Disable the GNOME3 Login Restart and Shutdown Buttons

An XCCDF Rule

Description

In the default graphical environment, users logging directly into the system are greeted with a login screen that allows any user, known or unknown, the ability the ability to shutdown or restart the system. This functionality should be disabled by setting disable-restart-buttons to true.

To disable, add or edit disable-restart-buttons to /etc/dconf/db/gdm.d/00-security-settings. For example:

[org/gnome/login-screen]
disable-restart-buttons=true

Once the setting has been added, add a lock to /etc/dconf/db/gdm.d/locks/00-security-settings-lock to prevent user modification. For example:

/org/gnome/login-screen/disable-restart-buttons

After the settings have been set, run dconf update.

Rationale

A user who is at the console can reboot the system at the login screen. If restart or shutdown buttons are pressed at the login screen, this can create the risk of short-term loss of availability of systems due to reboot.

ID: xccdf_org.ssgproject.content_rule_dconf_gnome_disable_restart_shutdown
Severity: High
References: 12 13 14 15 16 18 3 5

APO01.06 DSS05.04 DSS05.07 DSS06.02

3.1.2

CCI-000366

4.3.3.7.3

SR 2.1 SR 5.2

A.10.1.1 A.11.1.4 A.11.1.5 A.11.2.1 A.13.1.1 A.13.1.3 A.13.2.1 A.13.2.3 A.13.2.4 A.14.1.2 A.14.1.3 A.6.1.2 A.7.1.1 A.7.1.2 A.7.3.1 A.8.2.2 A.8.2.3 A.9.1.1 A.9.1.2 A.9.2.3 A.9.4.1 A.9.4.4 A.9.4.5

AC-6(1) CM-6(a) CM-7(b)

PR.AC-4 PR.DS-5

SRG-OS-000480-GPOS-00227
Updated: over 1 year ago

# 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
# If files contain ibus or distro, ignore them.
# The assignment assumes that individual filenames don't contain :readarray -t SETTINGSFILES < <(grep -r "\\[org/gnome/login-screen\\]" "/etc/dconf/db/" \
                                | grep -v 'distro\|ibus\|gdm.d' | cut -d":" -f1)
DCONFFILE="/etc/dconf/db/gdm.d/00-security-settings"
DBDIR="/etc/dconf/db/gdm.d"

mkdir -p "${DBDIR}"

# Comment out the configurations in databases different from the target one
if [ "${#SETTINGSFILES[@]}" -ne 0 ]
then
    if grep -q "^\\s*disable-restart-buttons\\s*=" "${SETTINGSFILES[@]}"
    then
        
        sed -Ei "s/(^\s*)disable-restart-buttons(\s*=)/#\1disable-restart-buttons\2/g" "${SETTINGSFILES[@]}"
    fi
fi

[ ! -z "${DCONFFILE}" ] && echo "" >> "${DCONFFILE}"
if ! grep -q "\\[org/gnome/login-screen\\]" "${DCONFFILE}"
then
    printf '%s\n' "[org/gnome/login-screen]" >> ${DCONFFILE}
fi

escaped_value="$(sed -e 's/\\/\\\\/g' <<< "true")"
if grep -q "^\\s*disable-restart-buttons\\s*=" "${DCONFFILE}"
then
        sed -i "s/\\s*disable-restart-buttons\\s*=\\s*.*/disable-restart-buttons=${escaped_value}/g" "${DCONFFILE}"
    else
        sed -i "\\|\\[org/gnome/login-screen\\]|a\\disable-restart-buttons=${escaped_value}" "${DCONFFILE}"
fi

dconf update
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/login-screen/disable-restart-buttons$" "/etc/dconf/db/" \
            | grep -v 'distro\|ibus\|gdm.d' | grep ":" | cut -d":" -f1)
LOCKSFOLDER="/etc/dconf/db/gdm.d/locks"

mkdir -p "${LOCKSFOLDER}"

# Comment out the configurations in databases different from the target one
if [[ ! -z "${LOCKFILES}" ]]
then
    sed -i -E "s|^/org/gnome/login-screen/disable-restart-buttons$|#&|" "${LOCKFILES[@]}"
fi

if ! grep -qr "^/org/gnome/login-screen/disable-restart-buttons$" /etc/dconf/db/gdm.d/
then
    echo "/org/gnome/login-screen/disable-restart-buttons" >> "/etc/dconf/db/gdm.d/locks/00-security-settings-lock"
fi

dconf update

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - NIST-800-171-3.1.2
  - NIST-800-53-AC-6(1)  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_restart_shutdown
  - high_severity
  - low_complexity
  - medium_disruption
  - no_reboot_needed
  - unknown_strategy

- name: Disable the GNOME3 Login Restart and Shutdown Buttons
  ini_file:
    dest: /etc/dconf/db/gdm.d/00-security-settings
    section: org/gnome/login-screen
    option: disable-restart-buttons
    value: 'true'
    create: true
    no_extra_spaces: true
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_restart_shutdown
  - high_severity
  - low_complexity
  - medium_disruption
  - no_reboot_needed
  - unknown_strategy

- name: Prevent user modification of GNOME disablement of Login Restart and Shutdown
    Buttons
  lineinfile:
    path: /etc/dconf/db/gdm.d/locks/00-security-settings-lock
    regexp: ^/org/gnome/login-screen/disable-restart-buttons
    line: /org/gnome/login-screen/disable-restart-buttons
    create: true
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-171-3.1.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_restart_shutdown
  - high_severity
  - low_complexity
  - medium_disruption
  - 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:
  - NIST-800-171-3.1.2
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_restart_shutdown
  - high_severity
  - low_complexity
  - medium_disruption
  - no_reboot_needed
  - unknown_strategy

Disable the GNOME3 Login Restart and Shutdown Buttons

Description

Rationale

Remediation - Shell Script

Remediation - Ansible