RHEL 9 SSH daemon must not allow known hosts authentication.

Documentable No

Rule ID SV-258006r1045071_rule

CCI References

CCI-000366

Discussion

Configuring the IgnoreUserKnownHosts setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere.

Check Procedure

Verify the SSH daemon does not allow known hosts 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*ignoreuserknownhosts'

IgnoreUserKnownHosts yes

If the value is returned as "no", the returned line is commented out, or no output is returned, this is a finding.

Fix Action

Configure the SSH daemon to not allow known hosts authentication.

Add the following line to "/etc/ssh/sshd_config" or to a file in "/etc/ssh/sshd_config.d", or uncomment the line and set the value to "yes":

IgnoreUserKnownHosts yes

The SSH service must be restarted for changes to take effect:

$ sudo systemctl restart sshd.service