Disable GNOME3 Automount running

An XCCDF Rule

Description

The system's default desktop environment, GNOME3, will mount devices and removable media (such as DVDs, CDs and USB flash drives) whenever they are inserted into the system. To disable autorun-never within GNOME3, add or set autorun-never to true in /etc/dconf/db/local.d/00-security-settings. For example:

[org/gnome/desktop/media-handling]
autorun-never=true

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/desktop/media-handling/autorun-never

After the settings have been set, run dconf update.

Rationale

Automatically mounting file systems permits easy introduction of unknown devices, thereby facilitating malicious activity. Disabling automatic mount running in GNOME3 can prevent the introduction of malware via removable media. It will, however, also prevent desktop users from legitimate use of removable media.

ID: xccdf_org.ssgproject.content_rule_dconf_gnome_disable_autorun
Severity: Low
References: 12 16

APO13.01 DSS01.04 DSS05.03 DSS05.04 DSS05.05 DSS05.07 DSS06.03

3.1.7

CCI-000366 CCI-000778 CCI-001958

4.3.3.2.2 4.3.3.5.2 4.3.3.6.6 4.3.3.7.2 4.3.3.7.4

SR 1.1 SR 1.13 SR 1.2 SR 1.4 SR 1.5 SR 1.9 SR 2.1 SR 2.6

A.11.2.6 A.13.1.1 A.13.2.1 A.6.2.1 A.6.2.2 A.7.1.1 A.9.2.1

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

PR.AC-3 PR.AC-6

SRG-OS-000114-GPOS-00059 SRG-OS-000378-GPOS-00163 SRG-OS-000480-GPOS-00227

CCE-83742-7

1.8.8
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/desktop/media-handling\\]" "/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 [ "${#SETTINGSFILES[@]}" -ne 0 ]
then
    if grep -q "^\\s*autorun-never\\s*=" "${SETTINGSFILES[@]}"
    then
        
        sed -Ei "s/(^\s*)autorun-never(\s*=)/#\1autorun-never\2/g" "${SETTINGSFILES[@]}"
    fi
fi

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

escaped_value="$(sed -e 's/\\/\\\\/g' <<< "true")"
if grep -q "^\\s*autorun-never\\s*=" "${DCONFFILE}"
then
        sed -i "s/\\s*autorun-never\\s*=\\s*.*/autorun-never=${escaped_value}/g" "${DCONFFILE}"
    else
        sed -i "\\|\\[org/gnome/desktop/media-handling\\]|a\\autorun-never=${escaped_value}" "${DCONFFILE}"
fi

dconf update
# Check for setting in any of the DConf db directories
LOCKFILES=$(grep -r "^/org/gnome/desktop/media-handling/autorun-never$" "/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 "${LOCKFILES}" ]]
then
    sed -i -E "s|^/org/gnome/desktop/media-handling/autorun-never$|#&|" "${LOCKFILES[@]}"
fi

if ! grep -qr "^/org/gnome/desktop/media-handling/autorun-never$" /etc/dconf/db/local.d/
then
    echo "/org/gnome/desktop/media-handling/autorun-never" >> "/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:
  - CCE-83742-7
  - NIST-800-171-3.1.7  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_autorun
  - low_complexity
  - low_severity
  - medium_disruption
  - no_reboot_needed
  - unknown_strategy

- name: Disable GNOME3 Automounting - autorun-never
  ini_file:
    dest: /etc/dconf/db/local.d/00-security-settings
    section: org/gnome/desktop/media-handling
    option: autorun-never
    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:
  - CCE-83742-7
  - NIST-800-171-3.1.7
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_autorun
  - low_complexity
  - low_severity
  - medium_disruption
  - no_reboot_needed
  - unknown_strategy

- name: Prevent user modification of GNOME3 Automounting - autorun-never
  lineinfile:
    path: /etc/dconf/db/local.d/locks/00-security-settings-lock
    regexp: ^/org/gnome/desktop/media-handling/autorun-never$
    line: /org/gnome/desktop/media-handling/autorun-never
    create: true
  when:
  - '"gdm" in ansible_facts.packages'
  - ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - CCE-83742-7
  - NIST-800-171-3.1.7
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_autorun
  - low_complexity
  - low_severity
  - 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:
  - CCE-83742-7
  - NIST-800-171-3.1.7
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - dconf_gnome_disable_autorun
  - low_complexity
  - low_severity
  - medium_disruption
  - no_reboot_needed
  - unknown_strategy

Disable GNOME3 Automount running

Description

Rationale

Remediation - Shell Script

Remediation - Ansible