RHEL 9 pam_unix.so module must be configured in the password-auth file to use a FIPS 140-3 approved cryptographic hashing algorithm for system authentication.

STIG ID: RHEL-09-671025  |  SRG: SRG-OS-000073-GPOS-00041 | Severity: medium |  CCI: CCI-004062

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

FIPS 140-3 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 the pam_unix.so module is configured to use sha512 in /etc/pam.d/password-auth with the following command:

$ grep "^password.*pam_unix.so.*sha512" /etc/pam.d/password-auth

password sufficient pam_unix.so sha512

If "sha512" is missing, or the line is commented out, this is a finding.

Fix

Configure RHEL 9 to use a FIPS 140-3 approved cryptographic hashing algorithm for system authentication.

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

password sufficient pam_unix.so sha512
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