Red Hat Enterprise Linux 8 STIG V1R2

RHEL 8 must be a vendor-supported release.

STIG ID: RHEL-08-010000 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

An operating system release is considered "supported" if the vendor continues to provide security patches for the product. With an unsupported release, it will not be possible to resolve security issues discovered in the system software.

Red Hat offers the Extended Update Support (EUS) ad-on to a Red Hat Enterprise Linux subscription, for a fee, for those customers who wish to standardize on a specific minor release for an extended period. The RHEL 8 minor releases eligible for EUS are 8.1, 8.2, 8.4, 8.6, and 8.8. Each RHEL 8 EUS stream is available for 24 months from the availability of the minor release. For more details on the Red Hat Enterprise Linux Life Cycle visit https://access.redhat.com/support/policy/updates/errata.

Check

Verify the version of the operating system is vendor supported.

Check the version of the operating system with the following command:

$ sudo cat /etc/redhat-release

Red Hat Enterprise Linux Server release 8.1 (Ootpa)

Current End of Maintenance Support for RHEL 8.1 is 30 April 2020.

Current End of Maintenance Support for RHEL 8.2 is 30 November 2020.

Current End of Maintenance Support for RHEL 8.3 is 30 April 2021.

Current End of Maintenance Support for RHEL 8.4 is 30 November 2021.

Current End of Maintenance Support for RHEL 8.5 is 30 April 2022.

Current End of Maintenance Support for RHEL 8.6 is 30 November 2022.

Current End of Maintenance Support for RHEL 8.7 is 30 April 2023.

Current End of Maintenance Support for RHEL 8.8 is 30 November 2023.

If the release is not supported by the vendor, this is a finding.

Fix

Upgrade to a supported version of RHEL 8.

RHEL 8 vendor packaged system security patches and updates must be installed and up to date.

STIG ID: RHEL-08-010010 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Timely patching is critical for maintaining the operational availability, confidentiality, and integrity of information technology (IT) systems. However, failure to keep operating system and application software patched is a common mistake made by IT professionals. New patches are released daily, and it is often difficult for even experienced System Administrators to keep abreast of all the new patches. When new weaknesses in an operating system exist, patches are usually made available by the vendor to resolve the problems. If the most recent security patches and updates are not installed, unauthorized users may take advantage of weaknesses in the unpatched software. The lack of prompt attention to patching could result in a system compromise.

Check

Verify the operating system security patches and updates are installed and up to date. Updates are required to be applied with a frequency determined by the site or Program Management Office (PMO).

Obtain the list of available package security updates from Red Hat. The URL for updates is https://rhn.redhat.com/errata/. It is important to note that updates provided by Red Hat may not be present on the system if the underlying packages are not installed.

Check that the available package security updates have been installed on the system with the following command:

$ sudo yum history list | more

Loaded plugins: langpacks, product-id, subscription-manager
ID | Command line | Date and time | Action(s) | Altered
-------------------------------------------------------------------------------
70 | install aide | 2020-03-05 10:58 | Install | 1
69 | update -y | 2020-03-04 14:34 | Update | 18 EE
68 | install vlc | 2020-02-21 17:12 | Install | 21
67 | update -y | 2020-02-21 17:04 | Update | 7 EE

If package updates have not been performed on the system within the timeframe the site/program documentation requires, this is a finding.

Typical update frequency may be overridden by Information Assurance Vulnerability Alert (IAVA) notifications from CYBERCOM.

If the operating system is in non-compliance with the Information Assurance Vulnerability Management (IAVM) process, this is a finding.

Fix

Install the operating system patches or updated packages available from Red Hat within 30 days or sooner as local policy dictates.

RHEL 8 must implement NIST FIPS-validated cryptography for the following: to provision digital signatures, to generate cryptographic hashes, and to protect data requiring data-at-rest protections in accordance with applicable federal laws, Executive Orders, directives, policies, regulations, and standards.

STIG ID: RHEL-08-010020 | SRG: SRG-OS-000033-GPOS-00014 | Severity: high | CCI: CCI-000068

Vulnerability Discussion

Use of weak or untested encryption algorithms undermines the purposes of using encryption to protect data. The operating system must implement cryptographic modules adhering to the higher standards approved by the Federal Government since this provides assurance they have been tested and validated.

RHEL 8 utilizes GRUB 2 as the default bootloader. Note that GRUB 2 command-line parameters are defined in the "kernelopts" variable of the /boot/grub2/grubenv file for all kernel boot entries. The command "fips-mode-setup" modifies the "kernelopts" variable, which in turn updates all kernel boot entries.

The fips=1 kernel option needs to be added to the kernel command line during system installation so that key generation is done with FIPS-approved algorithms and continuous monitoring tests in place. Users must also ensure the system has plenty of entropy during the installation process by moving the mouse around, or if no mouse is available, ensuring that many keystrokes are typed. The recommended amount of keystrokes is 256 and more. Less than 256 keystrokes may generate a non-unique key.

Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000125-GPOS-00065, SRG-OS-000396-GPOS-00176, SRG-OS-000423-GPOS-00187, SRG-OS-000478-GPOS-00223

Check

Verify the operating system implements DoD-approved encryption to protect the confidentiality of remote access sessions.

Check to see if FIPS mode is enabled with the following command:

$ sudo fipscheck

usage: fipscheck [-s ]

fips mode is on

If FIPS mode is "on", check to see if the kernel boot parameter is configured for FIPS mode with the following command:

$ sudo grub2-editenv - list | grep fips

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If the kernel boot parameter is configured to use FIPS mode, check to see if the system is in FIPS mode with the following command:

$ sudo cat /proc/sys/crypto/fips_enabled

1

If FIPS mode is not "on", the kernel boot parameter is not configured for FIPS mode, or the system does not have a value of "1" for "fips_enabled" in "/proc/sys/crypto", this is a finding.

Fix

Configure the operating system to implement DoD-approved encryption by following the steps below:

To enable strict FIPS compliance, the fips=1 kernel option needs to be added to the kernel boot parameters during system installation so key generation is done with FIPS-approved algorithms and continuous monitoring tests in place.

Enable FIPS mode after installation (not strict FIPS compliant) with the following command:

$ sudo fips-mode-setup --enable

Reboot the system for the changes to take effect.

All RHEL 8 local disk partitions must implement cryptographic mechanisms to prevent unauthorized disclosure or modification of all information that requires at rest protection.

STIG ID: RHEL-08-010030 | SRG: SRG-OS-000185-GPOS-00079 | Severity: medium | CCI: CCI-001199

Vulnerability Discussion

RHEL 8 systems handling data requiring "data at rest" protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest.

Selection of a cryptographic mechanism is based on the need to protect the integrity of organizational information. The strength of the mechanism is commensurate with the security category and/or classification of the information. Organizations have the flexibility to either encrypt all information on storage devices (i.e., full disk encryption) or encrypt specific data structures (e.g., files, records, or fields).

Satisfies: SRG-OS-000185-GPOS-00079, SRG-OS-000404-GPOS-00183, SRG-OS-000405-GPOS-00184

Check

Verify RHEL 8 prevents unauthorized disclosure or modification of all information requiring at-rest protection by using disk encryption.

If there is a documented and approved reason for not having data-at-rest encryption, this requirement is Not Applicable.

Verify all system partitions are encrypted with the following command:

$ sudo blkid

/dev/mapper/rhel-root: UUID="67b7d7fe-de60-6fd0-befb-e6748cf97743" TYPE="crypto_LUKS"

Every persistent disk partition present must be of type "crypto_LUKS". If any partitions other than pseudo file systems (such as /proc or /sys) are not type "crypto_LUKS", ask the administrator to indicate how the partitions are encrypted. If there is no evidence that all local disk partitions are encrypted, this is a finding.

Fix

Configure RHEL 8 to prevent unauthorized modification of all information at rest by using disk encryption.

Encrypting a partition in an already installed system is more difficult, because existing partitions will need to be resized and changed. To encrypt an entire partition, dedicate a partition for encryption in the partition layout.

RHEL 8 must display the Standard Mandatory DoD Notice and Consent Banner before granting local or remote access to the system via a ssh logon.

STIG ID: RHEL-08-010040 | SRG: SRG-OS-000023-GPOS-00006 | Severity: medium | CCI: CCI-000048

Vulnerability Discussion

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.

System use notifications are required only for access via logon interfaces with human users and are not required when such human interfaces do not exist.

The banner must be formatted in accordance with applicable DoD policy. Use the following verbiage for operating systems that can accommodate banners of 1300 characters:

"You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.

By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details."

Use the following verbiage for operating systems that have severe limitations on the number of characters that can be displayed in the banner:

"I've read & consent to terms in IS user agreem't."

Satisfies: SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088

Check

Verify any publicly accessible connection to the operating system displays the Standard Mandatory DoD Notice and Consent Banner before granting access to the system.

Check for the location of the banner file being used with the following command:

$ sudo grep -i banner /etc/ssh/sshd_config

banner /etc/issue

This command will return the banner keyword and the name of the file that contains the ssh banner (in this case "/etc/issue").

If the line is commented out, this is a finding.

View the file specified by the banner keyword to check that it matches the text of the Standard Mandatory DoD Notice and Consent Banner:

"You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details."

If the system does not display a graphical logon banner or the banner does not match the Standard Mandatory DoD Notice and Consent Banner, this is a finding.

If the text in the file does not match the Standard Mandatory DoD Notice and Consent Banner, this is a finding.

Fix

Configure the operating system to display the Standard Mandatory DoD Notice and Consent Banner before granting access to the system via the ssh.

Edit the "/etc/ssh/sshd_config" file to uncomment the banner keyword and configure it to point to a file that will contain the logon banner (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor). An example configuration line is:

banner /etc/issue

Either create the file containing the banner or replace the text in the file with the Standard Mandatory DoD Notice and Consent Banner. The DoD-required text is:

"You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details."

The SSH service must be restarted for changes to take effect.

RHEL 8 must display the Standard Mandatory DoD Notice and Consent Banner before granting local or remote access to the system via a graphical user logon.

STIG ID: RHEL-08-010050 | SRG: SRG-OS-000023-GPOS-00006 | Severity: medium | CCI: CCI-000048

Vulnerability Discussion

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.

System use notifications are required only for access via logon interfaces with human users and are not required when such human interfaces do not exist.

The banner must be formatted in accordance with applicable DoD policy. Use the following verbiage for operating systems that can accommodate banners of 1300 characters:

"You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.

By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details."

Satisfies: SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088

Check

Verify RHEL 8 displays the Standard Mandatory DoD Notice and Consent Banner before granting access to the operating system via a graphical user logon.

Note: This requirement assumes the use of the RHEL 8 default graphical user interface, Gnome Shell. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

Check to see if the operating system displays a banner at the logon screen with the following command:

$ sudo grep banner-message-enable /etc/dconf/db/local.d/*

banner-message-enable=true

If "banner-message-enable" is set to "false" or is missing, this is a finding.

Check that the operating system displays the exact Standard Mandatory DoD Notice and Consent Banner text with the command:

$ sudo grep banner-message-text /etc/dconf/db/local.d/*

banner-message-text=
'You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.\nBy using this IS (which includes any device attached to this IS), you consent to the following conditions:\n-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.\n-At any time, the USG may inspect and seize data stored on this IS.\n-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.\n-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.\n-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details. '

Note: The "\n " characters are for formatting only. They will not be displayed on the graphical interface.

If the banner does not match the Standard Mandatory DoD Notice and Consent Banner exactly, this is a finding.

Fix

Configure the operating system to display the Standard Mandatory DoD Notice and Consent Banner before granting access to the system.

Note: If the system does not have a graphical user interface installed, this requirement is Not Applicable.

Create a database to contain the system-wide graphical user logon settings (if it does not already exist) with the following command:

$ sudo touch /etc/dconf/db/local.d/01-banner-message

Add the following lines to the [org/gnome/login-screen] section of the "/etc/dconf/db/local.d/01-banner-message":

[org/gnome/login-screen]

banner-message-enable=true

banner-message-text='You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.\nBy using this IS (which includes any device attached to this IS), you consent to the following conditions:\n-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.\n-At any time, the USG may inspect and seize data stored on this IS.\n-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.\n-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.\n-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details. '

Note: The "\n " characters are for formatting only. They will not be displayed on the graphical interface.

Run the following command to update the database:

$ sudo dconf update

RHEL 8 must display the Standard Mandatory DoD Notice and Consent Banner before granting local or remote access to the system via a command line user logon.

STIG ID: RHEL-08-010060 | SRG: SRG-OS-000023-GPOS-00006 | Severity: medium | CCI: CCI-000048

Vulnerability Discussion

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.

System use notifications are required only for access via logon interfaces with human users and are not required when such human interfaces do not exist.

The banner must be formatted in accordance with applicable DoD policy. Use the following verbiage for operating systems that can accommodate banners of 1300 characters:

"You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.

By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details."

Satisfies: SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088

Check

Verify RHEL 8 displays the Standard Mandatory DoD Notice and Consent Banner before granting access to the operating system via a command line user logon.

Check that RHEL 8 displays a banner at the command line login screen with the following command:

$ sudo cat /etc/issue

If the banner is set correctly it will return the following text:

“You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.

By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.”

If the banner text does not match the Standard Mandatory DoD Notice and Consent Banner exactly, this is a finding.

Fix

Configure RHEL 8 to display the Standard Mandatory DoD Notice and Consent Banner before granting access to the system via command line logon.

Edit the "/etc/issue" file to replace the default text with the Standard Mandatory DoD Notice and Consent Banner. The DoD-required text is:

"You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.

By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests -- not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details."

All RHEL 8 remote access methods must be monitored.

STIG ID: RHEL-08-010070 | SRG: SRG-OS-000032-GPOS-00013 | Severity: medium | CCI: CCI-000067

Vulnerability Discussion

Remote access services, such as those providing remote access to network devices and information systems, which lack automated monitoring capabilities, increase risk and make remote user access management difficult at best.

Remote access is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Automated monitoring of remote access sessions allows organizations to detect cyber attacks and ensure ongoing compliance with remote access policies by auditing connection activities of remote access capabilities, such as Remote Desktop Protocol (RDP), on a variety of information system components (e.g., servers, workstations, notebook computers, smartphones, and tablets).

Check

Verify that RHEL 8 monitors all remote access methods.

Check that remote access methods are being logged by running the following command:

$ sudo grep -E '(auth.*|authpriv.*|daemon.*)' /etc/rsyslog.conf

auth.*;authpriv.*;daemon.* /var/log/secure

If "auth.*", "authpriv.*" or "daemon.*" are not configured to be logged, this is a finding.

Fix

Configure RHEL 8 to monitor all remote access methods by installing rsyslog with the following command:

$ sudo yum install rsyslog

Then add or update the following lines to the "/etc/rsyslog.conf" file:

auth.*;authpriv.*;daemon.* /var/log/secure

The "rsyslog" service must be restarted for the changes to take effect. To restart the "rsyslog" service, run the following command:

$ sudo systemctl restart rsyslog.service

RHEL 8, for PKI-based authentication, must validate certificates by constructing a certification path (which includes status information) to an accepted trust anchor.

STIG ID: RHEL-08-010090 | SRG: SRG-OS-000066-GPOS-00034 | Severity: medium | CCI: CCI-000185

Vulnerability Discussion

Without path validation, an informed trust decision by the relying party cannot be made when presented with any certificate not already explicitly trusted.

A trust anchor is an authoritative entity represented via a public key and associated data. It is used in the context of public key infrastructures, X.509 digital certificates, and DNSSEC.

When there is a chain of trust, usually the top entity to be trusted becomes the trust anchor; it can be, for example, a Certification Authority (CA). A certification path starts with the subject certificate and proceeds through a number of intermediate certificates up to a trusted root certificate, typically issued by a trusted CA.

This requirement verifies that a certification path to an accepted trust anchor is used for certificate validation and that the path includes status information. Path validation is necessary for a relying party to make an informed trust decision when presented with any certificate not already explicitly trusted. Status information for certification paths includes certificate revocation lists or online certificate status protocol responses. Validation of the certificate status information is out of scope for this requirement.

Satisfies: SRG-OS-000066-GPOS-00034, SRG-OS-000384-GPOS-00167

Check

Verify RHEL 8 for PKI-based authentication has valid certificates by constructing a certification path (which includes status information) to an accepted trust anchor.

Check that the system has a valid DoD root CA installed with the following command:

$ sudo openssl x509 -text -in /etc/sssd/pki/sssd_auth_ca_db.pem

Certificate:
Data:
Version: 3 (0x2)
Serial Number: 1 (0x1)
Signature Algorithm: sha256WithRSAEncryption
Issuer: C = US, O = U.S. Government, OU = DoD, OU = PKI, CN = DoD Root CA 3
Validity
Not Before: Mar 20 18:46:41 2012 GMT
Not After : Dec 30 18:46:41 2029 GMT
Subject: C = US, O = U.S. Government, OU = DoD, OU = PKI, CN = DoD Root CA 3
Subject Public Key Info:
Public Key Algorithm: rsaEncryption

If the root ca file is not a DoD-issued certificate with a valid date and installed in the /etc/sssd/pki/sssd_auth_ca_db.pem location, this is a finding.

Fix

Configure RHEL 8, for PKI-based authentication, to validate certificates by constructing a certification path (which includes status information) to an accepted trust anchor.

Obtain a valid copy of the DoD root CA file from the PKI CA certificate bundle from cyber.mil and copy the DoD_PKE_CA_chain.pem into the following file:

/etc/sssd/pki/sssd_auth_ca_db.pem

RHEL 8, for certificate-based authentication, must enforce authorized access to the corresponding private key.

STIG ID: RHEL-08-010100 | SRG: SRG-OS-000067-GPOS-00035 | Severity: medium | CCI: CCI-000186

Vulnerability Discussion

If an unauthorized user obtains access to a private key without a passcode, that user would have unauthorized access to any system where the associated public key has been installed.

Check

Verify the SSH private key files have a passcode.

For each private key stored on the system, use the following command:

$ sudo ssh-keygen -y -f /path/to/file

If the contents of the key are displayed, this is a finding.

Fix

Create a new private and public key pair that utilizes a passcode with the following command:

$ sudo ssh-keygen -n [passphrase]

RHEL 8 must encrypt all stored passwords with a FIPS 140-2 approved cryptographic hashing algorithm.

STIG ID: RHEL-08-010110 | SRG: SRG-OS-000073-GPOS-00041 | Severity: medium | CCI: CCI-000196

Vulnerability Discussion

Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised.

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and DoD data may be compromised.

FIPS 140-2 is the current standard for validating that mechanisms used to access cryptographic modules utilize authentication that meets DoD requirements.

Check

Verify that the shadow password suite configuration is set to encrypt password with a FIPS 140-2 approved cryptographic hashing algorithm.

Check the hashing algorithm that is being used to hash passwords with the following command:

$ sudo grep -i crypt /etc/login.defs

ENCRYPT_METHOD SHA512

If "ENCRYPT_METHOD" does not equal SHA512 or greater, this is a finding.

Fix

Configure RHEL 8 to encrypt all stored passwords.

Edit/Modify the following line in the "/etc/login.defs" file and set "[ENCRYPT_METHOD]" to SHA512.

ENCRYPT_METHOD SHA512

RHEL 8 must employ FIPS 140-2 approved cryptographic hashing algorithms for all stored passwords.

STIG ID: RHEL-08-010120 | SRG: SRG-OS-000073-GPOS-00041 | Severity: medium | CCI: CCI-000196

Vulnerability Discussion

The system must use a strong hashing algorithm to store the password.

Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised.

Check

Confirm that the interactive user account passwords are using a strong password hash with the following command:

$ sudo cut -d: -f2 /etc/shadow

$6$kcOnRq/5$NUEYPuyL.wghQwWssXRcLRFiiru7f5JPV6GaJhNC2aK5F3PZpE/BCCtwrxRc/AInKMNX3CdMw11m9STiql12f/

Password hashes "!" or "*" indicate inactive accounts not available for logon and are not evaluated. If any interactive user password hash does not begin with "$6$", this is a finding.

Fix

Lock all interactive user accounts not using SHA-512 hashing until the passwords can be regenerated with SHA-512.

RHEL 8 must employ FIPS 140-2 approved cryptographic hashing algorithms for all created passwords.

STIG ID: RHEL-08-010130 | SRG: SRG-OS-000073-GPOS-00041 | Severity: medium | CCI: CCI-000196

Vulnerability Discussion

The system must use a strong hashing algorithm to store the password. The system must use a sufficient number of hashing rounds to ensure the required level of entropy.

Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised.

Check

Check that a minimum number of hash rounds is configured by running the following commands:

$ sudo grep rounds /etc/pam.d/password-auth

password sufficient pam_unix.so sha512 rounds=5000

$ sudo grep rounds /etc/pam.d/system-auth

password sufficient pam_unix.so sha512 rounds=5000

If "rounds" has a value below "5000", or is commented out in either file, this is a finding.

Fix

Configure RHEL 8 to encrypt all stored passwords with a strong cryptographic hash.

Edit/modify the following line in the "/etc/pam.d/password-auth" and "etc/pam.d/system-auth" files and set "rounds" to a value no lower than "5000":

password sufficient pam_unix.so sha512 rounds=5000

RHEL 8 operating systems booted with United Extensible Firmware Interface (UEFI) implemented must require authentication upon booting into single-user mode and maintenance.

STIG ID: RHEL-08-010140 | SRG: SRG-OS-000080-GPOS-00048 | Severity: high | CCI: CCI-000213

Vulnerability Discussion

If the system does not require valid authentication before it boots into single-user or maintenance mode, anyone who invokes single-user or maintenance mode is granted privileged access to all files on the system. GRUB 2 is the default boot loader for RHEL 8 and is designed to require a password to boot into single-user mode or make modifications to the boot menu.

Check

For systems that use BIOS, this is Not Applicable.

Check to see if an encrypted root password is set. On systems that use UEFI, use the following command:

$ sudo grep -iw grub2_password /boot/efi/EFI/redhat/user.cfg

GRUB2_PASSWORD=grub.pbkdf2.sha512.[password_hash]

If the root password does not begin with "grub.pbkdf2.sha512", this is a finding.

Verify that a unique account name is set as the "superusers":

$ sudo grep -iw "superusers" /boot/efi/EFI/redhat/grub.cfg
set superusers="[someuniquestringhere]"
export superusers

If "superusers" is not set to a unique name or is missing a name, this is a finding.

Fix

Configure the system to require a grub bootloader password for the grub superuser account.

Generate an encrypted grub2 password for the grub superuser account with the following command:

$ sudo grub2-setpassword
Enter password:
Confirm password:

Edit the /boot/efi/EFI/redhat/grub.cfg file and add or modify the following lines in the "### BEGIN /etc/grub.d/01_users ###" section:

set superusers="[someuniquestringhere]"
export superusers

RHEL 8 operating systems booted with a BIOS must require authentication upon booting into single-user and maintenance modes.

STIG ID: RHEL-08-010150 | SRG: SRG-OS-000080-GPOS-00048 | Severity: high | CCI: CCI-000213

Vulnerability Discussion

Check

For systems that use UEFI, this is Not Applicable.

Check to see if an encrypted root password is set. On systems that use a BIOS, use the following command:

$ sudo grep -iw grub2_password /boot/grub2/user.cfg

GRUB2_PASSWORD=grub.pbkdf2.sha512.[password_hash]

If the root password does not begin with "grub.pbkdf2.sha512", this is a finding.

Verify that a unique name is set as the "superusers":

$ sudo grep -iw "superusers" /boot/grub2/grub.cfg
set superusers="[someuniquestringhere]"
export superusers

If "superusers" is not set to a unique name or is missing a name, this is a finding.

Fix

Configure the system to require a grub bootloader password for the grub superuser account.

Generate an encrypted grub2 password for the grub superuser account with the following command:

$ sudo grub2-setpassword
Enter password:
Confirm password:

Edit the /boot/grub2/grub.cfg file and add or modify the following lines in the "### BEGIN /etc/grub.d/01_users ###" section:

set superusers="[someuniquestringhere]"
export superusers

RHEL 8 operating systems must require authentication upon booting into emergency or rescue modes.

STIG ID: RHEL-08-010151 | SRG: SRG-OS-000080-GPOS-00048 | Severity: medium | CCI: CCI-000213

Vulnerability Discussion

If the system does not require valid root authentication before it boots into emergency or rescue mode, anyone who invokes emergency or rescue mode is granted privileged access to all files on the system.

Check

Check to see if the system requires authentication for rescue or emergency mode with the following command:

$ sudo grep sulogin-shell /usr/lib/systemd/system/rescue.service

ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue

If the "ExecStart" line is configured for anything other than "/usr/lib/systemd/systemd-sulogin-shell rescue", commented out, or missing, this is a finding.

Fix

Configure the system to require authentication upon booting into emergency or rescue mode by adding the following line to the "/usr/lib/systemd/system/rescue.service" file.

ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue

The RHEL 8 pam_unix.so module must use a FIPS 140-2 approved cryptographic hashing algorithm for system authentication.

STIG ID: RHEL-08-010160 | SRG: SRG-OS-000120-GPOS-00061 | Severity: medium | CCI: CCI-000803

Vulnerability Discussion

Check

Verify that pam_unix.so auth is configured to use sha512.

Check that pam_unix.so auth is configured to use sha512 in both /etc/pam.d/password-auth and /etc/pam.d/system-auth with the following command:

$ sudo grep password /etc/pam.d/password-auth | grep pam_unix

password sufficient pam_unix.so sha512 rounds=5000

$ sudo grep password /etc/pam.d/system-auth | grep pam_unix

password sufficient pam_unix.so sha512 rounds=5000

If "sha512" is not an option in both outputs, or is commented out, this is a finding.

Fix

Configure RHEL 8 to use a FIPS 140-2 approved cryptographic hashing algorithm for system authentication.

Edit/modify the following line in the file "/etc/pam.d/password-auth" and "/etc/pam.d/system-auth" files to include the sha512 option for pam_unix.so:

password sufficient pam_unix.so sha512 rounds=5000 shadow remember=5

RHEL 8 must prevent system daemons from using Kerberos for authentication.

STIG ID: RHEL-08-010161 | SRG: SRG-OS-000120-GPOS-00061 | Severity: medium | CCI: CCI-000803

Vulnerability Discussion

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and DoD data may be compromised.

RHEL 8 systems utilizing encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.

The key derivation function (KDF) in Kerberos is not FIPS compatible. Ensuring the system does not have any keytab files present prevents system daemons from using Kerberos for authentication. A keytab is a file containing pairs of Kerberos principals and encrypted keys.

FIPS 140-2 is the current standard for validating that mechanisms used to access cryptographic modules utilize authentication that meets DoD requirements. This allows for Security Levels 1, 2, 3, or 4 for use on a general-purpose computing system.

Check

Verify that RHEL 8 prevents system daemons from using Kerberos for authentication.

If the system is a server utilizing krb5-server-1.17-18.el8.x86_64 or newer, this requirement is not applicable.
If the system is a workstation utilizing krb5-workstation-1.17-18.el8.x86_64 or newer, this requirement is not applicable.

Check if there are available keytabs with the following command:

$ sudo ls -al /etc/*.keytab

If this command produces any file(s), this is a finding.

Fix

Configure RHEL 8 to prevent system daemons from using Kerberos for authentication.

Remove any files with the .keytab extension from the operating system.

The krb5-workstation package must not be installed on RHEL 8.

STIG ID: RHEL-08-010162 | SRG: SRG-OS-000120-GPOS-00061 | Severity: medium | CCI: CCI-000803

Vulnerability Discussion

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and DoD data may be compromised.

RHEL 8 systems utilizing encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.

Currently, Kerberos does not utilize FIPS 140-2 cryptography.

FIPS 140-2 is the current standard for validating that mechanisms used to access cryptographic modules utilize authentication that meets DoD requirements. This allows for Security Levels 1, 2, 3, or 4 for use on a general-purpose computing system.

Check

Verify the krb5-workstation package has not been installed on the system with the following commands:

If the system is a server or is utilizing krb5-workstation-1.17-18.el8.x86_64 or newer, this is Not Applicable.

$ sudo yum list installed krb5-workstation

krb5-workstation.x86_64 1.17-9.el8 repository

If the krb5-workstation package is installed and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Document the krb5-workstation package with the ISSO as an operational requirement or remove it from the system with the following command:

$ sudo yum remove krb5-workstation

The krb5-server package must not be installed on RHEL 8.

STIG ID: RHEL-08-010163 | SRG: SRG-OS-000120-GPOS-00061 | Severity: medium | CCI: CCI-000803

Vulnerability Discussion

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and DoD data may be compromised.

RHEL 8 systems utilizing encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.

Currently, Kerberos does not utilize FIPS 140-2 cryptography.

FIPS 140-2 is the current standard for validating that mechanisms used to access cryptographic modules utilize authentication that meets DoD requirements. This allows for Security Levels 1, 2, 3, or 4 for use on a general-purpose computing system.

Check

Verify the krb5-server package has not been installed on the system with the following commands:

If the system is a workstation or is utilizing krb5-server-1.17-18.el8.x86_64 or newer, this is Not Applicable

$ sudo yum list installed krb5-server

krb5-server.x86_64 1.17-9.el8 repository

If the krb5-server package is installed and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Document the krb5-server package with the ISSO as an operational requirement or remove it from the system with the following command:

$ sudo yum remove krb5-server

RHEL 8 must use a Linux Security Module configured to enforce limits on system services.

STIG ID: RHEL-08-010170 | SRG: SRG-OS-000134-GPOS-00068 | Severity: medium | CCI: CCI-001084

Vulnerability Discussion

Without verification of the security functions, security functions may not operate correctly and the failure may go unnoticed. Security function is defined as the hardware, software, and/or firmware of the information system responsible for enforcing the system security policy and supporting the isolation of code and data on which the protection is based. Security functionality includes, but is not limited to, establishing system accounts, configuring access authorizations (i.e., permissions, privileges), setting events to be audited, and setting intrusion detection parameters.

This requirement applies to operating systems performing security function verification/testing and/or systems and environments that require this functionality.

Check

Verify the operating system verifies correct operation of all security functions.

Check if "SELinux" is active and in "Enforcing" mode with the following command:

$ sudo getenforce
Enforcing

If "SELinux" is not active and not in "Enforcing" mode, this is a finding.

Fix

Configure the operating system to verify correct operation of all security functions.

Set the "SELinux" status and the "Enforcing" mode by modifying the "/etc/selinux/config" file to have the following line:

SELINUX=enforcing

A reboot is required for the changes to take effect.

RHEL 8 must have policycoreutils package installed.

STIG ID: RHEL-08-010171 | SRG: SRG-OS-000134-GPOS-00068 | Severity: low | CCI: CCI-001084

Vulnerability Discussion

Without verification of the security functions, security functions may not operate correctly and the failure may go unnoticed. Security function is defined as the hardware, software, and/or firmware of the information system responsible for enforcing the system security policy and supporting the isolation of code and data on which the protection is based. Security functionality includes, but is not limited to, establishing system accounts, configuring access authorizations (i.e., permissions, privileges), setting events to be audited, and setting intrusion detection parameters.

Policycoreutils contains the policy core utilities that are required for basic operation of an SELinux-enabled system. These utilities include load_policy to load SELinux policies, setfile to label filesystems, newrole to switch roles, and run_init to run /etc/init.d scripts in the proper context.

Check

Verify the operating system has the policycoreutils package installed with the following command:

$ sudo yum list installed policycoreutils

policycoreutils.x86_64 2.9-3.el8 @anaconda

If the policycoreutils package is not installed, this is a finding.

Fix

Configure the operating system to have the policycoreutils package installed with the following command:

$ sudo yum install policycoreutils

All RHEL 8 public directories must be owned by root or a system account to prevent unauthorized and unintended information transferred via shared system resources.

STIG ID: RHEL-08-010180 | SRG: SRG-OS-000138-GPOS-00069 | Severity: medium | CCI: CCI-001090

Vulnerability Discussion

Preventing unauthorized information transfers mitigates the risk of information, including encrypted representations of information, produced by the actions of prior users/roles (or the actions of processes acting on behalf of prior users/roles) from being available to any current users/roles (or current processes) that obtain access to shared system resources (e.g., registers, main memory, hard disks) after those resources have been released back to information systems. The control of information in shared resources is also commonly referred to as object reuse and residual information protection.

This requirement generally applies to the design of an information technology product, but it can also apply to the configuration of particular information system components that are, or use, such products. This can be verified by acceptance/validation processes in DoD or other government agencies.

There may be shared resources with configurable protections (e.g., files in storage) that may be assessed on specific information system components.

Check

Check to see that all public directories are owned by root or a system account with the following command:

$ sudo find / -type d -perm -0002 -exec ls -lLd {} \;

drwxrwxrwxt 7 root root 4096 Jul 26 11:19 /tmp

If any of the returned directories are not owned by root or a system account, this is a finding.

Fix

Configure all public directories to be owned by root or a system account to prevent unauthorized and unintended information transferred via shared system resources.

Set the owner of all public directories as root or a system account using the command, replace "[Public Directory]" with any directory path not owned by root or a system account:

$ sudo chown root [Public Directory]

A sticky bit must be set on all RHEL 8 public directories to prevent unauthorized and unintended information transferred via shared system resources.

STIG ID: RHEL-08-010190 | SRG: SRG-OS-000138-GPOS-00069 | Severity: medium | CCI: CCI-001090

Vulnerability Discussion

Check

Verify that all world-writable directories have the sticky bit set.

Check to see that all world-writable directories have the sticky bit set by running the following command:

$ sudo find / -type d $ -perm -0002 -a ! -perm -1000 $ -print 2>/dev/null

drwxrwxrwxt 7 root root 4096 Jul 26 11:19 /tmp

If any of the returned directories are world-writable and do not have the sticky bit set, this is a finding.

Fix

Configure all world-writable directories to have the sticky bit set to prevent unauthorized and unintended information transferred via shared system resources.

Set the sticky bit on all world-writable directories using the command, replace "[World-Writable Directory]" with any directory path missing the sticky bit:

$ sudo chmod 1777 [World-Writable Directory]

RHEL 8 must be configured so that all network connections associated with SSH traffic are terminated at the end of the session or after 10 minutes of inactivity, except to fulfill documented and validated mission requirements.

STIG ID: RHEL-08-010200 | SRG: SRG-OS-000163-GPOS-00072 | Severity: medium | CCI: CCI-001133

Vulnerability Discussion

Terminating an idle SSH session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle SSH session will also free up resources committed by the managed network element.

Terminating network connections associated with communications sessions includes, for example, de-allocating associated TCP/IP address/port pairs at the operating system level and de-allocating networking assignments at the application level if multiple application sessions are using a single operating system-level network connection. This does not mean that the operating system terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

RHEL 8 utilizes /etc/ssh/sshd_config for configurations of OpenSSH. Within the sshd_config the product of the values of "ClientAliveInterval" and "ClientAliveCountMax" are used to establish the inactivity threshold. The "ClientAliveInterval" is a timeout interval in seconds after which if no data has been received from the client, sshd will send a message through the encrypted channel to request a response from the client. The "ClientAliveCountMax" is the number of client alive messages that may be sent without sshd receiving any messages back from the client. If this threshold is met, sshd will disconnect the client. The default setting for "ClientAliveCountMax" is "3". If "ClientAliveInterval is set to "15" and "ClientAliveCountMax" is left at the default, unresponsive SSH clients will be disconnected after approximately 45 seconds.

Satisfies: SRG-OS-000163-GPOS-00072, SRG-OS-000126-GPOS-00066, SRG-OS-000279-GPOS-00109

Check

Verify all network connections associated with SSH traffic are automatically terminated at the end of the session or after 10 minutes of inactivity.

Check that the "ClientAliveInterval" variable is set to a value of "600" or less and that the "ClientAliveCountMax" is set to "0" by performing the following command:

$ sudo grep -i clientalive /etc/ssh/sshd_config

ClientAliveInterval 600
ClientAliveCountMax 0

If "ClientAliveInterval" and "ClientAliveCountMax" do not exist, does not have a product value of "600" or less in "/etc/ssh/sshd_config", or is commented out, this is a finding.

Fix

Configure RHEL 8 to automatically terminate all network connections associated with SSH traffic at the end of a session or after 10 minutes of inactivity.

Modify or append the following lines in the "/etc/ssh/sshd_config" file to have a product value of "600" or less:

ClientAliveInterval 600
ClientAliveCountMax 0

In order for the changes to take effect, the SSH daemon must be restarted.

$ sudo systemctl restart sshd.service

The RHEL 8 /var/log/messages file must have mode 0640 or less permissive.

STIG ID: RHEL-08-010210 | SRG: SRG-OS-000206-GPOS-00084 | Severity: medium | CCI: CCI-001314

Vulnerability Discussion

Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can identify the RHEL 8 system or platform. Additionally, Personally Identifiable Information (PII) and operational information must not be revealed through error messages to unauthorized personnel or their designated representatives.

The structure and content of error messages must be carefully considered by the organization and development team. The extent to which the information system is able to identify and handle error conditions is guided by organizational policy and operational requirements.

Check

Verify that the "/var/log/messages" file has mode "0640" or less permissive with the following command:

$ sudo stat -c "%a %n" /var/log/messages

640 /var/log/messages

If a value of "0640" or less permissive is not returned, this is a finding.

Fix

Change the permissions of the file "/var/log/messages" to "0640" by running the following command:

$ sudo chmod 0640 /var/log/messages

The RHEL 8 /var/log/messages file must be owned by root.

STIG ID: RHEL-08-010220 | SRG: SRG-OS-000206-GPOS-00084 | Severity: medium | CCI: CCI-001314

Vulnerability Discussion

Check

Verify that the /var/log/messages file is owned by root with the following command:

$ sudo stat -c "%U" /var/log/messages

root

If "root" is not returned as a result, this is a finding.

Fix

Change the owner of the file /var/log/messages to root by running the following command:

$ sudo chown root /var/log/messages

The RHEL 8 /var/log/messages file must be group-owned by root.

STIG ID: RHEL-08-010230 | SRG: SRG-OS-000206-GPOS-00084 | Severity: medium | CCI: CCI-001314

Vulnerability Discussion

Check

Verify the "/var/log/messages" file is group-owned by root with the following command:

$ sudo stat -c "%G" /var/log/messages

root

If "root" is not returned as a result, this is a finding.

Fix

Change the group of the file "/var/log/messages" to "root" by running the following command:

$ sudo chgrp root /var/log/messages

The RHEL 8 /var/log directory must have mode 0755 or less permissive.

STIG ID: RHEL-08-010240 | SRG: SRG-OS-000206-GPOS-00084 | Severity: medium | CCI: CCI-001314

Vulnerability Discussion

Check

Verify that the "/var/log" directory has a mode of "0755" or less with the following command:

$ sudo stat -c "%a %n" /var/log

755

If a value of "0755" or less permissive is not returned, this is a finding.

Fix

Change the permissions of the directory "/var/log" to "0755" by running the following command:

$ sudo chmod 0755 /var/log

The RHEL 8 /var/log directory must be owned by root.

STIG ID: RHEL-08-010250 | SRG: SRG-OS-000206-GPOS-00084 | Severity: medium | CCI: CCI-001314

Vulnerability Discussion

Check

Verify the /var/log directory is owned by root with the following command:

$ sudo stat -c "%U" /var/log

root

If "root" is not returned as a result, this is a finding.

Fix

Change the owner of the directory /var/log to root by running the following command:

$ sudo chown root /var/log

The RHEL 8 /var/log directory must be group-owned by root.

STIG ID: RHEL-08-010260 | SRG: SRG-OS-000206-GPOS-00084 | Severity: medium | CCI: CCI-001314

Vulnerability Discussion

Check

Verify the "/var/log" directory is group-owned by root with the following command:

$ sudo stat -c "%G" /var/log

root

If "root" is not returned as a result, this is a finding.

Fix

Change the group of the directory "/var/log" to "root" by running the following command:

$ sudo chgrp root /var/log

The RHEL 8 SSH daemon must be configured to use only Message Authentication Codes (MACs) employing FIPS 140-2 validated cryptographic hash algorithms.

STIG ID: RHEL-08-010290 | SRG: SRG-OS-000250-GPOS-00093 | Severity: medium | CCI: CCI-001453

Vulnerability Discussion

Without cryptographic integrity protections, information can be altered by unauthorized users without detection.

Remote access (e.g., RDP) is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

RHEL 8 incorporates system-wide crypto policies by default. The SSH configuration file has no effect on the ciphers, MACs, or algorithms unless specifically defined in the /etc/sysconfig/sshd file. The employed algorithms can be viewed in the /etc/crypto-policies/back-ends/openssh.config file.

By specifying a hash algorithm list with the order of hashes being in a “strongest to weakest” orientation, the system will automatically attempt to use the strongest hash for securing SSH connections.

Satisfies: SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174, SRG-OS-000125-GPOS-00065

Check

Verify the SSH daemon is configured to use only MACs employing FIPS 140-2-approved algorithms:

Verify that system-wide crypto policies are in effect:

$ sudo grep -i crypto_policy /etc/sysconfig/sshd

# crypto_policy=

If the "crypto_policy" is uncommented, this is a finding.

