Vulnerability Discussion

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

Check

Verify the Ubuntu operating system generates an audit record upon successful/unsuccessful attempts to use the "ssh-keysign" command.

Check the configured audit rules with the following commands:

$ sudo auditctl -l | grep ssh-keysign

-a always,exit -S all -F path=/usr/lib/openssh/ssh-keysign -F perm=x -F auid>=1000 -F auid!=-1 -F key=privileged-ssh

If the command does not return lines that match the example or the lines are commented out, this is a finding.

Note: The "key=" value is arbitrary and can be different from the example output above.

Fix

Configure the audit system to generate an audit event for any successful/unsuccessful use of the "ssh-keysign" command.

Add or update the following rules in the "/etc/audit/rules.d/stig.rules" file:

-a always,exit -F path=/usr/lib/openssh/ssh-keysign -F perm=x -F auid>=1000 -F auid!=unset -k privileged-ssh

To reload the rules file, issue the following command:

$ sudo augenrules --load

Note: The "-k " at the end of the line gives the rule a unique meaning to help during an audit investigation. The does not need to match the example above.