Ensure Users Cannot Change GNOME3 Screensaver Settings
Description
If not already configured, ensure that users cannot change GNOME3 screensaver lock settings
by adding /org/gnome/desktop/screensaver/lock-delay
to /etc/dconf/db/local.d/locks/00-security-settings-lock to prevent user modification.
For example:
/org/gnome/desktop/screensaver/lock-delay
After the settings have been set, run dconf update.
Rationale
A session time-out 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 logout because of the temporary nature of the absence.
Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity,
GNOME desktops can be configured to identify when a user’s session has idled and take action to initiate the
session lock. As such, users should not be allowed to change session settings.
Shell script
The following script can be run on the host to remediate the issue.
# Remediation is applicable only in certain platforms
if rpm --quiet -q gdm && { [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; }; then
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/desktop/screensaver/lock-delay$" "/etc/dconf/db/" \
| grep -v 'distro\|ibus\|local.d' | grep ":" | cut -d":" -f1)
LOCKSFOLDER="/etc/dconf/db/local.d/locks"
mkdir -p "${LOCKSFOLDER}"
# Comment out the configurations in databases different from the target one
if [[ ! -z "${LOCKFILES}" ]]
then
sed -i -E "s|^/org/gnome/desktop/screensaver/lock-delay$|#&|" "${LOCKFILES[@]}"
fi
if ! grep -qr "^/org/gnome/desktop/screensaver/lock-delay$" /etc/dconf/db/local.d/
then
echo "/org/gnome/desktop/screensaver/lock-delay" >> "/etc/dconf/db/local.d/locks/00-security-settings-lock"
fi
dconf update
else
>&2 echo 'Remediation is not applicable, nothing was done'
fi
Ansible playbook
The following playbook can be run with Ansible to remediate the issue.
- name: Gather the package facts
package\_facts:
manager: auto
tags:
- CCE-87491-7
- NIST-800-171-3.1.10
- NIST-800-53-CM-6(a)
- dconf\_gnome\_screensaver\_user\_locks
- low\_complexity
- medium\_disruption
- medium\_severity
- no\_reboot\_needed
- unknown\_strategy
- name: Prevent user modification of GNOME lock-delay
lineinfile:
path: /etc/dconf/db/local.d/locks/00-security-settings-lock
regexp: ^/org/gnome/desktop/screensaver/lock-delay$
line: /org/gnome/desktop/screensaver/lock-delay
create: true
when:
- '"gdm" in ansible\_facts.packages'
- ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
tags:
- CCE-87491-7
- NIST-800-171-3.1.10
- NIST-800-53-CM-6(a)
- dconf\_gnome\_screensaver\_user\_locks
- low\_complexity
- medium\_disruption
- medium\_severity
- no\_reboot\_needed
- unknown\_strategy
- name: Dconf Update
command: dconf update
when:
- '"gdm" in ansible\_facts.packages'
- ansible\_virtualization\_type not in ["docker", "lxc", "openvz", "podman", "container"]
tags:
- CCE-87491-7
- NIST-800-171-3.1.10
- NIST-800-53-CM-6(a)
- dconf\_gnome\_screensaver\_user\_locks
- low\_complexity
- medium\_disruption
- medium\_severity
- no\_reboot\_needed
- unknown\_strategy