Verify which system-wide crypto policy is in use:

$ sudo update-crypto-policies --show

FIPS

Check that the MACs in the back-end configurations are FIPS 140-2-approved algorithms with the following command:

$ sudo grep -i macs /etc/crypto-policies/back-ends/openssh.config /etc/crypto-policies/back-ends/opensshserver.config

/etc/crypto-policies/back-ends/openssh.config:MACs hmac-sha2-512,hmac-sha2-256
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr -oMACS=hmac-sha2-512,hmac-sha2-256'
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr -oMACS=hmac-sha2-512,hmac-sha2-256'

If the MAC entries in the "openssh.config" and "opensshserver.config" files have any hashes other than "hmac-sha2-512" and "hmac-sha2-256", the order differs from the example above, if they are missing, or commented out, this is a finding.

Fix

Configure the RHEL 8 SSH daemon to use only MACs employing FIPS 140-2-approved algorithms with the following commands:

$ sudo fips-mode-setup --enable

Next, update the "/etc/crypto-policies/back-ends/openssh.config"
and "/etc/crypto-policies/back-ends/opensshserver.config" files to include these MACs employing FIPS 140-2-approved algorithms:

/etc/crypto-policies/back-ends/openssh.config:MACs hmac-sha2-512,hmac-sha2-256
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr -oMACS=hmac-sha2-512,hmac-sha2-256'
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr -oMACS=hmac-sha2-512,hmac-sha2-256'

A reboot is required for the changes to take effect.

The RHEL 8 operating system must implement DoD-approved encryption to protect the confidentiality of SSH connections.

STIG ID: RHEL-08-010291 | SRG: SRG-OS-000250-GPOS-00093 | Severity: medium | CCI: CCI-001453

Vulnerability Discussion

Without cryptographic integrity protections, information can be altered by unauthorized users without detection.

Remote access (e.g., RDP) is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

RHEL 8 incorporates system-wide crypto policies by default. The SSH configuration file has no effect on the ciphers, MACs, or algorithms unless specifically defined in the /etc/sysconfig/sshd file. The employed algorithms can be viewed in the /etc/crypto-policies/back-ends/openssh.config file.

By specifying a cipher list with the order of ciphers being in a “strongest to weakest” orientation, the system will automatically attempt to use the strongest cipher for securing SSH connections.

Satisfies: SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174, SRG-OS-000125-GPOS-00065

Check

Verify the SSH daemon is configured to use only ciphers employing FIPS 140-2-approved algorithms:

Verify that system-wide crypto policies are in effect:

$ sudo grep -i crypto_policy /etc/sysconfig/sshd

# crypto_policy=

If the "crypto_policy" is uncommented, this is a finding.

Verify which system-wide crypto policy is in use:

$ sudo update-crypto-policies --show

FIPS

Check that the ciphers in the back-end configurations are FIPS 140-2-approved algorithms with the following command:

$ sudo grep -i ciphers /etc/crypto-policies/back-ends/openssh.config /etc/crypto-policies/back-ends/opensshserver.config

/etc/crypto-policies/back-ends/openssh.config:Ciphers aes256-ctr,aes192-ctr,aes128-ctr
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr'
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr'

If the cipher entries in the "openssh.config" and "opensshserver.config" files have any ciphers other than "aes256-ctr,aes192-ctr,aes128-ctr", the order differs from the example above, if they are missing, or commented out, this is a finding.

Fix

Configure the RHEL 8 SSH daemon to use only ciphers employing FIPS 140-2-approved algorithms with the following command:

$ sudo fips-mode-setup --enable

Next, update the "/etc/crypto-policies/back-ends/openssh.config" and "/etc/crypto-policies/back-ends/opensshserver.config" files to include these ciphers employing FIPS 140-2-approved algorithms:

/etc/crypto-policies/back-ends/openssh.config:Ciphers aes256-ctr,aes192-ctr,aes128-ctr
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr'
/etc/crypto-policies/back-ends/opensshserver.config:CRYPTO_POLICY='-oCiphers=aes256-ctr,aes192-ctr,aes128-ctr'

A reboot is required for the changes to take effect.

RHEL 8 must ensure the SSH server uses strong entropy.

STIG ID: RHEL-08-010292 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

The most important characteristic of a random number generator is its randomness, namely its ability to deliver random numbers that are impossible to predict. Entropy in computer security is associated with the unpredictability of a source of randomness. The random source with high entropy tends to achieve a uniform distribution of random values. Random number generators are one of the most important building blocks of cryptosystems.

The SSH implementation in RHEL8 uses the OPENSSL library, which does not use high-entropy sources by default. By using the SSH_USE_STRONG_RNG environment variable the OPENSSL random generator is reseeded from /dev/random. This setting is not recommended on computers without the hardware random generator because insufficient entropy causes the connection to be blocked until enough entropy is available.

Check

Verify the operating system SSH server uses strong entropy with the following command:

Note: If the operating system is RHEL versions 8.0 or 8.1, this requirement is not applicable.

$ sudo grep -i ssh_use_strong_rng /etc/sysconfig/sshd

SSH_USE_STRONG_RNG=32

If the "SSH_USE_STRONG_RNG" line does not equal "32", is commented out or missing, this is a finding.

Fix

Configure the operating system SSH server to use strong entropy.

Add or modify the following line in the "/etc/sysconfig/sshd" file.

SSH_USE_STRONG_RNG=32

The SSH service must be restarted for changes to take effect.

The RHEL 8 operating system must implement DoD-approved encryption in the OpenSSL package.

STIG ID: RHEL-08-010293 | SRG: SRG-OS-000250-GPOS-00093 | Severity: medium | CCI: CCI-001453

Vulnerability Discussion

Without cryptographic integrity protections, information can be altered by unauthorized users without detection.

Remote access (e.g., RDP) is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

RHEL 8 incorporates system-wide crypto policies by default. The employed algorithms can be viewed in the /etc/crypto-policies/back-ends/openssl.config file.

Satisfies: SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174, SRG-OS-000125-GPOS-00065

Check

Verify the OpenSSL library is configured to use only ciphers employing FIPS 140-2-approved algorithms:

Verify that system-wide crypto policies are in effect:

$ sudo grep -i opensslcnf.config /etc/pki/tls/openssl.cnf

.include /etc/crypto-policies/back-ends/opensslcnf.config

If the "opensslcnf.config" is not defined in the "/etc/pki/tls/openssl.cnf" file, this is a finding.

Verify which system-wide crypto policy is in use:

$ sudo update-crypto-policies --show

FIPS

If the system-wide crypto policy is set to anything other than "FIPS", this is a finding.

Fix

Configure the RHEL 8 OpenSSL library to use only ciphers employing FIPS 140-2-approved algorithms with the following command:

$ sudo fips-mode-setup --enable

A reboot is required for the changes to take effect.

The RHEL 8 operating system must implement DoD-approved TLS encryption in the OpenSSL package.

STIG ID: RHEL-08-010294 | SRG: SRG-OS-000250-GPOS-00093 | Severity: medium | CCI: CCI-001453

Vulnerability Discussion

Without cryptographic integrity protections, information can be altered by unauthorized users without detection.

Remote access (e.g., RDP) is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

RHEL 8 incorporates system-wide crypto policies by default. The employed algorithms can be viewed in the /etc/crypto-policies/back-ends/openssl.config file.

Satisfies: SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174, SRG-OS-000125-GPOS-00065

Check

Verify the OpenSSL library is configured to use only DoD-approved TLS encryption:

$ sudo grep -i MinProtocol /etc/crypto-policies/back-ends/opensslcnf.config

MinProtocol = TLSv1.2

If the "MinProtocol" is set to anything older than "TLSv1.2", this is a finding.

Fix

Configure the RHEL 8 OpenSSL library to use only DoD-approved TLS encryption by editing the following line in the "/etc/crypto-policies/back-ends/opensslcnf.config" file:

MinProtocol = TLSv1.2

A reboot is required for the changes to take effect.

The RHEL 8 operating system must implement DoD-approved TLS encryption in the GnuTLS package.

STIG ID: RHEL-08-010295 | SRG: SRG-OS-000250-GPOS-00093 | Severity: medium | CCI: CCI-001453

Vulnerability Discussion

Without cryptographic integrity protections, information can be altered by unauthorized users without detection.

Transport Layer Security (TLS) encryption is a required security setting as a number of known vulnerabilities have been reported against Secure Sockets Layer (SSL) and earlier versions of TLS. Encryption of private information is essential to ensuring data confidentiality. If private information is not encrypted, it can be intercepted and easily read by an unauthorized party. SQL Server must use a minimum of FIPS 140-2-approved TLS version 1.2, and all non-FIPS-approved SSL and TLS versions must be disabled. NIST SP 800-52 specifies the preferred configurations for government systems.

Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions using asymmetric cryptography enabling distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

The GnuTLS library offers an API to access secure communications protocols. SSLv2 is not available in the GnuTLS library. The RHEL 8 system-wide crypto policy defines employed algorithms in the /etc/crypto-policies/back-ends/gnutls.config file.

Satisfies: SRG-OS-000250-GPOS-00093, SRG-OS-000423-GPOS-00187

Check

Verify the GnuTLS library is configured to only allow DoD-approved SSL/TLS Versions:

$ sudo grep -io +vers.* /etc/crypto-policies/back-ends/gnutls.config

+VERS-ALL:-VERS-DTLS0.9:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:-VERS-DTLS1.0:+COMP-NULL:%PROFILE_MEDIUM

If the "gnutls.config" does not list "-VERS-DTLS0.9:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:VERS-DTLS1.0" to disable unapproved SSL/TLS versions, this is a finding.

Fix

Configure the RHEL 8 GnuTLS library to use only DoD-approved encryption by adding the following line to "/etc/crypto-policies/back-ends/gnutls.config":

+VERS-ALL:-VERS-DTLS0.9:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1:-VERS-DTLS1.0

A reboot is required for the changes to take effect.

RHEL 8 system commands must have mode 0755 or less permissive.

STIG ID: RHEL-08-010300 | SRG: SRG-OS-000259-GPOS-00100 | Severity: medium | CCI: CCI-001499

Vulnerability Discussion

If RHEL 8 were to allow any user to make changes to software libraries, then those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process.

This requirement applies to RHEL 8 with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs that execute with escalated privileges. Only qualified and authorized individuals will be allowed to obtain access to information system components for purposes of initiating changes, including upgrades and modifications.

Check

Verify the system commands contained in the following directories have mode "0755" or less permissive with the following command:

$ sudo find -L /bin /sbin /usr/bin /usr/sbin /usr/local/bin /usr/local/sbin -perm /0022 -exec ls -l {} \;

If any system commands are found to be group-writable or world-writable, this is a finding.

Fix

Configure the system commands to be protected from unauthorized access.

Run the following command, replacing "[FILE]" with any system command with a mode more permissive than "0755".

$ sudo chmod 0755 [FILE]

RHEL 8 system commands must be owned by root.

STIG ID: RHEL-08-010310 | SRG: SRG-OS-000259-GPOS-00100 | Severity: medium | CCI: CCI-001499

Vulnerability Discussion

Check

Verify the system commands contained in the following directories are owned by "root" with the following command:

$ sudo find -L /bin /sbin /usr/bin /usr/sbin /usr/local/bin /usr/local/sbin ! -user root -exec ls -l {} \;

If any system commands are returned, this is a finding.

Fix

Configure the system commands to be protected from unauthorized access.

Run the following command, replacing "[FILE]" with any system command file not owned by "root".

$ sudo chown root [FILE]

RHEL 8 system commands must be group-owned by root or a system account.

STIG ID: RHEL-08-010320 | SRG: SRG-OS-000259-GPOS-00100 | Severity: medium | CCI: CCI-001499

Vulnerability Discussion

Check

Verify the system commands contained in the following directories are group-owned by "root" with the following command:

$ sudo find -L /bin /sbin /usr/bin /usr/sbin /usr/local/bin /usr/local/sbin ! -group root -exec ls -l {} \;

If any system commands are returned and is not owned by a required system account, this is a finding.

Fix

Configure the system commands to be protected from unauthorized access.

Run the following command, replacing "[FILE]" with any system command file not group-owned by "root" or a required system account.

$ sudo chgrp root [FILE]

RHEL 8 library files must have mode 0755 or less permissive.

STIG ID: RHEL-08-010330 | SRG: SRG-OS-000259-GPOS-00100 | Severity: medium | CCI: CCI-001499

Vulnerability Discussion

Check

Verify the system-wide shared library files contained in the following directories have mode "0755" or less permissive with the following command:

$ sudo find -L /lib /lib64 /usr/lib /usr/lib64 -perm /0022 -type f -exec ls -l {} \;

If any system-wide shared library file is found to be group-writable or world-writable, this is a finding.

Fix

Configure the library files to be protected from unauthorized access. Run the following command, replacing "[FILE]" with any library file with a mode more permissive than 0755.

$ sudo chmod 0755 [FILE]

RHEL 8 library files must be owned by root.

STIG ID: RHEL-08-010340 | SRG: SRG-OS-000259-GPOS-00100 | Severity: medium | CCI: CCI-001499

Vulnerability Discussion

Check

Verify the system-wide shared library files are owned by "root" with the following command:

$ sudo find -L /lib /lib64 /usr/lib /usr/lib64 ! -user root -exec ls -l {} \;

If any system wide shared library file is returned, this is a finding.

Fix

Configure the system-wide shared library files (/lib, /lib64, /usr/lib and /usr/lib64) to be protected from unauthorized access.

Run the following command, replacing "[FILE]" with any library file not owned by "root".

$ sudo chown root [FILE]

RHEL 8 library files must be group-owned by root or a system account.

STIG ID: RHEL-08-010350 | SRG: SRG-OS-000259-GPOS-00100 | Severity: medium | CCI: CCI-001499

Vulnerability Discussion

Check

Verify the system-wide shared library files are group-owned by "root" with the following command:

$ sudo find -L /lib /lib64 /usr/lib /usr/lib64 ! -group root -exec ls -l {} \;

If any system wide shared library file is returned and is not group-owned by a required system account, this is a finding.

Fix

The RHEL 8 file integrity tool must notify the system administrator when changes to the baseline configuration or anomalies in the operation of any security functions are discovered within an organizationally defined frequency.

STIG ID: RHEL-08-010360 | SRG: SRG-OS-000363-GPOS-00150 | Severity: medium | CCI: CCI-001744

Vulnerability Discussion

Unauthorized changes to the baseline configuration could make the system vulnerable to various attacks or allow unauthorized access to the operating system. Changes to operating system configurations can have unintended side effects, some of which may be relevant to security.

Detecting such changes and providing an automated response can help avoid unintended, negative consequences that could ultimately affect the security state of the operating system. The operating system's Information Management Officer (IMO)/Information System Security Officer (ISSO) and System Administrators (SAs) must be notified via email and/or monitoring system trap when there is an unauthorized modification of a configuration item.

Notifications provided by information systems include messages to local computer consoles, and/or hardware indications, such as lights.

This capability must take into account operational requirements for availability for selecting an appropriate response. The organization may choose to shut down or restart the information system upon security function anomaly detection.

RHEL 8 comes with many optional software packages. A file integrity tool called Advanced Intrusion Detection Environment (AIDE) is one of those optional packages. This requirement assumes the use of AIDE; however, a different tool may be used if the requirements are met. Note that AIDE does not have a configuration that will send a notification, so a cron job is recommended that uses the mail application on the system to email the results of the file integrity check.

Satisfies: SRG-OS-000363-GPOS-00150, SRG-OS-000446-GPOS-00200, SRG-OS-000447-GPOS-00201

Check

Verify the operating system routinely checks the baseline configuration for unauthorized changes and notifies the system administrator when anomalies in the operation of any security functions are discovered.

Check to see if AIDE is installed on the system with the following command:

$ sudo yum list installed aide

If AIDE is not installed, ask the System Administrator how file integrity checks are performed on the system.

Check that RHEL 8 routinely executes a file integrity scan for changes to the system baseline. The command used in the example will use a daily occurrence.

Check the cron directories for scripts controlling the execution and notification of results of the file integrity application. For example, if AIDE is installed on the system, use the following commands:

$ sudo ls -al /etc/cron.* | grep aide

-rwxr-xr-x 1 root root 29 Nov 22 2015 aide

$ sudo grep aide /etc/crontab /var/spool/cron/root

/etc/crontab: 30 04 * * * root usr/sbin/aide
/var/spool/cron/root: 30 04 * * * root usr/sbin/aide

$ sudo more /etc/cron.daily/aide

#!/bin/bash
/usr/sbin/aide --check | /bin/mail -s "$HOSTNAME - Daily aide integrity check run" [email protected]

If the file integrity application does not exist, or a script file controlling the execution of the file integrity application does not exist, or the file integrity application does not notify designated personnel of changes, this is a finding.

Fix

Configure the file integrity tool to run automatically on the system at least weekly and to notify designated personnel if baseline configurations are changed in an unauthorized manner. The AIDE tool can be configured to email designated personnel with the use of the cron system.

The following example output is generic. It will set cron to run AIDE daily and to send email at the completion of the analysis.

$ sudo more /etc/cron.daily/aide

#!/bin/bash

/usr/sbin/aide --check | /bin/mail -s "$HOSTNAME - Daily aide integrity check run" [email protected]

RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components from a repository without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization.

STIG ID: RHEL-08-010370 | SRG: SRG-OS-000366-GPOS-00153 | Severity: high | CCI: CCI-001749

Vulnerability Discussion

Changes to any software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor.

Accordingly, patches, service packs, device drivers, or operating system components must be signed with a certificate recognized and approved by the organization.

Verifying the authenticity of the software prior to installation validates the integrity of the patch or upgrade received from a vendor. This verifies the software has not been tampered with and that it has been provided by a trusted vendor. Self-signed certificates are disallowed by this requirement. The operating system should not have to verify the software again. This requirement does not mandate DoD certificates for this purpose; however, the certificate used to verify the software must be from an approved CA.

Check

Verify the operating system prevents the installation of patches, service packs, device drivers, or operating system components from a repository without verification that they have been digitally signed using a certificate that is recognized and approved by the organization.

Check that YUM verifies the signature of packages from a repository prior to install with the following command:

$ sudo egrep '^\[.*\]|gpgcheck' /etc/yum.repos.d/*.repo

/etc/yum.repos.d/appstream.repo:[appstream]
/etc/yum.repos.d/appstream.repo:gpgcheck=1
/etc/yum.repos.d/baseos.repo:[baseos]
/etc/yum.repos.d/baseos.repo:gpgcheck=1

If "gpgcheck" is not set to "1", or if options are missing or commented out, ask the System Administrator how the certificates for patches and other operating system components are verified.

If there is no process to validate certificates that is approved by the organization, this is a finding.

Fix

Configure the operating system to verify the signature of packages from a repository prior to install by setting the following option in the "/etc/yum.repos.d/[your_repo_name].repo" file:

gpgcheck=1

RHEL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization.

STIG ID: RHEL-08-010371 | SRG: SRG-OS-000366-GPOS-00153 | Severity: high | CCI: CCI-001749

Vulnerability Discussion

Check

Fix

Configure the operating system to remove all software components after updated versions have been installed.

Set the "localpkg_gpgcheck" option to "True" in the "/etc/dnf/dnf.conf" file:

localpkg_gpgcheck=True

RHEL 8 must prevent the loading of a new kernel for later execution.

STIG ID: RHEL-08-010372 | SRG: SRG-OS-000366-GPOS-00153 | Severity: medium | CCI: CCI-001749

Vulnerability Discussion

Changes to any software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and that it has been provided by a trusted vendor.

Disabling kexec_load prevents an unsigned kernel image (that could be a windows kernel or modified vulnerable kernel) from being loaded. Kexec can be used subvert the entire secureboot process and should be avoided at all costs especially since it can load unsigned kernel images.

Check

Verify the operating system is configured to disable kernel image loading with the following commands:

Check the status of the kernel.kexec_load_disabled kernel parameter

$ sudo sysctl kernel.kexec_load_disabled

kernel.kexec_load_disabled = 1

If "kernel.kexec_load_disabled" is not set to "1" or is missing, this is a finding.

Check that the configuration files are present to enable this kernel parameter

$ sudo grep -r kernel.kexec_load_disabled /etc/sysctl.conf /etc/sysctl.d/*.conf

/etc/sysctl.d/99-sysctl.conf:kernel.kexec_load_disabled = 1

If "kernel.kexec_load_disabled" is not set to "1", is missing or commented out, this is a finding.

Fix

Configure the operating system to disable kernel image loading.

Add or edit the following line in a system configuration file in the "/etc/sysctl.d/" directory:

kernel.kexec_load_disabled = 1

Load settings from all system configuration files with the following command:

$ sudo sysctl --system

RHEL 8 must enable kernel parameters to enforce discretionary access control on symlinks.

STIG ID: RHEL-08-010373 | SRG: SRG-OS-000312-GPOS-00122 | Severity: medium | CCI: CCI-002165

Vulnerability Discussion

Discretionary Access Control (DAC) is based on the notion that individual users are "owners" of objects and therefore have discretion over who should be authorized to access the object and in which mode (e.g., read or write). Ownership is usually acquired as a consequence of creating the object or via specified ownership assignment. DAC allows the owner to determine who will have access to objects they control. An example of DAC includes user-controlled file permissions.

When discretionary access control policies are implemented, subjects are not constrained with regard to what actions they can take with information for which they have already been granted access. Thus, subjects that have been granted access to information are not prevented from passing (i.e., the subjects have the discretion to pass) the information to other subjects or objects. A subject that is constrained in its operation by Mandatory Access Control policies is still able to operate under the less rigorous constraints of this requirement. Thus, while Mandatory Access Control imposes constraints preventing a subject from passing information to another subject operating at a different sensitivity level, this requirement permits the subject to pass the information to any subject at the same sensitivity level. The policy is bounded by the information system boundary. Once the information is passed outside the control of the information system, additional means may be required to ensure the constraints remain in effect. While the older, more traditional definitions of discretionary access control require identity-based access control, that limitation is not required for this use of discretionary access control.

By enabling the fs.protected_symlinks kernel parameter, symbolic links are permitted to be followed only when outside a sticky world-writable directory, or when the UID of the link and follower match, or when the directory owner matches the symlink's owner. Disallowing such symlinks helps mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().

Satisfies: SRG-OS-000312-GPOS-00122, SRG-OS-000312-GPOS-00123, SRG-OS-000312-GPOS-00124, SRG-OS-000324-GPOS-00125

Check

Verify the operating system is configured to enable DAC on symlinks with the following commands:

Check the status of the fs.protected_symlinks kernel parameter

$ sudo sysctl fs.protected_symlinks

fs.protected_symlinks = 1

If "fs.protected_symlinks" is not set to "1" or is missing, this is a finding.

Check that the configuration files are present to enable this kernel parameter

$ sudo grep -r fs.protected_symlinks /etc/sysctl.conf /etc/sysctl.d/*.conf

/etc/sysctl.d/99-sysctl.conf:fs.protected_symlinks = 1

If "fs.protected_symlinks" is not set to "1", is missing or commented out, this is a finding.

Fix

Configure the operating system to enable DAC on symlinks.

Add or edit the following line in a system configuration file in the "/etc/sysctl.d/" directory:

fs.protected_symlinks = 1

Load settings from all system configuration files with the following command:

$ sudo sysctl --system

RHEL 8 must enable kernel parameters to enforce discretionary access control on hardlinks.

STIG ID: RHEL-08-010374 | SRG: SRG-OS-000312-GPOS-00122 | Severity: medium | CCI: CCI-002165

Vulnerability Discussion

Discretionary Access Control (DAC) is based on the notion that individual users are "owners" of objects and therefore have discretion over who should be authorized to access the object and in which mode (e.g., read or write). Ownership is usually acquired as a consequence of creating the object or via specified ownership assignment. DAC allows the owner to determine who will have access to objects they control. An example of DAC includes user-controlled file permissions.

When discretionary access control policies are implemented, subjects are not constrained with regard to what actions they can take with information for which they have already been granted access. Thus, subjects that have been granted access to information are not prevented from passing (i.e., the subjects have the discretion to pass) the information to other subjects or objects. A subject that is constrained in its operation by Mandatory Access Control policies is still able to operate under the less rigorous constraints of this requirement. Thus, while Mandatory Access Control imposes constraints preventing a subject from passing information to another subject operating at a different sensitivity level, this requirement permits the subject to pass the information to any subject at the same sensitivity level. The policy is bounded by the information system boundary. Once the information is passed outside the control of the information system, additional means may be required to ensure the constraints remain in effect. While the older, more traditional definitions of discretionary access control require identity-based access control, that limitation is not required for this use of discretionary access control.

By enabling the fs.protected_hardlinks kernel parameter, users can no longer create soft or hard links to files they do not own. Disallowing such hardlinks mitigate vulnerabilities based on insecure file system accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().

Satisfies: SRG-OS-000312-GPOS-00122, SRG-OS-000312-GPOS-00123, SRG-OS-000312-GPOS-00124, SRG-OS-000324-GPOS-00125

Check

Verify the operating system is configured to enable DAC on hardlinks with the following commands:

Check the status of the fs.protected_hardlinks kernel parameter.

$ sudo sysctl fs.protected_hardlinks

fs.protected_hardlinks = 1

If "fs.protected_hardlinks" is not set to "1" or is missing, this is a finding.

Check that the configuration files are present to enable this kernel parameter.

$ sudo grep -r fs.protected_hardlinks /etc/sysctl.conf /etc/sysctl.d/*.conf

/etc/sysctl.d/99-sysctl.conf:fs.protected_hardlinks = 1

If "fs.protected_hardlinks" is not set to "1", is missing or commented out, this is a finding.

Fix

Configure the operating system to enable DAC on hardlinks.

Add or edit the following line in a system configuration file in the "/etc/sysctl.d/" directory:

fs.protected_hardlinks = 1

Load settings from all system configuration files with the following command:

$ sudo sysctl --system

RHEL 8 must restrict access to the kernel message buffer.

STIG ID: RHEL-08-010375 | SRG: SRG-OS-000138-GPOS-00069 | Severity: low | CCI: CCI-001090

Vulnerability Discussion

Check

Verify the operating system is configured to restrict access to the kernel message buffer with the following commands:

Check the status of the kernel.dmesg_restrict kernel parameter.

$ sudo sysctl kernel.dmesg_restrict

kernel.dmesg_restrict = 1

If "kernel.dmesg_restrict" is not set to "1" or is missing, this is a finding.

Check that the configuration files are present to enable this kernel parameter.

$ sudo grep -r kernel.dmesg_restrict /etc/sysctl.conf /etc/sysctl.d/*.conf

/etc/sysctl.d/99-sysctl.conf:kernel.dmesg_restrict = 1

If "kernel.dmesg_restrict" is not set to "1", is missing or commented out, this is a finding.

Fix

Configure the operating system to restrict access to the kernel message buffer.

Add or edit the following line in a system configuration file in the "/etc/sysctl.d/" directory:

kernel.dmesg_restrict = 1

Load settings from all system configuration files with the following command:

$ sudo sysctl --system

RHEL 8 must prevent kernel profiling by unprivileged users.

STIG ID: RHEL-08-010376 | SRG: SRG-OS-000138-GPOS-00069 | Severity: low | CCI: CCI-001090

Vulnerability Discussion

Check

Verify the operating system is configured to prevent kernel profiling by unprivileged users with the following commands:

Check the status of the kernel.perf_event_paranoid kernel parameter.

$ sudo sysctl kernel.perf_event_paranoid

kernel.perf_event_paranoid = 2

If "kernel.perf_event_paranoid" is not set to "2" or is missing, this is a finding.

Check that the configuration files are present to enable this kernel parameter.

$ sudo grep -r kernel.perf_event_paranoid /etc/sysctl.conf /etc/sysctl.d/*.conf

/etc/sysctl.d/99-sysctl.conf:kernel.perf_event_paranoid = 2

If "kernel.perf_event_paranoid" is not set to "2", is missing or commented out, this is a finding.

Fix

Configure the operating system to prevent kernel profiling by unprivileged users.

Add or edit the following line in a system configuration file in the "/etc/sysctl.d/" directory:

kernel.perf_event_paranoid = 2

Load settings from all system configuration files with the following command:

$ sudo sysctl --system

RHEL 8 must require users to provide a password for privilege escalation.

STIG ID: RHEL-08-010380 | SRG: SRG-OS-000373-GPOS-00156 | Severity: medium | CCI: CCI-002038

Vulnerability Discussion

Without reauthentication, users may access resources or perform tasks for which they do not have authorization.

When operating systems provide the capability to escalate a functional capability, it is critical the user reauthenticate.

Satisfies: SRG-OS-000373-GPOS-00156, SRG-OS-000373-GPOS-00157, SRG-OS-000373-GPOS-00158

Check

Verify that "/etc/sudoers" has no occurrences of "NOPASSWD".

Check that the "/etc/sudoers" file has no occurrences of "NOPASSWD" by running the following command:

$ sudo grep -i nopasswd /etc/sudoers /etc/sudoers.d/*

%admin ALL=(ALL) NOPASSWD: ALL

If any occurrences of "NOPASSWD" are returned from the command and have not been documented with the ISSO as an organizationally defined administrative group utilizing MFA, this is a finding.

Fix

Remove any occurrence of "NOPASSWD" found in "/etc/sudoers" file or files in the "/etc/sudoers.d" directory.

RHEL 8 must require users to reauthenticate for privilege escalation.

STIG ID: RHEL-08-010381 | SRG: SRG-OS-000373-GPOS-00156 | Severity: medium | CCI: CCI-002038

Vulnerability Discussion

Check

Verify that "/etc/sudoers" has no occurrences of "!authenticate".

Check that the "/etc/sudoers" file has no occurrences of "!authenticate" by running the following command:

$ sudo grep -i !authenticate /etc/sudoers /etc/sudoers.d/*

If any occurrences of "!authenticate" return from the command, this is a finding.

Fix

Remove any occurrence of "!authenticate" found in "/etc/sudoers" file or files in the "/etc/sudoers.d" directory.

RHEL 8 must restrict privilege elevation to authorized personnel.

STIG ID: RHEL-08-010382 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The sudo command allows a user to execute programs with elevated (administrator) privileges. It prompts the user for their password and confirms your request to execute a command by checking a file, called sudoers. If the "sudoers" file is not configured correctly, any user defined on the system can initiate privileged actions on the target system.

Check

Verify the "sudoers" file restricts sudo access to authorized personnel.
$ sudo grep -iw 'ALL' /etc/sudoers /etc/sudoers.d/*

If the either of the following entries are returned, this is a finding:
ALL ALL=(ALL) ALL
ALL ALL=(ALL:ALL) ALL

Fix

Remove the following entries from the sudoers file:
ALL ALL=(ALL) ALL
ALL ALL=(ALL:ALL) ALL

RHEL 8 must use the invoking user's password for privilege escalation when using "sudo".

STIG ID: RHEL-08-010383 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-002227

Vulnerability Discussion

The sudoers security policy requires that users authenticate themselves before they can use sudo. When sudoers requires authentication, it validates the invoking user's credentials. If the rootpw, targetpw, or runaspw flags are defined and not disabled, by default the operating system will prompt the invoking user for the "root" user password.
For more information on each of the listed configurations, reference the sudoers(5) manual page.

Check

Verify that the sudoers security policy is configured to use the invoking user's password for privilege escalation.

$ sudo egrep -i '(!rootpw|!targetpw|!runaspw)' /etc/sudoers /etc/sudoers.d/* | grep -v '#'

/etc/sudoers:Defaults !targetpw
/etc/sudoers:Defaults !rootpw
/etc/sudoers:Defaults !runaspw

If no results are returned, this is a finding
If "Defaults !targetpw" is not defined, this is a finding.
If "Defaults !rootpw" is not defined, this is a finding.
If "Defaults !runaspw" is not defined, this is a finding.

Fix

Define the following in the Defaults section of the /etc/sudoers file or a configuration file in the /etc/sudoers.d/ directory:
Defaults !targetpw
Defaults !rootpw
Defaults !runaspw

RHEL 8 must require re-authentication when using the "sudo" command.

STIG ID: RHEL-08-010384 | SRG: SRG-OS-000373-GPOS-00156 | Severity: medium | CCI: CCI-002038

Vulnerability Discussion

Without re-authentication, users may access resources or perform tasks for which they do not have authorization.

When operating systems provide the capability to escalate a functional capability, it is critical the organization requires the user to re-authenticate when using the "sudo" command.

If the value is set to an integer less than 0, the user's time stamp will not expire and the user will not have to re-authenticate for privileged actions until the user's session is terminated.

Check

Verify the operating system requires re-authentication when using the "sudo" command to elevate privileges.

$ sudo grep -i 'timestamp_timeout' /etc/sudoers /etc/sudoers.d/*
/etc/sudoers:Defaults timestamp_timout=0

If "timestamp_timeout" is set to a negative number, is commented out, or no results are returned, this is a finding.

Fix

Configure the "sudo" command to require re-authentication.
Edit the /etc/sudoers file:
$ sudo visudo

Add or modify the following line:
Defaults timestamp_timeout=[value]
Note: The "[value]" must be a number that is greater than or equal to "0".

RHEL 8 must have the packages required for multifactor authentication installed.

STIG ID: RHEL-08-010390 | SRG: SRG-OS-000375-GPOS-00160 | Severity: medium | CCI: CCI-001948

Vulnerability Discussion

Using an authentication device, such as a DoD Common Access Card (CAC) or token that is separate from the information system, ensures that even if the information system is compromised, credentials stored on the authentication device will not be affected.

Multifactor solutions that require devices separate from information systems gaining access include, for example, hardware tokens providing time-based or challenge-response authenticators and smart cards such as the U.S. Government Personal Identity Verification (PIV) card and the DoD CAC.

A privileged account is defined as an information system account with authorizations of a privileged user.

Remote access is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

This requirement only applies to components where this is specific to the function of the device or has the concept of an organizational user (e.g., VPN, proxy capability). This does not apply to authentication for the purpose of configuring the device itself (management).

Check

Verify the operating system has the packages required for multifactor authentication installed with the following commands:

$ sudo yum list installed esc openssl-pkcs11

esc.x86_64 1.1.2-7.el8 @AppStream
openssl-pkcs11.x86_64 0.4.8-2.el8 @anaconda

If the "esc" and "openssl-pkcs11" packages are not installed, ask the administrator to indicate what type of multifactor authentication is being utilized and what packages are installed to support it. If there is no evidence of multifactor authentication being used, this is a finding.

Fix

Configure the operating system to implement multifactor authentication by installing the required packages with the following command:

$ sudo yum install esc openssl-pkcs11

RHEL 8 must implement certificate status checking for multifactor authentication.

STIG ID: RHEL-08-010400 | SRG: SRG-OS-000375-GPOS-00160 | Severity: medium | CCI: CCI-001948

Vulnerability Discussion

Using an authentication device, such as a DoD Common Access Card (CAC) or token that is separate from the information system, ensures that even if the information system is compromised, credentials stored on the authentication device will not be affected.

Multifactor solutions that require devices separate from information systems gaining access include, for example, hardware tokens providing time-based or challenge-response authenticators and smart cards such as the U.S. Government Personal Identity Verification (PIV) card and the DoD CAC.

RHEL 8 includes multiple options for configuring certificate status checking, but for this requirement focuses on the System Security Services Daemon (SSSD). By default, sssd performs Online Certificate Status Protocol (OCSP) checking and certificate verification using a sha256 digest function.

Satisfies: SRG-OS-000375-GPOS-00160, SRG-OS-000377-GPOS-00162

Check

Verify the operating system implements certificate status checking for multifactor authentication.

Check to see if Online Certificate Status Protocol (OCSP) is enabled and using the proper digest value on the system with the following command:

$ sudo grep certificate_verification /etc/sssd/sssd.conf | grep -v "^#"

certificate_verification = ocsp_dgst=sha1

If the certificate_verification line is missing "ocsp_dgst=sha1", ask the administrator to indicate what type of multifactor authentication is being utilized and how the system implements certificate status checking. If there is no evidence of certificate status checking being used, this is a finding.

Fix

Configure the operating system to implement certificate status checking for multifactor authentication.

Review the "/etc/sssd/sssd.conf" file to determine if the system is configured to prevent OCSP or certificate verification.

Add the following line to the "/etc/sssd/sssd.conf" file:

certificate_verification = ocsp_dgst=sha1

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must accept Personal Identity Verification (PIV) credentials.

STIG ID: RHEL-08-010410 | SRG: SRG-OS-000376-GPOS-00161 | Severity: medium | CCI: CCI-001953

Vulnerability Discussion

The use of PIV credentials facilitates standardization and reduces the risk of unauthorized access.

The DoD has mandated the use of the Common Access Card (CAC) to support identity management and personal authentication for systems covered under Homeland Security Presidential Directive (HSPD) 12, as well as making the CAC a primary component of layered protection for national security systems.

Check

Verify RHEL 8 accepts PIV credentials.

Check that the "opensc" package is installed on the system with the following command:

$ sudo yum list installed opensc

opensc.x86_64 0.19.0-5.el8 @anaconda

Check that "opensc" accepts PIV cards with the following command:

$ sudo opensc-tool --list-drivers | grep -i piv

PIV-II Personal Identity Verification Card

If the "opensc" package is not installed and the "opensc-tool" driver list does not include "PIV-II", this is a finding.

Fix

Configure RHEL 8 to accept PIV credentials.

Install the "opensc" package using the following command:

$ sudo yum install opensc

RHEL 8 must implement non-executable data to protect its memory from unauthorized code execution.

STIG ID: RHEL-08-010420 | SRG: SRG-OS-000433-GPOS-00192 | Severity: medium | CCI: CCI-002824

Vulnerability Discussion

Check

Verify the NX (no-execution) bit flag is set on the system.

Check that the no-execution bit flag is set with the following commands:

$ sudo dmesg | grep NX

[ 0.000000] NX (Execute Disable) protection: active

If "dmesg" does not show "NX (Execute Disable) protection" active, check the cpuinfo settings with the following command:

$ sudo less /proc/cpuinfo | grep -i flags
flags : fpu vme de pse tsc ms nx rdtscp lm constant_tsc

If "flags" does not contain the "nx" flag, this is a finding.

Fix

The NX bit execute protection must be enabled in the system BIOS.

RHEL 8 must clear the page allocator to prevent use-after-free attacks.

STIG ID: RHEL-08-010421 | SRG: SRG-OS-000134-GPOS-00068 | Severity: medium | CCI: CCI-001084

Vulnerability Discussion

Some adversaries launch attacks with the intent of executing code in non-executable regions of memory or in memory locations that are prohibited. Security safeguards employed to protect memory include, for example, data execution prevention and address space layout randomization. Data execution prevention safeguards can be either hardware-enforced or software-enforced with hardware providing the greater strength of mechanism.

Poisoning writes an arbitrary value to freed pages, so any modification or reference to that page after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory.

Satisfies: SRG-OS-000134-GPOS-00068, SRG-OS-000433-GPOS-00192

Check

Verify that GRUB 2 is configured to enable page poisoning to mitigate use-after-free vulnerabilities with the following commands:

Check that the current GRUB 2 configuration has page poisoning enabled:

$ sudo grub2-editenv - list | grep page_poison

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 page_poison=1 vsyscall=none audit=1 audit_backlog_limit=8192 boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If "page_poison" is not set to "1" or is missing, this is a finding.

Check that page poisoning is enabled by default to persist in kernel updates:

$ sudo grep page_poison /etc/default/grub

GRUB_CMDLINE_LINUX="page_poison=1"

If "page_poison" is not set to "1", is missing or commented out, this is a finding.

Fix

Configure RHEL 8 to enable page poisoning with the following commands:

$ sudo grubby --update-kernel=ALL --args="page_poison=1"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="page_poison=1"

RHEL 8 must disable virtual syscalls.

STIG ID: RHEL-08-010422 | SRG: SRG-OS-000134-GPOS-00068 | Severity: medium | CCI: CCI-001084

Vulnerability Discussion

Syscalls are special routines in the Linux kernel, which userspace applications ask to do privileged tasks. Invoking a system call is an expensive operation because the processor must interrupt the currently executing task and switch context to kernel mode and then back to userspace after the system call completes. Virtual Syscalls map into user space a page that contains some variables and the implementation of some system calls. This allows the system calls to be executed in userspace to alleviate the context switching expense.

Virtual Syscalls provide an opportunity of attack for a user who has control of the return instruction pointer. Disabling vsyscalls help to prevent return oriented programming (ROP) attacks via buffer overflows and overruns.

Satisfies: SRG-OS-000134-GPOS-00068, SRG-OS-000433-GPOS-00192

Check

Verify that GRUB 2 is configured to disable vsyscalls with the following commands:

Check that the current GRUB 2 configuration disables vsyscalls:

$ sudo grub2-editenv - list | grep vsyscall

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 page_poison=1 vsyscall=none audit=1 audit_backlog_limit=8192 boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If "vsyscall" is not set to "none" or is missing, this is a finding.

Check that vsyscalls are disabled by default to persist in kernel updates:

$ sudo grep vsyscall /etc/default/grub

GRUB_CMDLINE_LINUX="vsyscall=none"

If "vsyscall" is not set to "none", is missing or commented out, this is a finding.

Fix

Configure RHEL 8 to disable vsyscalls with the following commands:

$ sudo grubby --update-kernel=ALL --args="vsyscall=none"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="vsyscall=none"

RHEL 8 must clear SLUB/SLAB objects to prevent use-after-free attacks.

STIG ID: RHEL-08-010423 | SRG: SRG-OS-000134-GPOS-00068 | Severity: medium | CCI: CCI-001084

Vulnerability Discussion

Some adversaries launch attacks with the intent of executing code in non-executable regions of memory or in memory locations that are prohibited. Security safeguards employed to protect memory include, for example, data execution prevention and address space layout randomization. Data execution prevention safeguards can be either hardware-enforced or software-enforced with hardware providing the greater strength of mechanism.

