SV-253072r958478: TOSS must disable mounting of cramfs. | Tri-Lab Operating System Stack (TOSS) 4 STIG SCAP Benchmark

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Assessment Title

Rule Text

TOSS must disable mounting of cramfs.

Description

Discussion Text

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Removing support for unneeded filesystem types reduces the local attack surface of the server. Compressed ROM/RAM file system (or cramfs) is a read-only file system designed for simplicity and space efficiency. It is mainly used in embedded and small footprint systems.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-000381

References

DPMS Target TOSS 4 DISA DPMS Target TOSS 4 5469

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

#!/bin/bash
# Reconstructed from oval:mil.disa.stig.toss4os:def:253072
# TOSS must disable mounting of cramfs.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# /etc/modprobe.d contains a file that contains 'install cramfs /bin/false'
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  grep -rqP --include='*' '^[ \t]*install[ \t]+cramfs[ \t]+/bin/false[ \t]*$' '/etc/modprobe.d' &>/dev/null
}
# /etc/modprobe.d contains a file that contains 'blacklist cramfs'
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  grep -rqP --include='*' '^[ \t]*blacklist[ \t]+cramfs[ \t]*$' '/etc/modprobe.d' &>/dev/null
}
# /etc/modprobe.conf contains 'install cramfs /bin/false'
# textfilecontent54_object (textfilecontent54_test)
test_3() {
  grep -Pq '^[ \t]*install[ \t]+cramfs[ \t]+/bin/false[ \t]*$' '/etc/modprobe.conf' &>/dev/null
}
# /etc/modprobe.conf contains 'blacklist cramfs'
# textfilecontent54_object (textfilecontent54_test)
test_4() {
  grep -Pq '^[ \t]*blacklist[ \t]+cramfs[ \t]*$' '/etc/modprobe.conf' &>/dev/null
}

if ( ( test_1 && test_2 ) || ( test_3 && test_4 ) ); then
  echo "PASS"
else
  echo "FAIL"
fi

Assessment Script Powered by AISandbox-executed

A standalone Shell script to assess this control automatically. Review before running it in your environment.

Syntax-checked and actually executed in an isolated sandbox (not the real system this checks) — confirmed to run without errors.

#!/bin/sh
# This script implements OVAL definition oval:mil.disa.stig.toss4os:def:253072

if [ ! -d "/etc/modprobe.d" ]; then echo "PASS"; exit 0; fi
if [ $(grep -c "install cramfs /bin/false" /etc/modprobe.d/*) -ge 1 ] && [ $(grep -c "blacklist cramfs" /etc/modprobe.d/*) -ge 1 ]; then echo "PASS"; exit 0; fi
if [ ! -f "/etc/modprobe.conf" ]; then echo "PASS"; exit 0; fi
if [ $(grep -c "install cramfs /bin/false" /etc/modprobe.conf) -ge 1 ] && [ $(grep -c "blacklist cramfs" /etc/modprobe.conf) -ge 1 ]; then echo "PASS"; exit 0; fi
echo "FAIL"; exit 1

Remediation

Configure the operating system to disable the ability to use the cramfs kernel module.

Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf":

install cramfs /bin/false
blacklist cramfs

Reboot the system for the settings to take effect.