Add noexec Option to Removable Media Partitions

An XCCDF Rule

Description

The noexec mount option prevents the direct execution of binaries on the mounted filesystem. Preventing the direct execution of binaries from removable media (such as a USB key) provides a defense against malicious software that may be present on such untrusted media. Add the noexec option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions.

Rationale

Allowing users to execute binaries from removable media such as USB keys exposes the system to potential compromise.

ID: xccdf_org.ssgproject.content_rule_mount_option_noexec_removable_partitions
Severity: Medium
References: 11 12 13 14 16 3 8 9

APO13.01 BAI10.01 BAI10.02 BAI10.03 BAI10.05 DSS01.04 DSS05.02 DSS05.03 DSS05.04 DSS05.05 DSS05.06 DSS05.07 DSS06.03 DSS06.06

CCI-000087 CCI-000366

4.3.3.2.2 4.3.3.5.1 4.3.3.5.2 4.3.3.5.3 4.3.3.5.4 4.3.3.5.5 4.3.3.5.6 4.3.3.5.7 4.3.3.5.8 4.3.3.6.1 4.3.3.6.2 4.3.3.6.3 4.3.3.6.4 4.3.3.6.5 4.3.3.6.6 4.3.3.6.7 4.3.3.6.8 4.3.3.6.9 4.3.3.7.1 4.3.3.7.2 4.3.3.7.3 4.3.3.7.4 4.3.4.3.2 4.3.4.3.3

SR 1.1 SR 1.10 SR 1.11 SR 1.12 SR 1.13 SR 1.2 SR 1.3 SR 1.4 SR 1.5 SR 1.6 SR 1.7 SR 1.8 SR 1.9 SR 2.1 SR 2.2 SR 2.3 SR 2.4 SR 2.5 SR 2.6 SR 2.7 SR 7.6

A.11.2.6 A.11.2.9 A.12.1.2 A.12.5.1 A.12.6.2 A.13.1.1 A.13.2.1 A.14.2.2 A.14.2.3 A.14.2.4 A.6.2.1 A.6.2.2 A.7.1.1 A.8.2.1 A.8.2.2 A.8.2.3 A.8.3.1 A.8.3.3 A.9.1.2 A.9.2.1

CIP-003-8 R5.1.1 CIP-003-8 R5.3 CIP-004-6 R2.3 CIP-007-3 R2.1 CIP-007-3 R2.2 CIP-007-3 R2.3 CIP-007-3 R5.1 CIP-007-3 R5.1.1 CIP-007-3 R5.1.2

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

PR.AC-3 PR.AC-6 PR.IP-1 PR.PT-2 PR.PT-3

SRG-OS-000480-GPOS-00227

1.1.19
Updated: about 1 year ago

- name: XCCDF Value var_removable_partition # promote to variable
  set_fact:
    var_removable_partition: !!str <xccdf-1.2:sub xmlns:xccdf-1.2="http://checklists.nist.gov/xccdf/1.2" idref="xccdf_org.ssgproject.content_value_var_removable_partition" use="legacy"/>
  tags:
    - always
- name: Ensure permission noexec are set on var_removable_partition
  lineinfile:
    path: /etc/fstab
    regexp: ^\s*({{ var_removable_partition }})\s+([^\s]*)\s+([^\s]*)\s+([^\s]*)(.*)$
    backrefs: true
    line: \1 \2 \3 \4,noexec \5
  when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
  tags:
  - NIST-800-53-AC-6
  - NIST-800-53-AC-6(1)
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - NIST-800-53-MP-7
  - configure_strategy
  - high_disruption
  - low_complexity
  - medium_severity
  - mount_option_noexec_removable_partitions
  - no_reboot_needed

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

var_removable_partition='<xccdf-1.2:sub xmlns:xccdf-1.2="http://checklists.nist.gov/xccdf/1.2" idref="xccdf_org.ssgproject.content_value_var_removable_partition" use="legacy"/>'

device_regex="^\s*$var_removable_partition\s\+"
mount_option="noexec"

if grep -q $device_regex /etc/fstab ; then
    previous_opts=$(grep $device_regex /etc/fstab | awk '{print $4}')
    sed -i "s|\($device_regex.*$previous_opts\)|\1,$mount_option|" /etc/fstab
else
    echo "Not remediating, because there is no record of $var_removable_partition in /etc/fstab" >&2
fi

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

Add noexec Option to Removable Media Partitions

Description

Rationale

Remediation - Ansible

Remediation - Shell Script