Poisoning writes an arbitrary value to freed pages, so any modification or reference to that page after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. Also prevents leak of data and detection of corrupted memory.

SLAB objects are blocks of physically-contiguous memory. SLUB is the unqueued SLAB allocator.

Satisfies: SRG-OS-000134-GPOS-00068, SRG-OS-000433-GPOS-00192

Check

Verify that GRUB 2 is configured to enable poisoning of SLUB/SLAB objects to mitigate use-after-free vulnerabilities with the following commands:

Check that the current GRUB 2 configuration has poisoning of SLUB/SLAB objects enabled:

$ sudo grub2-editenv - list | grep slub_debug

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 slub_debug=P page_poison=1 vsyscall=none audit=1 audit_backlog_limit=8192 boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If "slub_debug" is not set to "P" or is missing, this is a finding.

Check that poisoning of SLUB/SLAB objects is enabled by default to persist in kernel updates:

$ sudo grep slub_debug /etc/default/grub

GRUB_CMDLINE_LINUX="slub_debug=P"

If "slub_debug" is not set to "P", is missing or commented out, this is a finding.

Fix

Configure RHEL 8 to enable poisoning of SLUB/SLAB objects with the following commands:

$ sudo grubby --update-kernel=ALL --args="slub_debug=P"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="slub_debug=P"

RHEL 8 must implement address space layout randomization (ASLR) to protect its memory from unauthorized code execution.

STIG ID: RHEL-08-010430 | SRG: SRG-OS-000433-GPOS-00193 | Severity: medium | CCI: CCI-002824

Vulnerability Discussion

Check

Verify RHEL 8 implements ASLR with the following command:

$ sudo sysctl kernel.randomize_va_space

kernel.randomize_va_space = 2

If nothing is returned, verify the kernel parameter "randomize_va_space" is set to "2" with the following command:

$ sudo cat /proc/sys/kernel/randomize_va_space

2

If "kernel.randomize_va_space" is not set to "2", this is a finding.

Fix

Configure the operating system to implement virtual address space randomization.

Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.d/*.conf"(or modify the line to have the required value):

kernel.randomize_va_space=2

Issue the following command to make the changes take effect:

$ sudo sysctl --system

YUM must remove all software components after updated versions have been installed on RHEL 8.

STIG ID: RHEL-08-010440 | SRG: SRG-OS-000437-GPOS-00194 | Severity: low | CCI: CCI-002617

Vulnerability Discussion

Previous versions of software components that are not removed from the information system after updates have been installed may be exploited by adversaries. Some information technology products may remove older versions of software automatically from the information system.

Check

Verify the operating system removes all software components after updated versions have been installed.

Check if YUM is configured to remove unneeded packages with the following command:

$ sudo grep -i clean_requirements_on_remove /etc/dnf/dnf.conf

clean_requirements_on_remove=True

If "clean_requirements_on_remove" is not set to either "1", "True", or "yes", commented out, or is missing from "/etc/dnf/dnf.conf", this is a finding.

Fix

Configure the operating system to remove all software components after updated versions have been installed.

Set the "clean_requirements_on_remove" option to "True" in the "/etc/dnf/dnf.conf" file:

clean_requirements_on_remove=True

RHEL 8 must enable the SELinux targeted policy.

STIG ID: RHEL-08-010450 | SRG: SRG-OS-000445-GPOS-00199 | Severity: medium | CCI: CCI-002696

Vulnerability Discussion

Check

Ensure the operating system verifies correct operation of all security functions.

Check if "SELinux" is active and is enforcing the targeted policy with the following command:

$ sudo sestatus

SELinux status: enabled
SELinuxfs mount: /sys/fs/selinux
SELinux root directory: /etc/selinux
Loaded policy name: targeted
Current mode: enforcing
Mode from config file: enforcing
Policy MLS status: enabled
Policy deny_unknown status: allowed
Memory protection checking: actual (secure)
Max kernel policy version: 31

If the "Loaded policy name" is not set to "targeted", this is a finding.

Verify that the /etc/selinux/config file is configured to the "SELINUXTYPE" to "targeted":

$ sudo grep -i "selinuxtype" /etc/selinux/config | grep -v '^#'

SELINUXTYPE = targeted

If no results are returned or "SELINUXTYPE" is not set to "targeted", this is a finding.

Fix

Configure the operating system to verify correct operation of all security functions.

Set the "SELinuxtype" to the "targeted" policy by modifying the "/etc/selinux/config" file to have the following line:

SELINUXTYPE=targeted

A reboot is required for the changes to take effect.

There must be no shosts.equiv files on the RHEL 8 operating system.

STIG ID: RHEL-08-010460 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

The "shosts.equiv" files are used to configure host-based authentication for the system via SSH. Host-based authentication is not sufficient for preventing unauthorized access to the system, as it does not require interactive identification and authentication of a connection request, or for the use of two-factor authentication.

Check

Verify there are no "shosts.equiv" files on RHEL 8 with the following command:

$ sudo find / -name shosts.equiv

If a "shosts.equiv" file is found, this is a finding.

Fix

Remove any found "shosts.equiv" files from the system.

$ sudo rm /etc/ssh/shosts.equiv

There must be no .shosts files on the RHEL 8 operating system.

STIG ID: RHEL-08-010470 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

The ".shosts" files are used to configure host-based authentication for individual users or the system via SSH. Host-based authentication is not sufficient for preventing unauthorized access to the system, as it does not require interactive identification and authentication of a connection request, or for the use of two-factor authentication.

Check

Verify there are no ".shosts" files on RHEL 8 with the following command:

$ sudo find / -name '*.shosts'

If any ".shosts" files are found, this is a finding.

Fix

Remove any found ".shosts" files from the system.

$ sudo rm /[path]/[to]/[file]/.shosts

RHEL 8 must enable the hardware random number generator entropy gatherer service.

STIG ID: RHEL-08-010471 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

The most important characteristic of a random number generator is its randomness, namely its ability to deliver random numbers that are impossible to predict. Entropy in computer security is associated with the unpredictability of a source of randomness. The random source with high entropy tends to achieve a uniform distribution of random values. Random number generators are one of the most important building blocks of cryptosystems.

The rngd service feeds random data from hardware device to kernel random device. Quality (non-predictable) random number generation is important for several security functions (i.e., ciphers).

Check

Check that RHEL 8 has enabled the hardware random number generator entropy gatherer service.

Verify the rngd service is enabled and active with the following commands:

$ sudo systemctl is-enabled rngd

enabled

$ sudo systemctl is-active rngd

active

If the service is not "enable and "active", this is a finding.

Fix

Start the rngd service, and enable the rngd service with the following commands:

$ sudo systemctl start rngd.service

$ sudo systemctl enable rngd.service

The RHEL 8 SSH public host key files must have mode 0644 or less permissive.

STIG ID: RHEL-08-010480 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If a public host key file is modified by an unauthorized user, the SSH service may be compromised.

Check

Verify the SSH public host key files have mode "0644" or less permissive with the following command:

$ sudo ls -l /etc/ssh/*.pub

-rw-r--r-- 1 root root 618 Nov 28 06:43 ssh_host_dsa_key.pub
-rw-r--r-- 1 root root 347 Nov 28 06:43 ssh_host_key.pub
-rw-r--r-- 1 root root 238 Nov 28 06:43 ssh_host_rsa_key.pub

If any key.pub file has a mode more permissive than "0644", this is a finding.

Note: SSH public key files may be found in other directories on the system depending on the installation.

Fix

Change the mode of public host key files under "/etc/ssh" to "0644" with the following command:

$ sudo chmod 0644 /etc/ssh/*key.pub

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

The RHEL 8 SSH private host key files must have mode 0640 or less permissive.

STIG ID: RHEL-08-010490 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If an unauthorized user obtains the private SSH host key file, the host could be impersonated.

Check

Verify the SSH private host key files have mode "0640" or less permissive with the following command:

$ sudo ls -l /etc/ssh/ssh_host*key

-rw------- 1 root ssh_keys 668 Nov 28 06:43 ssh_host_dsa_key
-rw------- 1 root ssh_keys 582 Nov 28 06:43 ssh_host_key
-rw------- 1 root ssh_keys 887 Nov 28 06:43 ssh_host_rsa_key

If any private host key file has a mode more permissive than "0640", this is a finding.

Fix

Configure the mode of SSH private host key files under "/etc/ssh" to "0640" with the following command:

$ sudo chmod 0640 /etc/ssh/ssh_host*key

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

The RHEL 8 SSH daemon must perform strict mode checking of home directory configuration files.

STIG ID: RHEL-08-010500 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If other users have access to modify user-specific SSH configuration files, they may be able to log on to the system as another user.

Check

Verify the SSH daemon performs strict mode checking of home directory configuration files with the following command:

$ sudo grep -i strictmodes /etc/ssh/sshd_config

StrictModes yes

If "StrictModes" is set to "no", is missing, or the returned line is commented out, this is a finding.

Fix

Configure SSH to perform strict mode checking of home directory configuration files. Uncomment the "StrictModes" keyword in "/etc/ssh/sshd_config" and set the value to "yes":

StrictModes yes

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

The RHEL 8 SSH daemon must not allow compression or must only allow compression after successful authentication.

STIG ID: RHEL-08-010510 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If compression is allowed in an SSH connection prior to authentication, vulnerabilities in the compression software could result in compromise of the system from an unauthenticated connection, potentially with root privileges.

Check

Verify the SSH daemon performs compression after a user successfully authenticates with the following command:

$ sudo grep -i compression /etc/ssh/sshd_config

Compression no

If the "Compression" keyword is set to "yes", "delayed", is missing, or the returned line is commented out, this is a finding.

Fix

Uncomment the "Compression" keyword in "/etc/ssh/sshd_config" (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor) on the system and set the value to "no":

Compression no

The SSH service must be restarted for changes to take effect.

The RHEL 8 SSH daemon must not allow authentication using known host’s authentication.

STIG ID: RHEL-08-010520 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Configuring this setting for the SSH daemon provides additional assurance that remote logon via SSH will require a password, even in the event of misconfiguration elsewhere.

Check

Verify the SSH daemon does not allow authentication using known host’s authentication with the following command:

$ sudo grep -i IgnoreUserKnownHosts /etc/ssh/sshd_config

IgnoreUserKnownHosts yes

If the value is returned as "no", the returned line is commented out, or no output is returned, this is a finding.

Fix

Configure the SSH daemon to not allow authentication using known host’s authentication.

Add the following line in "/etc/ssh/sshd_config", or uncomment the line and set the value to "yes":

IgnoreUserKnownHosts yes

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

The RHEL 8 SSH daemon must not allow unused methods of authentication.

STIG ID: RHEL-08-010521 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Configuring these settings for the SSH daemon provides additional assurance that remote logon via SSH will not use unused methods of authentication, even in the event of misconfiguration elsewhere.

Check

Verify the SSH daemon does not allow authentication using unused methods of authentication with the following command:

$ sudo grep -i "KerberosAuthentication\|GSSAPIAuthentication" /etc/ssh/sshd_config

KerberosAuthentication no
GSSAPIAuthentication no

If the values are returned as "yes", the returned line is commented out, no output is returned, or has not been documented with the ISSO, this is a finding.

Fix

Configure the SSH daemon to not allow authentication using unused methods of authentication.

Add the following line in "/etc/ssh/sshd_config", or uncomment the line and set the value to "no":

KerberosAuthentication no
GSSAPIAuthentication no

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

RHEL 8 must use a separate file system for /var.

STIG ID: RHEL-08-010540 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.

Check

Verify that a separate file system/partition has been created for "/var".

Check that a file system/partition has been created for "/var" with the following command:

$ sudo grep /var /etc/fstab

UUID=c274f65f /var xfs noatime,nobarrier 1 2

If a separate entry for "/var" is not in use, this is a finding.

Fix

Migrate the "/var" path onto a separate file system.

RHEL 8 must use a separate file system for /var/log.

STIG ID: RHEL-08-010541 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.

Check

Verify that a separate file system/partition has been created for "/var/log".

Check that a file system/partition has been created for "/var/log" with the following command:

$ sudo grep /var/log /etc/fstab

UUID=c274f65f /var/log xfs noatime,nobarrier 1 2

If a separate entry for "/var/log" is not in use, this is a finding.

Fix

Migrate the "/var/log" path onto a separate file system.

RHEL 8 must use a separate file system for the system audit data path.

STIG ID: RHEL-08-010542 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.

Check

Verify that a separate file system/partition has been created for the system audit data path with the following command:

Note: /var/log/audit is used as the example as it is a common location.

$ sudo grep /var/log/audit /etc/fstab

UUID=3645951a /var/log/audit xfs defaults 1 2

If an entry for "/var/log/audit" does not exist, ask the System Administrator if the system audit logs are being written to a different file system/partition on the system, then grep for that file system/partition.

If a separate file system/partition does not exist for the system audit data path, this is a finding.

Fix

Migrate the system audit data path onto a separate file system.

A separate RHEL 8 filesystem must be used for the /tmp directory.

STIG ID: RHEL-08-010543 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.

Check

Verify that a separate file system/partition has been created for non-privileged local interactive user home directories.

$ sudo grep /tmp /etc/fstab

/dev/mapper/rhel-tmp /tmp xfs defaults,nodev,nosuid,noexec 0 0

If a separate entry for the file system/partition "/tmp" does not exist, this is a finding.

Fix

Migrate the "/tmp" directory onto a separate file system/partition.

RHEL 8 must not permit direct logons to the root account using remote access via SSH.

STIG ID: RHEL-08-010550 | SRG: SRG-OS-000109-GPOS-00056 | Severity: medium | CCI: CCI-000770

Vulnerability Discussion

Even though the communications channel may be encrypted, an additional layer of security is gained by extending the policy of not logging on directly as root. In addition, logging on with a user-specific account provides individual accountability of actions performed on the system.

Check

Verify remote access using SSH prevents users from logging on directly as "root".

Check that SSH prevents users from logging on directly as "root" with the following command:

$ sudo grep -i PermitRootLogin /etc/ssh/sshd_config

PermitRootLogin no

If the "PermitRootLogin" keyword is set to "yes", is missing, or is commented out, this is a finding.

Fix

Configure RHEL 8 to stop users from logging on remotely as the "root" user via SSH.

Edit the appropriate "/etc/ssh/sshd_config" file to uncomment or add the line for the "PermitRootLogin" keyword and set its value to "no":

PermitRootLogin no

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

The auditd service must be running in RHEL 8.

STIG ID: RHEL-08-010560 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Configuring RHEL 8 to implement organization-wide security implementation guides and security checklists ensures compliance with federal standards and establishes a common security baseline across the DoD that reflects the most restrictive security posture consistent with operational requirements.

Configuration settings are the set of parameters that can be changed in hardware, software, or firmware components of the system that affect the security posture and/or functionality of the system. Security-related parameters are those parameters impacting the security state of the system, including the parameters required to satisfy other security control requirements. Security-related parameters include, for example: registry settings; account, file, directory permission settings; and settings for functions, ports, protocols, services, and remote connections.

Check

Verify the audit service is enabled and active with the following commands:

$ sudo systemctl is-enabled auditd

enabled

$ sudo systemctl is-active auditd

active

If the service is not "enabled" and "active" this is a finding.

Fix

Start the auditd service, and enable the auditd service with the following commands:

$ sudo systemctl start auditd.service

$ sudo systemctl enable auditd.service

The rsyslog service must be running in RHEL 8.

STIG ID: RHEL-08-010561 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the rsyslog service is enabled and active with the following commands:

$ sudo systemctl is-enabled rsyslog

enabled

$ sudo systemctl is-active rsyslog

active

If the service is not "enabled" and "active" this is a finding.

Fix

Start the auditd service, and enable the rsyslog service with the following commands:

$ sudo systemctl start rsyslog.service

$ sudo systemctl enable rsyslog.service

RHEL 8 must prevent files with the setuid and setgid bit set from being executed on file systems that contain user home directories.

STIG ID: RHEL-08-010570 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The "nosuid" mount option causes the system not to execute "setuid" and "setgid" files with owner privileges. This option must be used for mounting any file system not containing approved "setuid" and "setguid" files. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

Check

Verify file systems that contain user home directories are mounted with the "nosuid" option.

Note: If a separate file system has not been created for the user home directories (user home directories are mounted under "/"), this is automatically a finding as the "nosuid" option cannot be used on the "/" system.

Find the file system(s) that contain the user home directories with the following command:

$ sudo awk -F: '($3>=1000)&&($7 !~ /nologin/){print $1,$3,$6}' /etc/passwd

smithj:1001: /home/smithj
robinst:1002: /home/robinst

Check the file systems that are mounted at boot time with the following command:

$ sudo more /etc/fstab

UUID=a411dc99-f2a1-4c87-9e05-184977be8539 /home xfs rw,relatime,discard,data=ordered,nosuid,nodev,noexec 0 0

If a file system found in "/etc/fstab" refers to the user home directory file system and it does not have the "nosuid" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "nosuid" option on file systems that contain user home directories for interactive users.

RHEL 8 must prevent files with the setuid and setgid bit set from being executed on the /boot directory.

STIG ID: RHEL-08-010571 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the /boot directory is mounted with the "nosuid" option with the following command:

$ sudo mount | grep '\s/boot\s'

/dev/sda1 on /boot type xfs (rw,nosuid,relatime,seclabe,attr2,inode64,noquota)

If the /boot file system does not have the "nosuid" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "nosuid" option on the /boot directory.

RHEL 8 must prevent special devices on non-root local partitions.

STIG ID: RHEL-08-010580 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access. The only legitimate location for device files is the /dev directory located on the root partition.

Check

Verify all non-root local partitions are mounted with the "nodev" option with the following command:

$ sudo mount | grep '^/dev\S* on /\S' | grep --invert-match 'nodev'

If any output is produced, this is a finding.

Fix

Configure the "/etc/fstab" to use the "nodev" option on all non-root local partitions.

RHEL 8 must prevent code from being executed on file systems that contain user home directories.

STIG ID: RHEL-08-010590 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The "noexec" mount option causes the system not to execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

Check

Verify file systems that contain user home directories are mounted with the "noexec" option.

Note: If a separate file system has not been created for the user home directories (user home directories are mounted under "/"), this is automatically a finding as the "noexec" option cannot be used on the "/" system.

Find the file system(s) that contain the user home directories with the following command:

$ sudo awk -F: '($3>=1000)&&($7 !~ /nologin/){print $1,$3,$6}' /etc/passwd

smithj:1001: /home/smithj
robinst:1002: /home/robinst

Check the file systems that are mounted at boot time with the following command:

$ sudo more /etc/fstab

UUID=a411dc99-f2a1-4c87-9e05-184977be8539 /home ext4 rw,relatime,discard,data=ordered,nosuid,nodev,noexec 0 2

If a file system found in "/etc/fstab" refers to the user home directory file system and it does not have the "noexec" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "noexec" option on file systems that contain user home directories for interactive users.

RHEL 8 must prevent special devices on file systems that are used with removable media.

STIG ID: RHEL-08-010600 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The "nodev" mount option causes the system not to interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

Check

Verify file systems that are used for removable media are mounted with the "nodev" option with the following command:

$ sudo more /etc/fstab

UUID=2bc871e4-e2a3-4f29-9ece-3be60c835222 /mnt/usbflash vfat noauto,owner,ro,nosuid,nodev,noexec 0 0

If a file system found in "/etc/fstab" refers to removable media and it does not have the "nodev" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "nodev" option on file systems that are associated with removable media.

RHEL 8 must prevent code from being executed on file systems that are used with removable media.

STIG ID: RHEL-08-010610 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify file systems that are used for removable media are mounted with the "noexec" option with the following command:

$ sudo more /etc/fstab

UUID=2bc871e4-e2a3-4f29-9ece-3be60c835222 /mnt/usbflash vfat noauto,owner,ro,nosuid,nodev,noexec 0 0

If a file system found in "/etc/fstab" refers to removable media and it does not have the "noexec" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "noexec" option on file systems that are associated with removable media.

RHEL 8 must prevent files with the setuid and setgid bit set from being executed on file systems that are used with removable media.

STIG ID: RHEL-08-010620 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify file systems that are used for removable media are mounted with the "nosuid" option with the following command:

$ sudo more /etc/fstab

UUID=2bc871e4-e2a3-4f29-9ece-3be60c835222 /mnt/usbflash vfat noauto,owner,ro,nosuid,nodev,noexec 0 0

If a file system found in "/etc/fstab" refers to removable media and it does not have the "nosuid" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "nosuid" option on file systems that are associated with removable media.

RHEL 8 must prevent code from being executed on file systems that are imported via Network File System (NFS).

STIG ID: RHEL-08-010630 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The "noexec" mount option causes the system not to execute binary files. This option must be used for mounting any file system not containing approved binary as they may be incompatible. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

Check

Verify that file systems being imported via NFS are mounted with the "noexec" option with the following command:

$ sudo grep nfs /etc/fstab | grep noexec

UUID=e06097bb-cfcd-437b-9e4d-a691f5662a7d /store nfs rw,nosuid,nodev,noexec 0 0

If a file system found in "/etc/fstab" refers to NFS and it does not have the "noexec" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "noexec" option on file systems that are being imported via NFS.

RHEL 8 must prevent special devices on file systems that are imported via Network File System (NFS).

STIG ID: RHEL-08-010640 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify file systems that are being NFS-imported are mounted with the "nodev" option with the following command:

$ sudo grep nfs /etc/fstab | grep nodev

UUID=e06097bb-cfcd-437b-9e4d-a691f5662a7d /store nfs rw,nosuid,nodev,noexec 0 0

If a file system found in "/etc/fstab" refers to NFS and it does not have the "nodev" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "nodev" option on file systems that are being imported via NFS.

RHEL 8 must prevent files with the setuid and setgid bit set from being executed on file systems that are imported via Network File System (NFS).

STIG ID: RHEL-08-010650 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify that file systems being imported via NFS are mounted with the "nosuid" option with the following command:

$ sudo grep nfs /etc/fstab | grep nosuid

UUID=e06097bb-cfcd-437b-9e4d-a691f5662a7d /store nfs rw,nosuid,nodev,noexec 0 0

If a file system found in "/etc/fstab" refers to NFS and it does not have the "nosuid" option set, this is a finding.

Fix

Configure the "/etc/fstab" to use the "nosuid" option on file systems that are being imported via NFS.

Local RHEL 8 initialization files must not execute world-writable programs.

STIG ID: RHEL-08-010660 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If user start-up files execute world-writable programs, especially in unprotected directories, they could be maliciously modified to destroy user files or otherwise compromise the system at the user level. If the system is compromised at the user level, it is easier to elevate privileges to eventually compromise the system at the root and network level.

Check

Verify that local initialization files do not execute world-writable programs.

Check the system for world-writable files.

The following command will discover and print world-writable files. Run it once for each local partition [PART]:

$ sudo find [PART] -xdev -type f -perm -0002 -print

For all files listed, check for their presence in the local initialization files with the following commands:

Note: The example will be for a system that is configured to create user home directories in the "/home" directory.

$ sudo grep /home/*/.*

If any local initialization files are found to reference world-writable files, this is a finding.

Fix

Set the mode on files being executed by the local initialization files with the following command:

$ sudo chmod 0755

RHEL 8 must disable kernel dumps unless needed.

STIG ID: RHEL-08-010670 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Kernel core dumps may contain the full contents of system memory at the time of the crash. Kernel core dumps may consume a considerable amount of disk space and may result in denial of service by exhausting the available space on the target file system partition.

RHEL 8 installation media presents the option to enable or disable the kdump service at the time of system installation.

Check

Verify that kernel core dumps are disabled unless needed with the following command:

$ sudo systemctl status kdump.service

kdump.service - Crash recovery kernel arming
Loaded: loaded (/usr/lib/systemd/system/kdump.service; enabled; vendor preset: enabled)
Active: active (exited) since Mon 2020-05-04 16:08:09 EDT; 3min ago
Main PID: 1130 (code=exited, status=0/SUCCESS)

If the "kdump" service is active, ask the System Administrator if the use of the service is required and documented with the Information System Security Officer (ISSO).

If the service is active and is not documented, this is a finding.

Fix

If kernel core dumps are not required, disable the "kdump" service with the following command:

# systemctl disable kdump.service

If kernel core dumps are required, document the need with the ISSO.

RHEL 8 must disable the kernel.core_pattern.

STIG ID: RHEL-08-010671 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 disables storing core dumps with the following commands:

$ sudo sysctl kernel.core_pattern

kernel.core_pattern = |/bin/false

If the returned line does not have a value of "|/bin/false", or a line is not returned and the need for core dumps is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure RHEL 8 to disable storing core dumps by adding the following line to a file in the "/etc/sysctl.d" directory:

kernel.core_pattern = |/bin/false

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

RHEL 8 must disable acquiring, saving, and processing core dumps.

STIG ID: RHEL-08-010672 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 is not configured to acquire, save, or process core dumps with the following command:

$ sudo systemctl status systemd-coredump.socket

systemd-coredump.socket
Loaded: masked (Reason: Unit ctrl-alt-del.target is masked.)
Active: inactive (dead)

If the "systemd-coredump.socket" is loaded and not masked and the need for core dumps is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the system to disable the systemd-coredump.socket with the following command:

$ sudo systemctl mask systemd-coredump.socket

Created symlink /etc/systemd/system/systemd-coredump.socket -> /dev/null

Reload the daemon for this change to take effect.

$ sudo systemctl daemon-reload

RHEL 8 must disable core dumps for all users.

STIG ID: RHEL-08-010673 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the operating system disables core dumps for all users by issuing the following command:

$ sudo grep -r -s '^[^#].*core' /etc/security/limits.conf /etc/security/limits.d/*.conf

* hard core 0

This can be set as a global domain (with the * wildcard) but may be set differently for multiple domains.

If the "core" item is missing, commented out, or the value is anything other than "0" and the need for core dumps is not documented with the Information System Security Officer (ISSO) as an operational requirement for all domains that have the "core" item assigned, this is a finding.

Fix

Configure the operating system to disable core dumps for all users.

Add the following line to the top of the /etc/security/limits.conf or in a ".conf" file defined in /etc/security/limits.d/:

* hard core 0

RHEL 8 must disable storing core dumps.

STIG ID: RHEL-08-010674 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the operating system disables storing core dumps for all users by issuing the following command:

$ sudo grep -i storage /etc/systemd/coredump.conf

Storage=none

If the "Storage" item is missing, commented out, or the value is anything other than "none" and the need for core dumps is not documented with the Information System Security Officer (ISSO) as an operational requirement for all domains that have the "core" item assigned, this is a finding.

Fix

Configure the operating system to disable storing core dumps for all users.

Add or modify the following line in /etc/systemd/coredump.conf:

Storage=none

RHEL 8 must disable core dump backtraces.

STIG ID: RHEL-08-010675 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the operating system disables core dump backtraces by issuing the following command:

$ sudo grep -i ProcessSizeMax /etc/systemd/coredump.conf

ProcessSizeMax=0

If the "ProcessSizeMax" item is missing, commented out, or the value is anything other than "0" and the need for core dumps is not documented with the Information System Security Officer (ISSO) as an operational requirement for all domains that have the "core" item assigned, this is a finding.

Fix

Configure the operating system to disable core dump backtraces.

Add or modify the following line in /etc/systemd/coredump.conf:

ProcessSizeMax=0

For RHEL 8 systems using Domain Name Servers (DNS) resolution, at least two name servers must be configured.

STIG ID: RHEL-08-010680 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

To provide availability for name resolution services, multiple redundant name servers are mandated. A failure in name resolution could lead to the failure of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.

Check

Determine whether the system is using local or DNS name resolution with the following command:

$ sudo grep hosts /etc/nsswitch.conf

hosts: files dns

If the DNS entry is missing from the host's line in the "/etc/nsswitch.conf" file, the "/etc/resolv.conf" file must be empty.

Verify the "/etc/resolv.conf" file is empty with the following command:

$ sudo ls -al /etc/resolv.conf

-rw-r--r-- 1 root root 0 Aug 19 08:31 resolv.conf

If local host authentication is being used and the "/etc/resolv.conf" file is not empty, this is a finding.

If the DNS entry is found on the host's line of the "/etc/nsswitch.conf" file, verify the operating system is configured to use two or more name servers for DNS resolution.

Determine the name servers used by the system with the following command:

$ sudo grep nameserver /etc/resolv.conf

nameserver 192.168.1.2
nameserver 192.168.1.3

If less than two lines are returned that are not commented out, this is a finding.

Fix

Configure the operating system to use two or more name servers for DNS resolution.

By default, "NetworkManager" on RHEL 8 dynamically updates the /etc/resolv.conf file with the DNS settings from active "NetworkManager" connection profiles. However, this feature can be disabled to allow manual configurations.

If manually configuring DNS, edit the "/etc/resolv.conf" file to uncomment or add the two or more "nameserver" option lines with the IP address of local authoritative name servers. If local host resolution is being performed, the "/etc/resolv.conf" file must be empty. An empty "/etc/resolv.conf" file can be created as follows:

$ sudo echo -n > /etc/resolv.conf

Executable search paths within the initialization files of all local interactive RHEL 8 users must only contain paths that resolve to the system default or the users home directory.

STIG ID: RHEL-08-010690 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The executable search path (typically the PATH environment variable) contains a list of directories for the shell to search to find executables. If this path includes the current working directory (other than the user's home directory), executables in these directories may be executed instead of system commands. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon or two consecutive colons, this is interpreted as the current working directory. If deviations from the default system search path for the local interactive user are required, they must be documented with the Information System Security Officer (ISSO).

Check

Verify that all local interactive user initialization file executable search path statements do not contain statements that will reference a working directory other than user home directories with the following commands:

$ sudo grep -i path /home/*/.*

/home/[localinteractiveuser]/.bash_profile:PATH=$PATH:$HOME/.local/bin:$HOME/bin
/home/[localinteractiveuser]/.bash_profile:export PATH

If any local interactive user initialization files have executable search path statements that include directories outside of their home directory and is not documented with the ISSO as an operational requirement, this is a finding.

Fix

Edit the local interactive user initialization files to change any PATH variable statements that reference directories other than their home directory.

If a local interactive user requires path variables to reference a directory owned by the application, it must be documented with the ISSO.

All RHEL 8 world-writable directories must be owned by root, sys, bin, or an application group.

STIG ID: RHEL-08-010700 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If a world-writable directory has the sticky bit set and is not owned by root, sys, bin, or an application User Identifier (UID), unauthorized users may be able to modify files created by others.

The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage, (e.g., /tmp), and for directories requiring global read/write access.

Check

The following command will discover and print world-writable directories that are not owned by a system account, given the assumption that only system accounts have a uid lower than 1000. Run it once for each local partition [PART]:

$ sudo find [PART] -xdev -type d -perm -0002 -uid +999 -print

If there is output, this is a finding.

Fix

All directories in local partitions which are world-writable should be owned by root or another system account. If any world-writable directories are not owned by a system account, this should be investigated. Following this, the files should be deleted or assigned to an appropriate group.

All RHEL 8 world-writable directories must be group-owned by root, sys, bin, or an application group.

STIG ID: RHEL-08-010710 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If a world-writable directory has the sticky bit set and is not group-owned by root, sys, bin, or an application Group Identifier (GID), unauthorized users may be able to modify files created by others.

The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage, (e.g., /tmp), and for directories requiring global read/write access.

Check

The following command will discover and print world-writable directories that are not group-owned by a system account, given the assumption that only system accounts have a gid lower than 1000. Run it once for each local partition [PART]:

$ sudo find [PART] -xdev -type d -perm -0002 -gid +999 -print

If there is output, this is a finding.

Fix

All directories in local partitions which are world-writable must be group-owned by root or another system account. If any world-writable directories are not group-owned by a system account, this must be investigated. Following this, the directories must be deleted or assigned to an appropriate group.

All RHEL 8 local interactive users must have a home directory assigned in the /etc/passwd file.

STIG ID: RHEL-08-010720 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If local interactive users are not assigned a valid home directory, there is no place for the storage and control of files they should own.

Check

Verify local interactive users on RHEL 8 have a home directory assigned with the following command:

$ sudo pwck -r

user 'lp': directory '/var/spool/lpd' does not exist
user 'news': directory '/var/spool/news' does not exist
user 'uucp': directory '/var/spool/uucp' does not exist
user 'www-data': directory '/var/www' does not exist

Ask the System Administrator (SA) if any users found without home directories are local interactive users. If the SA is unable to provide a response, check for users with a User Identifier (UID) of 1000 or greater with the following command:

$ sudo awk -F: '($3>=1000)&&($7 !~ /nologin/){print $1, $3, $6}' /etc/passwd

If any interactive users do not have a home directory assigned, this is a finding.

Fix

Assign home directories to all local interactive users on RHEL 8 that currently do not have a home directory assigned.

All RHEL 8 local interactive user home directories must have mode 0750 or less permissive.

STIG ID: RHEL-08-010730 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Excessive permissions on local interactive user home directories may allow unauthorized access to user files by other users.

Check

Verify the assigned home directory of all local interactive users has a mode of "0750" or less permissive with the following command:

Note: This may miss interactive users that have been assigned a privileged User Identifier (UID). Evidence of interactive use may be obtained from a number of log files containing system logon information.

$ sudo ls -ld $(awk -F: '($3>=1000)&&($7 !~ /nologin/){print $6}' /etc/passwd)

drwxr-x--- 2 smithj admin 4096 Jun 5 12:41 smithj

If home directories referenced in "/etc/passwd" do not have a mode of "0750" or less permissive, this is a finding.

Fix

Change the mode of interactive user’s home directories to "0750". To change the mode of a local interactive user’s home directory, use the following command:

Note: The example will be for the user "smithj".

$ sudo chmod 0750 /home/smithj

All RHEL 8 local interactive user home directories must be group-owned by the home directory owner’s primary group.

STIG ID: RHEL-08-010740 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If the Group Identifier (GID) of a local interactive user’s home directory is not the same as the primary GID of the user, this would allow unauthorized access to the user’s files, and users that share the same group may not be able to access files that they legitimately should.

Check

Verify the assigned home directory of all local interactive users is group-owned by that user’s primary GID with the following command:

Note: This may miss local interactive users that have been assigned a privileged UID. Evidence of interactive use may be obtained from a number of log files containing system logon information. The returned directory "/home/smithj" is used as an example.

$ sudo ls -ld $(awk -F: '($3>=1000)&&($7 !~ /nologin/){print $6}' /etc/passwd)

drwxr-x--- 2 smithj admin 4096 Jun 5 12:41 smithj

Check the user's primary group with the following command:

$ sudo grep admin /etc/group

admin:x:250:smithj,jonesj,jacksons

If the user home directory referenced in "/etc/passwd" is not group-owned by that user’s primary GID, this is a finding.

Fix

Change the group owner of a local interactive user’s home directory to the group found in "/etc/passwd". To change the group owner of a local interactive user’s home directory, use the following command:

Note: The example will be for the user "smithj", who has a home directory of "/home/smithj", and has a primary group of users.

$ sudo chgrp users /home/smithj

All RHEL 8 local interactive user home directories defined in the /etc/passwd file must exist.

STIG ID: RHEL-08-010750 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If a local interactive user has a home directory defined that does not exist, the user may be given access to the "/" directory as the current working directory upon logon. This could create a denial of service because the user would not be able to access their logon configuration files, and it may give them visibility to system files they normally would not be able to access.

Check

Verify the assigned home directory of all local interactive users on RHEL 8 exists with the following command:

$ sudo ls -ld $(awk -F: '($3>=1000)&&($7 !~ /nologin/){print $6}' /etc/passwd)

drwxr-xr-x 2 smithj admin 4096 Jun 5 12:41 smithj

Note: This may miss interactive users that have been assigned a privileged User ID (UID). Evidence of interactive use may be obtained from a number of log files containing system logon information.

Check that all referenced home directories exist with the following command:

$ sudo pwck -r

user 'smithj': directory '/home/smithj' does not exist

If any home directories referenced in "/etc/passwd" are returned as not defined, this is a finding.

Fix

Create home directories to all local interactive users that currently do not have a home directory assigned. Use the following commands to create the user home directory assigned in "/etc/ passwd":

Note: The example will be for the user smithj, who has a home directory of "/home/smithj", a UID of "smithj", and a Group Identifier (GID) of "users assigned" in "/etc/passwd".

$ sudo mkdir /home/smithj
$ sudo chown smithj /home/smithj
$ sudo chgrp users /home/smithj
$ sudo chmod 0750 /home/smithj

All RHEL 8 local interactive user accounts must be assigned a home directory upon creation.

STIG ID: RHEL-08-010760 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If local interactive users are not assigned a valid home directory, there is no place for the storage and control of files they should own.

Check

Verify all local interactive users on RHEL 8 are assigned a home directory upon creation with the following command:

$ sudo grep -i create_home /etc/login.defs

CREATE_HOME yes

If the value for "CREATE_HOME" parameter is not set to "yes", the line is missing, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to assign home directories to all new local interactive users by setting the "CREATE_HOME" parameter in "/etc/login.defs" to "yes" as follows.

CREATE_HOME yes

All RHEL 8 local initialization files must have mode 0740 or less permissive.

STIG ID: RHEL-08-010770 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Local initialization files are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.

Check

Verify that all local initialization files have a mode of "0740" or less permissive with the following command:

Note: The example will be for the "smithj" user, who has a home directory of "/home/smithj".

$ sudo ls -al /home/smithj/.[^.]* | more

-rwxr-xr-x 1 smithj users 896 Mar 10 2011 .profile
-rwxr-xr-x 1 smithj users 497 Jan 6 2007 .login
-rwxr-xr-x 1 smithj users 886 Jan 6 2007 .something

If any local initialization files have a mode more permissive than "0740", this is a finding.

Fix

Set the mode of the local initialization files to "0740" with the following command:

Note: The example will be for the smithj user, who has a home directory of "/home/smithj".

$ sudo chmod 0740 /home/smithj/.

All RHEL 8 local files and directories must have a valid owner.

STIG ID: RHEL-08-010780 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Unowned files and directories may be unintentionally inherited if a user is assigned the same User Identifier "UID" as the UID of the un-owned files.

Check

Verify all local files and directories on RHEL 8 have a valid owner with the following command:

Note: The value after -fstype must be replaced with the filesystem type. XFS is used as an example.

$ sudo find / -fstype xfs -nouser

If any files on the system do not have an assigned owner, this is a finding.

Note: Command may produce error messages from the /proc and /sys directories.

Fix

Either remove all files and directories from the system that do not have a valid user, or assign a valid user to all unowned files and directories on RHEL 8 with the "chown" command:

$ sudo chown

All RHEL 8 local files and directories must have a valid group owner.

STIG ID: RHEL-08-010790 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Files without a valid group owner may be unintentionally inherited if a group is assigned the same Group Identifier (GID) as the GID of the files without a valid group owner.

Check

Verify all local files and directories on RHEL 8 have a valid group with the following command:

Note: The value after -fstype must be replaced with the filesystem type. XFS is used as an example.

$ sudo find / -fstype xfs -nogroup

If any files on the system do not have an assigned group, this is a finding.

Note: Command may produce error messages from the /proc and /sys directories.

Fix

Either remove all files and directories from RHEL 8 that do not have a valid group, or assign a valid group to all files and directories on the system with the "chgrp" command:

$ sudo chgrp

A separate RHEL 8 filesystem must be used for user home directories (such as /home or an equivalent).

STIG ID: RHEL-08-010800 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.

Check

Verify that a separate file system/partition has been created for non-privileged local interactive user home directories.

Check the home directory assignment for all non-privileged users, users with a User Identifier (UID) greater than 1000, on the system with the following command:

$ sudo awk -F: '($3>=1000)&&($7 !~ /nologin/){print $1,$3,$6}' /etc/passwd

adamsj 1001 /home/adamsj
jacksonm 1002 /home/jacksonm
smithj 1003 /home/smithj

The output of the command will give the directory/partition that contains the home directories for the non-privileged users on the system (in this example, "/home") and users’ shell. All accounts with a valid shell (such as /bin/bash) are considered interactive users.

Check that a file system/partition has been created for the non-privileged interactive users with the following command:

Note: The partition of "/home" is used in the example.

$ sudo grep /home /etc/fstab

UUID=333ada18 /home ext4 noatime,nobarrier,nodev 1 2

If a separate entry for the file system/partition containing the non-privileged interactive user home directories does not exist, this is a finding.

Fix

Migrate the "/home" directory onto a separate file system/partition.

Unattended or automatic logon via the RHEL 8 graphical user interface must not be allowed.

STIG ID: RHEL-08-010820 | SRG: SRG-OS-000480-GPOS-00229 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

Failure to restrict system access to authenticated users negatively impacts operating system security.

Check

Verify the operating system does not allow an unattended or automatic logon to the system via a graphical user interface.

Note: This requirement assumes the use of the RHEL 8 default graphical user interface, Gnome Shell. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

Check for the value of the "AutomaticLoginEnable" in the "/etc/gdm/custom.conf" file with the following command:

$ sudo grep -i automaticloginenable /etc/gdm/custom.conf

AutomaticLoginEnable=false

If the value of "AutomaticLoginEnable" is not set to "false", this is a finding.

Fix

Configure the operating system to not allow an unattended or automatic logon to the system via a graphical user interface.

