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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/true
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
Updated



Remediation - Kubernetes Patch

---
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
spec:
  config:
    ignition:

Remediation - Shell Script

# Remediation is applicable only in certain platforms
if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; 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/true#g' /etc/modprobe.d/cramfs.conf

Remediation - Ansible

- 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