cis-ubuntu2004-v300-1-1-1-1

name	cis-ubuntu2004-v300-1-1-1-1
description	Ensure cramfs kernel module is not available
category	cis-storage
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","kernel-module"]
cis_id	1.1.1.1
cis_benchmark	CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure cramfs kernel module is not available

Profile

Level 1 - Server, Level 1 - Workstation, Assessment: Automated

Description

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 system. If this filesystem type is not needed, disable it.

Audit Procedure

Command Line

Verify the cramfs kernel module is not available on the system - OR - has been disabled.

Run the following script to determine if the cramfs kernel module is available on the system:

#!/usr/bin/env bash

{
   l_mod_name="cramfs" l_mod_type="fs"
   while IFS= read -r l_mod_path; do
      if [ -d "$l_mod_path/${l_mod_name}/-/\/" ] &&  [ -n "$(ls -A "$l_mod_path/${l_mod_name}/-/\/")" ]; then
         printf '%s\n' "$l_mod_name exists in $l_mod_path"
      fi
   done < <(readlink -f /usr/lib/modules/**/kernel/$l_mod_type || readlink -f /lib/modules/**/kernel/$l_mod_type)
}

If nothing is returned, the cramfs kernel module is not available on the system and no further audit steps are required.

Note: Some systems may include the cramfs filesystem as part of the kernel opposed to being available as a kernel module. In this case, the above audit will not return anything. This is also considered a passing state.