Add or edit the line for the "AutomaticLoginEnable" parameter in the [daemon] section of the "/etc/gdm/custom.conf" file to "false":

[daemon]
AutomaticLoginEnable=false

RHEL 8 must not allow users to override SSH environment variables.

STIG ID: RHEL-08-010830 | SRG: SRG-OS-000480-GPOS-00229 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

SSH environment options potentially allow users to bypass access restriction in some configurations.

Check

Verify that unattended or automatic logon via ssh is disabled with the following command:

$ sudo grep -i PermitUserEnvironment /etc/ssh/sshd_config

PermitUserEnvironment no

If "PermitUserEnvironment" is set to "yes", is missing completely, or is commented out, this is a finding.

Fix

Configure RHEL 8 to allow the SSH daemon to not allow unattended or automatic logon to the system.

Add or edit the following line in the "/etc/ssh/sshd_config" file:

PermitUserEnvironment no

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

RHEL 8 temporary user accounts must be provisioned with an expiration time of 72 hours or less.

STIG ID: RHEL-08-020000 | SRG: SRG-OS-000002-GPOS-00002 | Severity: medium | CCI: CCI-000016

Vulnerability Discussion

If temporary user accounts remain active when no longer needed or for an excessive period, these accounts may be used to gain unauthorized access. To mitigate this risk, automated termination of all temporary accounts must be set upon account creation.

Temporary accounts are established as part of normal account activation procedures when there is a need for short-term accounts without the demand for immediacy in account activation.

If temporary accounts are used, RHEL 8 must be configured to automatically terminate these types of accounts after a DoD-defined time period of 72 hours.

To address access requirements, many RHEL 8 operating systems may be integrated with enterprise-level authentication/access mechanisms that meet or exceed access control policy requirements.

Check

Verify that temporary accounts have been provisioned with an expiration date of 72 hours.

For every existing temporary account, run the following command to obtain its account expiration information.

$ sudo chage -l system_account_name

Verify each of these accounts has an expiration date set within 72 hours.

If any temporary accounts have no expiration date set or do not expire within 72 hours, this is a finding.

Fix

If a temporary account must be created configure the system to terminate the account after a 72 hour time period with the following command to set an expiration date on it. Substitute "system_account_name" with the account to be created.

$ sudo chage -E `date -d "+3 days" +%Y-%m-%d` system_account_name

RHEL 8 must automatically lock an account when three unsuccessful logon attempts occur.

STIG ID: RHEL-08-020010 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system locks an account after three unsuccessful logon attempts with the following commands:

Note: If the System Administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

Note: This check applies to RHEL versions 8.0 and 8.1, if the system is RHEL version 8.2 or newer, this check is not applicable.

$ sudo grep pam_faillock.so /etc/pam.d/password-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "deny" option is not set to "3" or less (but not "0") on the "preauth" line with the "pam_faillock.so" module, or is missing from this line, this is a finding.

If any line referencing the "pam_faillock.so" module is commented out, this is a finding.

$ sudo grep pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "deny" option is not set to "3" or less (but not "0") on the "preauth" line with the "pam_faillock.so" module, or is missing from this line, this is a finding.

If any line referencing the "pam_faillock.so" module is commented out, this is a finding.

Fix

Configure the operating system to lock an account when three unsuccessful logon attempts occur.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must automatically lock an account when three unsuccessful logon attempts occur.

STIG ID: RHEL-08-020011 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-force attacks, is reduced. Limits are imposed by locking the account.

In RHEL 8.2 the "/etc/security/faillock.conf" file was incorporated to centralize the configuration of the pam_faillock.so module. Also introduced is a "local_users_only" option that will only track failed user authentication attempts for local users in /etc/passwd and ignore centralized (AD, IdM, LDAP, etc.) users to allow the centralized platform to solely manage user lockout.

From "faillock.conf" man pages: Note that the default directory that "pam_faillock" uses is usually cleared on system boot so the access will be reenabled after system reboot. If that is undesirable a different tally directory must be set with the "dir" option.

Satisfies: SRG-OS-000021-GPOS-00005, SRG-OS-000329-GPOS-00128

Check

Check that the system locks an account after three unsuccessful logon attempts with the following commands:

Note: This check applies to RHEL versions 8.2 or newer, if the system is RHEL version 8.0 or 8.1, this check is not applicable.

Verify the pam_faillock.so module is present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files:

$ sudo grep pam_faillock.so /etc/pam.d/system-auth /etc/pam.d/password-auth

/etc/pam.d/system-auth:auth required pam_faillock.so preauth
/etc/pam.d/system-auth:auth required pam_faillock.so authfail
/etc/pam.d/system-auth:account required pam_faillock.so
/etc/pam.d/password-auth:auth required pam_faillock.so preauth
/etc/pam.d/password-auth:auth required pam_faillock.so authfail
/etc/pam.d/password-auth:account required pam_faillock.so preauth

If the pam_failllock.so module is not present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files, this is a finding.

Verify the "/etc/security/faillock.conf" file is configured to lock an account after three unsuccessful logon attempts:

$ sudo grep 'deny =' /etc/security/faillock.conf

deny = 3

If the "deny" option is not set to "3" or less (but not "0"), is missing or commented out, this is a finding.

Fix

RHEL 8 must automatically lock an account when three unsuccessful logon attempts occur during a 15-minute time period.

STIG ID: RHEL-08-020012 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system locks an account after three unsuccessful logon attempts within a period of 15 minutes with the following commands:

Note: If the System Administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

Note: This check applies to RHEL versions 8.0 and 8.1, if the system is RHEL version 8.2 or newer, this check is not applicable.

$ sudo grep pam_faillock.so /etc/pam.d/password-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "fail_interval" option is not set to "900" or less (but not "0") on the "preauth" lines with the "pam_faillock.so" module, or is missing from this line, this is a finding.

$ sudo grep pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "fail_interval" option is not set to "900" or less (but not "0") on the "preauth" lines with the "pam_faillock.so" module, or is missing from this line, this is a finding.

Fix

Configure the operating system to lock an account when three unsuccessful logon attempts occur in 15 minutes.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must automatically lock an account when three unsuccessful logon attempts occur during a 15-minute time period.

STIG ID: RHEL-08-020013 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system locks an account after three unsuccessful logon attempts within a period of 15 minutes with the following commands:

Note: This check applies to RHEL versions 8.2 or newer, if the system is RHEL version 8.0 or 8.1, this check is not applicable.

Verify the pam_faillock.so module is present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files:

$ sudo grep pam_faillock.so /etc/pam.d/system-auth /etc/pam.d/password-auth

/etc/pam.d/system-auth:auth required pam_faillock.so preauth
/etc/pam.d/system-auth:auth required pam_faillock.so authfail
/etc/pam.d/system-auth:account required pam_faillock.so
/etc/pam.d/password-auth:auth required pam_faillock.so preauth
/etc/pam.d/password-auth:auth required pam_faillock.so authfail
/etc/pam.d/password-auth:account required pam_faillock.so preauth

If the pam_failllock.so module is not present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files, this is a finding.

Verify the "/etc/security/faillock.conf" file is configured to lock an account after three unsuccessful logon attempts within 15 minutes:

$ sudo grep 'fail_interval =' /etc/security/faillock.conf

fail_interval = 900

If the "fail_interval" option is not set to "900" or less (but not "0"), is missing or commented out, this is a finding.

Fix

Configure the operating system to lock an account when three unsuccessful logon attempts occur in 15 minutes.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth
auth required pam_faillock.so authfail
account required pam_faillock.so

Add/Modify the "/etc/security/faillock.conf" file to match the following line:

fail_interval = 900

RHEL 8 must automatically lock an account until the locked account is released by an administrator when three unsuccessful logon attempts occur during a 15-minute time period.

STIG ID: RHEL-08-020014 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system locks an account after three unsuccessful logon attempts within a period of 15 minutes until released by an administrator with the following commands:

Note: If the System Administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

Note: This check applies to RHEL versions 8.0 and 8.1, if the system is RHEL version 8.2 or newer, this check is not applicable.

$ sudo grep pam_faillock.so /etc/pam.d/password-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "unlock_time" option is not set to "0" on the "preauth" and "authfail" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

$ sudo grep pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "unlock_time" option is not set to "0" on the "preauth" and "authfail" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

Fix

Configure the operating system to lock an account until released by an administrator when three unsuccessful logon attempts occur in 15 minutes.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must automatically lock an account until the locked account is released by an administrator when three unsuccessful logon attempts occur during a 15-minute time period.

STIG ID: RHEL-08-020015 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system locks an account after three unsuccessful logon attempts within a period of 15 minutes until released by an administrator with the following commands:

Note: This check applies to RHEL versions 8.2 or newer, if the system is RHEL version 8.0 or 8.1, this check is not applicable.

Verify the pam_faillock.so module is present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files:

$ sudo grep pam_faillock.so /etc/pam.d/system-auth /etc/pam.d/password-auth

/etc/pam.d/system-auth:auth required pam_faillock.so preauth
/etc/pam.d/system-auth:auth required pam_faillock.so authfail
/etc/pam.d/system-auth:account required pam_faillock.so
/etc/pam.d/password-auth:auth required pam_faillock.so preauth
/etc/pam.d/password-auth:auth required pam_faillock.so authfail
/etc/pam.d/password-auth:account required pam_faillock.so preauth

If the pam_failllock.so module is not present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files, this is a finding.

Verify the "/etc/security/faillock.conf" file is configured to lock an account until released by an administrator after three unsuccessful logon attempts:

$ sudo grep 'unlock_time =' /etc/security/faillock.conf

unlock_time = 0

If the "unlock_time" option is not set to "0", is missing or commented out, this is a finding.

Fix

Configure the operating system to lock an account until released by an administrator when three unsuccessful logon attempts occur in 15 minutes.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth
auth required pam_faillock.so authfail
account required pam_faillock.so

Add/Modify the "/etc/security/faillock.conf" file to match the following line:

unlock_time = 0

RHEL 8 must ensure account lockouts persist.

STIG ID: RHEL-08-020016 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the faillock directory contents persists after a reboot with the following commands:

Note: If the System Administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

Note: This check applies to RHEL versions 8.0 and 8.1, if the system is RHEL version 8.2 or newer, this check is not applicable.

$ sudo grep pam_faillock.so /etc/pam.d/password-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "dir" option is not set to a non-default documented tally log directory on the "preauth" and "authfail" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

$ sudo grep pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "dir" option is not set to a non-default documented tally log directory on the "preauth" and "authfail" lines with the "pam_faillock.so" module, or is missing from these lines, this is a finding.

Fix

Configure the operating system maintain the contents of the faillock directory after a reboot.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

Note: Using the default faillock directory of /var/run/faillock will result in the contents being cleared in the event of a reboot.

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must ensure account lockouts persist.

STIG ID: RHEL-08-020017 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the faillock directory contents persist after a reboot with the following commands:

Note: This check applies to RHEL versions 8.2 or newer. If the system is RHEL version 8.0 or 8.1, this check is not applicable.

Verify the pam_faillock.so module is present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files:

$ sudo grep pam_faillock.so /etc/pam.d/system-auth /etc/pam.d/password-auth

/etc/pam.d/system-auth:auth required pam_faillock.so preauth
/etc/pam.d/system-auth:auth required pam_faillock.so authfail
/etc/pam.d/system-auth:account required pam_faillock.so
/etc/pam.d/password-auth:auth required pam_faillock.so preauth
/etc/pam.d/password-auth:auth required pam_faillock.so authfail
/etc/pam.d/password-auth:account required pam_faillock.so preauth

If the pam_failllock.so module is not present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files, this is a finding.

Verify the "/etc/security/faillock.conf" file is configured use a non-default faillock directory to ensure contents persist after reboot:

$ sudo grep 'dir =' /etc/security/faillock.conf

dir = /var/log/faillock

If the "dir" option is not set to a non-default documented tally log directory, is missing or commented out, this is a finding.

Fix

RHEL 8 must prevent system messages from being presented when three unsuccessful logon attempts occur.

STIG ID: RHEL-08-020018 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system prevents informative messages from being presented to the user pertaining to logon information with the following commands:

Note: If the System Administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

Note: This check applies to RHEL versions 8.0 and 8.1, if the system is RHEL version 8.2 or newer, this check is not applicable.

$ sudo grep pam_faillock.so /etc/pam.d/password-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "silent" option is missing from the "preauth" line with the "pam_faillock.so" module, this is a finding.

$ sudo grep pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "silent" option is missing from the "preauth" line with the "pam_faillock.so" module, this is a finding.

Fix

Configure the operating system to prevent informative messages from being presented at logon attempts.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must prevent system messages from being presented when three unsuccessful logon attempts occur.

STIG ID: RHEL-08-020019 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system prevents informative messages from being presented to the user pertaining to logon information with the following commands:

Note: This check applies to RHEL versions 8.2 or newer, if the system is RHEL version 8.0 or 8.1, this check is not applicable.

Verify the pam_faillock.so module is present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files:

$ sudo grep pam_faillock.so /etc/pam.d/system-auth /etc/pam.d/password-auth

/etc/pam.d/system-auth:auth required pam_faillock.so preauth
/etc/pam.d/system-auth:auth required pam_faillock.so authfail
/etc/pam.d/system-auth:account required pam_faillock.so
/etc/pam.d/password-auth:auth required pam_faillock.so preauth
/etc/pam.d/password-auth:auth required pam_faillock.so authfail
/etc/pam.d/password-auth:account required pam_faillock.so preauth

If the pam_failllock.so module is not present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files, this is a finding.

Verify the "/etc/security/faillock.conf" file is configured to prevent informative messages from being presented at logon attempts:

$ sudo grep silent /etc/security/faillock.conf

silent

If the "silent" option is not set, is missing or commented out, this is a finding.

Fix

RHEL 8 must log user name information when unsuccessful logon attempts occur.

STIG ID: RHEL-08-020020 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-force attacks, is reduced. Limits are imposed by locking the account.

RHEL 8 can utilize the "pam_faillock.so" for this purpose. Note that manual changes to the listed files may be overwritten by the "authselect" program.

From "Pam_Faillock" man pages: Note that the default directory that "pam_faillock" uses is usually cleared on system boot so the access will be reenabled after system reboot. If that is undesirable a different tally directory must be set with the "dir" option.

In RHEL 8.2 the "/etc/security/faillock.conf" file was incorporated to centralize the configuration of the pam_faillock.so module. Also introduced is a "local_users_only" option that will only track failed user authentication attempts for local users in /etc/passwd and ignore centralized (AD, IdM, LDAP, etc.) users to allow the centralized platform to solely manage user lockout.

Satisfies: SRG-OS-000021-GPOS-00005, SRG-OS-000329-GPOS-00128

Check

Check that the system logs user name information when unsuccessful logon attempts occur with the following commands:

If the system is RHEL version 8.2 or newer, this check is not applicable.

Note: If the System Administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

$ sudo grep pam_faillock.so /etc/pam.d/password-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "audit" option is missing from the "preauth" line with the "pam_faillock.so" module, this is a finding.

$ sudo grep pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "audit" option is missing from the "preauth" line with the "pam_faillock.so" module, this is a finding.

Fix

Configure the operating system to log user name information when unsuccessful logon attempts occur.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must log user name information when unsuccessful logon attempts occur.

STIG ID: RHEL-08-020021 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system logs user name information when unsuccessful logon attempts occur with the following commands:

Note: This check applies to RHEL versions 8.2 or newer, if the system is RHEL version 8.0 or 8.1, this check is not applicable.

Verify the pam_faillock.so module is present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files:

$ sudo grep pam_faillock.so /etc/pam.d/system-auth /etc/pam.d/password-auth

/etc/pam.d/system-auth:auth required pam_faillock.so preauth
/etc/pam.d/system-auth:auth required pam_faillock.so authfail
/etc/pam.d/system-auth:account required pam_faillock.so
/etc/pam.d/password-auth:auth required pam_faillock.so preauth
/etc/pam.d/password-auth:auth required pam_faillock.so authfail
/etc/pam.d/password-auth:account required pam_faillock.so preauth

If the pam_failllock.so module is not present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files, this is a finding.

Verify the "/etc/security/faillock.conf" file is configured to log user name information when unsuccessful logon attempts occur:

$ sudo grep audit /etc/security/faillock.conf

audit

If the "audit" option is not set, is missing or commented out, this is a finding.

Fix

RHEL 8 must include root when automatically locking an account until the locked account is released by an administrator when three unsuccessful logon attempts occur during a 15-minute time period.

STIG ID: RHEL-08-020022 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-force attacks, is reduced. Limits are imposed by locking the account.

RHEL 8 can utilize the "pam_faillock.so" for this purpose. Note that manual changes to the listed files may be overwritten by the "authselect" program.

From "Pam_Faillock" man pages: Note that the default directory that "pam_faillock" uses is usually cleared on system boot so the access will be reenabled after system reboot. If that is undesirable a different tally directory must be set with the "dir" option.

In RHEL 8.2 the "/etc/security/faillock.conf" file was incorporated to centralize the configuration of the pam_faillock.so module. Also introduced is a "local_users_only" option that will only track failed user authentication attempts for local users in /etc/passwd and ignore centralized (AD, IdM, LDAP, etc.) users to allow the centralized platform to solely manage user lockout.

Satisfies: SRG-OS-000021-GPOS-00005, SRG-OS-000329-GPOS-00128

Check

Check that the system includes the root account when locking an account after three unsuccessful logon attempts within a period of 15 minutes with the following commands:

If the system is RHEL version 8.2 or newer, this check is not applicable.

Note: If the System Administrator demonstrates the use of an approved centralized account management method that locks an account after three unsuccessful logon attempts within a period of 15 minutes, this requirement is not applicable.

$ sudo grep pam_faillock.so /etc/pam.d/password-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "even_deny_root" option is missing from the "preauth" line with the "pam_faillock.so" module, this is a finding.

$ sudo grep pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

If the "even_deny_root" option is missing from the "preauth" line with the "pam_faillock.so" module, this is a finding.

Fix

Configure the operating system to include root when locking an account after three unsuccessful logon attempts occur in 15 minutes.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth dir=/var/log/faillock silent audit deny=3 even_deny_root fail_interval=900 unlock_time=0
auth required pam_faillock.so authfail dir=/var/log/faillock unlock_time=0
account required pam_faillock.so

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must include root when automatically locking an account until the locked account is released by an administrator when three unsuccessful logon attempts occur during a 15-minute time period.

STIG ID: RHEL-08-020023 | SRG: SRG-OS-000021-GPOS-00005 | Severity: medium | CCI: CCI-000044

Vulnerability Discussion

Check

Check that the system includes the root account when locking an account after three unsuccessful logon attempts within a period of 15 minutes with the following commands:

Note: This check applies to RHEL versions 8.2 or newer, if the system is RHEL version 8.0 or 8.1, this check is not applicable.

Verify the pam_faillock.so module is present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files:

$ sudo grep pam_faillock.so /etc/pam.d/system-auth /etc/pam.d/password-auth

/etc/pam.d/system-auth:auth required pam_faillock.so preauth
/etc/pam.d/system-auth:auth required pam_faillock.so authfail
/etc/pam.d/system-auth:account required pam_faillock.so
/etc/pam.d/password-auth:auth required pam_faillock.so preauth
/etc/pam.d/password-auth:auth required pam_faillock.so authfail
/etc/pam.d/password-auth:account required pam_faillock.so preauth

If the pam_failllock.so module is not present in the "/etc/pam.d/system-auth" and " /etc/pam.d/password-auth" files, this is a finding.

Verify the "/etc/security/faillock.conf" file is configured to log user name information when unsuccessful logon attempts occur:

$ sudo grep even_deny_root /etc/security/faillock.conf

even_deny_root

If the "even_deny_root" option is not set, is missing or commented out, this is a finding.

Fix

Configure the operating system to include root when locking an account after three unsuccessful logon attempts occur in 15 minutes.

Add/Modify the appropriate sections of the "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" files to match the following lines:

auth required pam_faillock.so preauth
auth required pam_faillock.so authfail
account required pam_faillock.so

Add/Modify the "/etc/security/faillock.conf" file to match the following line:

even_deny_root

RHEL 8 must limit the number of concurrent sessions to ten for all accounts and/or account types.

STIG ID: RHEL-08-020024 | SRG: SRG-OS-000027-GPOS-00008 | Severity: low | CCI: CCI-000054

Vulnerability Discussion

Operating system management includes the ability to control the number of users and user sessions that utilize an operating system. Limiting the number of allowed users and sessions per user is helpful in reducing the risks related to DoS attacks.

This requirement addresses concurrent sessions for information system accounts and does not address concurrent sessions by single users via multiple system accounts. The maximum number of concurrent sessions should be defined based on mission needs and the operational environment for each system.

Check

Verify the operating system limits the number of concurrent sessions to "10" for all accounts and/or account types by issuing the following command:

$ sudo grep -r -s '^[^#].*maxlogins' /etc/security/limits.conf /etc/security/limits.d/*.conf

* hard maxlogins 10

This can be set as a global domain (with the * wildcard) but may be set differently for multiple domains.

If the "maxlogins" item is missing, commented out, or the value is set greater than "10" and is not documented with the Information System Security Officer (ISSO) as an operational requirement for all domains that have the "maxlogins" item assigned, this is a finding.

Fix

Configure the operating system to limit the number of concurrent sessions to "10" for all accounts and/or account types.

Add the following line to the top of the /etc/security/limits.conf or in a ".conf" file defined in /etc/security/limits.d/:

* hard maxlogins 10

RHEL 8 must enable a user session lock until that user re-establishes access using established identification and authentication procedures for graphical user sessions.

STIG ID: RHEL-08-020030 | SRG: SRG-OS-000028-GPOS-00009 | Severity: medium | CCI: CCI-000056

Vulnerability Discussion

Check

Verify the operating system enables a user's session lock until that user re-establishes access using established identification and authentication procedures with the following command:

$ sudo gsettings get org.gnome.desktop.screensaver lock-enabled

true

If the setting is "false", this is a finding.

Note: This requirement assumes the use of the RHEL 8 default graphical user interface, Gnome Shell. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

Fix

Configure the operating system to enable a user's session lock until that user re-establishes access using established identification and authentication procedures.

Create a database to contain the system-wide screensaver settings (if it does not already exist) with the following example:

$ sudo vi /etc/dconf/db/local.d/00-screensaver

Edit the "[org/gnome/desktop/screensaver]" section of the database file and add or update the following lines:

# Set this to true to lock the screen when the screensaver activates
lock-enabled=true

Update the system databases:

$ sudo dconf update

RHEL 8 must enable a user session lock until that user re-establishes access using established identification and authentication procedures for command line sessions.

STIG ID: RHEL-08-020040 | SRG: SRG-OS-000028-GPOS-00009 | Severity: medium | CCI: CCI-000056

Vulnerability Discussion

A session lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not want to log out because of the temporary nature of the absence.

The session lock is implemented at the point where session activity can be determined. Rather than be forced to wait for a period of time to expire before the user session can be locked, RHEL 8 needs to provide users with the ability to manually invoke a session lock so users can secure their session if it is necessary to temporarily vacate the immediate physical vicinity.

Tmux is a terminal multiplexer that enables a number of terminals to be created, accessed, and controlled from a single screen. Red Hat endorses tmux as the recommended session controlling package.

Satisfies: SRG-OS-000028-GPOS-00009, SRG-OS-000030-GPOS-00011

Check

Verify the operating system enables the user to initiate a session lock on command.

Verify RHEL 8 has the "tmux" package installed, by running the following command:

$ sudo yum list installed tmux

tmux.x86.64 2.7-1.el8 @repository

If "tmux" is not installed, this is a finding.

Next verify that the lock-command is set in the global settings of tmux with the following command:

$ sudo grep -i lock-command /etc/tmux.conf

set -g lock-command vlock

If the "lock-command" is not set in the global settings to call "vlock", this is a finding.

Fix

Configure the operating system to enable a user to initiate a session lock via tmux.

Install the "tmux" package, if it is not already installed, by running the following command:

$ sudo yum install tmux

Once installed, create a global configuration file "/etc/tmux.conf" and add the following line:

set -g lock-command vlock

RHEL 8 must ensure session control is automatically started at shell initialization.

STIG ID: RHEL-08-020041 | SRG: SRG-OS-000028-GPOS-00009 | Severity: medium | CCI: CCI-000056

Vulnerability Discussion

Check

Verify the operating system shell initialization file is configured to start each shell with the tmux terminal multiplexer with the following command:

$ sudo grep -i tmux /etc/bashrc

[ -n "$PS1" -a -z "$TMUX" ] && exec tmux

If "tmux" is not configured as the example above, is commented out, or missing from the "/etc/bashrc" initialization file, this is a finding.

Fix

Configure the operating system to initialize the tmux terminal multiplexer as each shell is called by adding the following line to the end of the "/etc/bashrc" configuration file:

[ -n "$PS1" -a -z "$TMUX" ] && exec tmux

This setting will take effect at next logon.

RHEL 8 must prevent users from disabling session control mechanisms.

STIG ID: RHEL-08-020042 | SRG: SRG-OS-000028-GPOS-00009 | Severity: low | CCI: CCI-000056

Vulnerability Discussion

Check

Verify the operating system prevents users from disabling the tmux terminal multiplexer with the following command:

$ sudo grep -i tmux /etc/shells

If any output is produced, this is a finding.

Fix

Configure the operating system to prevent users from disabling the tmux terminal multiplexer by editing the "/etc/shells" configuration file to remove any instances of tmux.

RHEL 8 must be able to initiate directly a session lock for all connection types using smartcard when the smartcard is removed.

STIG ID: RHEL-08-020050 | SRG: SRG-OS-000028-GPOS-00009 | Severity: medium | CCI: CCI-000056

Vulnerability Discussion

Check

Verify the operating system enables a user's session lock until that user re-establishes access using established identification and authentication procedures with the following command:

$ sudo grep -R removal-action /etc/dconf/db/*

/etc/dconf/db/distro.d/20-authselect:removal-action='lock-screen'

If the "removal-action='lock-screen'" setting is missing or commented out from the dconf database files, this is a finding.

Fix

Configure the operating system to enable a user's session lock until that user re-establishes access using established identification and authentication procedures.

Select/Create an authselect profile and incorporate the "with-smartcard-lock-on-removal" feature with the following example:

$ sudo authselect select sssd with-smartcard with-smartcard-lock-on-removal

Alternatively, the dconf settings can be edited in the /etc/dconf/db/* location.

Edit or add the "[org/gnome/settings-daemon/peripherals/smartcard]" section of the database file and add or update the following lines:

removal-action='lock-screen'

Update the system databases:

$ sudo dconf update

RHEL 8 must automatically lock graphical user sessions after 15 minutes of inactivity.

STIG ID: RHEL-08-020060 | SRG: SRG-OS-000029-GPOS-00010 | Severity: medium | CCI: CCI-000057

Vulnerability Discussion

A session lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not want to log out because of the temporary nature of the absence.

The session lock is implemented at the point where session activity can be determined. Rather than be forced to wait for a period of time to expire before the user session can be locked, RHEL 8 needs to provide users with the ability to manually invoke a session lock so users can secure their session if it is necessary to temporarily vacate the immediate physical vicinity.

Satisfies: SRG-OS-000029-GPOS-00010, SRG-OS-000031-GPOS-00012

Check

Verify the operating system initiates a session lock after a 15-minute period of inactivity for graphical user interfaces with the following commands:

This requirement assumes the use of the RHEL 8 default graphical user interface, Gnome Shell. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

$ sudo gsettings get org.gnome.desktop.session idle-delay

uint32 900

If "idle-delay" is set to "0" or a value greater than "900", this is a finding.

Fix

Configure the operating system to initiate a screensaver after a 15-minute period of inactivity for graphical user interfaces.

Create a database to contain the system-wide screensaver settings (if it does not already exist) with the following command:

$ sudo touch /etc/dconf/db/local.d/00-screensaver

Edit /etc/dconf/db/local.d/00-screensaver and add or update the following lines:

[org/gnome/desktop/session]
# Set the lock time out to 900 seconds before the session is considered idle
idle-delay=uint32 900

Update the system databases:

$ sudo dconf update

RHEL 8 must automatically lock command line user sessions after 15 minutes of inactivity.

STIG ID: RHEL-08-020070 | SRG: SRG-OS-000029-GPOS-00010 | Severity: medium | CCI: CCI-000057

Vulnerability Discussion

Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle session will also free up resources committed by the managed network element.

Terminating network connections associated with communications sessions includes, for example, de-allocating associated TCP/IP address/port pairs at the operating system level and de-allocating networking assignments at the application level if multiple application sessions are using a single operating system-level network connection. This does not mean the operating system terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

Satisfies: SRG-OS-000029-GPOS-00010, SRG-OS-000031-GPOS-00012

Check

Verify the operating system initiates a session lock after 15 minutes of inactivity.

Check the value of the system inactivity timeout with the following command:

$ sudo grep -i lock-after-time /etc/tmux.conf

set -g lock-after-time 900

If "lock-after-time" is not set to "900" or less in the global tmux configuration file to enforce session lock after inactivity, this is a finding.

Fix

Configure the operating system to enforce session lock after a period of 15 minutes of inactivity by adding the following line to the "/etc/tmux.conf" global configuration file:

set -g lock-after-time 900

RHEL 8 must prevent a user from overriding graphical user interface settings.

STIG ID: RHEL-08-020080 | SRG: SRG-OS-000029-GPOS-00010 | Severity: medium | CCI: CCI-000057

Vulnerability Discussion

A session time-out lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not log out because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, operating systems need to be able to identify when a user's session has idled and take action to initiate the session lock.

The session lock is implemented at the point where session activity can be determined and/or controlled.

Implementing session settings will have little value if a user is able to manipulate these settings from the defaults prescribed in the other requirements of this implementation guide.

Locking these settings from non-privileged users is crucial to maintaining a protected baseline.

Satisfies: SRG-OS-000029-GPOS-00010, SRG-OS-000031-GPOS-00012, SRG-OS-000480-GPOS-00227

Check

Verify the operating system prevents a user from overriding graphical user interfaces.

Note: This requirement assumes the use of the RHEL 8 default graphical user interface, Gnome Shell. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

Determine which profile the system database is using with the following command:

$ sudo grep system-db /etc/dconf/profile/user

system-db:local

Check that graphical settings are locked from non-privileged user modification with the following command:

Note: The example below is using the database "local" for the system, so the path is "/etc/dconf/db/local.d". This path must be modified if a database other than "local" is being used.

$ sudo grep -i 'idle\|lock\|log\|user\|banner' /etc/dconf/db/local.d/locks/*

/org/gnome/desktop/session/idle-delay
/org/gnome/desktop/screensaver/lock-enabled
/org/gnome/desktop/screensaver/lock-delay
/org/gnome/settings-daemon/plugins/media-keys/logout
/org/gnome/login-screen/disable-user-list
/org/gnome/login-screen/banner-message-text
/org/gnome/login-screen/banner-message-enable
/org/gnome/desktop/lockdown/disable-lock-screen

If the command does not return at least the example result, this is a finding.

Fix

Configure the operating system to prevent a user from overriding settings for graphical user interfaces.

Create a database to contain the system-wide screensaver settings (if it does not already exist) with the following command:

Note: The example below is using the database "local" for the system, so if the system is using another database in "/etc/dconf/profile/user", the file should be created under the appropriate subdirectory.

$ sudo touch /etc/dconf/db/local.d/locks/session

Add the following settings to prevent non-privileged users from modifying them:

/org/gnome/desktop/session/idle-delay
/org/gnome/desktop/screensaver/lock-enabled
/org/gnome/desktop/screensaver/lock-delay
/org/gnome/settings-daemon/plugins/media-keys/logout
/org/gnome/login-screen/disable-user-list
/org/gnome/login-screen/banner-message-text
/org/gnome/login-screen/banner-message-enable
/org/gnome/desktop/lockdown/disable-lock-screen

RHEL 8 must map the authenticated identity to the user or group account for PKI-based authentication.

STIG ID: RHEL-08-020090 | SRG: SRG-OS-000068-GPOS-00036 | Severity: medium | CCI: CCI-000187

Vulnerability Discussion

Without mapping the certificate used to authenticate to the user account, the ability to determine the identity of the individual user or group will not be available for forensic analysis.

There are various methods of mapping certificates to user/group accounts for RHEL 8. For the purposes of this requirement, the check and fix will account for Active Directory mapping. Some of the other possible methods include joining the system to a domain and utilizing a Red Hat idM server, or a local system mapping, where the system is not part of a domain.

Check

Verify the certificate of the user or group is mapped to the corresponding user or group in the "sssd.conf" file with the following command:

$ sudo cat /etc/sssd/sssd.conf

[sssd]
config_file_version = 2
services = pam, sudo, ssh
domains = testing.test

[pam]
pam_cert_auth = True

[domain/testing.test]
id_provider = ldap

[certmap/testing.test/rule_name]
matchrule =.*EDIPI@mil
maprule = (userCertificate;binary={cert!bin})
domains = testing.test

If the certmap section does not exist, ask the System Administrator to indicate how certificates are mapped to accounts. If there is no evidence of certificate mapping, this is a finding.

Fix

Configure the operating system to map the authenticated identity to the user or group account by adding or modifying the certmap section of the "/etc/sssd/sssd.conf file based on the following example:

[certmap/testing.test/rule_name]
matchrule =.*EDIPI@mil
maprule = (userCertificate;binary={cert!bin})
dmains = testing.test

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 must ensure a password complexity module is enabled.

STIG ID: RHEL-08-020100 | SRG: SRG-OS-000069-GPOS-00037 | Severity: medium | CCI: CCI-000192

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. "pwquality" enforces complex password construction configuration and has the ability to limit brute-force attacks on the system.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. This is set in both:
/etc/pam.d/password-auth
/etc/pam.d/system-auth

Note the value of "retry" set in these configuration files should be between "1" and "3". Manual changes to the listed files may be overwritten by the "authselect" program.

Check

Verify the operating system uses "pwquality" to enforce the password complexity rules.

Check for the use of "pwquality" with the following commands:

$ sudo cat /etc/pam.d/password-auth | grep pam_pwquality

password required pam_pwquality.so retry=3

$ sudo cat /etc/pam.d/system-auth | grep pam_pwquality

password required pam_pwquality.so retry=3

If both commands do not return a line containing the value "pam_pwquality.so", or the line is commented out, this is a finding.

If the value of "retry" is set to "0" or greater than "3", this is a finding.

Fix

Configure the operating system to use "pwquality" to enforce password complexity rules.

Add the following line to both "/etc/pam.d/password-auth" and "/etc/pam.d/system-auth" (or modify the line to have the required value):

password required pam_pwquality.so retry=3

RHEL 8 must enforce password complexity by requiring that at least one uppercase character be used.

STIG ID: RHEL-08-020110 | SRG: SRG-OS-000069-GPOS-00037 | Severity: medium | CCI: CCI-000192

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes pwquality as a mechanism to enforce password complexity. Note that in order to require uppercase characters, without degrading the "minlen" value, the credit value must be expressed as a negative number in "/etc/security/pwquality.conf".

Check

Verify the value for "ucredit" in "/etc/security/pwquality.conf" with the following command:

$ sudo grep ucredit /etc/security/pwquality.conf

ucredit = -1

If the value of "ucredit" is a positive number or is commented out, this is a finding.

Fix

Configure the operating system to enforce password complexity by requiring that at least one uppercase character be used by setting the "ucredit" option.

Add the following line to /etc/security/pwquality.conf (or modify the line to have the required value):

ucredit = -1

RHEL 8 must enforce password complexity by requiring that at least one lower-case character be used.

STIG ID: RHEL-08-020120 | SRG: SRG-OS-000070-GPOS-00038 | Severity: medium | CCI: CCI-000193

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes pwquality as a mechanism to enforce password complexity. Note that in order to require lower-case characters without degrading the "minlen" value, the credit value must be expressed as a negative number in "/etc/security/pwquality.conf".

Check

Verify the value for "lcredit" in "/etc/security/pwquality.conf" with the following command:

$ sudo grep lcredit /etc/security/pwquality.conf

lcredit = -1

If the value of "lcredit" is a positive number or is commented out, this is a finding.

Fix

Configure the operating system to enforce password complexity by requiring that at least one lower-case character be used by setting the "lcredit" option.

Add the following line to /etc/security/pwquality.conf (or modify the line to have the required value):

lcredit = -1

RHEL 8 must enforce password complexity by requiring that at least one numeric character be used.

STIG ID: RHEL-08-020130 | SRG: SRG-OS-000071-GPOS-00039 | Severity: medium | CCI: CCI-000194

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. Note that in order to require numeric characters, without degrading the minlen value, the credit value must be expressed as a negative number in "/etc/security/pwquality.conf".

Check

Verify the value for "dcredit" in "/etc/security/pwquality.conf" with the following command:

$ sudo grep dcredit /etc/security/pwquality.conf

dcredit = -1

If the value of "dcredit" is a positive number or is commented out, this is a finding.

Fix

Configure the operating system to enforce password complexity by requiring that at least one numeric character be used by setting the "dcredit" option.

Add the following line to /etc/security/pwquality.conf (or modify the line to have the required value):

dcredit = -1

RHEL 8 must require the maximum number of repeating characters of the same character class be limited to four when passwords are changed.

STIG ID: RHEL-08-020140 | SRG: SRG-OS-000072-GPOS-00040 | Severity: medium | CCI: CCI-000195

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. The "maxclassrepeat" option sets the maximum number of allowed same consecutive characters in the same class in the new password.

Check

Check for the value of the "maxclassrepeat" option in "/etc/security/pwquality.conf" with the following command:

$ sudo grep maxclassrepeat /etc/security/pwquality.conf

maxclassrepeat = 4

If the value of "maxclassrepeat" is set to more than "4" or is commented out, this is a finding.

Fix

Configure the operating system to require the change of the number of repeating characters of the same character class when passwords are changed by setting the "maxclassrepeat" option.

Add the following line to "/etc/security/pwquality.conf" conf (or modify the line to have the required value):

maxclassrepeat = 4

RHEL 8 must require the maximum number of repeating characters be limited to three when passwords are changed.

STIG ID: RHEL-08-020150 | SRG: SRG-OS-000072-GPOS-00040 | Severity: medium | CCI: CCI-000195

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. The "maxrepeat" option sets the maximum number of allowed same consecutive characters in a new password.

Check

Check for the value of the "maxrepeat" option in "/etc/security/pwquality.conf" with the following command:

$ sudo grep maxrepeat /etc/security/pwquality.conf

maxrepeat = 3

If the value of "maxrepeat" is set to more than "3" or is commented out, this is a finding.

Fix

Configure the operating system to require the change of the number of repeating consecutive characters when passwords are changed by setting the "maxrepeat" option.

Add the following line to "/etc/security/pwquality.conf conf" (or modify the line to have the required value):

maxrepeat = 3

RHEL 8 must require the change of at least four character classes when passwords are changed.

STIG ID: RHEL-08-020160 | SRG: SRG-OS-000072-GPOS-00040 | Severity: medium | CCI: CCI-000195

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. The "minclass" option sets the minimum number of required classes of characters for the new password (digits, uppercase, lowercase, others).

Check

Verify the value of the "minclass" option in "/etc/security/pwquality.conf" with the following command:

$ sudo grep minclass /etc/security/pwquality.conf
minclass = 4

If the value of "minclass" is set to less than "4" or is commented out, this is a finding.

Fix

Configure the operating system to require the change of at least four character classes when passwords are changed by setting the "minclass" option.

Add the following line to "/etc/security/pwquality.conf conf" (or modify the line to have the required value):

minclass = 4

RHEL 8 must require the change of at least 8 characters when passwords are changed.

STIG ID: RHEL-08-020170 | SRG: SRG-OS-000072-GPOS-00040 | Severity: medium | CCI: CCI-000195

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. The "difok" option sets the number of characters in a password that must not be present in the old password.

Check

Verify the value of the "difok" option in "/etc/security/pwquality.conf" with the following command:

$ sudo grep difok /etc/security/pwquality.conf

difok = 8

If the value of "difok" is set to less than "8" or is commented out, this is a finding.

Fix

Configure the operating system to require the change of at least eight of the total number of characters when passwords are changed by setting the "difok" option.

Add the following line to "/etc/security/pwquality.conf" (or modify the line to have the required value):

difok = 8

RHEL 8 passwords must have a 24 hours/1 day minimum password lifetime restriction in /etc/shadow.

STIG ID: RHEL-08-020180 | SRG: SRG-OS-000075-GPOS-00043 | Severity: medium | CCI: CCI-000198

Vulnerability Discussion

Enforcing a minimum password lifetime helps to prevent repeated password changes to defeat the password reuse or history enforcement requirement. If users are allowed to immediately and continually change their password, the password could be repeatedly changed in a short period of time to defeat the organization's policy regarding password reuse.

Check

Check whether the minimum time period between password changes for each user account is one day or greater.

$ sudo awk -F: '$4 < 1 {print $1 " " $4}' /etc/shadow

If any results are returned that are not associated with a system account, this is a finding.

Fix

Configure non-compliant accounts to enforce a 24 hours/1 day minimum password lifetime:

$ sudo chage -m 1 [user]

RHEL 8 passwords for new users or password changes must have a 24 hours/1 day minimum password lifetime restriction in /etc/logins.def.

STIG ID: RHEL-08-020190 | SRG: SRG-OS-000075-GPOS-00043 | Severity: medium | CCI: CCI-000198

Vulnerability Discussion

Check

Verify the operating system enforces 24 hours/1 day as the minimum password lifetime for new user accounts.

