The SSH daemon must not allow authentication using known hosts authentication.

From Canonical Ubuntu 16.04 Security Technical Implementation Guide

Associated with: CCI-000366

SV-90521r2_rule The SSH daemon must not allow authentication using known hosts authentication.

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 content

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 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.

Fix text

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 daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command: # sudo systemctl restart sshd.service

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