1.8.5 Ensure GDM screen locks cannot be overridden

Audit

Run the following script to verify that the screen lock can not be overridden:

#!/usr/bin/env bash
{
 # Check if GNOME Desktop Manager is installed. If package isn't installed, recommendation is Not Applicable\n
 # determine system's package manager
 l_pkgoutput=""
 if command -v dpkg-query > /dev/null 2>&1; then
 l_pq="dpkg-query -W"
 elif command -v rpm > /dev/null 2>&1; then
 l_pq="rpm -q"
 fi
 # Check if GDM is installed
 l_pcl="gdm gdm3" # Space seporated list of packages to check
 for l_pn in $l_pcl; do
 $l_pq "$l_pn" > /dev/null 2>&1 && l_pkgoutput="$l_pkgoutput\n - Package: \"$l_pn\" exists on the system\n - checking configuration"
 done
 # Check configuration (If applicable)
 if [ -n "$l_pkgoutput" ]; then
 l_output="" l_output2=""
 # Look for idle-delay to determine profile in use, needed for remaining tests
 l_kfd="/etc/dconf/db/$(grep -Psril '^\h*idledelay\h*=\h*uint32\h+\d+\b' /etc/dconf/db/*/ | awk -F'/' '{split($(NF1),a,".");print a[1]}').d" #set directory of key file to be locked
 l_kfd2="/etc/dconf/db/$(grep -Psril '^\h*lockdelay\h*=\h*uint32\h+\d+\b' /etc/dconf/db/*/ | awk -F'/' '{split($(NF1),a,".");print a[1]}').d" #set directory of key file to be locked
 if [ -d "$l_kfd" ]; then # If key file directory doesn't exist, options can't be locked
 if grep -Prilq '\/org\/gnome\/desktop\/session\/idle-delay\b' "$l_kfd"; then
 l_output="$l_output\n - \"idle-delay\" is locked in \"$(grep - Pril '\/org\/gnome\/desktop\/session\/idle-delay\b' "$l_kfd")\""
 else
 l_output2="$l_output2\n - \"idle-delay\" is not locked"
 fi
 else
 l_output2="$l_output2\n - \"idle-delay\" is not set so it can not be locked"
 fi
 if [ -d "$l_kfd2" ]; then # If key file directory doesn't exist, options can't be locked
 if grep -Prilq '\/org\/gnome\/desktop\/screensaver\/lock-delay\b' "$l_kfd2"; then
 l_output="$l_output\n - \"lock-delay\" is locked in \"$(grep - Pril '\/org\/gnome\/desktop\/screensaver\/lock-delay\b' "$l_kfd2")\""
 else
 l_output2="$l_output2\n - \"lock-delay\" is not locked"
 fi
 else
 l_output2="$l_output2\n - \"lock-delay\" is not set so it can not be locked"
 fi
 else
 l_output="$l_output\n - GNOME Desktop Manager package is not installed on the system\n - Recommendation is not applicable"
 fi
 # Report results. If no failures output in l_output2, we pass
[ -n "$l_pkgoutput" ] && echo -e "\n$l_pkgoutput"
 if [ -z "$l_output2" ]; then
 echo -e "\n- Audit Result:\n ** PASS **\n$l_output\n"
 else
 echo -e "\n- Audit Result:\n ** FAIL **\n - Reason(s) for audit
failure:\n$l_output2\n"
 [ -n "$l_output" ] && echo -e "\n- Correctly set:\n$l_output\n"
 fi
}

Remediation

Run the following script to ensure screen locks can not be overridden:

#!/usr/bin/env bash
{
 # Check if GNMOE Desktop Manager is installed. If package isn't installed, recommendation is Not Applicable\n
 # determine system's package manager
 l_pkgoutput=""
 if command -v dpkg-query > /dev/null 2>&1; then
 l_pq="dpkg-query -W"
 elif command -v rpm > /dev/null 2>&1; then
 l_pq="rpm -q"
 fi
 # Check if GDM is installed
 l_pcl="gdm gdm3" # Space seporated list of packages to check
 for l_pn in $l_pcl; do
 $l_pq "$l_pn" > /dev/null 2>&1 && l_pkgoutput="y" && echo -e "\n - Package: \"$l_pn\" exists on the system\n - remediating configuration if needed"
 done
 # Check configuration (If applicable)
 if [ -n "$l_pkgoutput" ]; then
 # Look for idle-delay to determine profile in use, needed for remaining tests
 l_kfd="/etc/dconf/db/$(grep -Psril '^\h*idledelay\h*=\h*uint32\h+\d+\b' /etc/dconf/db/*/ | awk -F'/' '{split($(NF1),a,".");print a[1]}').d" #set directory of key file to be locked
 # Look for lock-delay to determine profile in use, needed for remaining tests
 l_kfd2="/etc/dconf/db/$(grep -Psril '^\h*lockdelay\h*=\h*uint32\h+\d+\b' /etc/dconf/db/*/ | awk -F'/' '{split($(NF1),a,".");print a[1]}').d" #set directory of key file to be locked
 if [ -d "$l_kfd" ]; then # If key file directory doesn't exist, options can't be locked
 if grep -Prilq '^\h*\/org\/gnome\/desktop\/session\/idle-delay\b' "$l_kfd"; then
 echo " - \"idle-delay\" is locked in \"$(grep -Pril '^\h*\/org\/gnome\/desktop\/session\/idle-delay\b' "$l_kfd")\""
 else
 echo "creating entry to lock \"idle-delay\""
 [ ! -d "$l_kfd"/locks ] && echo "creating directory $l_kfd/locks" && mkdir "$l_kfd"/locks
 {
 echo -e '\n# Lock desktop screensaver idle-delay setting'
 echo '/org/gnome/desktop/session/idle-delay'
 } >> "$l_kfd"/locks/00-screensaver
 fi
 else
 echo -e " - \"idle-delay\" is not set so it can not be locked\n - Please follow Recommendation \"Ensure GDM screen locks when the user is idle\" and follow this Recommendation again"
 fi
 if [ -d "$l_kfd2" ]; then # If key file directory doesn't exist, options can't be locked
 if grep -Prilq '^\h*\/org\/gnome\/desktop\/screensaver\/lockdelay\b' "$l_kfd2"; then
 echo " - \"lock-delay\" is locked in \"$(grep -Pril '^\h*\/org\/gnome\/desktop\/screensaver\/lock-delay\b' "$l_kfd2")\""
 else
 echo "creating entry to lock \"lock-delay\""
 [ ! -d "$l_kfd2"/locks ] && echo "creating directory $l_kfd2/locks" && mkdir "$l_kfd2"/locks
 {
 echo -e '\n# Lock desktop screensaver lock-delay setting'
 echo '/org/gnome/desktop/screensaver/lock-delay'
 } >> "$l_kfd2"/locks/00-screensaver
 fi
 else
 echo -e " - \"lock-delay\" is not set so it can not be locked\n - Please follow Recommendation \"Ensure GDM screen locks when the user is idle\" and follow this Recommendation again"
 fi
 else
 echo -e " - GNOME Desktop Manager package is not installed on the system\n - Recommendation is not applicable"
 fi
}

Run the following command to update the system databases:

# dconf update

Note: Users must log out and back in again before the system-wide settings take effect.