Vulnerability Discussion

Preventing non-privileged users from executing privileged functions mitigates the risk that unauthorized individuals or processes may gain unnecessary access to information or privileges.

Privileged functions include, for example, establishing accounts, performing system integrity checks, or administering cryptographic key management activities. Non-privileged users are individuals who do not possess appropriate authorizations. Circumventing intrusion detection and prevention mechanisms or malicious code protection mechanisms are examples of privileged functions that require protection from non-privileged users.

Check

Note: Per OPORD 16-0080, the preferred endpoint security tool is Endpoint Security for Linux (ENSL) in conjunction with SELinux.

Verify the operating system prevents non-privileged users from executing privileged functions to include disabling, circumventing, or altering implemented security safeguards/countermeasures.

Obtain a list of authorized users for the system.

Check the list against the system by using the following command:
$ sudo semanage login -l | more
Login Name SELinux User MLS/MCS Range Service
__default__ user_u s0-s0:c0.c1023 *
root unconfined_u s0-s0:c0.c1023 *
system_u system_u s0-s0:c0.c1023 *
joe staff_u s0-s0:c0.c1023 *

All administrators must be mapped to the "staff_u", or an appropriately tailored confined SELinux user as defined by the organization.

All authorized non-administrative users must be mapped to the "user_u" SELinux user.

If they are not mapped in this way, this is a finding.
If administrator accounts are mapped to the "sysadm_u" SELinux user and are not documented as an operational requirement with the ISSO, this is a finding.
If administrator accounts are mapped to the "sysadm_u" SELinux user and are documented as an operational requirement with the ISSO, this can be downgraded to a CAT III.

Fix

Configure the operating system to prevent non-privileged users from executing privileged functions to include disabling, circumventing, or altering implemented security safeguards/countermeasures.

Use the following command to map a new user to the "staff_u" SELinux user:

$ sudo semanage login -a -s staff_u

Use the following command to map an existing user to the "staff_u" SELinux user:

$ sudo semanage login -m -s staff_u

Use the following command to map a new user to the "user_u" SELinux user:

$ sudo semanage login -a -s user_u

Use the following command to map an existing user to the "user_u" SELinux user:

$ sudo semanage login -m -s user_u