Check for the value of "PASS_MIN_DAYS" in "/etc/login.defs" with the following command:

$ sudo grep -i pass_min_days /etc/login.defs
PASS_MIN_DAYS 1

If the "PASS_MIN_DAYS" parameter value is not "1" or greater, or is commented out, this is a finding.

Fix

Configure the operating system to enforce 24 hours/1 day as the minimum password lifetime.

Add the following line in "/etc/login.defs" (or modify the line to have the required value):

PASS_MIN_DAYS 1

RHEL 8 user account passwords must have a 60-day maximum password lifetime restriction.

STIG ID: RHEL-08-020200 | SRG: SRG-OS-000076-GPOS-00044 | Severity: medium | CCI: CCI-000199

Vulnerability Discussion

Any password, no matter how complex, can eventually be cracked. Therefore, passwords need to be changed periodically. If RHEL 8 does not limit the lifetime of passwords and force users to change their passwords, there is the risk that RHEL 8 passwords could be compromised.

Check

Verify that RHEL 8 enforces a 60-day maximum password lifetime for new user accounts by running the following command:

$ sudo grep -i pass_max_days /etc/login.defs
PASS_MAX_DAYS 60

If the "PASS_MAX_DAYS" parameter value is greater than "60", or commented out, this is a finding.

Fix

Configure RHEL 8 to enforce a 60-day maximum password lifetime.

Add, or modify the following line in the "/etc/login.defs" file:

PASS_MAX_DAYS 60

RHEL 8 user account passwords must be configured so that existing passwords are restricted to a 60-day maximum lifetime.

STIG ID: RHEL-08-020210 | SRG: SRG-OS-000076-GPOS-00044 | Severity: medium | CCI: CCI-000199

Vulnerability Discussion

Check

Check whether the maximum time period for existing passwords is restricted to 60 days with the following commands:

$ sudo awk -F: '$5 > 60 {print $1 " " $5}' /etc/shadow

$ sudo awk -F: '$5 <= 0 {print $1 " " $5}' /etc/shadow

If any results are returned that are not associated with a system account, this is a finding.

Fix

Configure non-compliant accounts to enforce a 60-day maximum password lifetime restriction.

$ sudo chage -M 60 [user]

RHEL 8 passwords must be prohibited from reuse for a minimum of five generations.

STIG ID: RHEL-08-020220 | SRG: SRG-OS-000077-GPOS-00045 | Severity: medium | CCI: CCI-000200

Vulnerability Discussion

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. If the information system or application allows the user to reuse their password consecutively when that password has exceeded its defined lifetime, the end result is a password that is not changed per policy requirements.

RHEL 8 utilizes "pwquality" consecutively as a mechanism to enforce password complexity. This is set in both:
/etc/pam.d/password-auth
/etc/pam.d/system-auth.

Note that manual changes to the listed files may be overwritten by the "authselect" program.

Check

Verify the operating system prohibits password reuse for a minimum of five generations.

Check for the value of the "remember" argument in "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" with the following command:

$ sudo grep -i remember /etc/pam.d/system-auth /etc/pam.d/password-auth

password required pam_pwhistory.so use_authtok remember=5 retry=3

If the line containing "pam_pwhistory.so" does not have the "remember" module argument set, is commented out, or the value of the "remember" module argument is set to less than "5", this is a finding.

Fix

Configure the operating system to prohibit password reuse for a minimum of five generations.

Add the following line in "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" (or modify the line to have the required value):

password required pam_pwhistory.so use_authtok remember=5 retry=3

RHEL 8 passwords must have a minimum of 15 characters.

STIG ID: RHEL-08-020230 | SRG: SRG-OS-000078-GPOS-00046 | Severity: medium | CCI: CCI-000205

Vulnerability Discussion

The shorter the password, the lower the number of possible combinations that need to be tested before the password is compromised.

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to increase exponentially the time and/or resources required to compromise the password.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. Configurations are set in the "etc/security/pwquality.conf" file.

The "minlen", sometimes noted as minimum length, acts as a "score" of complexity based on the credit components of the "pwquality" module. By setting the credit components to a negative value, not only will those components be required, they will not count towards the total "score" of "minlen". This will enable "minlen" to require a 15-character minimum.

The DoD minimum password requirement is 15 characters.

Check

Verify the operating system enforces a minimum 15-character password length. The "minlen" option sets the minimum number of characters in a new password.

Check for the value of the "minlen" option in "/etc/security/pwquality.conf" with the following command:

$ sudo grep minlen /etc/security/pwquality.conf
minlen = 15

If the command does not return a "minlen" value of 15 or greater, this is a finding.

Fix

Configure operating system to enforce a minimum 15-character password length.

Add the following line to "/etc/security/pwquality.conf" (or modify the line to have the required value):

minlen = 15

RHEL 8 passwords for new users must have a minimum of 15 characters.

STIG ID: RHEL-08-020231 | SRG: SRG-OS-000078-GPOS-00046 | Severity: medium | CCI: CCI-000205

Vulnerability Discussion

Check

Verify that RHEL 8 enforces a minimum 15-character password length for new user accounts by running the following command:

$ sudo grep -i pass_min_len /etc/login.defs

PASS_MIN_LEN 15

If the "PASS_MIN_LEN" parameter value is less than "15", or commented out, this is a finding.

Fix

Configure operating system to enforce a minimum 15-character password length for new user accounts.

Add, or modify the following line in the "/etc/login.defs" file:

PASS_MIN_LEN 15

RHEL 8 duplicate User IDs (UIDs) must not exist for interactive users.

STIG ID: RHEL-08-020240 | SRG: SRG-OS-000104-GPOS-00051 | Severity: medium | CCI: CCI-000764

Vulnerability Discussion

To ensure accountability and prevent unauthenticated access, interactive users must be identified and authenticated to prevent potential misuse and compromise of the system.

Interactive users include organizational employees or individuals the organization deems to have equivalent status of employees (e.g., contractors). Interactive users (and processes acting on behalf of users) must be uniquely identified and authenticated to all accesses, except for the following:

1) Accesses explicitly identified and documented by the organization. Organizations document specific user actions that can be performed on the information system without identification or authentication; and

2) Accesses that occur through authorized use of group authenticators without individual authentication. Organizations may require unique identification of individuals in group accounts (e.g., shared privilege accounts) or for detailed accountability of individual activity.

Satisfies: SRG-OS-000104-GPOS-00051, SRG-OS-000121-GPOS-00062, SRG-OS-000042-GPOS-00020

Check

Verify that RHEL 8 contains no duplicate User IDs (UIDs) for interactive users.

Check that the operating system contains no duplicate UIDs for interactive users with the following command:

$ sudo awk -F ":" 'list[$3]++{print $1, $3}' /etc/passwd

If output is produced, and the accounts listed are interactive user accounts, this is a finding.

Fix

Edit the file "/etc/passwd" and provide each interactive user account that has a duplicate User ID (UID) with a unique UID.

RHEL 8 must implement smart card logon for multifactor authentication for access to interactive accounts.

STIG ID: RHEL-08-020250 | SRG: SRG-OS-000105-GPOS-00052 | Severity: medium | CCI: CCI-000765

Vulnerability Discussion

Using an authentication device, such as a Common Access Card (CAC) or token that is separate from the information system, ensures that even if the information system is compromised, that compromise will not affect credentials stored on the authentication device.

Multifactor solutions that require devices separate from information systems gaining access include, for example, hardware tokens providing time-based or challenge-response authenticators and smart cards such as the U.S. Government Personal Identity Verification card and the DoD CAC.

There are various methods of implementing multifactor authentication for RHEL 8. Some methods include a local system multifactor account mapping or joining the system to a domain and utilizing a Red Hat idM server or Microsoft Windows Active Directory server. Any of these methods will require that the client operating system handle the multifactor authentication correctly.

Satisfies: SRG-OS-000105-GPOS-00052, SRG-OS-000106-GPOS-00053, SRG-OS-000107-GPOS-00054, SRG-OS-000108-GPOS-00055

Check

Verify RHEL 8 uses multifactor authentication for local access to accounts.

Note: If the System Administrator demonstrates the use of an approved alternate multifactor authentication method, this requirement is not applicable.

Check that the "pam_cert_auth" setting is set to "true" in the "/etc/sssd/sssd.conf" file.

Check that the "try_cert_auth" or "require_cert_auth" options are configured in both "/etc/pam.d/system-auth" and "/etc/pam.d/smartcard-auth" files with the following command:

$ sudo grep cert_auth /etc/sssd/sssd.conf /etc/pam.d/*

/etc/sssd/sssd.conf:pam_cert_auth = True
/etc/pam.d/smartcard-auth:auth sufficient pam_sss.so try_cert_auth
/etc/pam.d/system-auth:auth [success=done authinfo_unavail=ignore ignore=ignore default=die] pam_sss.so try_cert_auth

If "pam_cert_auth" is not set to "true" in "/etc/sssd/sssd.conf", this is a finding.

If "pam_sss.so" is not set to "try_cert_auth" or "require_cert_auth" in both the "/etc/pam.d/smartcard-auth" and "/etc/pam.d/system-auth" files, this is a finding.

Fix

Configure RHEL 8 to use multifactor authentication for local access to accounts.

Add or update the "pam_cert_auth" setting in the "/etc/sssd/sssd.conf" file to match the following line:

[pam]
pam_cert_auth = True

Add or update "pam_sss.so" with "try_cert_auth" or "require_cert_auth" in the "/etc/pam.d/system-auth" and "/etc/pam.d/smartcard-auth" files based on the following examples:

/etc/pam.d/smartcard-auth:auth sufficient pam_sss.so try_cert_auth

/etc/pam.d/system-auth:auth [success=done authinfo_unavail=ignore ignore=ignore default=die] pam_sss.so try_cert_auth

The "sssd" service must be restarted for the changes to take effect. To restart the "sssd" service, run the following command:

$ sudo systemctl restart sssd.service

RHEL 8 account identifiers (individuals, groups, roles, and devices) must be disabled after 35 days of inactivity.

STIG ID: RHEL-08-020260 | SRG: SRG-OS-000118-GPOS-00060 | Severity: medium | CCI: CCI-000795

Vulnerability Discussion

Inactive identifiers pose a risk to systems and applications because attackers may exploit an inactive identifier and potentially obtain undetected access to the system. Owners of inactive accounts will not notice if unauthorized access to their user account has been obtained.

RHEL 8 needs to track periods of inactivity and disable application identifiers after 35 days of inactivity.

Check

Verify the account identifiers (individuals, groups, roles, and devices) are disabled after 35 days of inactivity with the following command:

Check the account inactivity value by performing the following command:

$ sudo grep -i inactive /etc/default/useradd

INACTIVE=35

If "INACTIVE" is set to "-1", a value greater than "35", or is commented out, this is a finding.

Fix

Configure RHEL 8 to disable account identifiers after 35 days of inactivity after the password expiration.

Run the following command to change the configuration for useradd:

$ sudo useradd -D -f 35

DoD recommendation is 35 days, but a lower value is acceptable. The value "-1" will disable this feature, and "0" will disable the account immediately after the password expires.

RHEL 8 emergency accounts must be automatically removed or disabled after the crisis is resolved or within 72 hours.

STIG ID: RHEL-08-020270 | SRG: SRG-OS-000123-GPOS-00064 | Severity: medium | CCI: CCI-001682

Vulnerability Discussion

Emergency accounts are privileged accounts established in response to crisis situations where the need for rapid account activation is required. Therefore, emergency account activation may bypass normal account authorization processes. If these accounts are automatically disabled, system maintenance during emergencies may not be possible, thus adversely affecting system availability.

Emergency accounts are different from infrequently used accounts (i.e., local logon accounts used by the organization's system administrators when network or normal logon/access is not available). Infrequently used accounts are not subject to automatic termination dates. Emergency accounts are accounts created in response to crisis situations, usually for use by maintenance personnel. The automatic expiration or disabling time period may be extended as needed until the crisis is resolved; however, it must not be extended indefinitely. A permanent account should be established for privileged users who need long-term maintenance accounts.

To address access requirements, many RHEL 8 systems can be integrated with enterprise-level authentication/access mechanisms that meet or exceed access control policy requirements.

Check

Verify emergency accounts have been provisioned with an expiration date of 72 hours.

For every existing emergency account, run the following command to obtain its account expiration information.

$ sudo chage -l system_account_name

Verify each of these accounts has an expiration date set within 72 hours.
If any emergency accounts have no expiration date set or do not expire within 72 hours, this is a finding.

Fix

If an emergency account must be created, configure the system to terminate the account after 72 hours with the following command to set an expiration date for the account. Substitute "system_account_name" with the account to be created.

$ sudo chage -E `date -d "+3 days" +%Y-%m-%d` system_account_name

The automatic expiration or disabling time period may be extended as needed until the crisis is resolved.

All RHEL 8 passwords must contain at least one special character.

STIG ID: RHEL-08-020280 | SRG: SRG-OS-000266-GPOS-00101 | Severity: medium | CCI: CCI-001619

Vulnerability Discussion

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. Note that to require special characters without degrading the "minlen" value, the credit value must be expressed as a negative number in "/etc/security/pwquality.conf".

Check

Verify the value for "ocredit" in "/etc/security/pwquality.conf" with the following command:

$ sudo grep ocredit /etc/security/pwquality.conf

ocredit = -1

If the value of "ocredit" is a positive number or is commented out, this is a finding.

Fix

Configure the operating system to enforce password complexity by requiring that at least one special character be used by setting the "ocredit" option.

Add the following line to /etc/security/pwquality.conf (or modify the line to have the required value):

ocredit = -1

RHEL 8 must prohibit the use of cached authentications after one day.

STIG ID: RHEL-08-020290 | SRG: SRG-OS-000383-GPOS-00166 | Severity: medium | CCI: CCI-002007

Vulnerability Discussion

If cached authentication information is out-of-date, the validity of the authentication information may be questionable.

RHEL 8 includes multiple options for configuring authentication, but this requirement will be focus on the System Security Services Daemon (SSSD). By default sssd does not cache credentials.

Check

Verify that the SSSD prohibits the use of cached authentications after one day.

Note: If smart card authentication is not being used on the system this item is Not Applicable.

Check that SSSD allows cached authentications with the following command:

$ sudo grep cache_credentials /etc/sssd/sssd.conf

cache_credentials = true

If "cache_credentials" is set to "false" or missing from the configuration file, this is not a finding and no further checks are required.

If "cache_credentials" is set to "true", check that SSSD prohibits the use of cached authentications after one day with the following command:

$ sudo grep offline_credentials_expiration /etc/sssd/sssd.conf

offline_credentials_expiration = 1

If "offline_credentials_expiration" is not set to a value of "1", this is a finding.

Fix

Configure the SSSD to prohibit the use of cached authentications after one day.

Add or change the following line in "/etc/sssd/sssd.conf" just below the line "[pam]".

offline_credentials_expiration = 1

RHEL 8 must prevent the use of dictionary words for passwords.

STIG ID: RHEL-08-020300 | SRG: SRG-OS-000480-GPOS-00225 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If RHEL 8 allows the user to select passwords based on dictionary words, this increases the chances of password compromise by increasing the opportunity for successful guesses, and brute-force attacks.

Check

Verify RHEL 8 prevents the use of dictionary words for passwords.

Determine if the field "dictcheck" is set in the "/etc/security/pwquality.conf" or "/etc/pwquality.conf.d/*.conf" files with the following command:

$ sudo grep dictcheck /etc/security/pwquality.conf /etc/pwquality.conf.d/*.conf

dictcheck=1

If the "dictcheck" parameter is not set to "1", or is commented out, this is a finding.

Fix

Configure RHEL 8 to prevent the use of dictionary words for passwords.

Add or update the following line in the "/etc/security/pwquality.conf" file or a configuration file in the /etc/pwquality.conf.d/ directory to contain the "dictcheck" parameter:

dictcheck=1

RHEL 8 must enforce a delay of at least four seconds between logon prompts following a failed logon attempt.

STIG ID: RHEL-08-020310 | SRG: SRG-OS-000480-GPOS-00226 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Configuring the operating system to implement organization-wide security implementation guides and security checklists verifies compliance with federal standards and establishes a common security baseline across the DoD that reflects the most restrictive security posture consistent with operational requirements.

Configuration settings are the set of parameters that can be changed in hardware, software, or firmware components of the system that affect the security posture and/or functionality of the system. Security-related parameters are those parameters impacting the security state of the system, including the parameters required to satisfy other security control requirements. Security-related parameters include, for example, registry settings; account, file, and directory permission settings; and settings for functions, ports, protocols, services, and remote connections.

Check

Verify the operating system enforces a delay of at least four seconds between console logon prompts following a failed logon attempt with the following command:

$ sudo grep -i fail_delay /etc/login.defs

FAIL_DELAY 4

If the value of "FAIL_DELAY" is not set to "4" or greater, or the line is commented out, this is a finding.

Fix

Configure the operating system to enforce a delay of at least four seconds between logon prompts following a failed console logon attempt.

Modify the "/etc/login.defs" file to set the "FAIL_DELAY" parameter to "4" or greater:

FAIL_DELAY 4

RHEL 8 must not have unnecessary accounts.

STIG ID: RHEL-08-020320 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Accounts providing no operational purpose provide additional opportunities for system compromise. Unnecessary accounts include user accounts for individuals not requiring access to the system and application accounts for applications not installed on the system.

Check

Verify all accounts on the system are assigned to an active system, application, or user account.

Obtain the list of authorized system accounts from the Information System Security Officer (ISSO).

Check the system accounts on the system with the following command:

$ sudo more /etc/passwd

root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
games:x:12:100:games:/usr/games:/sbin/nologin
gopher:x:13:30:gopher:/var/gopher:/sbin/nologin

Accounts such as "games" and "gopher" are not authorized accounts as they do not support authorized system functions.

If the accounts on the system do not match the provided documentation, or accounts that do not support an authorized system function are present, this is a finding.

Fix

Configure the system so all accounts on the system are assigned to an active system, application, or user account.

Remove accounts that do not support approved system activities or that allow for a normal user to perform administrative-level actions.

Document all authorized accounts on the system.

RHEL 8 must not have accounts configured with blank or null passwords.

STIG ID: RHEL-08-020330 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

If an account has an empty password, anyone could log on and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.

Check

To verify that null passwords cannot be used, run the following commands:

$ sudo grep -i nullok /etc/pam.d/system-auth /etc/pam.d/password-auth

If this produces any output, it may be possible to log on with accounts with empty passwords.

$ sudo grep -i permitemptypasswords /etc/ssh/sshd_config

PermitEmptyPasswords no

If "PermitEmptyPasswords" is set to "yes", or If null passwords can be used, this is a finding.

Note: Manual changes to the listed files may be overwritten by the "authselect" program.

Fix

Remove any instances of the "nullok" option in "/etc/pam.d/system-auth" and "/etc/pam.d/password-auth" and add or edit the following line in "etc/ssh/sshd_config" to prevent logons with empty passwords.

PermitEmptyPasswords no

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service

Note: Manual changes to the listed files may be overwritten by the "authselect" program.

RHEL 8 must display the date and time of the last successful account logon upon logon.

STIG ID: RHEL-08-020340 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

Providing users with feedback on when account accesses last occurred facilitates user recognition and reporting of unauthorized account use.

Check

Verify users are provided with feedback on when account accesses last occurred with the following command:

$ sudo grep pam_lastlog /etc/pam.d/postlogin

session required pam_lastlog.so showfailed

If "pam_lastlog" is missing from "/etc/pam.d/postlogin" file, or the silent option is present, this is a finding.

Fix

Configure the operating system to provide users with feedback on when account accesses last occurred by setting the required configuration options in "/etc/pam.d/postlogin".

Add the following line to the top of "/etc/pam.d/postlogin":

session required pam_lastlog.so showfailed

RHEL 8 must display the date and time of the last successful account logon upon an SSH logon.

STIG ID: RHEL-08-020350 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Providing users with feedback on when account accesses via SSH last occurred facilitates user recognition and reporting of unauthorized account use.

Check

Verify SSH provides users with feedback on when account accesses last occurred with the following command:

$ sudo grep -i printlastlog /etc/ssh/sshd_config

PrintLastLog yes

If the "PrintLastLog" keyword is set to "no", is missing, or is commented out, this is a finding.

Fix

Configure SSH to provide users with feedback on when account accesses last occurred by setting the required configuration options in "/etc/pam.d/sshd" or in the "sshd_config" file used by the system ("/etc/ssh/sshd_config" will be used in the example) (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor).

Modify the "PrintLastLog" line in "/etc/ssh/sshd_config" to match the following:

PrintLastLog yes

The SSH service must be restarted for changes to "sshd_config" to take effect.

RHEL 8 must define default permissions for all authenticated users in such a way that the user can only read and modify their own files.

STIG ID: RHEL-08-020351 | SRG: SRG-OS-000480-GPOS-00228 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Setting the most restrictive default permissions ensures that when new accounts are created, they do not have unnecessary access.

Check

Verify the operating system defines default permissions for all authenticated users in such a way that the user can only read and modify their own files.

Check for the value of the "UMASK" parameter in "/etc/login.defs" file with the following command:

Note: If the value of the "UMASK" parameter is set to "000" in "/etc/login.defs" file, the Severity is raised to a CAT I.

# grep -i umask /etc/login.defs

UMASK 077

If the value for the "UMASK" parameter is not "077", or the "UMASK" parameter is missing or is commented out, this is a finding.

Fix

Configure the operating system to define default permissions for all authenticated users in such a way that the user can only read and modify their own files.

Add or edit the line for the "UMASK" parameter in "/etc/login.defs" file to "077":

UMASK 077

RHEL 8 must set the umask value to 077 for all local interactive user accounts.

STIG ID: RHEL-08-020352 | SRG: SRG-OS-000480-GPOS-00228 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The umask controls the default access mode assigned to newly created files. A umask of 077 limits new files to mode 600 or less permissive. Although umask can be represented as a four-digit number, the first digit representing special access modes is typically ignored or required to be "0". This requirement applies to the globally configured system defaults and the local interactive user defaults for each account on the system.

Check

Verify that the default umask for all local interactive users is "077".

Identify the locations of all local interactive user home directories by looking at the "/etc/passwd" file.

Check all local interactive user initialization files for interactive users with the following command:

Note: The example is for a system that is configured to create users home directories in the "/home" directory.

# grep -i umask /home/*/.*

If any local interactive user initialization files are found to have a umask statement that has a value less restrictive than "077", this is a finding.

Fix

Remove the umask statement from all local interactive user's initialization files.

If the account is for an application, the requirement for a umask less restrictive than "077" can be documented with the Information System Security Officer, but the user agreement for access to the account must specify that the local interactive user must log on to their account first and then switch the user to the application account with the correct option to gain the account's environment variables.

RHEL 8 must define default permissions for logon and non-logon shells.

STIG ID: RHEL-08-020353 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify that the umask default for installed shells is "077".

Check for the value of the "UMASK" parameter in the "/etc/bashrc" and "/etc/csh.cshrc" files with the following command:

Note: If the value of the "UMASK" parameter is set to "000" in either the "/etc/bashrc" or the "/etc/csh.cshrc" files, the Severity is raised to a CAT I.

# grep -i umask /etc/bashrc /etc/csh.cshrc

/etc/bashrc: umask 077
/etc/bashrc: umask 077
/etc/csh.cshrc: umask 077
/etc/csh.cshrc: umask 077

If the value for the "UMASK" parameter is not "077", or the "UMASK" parameter is missing or is commented out, this is a finding.

Fix

Configure the operating system to define default permissions for all authenticated users in such a way that the user can only read and modify their own files.

Add or edit the lines for the "UMASK" parameter in the "/etc/bashrc" and "etc/csh.cshrc" files to "077":

UMASK 077

The RHEL 8 audit system must be configured to audit the execution of privileged functions and prevent all software from executing at higher privilege levels than users executing the software.

STIG ID: RHEL-08-030000 | SRG: SRG-OS-000326-GPOS-00126 | Severity: medium | CCI: CCI-002233

Vulnerability Discussion

Misuse of privileged functions, either intentionally or unintentionally by authorized users, or by unauthorized external entities that have compromised information system accounts, is a serious and ongoing concern and can have significant adverse impacts on organizations. Auditing the use of privileged functions is one way to detect such misuse and identify the risk from insider threats and the advanced persistent threat.

Satisfies: SRG-OS-000326-GPOS-00126, SRG-OS-000327-GPOS-00127

Check

Verify RHEL 8 audits the execution of privileged functions.

Check if RHEL 8 is configured to audit the execution of the "execve" system call, by running the following command:

$ sudo grep execve /etc/audit/audit.rules

-a always,exit -F arch=b32 -S execve -C uid!=euid -F euid=0 -k execpriv
-a always,exit -F arch=b64 -S execve -C uid!=euid -F euid=0 -k execpriv

-a always,exit -F arch=b32 -S execve -C gid!=egid -F egid=0 -k execpriv
-a always,exit -F arch=b64 -S execve -C gid!=egid -F egid=0 -k execpriv

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the "execve" system call.

Add or update the following file system rules to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S execve -C uid!=euid -F euid=0 -k execpriv
-a always,exit -F arch=b64 -S execve -C uid!=euid -F euid=0 -k execpriv

-a always,exit -F arch=b32 -S execve -C gid!=egid -F egid=0 -k execpriv
-a always,exit -F arch=b64 -S execve -C gid!=egid -F egid=0 -k execpriv

The audit daemon must be restarted for the changes to take effect.

Cron logging must be implemented in RHEL 8.

STIG ID: RHEL-08-030010 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Cron logging can be used to trace the successful or unsuccessful execution of cron jobs. It can also be used to spot intrusions into the use of the cron facility by unauthorized and malicious users.

Check

Verify that "rsyslog" is configured to log cron events with the following command:

Note: If another logging package is used, substitute the utility configuration file for "/etc/rsyslog.conf" or "/etc/rsyslog.d/*.conf" files.

$ sudo grep -s cron /etc/rsyslog.conf /etc/rsyslog.d/*.conf

/etc/rsyslog.conf:*.info;mail.none;authpriv.none;cron.none /var/log/messages
/etc/rsyslog.conf:# Log cron stuff
/etc/rsyslog.conf:cron.* /var/log/cron.log

If the command does not return a response, check for cron logging all facilities with the following command.

$ sudo grep -s /var/log/messages /etc/rsyslog.conf /etc/rsyslog.d/*.conf

/etc/rsyslog.conf:*.info;mail.none;authpriv.none;cron.none /var/log/messages

If "rsyslog" is not logging messages for the cron facility or all facilities, this is a finding.

Fix

Configure "rsyslog" to log all cron messages by adding or updating the following line to "/etc/rsyslog.conf" or a configuration file in the /etc/rsyslog.d/ directory:

cron.* /var/log/cron.log

The RHEL 8 System Administrator (SA) and Information System Security Officer (ISSO) (at a minimum) must be alerted of an audit processing failure event.

STIG ID: RHEL-08-030020 | SRG: SRG-OS-000046-GPOS-00022 | Severity: medium | CCI: CCI-000139

Vulnerability Discussion

It is critical for the appropriate personnel to be aware if a system is at risk of failing to process audit logs as required. Without this notification, the security personnel may be unaware of an impending failure of the audit capability, and system operation may be adversely affected.

Audit processing failures include software/hardware errors, failures in the audit capturing mechanisms, and audit storage capacity being reached or exceeded.

This requirement applies to each audit data storage repository (i.e., distinct information system component where audit records are stored), the centralized audit storage capacity of organizations (i.e., all audit data storage repositories combined), or both.

Check

Verify that the SA and ISSO (at a minimum) are notified in the event of an audit processing failure.

Check that RHEL 8 notifies the SA and ISSO (at a minimum) in the event of an audit processing failure with the following command:

$ sudo grep action_mail_acct /etc/audit/auditd.conf

action_mail_acct = root

If the value of the "action_mail_acct" keyword is not set to "root" and/or other accounts for security personnel, the "action_mail_acct" keyword is missing, or the retuned line is commented out, ask the system administrator to indicate how they and the ISSO are notified of an audit process failure. If there is no evidence of the proper personnel being notified of an audit processing failure, this is a finding.

Fix

Configure "auditd" service to notify the SA and ISSO in the event of an audit processing failure.

Edit the following line in "/etc/audit/auditd.conf" to ensure that administrators are notified via email for those situations:

action_mail_acct = root

The RHEL 8 Information System Security Officer (ISSO) and System Administrator (SA) (at a minimum) must have mail aliases to be notified of an audit processing failure.

STIG ID: RHEL-08-030030 | SRG: SRG-OS-000046-GPOS-00022 | Severity: medium | CCI: CCI-000139

Vulnerability Discussion

Check

Verify that the administrators are notified in the event of an audit processing failure.

Check that the "/etc/aliases" file has a defined value for "root".

$ sudo grep "postmaster:\s*root$" /etc/aliases

If the command does not return a line, or the line is commented out, ask the system administrator to indicate how they and the ISSO are notified of an audit process failure. If there is no evidence of the proper personnel being notified of an audit processing failure, this is a finding.

Fix

Configure RHEL 8 to notify administrators in the event of an audit processing failure.

Add/update the following line in "/etc/aliases":

postmaster: root

The RHEL 8 System must take appropriate action when an audit processing failure occurs.

STIG ID: RHEL-08-030040 | SRG: SRG-OS-000047-GPOS-00023 | Severity: medium | CCI: CCI-000140

Vulnerability Discussion

Check

Verify RHEL 8 takes the appropriate action when an audit processing failure occurs.

Check that RHEL 8 takes the appropriate action when an audit processing failure occurs with the following command:

$ sudo grep disk_error_action /etc/audit/auditd.conf

disk_error_action = HALT

If the value of the "disk_error_action" option is not "SYSLOG", "SINGLE", or "HALT", or the line is commented out, ask the system administrator to indicate how the system takes appropriate action when an audit process failure occurs. If there is no evidence of appropriate action, this is a finding.

Fix

Configure RHEL 8 to shut down by default upon audit failure (unless availability is an overriding concern).

Add or update the following line (depending on configuration "disk_error_action" can be set to "SYSLOG" or "SINGLE" depending on configuration) in "/etc/audit/auditd.conf" file:

disk_error_action = HALT

If availability has been determined to be more important, and this decision is documented with the ISSO, configure the operating system to notify system administration staff and ISSO staff in the event of an audit processing failure by setting the "disk_error_action" to "SYSLOG".

The RHEL 8 System Administrator (SA) and Information System Security Officer (ISSO) (at a minimum) must be alerted when the audit storage volume is full.

STIG ID: RHEL-08-030050 | SRG: SRG-OS-000047-GPOS-00023 | Severity: medium | CCI: CCI-000140

Vulnerability Discussion

It is critical that when RHEL 8 is at risk of failing to process audit logs as required, it takes action to mitigate the failure. Audit processing failures include software/hardware errors; failures in the audit capturing mechanisms; and audit storage capacity being reached or exceeded. Responses to audit failure depend upon the nature of the failure mode.

When availability is an overriding concern, other approved actions in response to an audit failure are as follows:

1) If the failure was caused by the lack of audit record storage capacity, RHEL 8 must continue generating audit records if possible (automatically restarting the audit service if necessary) and overwriting the oldest audit records in a first-in-first-out manner.

2) If audit records are sent to a centralized collection server and communication with this server is lost or the server fails, RHEL 8 must queue audit records locally until communication is restored or until the audit records are retrieved manually. Upon restoration of the connection to the centralized collection server, action should be taken to synchronize the local audit data with the collection server.

Check

Verify that the SA and ISSO (at a minimum) are notified when the audit storage volume is full.

Check which action RHEL 8 takes when the audit storage volume is full with the following command:

$ sudo grep max_log_file_action /etc/audit/auditd.conf

max_log_file_action=syslog

If the value of the "max_log_file_action" option is set to "ignore", "rotate", or "suspend", or the line is commented out, ask the system administrator to indicate how the system takes appropriate action when an audit storage volume is full. If there is no evidence of appropriate action, this is a finding.

Fix

Configure RHEL 8 to notify the System Administrator (SA) and Information System Security Officer (ISSO) when the audit storage volume is full by configuring the "max_log_file_action" parameter in the "/etc/audit/auditd.conf" file with the a value of "syslog" or "keep_logs":

max_log_file_action=syslog

The RHEL 8 audit system must take appropriate action when the audit storage volume is full.

STIG ID: RHEL-08-030060 | SRG: SRG-OS-000047-GPOS-00023 | Severity: medium | CCI: CCI-000140

Vulnerability Discussion

Check

Verify RHEL 8 takes the appropriate action when the audit storage volume is full.

Check that RHEL 8 takes the appropriate action when the audit storage volume is full with the following command:

$ sudo grep disk_full_action /etc/audit/auditd.conf

disk_full_action = HALT

If the value of the "disk_full_action" option is not "SYSLOG", "SINGLE", or "HALT", or the line is commented out, ask the system administrator to indicate how the system takes appropriate action when an audit storage volume is full. If there is no evidence of appropriate action, this is a finding.

Fix

Configure RHEL 8 to shut down by default upon audit failure (unless availability is an overriding concern).

Add or update the following line (depending on configuration "disk_full_action" can be set to "SYSLOG" or "SINGLE" depending on configuration) in "/etc/audit/auditd.conf" file:

disk_full_action = HALT

If availability has been determined to be more important, and this decision is documented with the ISSO, configure the operating system to notify system administration staff and ISSO staff in the event of an audit processing failure by setting the "disk_full_action" to "SYSLOG".

The RHEL 8 audit system must audit local events.

STIG ID: RHEL-08-030061 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the RHEL 8 Audit Daemon is configured to include local events, with the following command:

$ sudo grep local_events /etc/audit/auditd.conf

local_events = yes

If the value of the "local_events" option is not set to "yes", or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to audit local events on the system.

Add or update the following line in "/etc/audit/auditd.conf" file:

local_events = yes

RHEL 8 must label all off-loaded audit logs before sending them to the central log server.

STIG ID: RHEL-08-030062 | SRG: SRG-OS-000342-GPOS-00133 | Severity: medium | CCI: CCI-001851

Vulnerability Discussion

Check

Verify the RHEL 8 Audit Daemon is configured to label all off-loaded audit logs, with the following command:

$ sudo grep "name_format" /etc/audit/auditd.conf

name_format = hostname

If the "name_format" option is not "hostname", "fqd", or "numeric", or the line is commented out, this is a finding.

Fix

Edit the /etc/audit/auditd.conf file and add or update the "name_format" option:

name_format = hostname

The audit daemon must be restarted for changes to take effect.

RHEL 8 must resolve audit information before writing to disk.

STIG ID: RHEL-08-030063 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the RHEL 8 Audit Daemon is configured to resolve audit information before writing to disk, with the following command:

$ sudo grep "log_format" /etc/audit/auditd.conf

log_format = ENRICHED

If the "log_format" option is not "ENRICHED", or the line is commented out, this is a finding.

Fix

Edit the /etc/audit/auditd.conf file and add or update the "log_format" option:

log_format = ENRICHED

The audit daemon must be restarted for changes to take effect.

RHEL 8 audit logs must have a mode of 0600 or less permissive to prevent unauthorized read access.

STIG ID: RHEL-08-030070 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Check

Verify the audit logs have a mode of "0600" or less permissive.

First, determine where the audit logs are stored with the following command:

$ sudo grep -iw log_file /etc/audit/auditd.conf

log_file = /var/log/audit/audit.log

Using the location of the audit log file, check if the audit log has a mode of "0600" or less permissive with the following command:

$ sudo stat -c "%a %n" /var/log/audit/audit.log

600 /var/log/audit/audit.log

If the audit log has a mode more permissive than "0600", this is a finding.

Fix

Configure the audit log to be protected from unauthorized read access by configuring the log group in the /etc/audit/auditd.conf file:

log_group = root

RHEL 8 audit logs must be owned by root to prevent unauthorized read access.

STIG ID: RHEL-08-030080 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Check

Verify the audit logs are owned by "root". First, determine where the audit logs are stored with the following command:

$ sudo grep -iw log_file /etc/audit/auditd.conf

log_file = /var/log/audit/audit.log

Using the location of the audit log file, determine if the audit log is owned by "root" using the following command:

$ sudo ls -al /var/log/audit/audit.log

rw------- 2 root root 23 Jun 11 11:56 /var/log/audit/audit.log

If the audit log is not owned by "root", this is a finding.

Fix

Configure the audit log to be protected from unauthorized read access, by setting the correct owner as "root" with the following command:

$ sudo chown root [audit_log_file]

Replace "[audit_log_file]" to the correct audit log path, by default this location is "/var/log/audit/audit.log".

RHEL 8 audit logs must be group-owned by root to prevent unauthorized read access.

STIG ID: RHEL-08-030090 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Check

Verify the audit logs are group-owned by "root". First determine where the audit logs are stored with the following command:

$ sudo grep -iw log_file /etc/audit/auditd.conf

log_file = /var/log/audit/audit.log

Using the location of the audit log file, determine if the audit log is group-owned by "root" using the following command:

$ sudo ls -al /var/log/audit/audit.log

rw------- 2 root root 23 Jun 11 11:56 /var/log/audit/audit.log

If the audit log is not group-owned by "root", this is a finding.

Fix

Configure the audit log to be owned by root by configuring the log group in the /etc/audit/auditd.conf file:

log_group = root

RHEL 8 audit log directory must be owned by root to prevent unauthorized read access.

STIG ID: RHEL-08-030100 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Check

Verify the audit log directory is owned by "root" to prevent unauthorized read access.

Determine where the audit logs are stored with the following command:

$ sudo grep -iw log_file /etc/audit/auditd.conf

log_file = /var/log/audit/audit.log

Determine the owner of the audit log directory by using the output of the above command (ex: "/var/log/audit/"). Run the following command with the correct audit log directory path:

$ sudo ls -ld /var/log/audit

drw------- 2 root root 23 Jun 11 11:56 /var/log/audit

If the audit log directory is not owned by "root", this is a finding.

Fix

Configure the audit log to be protected from unauthorized read access, by setting the correct owner as "root" with the following command:

$ sudo chown root [audit_log_directory]

Replace "[audit_log_directory]" with the correct audit log directory path, by default this location is usually "/var/log/audit".

RHEL 8 audit log directory must be group-owned by root to prevent unauthorized read access.

STIG ID: RHEL-08-030110 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Check

Verify the audit log directory is group-owned by "root" to prevent unauthorized read access.

Determine where the audit logs are stored with the following command:

$ sudo grep -iw log_file /etc/audit/auditd.conf

log_file = /var/log/audit/audit.log

Determine the group owner of the audit log directory by using the output of the above command (ex: "/var/log/audit/"). Run the following command with the correct audit log directory path:

$ sudo ls -ld /var/log/audit

drw------- 2 root root 23 Jun 11 11:56 /var/log/audit

If the audit log directory is not group-owned by "root", this is a finding.

Fix

Configure the audit log to be protected from unauthorized read access by setting the correct group-owner as "root" with the following command:

$ sudo chgrp root [audit_log_directory]

Replace "[audit_log_directory]" with the correct audit log directory path, by default this location is usually "/var/log/audit".

RHEL 8 audit log directory must have a mode of 0700 or less permissive to prevent unauthorized read access.

STIG ID: RHEL-08-030120 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Check

Verify the audit log directories have a mode of "0700" or less permissive by first determining where the audit logs are stored with the following command:

$ sudo grep -iw log_file /etc/audit/auditd.conf

log_file = /var/log/audit/audit.log

Using the location of the audit log, determine the directory where the audit logs are stored (ex: "/var/log/audit"). Run the following command to determine the permissions for the audit log folder:

$ sudo stat -c "%a %n" /var/log/audit

700 /var/log/audit

If the audit log directory has a mode more permissive than "0700", this is a finding.

Fix

Configure the audit log directory to be protected from unauthorized read access by setting the correct permissive mode with the following command:

$ sudo chmod 0700 [audit_log_directory]

Replace "[audit_log_directory]" to the correct audit log directory path, by default this location is "/var/log/audit".

RHEL 8 audit system must protect auditing rules from unauthorized change.

STIG ID: RHEL-08-030121 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Unauthorized disclosure of audit records can reveal system and configuration data to attackers, thus compromising its confidentiality.

Audit information includes all information (e.g., audit records, audit settings, audit reports) needed to successfully audit RHEL 8 system activity.

In immutable mode, unauthorized users cannot execute changes to the audit system to potentially hide malicious activity and then put the audit rules back. A system reboot would be noticeable and a system administrator could then investigate the unauthorized changes.

Satisfies: SRG-OS-000057-GPOS-00027, SRG-OS-000058-GPOS-00028, SRG-OS-000059-GPOS-00029

Check

Verify the audit system prevents unauthorized changes with the following command:

$ sudo grep "^\s*[^#]" /etc/audit/audit.rules | tail -1

-e 2

If the audit system is not set to be immutable by adding the "-e 2" option to the "/etc/audit/audit.rules", this is a finding.

Fix

Configure the audit system to set the audit rules to be immutable by adding the following line to "/etc/audit/rules.d/audit.rules"

-e 2

Note: Once set, the system must be rebooted for auditing to be changed. It is recommended to add this option as the last step in securing the system.

RHEL 8 audit system must protect logon UIDs from unauthorized change.

