Title

RHEL 9 SSH daemon must not allow GSSAPI authentication. (Cat II impact)

Discussion

Generic Security Service Application Program Interface (GSSAPI) authentication is used to provide additional authentication mechanisms to applications. Allowing GSSAPI authentication through SSH exposes the system's GSSAPI to remote hosts, increasing the attack surface of the system. Satisfies: SRG-OS-000364-GPOS-00151, SRG-OS-000480-GPOS-00227

Check Content

Verify the SSH daemon does not allow GSSAPI authentication with the following command: $ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*gssapiauthentication' GSSAPIAuthentication no If the value is returned as "yes", the returned line is commented out, no output is returned, and the use of GSSAPI authentication has not been documented with the information system security officer (ISSO), this is a finding. If the required value is not set, this is a finding.

Fix Text

Configure the SSH daemon to not allow GSSAPI authentication. Add the following line in "/etc/ssh/sshd_config", or uncomment the line and set the value to "no": GSSAPIAuthentication no The SSH service must be restarted for changes to take effect: $ sudo systemctl restart sshd.service

Additional Identifiers

Rule ID: SV-258003r952202_rule

Vulnerability ID: V-258003

Group Title: SRG-OS-000364-GPOS-00151

Expert Comments

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