STIG ID: UBTU-20-010033 | SRG: SRG-OS-000105-GPOS-00052 | Severity: medium | CCI: | Vulnerability Id: V-238210
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.
Satisfies: SRG-OS-000105-GPOS-00052, SRG-OS-000106-GPOS-00053, SRG-OS-000107-GPOS-00054, SRG-OS-000108-GPOS-00055
Configure the Ubuntu operating system to use multifactor authentication for network access to accounts.
Add or update the following line in "/etc/pam.d/common-auth", placing it above any lines containing "pam_unix.so":
auth [success=2 default=ignore] pam_pkcs11.so
Set the sshd option "PubkeyAuthentication yes" in the "/etc/ssh/sshd_config" file.
Verify the Ubuntu operating system has the packages required for multifactor authentication installed with the following commands:
$ dpkg -l | grep libpam-pkcs11
ii libpam-pkcs11 0.6.8-4 amd64 Fully featured PAM module for using PKCS#11 smart cards
If the "libpam-pkcs11" package is not installed, this is a finding.
Verify the sshd daemon allows public key 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*pubkeyauthentication'
PubkeyAuthentication yes
If this option is set to "no" or is missing, this is a finding.
If conflicting results are returned, this is a finding.