STIG ID: RHEL-08-030122 | SRG: SRG-OS-000057-GPOS-00027 | Severity: medium | CCI: CCI-000162

Vulnerability Discussion

Check

Verify the audit system prevents unauthorized changes to logon UIDs with the following command:

$ sudo grep -i immutable /etc/audit/audit.rules

--loginuid-immutable

If the login UIDs are not set to be immutable by adding the "--loginuid-immutable" option to the "/etc/audit/audit.rules", this is a finding.

Fix

Configure the audit system to set the logon UIDs to be immutable by adding the following line to "/etc/audit/rules.d/audit.rules"

--loginuid-immutable

RHEL 8 must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/shadow.

STIG ID: RHEL-08-030130 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Check

Verify RHEL 8 generates audit records for all account creations, modifications, disabling, and termination events that affect "/etc/shadow".

Check the auditing rules in "/etc/audit/audit.rules" with the following command:

$ sudo grep /etc/shadow /etc/audit/audit.rules

-w /etc/shadow -p wa -k identity

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records for all account creations, modifications, disabling, and termination events that affect "/etc/shadow".

Add or update the following file system rule to "/etc/audit/rules.d/audit.rules":

-w /etc/shadow -p wa -k identity

The audit daemon must be restarted for the changes to take effect.

RHEL 8 must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/security/opasswd.

STIG ID: RHEL-08-030140 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Check

Verify RHEL 8 generates audit records for all account creations, modifications, disabling, and termination events that affect "/etc/security/opasswd".

Check the auditing rules in "/etc/audit/audit.rules" with the following command:

$ sudo grep /etc/security/opasswd /etc/audit/audit.rules

-w /etc/security/opasswd -p wa -k identity

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records for all account creations, modifications, disabling, and termination events that affect "/etc/security/opasswd".

Add or update the following file system rule to "/etc/audit/rules.d/audit.rules":

-w /etc/security/opasswd -p wa -k identity

The audit daemon must be restarted for the changes to take effect.

RHEL 8 must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/passwd.

STIG ID: RHEL-08-030150 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Check

Verify RHEL 8 generates audit records for all account creations, modifications, disabling, and termination events that affect "/etc/passwd".

Check the auditing rules in "/etc/audit/audit.rules" with the following command:

$ sudo grep /etc/passwd /etc/audit/audit.rules

-w /etc/passwd -p wa -k identity

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records for all account creations, modifications, disabling, and termination events that affect "/etc/passwd".

Add or update the following file system rule to "/etc/audit/rules.d/audit.rules":

-w /etc/passwd -p wa -k identity

The audit daemon must be restarted for the changes to take effect.

RHEL 8 must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/gshadow.

STIG ID: RHEL-08-030160 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Check

Verify RHEL 8 generates audit records for all account creations, modifications, disabling, and termination events that affect "/etc/gshadow".

Check the auditing rules in "/etc/audit/audit.rules" with the following command:

$ sudo grep /etc/gshadow /etc/audit/audit.rules

-w /etc/gshadow -p wa -k identity

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records for all account creations, modifications, disabling, and termination events that affect "/etc/gshadow".

Add or update the following file system rule to "/etc/audit/rules.d/audit.rules":

-w /etc/gshadow -p wa -k identity

The audit daemon must be restarted for the changes to take effect.

RHEL 8 must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/group.

STIG ID: RHEL-08-030170 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Check

Verify RHEL 8 generates audit records for all account creations, modifications, disabling, and termination events that affect "/etc/group".

Check the auditing rules in "/etc/audit/audit.rules" with the following command:

$ sudo grep /etc/group /etc/audit/audit.rules

-w /etc/group -p wa -k identity

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records for all account creations, modifications, disabling, and termination events that affect "/etc/group".

Add or update the following file system rule to "/etc/audit/rules.d/audit.rules":

-w /etc/group -p wa -k identity

The audit daemon must be restarted for the changes to take effect.

RHEL 8 must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/sudoers.

STIG ID: RHEL-08-030171 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Check

Verify RHEL 8 generates audit records for all account creations, modifications, disabling, and termination events that affect "/etc/sudoers".

Check the auditing rules in "/etc/audit/audit.rules" with the following command:

$ sudo grep /etc/sudoers /etc/audit/audit.rules

-w /etc/sudoers -p wa -k identity

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records for all account creations, modifications, disabling, and termination events that affect "/etc/sudoers".

Add or update the following file system rule to "/etc/audit/rules.d/audit.rules":

-w /etc/sudoers -p wa -k identity

The audit daemon must be restarted for the changes to take effect.

RHEL 8 must generate audit records for all account creations, modifications, disabling, and termination events that affect /etc/sudoers.d/.

STIG ID: RHEL-08-030172 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Check

Verify RHEL 8 generates audit records for all account creations, modifications, disabling, and termination events that affect "/etc/sudoers.d/".

Check the auditing rules in "/etc/audit/audit.rules" with the following command:

$ sudo grep /etc/sudoers.d/ /etc/audit/audit.rules

-w /etc/sudoers.d/ -p wa -k identity

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records for all account creations, modifications, disabling, and termination events that affect "/etc/sudoers.d/".

Add or update the following file system rule to "/etc/audit/rules.d/audit.rules":

-w /etc/sudoers.d/ -p wa -k identity

The audit daemon must be restarted for the changes to take effect.

RHEL 8 audit records must contain information to establish what type of events occurred, the source of events, where events occurred, and the outcome of events.

STIG ID: RHEL-08-030180 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without establishing what type of events occurred, the source of events, where events occurred, and the outcome of events, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack.

Audit record content that may be necessary to satisfy this requirement includes, for example, time stamps, source and destination addresses, user/process identifiers, event descriptions, success/fail indications, filenames involved, and access control or flow control rules invoked.

Associating event types with detected events in RHEL 8 audit logs provides a means of investigating an attack, recognizing resource utilization or capacity thresholds, or identifying an improperly configured RHEL 8 system.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000038-GPOS-00016, SRG-OS-000039-GPOS-00017, SRG-OS-000040-GPOS-00018, SRG-OS-000041-GPOS-00019, SRG-OS-000042-GPOS-00021, SRG-OS-000051-GPOS-00024, SRG-OS-000054-GPOS-00025, SRG-OS-000122-GPOS-00063, SRG-OS-000254-GPOS-00095, SRG-OS-000255-GPOS-00096, SRG-OS-000337-GPOS-00129, SRG-OS-000348-GPOS-00136, SRG-OS-000349-GPOS-00137, SRG-OS-000350-GPOS-00138, SRG-OS-000351-GPOS-00139, SRG-OS-000352-GPOS-00140, SRG-OS-000353-GPOS-00141, SRG-OS-000354-GPOS-00142, SRG-OS-000358-GPOS-00145, SRG-OS-000365-GPOS-00152, SRG-OS-000392-GPOS-00172, SRG-OS-000475-GPOS-00220

Check

Verify the audit service is configured to produce audit records.

Check that the audit service is installed properly with the following command:

$ sudo yum list installed audit

If the "audit" package is not installed, this is a finding.

Fix

Configure the audit service to produce audit records containing the information needed to establish when (date and time) an event occurred.

Install the audit service (if the audit service is not already installed) with the following command:

$ sudo yum install audit

Successful/unsuccessful uses of the su command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030190 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "su" command allows a user to run commands with a substitute user and group ID.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000064-GPOS-0003, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates audit records when successful/unsuccessful attempts to use the "su" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w /usr/bin/su /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/su -F perm=x -F auid>=1000 -F auid!=unset -k privileged-priv_change

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to generate audit records when successful/unsuccessful attempts to use the "su" command occur by adding or updating the following rule in "/etc/audit/rules.d/audit.rules":

-a always,exit -F path=/usr/bin/su -F perm=x -F auid>=1000 -F auid!=unset -k privileged-priv_change

The audit daemon must be restarted for the changes to take effect.

The RHEL 8 audit system must be configured to audit any usage of the lremovexattr system call.

STIG ID: RHEL-08-030200 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). "Lremovexattr" is a system call that removes extended attributes. This is used for removal of extended attributes from symbolic links.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000463-GPOS-00207, SRG-OS-000468-GPOS-00212, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000466-GPOS-00210

Check

Verify if RHEL 8 is configured to audit the execution of the "lremovexattr" system call, by running the following command:

$ sudo grep -w lremovexattr /etc/audit/audit.rules

-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S lremovexattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S lremovexattr -F auid=0 -k perm_mod

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the "lremovexattr" system call, by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S lremovexattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S lremovexattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S lremovexattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S lremovexattr -F auid=0 -k perm_mod

The audit daemon must be restarted for the changes to take effect.

The RHEL 8 audit system must be configured to audit any usage of the removexattr system call.

STIG ID: RHEL-08-030210 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). "Removexattr" is a system call that removes extended attributes.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000463-GPOS-00207, SRG-OS-000468-GPOS-00212, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000466-GPOS-00210

Check

Verify if RHEL 8 is configured to audit the execution of the "removexattr" system call, by running the following command:

$ sudo grep -w removexattr /etc/audit/audit.rules

-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S removexattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S removexattr -F auid=0 -k perm_mod

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the "removexattr" system call, by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S removexattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S removexattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S removexattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S removexattr -F auid=0 -k perm_mod

The audit daemon must be restarted for the changes to take effect.

The RHEL 8 audit system must be configured to audit any usage of the lsetxattr system call.

STIG ID: RHEL-08-030220 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). "Lsetxattr" is a system call used to set an extended attribute value. This is used to set extended attributes on a symbolic link.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000463-GPOS-00207, SRG-OS-000468-GPOS-00212, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219

Check

Verify if RHEL 8 is configured to audit the execution of the "lsetxattr" system call, by running the following command:

$ sudo grep -w lsetxattr /etc/audit/audit.rules

-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S lsetxattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S lsetxattr -F auid=0 -k perm_mod

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the "lsetxattr" system call, by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S lsetxattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S lsetxattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S lsetxattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S lsetxattr -F auid=0 -k perm_mod

The audit daemon must be restarted for the changes to take effect.

The RHEL 8 audit system must be configured to audit any usage of the fsetxattr system call.

STIG ID: RHEL-08-030230 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). "Fsetxattr" is a system call used to set an extended attribute value. This is used to set extended attributes on a file.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The auid representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000463-GPOS-00207, SRG-OS-000468-GPOS-00212, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219

Check

Verify if RHEL 8 is configured to audit the execution of the "fsetxattr" system call, by running the following command:

$ sudo grep -w fsetxattr /etc/audit/audit.rules

-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S fsetxattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S fsetxattr -F auid=0 -k perm_mod

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the "fsetxattr" system call, by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S fsetxattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fsetxattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S fsetxattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S fsetxattr -F auid=0 -k perm_mod

The audit daemon must be restarted for the changes to take effect.

The RHEL 8 audit system must be configured to audit any usage of the fremovexattr system call.

STIG ID: RHEL-08-030240 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). "Fremovexattr" is a system call that removes extended attributes. This is used for removal of extended attributes from a file.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000463-GPOS-00207, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000466-GPOS-00210

Check

Verify if RHEL 8 is configured to audit the execution of the "fremovexattr" system call, by running the following command:

$ sudo grep -w fremovexattr /etc/audit/audit.rules

-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S fremovexattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S fremovexattr -F auid=0 -k perm_mod

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the "fremovexattr" system call by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fremovexattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S fremovexattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S fremovexattr -F auid=0 -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the chage command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030250 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "chage" command is used to change or view user password expiry information.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000468-GPOS-00212, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "chage" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w chage /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/chage -F perm=x -F auid>=1000 -F auid!=unset -k privileged-chage

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "chage" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/chage -F perm=x -F auid>=1000 -F auid!=unset -k privileged-chage

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the chcon command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030260 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "chcon" command is used to change file SELinux security context.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000468-GPOS-00212, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "chcon" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w chcon /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/chcon -F perm=x -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "chcon" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/chcon -F perm=x -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

The RHEL 8 audit system must be configured to audit any usage of the setxattr system call.

STIG ID: RHEL-08-030270 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). "Setxattr" is a system call used to set an extended attribute value.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify if RHEL 8 is configured to audit the execution of the "setxattr" system call, by running the following command:

$ sudo grep -w setxattr /etc/audit/audit.rules

-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S setxattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S setxattr -F auid=0 -k perm_mod

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the "setxattr" system call, by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S setxattr -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S setxattr -F auid>=1000 -F auid!=unset -k perm_mod

-a always,exit -F arch=b32 -S setxattr -F auid=0 -k perm_mod
-a always,exit -F arch=b64 -S setxattr -F auid=0 -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the ssh-agent in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030280 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "ssh-agent" is a program to hold private keys used for public key authentication.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "ssh-agent" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep ssh-agent /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/ssh-agent -F perm=x -F auid>=1000 -F auid!=unset -k privileged-ssh

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "ssh-agent" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/ssh-agent -F perm=x -F auid>=1000 -F auid!=unset -k privileged-ssh

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the passwd command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030290 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "passwd" command is used to change passwords for user accounts.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "passwd" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w passwd /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/passwd -F perm=x -F auid>=1000 -F auid!=unset -k privileged-passwd

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "passwd" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/passwd -F perm=x -F auid>=1000 -F auid!=unset -k privileged-passwd

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the mount command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030300 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "mount" command is used to mount a filesystem.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "mount" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w /usr/bin/mount /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/mount -F perm=x -F auid>=1000 -F auid!=unset -k privileged-mount

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "mount" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/mount -F perm=x -F auid>=1000 -F auid!=unset -k privileged-mount

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the umount command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030301 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "umount" command is used to unmount a filesystem.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "umount" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w /usr/bin/umount /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/umount -F perm=x -F auid>=1000 -F auid!=unset -k privileged-mount

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "umount" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/umount -F perm=x -F auid>=1000 -F auid!=unset -k privileged-mount

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the mount syscall in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030302 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "mount" syscall is used to mount a filesystem.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "mount" syscall by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "\-S mount" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S mount -F auid>=1000 -F auid!=unset -k privileged-mount
-a always,exit -F arch=b64 -S mount -F auid>=1000 -F auid!=unset -k privileged-mount

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "mount" syscall by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S mount -F auid>=1000 -F auid!=unset -k privileged-mount
-a always,exit -F arch=b64 -S mount -F auid>=1000 -F auid!=unset -k privileged-mount

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the unix_update in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030310 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. "Unix_update" is a helper program for the "pam_unix" module that updates the password for a given user. It is not intended to be run directly from the command line and logs a security violation if done so.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "unix_update" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "unix_update" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/unix_update -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "unix_update" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/unix_update -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of postdrop in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030311 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "postdrop" command creates a file in the maildrop directory and copies its standard input to the file.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of "postdrop" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "postdrop" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/postdrop -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "postdrop" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/postdrop -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of postqueue in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030312 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "postqueue" command implements the Postfix user interface for queue management.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of "postqueue" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "postqueue" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/postqueue -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "postqueue" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/postqueue -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of semanage in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030313 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "semanage" command is used to configure certain elements of SELinux policy without requiring modification to or recompilation from policy sources.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of "semanage" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "semanage" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/semanage -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "semanage" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/semanage -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of setfiles in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030314 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "setfiles" command is primarily used to initialize the security context fields (extended attributes) on one or more filesystems (or parts of them). Usually it is initially run as part of the SELinux installation process (a step commonly known as labeling).

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of "setfiles" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "setfiles" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/setfiles -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "setfiles" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/setfiles -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of userhelper in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030315 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "userhelper" command is not intended to be run interactively. "Userhelper" provides a basic interface to change a user's password, gecos information, and shell. The main difference between this program and its traditional equivalents (passwd, chfn, chsh) is that prompts are written to standard out to make it easy for a graphical user interface wrapper to interface to it as a child process.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of "userhelper" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "userhelper" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/userhelper -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "userhelper" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/userhelper -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of setsebool in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030316 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "setsebool" command sets the current state of a particular SELinux boolean or a list of booleans to a given value.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of "setsebool" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "setsebool" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/setsebool -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "setsebool" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/setsebool -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of unix_chkpwd in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030317 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information.

At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "unix_chkpwd" command is a helper program for the pam_unix module that verifies the password of the current user. It also checks password and account expiration dates in shadow. It is not intended to be run directly from the command line and logs a security violation if done so.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of "unix_chkpwd" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "unix_chkpwd" /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/unix_chkpwd -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "unix_chkpwd" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/unix_chkpwd -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the ssh-keysign in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030320 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "ssh-keysign" program is an SSH helper program for host-based authentication.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "ssh-keysign" by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep ssh-keysign /etc/audit/audit.rules

-a always,exit -F path=/usr/libexec/openssh/ssh-keysign -F perm=x -F auid>=1000 -F auid!=unset -k privileged-ssh

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "ssh-keysign" by adding or updating the following rule in the "/etc/audit/audit.rules" file:

-a always,exit -F path=/usr/libexec/openssh/ssh-keysign -F perm=x -F auid>=1000 -F auid!=unset -k privileged-ssh

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the setfacl command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030330 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "setfacl" command is used to set file access control lists.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "setfacl" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w setfacl /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/setfacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "setfacl" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/setfacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the pam_timestamp_check command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030340 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "pam_timestamp_check" command is used to check if the default timestamp is valid.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "pam_timestamp_check" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w pam_timestamp_check /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/pam_timestamp_check -F perm=x -F auid>=1000 -F auid!=unset -k privileged-pam_timestamp_check

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "pam_timestamp_check" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/pam_timestamp_check -F perm=x -F auid>=1000 -F auid!=unset -k privileged-pam_timestamp_check

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the newgrp command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030350 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "newgrp" command is used to change the current group ID during a login session.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "newgrp" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w newgrp /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/newgrp -F perm=x -F auid>=1000 -F auid!=unset -k priv_cmd

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "newgrp" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/newgrp -F perm=x -F auid>=1000 -F auid!=unset -k priv_cmd

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the init_module command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030360 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "init_module" command is used to load a kernel module.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "init_module" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "init_module" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S init_module -F auid>=1000 -F auid!=unset -k module_chng
-a always,exit -F arch=b64 -S init_module -F auid>=1000 -F auid!=unset -k module_chng

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "init_module" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S init_module -F auid>=1000 -F auid!=unset -k module_chng
-a always,exit -F arch=b64 -S init_module -F auid>=1000 -F auid!=unset -k module_chng

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the rename command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030361 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "rename" command will rename the specified files by replacing the first occurrence of expression in their name by replacement.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "rename" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "rename" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S rename -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S rename -F auid>=1000 -F auid!=unset -k delete

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "rename" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S rename -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S rename -F auid>=1000 -F auid!=unset -k delete

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the renameat command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030362 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "renameat" command renames a file, moving it between directories if required.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "renameat" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "renameat" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S renameat -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S renameat -F auid>=1000 -F auid!=unset -k delete

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "renameat" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S renameat -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S renameat -F auid>=1000 -F auid!=unset -k delete

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the rmdir command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030363 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "rmdir" command removes empty directories.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "rmdir" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "rmdir" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S rmdir -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S rmdir -F auid>=1000 -F auid!=unset -k delete

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "rmdir" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S rmdir -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S rmdir -F auid>=1000 -F auid!=unset -k delete

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the unlink command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030364 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "unlink" command deletes a name from the filesystem. If that name was the last link to a file and no processes have the file open, the file is deleted and the space it was using is made available for reuse.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "unlink" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "unlink" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S unlink -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S unlink -F auid>=1000 -F auid!=unset -k delete

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "unlink" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S unlink -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S unlink -F auid>=1000 -F auid!=unset -k delete

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the unlinkat command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030365 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "unlinkat" system call operates in exactly the same way as either "unlink" or "rmdir" except for the differences described in the manual page.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "unlinkat" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "unlinkat" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S unlinkat -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S unlinkat -F auid>=1000 -F auid!=unset -k delete

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "unlinkat" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S unlinkat -F auid>=1000 -F auid!=unset -k delete
-a always,exit -F arch=b64 -S unlinkat -F auid>=1000 -F auid!=unset -k delete

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the gpasswd command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030370 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "gpasswd" command is used to administer /etc/group and /etc/gshadow. Every group can have administrators, members and a password.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "gpasswd" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w gpasswd /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/gpasswd -F perm=x -F auid>=1000 -F auid!=unset -k privileged-gpasswd

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "gpasswd" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/gpasswd -F perm=x -F auid>=1000 -F auid!=unset -k privileged-gpasswd

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the finit_module command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030380 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "finit_module" command is used to load a kernel module.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "finit_module" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "finit_module" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S finit_module -F auid>=1000 -F auid!=unset -k module_chng
-a always,exit -F arch=b64 -S finit_module -F auid>=1000 -F auid!=unset -k module_chng

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "finit_module" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S finit_module -F auid>=1000 -F auid!=unset -k module_chng
-a always,exit -F arch=b64 -S finit_module -F auid>=1000 -F auid!=unset -k module_chng

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the delete_module command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030390 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "delete_module" command is used to unload a kernel module.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "delete_module" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w "delete_module" /etc/audit/audit.rules

-a always,exit -F arch=b32 -S delete_module -F auid>=1000 -F auid!=unset -k module_chng
-a always,exit -F arch=b64 -S delete_module -F auid>=1000 -F auid!=unset -k module_chng

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "delete_module" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S delete_module -F auid>=1000 -F auid!=unset -k module_chng
-a always,exit -F arch=b64 -S delete_module -F auid>=1000 -F auid!=unset -k module_chng

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the crontab command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030400 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "crontab" command is used to maintain crontab files for individual users. Crontab is the program used to install, remove, or list the tables used to drive the cron daemon. This is similar to the task scheduler used in other operating systems.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "crontab" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w crontab /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/crontab -F perm=x -F auid>=1000 -F auid!=unset -k privileged-crontab

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "crontab" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/crontab -F perm=x -F auid>=1000 -F auid!=unset -k privileged-crontab

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the chsh command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030410 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "chsh" command is used to change the login shell.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "chsh" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w chsh /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/chsh -F perm=x -F auid>=1000 -F auid!=unset -k priv_cmd

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "chsh" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/chsh -F perm=x -F auid>=1000 -F auid!=unset -k priv_cmd

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the truncate command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030420 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "truncate" and "ftruncate" functions are used to truncate a file to a specified length.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "truncate" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -iw truncate /etc/audit/audit.rules

-a always,exit -F arch=b32 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "truncate" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S truncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S truncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the openat system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030430 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "openat" system call opens a file specified by a relative pathname.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "openat" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -iw openat /etc/audit/audit.rules

-a always,exit -F arch=b32 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "openat" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S openat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S openat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the open system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030440 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "open system" call opens a file specified by a pathname. If the specified file does not exist, it may optionally be created by "open".

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "open" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -iw open /etc/audit/audit.rules

-a always,exit -F arch=b32 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "open" system call by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the open_by_handle_at system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030450 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "name_to_handle_at" and "open_by_handle_at" system calls split the functionality of openat into two parts: "name_to_handle_at" returns an opaque handle that corresponds to a specified file; "open_by_handle_at" opens the file corresponding to a handle returned by a previous call to "name_to_handle_at" and returns an open file descriptor.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "open_by_handle_at" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -iw open_by_handle_at /etc/audit/audit.rules

-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "open_by_handle_at" system call by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S open_by_handle_at -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the ftruncate command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030460 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "truncate" and "ftruncate" functions are used to truncate a file to a specified length.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "ftruncate" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -iw ftruncate /etc/audit/audit.rules

-a always,exit -F arch=b32 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "ftruncate" command by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S ftruncate -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S ftruncate -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the creat system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030470 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "creat" system call is used to open and possibly create a file or device.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "creat" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -iw creat /etc/audit/audit.rules

-a always,exit -F arch=b32 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

If the command does not return all lines, or the lines are commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "creat" system call by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F arch=b32 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S creat -F exit=-EPERM -F auid>=1000 -F auid!=unset -k perm_access

-a always,exit -F arch=b32 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access
-a always,exit -F arch=b64 -S creat -F exit=-EACCES -F auid>=1000 -F auid!=unset -k perm_access

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the chown command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030480 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "chown" command is used to change file owner and group.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "chown" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w chown /etc/audit/audit.rules

-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "chown" command by adding or updating the following line to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S chown -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S chown -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the chmod command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030490 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "chmod" command changes the file mode bits of each given file according to mode, which can be either a symbolic representation of changes to make, or an octal number representing the bit pattern for the new mode bits.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "chmod" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w chmod /etc/audit/audit.rules

-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "chmod" command by adding or updating the following line to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S chmod -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S chmod -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the lchown system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030500 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "lchown" system call is used to change the ownership of the file specified by a path, which does not dereference symbolic links.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "lchown" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w lchown /etc/audit/audit.rules

-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "lchown" system call by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S lchown -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S lchown -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the fchownat system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030510 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "fchownat" system call is used to change ownership of a file relative to a directory file descriptor.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "fchownat" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w fchownat /etc/audit/audit.rules

-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "fchownat" system call by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S fchownat -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchownat -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the fchown system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030520 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "fchown" system call is used to change the ownership of a file referred to by the open file descriptor.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "fchown" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w fchown /etc/audit/audit.rules

-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "fchown" system call by adding or updating the following line to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S fchown -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchown -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the fchmodat system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030530 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "fchmodat" system call is used to change permissions of a file relative to a directory file descriptor.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "fchmodat" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w fchmodat /etc/audit/audit.rules

-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "fchmodat" system call by adding or updating the following lines to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S fchmodat -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchmodat -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the fchmod system call in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030540 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "fchmod" system call is used to change permissions of a file.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "fchmod" system call by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w fchmod /etc/audit/audit.rules

-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "fchmod" system call by adding or updating the following line to "/etc/audit/rules.d/audit.rules":

-a always,exit -F arch=b32 -S fchmod -F auid>=1000 -F auid!=unset -k perm_mod
-a always,exit -F arch=b64 -S fchmod -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the sudo command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030550 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "sudo" command allows a permitted user to execute a command as the superuser or another user, as specified by the security policy.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "sudo" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w sudo /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/sudo -F perm=x -F auid>=1000 -F auid!=unset -k priv_cmd

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "sudo" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/sudo -F perm=x -F auid>=1000 -F auid!=unset -k priv_cmd

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the usermod command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030560 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "usermod" command modifies the system account files to reflect the changes that are specified on the command line.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210

Check

Verify that an audit event is generated for any successful/unsuccessful use of the "usermod" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w usermod /etc/audit/audit.rules

-a always,exit -F path=/usr/sbin/usermod -F perm=x -F auid>=1000 -F auid!=unset -k privileged-usermod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "usermod" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/usermod -F perm=x -F auid>=1000 -F auid!=unset -k privileged-usermod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the chacl command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030570 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "chacl" command is used to change the access control list of a file or directory.

When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful attempts to use the "chacl" command by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w chacl /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/chacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_mod

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "chacl" command by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/bin/chacl -F perm=x -F auid>=1000 -F auid!=unset -k perm_mod

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful uses of the kmod command in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030580 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter). The "kmod" command is used to control Linux Kernel modules.

The list of audited events is the set of events for which audits are to be generated. This set of events is typically a subset of the list of all events for which the system is capable of generating audit records.

DoD has defined the list of events for which RHEL 8 will provide an audit record generation capability as the following:

1) Successful and unsuccessful attempts to access, modify, or delete privileges, security objects, security levels, or categories of information (e.g., classification levels);

2) Access actions, such as successful and unsuccessful logon attempts, privileged activities or other system-level access, starting and ending time for user access to the system, concurrent logons from different workstations, successful and unsuccessful accesses to objects, all program initiations, and all direct access to the information system;

3) All account creations, modifications, disabling, and terminations; and

4) All kernel module load, unload, and restart actions.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000471-GPOS-00216, SRG-OS-000477-GPOS-00222

Check

Verify if RHEL 8 is configured to audit the execution of the module management program "kmod", by running the following command:

$ sudo grep "/usr/bin/kmod" /etc/audit/audit.rules

-a always,exit -F path=/usr/bin/kmod -F perm=x -F auid>=1000 -F auid!=unset -k modules

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to audit the execution of the module management program "kmod" by adding or updating the following line to "/etc/audit/rules.d/audit.rules":

-a always,exit -F path=/usr/bin/kmod -F perm=x -F auid>=1000 -F auid!=unset -k modules

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful modifications to the faillock log file in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030590 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

The list of audited events is the set of events for which audits are to be generated. This set of events is typically a subset of the list of all events for which the system is capable of generating audit records.

DoD has defined the list of events for which RHEL 8 will provide an audit record generation capability as the following:

1) Successful and unsuccessful attempts to access, modify, or delete privileges, security objects, security levels, or categories of information (e.g., classification levels);

2) Access actions, such as successful and unsuccessful logon attempts, privileged activities or other system-level access, starting and ending time for user access to the system, concurrent logons from different workstations, successful and unsuccessful accesses to objects, all program initiations, and all direct access to the information system;

3) All account creations, modifications, disabling, and terminations; and

4) All kernel module load, unload, and restart actions.

From "Pam_Faillock man" pages: Note the default directory that pam_faillock uses is usually cleared on system boot so the access will be reenabled after system reboot. If that is undesirable a different tally directory must be set with the "dir" option.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000473-GPOS-00218

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful modifications to the "faillock" file occur. First, determine where the faillock tallies are stored with the following commands:

For RHEL versions 8.0 and 8.1:

$ sudo grep -i pam_faillock.so /etc/pam.d/system-auth

auth required pam_faillock.so preauth dir=/var/log/faillock silent deny=3 fail_interval=900 even_deny_root

For RHEL versions 8.2 and newer:

$ sudo grep dir /etc/security/faillock.conf

dir=/var/log/faillock

Using the location of the faillock log file, check that the following calls are being audited by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w faillock /etc/audit/audit.rules

-w /var/log/faillock -p wa -k logins

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful modifications to the "faillock" file by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-w /var/log/faillock -p wa -k logins

The audit daemon must be restarted for the changes to take effect.

Successful/unsuccessful modifications to the lastlog file in RHEL 8 must generate an audit record.

STIG ID: RHEL-08-030600 | SRG: SRG-OS-000062-GPOS-00031 | Severity: medium | CCI: CCI-000169

Vulnerability Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

The list of audited events is the set of events for which audits are to be generated. This set of events is typically a subset of the list of all events for which the system is capable of generating audit records.

DoD has defined the list of events for which RHEL 8 will provide an audit record generation capability as the following:

1) Successful and unsuccessful attempts to access, modify, or delete privileges, security objects, security levels, or categories of information (e.g., classification levels);

2) Access actions, such as successful and unsuccessful logon attempts, privileged activities or other system-level access, starting and ending time for user access to the system, concurrent logons from different workstations, successful and unsuccessful accesses to objects, all program initiations, and all direct access to the information system;

3) All account creations, modifications, disabling, and terminations; and

4) All kernel module load, unload, and restart actions.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000473-GPOS-00218

Check

Verify RHEL 8 generates an audit record when successful/unsuccessful modifications to the "lastlog" file by performing the following command to check the file system rules in "/etc/audit/audit.rules":

$ sudo grep -w lastlog /etc/audit/audit.rules

-w /var/log/lastlog -p wa -k logins

If the command does not return a line, or the line is commented out, this is a finding.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful modifications to the "lastlog" file by adding or updating the following rules in the "/etc/audit/rules.d/audit.rules" file:

-w /var/log/lastlog -p wa -k logins

The audit daemon must be restarted for the changes to take effect.

RHEL 8 must enable auditing of processes that start prior to the audit daemon.

STIG ID: RHEL-08-030601 | SRG: SRG-OS-000062-GPOS-00031 | Severity: low | CCI: CCI-000169

Vulnerability Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

If auditing is enabled late in the startup process, the actions of some startup processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

The list of audited events is the set of events for which audits are to be generated. This set of events is typically a subset of the list of all events for which the system is capable of generating audit records.

DoD has defined the list of events for which RHEL 8 will provide an audit record generation capability as the following:

1) Successful and unsuccessful attempts to access, modify, or delete privileges, security objects, security levels, or categories of information (e.g., classification levels);

2) Access actions, such as successful and unsuccessful logon attempts, privileged activities or other system-level access, starting and ending time for user access to the system, concurrent logons from different workstations, successful and unsuccessful accesses to objects, all program initiations, and all direct access to the information system;

3) All account creations, modifications, disabling, and terminations; and

4) All kernel module load, unload, and restart actions.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000473-GPOS-00218

Check

Verify RHEL 8 enables auditing of processes that start prior to the audit daemon with the following commands:

$ sudo grub2-editenv - list | grep audit

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 audit=1 audit_backlog_limit=8192 boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If the "audit" entry does not equal "1", is missing, or the line is commented out, this is a finding.

Check that auditing is enabled by default to persist in kernel updates:

$ sudo grep audit /etc/default/grub

GRUB_CMDLINE_LINUX="audit=1"

If "audit" is not set to "1", is missing or commented out, this is a finding.

Fix

Configure RHEL 8 to audit processes that start prior to the audit daemon with the following command:

$ sudo grubby --update-kernel=ALL --args="audit=1"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="audit=1"

RHEL 8 must allocate an audit_backlog_limit of sufficient size to capture processes that start prior to the audit daemon.

STIG ID: RHEL-08-030602 | SRG: SRG-OS-000341-GPOS-00132 | Severity: low | CCI: CCI-001849

Vulnerability Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

If auditing is enabled late in the startup process, the actions of some startup processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

Allocating an audit_backlog_limit of sufficient size is critical in maintaining a stable boot process. With an insufficient limit allocated, the system is susceptible to boot failures and crashes.

Check

Verify RHEL 8 allocates a sufficient audit_backlog_limit to capture processes that start prior to the audit daemon with the following commands:

$ sudo grub2-editenv - list | grep audit

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 audit=1 audit_backlog_limit=8192 boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If the "audit_backlog_limit" entry does not equal "8192", is missing, or the line is commented out, this is a finding.

Check the audit_backlog_limit is set to persist in kernel updates:

$ sudo grep audit /etc/default/grub

GRUB_CMDLINE_LINUX="audit_backlog_limit=8192"

If "audit_backlog_limit" is not set to "8192", is missing or commented out, this is a finding.

Fix

Configure RHEL 8 to allocate sufficient audit_backlog_limit to capture processes that start prior to the audit daemon with the following command:

$ sudo grubby --update-kernel=ALL --args="audit_backlog_limit=8192"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="audit_backlog_limit=8192"

RHEL 8 must enable Linux audit logging for the USBGuard daemon.

STIG ID: RHEL-08-030603 | SRG: SRG-OS-000062-GPOS-00031 | Severity: low | CCI: CCI-000169

Vulnerability Discussion

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

If auditing is enabled late in the startup process, the actions of some startup processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

The list of audited events is the set of events for which audits are to be generated. This set of events is typically a subset of the list of all events for which the system is capable of generating audit records.

DoD has defined the list of events for which RHEL 8 will provide an audit record generation capability as the following:

1) Successful and unsuccessful attempts to access, modify, or delete privileges, security objects, security levels, or categories of information (e.g., classification levels);

2) Access actions, such as successful and unsuccessful logon attempts, privileged activities or other system-level access, starting and ending time for user access to the system, concurrent logons from different workstations, successful and unsuccessful accesses to objects, all program initiations, and all direct access to the information system;

3) All account creations, modifications, disabling, and terminations; and

4) All kernel module load, unload, and restart actions.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000471-GPOS-00215

Check

Verify RHEL 8 enables Linux audit logging of the USBGuard daemon with the following commands:

Note: If the USBGuard daemon is not installed and enabled, this requirement is not applicable.

$ sudo grep -i auditbackend /etc/usbguard/usbguard-daemon.conf

AuditBackend=LinuxAudit

If the "AuditBackend" entry does not equal "LinuxAudit", is missing, or the line is commented out, this is a finding.

Fix

Configure RHEL 8 to enable Linux audit logging of the USBGuad daemon by adding or modifying the following line in "/etc/usbguard/usbguard-daemon.conf":

AuditBackend=LinuxAudit

RHEL 8 must allow only the Information System Security Manager (ISSM) (or individuals or roles appointed by the ISSM) to select which auditable events are to be audited.

STIG ID: RHEL-08-030610 | SRG: SRG-OS-000063-GPOS-00032 | Severity: medium | CCI: CCI-000171

Vulnerability Discussion

Without the capability to restrict the roles and individuals that can select which events are audited, unauthorized personnel may be able to prevent the auditing of critical events. Misconfigured audits may degrade the system's performance by overwhelming the audit log. Misconfigured audits may also make it more difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Check

Verify that the files in directory "/etc/audit/rules.d/" and "/etc/audit/auditd.conf" file have a mode of "0640" or less permissive by using the following commands:

$ sudo ls -al /etc/audit/rules.d/*.rules

-rw-r----- 1 root root 1280 Feb 16 17:09 audit.rules

$ sudo ls -l /etc/audit/auditd.conf

-rw-r----- 1 root root 621 Sep 22 17:19 auditd.conf

If the files in the "/etc/audit/rules.d/" directory or the "/etc/audit/auditd.conf" file have a mode more permissive than "0640", this is a finding.

Fix

Configure the files in directory "/etc/audit/rules.d/" and the "/etc/audit/auditd.conf" file to have a mode of "0640" with the following commands:

$ sudo chmod 0640 /etc/audit/rules.d/audit.rules
$ sudo chmod 0640 /etc/audit/rules.d/[customrulesfile].rules
$ sudo chmod 0640 /etc/audit/auditd.conf

RHEL 8 audit tools must have a mode of 0755 or less permissive.

STIG ID: RHEL-08-030620 | SRG: SRG-OS-000256-GPOS-00097 | Severity: medium | CCI: CCI-001493

Vulnerability Discussion

Protecting audit information also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operation on audit information.

RHEL 8 systems providing tools to interface with audit information will leverage user permissions and roles identifying the user accessing the tools, and the corresponding rights the user enjoys, to make access decisions regarding the access to audit tools.

Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators.

Check

Verify the audit tools are protected from unauthorized access, deletion, or modification by checking the permissive mode.

Check the octal permission of each audit tool by running the following command:

$ sudo stat -c "%a %n" /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/rsyslogd /sbin/augenrules

755 /sbin/auditctl
755 /sbin/aureport
755 /sbin/ausearch
750 /sbin/autrace
755 /sbin/auditd
755 /sbin/rsyslogd
755 /sbin/augenrules

If any of the audit tools has a mode more permissive than "0755", this is a finding.

Fix

Configure the audit tools to be protected from unauthorized access by setting the correct permissive mode using the following command:

$ sudo chmod 0755 [audit_tool]

Replace "[audit_tool]" with the audit tool that does not have the correct permissive mode.

RHEL 8 audit tools must be owned by root.

STIG ID: RHEL-08-030630 | SRG: SRG-OS-000256-GPOS-00097 | Severity: medium | CCI: CCI-001493

Vulnerability Discussion

Check

Verify the audit tools are owned by "root" to prevent any unauthorized access, deletion, or modification.

Check the owner of each audit tool by running the following command:

$ sudo stat -c "%U %n" /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/rsyslog /sbin/augenrules

root /sbin/auditctl
root /sbin/aureport
root /sbin/ausearch
root /sbin/autrace
root /sbin/auditd
root /sbin/rsyslogd
root /sbin/augenrules

If any of the audit tools are not owned by "root", this is a finding.

Fix

Configure the audit tools to be owned by "root", by running the following command:

$ sudo chown root [audit_tool]

Replace "[audit_tool]" with each audit tool not owned by "root".

RHEL 8 audit tools must be group-owned by root.

STIG ID: RHEL-08-030640 | SRG: SRG-OS-000256-GPOS-00097 | Severity: medium | CCI: CCI-001493

Vulnerability Discussion

Check

Verify the audit tools are group-owned by "root" to prevent any unauthorized access, deletion, or modification.

Check the owner of each audit tool by running the following commands:

$ sudo stat -c "%G %n" /sbin/auditctl /sbin/aureport /sbin/ausearch /sbin/autrace /sbin/auditd /sbin/rsyslogd /sbin/augenrules

root /sbin/auditctl
root /sbin/aureport
root /sbin/ausearch
root /sbin/autrace
root /sbin/auditd
root /sbin/rsyslogd
root /sbin/augenrules

If any of the audit tools are not group-owned by "root", this is a finding.

Fix

Configure the audit tools to be group-owned by "root", by running the following command:

$ sudo chgrp root [audit_tool]

Replace "[audit_tool]" with each audit tool not group-owned by "root".

RHEL 8 must use cryptographic mechanisms to protect the integrity of audit tools.

STIG ID: RHEL-08-030650 | SRG: SRG-OS-000278-GPOS-00108 | Severity: medium | CCI: CCI-001496

Vulnerability Discussion

Protecting the integrity of the tools used for auditing purposes is a critical step toward ensuring the integrity of audit information. Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity.

Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators.

It is not uncommon for attackers to replace the audit tools or inject code into the existing tools with the purpose of providing the capability to hide or erase system activity from the audit logs.

To address this risk, audit tools must be cryptographically signed to provide the capability to identify when the audit tools have been modified, manipulated, or replaced. An example is a checksum hash of the file or files.

Check

Verify that Advanced Intrusion Detection Environment (AIDE) is properly configured to use cryptographic mechanisms to protect the integrity of audit tools.

If AIDE is not installed, ask the System Administrator how file integrity checks are performed on the system.

Check the selection lines to ensure AIDE is configured to add/check with the following command:

$ sudo egrep '(\/usr\/sbin\/(audit|au))' /etc/aide.conf

/usr/sbin/auditctl p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/auditd p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/ausearch p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/aureport p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/autrace p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/rsyslogd p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/augenrules p+i+n+u+g+s+b+acl+xattrs+sha512

If any of the audit tools listed above do not have an appropriate selection line, ask the system administrator to indicate what cryptographic mechanisms are being used to protect the integrity of the audit tools. If there is no evidence of integrity protection, this is a finding.

