Vulnerability Discussion

A locally logged-in user who presses Ctrl-Alt-Del, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot.

Check

Verify that users cannot enable the Ctrl-Alt-Del sequence in the GNOME desktop with the following command:

Note: This requirement assumes the use of the RHEL 9 default graphical user interface, the GNOME desktop environment. If the system does not have any graphical user interface installed, this requirement is Not Applicable.

$ grep logout /etc/dconf/db/local.d/locks/*

/org/gnome/settings-daemon/plugins/media-keys/logout

If the output is not "/org/gnome/settings-daemon/plugins/media-keys/logout", the line is commented out, or the line is missing, this is a finding.

Fix

Configure RHEL 9 to disallow the user changing the Ctrl-Alt-Del sequence in the GNOME desktop.

Create a database to container system-wide graphical user logon settings (if it does not already exist) with the following command:

$ sudo touch /etc/dconf/db/local.d/locks/session

Add the following line to the session locks file to prevent nonprivileged users from modifying the Ctrl-Alt-Del setting:

/org/gnome/settings-daemon/plugins/media-keys/logout

Run the following command to update the database:

$ sudo dconf update