The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not allow authentication using known hosts authentication.

STIG ID: RHEL-07-040380 |  SRG: SRG-OS-000480-GPOS-00227 |  Severity: medium |  CCI:  | Vulnerability Id: V-204593

Vulnerability Discussion

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

Check

Configure the SSH daemon to not allow authentication using known hosts authentication.

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

IgnoreUserKnownHosts yes

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

Fix

Verify the SSH daemon does not allow authentication using known hosts authentication.

To determine how the SSH daemon's "IgnoreUserKnownHosts" option is set, run the following command:

# grep -i IgnoreUserKnownHosts /etc/ssh/sshd_config

IgnoreUserKnownHosts yes

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