Enable the GNOME3 Screen Locking On Smartcard Removal

An XCCDF Rule

Description

In the default graphical environment, screen locking on smartcard removal can be enabled by setting removal-action to 'lock-screen'.

To enable, add or edit removal-action to /etc/dconf/db/local.d/00-security-settings. For example:

[org/gnome/settings-daemon/peripherals/smartcard]
removal-action='lock-screen'

Once the setting has 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/peripherals/smartcard/removal-action

After the settings have been set, run dconf update.

Rationale

Locking the screen automatically when removing the smartcard can prevent undesired access to system.

ID: xccdf_org.ssgproject.content_rule_dconf_gnome_lock_screen_on_smartcard_removal
Severity: Medium
References: CCI-000056 CCI-000058

SRG-OS-000028-GPOS-00009 SRG-OS-000030-GPOS-00011

OL08-00-020050

SV-248679r818655_rule
Updated: about 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/settings-daemon/peripherals/smartcard\\]" "/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 [ "${#SETTINGSFILES[@]}" -ne 0 ]
then
    if grep -q "^\\s*removal-action\\s*=" "${SETTINGSFILES[@]}"
    then
        
        sed -Ei "s/(^\s*)removal-action(\s*=)/#\1removal-action\2/g" "${SETTINGSFILES[@]}"
    fi
fi

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

escaped_value="$(sed -e 's/\\/\\\\/g' <<< "'lock-screen'")"
if grep -q "^\\s*removal-action\\s*=" "${DCONFFILE}"
then
        sed -i "s/\\s*removal-action\\s*=\\s*.*/removal-action=${escaped_value}/g" "${DCONFFILE}"
    else
        sed -i "\\|\\[org/gnome/settings-daemon/peripherals/smartcard\\]|a\\removal-action=${escaped_value}" "${DCONFFILE}"
fi

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

if ! grep -qr "^/org/gnome/settings-daemon/peripherals/smartcard/removal-action$" /etc/dconf/db/local.d/
then
    echo "/org/gnome/settings-daemon/peripherals/smartcard/removal-action" >> "/etc/dconf/db/local.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:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

- name: Detect if removal-action can be found on /etc/dconf/db/local.d/
  find:
    path: /etc/dconf/db/local.d/
    contains: ^\s*removal-action
  register: dconf_gnome_lock_screen_on_smartcard_removal_config_files
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

- name: Configure removal-action - default file
  ini_file:
    dest: /etc/dconf/db/local.d//00-security-settings
    section: org/gnome/settings-daemon/peripherals/smartcard
    option: removal-action
    value: '''lock-screen'''
    create: true
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - dconf_gnome_lock_screen_on_smartcard_removal_config_files is defined and dconf_gnome_lock_screen_on_smartcard_removal_config_files.matched
    == 0
  tags:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

- name: Configure removal-action - existing files
  ini_file:
    dest: '{{ item.path }}'
    section: org/gnome/settings-daemon/peripherals/smartcard
    option: removal-action
    value: '''lock-screen'''
    create: true
  with_items: '{{ dconf_gnome_lock_screen_on_smartcard_removal_config_files.files
    }}'
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - dconf_gnome_lock_screen_on_smartcard_removal_config_files is defined and dconf_gnome_lock_screen_on_smartcard_removal_config_files.matched
    > 0
  tags:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

- name: Detect if lock for removal-action can be found on /etc/dconf/db/local.d/
  find:
    path: /etc/dconf/db/local.d/locks
    contains: ^\s*removal-action
  register: dconf_gnome_lock_screen_on_smartcard_removal_lock_files
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

- name: Prevent user modification removal-action - default file
  lineinfile:
    path: /etc/dconf/db/local.d/locks/00-security-settings-lock
    regexp: ^/org/gnome/settings-daemon/peripherals/smartcard/removal-action$
    line: /org/gnome/settings-daemon/peripherals/smartcard/removal-action
    create: true
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - dconf_gnome_lock_screen_on_smartcard_removal_lock_files is defined and dconf_gnome_lock_screen_on_smartcard_removal_lock_files.matched
    == 0
  tags:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

- name: Prevent user modification removal-action - existing files
  lineinfile:
    path: '{{ item.path }}'
    regexp: ^/org/gnome/settings-daemon/peripherals/smartcard/removal-action$
    line: /org/gnome/settings-daemon/peripherals/smartcard/removal-action
    create: true
  with_items: '{{ dconf_gnome_lock_screen_on_smartcard_removal_lock_files.files }}'
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  - dconf_gnome_lock_screen_on_smartcard_removal_lock_files is defined and dconf_gnome_lock_screen_on_smartcard_removal_lock_files.matched
    > 0
  tags:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

- name: Dconf Update - removal-action
  command: dconf update
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - DISA-STIG-OL08-00-020050
  - dconf_gnome_lock_screen_on_smartcard_removal
  - low_complexity
  - medium_disruption
  - medium_severity
  - no_reboot_needed
  - unknown_strategy

Enable the GNOME3 Screen Locking On Smartcard Removal

Description

Rationale

Remediation - Shell Script

Remediation - Ansible