Vulnerability Discussion

Without the use of multifactor authentication, the ease of access to privileged functions is greatly increased. Multifactor authentication requires using two or more factors to achieve authentication. A privileged account is defined as an information system account with authorizations of a privileged user. A DOD common access card (CAC) with DOD-approved PKI is an example of multifactor authentication.

Satisfies: SRG-OS-000105-GPOS-00052, SRG-OS-000106-GPOS-00053, SRG-OS-000107-GPOS-00054, SRG-OS-000108-GPOS-00055

Check

Verify that RHEL 9 SSH daemon accepts public key encryption 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*pubkeyauthentication'

PubkeyAuthentication yes

If "PubkeyAuthentication" is set to no, the line is commented out, or the line is missing, this is a finding.

Note: If the system administrator demonstrates the use of an approved alternate multifactor authentication method, this requirement is not applicable.

Fix

To configure the system add or modify the following line in "/etc/ssh/sshd_config".

PubkeyAuthentication yes

Restart the SSH daemon for the settings to take effect:

$ sudo systemctl restart sshd.service