SV-218009r603264: Mail relaying must be restricted. | Red Hat Enterprise Linux 6 Security Technical Implementation Guide

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Assessment Title

Rule Text

Mail relaying must be restricted.

Description

Discussion Text

This ensures "postfix" accepts mail messages (such as cron job reports) from the local system only, and not from the network, which protects it from network attack.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000382CCE-26780-7SV-50423V-38622

References

DPMS Target Red Hat Enterprise Linux 6 DISA DPMS Target Red Hat Enterprise Linux 6 4046

Checks

DISA STIG (Manual Reference)

If the system is an authorized mail relay host, this is not applicable. 

Run the following command to ensure postfix accepts mail messages from only the local system: 

$ grep inet_interfaces /etc/postfix/main.cf

If properly configured, the output should show only "localhost". 
If it does not, 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.fso.redhat.rhel6:def:121
# Mail relaying must be restricted.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# Check inet_interfaces in /etc/postfix/main.cf
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  grep -Pq '^[\s]*inet_interfaces[\s]*=[\s]*localhost[\s]*$' '/etc/postfix/main.cf' &>/dev/null
}

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.fso.redhat.rhel6:def:121
if [ ! -f "/etc/postfix/main.cf" ]; then echo "PASS"; exit 0; fi
if [ "$(grep -E "^[\s]*inet_interfaces[\s]*=[\s]*localhost[\s]*$" /etc/postfix/main.cf | grep -c .)" -eq 1 ]; then echo "PASS"; exit 0; else echo "FAIL"; exit 1; fi

Remediation

Edit the file "/etc/postfix/main.cf" to ensure that only the following "inet_interfaces" line appears: 

inet_interfaces = localhost