Check: RHEL-07-040440
RHEL 7 STIG:
RHEL-07-040440
(in versions v3 r15 through v1 r1)
Title
The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not permit Kerberos authentication unless needed. (Cat II impact)
Discussion
Kerberos authentication for SSH is often implemented using Generic Security Service Application Program Interface (GSSAPI). If Kerberos is enabled through SSH, the SSH daemon provides a means of access to the system's Kerberos implementation. Vulnerabilities in the system's Kerberos implementation may then be subject to exploitation. To reduce the attack surface of the system, the Kerberos authentication mechanism within SSH must be disabled for systems not using this capability.
Check Content
Verify the SSH daemon does not permit Kerberos to authenticate passwords unless approved. Check that the SSH daemon does not permit Kerberos to authenticate passwords with the following command: # grep -i kerberosauth /etc/ssh/sshd_config KerberosAuthentication no If the "KerberosAuthentication" keyword is missing, or is set to "yes" and is not documented with the Information System Security Officer (ISSO), or the returned line is commented out, this is a finding.
Fix Text
Uncomment the "KerberosAuthentication" 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) and set the value to "no": KerberosAuthentication no The SSH service must be restarted for changes to take effect. If Kerberos authentication is required, it must be documented, to include the location of the configuration file, with the ISSO.
Additional Identifiers
Rule ID: SV-204599r958796_rule
Vulnerability ID: V-204599
Group Title: SRG-OS-000364-GPOS-00151
Expert Comments
CCIs
| Number | Definition |
|---|---|
| CCI-000318 |
Monitor and review activities associated with configuration-controlled changes to the system. |
| CCI-000368 |
Document any deviations from the established configuration settings for organization-defined system components based on organization-defined operational requirements. |
| CCI-001812 |
The information system prohibits user installation of software without explicit privileged status. |
| CCI-001813 |
Enforce access restrictions using organization-defined mechanisms. |
| CCI-001814 |
The Information system supports auditing of the enforcement actions. |