Fix

Add or update the following lines to "/etc/aide.conf", to protect the integrity of the audit tools.

# Audit Tools
/usr/sbin/auditctl p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/auditd p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/ausearch p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/aureport p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/autrace p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/rsyslogd p+i+n+u+g+s+b+acl+xattrs+sha512
/usr/sbin/augenrules p+i+n+u+g+s+b+acl+xattrs+sha512

RHEL 8 must allocate audit record storage capacity to store at least one week of audit records, when audit records are not immediately sent to a central audit record storage facility.

STIG ID: RHEL-08-030660 | SRG: SRG-OS-000341-GPOS-00132 | Severity: medium | CCI: CCI-001849

Vulnerability Discussion

To ensure RHEL 8 systems have a sufficient storage capacity in which to write the audit logs, RHEL 8 needs to be able to allocate audit record storage capacity.

The task of allocating audit record storage capacity is usually performed during initial installation of RHEL 8.

Check

Verify RHEL 8 allocates audit record storage capacity to store at least one week of audit records when audit records are not immediately sent to a central audit record storage facility.

Determine to which partition the audit records are being written with the following command:

$ sudo grep log_file /etc/audit/auditd.conf
log_file = /var/log/audit/audit.log

Check the size of the partition to which audit records are written (with the example being /var/log/audit/) with the following command:

$ sudo df -h /var/log/audit/
/dev/sda2 24G 10.4G 13.6G 43% /var/log/audit

If the audit records are not written to a partition made specifically for audit records (/var/log/audit is a separate partition), determine the amount of space being used by other files in the partition with the following command:

$ sudo du -sh [audit_partition]
1.8G /var/log/audit

If the audit record partition is not allocated for sufficient storage capacity, this is a finding.

Note: The partition size needed to capture a week of audit records is based on the activity level of the system and the total storage capacity available. Typically 10.0 GB of storage space for audit records should be sufficient.

Fix

Allocate enough storage capacity for at least one week of audit records when audit records are not immediately sent to a central audit record storage facility.

If audit records are stored on a partition made specifically for audit records, resize the partition with sufficient space to contain one week of audit records.

If audit records are not stored on a partition made specifically for audit records, a new partition with sufficient space will need be to be created.

RHEL 8 must have the packages required for offloading audit logs installed.

STIG ID: RHEL-08-030670 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Information stored in one location is vulnerable to accidental or incidental deletion or alteration.

Off-loading is a common process in information systems with limited audit storage capacity.

RHEL 8 installation media provides "rsyslogd". "rsyslogd" is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to support both local and remote logging. Couple this utility with "gnutls" (which is a secure communications library implementing the SSL, TLS and DTLS protocols), and you have a method to securely encrypt and off-load auditing.

Rsyslog provides three ways to forward message: the traditional UDP transport, which is extremely lossy but standard; the plain TCP based transport, which loses messages only during certain situations but is widely available; and the RELP transport, which does not lose messages but is currently available only as part of the rsyslogd 3.15.0 and above.
Examples of each configuration:
UDP *.* @remotesystemname
TCP *.* @@remotesystemname
RELP *.* :omrelp:remotesystemname:2514
Note that a port number was given as there is no standard port for RELP.

Check

Verify the operating system has the packages required for offloading audit logs installed with the following commands:

$ sudo yum list installed rsyslog

rsyslog.x86_64 8.1911.0-3.el8 @AppStream

If the "rsyslog" package is not installed, ask the administrator to indicate how audit logs are being offloaded and what packages are installed to support it. If there is no evidence of audit logs being offloaded, this is a finding.

Fix

Configure the operating system to offload audit logs by installing the required packages with the following command:

$ sudo yum install rsyslog

RHEL 8 must have the packages required for encrypting offloaded audit logs installed.

STIG ID: RHEL-08-030680 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the operating system has the packages required for encrypting offloaded audit logs installed with the following commands:

$ sudo yum list installed gnutls

gnutls.x86_64 3.6.8-9.el8 @anaconda

If the "gnutls" package is not installed, ask the administrator to indicate how audit logs are being encrypted during offloading and what packages are installed to support it. If there is no evidence of audit logs being encrypted during offloading, this is a finding.

Fix

Configure the operating system to encrypt offloaded audit logs by installing the required packages with the following command:

$ sudo yum install gnutls

The RHEL 8 audit records must be off-loaded onto a different system or storage media from the system being audited.

STIG ID: RHEL-08-030690 | SRG: SRG-OS-000342-GPOS-00133 | Severity: medium | CCI: CCI-001851

Vulnerability Discussion

Check

Verify the audit system off-loads audit records onto a different system or media from the system being audited with the following command:

$ sudo grep @@ /etc/rsyslog.conf /etc/rsyslog.d/*.conf

/etc/rsyslog.conf:*.* @@[remoteloggingserver]:[port]

If a remote server is not configured, or the line is commented out, ask the System Administrator to indicate how the audit logs are off-loaded to a different system or media.

If there is no evidence that the audit logs are being off-loaded to another system or media, this is a finding.

Fix

Configure the operating system to off-load audit records onto a different system or media from the system being audited by specifying the remote logging server in "/etc/rsyslog.conf" or "/etc/rsyslog.d/[customfile].conf" with the name or IP address of the log aggregation server.

*.* @@[remoteloggingserver]:[port]

RHEL 8 must take appropriate action when the internal event queue is full.

STIG ID: RHEL-08-030700 | SRG: SRG-OS-000342-GPOS-00133 | Severity: medium | CCI: CCI-001851

Vulnerability Discussion

Check

Verify the audit system is configured to take an appropriate action when the internal event queue is full:

$ sudo grep -i overflow_action /etc/audit/auditd.conf

overflow_action = syslog

If the value of the "overflow_action" option is not set to "syslog", "single", "halt", or the line is commented out, ask the System Administrator to indicate how the audit logs are off-loaded to a different system or media.

If there is no evidence that the transfer of the audit logs being off-loaded to another system or media takes appropriate action if the internal event queue becomes full, this is a finding.

Fix

Edit the /etc/audit/auditd.conf file and add or update the "overflow_action" option:

overflow_action = syslog

The audit daemon must be restarted for changes to take effect.

RHEL 8 must encrypt the transfer of audit records off-loaded onto a different system or media from the system being audited.

STIG ID: RHEL-08-030710 | SRG: SRG-OS-000342-GPOS-00133 | Severity: medium | CCI: CCI-001851

Vulnerability Discussion

Check

Verify the operating system encrypts audit records off-loaded onto a different system or media from the system being audited with the following commands:

$ sudo grep -i '$DefaultNetstreamDriver' /etc/rsyslog.conf /etc/rsyslog.d/*.conf

/etc/rsyslog.conf:$DefaultNetstreamDriver gtls

If the value of the "$DefaultNetstreamDriver" option is not set to "gtls" or the line is commented out, this is a finding.

$ sudo grep -i '$ActionSendStreamDriverMode' /etc/rsyslog.conf /etc/rsyslog.d/*.conf

/etc/rsyslog.conf:$ActionSendStreamDriverMode 1

If the value of the "$ActionSendStreamDriverMode" option is not set to "1" or the line is commented out, this is a finding.

If either of the definitions above are set, ask the System Administrator to indicate how the audit logs are off-loaded to a different system or media.

If there is no evidence that the transfer of the audit logs being off-loaded to another system or media is encrypted, this is a finding.

Fix

Configure the operating system to encrypt off-loaded audit records by setting the following options in "/etc/rsyslog.conf" or "/etc/rsyslog.d/[customfile].conf":

$DefaultNetstreamDriver gtls
$ActionSendStreamDriverMode 1

RHEL 8 must authenticate the remote logging server for off-loading audit logs.

STIG ID: RHEL-08-030720 | SRG: SRG-OS-000342-GPOS-00133 | Severity: medium | CCI: CCI-001851

Vulnerability Discussion

Information stored in one location is vulnerable to accidental or incidental deletion or alteration.

Off-loading is a common process in information systems with limited audit storage capacity.

RHEL 8 installation media provides "rsyslogd". "rsyslogd" is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to support both local and remote logging. Couple this utility with "gnutls" (which is a secure communications library implementing the SSL, TLS and DTLS protocols), and you have a method to securely encrypt and off-load auditing.

"Rsyslog" supported authentication modes include:
anon - anonymous authentication
x509/fingerprint - certificate fingerprint authentication
x509/certvalid - certificate validation only
x509/name - certificate validation and subject name authentication.

Satisfies: SRG-OS-000342-GPOS-00133, SRG-OS-000479-GPOS-00224

Check

Verify the operating system authenticates the remote logging server for off-loading audit logs with the following command:

$ sudo grep -i '$ActionSendStreamDriverAuthMode' /etc/rsyslog.conf /etc/rsyslog.d/*.conf

/etc/rsyslog.conf:$ActionSendStreamDriverAuthMode x509/name

If the value of the "$ActionSendStreamDriverAuthMode" option is not set to "x509/name" or the line is commented out, ask the System Administrator to indicate how the audit logs are off-loaded to a different system or media.

If there is no evidence that the transfer of the audit logs being off-loaded to another system or media is encrypted, this is a finding.

Fix

Configure the operating system to authenticate the remote logging server for off-loading audit logs by setting the following option in "/etc/rsyslog.conf" or "/etc/rsyslog.d/[customfile].conf":

$ActionSendStreamDriverAuthMode x509/name

RHEL 8 must notify the System Administrator (SA) and Information System Security Officer (ISSO) (at a minimum) when allocated audit record storage volume reaches 75 percent of the repository maximum audit record storage capacity.

STIG ID: RHEL-08-030730 | SRG: SRG-OS-000343-GPOS-00134 | Severity: medium | CCI: CCI-001855

Vulnerability Discussion

If security personnel are not notified immediately when storage volume reaches 75 percent utilization, they are unable to plan for audit record storage capacity expansion.

Check

Verify RHEL 8 notifies the SA and ISSO (at a minimum) when allocated audit record storage volume reaches 75 percent of the repository maximum audit record storage capacity with the following commands:

$ sudo grep space_left /etc/audit/auditd.conf

space_left = 25%
space_left_action = email

If the value of the "space_left" keyword is not set to "25%" and the "space_left_action" is not set to "email", or if these lines are commented out, ask the System Administrator to indicate how the system is providing real-time alerts to the SA and ISSO.

If there is no evidence that real-time alerts are configured on the system, this is a finding.

Fix

Configure the operating system to initiate an action to notify the SA and ISSO (at a minimum) when allocated audit record storage volume reaches 75 percent of the repository maximum audit record storage capacity by adding/modifying the following lines in the /etc/audit/auditd.conf file.

space_left = 25%
space_left_action = email

Note: Option names and values in the auditd.conf file are case insensitive.

RHEL 8 must securely compare internal information system clocks at least every 24 hours with a server synchronized to an authoritative time source, such as the United States Naval Observatory (USNO) time servers, or a time server designated for the appropriate DoD network (NIPRNet/SIPRNet), and/or the Global Positioning System (GPS).

STIG ID: RHEL-08-030740 | SRG: SRG-OS-000355-GPOS-00143 | Severity: medium | CCI: CCI-001891

Vulnerability Discussion

Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate.

Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network.

Organizations should consider endpoints that may not have regular access to the authoritative time server (e.g., mobile, teleworking, and tactical endpoints).

If time stamps are not consistently applied and there is no common time reference, it is difficult to perform forensic analysis.

Time stamps generated by the operating system include date and time. Time is commonly expressed in Coordinated Universal Time (UTC), a modern continuation of Greenwich Mean Time (GMT), or local time with an offset from UTC.

RHEL 8 utilizes the "timedatectl" command to view the status of the "systemd-timesyncd.service". The "timedatectl" status will display the local time, UTC, and the offset from UTC.

Note that USNO offers authenticated NTP service to DoD and U.S. Government agencies operating on the NIPR and SIPR networks. Visit https://www.usno.navy.mil/USNO/time/ntp/dod-customers for more information.

Satisfies: SRG-OS-000355-GPOS-00143, SRG-OS-000356-GPOS-00144, SRG-OS-000359-GPOS-00146

Check

Verify RHEL 8 is securely comparing internal information system clocks at least every 24 hours with an NTP server with the following commands:

$ sudo grep maxpoll /etc/chrony.conf

server 0.us.pool.ntp.mil iburst maxpoll 16

If the "maxpoll" option is set to a number greater than 16 or the line is commented out, this is a finding.

Verify the "chrony.conf" file is configured to an authoritative DoD time source by running the following command:

$ sudo grep -i server /etc/chrony.conf
server 0.us.pool.ntp.mil

If the parameter "server" is not set or is not set to an authoritative DoD time source, this is a finding.

Fix

Configure the operating system to securely compare internal information system clocks at least every 24 hours with an NTP server by adding/modifying the following line in the /etc/chrony.conf file.

server [ntp.server.name] iburst maxpoll 16

RHEL 8 must disable the chrony daemon from acting as a server.

STIG ID: RHEL-08-030741 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify RHEL 8 disables the chrony daemon from acting as a server with the following command:

$ sudo grep -w 'port' /etc/chrony.conf

port 0

If the "port" option is not set to "0", is commented out or missing, this is a finding.

Fix

Configure the operating system to disable the chrony daemon from acting as a server by adding/modifying the following line in the /etc/chrony.conf file.

port 0

RHEL 8 must disable network management of the chrony daemon.

STIG ID: RHEL-08-030742 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify RHEL 8 disables network management of the chrony daemon with the following command:

$ sudo grep -w 'cmdport' /etc/chrony.conf

cmdport 0

If the "cmdport" option is not set to "0", is commented out or missing, this is a finding.

Fix

Configure the operating system disable network management of the chrony daemon by adding/modifying the following line in the /etc/chrony.conf file.

cmdport 0

RHEL 8 must not have the telnet-server package installed.

STIG ID: RHEL-08-040000 | SRG: SRG-OS-000095-GPOS-00049 | Severity: high | CCI: CCI-000381

Vulnerability Discussion

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors.

Operating systems are capable of providing a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions).

Examples of non-essential capabilities include, but are not limited to, games, software packages, tools, and demonstration software not related to requirements or providing a wide array of functionality not required for every mission, but which cannot be disabled.

Verify the operating system is configured to disable non-essential capabilities. The most secure way of ensuring a non-essential capability is disabled is to not have the capability installed.

The telnet service provides an unencrypted remote access service that does not provide for the confidentiality and integrity of user passwords or the remote session.

If a privileged user were to log on using this service, the privileged user password could be compromised.

Check

Check to see if the telnet-server package is installed with the following command:

$ sudo yum list installed telnet-server

If the telnet-server package is installed, this is a finding.

Fix

Configure the operating system to disable non-essential capabilities by removing the telnet-server package from the system with the following command:

$ sudo yum remove telnet-server

RHEL 8 must not have any automated bug reporting tools installed.

STIG ID: RHEL-08-040001 | SRG: SRG-OS-000095-GPOS-00049 | Severity: medium | CCI: CCI-000381

Vulnerability Discussion

Check

Check to see if any automated bug reporting packages are installed with the following command:

$ sudo yum list installed abrt*

If any automated bug reporting package is installed, this is a finding.

Fix

Configure the operating system to disable non-essential capabilities by removing automated bug reporting packages from the system with the following command:

$ sudo yum remove abrt*

RHEL 8 must not have the sendmail package installed.

STIG ID: RHEL-08-040002 | SRG: SRG-OS-000095-GPOS-00049 | Severity: medium | CCI: CCI-000381

Vulnerability Discussion

Check

Check to see if the sendmail package is installed with the following command:

$ sudo yum list installed sendmail

If the sendmail package is installed, this is a finding.

Fix

Configure the operating system to disable non-essential capabilities by removing the sendmail package from the system with the following command:

$ sudo yum remove sendmail

RHEL 8 must enable mitigations against processor-based vulnerabilities.

STIG ID: RHEL-08-040004 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors.

Operating systems are capable of providing a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions).

Examples of non-essential capabilities include, but are not limited to, games, software packages, tools, and demonstration software not related to requirements or providing a wide array of functionality not required for every mission, but which cannot be disabled.

Verify the operating system is configured to disable non-essential capabilities. The most secure way of ensuring a non-essential capability is disabled is to not have the capability installed.

Kernel page-table isolation is a kernel feature that mitigates the Meltdown security vulnerability and hardens the kernel against attempts to bypass kernel address space layout randomization (KASLR).

Check

Verify RHEL 8 enables kernel page-table isolation with the following commands:

$ sudo grub2-editenv - list | grep pti

kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet fips=1 audit=1 audit_backlog_limit=8192 pti=on boot=UUID=8d171156-cd61-421c-ba41-1c021ac29e82

If the "pti" entry does not equal "on", is missing, or the line is commented out, this is a finding.

Check that kernel page-table isolation is enabled by default to persist in kernel updates:

$ sudo grep audit /etc/default/grub

GRUB_CMDLINE_LINUX="pti=on"

If "pti" is not set to "on", is missing or commented out, this is a finding.

Fix

Configure RHEL 8 to enable kernel page-table isolation with the following command:

$ sudo grubby --update-kernel=ALL --args="pti=on"

Add or modify the following line in "/etc/default/grub" to ensure the configuration survives kernel updates:

GRUB_CMDLINE_LINUX="pti=on"

RHEL 8 must not have the rsh-server package installed.

STIG ID: RHEL-08-040010 | SRG: SRG-OS-000095-GPOS-00049 | Severity: high | CCI: CCI-000381

Vulnerability Discussion

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors.

Operating systems are capable of providing a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions).

The rsh-server service provides an unencrypted remote access service that does not provide for the confidentiality and integrity of user passwords or the remote session and has very weak authentication.

If a privileged user were to log on using this service, the privileged user password could be compromised.

Satisfies: SRG-OS-000095-GPOS-00049, SRG-OS-000074-GPOS-00042

Check

Check to see if the rsh-server package is installed with the following command:

$ sudo yum list installed rsh-server

If the rsh-server package is installed, this is a finding.

Fix

Configure the operating system to disable non-essential capabilities by removing the rsh-server package from the system with the following command:

$ sudo yum remove rsh-server

RHEL 8 must cover or disable the built-in or attached camera when not in use.

STIG ID: RHEL-08-040020 | SRG: SRG-OS-000095-GPOS-00049 | Severity: medium | CCI: CCI-000381

Vulnerability Discussion

Check

If the device or operating system does not have a camera installed, this requirement is not applicable.

This requirement is not applicable to mobile devices (smartphones and tablets), where the use of the camera is a local AO decision.

This requirement is not applicable to dedicated VTC suites located in approved VTC locations that are centrally managed.

For an external camera, if there is not a method for the operator to manually disconnect the camera at the end of collaborative computing sessions, this is a finding.

For a built-in camera, the camera must be protected by a camera cover (e.g., laptop camera cover slide) when not in use. If the built-in camera is not protected with a camera cover, or is not physically disabled, this is a finding.

If the camera is not disconnected, covered, or physically disabled, determine if it is being disabled via software with the following commands:

Determine if the camera is disabled via blacklist with the following command:

$ sudo grep blacklist /etc/modprobe.d/*

/etc/modprobe.d/blacklist.conf:blacklist uvcvideo

Determine if a camera driver is in use with the following command:

$ sudo dmesg | grep -i video

[ 44.630131] ACPI: Video Device [VGA]
[ 46.655714] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/LNXVIDEO:00/input/input7
[ 46.670133] videodev: Linux video capture interface: v2.00
[ 47.226424] uvcvideo: Found UVC 1.00 device WebCam (0402:7675)
[ 47.235752] usbcore: registered new interface driver uvcvideo
[ 47.235756] USB Video Class driver (1.1.1)

If the camera driver blacklist is missing, a camera driver is determined to be in use, and the collaborative computing device has not been authorized for use, this is a finding.

Fix

Configure the operating system to disable the built-in or attached camera when not in use.

First determine the driver being used by the camera with the following command:

$ sudo dmesg | grep -i video

[ 44.630131] ACPI: Video Device [VGA]
[ 46.655714] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/LNXVIDEO:00/input/input7
[ 46.670133] videodev: Linux video capture interface: v2.00
[ 47.226424] uvcvideo: Found UVC 1.00 device WebCam (0402:7675)
[ 47.235752] usbcore: registered new interface driver uvcvideo
[ 47.235756] USB Video Class driver (1.1.1)

Next, build or modify the "/etc/modprobe.d/blacklist.conf" file by using the following example:

##Disable WebCam
blacklist uvcvideo

Reboot the system for the settings to take effect.

RHEL 8 must disable the asynchronous transfer mode (ATM) protocol.

STIG ID: RHEL-08-040021 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify the operating system disables the ability to load the ATM protocol kernel module.

$ sudo grep -ri ATM /etc/modprobe.d/* | grep -i "/bin/true"

install ATM /bin/true

If the command does not return any output, or the line is commented out, and use of the ATM protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use the ATM protocol.

Check to see if the ATM protocol is disabled with the following command:

$ sudo grep -ri ATM /etc/modprobe.d/* | grep -i "blacklist"

blacklist ATM

If the command does not return any output or the output is not "blacklist atm", and use of the ATM protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to use the ATM protocol kernel module.

Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf":

install ATM /bin/true
blacklist ATM

Reboot the system for the settings to take effect.

RHEL 8 must disable the controller area network (CAN) protocol.

STIG ID: RHEL-08-040022 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify the operating system disables the ability to load the CAN protocol kernel module.

$ sudo grep -ri CAN /etc/modprobe.d/* | grep -i "/bin/true"

install CAN /bin/true

If the command does not return any output, or the line is commented out, and use of the CAN protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use the CAN protocol.

Check to see if the CAN protocol is disabled with the following command:

$ sudo grep -ri CAN /etc/modprobe.d/* | grep -i "blacklist"

blacklist CAN

If the command does not return any output or the output is not "blacklist CAN", and use of the CAN protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to use the CAN protocol kernel module.

Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf":

install CAN /bin/true
blacklist CAN

Reboot the system for the settings to take effect.

RHEL 8 must disable the stream control transmission (SCTP) protocol.

STIG ID: RHEL-08-040023 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify the operating system disables the ability to load the SCTP protocol kernel module.

$ sudo grep -ri SCTP /etc/modprobe.d/* | grep -i "/bin/true"

install SCTP /bin/true

If the command does not return any output, or the line is commented out, and use of the SCTP protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use the SCTP protocol.

Check to see if the SCTP protocol is disabled with the following command:

$ sudo grep -ri SCTP /etc/modprobe.d/* | grep -i "blacklist"

blacklist SCTP

If the command does not return any output or the output is not "blacklist SCTP", and use of the SCTP protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to use the SCTP protocol kernel module.

Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf":

install SCTP /bin/true
blacklist SCTP

Reboot the system for the settings to take effect.

RHEL 8 must disable the transparent inter-process communication (TIPC) protocol.

STIG ID: RHEL-08-040024 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify the operating system disables the ability to load the TIPC protocol kernel module.

$ sudo grep -ri TIPC /etc/modprobe.d/* | grep -i "/bin/true"

install TIPC /bin/true

If the command does not return any output, or the line is commented out, and use of the TIPC protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use the TIPC protocol.

Check to see if the TIPC protocol is disabled with the following command:

$ sudo grep -ri TIPC /etc/modprobe.d/* | grep -i "blacklist"

blacklist TIPC

If the command does not return any output or the output is not "blacklist TIPC", and use of the TIPC protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to use the TIPC protocol kernel module.

Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf":

install TIPC /bin/true
blacklist TIPC

Reboot the system for the settings to take effect.

RHEL 8 must disable mounting of cramfs.

STIG ID: RHEL-08-040025 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify the operating system disables the ability to load the cramfs kernel module.

$ sudo grep -ri cramfs /etc/modprobe.d/* | grep -i "/bin/true"

install cramfs /bin/true

If the command does not return any output, or the line is commented out, and use of the cramfs protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use the cramfs kernel module.

Check to see if the cramfs kernel module is disabled with the following command:

$ sudo grep -ri cramfs /etc/modprobe.d/* | grep -i "blacklist"

blacklist cramfs

If the command does not return any output or the output is not "blacklist cramfs", and use of the cramfs kernel module is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to use the cramfs kernel module.

Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf":

install cramfs /bin/true
blacklist cramfs

Reboot the system for the settings to take effect.

RHEL 8 must disable IEEE 1394 (FireWire) Support.

STIG ID: RHEL-08-040026 | SRG: SRG-OS-000095-GPOS-00049 | Severity: low | CCI: CCI-000381

Vulnerability Discussion

Check

Verify the operating system disables the ability to load the firewire-core kernel module.

$ sudo grep -ri firewire-core /etc/modprobe.d/* | grep -i "/bin/true"

install firewire-core /bin/true

If the command does not return any output, or the line is commented out, and use of the firewire-core protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use the firewire-core kernel module.

Check to see if the firewire-core kernel module is disabled with the following command:

$ sudo grep -ri firewire-core /etc/modprobe.d/* | grep -i "blacklist"

blacklist firewire-core

If the command does not return any output or the output is not "blacklist firewire-core", and use of the firewire-core kernel module is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to use the firewire-core kernel module.

Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf":

install firewire-core /bin/true
blacklist firewire-core

Reboot the system for the settings to take effect.

RHEL 8 must be configured to prohibit or restrict the use of functions, ports, protocols, and/or services, as defined in the Ports, Protocols, and Services Management (PPSM) Category Assignments List (CAL) and vulnerability assessments.

STIG ID: RHEL-08-040030 | SRG: SRG-OS-000096-GPOS-00050 | Severity: medium | CCI: CCI-000382

Vulnerability Discussion

To prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports/protocols on information systems.

Operating systems are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., VPN and IPS); however, doing so increases risk over limiting the services provided by any one component.

To support the requirements and principles of least functionality, the operating system must support the organizational requirements, providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved to conduct official business or to address authorized quality-of-life issues.

Check

Inspect the firewall configuration and running services to verify it is configured to prohibit or restrict the use of functions, ports, protocols, and/or services that are unnecessary or prohibited.

Check which services are currently active with the following command:

$ sudo firewall-cmd --list-all-zones

custom (active)
target: DROP
icmp-block-inversion: no
interfaces: ens33
sources:
services: dhcpv6-client dns http https ldaps rpc-bind ssh
ports:
masquerade: no
forward-ports:
icmp-blocks:
rich rules:

Ask the System Administrator for the site or program Ports, Protocols, and Services Management Component Local Service Assessment (PPSM CLSA). Verify the services allowed by the firewall match the PPSM CLSA.

If there are additional ports, protocols, or services that are not in the PPSM CLSA, or there are ports, protocols, or services that are prohibited by the PPSM Category Assurance List (CAL), this is a finding.

Fix

Update the host's firewall settings and/or running services to comply with the PPSM Component Local Service Assessment (CLSA) for the site or program and the PPSM CAL.

The RHEL 8 file system automounter must be disabled unless required.

STIG ID: RHEL-08-040070 | SRG: SRG-OS-000114-GPOS-00059 | Severity: medium | CCI: CCI-000778

Vulnerability Discussion

Automatically mounting file systems permits easy introduction of unknown devices, thereby facilitating malicious activity.

Check

Verify the operating system disables the ability to automount devices.

Check to see if automounter service is active with the following command:

Note: If the autofs service is not installed, this requirement is not applicable.

$ sudo systemctl status autofs

autofs.service - Automounts filesystems on demand
Loaded: loaded (/usr/lib/systemd/system/autofs.service; disabled)
Active: inactive (dead)

If the "autofs" status is set to "active" and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to automount devices.

Turn off the automount service with the following commands:

$ sudo systemctl stop autofs
$ sudo systemctl disable autofs

If "autofs" is required for Network File System (NFS), it must be documented with the ISSO.

RHEL 8 must be configured to disable USB mass storage.

STIG ID: RHEL-08-040080 | SRG: SRG-OS-000114-GPOS-00059 | Severity: medium | CCI: CCI-000778

Vulnerability Discussion

USB mass storage permits easy introduction of unknown devices, thereby facilitating malicious activity.

Satisfies: SRG-OS-000114-GPOS-00059, SRG-OS-000378-GPOS-00163

Check

Verify the operating system disables the ability to load the USB Storage kernel module.

$ sudo grep -r usb-storage /etc/modprobe.d/* | grep -i "/bin/true"

install usb-storage /bin/true

If the command does not return any output, or the line is commented out, and use of USB Storage is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use USB mass storage devices.

Check to see if USB mass storage is disabled with the following command:

$ sudo grep usb-storage /etc/modprobe.d/* | grep -i "blacklist"

blacklist usb-storage

If the command does not return any output or the output is not "blacklist usb-storage", and use of USB storage devices is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure the operating system to disable the ability to use the USB Storage kernel module.

Create a file under "/etc/modprobe.d" with the following command:

$ sudo touch /etc/modprobe.d/usb-storage.conf

Add the following line to the created file:

install usb-storage /bin/true

Configure the operating system to disable the ability to use USB mass storage devices.

$ sudo vi /etc/modprobe.d/blacklist.conf

Add or update the line:

blacklist usb-storage

A RHEL 8 firewall must employ a deny-all, allow-by-exception policy for allowing connections to other systems.

STIG ID: RHEL-08-040090 | SRG: SRG-OS-000297-GPOS-00115 | Severity: medium | CCI: CCI-002314

Vulnerability Discussion

Failure to restrict network connectivity only to authorized systems permits inbound connections from malicious systems. It also permits outbound connections that may facilitate exfiltration of DoD data.

RHEL 8 incorporates the "firewalld" daemon, which allows for many different configurations. One of these configurations is zones. Zones can be utilized to a deny-all, allow-by-exception approach. The default "drop" zone will drop all incoming network packets unless it is explicitly allowed by the configuration file or is related to an outgoing network connection.

Check

Verify "firewalld" is configured to employ a deny-all, allow-by-exception policy for allowing connections to other systems with the following commands:

$ sudo firewall-cmd --state

running

$ sudo firewall-cmd --get-active-zones

[custom]
interfaces: ens33

$ sudo firewall-cmd --info-zone=[custom] | grep target

target: DROP

If no zones are active on the RHEL 8 interfaces or if the target is set to a different option other than "DROP", this is a finding.

Fix

Configure the "firewalld" daemon to employ a deny-all, allow-by-exception with the following commands:

$ sudo firewall-cmd --permanent --new-zone=[custom]

$ sudo cp /usr/lib/firewalld/zones/drop.xml /etc/firewalld/zones/[custom].xml

This will provide a clean configuration file to work with that employs a deny-all approach. Next, add the exceptions that are required for mission functionality.

$ sudo firewall-cmd --set-default-zone=[custom]

Note: This is a runtime and permanent change.

A firewall must be installed on RHEL 8.

STIG ID: RHEL-08-040100 | SRG: SRG-OS-000297-GPOS-00115 | Severity: medium | CCI: CCI-002314

Vulnerability Discussion

"Firewalld" provides an easy and effective way to block/limit remote access to the system via ports, services, and protocols.

Remote access services, such as those providing remote access to network devices and information systems, which lack automated control capabilities, increase risk and make remote user access management difficult at best.

Remote access is access to DoD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

RHEL 8 functionality (e.g., RDP) must be capable of taking enforcement action if the audit reveals unauthorized activity. Automated control of remote access sessions allows organizations to ensure ongoing compliance with remote access policies by enforcing connection rules of remote access applications on a variety of information system components (e.g., servers, workstations, notebook computers, smartphones, and tablets).

Check

Verify that "firewalld" is installed and active with the following commands:

$ sudo yum list installed firewalld

firewalld.noarch 0.7.0-5.el8

$ sudo systemctl is-active firewalld

active

If the "firewalld" package is not installed and "active", ask the System Administrator if another firewall is installed. If no firewall is installed and active this is a finding.

Fix

Install "firewalld" and enable with the following commands:

$ sudo yum install firewalld.noarch

$ sudo systemctl enable firewalld

RHEL 8 wireless network adapters must be disabled.

STIG ID: RHEL-08-040110 | SRG: SRG-OS-000299-GPOS-00117 | Severity: medium | CCI: CCI-001444

Vulnerability Discussion

Without protection of communications with wireless peripherals, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read, altered, or used to compromise the RHEL 8 operating system.

This requirement applies to wireless peripheral technologies (e.g., wireless mice, keyboards, displays, etc.) used with RHEL 8 systems. Wireless peripherals (e.g., Wi-Fi/Bluetooth/IR Keyboards, Mice, and Pointing Devices and Near Field Communications [NFC]) present a unique challenge by creating an open, unsecured port on a computer. Wireless peripherals must meet DoD requirements for wireless data transmission and be approved for use by the Authorizing Official (AO). Even though some wireless peripherals, such as mice and pointing devices, do not ordinarily carry information that need to be protected, modification of communications with these wireless peripherals may be used to compromise the RHEL 8 operating system. Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification.

Protecting the confidentiality and integrity of communications with wireless peripherals can be accomplished by physical means (e.g., employing physical barriers to wireless radio frequencies) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa. If the wireless peripheral is only passing telemetry data, encryption of the data may not be required.

Satisfies: SRG-OS-000299-GPOS-00117, SRG-OS-000300-GPOS-00118, SRG-OS-000481-GPOS-000481

Check

Verify there are no wireless interfaces configured on the system with the following command:

Note: This requirement is Not Applicable for systems that do not have physical wireless network radios.

$ sudo nmcli device status

DEVICE TYPE STATE CONNECTION
virbr0 bridge connected virbr0
wlp7s0 wifi connected wifiSSID
enp6s0 ethernet disconnected --
p2p-dev-wlp7s0 wifi-p2p disconnected --
lo loopback unmanaged --
virbr0-nic tun unmanaged --

If a wireless interface is configured and has not been documented and approved by the Information System Security Officer (ISSO), this is a finding.

Fix

Configure the system to disable all wireless network interfaces with the following command:

$ sudo nmcli radio all off

RHEL 8 Bluetooth must be disabled.

STIG ID: RHEL-08-040111 | SRG: SRG-OS-000300-GPOS-00118 | Severity: medium | CCI: CCI-001443

Vulnerability Discussion

Check

If the device or operating system does not have a Bluetooth adapter installed, this requirement is not applicable.

This requirement is not applicable to mobile devices (smartphones and tablets), where the use of Bluetooth is a local AO decision.

Determine if Bluetooth is disabled with the following command:

$ sudo grep bluetooth /etc/modprobe.d/*

/etc/modprobe.d/bluetooth.conf:install bluetooth /bin/true

If the Bluetooth driver blacklist entry is missing, a Bluetooth driver is determined to be in use, and the collaborative computing device has not been authorized for use, this is a finding.

Fix

Configure the operating system to disable the Bluetooth adapter when not in use.

Build or modify the "/etc/modprobe.d/bluetooth.conf" file with the following line:

install bluetooth /bin/true

Reboot the system for the settings to take effect.

RHEL 8 must mount /dev/shm with the nodev option.

STIG ID: RHEL-08-040120 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

The organization must identify authorized software programs and permit execution of authorized software. The process used to identify software programs that are authorized to execute on organizational information systems is commonly referred to as whitelisting.

The "noexec" mount option causes the system to not execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

The "nosuid" mount option causes the system to not execute "setuid" and "setgid" files with owner privileges. This option must be used for mounting any file system not containing approved "setuid" and "setguid" files. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

Check

Verify "/dev/shm" is mounted with the "nodev" option:

$ sudo mount | grep /dev/shm

tmpfs on /dev/shm type tmpfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nodev"option is configured for /dev/shm:

$ sudo cat /etc/fstab | grep /dev/shm

tmpfs /dev/shm tmpfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nodev" option is missing, or if /dev/shm is mounted without the "nodev" option, this is a finding.

Fix

Configure the system so that /dev/shm is mounted with the "nodev" option by adding /modifying the /etc/fstab with the following line:

tmpfs /dev/shm tmpfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /dev/shm with the nosuid option.

STIG ID: RHEL-08-040121 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

The organization must identify authorized software programs and permit execution of authorized software. The process used to identify software programs that are authorized to execute on organizational information systems is commonly referred to as whitelisting.

The "noexec" mount option causes the system to not execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.
The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.
The "nosuid" mount option causes the system to not execute "setuid" and "setgid" files with owner privileges. This option must be used for mounting any file system not containing approved "setuid" and "setguid" files. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

Check

Verify "/dev/shm" is mounted with the "nosuid" option:

$ sudo mount | grep /dev/shm

tmpfs on /dev/shm type tmpfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nosuid" option is configured for /dev/shm:

$ sudo cat /etc/fstab | grep /dev/shm

tmpfs /dev/shm tmpfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nosuid" option is missing, or if /dev/shm is mounted without the "nosuid" option, this is a finding.

Fix

Configure the system so that /dev/shm is mounted with the "nosuid" option by adding /modifying the /etc/fstab with the following line:

tmpfs /dev/shm tmpfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /dev/shm with the noexec option.

STIG ID: RHEL-08-040122 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/dev/shm" is mounted with the "noexec" option:

$ sudo mount | grep /dev/shm

tmpfs on /dev/shm type tmpfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "noexec" options is configured for /dev/shm:

$ sudo cat /etc/fstab | grep /dev/shm

tmpfs /dev/shm tmpfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "noexec" option is missing, or if /dev/shm is mounted without the "noexec" option, this is a finding.

Fix

Configure the system so that /dev/shm is mounted with the "noexec" option by adding /modifying the /etc/fstab with the following line:

tmpfs /dev/shm tmpfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /tmp with the nodev option.

STIG ID: RHEL-08-040123 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/tmp" is mounted with the "nodev" option:

$ sudo mount | grep /tmp

/dev/mapper/rhel-tmp on /tmp type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nodev" option is configured for /tmp:

$ sudo cat /etc/fstab | grep /tmp

/dev/mapper/rhel-tmp /tmp xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nodev" option is missing, or if /tmp is mounted without the "nodev" option, this is a finding.

Fix

Configure the system so that /tmp is mounted with the "nodev" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-tmp /tmp xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /tmp with the nosuid option.

STIG ID: RHEL-08-040124 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

The organization must identify authorized software programs and permit execution of authorized software. The process used to identify software programs that are authorized to execute on organizational information systems is commonly referred to as whitelisting.

The "noexec" mount option causes the system to not execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.
The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.
The "nosuid" mount option causes the system to not execute "setuid" and "setgid" files with owner privileges. This option must be used for mounting any file system not containing approved "setuid" and "setguid" files. Executing files from untrusted file systems increases the opportunity for unprivileged users to attain unauthorized administrative access.

Check

Verify "/tmp" is mounted with the "nosuid" option:

$ sudo mount | grep /tmp

/dev/mapper/rhel-tmp on /tmp type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nosuid" option is configured for /tmp:

$ sudo cat /etc/fstab | grep /tmp

/dev/mapper/rhel-tmp /tmp xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nosuid" option is missing, or if /tmp is mounted without the "nosuid" option, this is a finding.

Fix

Configure the system so that /tmp is mounted with the "nosuid" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-tmp /tmp xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /tmp with the noexec option.

STIG ID: RHEL-08-040125 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/tmp" is mounted with the "noexec" option:

$ sudo mount | grep /tmp

/dev/mapper/rhel-tmp on /tmp type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "noexec" option is configured for /tmp:

$ sudo cat /etc/fstab | grep /tmp

/dev/mapper/rhel-tmp /tmp xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "noexec" option is missing, or if /tmp is mounted without the "noexec" option, this is a finding.

Fix

Configure the system so that /tmp is mounted with the "noexec" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-tmp /tmp xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/log with the nodev option.

STIG ID: RHEL-08-040126 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/log" is mounted with the "nodev" option:

$ sudo mount | grep /var/log

/dev/mapper/rhel-var-log on /var/log type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nodev" option is configured for /var/log:

$ sudo cat /etc/fstab | grep /var/log

/dev/mapper/rhel-var-log /var/log xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nodev" option is missing, or if /var/log is mounted without the "nodev" option, this is a finding.

Fix

Configure the system so that /var/log is mounted with the "nodev" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log /var/log xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/log with the nosuid option.

STIG ID: RHEL-08-040127 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/log" is mounted with the "nosuid" option:

$ sudo mount | grep /var/log

/dev/mapper/rhel-var-log on /var/log type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nosuid" option is configured for /var/log:

$ sudo cat /etc/fstab | grep /var/log

/dev/mapper/rhel-var-log /var/log xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nosuid" option is missing, or if /var/log is mounted without the "nosuid" option, this is a finding.

Fix

Configure the system so that /var/log is mounted with the "nosuid" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log /var/log xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/log with the noexec option.

STIG ID: RHEL-08-040128 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/log" is mounted with the "noexec" option:

$ sudo mount | grep /var/log

/dev/mapper/rhel-var-log on /var/log type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "noexec" option is configured for /var/log:

$ sudo cat /etc/fstab | grep /var/log

/dev/mapper/rhel-var-log /var/log xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "noexec" option is missing, or if /var/log is mounted without the "noexec" option, this is a finding.

Fix

Configure the system so that /var/log is mounted with the "noexec" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log /var/log xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/log/audit with the nodev option.

