Add nosuid Option to Removable Media Partitions

An XCCDF Rule

Description

The nosuid mount option prevents set-user-identifier (SUID) and set-group-identifier (SGID) permissions from taking effect. These permissions allow users to execute binaries with the same permissions as the owner and group of the file respectively. Users should not be allowed to introduce SUID and SGID files into the system via partitions mounted from removeable media. Add the nosuid option to the fourth column of /etc/fstab for the line which controls mounting of any removable media partitions.

Rationale

The presence of SUID and SGID executables should be tightly controlled. Allowing users to introduce SUID or SGID binaries from partitions mounted off of removable media would allow them to introduce their own highly-privileged programs.

ID: xccdf_org.ssgproject.content_rule_mount_option_nosuid_removable_partitions
Severity: Medium
References: 11 12 13 14 15 16 18 3 5 8 9

APO01.06 APO13.01 BAI10.01 BAI10.02 BAI10.03 BAI10.05 DSS01.04 DSS05.02 DSS05.03 DSS05.04 DSS05.05 DSS05.06 DSS05.07 DSS06.02 DSS06.03 DSS06.06

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 5.2 SR 7.6

A.10.1.1 A.11.1.4 A.11.1.5 A.11.2.1 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.13.1.3 A.13.2.1 A.13.2.3 A.13.2.4 A.14.1.2 A.14.1.3 A.14.2.2 A.14.2.3 A.14.2.4 A.6.1.2 A.6.2.1 A.6.2.2 A.7.1.1 A.7.1.2 A.7.3.1 A.8.2.1 A.8.2.2 A.8.2.3 A.8.3.1 A.8.3.3 A.9.1.1 A.9.1.2 A.9.2.1 A.9.2.3 A.9.4.1 A.9.4.4 A.9.4.5

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-4 PR.AC-6 PR.DS-5 PR.IP-1 PR.PT-2 PR.PT-3

SRG-OS-000480-GPOS-00227
Updated: about 1 year ago

# 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="nosuid"

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

- 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 nosuid 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,nosuid \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_nosuid_removable_partitions
  - no_reboot_needed

Add nosuid Option to Removable Media Partitions

Description

Rationale

Remediation - Shell Script

Remediation - Ansible