Disable Mounting of cramfs

An XCCDF Rule

Description

To configure the system to prevent the cramfs kernel module from being loaded, add the following line to the file /etc/modprobe.d/cramfs.conf:

install cramfs /bin/false

To configure the system to prevent the cramfs from being used, add the following line to file /etc/modprobe.d/cramfs.conf:

blacklist cramfs

This effectively prevents usage of this uncommon filesystem. The cramfs filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A cramfs image can be used without having to first decompress the image.

Rationale

Removing support for unneeded filesystem types reduces the local attack surface of the server.

ID: xccdf_org.ssgproject.content_rule_kernel_module_cramfs_disabled
Severity: Low
References: 11 14 3 9

BAI10.01 BAI10.02 BAI10.03 BAI10.05 DSS05.02 DSS05.05 DSS06.06

3.4.6

CCI-000381

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.12.1.2 A.12.5.1 A.12.6.2 A.14.2.2 A.14.2.3 A.14.2.4 A.9.1.2

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

PR.IP-1 PR.PT-3

SRG-OS-000095-GPOS-00049

1.1.1.1

SV-230498r1017281_rule
Updated: about 1 month ago

Remediation Templates

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - DISA-STIG-RHEL-08-040025
  - NIST-800-171-3.4.6  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - disable_strategy
  - kernel_module_cramfs_disabled
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required
- name: Ensure kernel module 'cramfs' is disabled
  lineinfile:
    create: true
    dest: /etc/modprobe.d/cramfs.conf
    regexp: install\s+cramfs
    line: install cramfs /bin/false
  when: '"kernel" in ansible_facts.packages'
  tags:
  - DISA-STIG-RHEL-08-040025
  - NIST-800-171-3.4.6
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - disable_strategy
  - kernel_module_cramfs_disabled
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required

- name: Ensure kernel module 'cramfs' is blacklisted
  lineinfile:
    create: true
    dest: /etc/modprobe.d/cramfs.conf
    regexp: ^blacklist cramfs$
    line: blacklist cramfs
  when: '"kernel" in ansible_facts.packages'
  tags:
  - DISA-STIG-RHEL-08-040025
  - NIST-800-171-3.4.6
  - NIST-800-53-CM-6(a)
  - NIST-800-53-CM-7(a)
  - NIST-800-53-CM-7(b)
  - disable_strategy
  - kernel_module_cramfs_disabled
  - low_complexity
  - low_severity
  - medium_disruption
  - reboot_required

apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
spec:
  config:
    ignition:
      version: 3.1.0    storage:
      files:
      - contents:
          source: data:,install%20cramfs%20/bin/false%0Ablacklist%20cramfs%0A
        mode: 0644
        path: /etc/modprobe.d/cramfs.conf
        overwrite: true

# Remediation is applicable only in certain platforms
if rpm --quiet -q kernel; then
if LC_ALL=C grep -q -m 1 "^install cramfs" /etc/modprobe.d/cramfs.conf ; then
	
	sed -i 's#^install cramfs.*#install cramfs /bin/false#g' /etc/modprobe.d/cramfs.conf
else	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/cramfs.conf
	echo "install cramfs /bin/false" >> /etc/modprobe.d/cramfs.conf
fi

if ! LC_ALL=C grep -q -m 1 "^blacklist cramfs$" /etc/modprobe.d/cramfs.conf ; then
	echo "blacklist cramfs" >> /etc/modprobe.d/cramfs.conf
fi

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

Disable Mounting of cramfs

Description

Rationale

Remediation Templates

An Ansible Snippet

A Kubernetes Patch

A Shell Script