SV-253134r991589: TOSS must use reverse path filtering on all IPv4 interfaces. | Tri-Lab Operating System Stack (TOSS) 4 STIG SCAP Benchmark

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Assessment Title

Rule Text

TOSS must use reverse path filtering on all IPv4 interfaces.

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. Enabling reverse path filtering drops packets with source addresses that are not routable. There is not an equivalent filter for IPv6 traffic.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000366

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:253134
# TOSS must use reverse path filtering on all IPv4 interfaces.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# net.ipv4.conf.all.rp_filter setting in kernel is 1
# sysctl_object (sysctl_test)
test_1() {
  [ "$(cat /proc/sys/net/ipv4/conf/all/rp_filter)" -eq 1 ]
}

if test_1; 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
# OVAL Definition: oval:mil.disa.stig.toss4os:def:253134
if [ ! -x "$(command -v sysctl)" ]; then echo "FAIL"; exit 1; fi
if [ ! -s /etc/sysctl.d/99-sysdefaults.conf ]; then echo "PASS"; exit 0; fi
if grep -q '^net.ipv4.conf.all.rp_filter = 1$' /etc/sysctl.d/99-sysdefaults.conf; then echo "PASS"; exit 0; else echo "FAIL"; exit 1; fi

Remediation

Configure TOSS to use reverse path filtering on all IPv4 interfaces by adding the following line to a file in the "/etc/sysctl.d" directory:

net.ipv4.conf.all.rp_filter = 1

The system configuration files need to be reloaded for the changes to take effect. To reload the contents of the files, run the following command:

$ sudo sysctl --system