← Back to Tri-Lab Operating System Stack (TOSS) 5 Security Technical Implementation Guide

V-282581

CAT II (Medium)

TOSS 5 SSH daemon must not allow Kerberos authentication.

Rule ID

SV-282581r1200723_rule

STIG

Tri-Lab Operating System Stack (TOSS) 5 Security Technical Implementation Guide

Version

V1R1

CCIs

CCI-001813

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 implementations may be subject to exploitation.

Check Content

Verify the SSH daemon does not allow Kerberos authentication using the following command:

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*kerberosauthentication'

KerberosAuthentication no

If the value is returned as "yes", the returned line is commented out, no output is returned, and the use of Kerberos authentication has not been documented with the information system security officer (ISSO), this is a finding.

Fix Text

Configure the SSH daemon to not allow Kerberos authentication.

Add the following line in "/etc/ssh/sshd_config" or uncomment the line and set the value to "no":

KerberosAuthentication no

Restart the SSH service for changes to take effect:

$ sudo systemctl restart sshd.service