SV-37473r2: The aliases file must be group-owned by root, sys, bin, or system. | Red Hat Enterprise Linux 5 Security Technical Implementation Guide

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Assessment Title

Rule Text

The aliases file must be group-owned by root, sys, bin, or system.

Description

Discussion Text

If the alias file is not group-owned by root or a system group, an unauthorized user may modify the file adding aliases to run malicious code or redirect e-mail.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000225

Additional Details

Responsibility

System Administrator

References

DPMS Target Red Hat 5 DISA DPMS Target Red Hat 5 2154

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.rhel11:def:283
# The aliases file must be group-owned by root, sys, bin, or system.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# sendmail is installed
# rpminfo_object (rpminfo_test)
test_1() {
  rpm -q --quiet 'sendmail' &>/dev/null
}
# test if /etc/alias is group owned by root, bin or sys
# file_object (file_test)
test_2() {
  ( [ "$(stat -c '%g' '/etc/aliases')" -eq 0 ] ) || ( [ "$(stat -c '%g' '/etc/aliases')" -eq 1 ] ) || ( [ "$(stat -c '%g' '/etc/aliases')" -eq 3 ] )
}
# test if /etc/aliases.db has same groupid as /usr/sbin/sendmail.sendmail (sendmail)
# file_object (file_test)
test_3() {
  [ "$(stat -c '%g' '/etc/aliases.db')" = "$(stat -c '%g' '/usr/sbin/sendmail.sendmail')" ]
}
# postfix is installed
# rpminfo_object (rpminfo_test)
test_4() {
  rpm -q --quiet 'postfix' &>/dev/null
}
# test if /etc/postfix/aliases.db is group-owned by root (postfix) 
# file_object (file_test)
test_5() {
  [ "$(stat -c '%g' '/etc/postfix/aliases.db')" -eq 0 ]
}
# test if /etc/aliases group owned by root (postfix)
# file_object (file_test)
test_6() {
  [ "$(stat -c '%g' '/etc/aliases')" -eq 0 ]
}
# test if /etc/postfix/aliases is group owned by root (postfix)
# file_object (file_test)
test_7() {
  [ "$(stat -c '%g' '/etc/postfix/aliases')" -eq 0 ]
}
# sendmail is not installed
# rpminfo_object (rpminfo_test)
test_8() {
  rpm -q --quiet 'sendmail' &>/dev/null
}
# postfix is not installed
# rpminfo_object (rpminfo_test)
test_9() {
  rpm -q --quiet 'postfix' &>/dev/null
}

if ! ( ! ( test_1 && test_2 && test_3 ) || ! ( test_4 && test_5 && ! ( test_6 || test_7 ) ) || ! ( test_8 && test_9 ) ); 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.rhel11:def:283

if rpm -q sendmail &> /dev/null; then
    if [ ! -f "/etc/aliases" ] || [ ! -f "/etc/aliases.db" ]; then echo "FAIL"; exit 1; fi
    if [ ! -g "/etc/aliases" ] || [ ! -g "/etc/aliases.db" ]; then echo "FAIL"; exit 1; fi
    if [ $(stat -c "%G" /etc/aliases) != "root" ] || [ $(stat -c "%G" /etc/aliases.db) != "smmsp" ]; then echo "FAIL"; exit 1; fi
    if [ $(stat -c "%g" /etc/aliases) != $(stat -c "%G" /usr/sbin/sendmail.sendmail) ]; then echo "FAIL"; exit 1; fi
else
    if rpm -q postfix &> /dev/null; then
        if [ ! -f "/etc/postfix/aliases" ] || [ ! -f "/etc/postfix/aliases.db" ]; then echo "FAIL"; exit 1; fi
        if [ ! -g "/etc/postfix/aliases" ] || [ ! -g "/etc/postfix/aliases.db" ]; then echo "FAIL"; exit 1; fi
        if [ $(stat -c "%G" /etc/postfix/aliases) != "root" ] || [ $(stat -c "%G" /etc/postfix/aliases.db) != "root" ]; then echo "FAIL"; exit 1; fi
    else
        echo "PASS"; exit 0;
    fi
fi
echo "PASS"; exit 0

Remediation

Change the group-owner of the /etc/aliases file.

Procedure:
for sendmail:
# chgrp root /etc/aliases
# chgrp smmsp /etc/aliases.db

The aliases.db file must be owned by the same system group as sendmail, which is smmsp by default.

for postfix
# chgrp root /etc/postfix/aliases
# chgrp root /etc/postfix/aliases.db