Disable Ctrl-Alt-Del Reboot Key Sequence in GNOME3

An XCCDF Rule

Description

By default, GNOME will reboot the system if the Ctrl-Alt-Del key sequence is pressed.

To configure the system to ignore the Ctrl-Alt-Del key sequence from the Graphical User Interface (GUI) instead of rebooting the system, add or set logout to '' in /etc/dconf/db/local.d/00-security-settings. For example:

[org/gnome/settings-daemon/plugins/media-keys]
logout=''

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

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

After the settings have been set, run dconf update.

Rationale

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.

ID: xccdf_org.ssgproject.content_rule_dconf_gnome_disable_ctrlaltdel_reboot
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: about 1 year ago

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'gdm3' 2>/dev/null | grep -q installed && { [ ! -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/settings-daemon/plugins/media-keys\\]" "/etc/dconf/db/" \
                                | grep -v 'distro\|ibus\|local.d' | cut -d":" -f1)
DCONFFILE="/etc/dconf/db/local.d/00-security-settings"
DBDIR="/etc/dconf/db/local.d"

mkdir -p "${DBDIR}"

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

[ ! -z "${DCONFFILE}" ] && echo "" >> "${DCONFFILE}"
if ! grep -q "\\[org/gnome/settings-daemon/plugins/media-keys\\]" "${DCONFFILE}"
then
    printf '%s\n' "[org/gnome/settings-daemon/plugins/media-keys]" >> ${DCONFFILE}
fi

escaped_value="$(sed -e 's/\\/\\\\/g' <<< "''")"
if grep -q "^\\s*logout\\s*=" "${DCONFFILE}"
then
        sed -i "s/\\s*logout\\s*=\\s*.*/logout=${escaped_value}/g" "${DCONFFILE}"
    else
        sed -i "\\|\\[org/gnome/settings-daemon/plugins/media-keys\\]|a\\logout=${escaped_value}" "${DCONFFILE}"
fi

dconf update
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/settings-daemon/plugins/media-keys/logout$" "/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 "${LOCKFILES}" ]]
then
    sed -i -E "s|^/org/gnome/settings-daemon/plugins/media-keys/logout$|#&|" "${LOCKFILES[@]}"
fi

if ! grep -qr "^/org/gnome/settings-daemon/plugins/media-keys/logout$" /etc/dconf/db/local.d/
then
    echo "/org/gnome/settings-daemon/plugins/media-keys/logout" >> "/etc/dconf/db/local.d/locks/00-security-settings-lock"
fi

dconf update

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

Disable Ctrl-Alt-Del Reboot Key Sequence in GNOME3

Description

Rationale

Remediation - Shell Script