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RHEL 9 SSH daemon must not allow known hosts authentication.


Overview

Finding ID Version Rule ID IA Controls Severity
V-258006 RHEL-09-255150 SV-258006r991589_rule Medium
Description
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.
STIG Date
Red Hat Enterprise Linux 9 Security Technical Implementation Guide 2024-06-04

Details

Check Text ( C-61747r952207_chk )
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 Text (F-61671r926004_fix)
Configure the SSH daemon to not allow 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:

$ sudo systemctl restart sshd.service