Ubuntu OS must be configured such that Pluggable Authentication Module (PAM) prohibits the use of cached authentications after one day.

If cached authentication information is out-of-date, the validity of the authentication information may be questionable.

Verify PAM prohibits the use of cached authentications after one day by using the following command:

Note: If smart card authentication is not being used on the system, this requirement is not applicable.

     $ sudo grep -i '^\s*offline_credentials_expiration' /etc/sssd/sssd.conf /etc/sssd/conf.d/*.conf 
     /etc/sssd/sssd.conf:offline_credentials_expiration = 1 

If "offline_credentials_expiration" is not set to "1", is commented out, is missing, or conflicting results are returned, this is a finding.

Configure PAM to prohibit the use of cached authentications after one day.

Add or modify the following line in the "/etc/sssd/sssd.conf" file, just below the line "[pam]":

offline_credentials_expiration = 1

Note: It is valid for this configuration to be in a file with a name that ends with ".conf" and does not begin with a "." in the "/etc/sssd/conf.d/" directory instead of the "/etc/sssd/sssd.conf" file.