SV-230427r1017228: Successful/unsuccessful uses of postdrop in RHEL 8 must generate an audit record. | Red Hat Enterprise Linux 8 STIG SCAP Benchmark

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Assessment Title

Rule Text

Successful/unsuccessful uses of postdrop in RHEL 8 must generate an audit record.

Description

Discussion Text

Reconstruction of harmful events or forensic analysis is not possible if audit records do not contain enough information. At a minimum, the organization must audit the full-text recording of privileged commands. The organization must maintain audit trails in sufficient detail to reconstruct events to determine the cause and impact of compromise. The "postdrop" command creates a file in the maildrop directory and copies its standard input to the file. When a user logs on, the AUID is set to the UID of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to "-1". The AUID representation is an unsigned 32-bit integer, which equals "4294967295". The audit system interprets "-1", "4294967295", and "unset" in the same way. Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

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

IA Controls

NIST SP 800-53

Not mappedCCI-000169

References

DPMS Target Red Hat Enterprise Linux 8 DISA DPMS Target Red Hat Enterprise Linux 8 2921

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.rhel8os:def:230427
# Successful/unsuccessful uses of postdrop in RHEL 8 must generate an audit record.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# Audit invocations of /usr/sbin/postdrop
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  grep -Pq '^\s*-a\s+(always,exit|exit,always)(?:\s+-S\s+all)?\s+-F\s+path=/usr/sbin/postdrop\s+(-F\s+perm=([rwa]*x[rwa]*)\s+)?-F\s+auid>=1000\s+-F\s+auid!=(4294967295|-1|unset)(\s+(-k\s+|-F\s+key=)\S+)?\s*$' '/etc/audit/audit.rules' &>/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
# DISA STIG / SCAP compliance check oval:mil.disa.stig.rhel8os:def:230427


audit_rule_exists=$(grep -q "^\\s*-a\\s+(always,exit|exit,always)(?:\\s+-S\\s+all)?\\s+-F\\s+path=/usr/sbin/postdrop\\s+(-F\\s+perm=([rwa]*x[rwa]*)\\s+)?-F\\s+auid>=1000\\s+-F\\s+auid != (4294967295|-1|unset)(\\s+(-k\\s+|-F\\s+key=)\\S+)?\\s*$" /etc/audit/rules.d/audit.rules && echo "TRUE" || echo "FALSE")

if [ "$audit_rule_exists" = "TRUE" ]; then
  echo "PASS"
  exit 0
else
  echo "FAIL"
  exit 1
fi

Remediation

Configure the audit system to generate an audit event for any successful/unsuccessful uses of the "postdrop" by adding or updating the following rule in the "/etc/audit/rules.d/audit.rules" file:

-a always,exit -F path=/usr/sbin/postdrop -F perm=x -F auid>=1000 -F auid!=unset -k privileged-unix-update

The audit daemon must be restarted for the changes to take effect.