AlmaLinux OS 9 SSHD must accept public key authentication.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-269367	SRG-OS-000105-GPOS-00052	ALMA-09-033240	SV-269367r1050250_rule	2025-02-20	1

Description
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.

Description

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.

ℹ️ 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.

ℹ️ 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

✔️ 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