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 confines SELinux users to roles that conform to least privilege.

Check the SELinux User list to SELinux Roles mapping by using the following command:

$ sudo semanage user -l
SELinuxUser LabelingPrefix MLS/MCSLevel MLS/MCSRange SELinuxRoles
guest_u user s0 s0 guest_r
root user s0 s0-s0:c0.c1023 staff_r sysadm_r system_r unconfined_r
staff_u user s0 s0-s0:c0.c1023 staff_r sysadm_r
sysadm_u user s0 s0-s0:c0.c1023 sysadm_r
system_u user s0 s0-s0:c0.c1023 system_r unconfined_r
unconfined_u user s0 s0-s0:c0.c1023 system_r unconfined_r
user_u user s0 s0 user_r
xguest_u user s0 s0 xguest_r

If the output differs from the above example, ask the SA to demonstrate how the SELinux User mappings are exercising least privilege. If deviations from the example are not documented with the ISSO and do not demonstrate least privilege, this is a finding.

Fix

Configure the operating system to confine SELinux users to roles that conform to least privilege.

Use the following command to map the "staff_u" SELinux user to the "staff_r" and "sysadm_r" roles:

$ sudo semanage user -m staff_u -R staff_r -R sysadm_r

Use the following command to map the "user_u" SELinux user to the "user_r" role:

$ sudo semanage -m user_u -R user_r