STIG ID: RHEL-08-040129 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/log/audit" is mounted with the "nodev" option:

$ sudo mount | grep /var/log/audit

/dev/mapper/rhel-var-log-audit on /var/log/audit type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nodev" option is configured for /var/log/audit:

$ sudo cat /etc/fstab | grep /var/log/audit

/dev/mapper/rhel-var-log-audit /var/log/audit xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nodev" option is missing, or if /var/log/audit is mounted without the "nodev" option, this is a finding.

Fix

Configure the system so that /var/log/audit is mounted with the "nodev" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log-audit /var/log/audit xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/log/audit with the nosuid option.

STIG ID: RHEL-08-040130 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/log/audit" is mounted with the "nosuid" option:

$ sudo mount | grep /var/log/audit

/dev/mapper/rhel-var-log-audit on /var/log/audit type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nosuid" option is configured for /var/log/audit:

$ sudo cat /etc/fstab | grep /var/log/audit

/dev/mapper/rhel-var-log-audit /var/log/audit xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nosuid" option is missing, or if /var/log/audit is mounted without the "nosuid" option, this is a finding.

Fix

Configure the system so that /var/log/audit is mounted with the "nosuid" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log-audit /var/log/audit xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/log/audit with the noexec option.

STIG ID: RHEL-08-040131 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/log/audit" is mounted with the "noexec" option:

$ sudo mount | grep /var/log/audit

/dev/mapper/rhel-var-log-audit on /var/log/audit type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "noexec" option is configured for /var/log/audit:

$ sudo cat /etc/fstab | grep /var/log/audit

/dev/mapper/rhel-var-log-audit /var/log/audit xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "noexec" option is missing, or if /var/log/audit is mounted without the "noexec" option, this is a finding.

Fix

Configure the system so that /var/log/audit is mounted with the "noexec" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log-audit /var/log/audit xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/tmp with the nodev option.

STIG ID: RHEL-08-040132 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/tmp" is mounted with the "nodev" option:

$ sudo mount | grep /var/tmp

/dev/mapper/rhel-var-log-audit on /var/tmp type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nodev" option is configured for /var/tmp:

$ sudo cat /etc/fstab | grep /var/tmp

/dev/mapper/rhel-var-log-audit /var/tmp xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nodev" option is missing, or if /var/tmp is mounted without the "nodev" option, this is a finding.

Fix

Configure the system so that /var/tmp is mounted with the "nodev" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log-audit /var/tmp xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/tmp with the nosuid option.

STIG ID: RHEL-08-040133 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/tmp" is mounted with the "nosuid" option:

$ sudo mount | grep /var/tmp

/dev/mapper/rhel-var-log-audit on /var/tmp type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "nosuid" option is configured for /var/tmp:

$ sudo cat /etc/fstab | grep /var/tmp

/dev/mapper/rhel-var-log-audit /var/tmp xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "nosuid" option is missing, or if /var/tmp is mounted without the "nosuid" option, this is a finding.

Fix

Configure the system so that /var/tmp is mounted with the "nosuid" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log-audit /var/tmp xfs defaults,nodev,nosuid,noexec 0 0

RHEL 8 must mount /var/tmp with the noexec option.

STIG ID: RHEL-08-040134 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

Check

Verify "/var/tmp" is mounted with the "noexec" option:

$ sudo mount | grep /var/tmp

/dev/mapper/rhel-var-log-audit on /var/tmp type xfs (rw,nodev,nosuid,noexec,seclabel)

Verify that the "noexec" option is configured for /var/tmp:

$ sudo cat /etc/fstab | grep /var/tmp

/dev/mapper/rhel-var-log-audit /var/tmp xfs defaults,nodev,nosuid,noexec 0 0

If results are returned and the "noexec" option is missing, or if /var/tmp is mounted without the "noexec" option, this is a finding.

Fix

Configure the system so that /var/tmp is mounted with the "noexec" option by adding /modifying the /etc/fstab with the following line:

/dev/mapper/rhel-var-log-audit /var/tmp xfs defaults,nodev,nosuid,noexec 0 0

The RHEL 8 fapolicy module must be configured to employ a deny-all, permit-by-exception policy to allow the execution of authorized software programs.

STIG ID: RHEL-08-040135 | SRG: SRG-OS-000368-GPOS-00154 | Severity: medium | CCI: CCI-001764

Vulnerability Discussion

The organization must identify authorized software programs and permit execution of authorized software. The process used to identify software programs that are authorized to execute on organizational information systems is commonly referred to as whitelisting.

Utilizing a whitelist provides a configuration management method for allowing the execution of only authorized software. Using only authorized software decreases risk by limiting the number of potential vulnerabilities. Verification of whitelisted software occurs prior to execution or at system startup.

User home directories/folders may contain information of a sensitive nature. Non-privileged users should coordinate any sharing of information with an SA through shared resources.

RHEL 8 ships with many optional packages. One such package is a file access policy daemon called "fapolicyd". "fapolicyd" is a userspace daemon that determines access rights to files based on attributes of the process and file. It can be used to either blacklist or whitelist processes or file access.

Proceed with caution with enforcing the use of this daemon. Improper configuration may render the system non-functional.

Satisfies: SRG-OS-000368-GPOS-00154, SRG-OS-000370-GPOS-00155, SRG-OS-000480-GPOS-00232

Check

Verify the RHEL 8 "fapolicyd" is enabled and employs a deny-all, permit-by-exception policy.

Check that "fapolicyd" is installed, running, and in enforcing mode with the following commands:

$ sudo yum list installed fapolicyd

Installed Packages
fapolicyd.x86_64

$ sudo systemctl status fapolicyd.service

fapolicyd.service - File Access Policy Daemon
Loaded: loaded (/usr/lib/systemd/system/fapolicyd.service; enabled; vendor preset: disabled)
Active: active (running)

$ sudo grep permissive /etc/fapolicyd/fapolicyd.conf

permissive = 0

Check that fapolicyd employs a deny-all policy on system mounts with the following commands:

$ sudo tail /etc/fapolicyd/fapolicyd.rules

allow exe=/usr/bin/python3.4 dir=execdirs ftype=text/x-pyton
deny_audit pattern ld_so all
deny all all

$ sudo cat /etc/fapolicyd/fapolicyd.mounts

/dev/shm
/run
/sys/fs/cgroup
/
/home
/boot
/run/user/42
/run/user/1000

If fapolicyd is not running in enforcement mode on all system mounts with a deny-all, permit-by-exception policy, this is a finding.

Fix

Configure RHEL 8 to employ a deny-all, permit-by-exception application whitelisting policy with "fapolicyd" using the following commands:

Install and enable "fapolicyd":

$ sudo yum install fapolicyd.x86_64

$ sudo mount | egrep '^tmpfs| ext4| ext3| xfs' | awk '{ printf "%s\n", $3 }' >> /etc/fapolicyd/fapolicyd.mounts

$ sudo systemctl enable --now fapolicyd

With the "fapolicyd" installed and enabled, configure the daemon to function in permissive mode until the whitelist is built correctly to avoid system lockout. Do this by editing the "/etc/fapolicyd/fapolicyd.conf" file with the following line:

permissive = 1

Build the whitelist in the "/etc/fapolicyd/fapolicyd.rules" file ensuring the last rule is "deny all all".

Once it is determined the whitelist is built correctly, set the fapolicyd to enforcing mode by editing the "permissive" line in the /etc/fapolicyd/fapolicyd.conf file.

permissive = 0

RHEL 8 must block unauthorized peripherals before establishing a connection.

STIG ID: RHEL-08-040140 | SRG: SRG-OS-000378-GPOS-00163 | Severity: medium | CCI: CCI-001958

Vulnerability Discussion

Without authenticating devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity.

Peripherals include, but are not limited to, such devices as flash drives, external storage, and printers.

A new feature that RHEL 8 provides is the USBGuard software framework. The USBguard-daemon is the main component of the USBGuard software framework. It runs as a service in the background and enforces the USB device authorization policy for all USB devices. The policy is defined by a set of rules using a rule language described in the usbguard-rules.conf file. The policy and the authorization state of USB devices can be modified during runtime using the usbguard tool.

The System Administrator (SA) must work with the site Information System Security Officer (ISSO) to determine a list of authorized peripherals and establish rules within the USBGuard software framework to allow only authorized devices.

Check

Verify the operating system has enabled the use of USBGuard with the following command:

$ sudo systemctl status usbguard.service

usbguard.service - USBGuard daemon
Loaded: loaded (/usr/lib/systemd/system/usbguard.service; enabled; vendor preset: disabled)
Active: active (running)

If the usbguard.service is not installed and active, ask the SA to indicate how unauthorized peripherals are being blocked.

If there is no evidence that unauthorized peripherals can be blocked before establishing a connection, this is a finding.

Fix

Configure the operating system to enable the blocking of unauthorized peripherals with the following commands:

$ sudo yum install usbguard.x86_64

$ sudo usbguard generate-policy > /etc/usbguard/rules.conf

$ sudo systemctl enable usbguard.service

$ sudo systemctl start usbguard.service

Note: Enabling and starting usbguard without properly configuring it for an individual system will immediately prevent any access over a usb device such as a keyboard or mouse

A firewall must be able to protect against or limit the effects of Denial of Service (DoS) attacks by ensuring RHEL 8 can implement rate-limiting measures on impacted network interfaces.

STIG ID: RHEL-08-040150 | SRG: SRG-OS-000420-GPOS-00186 | Severity: medium | CCI: CCI-002385

Vulnerability Discussion

DoS is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity.

This requirement addresses the configuration of RHEL 8 to mitigate the impact of DoS attacks that have occurred or are ongoing on system availability. For each system, known and potential DoS attacks must be identified and solutions for each type implemented. A variety of technologies exists to limit or, in some cases, eliminate the effects of DoS attacks (e.g., limiting processes or establishing memory partitions). Employing increased capacity and bandwidth, combined with service redundancy, may reduce the susceptibility to some DoS attacks.

Since version 0.6.0, "firewalld" has incorporated "nftables" as its backend support. Utilizing the limit statement in "nftables" can help to mitigate DoS attacks.

Check

Verify "nftables" is configured to allow rate limits on any connection to the system with the following commands:

Check that the "nftables.service" is active and running:

$ sudo systemctl status nftables.service

nftables.service - Netfilter Tables
Loaded: loaded (/usr/lib/systemd/system/nftables.service; enabled; vendor preset: disabled)
Active: active (running)

Verify "firewalld" has "nftables" set as the default backend:

$ sudo grep -i firewallbackend /etc/firewalld/firewalld.conf

# FirewallBackend
FirewallBackend=nftables

If the "nftables" is not active, running and set as the "firewallbackend" default, this is a finding.

Fix

Install "nftables" packages onto the host with the following commands:

$ sudo yum install nftables.x86_64 1:0.9.0-14.el8

Configure the "nftables" service to automatically start after reboot with the following command:

$ sudo systemctl enable nftables.service

Configure "nftables" to be the default "firewallbackend" for "firewalld" by adding or editing the following line in "etc/firewalld/firewalld.conf":

FirewallBackend=nftables

Establish rate-limiting rules based on organization-defined types of DoS attacks on impacted network interfaces.

All RHEL 8 networked systems must have and implement SSH to protect the confidentiality and integrity of transmitted and received information, as well as information during preparation for transmission.

STIG ID: RHEL-08-040160 | SRG: SRG-OS-000423-GPOS-00187 | Severity: medium | CCI: CCI-002418

Vulnerability Discussion

Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read or altered.

This requirement applies to both internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification.

Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa.

Satisfies: SRG-OS-000423-GPOS-00187, SRG-OS-000424-GPOS-00188, SRG-OS-000425-GPOS-00189, SRG-OS-000426-GPOS-00190

Check

Verify SSH is loaded and active with the following command:

$ sudo systemctl status sshd

sshd.service - OpenSSH server daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled)
Active: active (running) since Tue 2015-11-17 15:17:22 EST; 4 weeks 0 days ago
Main PID: 1348 (sshd)
CGroup: /system.slice/sshd.service
1053 /usr/sbin/sshd -D

If "sshd" does not show a status of "active" and "running", this is a finding.

If the "SSH server" package is not installed, this is a finding.

Fix

Install SSH packages onto the host with the following commands:

$ sudo yum install openssh-server.x86_64

Configure the SSH service to automatically start after reboot with the following command:

$ sudo systemctl enable sshd.service

RHEL 8 must force a frequent session key renegotiation for SSH connections to the server.

STIG ID: RHEL-08-040161 | SRG: SRG-OS-000033-GPOS-00014 | Severity: medium | CCI: CCI-000068

Vulnerability Discussion

Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read or altered.

This requirement applies to both internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification.

Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa.

Session key regeneration limits the chances of a session key becoming compromised.

Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000420-GPOS-00186, SRG-OS-000424-GPOS-00188

Check

Verify the SSH server is configured to force frequent session key renegotiation with the following command:

$ sudo grep -i RekeyLimit /etc/ssh/sshd_config

RekeyLimit 1G 1h

If "RekeyLimit" does not have a maximum data amount and maximum time defined, is missing or commented out, this is a finding.

Fix

Configure the system to force a frequent session key renegotiation for SSH connections to the server by add or modifying the following line in the "/etc/ssh/sshd_config" file:

RekeyLimit 1G 1h

Restart the SSH daemon for the settings to take effect.

$ sudo systemctl restart sshd.service

RHEL 8 must force a frequent session key renegotiation for SSH connections by the client.

STIG ID: RHEL-08-040162 | SRG: SRG-OS-000033-GPOS-00014 | Severity: medium | CCI: CCI-000068

Vulnerability Discussion

Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read or altered.

This requirement applies to both internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification.

Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa.

Session key regeneration limits the chances of a session key becoming compromised.

Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000420-GPOS-00186, SRG-OS-000424-GPOS-00188

Check

Verify the SSH client is configured to force frequent session key renegotiation with the following command:

$ sudo grep -i RekeyLimit /etc/ssh/ssh_config

RekeyLimit 1G 1h

If "RekeyLimit" does not have a maximum data amount and maximum time defined, is missing or commented out, this is a finding.

Fix

Configure the system to force a frequent session key renegotiation for SSH connections by the client by add or modifying the following line in the "/etc/ssh/ssh_config" file:

RekeyLimit 1G 1h

Restart the SSH daemon for the settings to take effect.

$ sudo systemctl restart sshd.service

The x86 Ctrl-Alt-Delete key sequence must be disabled on RHEL 8.

STIG ID: RHEL-08-040170 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

A locally logged-on user, who presses Ctrl-Alt-Delete when at the console, can reboot the system. If accidentally pressed, as could happen in the case of a mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. In a graphical user environment, risk of unintentional reboot from the Ctrl-Alt-Delete sequence is reduced because the user will be prompted before any action is taken.

Check

Verify RHEL 8 is not configured to reboot the system when Ctrl-Alt-Delete is pressed with the following command:

$ sudo systemctl status ctrl-alt-del.target

ctrl-alt-del.target
Loaded: masked (Reason: Unit ctrl-alt-del.target is masked.)
Active: inactive (dead)

If the "ctrl-alt-del.target" is loaded and not masked, this is a finding.

Fix

Configure the system to disable the Ctrl-Alt-Delete sequence for the command line with the following command:

$ sudo systemctl mask ctrl-alt-del.target

Created symlink /etc/systemd/system/ctrl-alt-del.target -> /dev/null

Reload the daemon for this change to take effect.

$ sudo systemctl daemon-reload

The x86 Ctrl-Alt-Delete key sequence in RHEL 8 must be disabled if a graphical user interface is installed.

STIG ID: RHEL-08-040171 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

A locally logged-on user, who presses Ctrl-Alt-Delete, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of a mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. In a graphical user environment, risk of unintentional reboot from the Ctrl-Alt-Delete sequence is reduced because the user will be prompted before any action is taken.

Check

Verify RHEL 8 is not configured to reboot the system when Ctrl-Alt-Delete is pressed when using a graphical user interface with the following command:

This requirement assumes the use of the RHEL 8 default graphical user interface, Gnome Shell. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

$ sudo grep logout /etc/dconf/db/local.d/*

logout=''

If the "logout" key is bound to an action, is commented out, or is missing, this is a finding.

Fix

Configure the system to disable the Ctrl-Alt-Delete sequence when using a graphical user interface by creating or editing the /etc/dconf/db/local.d/00-disable-CAD file.

Add the setting to disable the Ctrl-Alt-Delete sequence for a graphical user interface:

[org/gnome/settings-daemon/plugins/media-keys]
logout=''

Note: The value above is set to two single quotations.

Then update the dconf settings:

$ sudo dconf update

The systemd Ctrl-Alt-Delete burst key sequence in RHEL 8 must be disabled.

STIG ID: RHEL-08-040172 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

A locally logged-on user who presses Ctrl-Alt-Delete when at the console can reboot the system. If accidentally pressed, as could happen in the case of a mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. In a graphical user environment, risk of unintentional reboot from the Ctrl-Alt-Delete sequence is reduced because the user will be prompted before any action is taken.

Check

Verify RHEL 8 is not configured to reboot the system when Ctrl-Alt-Delete is pressed seven times within two seconds with the following command:

$ sudo grep -i ctrl /etc/systemd/system.conf

CtrlAltDelBurstAction=none

If the "CtrlAltDelBurstAction" is not set to "none", commented out, or is missing, this is a finding.

Fix

Configure the system to disable the CtrlAltDelBurstAction by added or modifying the following line in the "/etc/systemd/system.conf" configuration file:

CtrlAltDelBurstAction=none

Reload the daemon for this change to take effect.

$ sudo systemctl daemon-reload

The debug-shell systemd service must be disabled on RHEL 8.

STIG ID: RHEL-08-040180 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The debug-shell requires no authentication and provides root privileges to anyone who has physical access to the machine. While this feature is disabled by default, masking it adds an additional layer of assurance that it will not be enabled via a dependency in systemd. This also prevents attackers with physical access from trivially bypassing security on the machine through valid troubleshooting configurations and gaining root access when the system is rebooted.

Check

Verify RHEL 8 is configured to mask the debug-shell systemd service with the following command:

$ sudo systemctl status debug-shell.service

debug-shell.service
Loaded: masked (Reason: Unit debug-shell.service is masked.)
Active: inactive (dead)

If the "debug-shell.service" is loaded and not masked, this is a finding.

Fix

Configure the system to mask the debug-shell systemd service with the following command:

$ sudo systemctl mask debug-shell.service

Created symlink /etc/systemd/system/debug-shell.service -> /dev/null

Reload the daemon to take effect.

$ sudo systemctl daemon-reload

The Trivial File Transfer Protocol (TFTP) server package must not be installed if not required for RHEL 8 operational support.

STIG ID: RHEL-08-040190 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

If TFTP is required for operational support (such as the transmission of router configurations) its use must be documented with the Information System Security Officer (ISSO), restricted to only authorized personnel, and have access control rules established.

Check

Verify a TFTP server has not been installed on the system with the following command:

$ sudo yum list installed tftp-server

tftp-server.x86_64 5.2-24.el8

If TFTP is installed and the requirement for TFTP is not documented with the ISSO, this is a finding.

Fix

Remove the TFTP package from the system with the following command:

$ sudo yum remove tftp-server

The root account must be the only account having unrestricted access to the RHEL 8 system.

STIG ID: RHEL-08-040200 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

If an account other than root also has a User Identifier (UID) of "0", it has root authority, giving that account unrestricted access to the entire operating system. Multiple accounts with a UID of "0" afford an opportunity for potential intruders to guess a password for a privileged account.

Check

Check the system for duplicate UID "0" assignments with the following command:

$ sudo awk -F: '$3 == 0 {print $1}' /etc/passwd

If any accounts other than root have a UID of "0", this is a finding.

Fix

Change the UID of any account on the system, other than root, that has a UID of "0".

If the account is associated with system commands or applications, the UID should be changed to one greater than "0" but less than "1000". Otherwise, assign a UID of greater than "1000" that has not already been assigned.

RHEL 8 must prevent Internet Control Message Protocol (ICMP) redirect messages from being accepted.

STIG ID: RHEL-08-040210 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.

Check

Verify RHEL 8 will not accept ICMP redirect messages.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check the value of the default "accept_redirects" variables with the following command:

$ sudo sysctl net.ipv4.conf.default.accept_redirects net.ipv6.conf.default.accept_redirects

net.ipv4.conf.default.accept_redirects = 0
net.ipv6.conf.default.accept_redirects = 0

If the returned lines do not have a value of "0", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to prevent ICMP redirect messages from being accepted with the following command:

$ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0

$ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0

If "0" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.default.accept_redirects=0

net.ipv6.conf.default.accept_redirects=0

RHEL 8 must not send Internet Control Message Protocol (ICMP) redirects.

STIG ID: RHEL-08-040220 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table, possibly revealing portions of the network topology.

There are notable differences between Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). There is only a directive to disable sending of IPv4 redirected packets. Refer to RFC4294 for an explanation of "IPv6 Node Requirements", which resulted in this difference between IPv4 and IPv6.

Check

Verify RHEL 8 does not IPv4 ICMP redirect messages.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check the value of the "all send_redirects" variables with the following command:

$ sudo sysctl net.ipv4.conf.all.send_redirects

net.ipv4.conf.all.send_redirects = 0

If the returned line does not have a value of "0", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to not allow interfaces to perform IPv4 ICMP redirects with the following command:

$ sudo sysctl -w net.ipv4.conf.all.send_redirects=0

If "0" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.all.send_redirects=0

RHEL 8 must not respond to Internet Control Message Protocol (ICMP) echoes sent to a broadcast address.

STIG ID: RHEL-08-040230 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Responding to broadcast ICMP echoes facilitates network mapping and provides a vector for amplification attacks.

There are notable differences between Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6). IPv6 does not implement the same method of broadcast as IPv4. Instead, IPv6 uses multicast addressing to the all-hosts multicast group. Refer to RFC4294 for an explanation of "IPv6 Node Requirements", which resulted in this difference between IPv4 and IPv6.

Check

Verify RHEL 8 does not respond to ICMP echoes sent to a broadcast address.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check the value of the "icmp_echo_ignore_broadcasts" variable with the following command:

$ sudo sysctl net.ipv4.icmp_echo_ignore_broadcasts

net.ipv4.icmp_echo_ignore_broadcasts = 1

If the returned line does not have a value of "1", a line is not returned, or the retuned line is commented out, this is a finding.

Fix

Configure RHEL 8 to not respond to IPv4 ICMP echoes sent to a broadcast address with the following command:

$ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1

If "1" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d":

net.ipv4.icmp_echo_ignore_broadcasts=1

RHEL 8 must not forward source-routed packets.

STIG ID: RHEL-08-040240 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when forwarding is enabled and the system is functioning as a router.

Check

Verify RHEL 8 does not accept source-routed packets.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check the value of the accept source route variable with the following command:

$ sudo sysctl net.ipv4.conf.all.accept_source_route net.ipv6.conf.all.accept_source_route

net.ipv4.conf.all.accept_source_route = 0
net.ipv6.conf.all.accept_source_route = 0

If the returned lines do not have a value of "0", a line is not returned, or either returned line is commented out, this is a finding.

Fix

Configure RHEL 8 to not forward source-routed packets with the following commands:

$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0

$ sudo sysctl -w net.ipv6.conf.all.accept_source_route=0

If "0" is not the system's all value then add or update the following lines in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.all.accept_source_route=0

net.ipv6.conf.all.accept_source_route=0

RHEL 8 must not forward source-routed packets by default.

STIG ID: RHEL-08-040250 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 does not accept source-routed packets by default.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check the value of the accept source route variable with the following command:

$ sudo sysctl net.ipv4.conf.default.accept_source_route net.ipv6.conf.default.accept_source_route

net.ipv4.conf.default.accept_source_route = 0
net.ipv6.conf.default.accept_source_route = 0

If the returned lines do not have a value of "0", a line is not returned, or either returned line is commented out, this is a finding.

Fix

Configure RHEL 8 to not forward source-routed packets by default with the following commands:

$ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0

$ sudo sysctl -w net.ipv6.conf.default.accept_source_route=0

If "0" is not the system's default value then add or update the following lines in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.default.accept_source_route=0

net.ipv6.conf.default.accept_source_route=0

RHEL 8 must not be performing packet forwarding unless the system is a router.

STIG ID: RHEL-08-040260 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network.

Check

Verify RHEL 8 is not performing packet forwarding, unless the system is a router.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check to see if IP forwarding is enabled using the following commands:

$ sudo sysctl net.ipv4.ip_forward

net.ipv4.ip_forward = 0

$ sudo sysctl net.ipv6.conf.all.forwarding

net.ipv6.conf.all.forwarding = 0

If IP forwarding value is not "0" and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure RHEL 8 to not allow packet forwarding, unless the system is a router with the following commands:

$ sudo sysctl -w net.ipv4.ip_forward=0

$ sudo sysctl -w net.ipv6.conf.all.forwarding=0

If "0" is not the system's default value then add or update the following lines in the appropriate file under "/etc/sysctl.d":

net.ipv4.ip_forward=0

net.ipv6.conf.all.forwarding=0

RHEL 8 must not accept router advertisements on all IPv6 interfaces.

STIG ID: RHEL-08-040261 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 does not accept router advertisements on all IPv6 interfaces, unless the system is a router.

Note: If IPv6 is disabled on the system, this requirement is not applicable.

Check to see if router advertisements are not accepted by using the following command:

$ sudo sysctl net.ipv6.conf.all.accept_ra

net.ipv6.conf.all.accept_ra = 0

If the "accept_ra" value is not "0" and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure RHEL 8 to not accept router advertisements on all IPv6 interfaces unless the system is a router with the following commands:

$ sudo sysctl -w net.ipv6.conf.all.accept_ra=0

If "0" is not the system's default value then add or update the following lines in the appropriate file under "/etc/sysctl.d":

net.ipv6.conf.all.accept_ra=0

RHEL 8 must not accept router advertisements on all IPv6 interfaces by default.

STIG ID: RHEL-08-040262 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 does not accept router advertisements on all IPv6 interfaces by default, unless the system is a router.

Note: If IPv6 is disabled on the system, this requirement is not applicable.

Check to see if router advertisements are not accepted by default by using the following command:

$ sudo sysctl net.ipv6.conf.default.accept_ra

net.ipv6.conf.default.accept_ra = 0

If the "accept_ra" value is not "0" and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Configure RHEL 8 to not accept router advertisements on all IPv6 interfaces by default unless the system is a router with the following commands:

$ sudo sysctl -w net.ipv6.conf.default.accept_ra=0

If "0" is not the system's default value then add or update the following lines in the appropriate file under "/etc/sysctl.d":

net.ipv6.conf.default.accept_ra=0

RHEL 8 must not allow interfaces to perform Internet Control Message Protocol (ICMP) redirects by default.

STIG ID: RHEL-08-040270 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 does not allow interfaces to perform Internet Protocol version 4 (IPv4) ICMP redirects by default.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check the value of the "default send_redirects" variables with the following command:

$ sudo sysctl net.ipv4.conf.default.send_redirects

net.ipv4.conf.default.send_redirects=0

If the returned line does not have a value of "0", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to not allow interfaces to perform Internet Protocol version 4 (IPv4) ICMP redirects by default with the following command:

$ sudo sysctl -w net.ipv4.conf.default.send_redirects=0

If "0" is not the system's default value then add or update the following line in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.default.send_redirects=0

RHEL 8 must ignore Internet Control Message Protocol (ICMP) redirect messages.

STIG ID: RHEL-08-040280 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 ignores ICMP redirect messages.

Note: If either IPv4 or IPv6 is disabled on the system, this requirement only applies to the active internet protocol version.

Check the value of the "accept_redirects" variables with the following command:

$ sudo sysctl net.ipv4.conf.all.accept_redirects net.ipv6.conf.all.accept_redirects

net.ipv4.conf.all.accept_redirects = 0
net.ipv6.conf.all.accept_redirects = 0

If both of the returned lines do not have a value of "0", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to ignore ICMP redirect messages with the following commands:

$ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0

$ sudo sysctl -w net.ipv6.conf.all.accept_redirects=0

If "0" is not the system's default value then add or update the following lines in the appropriate file under "/etc/sysctl.d":

net.ipv4.conf.all.accept_redirects = 0

net.ipv6.conf.all.accept_redirects = 0

RHEL 8 must disable access to network bpf syscall from unprivileged processes.

STIG ID: RHEL-08-040281 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 prevents privilege escalation thru the kernel by disabling access to the bpf syscall with the following commands:

$ sudo sysctl kernel.unprivileged_bpf_disabled

kernel.unprivileged_bpf_disabled = 1

If the returned line does not have a value of "1", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to prevent privilege escalation thru the kernel by disabling access to the bpf syscall by adding the following line to a file in the "/etc/sysctl.d" directory:

kernel.unprivileged_bpf_disabled = 1

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

RHEL 8 must restrict usage of ptrace to descendant processes.

STIG ID: RHEL-08-040282 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 restricts usage of ptrace to descendant processes with the following commands:

$ sudo sysctl kernel.yama.ptrace_scope

kernel.yama.ptrace_scope = 1

If the returned line does not have a value of "1", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to restrict usage of ptrace to descendant processes by adding the following line to a file in the "/etc/sysctl.d" directory:

kernel.yama.ptrace_scope = 1

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

RHEL 8 must restrict exposed kernel pointer addresses access.

STIG ID: RHEL-08-040283 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 restricts exposed kernel pointer addresses access with the following commands:

$ sudo sysctl kernel.kptr_restrict

kernel.kptr_restrict = 1

If the returned line does not have a value of "1", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to restrict exposed kernel pointer addresses access by adding the following line to a file in the "/etc/sysctl.d" directory:

kernel.kptr_restrict = 1

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

RHEL 8 must disable the use of user namespaces.

STIG ID: RHEL-08-040284 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 disables the use of user namespaces with the following commands:

Note: User namespaces are used primarily for Linux containers. If containers are in use, this requirement is not applicable.

$ sudo sysctl user.max_user_namespaces

user.max_user_namespaces = 0

If the returned line does not have a value of "0", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to disable the use of user namespaces by adding the following line to a file in the "/etc/sysctl.d" directory:

Note: User namespaces are used primarily for Linux containers. If containers are in use, this requirement is not applicable.

user.max_user_namespaces = 0

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

RHEL 8 must use reverse path filtering on all IPv4 interfaces.

STIG ID: RHEL-08-040285 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify RHEL 8 uses reverse path filtering on all IPv4 interfaces with the following commands:

$ sudo sysctl net.ipv4.conf.all.rp_filter

net.ipv4.conf.all.rp_filter = 1

If the returned line does not have a value of "1", or a line is not returned, this is a finding.

Fix

Configure RHEL 8 to use reverse path filtering on all IPv4 interfaces by adding the following line to a file in the "/etc/sysctl.d" directory:

net.ipv4.conf.all.rp_filter = 1

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system

RHEL 8 must be configured to prevent unrestricted mail relaying.

STIG ID: RHEL-08-040290 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay for the purpose of sending spam or other unauthorized activity.

Check

Verify the system is configured to prevent unrestricted mail relaying.

Determine if "postfix" is installed with the following commands:

$ sudo yum list installed postfix

postfix.x86_64 2:3.3.1-9.el8

If postfix is not installed, this is Not Applicable.

If postfix is installed, determine if it is configured to reject connections from unknown or untrusted networks with the following command:

$ sudo postconf -n smtpd_client_restrictions

smtpd_client_restrictions = permit_mynetworks, reject

If the "smtpd_client_restrictions" parameter contains any entries other than "permit_mynetworks" and "reject", this is a finding.

Fix

If "postfix" is installed, modify the "/etc/postfix/main.cf" file to restrict client connections to the local network with the following command:

$ sudo postconf -e 'smtpd_client_restrictions = permit_mynetworks,reject'

The RHEL 8 file integrity tool must be configured to verify extended attributes.

STIG ID: RHEL-08-040300 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

Extended attributes in file systems are used to contain arbitrary data and file metadata with security implications.

RHEL 8 installation media come with a file integrity tool, Advanced Intrusion Detection Environment (AIDE).

Check

Verify the file integrity tool is configured to verify extended attributes.

If AIDE is not installed, ask the System Administrator how file integrity checks are performed on the system.

Note: AIDE is highly configurable at install time. This requirement assumes the "aide.conf" file is under the "/etc" directory.

Use the following command to determine if the file is in another location:

$ sudo find / -name aide.conf

Check the "aide.conf" file to determine if the "xattrs" rule has been added to the rule list being applied to the files and directories selection lists.

An example rule that includes the "xattrs" rule follows:

All= p+i+n+u+g+s+m+S+sha512+acl+xattrs+selinux
/bin All # apply the custom rule to the files in bin
/sbin All # apply the same custom rule to the files in sbin

If the "xattrs" rule is not being used on all uncommented selection lines in the "/etc/aide.conf" file, or extended attributes are not being checked by another file integrity tool, this is a finding.

Fix

Configure the file integrity tool to check file and directory extended attributes.

If AIDE is installed, ensure the "xattrs" rule is present on all uncommented file and directory selection lists.

The RHEL 8 file integrity tool must be configured to verify Access Control Lists (ACLs).

STIG ID: RHEL-08-040310 | SRG: SRG-OS-000480-GPOS-00227 | Severity: low | CCI: CCI-000366

Vulnerability Discussion

ACLs can provide permissions beyond those permitted through the file mode and must be verified by file integrity tools.

RHEL 8 installation media come with a file integrity tool, Advanced Intrusion Detection Environment (AIDE).

Check

Verify the file integrity tool is configured to verify ACLs.

Note: AIDE is highly configurable at install time. This requirement assumes the "aide.conf" file is under the "/etc" directory.

If AIDE is not installed, ask the System Administrator how file integrity checks are performed on the system.

Use the following command to determine if the file is in a location other than "/etc/aide/aide.conf":

$ sudo find / -name aide.conf

Check the "aide.conf" file to determine if the "acl" rule has been added to the rule list being applied to the files and directories selection lists with the following command:

$ sudo egrep "[+]?acl" /etc/aide.conf

VarFile = OwnerMode+n+l+X+acl

If the "acl" rule is not being used on all selection lines in the "/etc/aide.conf" file, is commented out, or ACLs are not being checked by another file integrity tool, this is a finding.

Fix

Configure the file integrity tool to check file and directory ACLs.

If AIDE is installed, ensure the "acl" rule is present on all file and directory selection lists.

The graphical display manager must not be installed on RHEL 8 unless approved.

STIG ID: RHEL-08-040320 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Internet services that are not required for system or application processes must not be active to decrease the attack surface of the system. Graphical display managers have a long history of security vulnerabilities and must not be used, unless approved and documented.

Check

Verify that the system is configured to boot to the command line:

$ systemctl get-default
multi-user.target

If the system default target is not set to "multi-user.target" and the Information System Security Officer (ISSO) lacks a documented requirement for a graphical user interface, this is a finding.

Verify that a graphical user interface is not installed:

$ rpm -qa | grep xorg | grep server

Ask the System Administrator if use of a graphical user interface is an operational requirement.

If the use of a graphical user interface on the system is not documented with the ISSO, this is a finding.

Fix

Document the requirement for a graphical user interface with the ISSO or reinstall the operating system without the graphical user interface. If reinstallation is not feasible, then continue with the following procedure:

Open an SSH session and enter the following commands:

$ sudo systemctl set-default multi-user.target

$ sudo yum remove xorg-x11-server-Xorg xorg-x11-server-common xorg-x11-server-utils xorg-x11-server-Xwayland

A reboot is required for the changes to take effect.

RHEL 8 network interfaces must not be in promiscuous mode.

STIG ID: RHEL-08-040330 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Network interfaces in promiscuous mode allow for the capture of all network traffic visible to the system. If unauthorized individuals can access these applications, it may allow them to collect information such as logon IDs, passwords, and key exchanges between systems.

If the system is being used to perform a network troubleshooting function, the use of these tools must be documented with the Information System Security Officer (ISSO) and restricted to only authorized personnel.

Check

Verify network interfaces are not in promiscuous mode unless approved by the ISSO and documented.

Check for the status with the following command:

$ sudo ip link | grep -i promisc

If network interfaces are found on the system in promiscuous mode and their use has not been approved by the ISSO and documented, this is a finding.

Fix

Configure network interfaces to turn off promiscuous mode unless approved by the ISSO and documented.

Set the promiscuous mode of an interface to off with the following command:

$ sudo ip link set dev multicast off promisc off

RHEL 8 remote X connections for interactive users must be disabled unless to fulfill documented and validated mission requirements.

STIG ID: RHEL-08-040340 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

The security risk of using X11 forwarding is that the client's X11 display server may be exposed to attack when the SSH client requests forwarding. A system administrator may have a stance in which they want to protect clients that may expose themselves to attack by unwittingly requesting X11 forwarding, which can warrant a "no" setting.

X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the user's X11 authorization database) can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring if the ForwardX11Trusted option is also enabled.

If X11 services are not required for the system's intended function, they should be disabled or restricted as appropriate to the system’s needs.

Check

Verify X11Forwarding is disabled with the following command:

$ sudo grep -i x11forwarding /etc/ssh/sshd_config | grep -v "^#"

X11Forwarding no

If the "X11Forwarding" keyword is set to "yes" and is not documented with the Information System Security Officer (ISSO) as an operational requirement or is missing, this is a finding.

Fix

Edit the "/etc/ssh/sshd_config" file to uncomment or add the line for the "X11Forwarding" keyword and set its value to "no" (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor):

X11Forwarding no

The SSH service must be restarted for changes to take effect:

$ sudo systemctl restart sshd

The RHEL 8 SSH daemon must prevent remote hosts from connecting to the proxy display.

STIG ID: RHEL-08-040341 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

When X11 forwarding is enabled, there may be additional exposure to the server and client displays if the sshd proxy display is configured to listen on the wildcard address. By default, sshd binds the forwarding server to the loopback address and sets the hostname part of the DIPSLAY environment variable to localhost. This prevents remote hosts from connecting to the proxy display.

Check

Verify the SSH daemon prevents remote hosts from connecting to the proxy display.

Check the SSH X11UseLocalhost setting with the following command:

# sudo grep -i x11uselocalhost /etc/ssh/sshd_config
X11UseLocalhost yes

If the "X11UseLocalhost" keyword is set to "no", is missing, or is commented out, this is a finding.

Fix

Configure the SSH daemon to prevent remote hosts from connecting to the proxy display.

Edit the "/etc/ssh/sshd_config" file to uncomment or add the line for the "X11UseLocalhost" keyword and set its value to "yes" (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor):

X11UseLocalhost yes

If the Trivial File Transfer Protocol (TFTP) server is required, the RHEL 8 TFTP daemon must be configured to operate in secure mode.

STIG ID: RHEL-08-040350 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Restricting TFTP to a specific directory prevents remote users from copying, transferring, or overwriting system files.

Check

Verify the TFTP daemon is configured to operate in secure mode with the following commands:

$ sudo yum list installed tftp-server

tftp-server.x86_64 x.x-x.el8

If a TFTP server is not installed, this is Not Applicable.

If a TFTP server is installed, check for the server arguments with the following command:

$ sudo grep server_args /etc/xinetd.d/tftp

server_args = -s /var/lib/tftpboot

If the "server_args" line does not have a "-s" option, and a subdirectory is not assigned, this is a finding.

Fix

Configure the TFTP daemon to operate in secure mode by adding the following line to "/etc/xinetd.d/tftp" (or modify the line to have the required value):

server_args = -s /var/lib/tftpboot

A File Transfer Protocol (FTP) server package must not be installed unless mission essential on RHEL 8.

STIG ID: RHEL-08-040360 | SRG: SRG-OS-000480-GPOS-00227 | Severity: high | CCI: CCI-000366

Vulnerability Discussion

The FTP service provides an unencrypted remote access that does not provide for the confidentiality and integrity of user passwords or the remote session. If a privileged user were to log on using this service, the privileged user password could be compromised. SSH or other encrypted file transfer methods must be used in place of this service.

Check

Verify an FTP server has not been installed on the system with the following commands:

$ sudo yum list installed *ftpd*

vsftpd.x86_64 3.0.3-28.el8 appstream

If an FTP server is installed and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Document the FTP server package with the ISSO as an operational requirement or remove it from the system with the following command:

$ sudo yum remove vsftpd

The gssproxy package must not be installed unless mission essential on RHEL 8.

STIG ID: RHEL-08-040370 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000381

Vulnerability Discussion

Check

Verify the gssproxy package has not been installed on the system with the following commands:

$ sudo yum list installed gssproxy

gssproxy.x86_64 0.8.0-14.el8 @anaconda

If the gssproxy package is installed and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Document the gssproxy package with the ISSO as an operational requirement or remove it from the system with the following command:

$ sudo yum remove gssproxy

The iprutils package must not be installed unless mission essential on RHEL 8.

STIG ID: RHEL-08-040380 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the iprutils package has not been installed on the system with the following commands:

$ sudo yum list installed iprutils

iprutils.x86_64 2.4.18.1-1.el8 @anaconda

If the iprutils package is installed and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Document the iprutils package with the ISSO as an operational requirement or remove it from the system with the following command:

$ sudo yum remove iprutils

The tuned package must not be installed unless mission essential on RHEL 8.

STIG ID: RHEL-08-040390 | SRG: SRG-OS-000480-GPOS-00227 | Severity: medium | CCI: CCI-000366

Vulnerability Discussion

Check

Verify the tuned package has not been installed on the system with the following commands:

$ sudo yum list installed tuned

tuned.noarch 2.12.0-3.el8 @anaconda

If the tuned package is installed and is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix

Document the tuned package with the ISSO as an operational requirement or remove it from the system with the following command:

$ sudo yum remove tuned