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.

Factors include:
1) something a user knows (e.g., password/PIN);
2) something a user has (e.g., cryptographic identification device, token); and
3) something a user is (e.g., biometric).

A privileged account is defined as an information system account with authorizations of a privileged user.

Network access is defined as access to an information system by a user (or a process acting on behalf of a user) communicating through a network (e.g., local area network, wide area network, or the internet).

The DOD CAC with DOD-approved PKI is an example of multifactor authentication.

Check

Note: If the system administrator (SA) demonstrates the use of an approved alternate multifactor authentication method, this requirement is Not Applicable.

Verify that AlmaLinux OS 9 SSH daemon accepts public key encryption with the following command:

$ sshd -T | grep -i pubkeyauthentication

pubkeyauthentication yes

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

Fix

Configure the SSH daemon to accept public key encryption.

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

PubkeyAuthentication yes

Alternatively, add the setting to an include file if the line "Include /etc/ssh/sshd_config.d/*.conf" is found at the top of the "/etc/ssh/sshd_config" file:

$ cat << EOF | tee /etc/ssh/sshd_config.d/pubkey.conf
PubkeyAuthentication yes
EOF

Restart the SSH daemon for the settings to take effect:

$ systemctl restart sshd.service