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RHEL-09-255150 RHEL 9 SSH daemon must not allow known hosts authentication.

DISA STIG library V2R10
All changes in this version
first version loaded CAT II

Maps to CM-6 via CCI-000366

Title

RHEL 9 SSH daemon must not allow known hosts authentication.

Control

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.

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.

Related controls

CCI-000366

Fix

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