SV-204625r991589: The Red Hat Enterprise Linux operating system must not be performing packet forwarding unless the system is a router. | Red Hat Enterprise Linux 7 STIG SCAP Benchmark

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Assessment Title

Rule Text

The Red Hat Enterprise Linux operating system must not be performing packet forwarding unless the system is a router.

Description

Discussion Text

Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000366SV-86933V-72309

References

DPMS Target Red Hat Enterprise Linux 7 DISA DPMS Target Red Hat Enterprise Linux 7 2899

Checks

DISA STIG (Manual Reference)

Verify the system is not performing packet forwarding, unless the system is a router.

     # grep -r net.ipv4.ip_forward /run/sysctl.d/* /etc/sysctl.d/* /usr/local/lib/sysctl.d/* /usr/lib/sysctl.d/* /lib/sysctl.d/* /etc/sysctl.conf 2> /dev/null
     net.ipv4.ip_forward = 0

If "net.ipv4.ip_forward" is not configured in the /etc/sysctl.conf file or in any of the other sysctl.d directories, is commented out, or does not have a value of "0", this is a finding.

Check that the operating system does not implement IP forwarding using the following command:

     # /sbin/sysctl -a | grep net.ipv4.ip_forward
     net.ipv4.ip_forward = 0

If IP forwarding value is "1" and the system is hosting any application, database, or web servers, this is a finding.

If conflicting results are returned, this is a finding.

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.rhel7:def:290
# The Red Hat Enterprise Linux operating system must not be performing packet forwarding unless the system is a router.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.
#
# MANUAL REVIEW REQUIRED -- the module(s) below could not be reconstructed
# into working code from curated SCC reference data, and are excluded from
# the automated result:
#   - textfilecontent54_object (textfilecontent54_test): <set> composition (base object oval:mil.disa.stig.rhel7:obj:2289, oval:mil.disa.stig.rhel7:obj:20462501): member unresolved -- no extractor for field "subexpression"

# kernel runtime parameter net.ipv4.ip_forward set to 0
# sysctl_object (sysctl_test)
test_2() {
  [ "$(cat /proc/sys/net/ipv4/ip_forward)" -eq 0 ]
}

if test_2; then
  echo "PASS (automated portion only -- MANUAL REVIEW still required, see notes above)"
else
  echo "FAIL (or see MANUAL REVIEW note above)"
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.rhel7:def:290

if [ ! -f "/etc/sysctl.conf" ]; then echo "PASS"; exit 0; fi
if grep -qE "^[\s]*net\.ipv4\.ip_forward[\s]*=[\s]*0[\s]*$" /etc/sysctl.conf; then echo "PASS"; exit 0; fi
if [ ! -d "/etc/sysctl.d" ]; then echo "PASS"; exit 0; fi
for file in /etc/sysctl.d/*.conf; do
    if grep -qE "^[\s]*net\.ipv4\.ip_forward[\s]*=[\s]*0[\s]*$" "$file"; then echo "PASS"; exit 0; fi
done
echo "FAIL"; exit 1

if ! sysctl -n net.ipv4.ip_forward | grep -q "^0$"; then echo "FAIL"; exit 1; fi
echo "PASS"; exit 0

Remediation

Set the system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" or a configuration file in the /etc/sysctl.d/ directory (or modify the line to have the required value):

     net.ipv4.ip_forward = 0

Issue the following command to make the changes take effect:

     # sysctl --system