Vulnerability Discussion

A session lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not want to log out because of the temporary nature of the absence.

The session lock is implemented at the point where session activity can be determined. Rather than be forced to wait for a period of time to expire before the user session can be locked, RHEL 8 needs to provide users with the ability to manually invoke a session lock so users can secure their session if it is necessary to temporarily vacate the immediate physical vicinity.

Tmux is a terminal multiplexer that enables a number of terminals to be created, accessed, and controlled from a single screen. Red Hat endorses tmux as the recommended session controlling package.

Satisfies: SRG-OS-000028-GPOS-00009, SRG-OS-000030-GPOS-00011

Check

Verify the operating system enables the user to initiate a session lock on command.

Verify RHEL 8 has the "tmux" package installed, by running the following command:

$ sudo yum list installed tmux

tmux.x86.64 2.7-1.el8 @repository

If "tmux" is not installed, this is a finding.

Next verify that the lock-command is set in the global settings of tmux with the following command:

$ sudo grep -i lock-command /etc/tmux.conf

set -g lock-command vlock

If the "lock-command" is not set in the global settings to call "vlock", this is a finding.

Fix

Configure the operating system to enable a user to initiate a session lock via tmux.

Install the "tmux" package, if it is not already installed, by running the following command:

$ sudo yum install tmux

Once installed, create a global configuration file "/etc/tmux.conf" and add the following line:

set -g lock-command vlock