SV-257981r1101970: RHEL 9 must display the Standard Mandatory DOD Notice and Consent Banner before granting local or remote access to the system via a SSH logon. | Red Hat Enterprise Linux 9 STIG SCAP Benchmark

Loading benchmark…

Assessment Title

Rule Text

RHEL 9 must display the Standard Mandatory DOD Notice and Consent Banner before granting local or remote access to the system via a SSH logon.

Description

Discussion Text

The warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers. Alternatively, systems whose ownership should not be obvious should ensure usage of a banner that does not provide easy attribution. Satisfies: SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088

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

IA Controls

NIST SP 800-53

Not mappedCCI-000048Not mappedCCI-001384Not mappedCCI-001385Not mappedCCI-001386Not mappedCCI-001387Not mappedCCI-001388

References

DPMS Target Red Hat Enterprise Linux 9 DISA DPMS Target Red Hat Enterprise Linux 9 5551

Checks

DISA STIG (Manual Reference)

Verify any SSH connection to RHEL 9 displays the Standard Mandatory DOD Notice and Consent Banner before granting access to the system.

Check for the location of the banner file being used with the following command:

$ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*banner'
/etc/ssh/sshd_config.d/80-bannerPointer.conf:Banner /etc/issue

This command will return the banner keyword and the name of the file that contains the SSH banner (in this case "/etc/issue").

If the line is commented out, 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.rhel9os:def:257981
# RHEL 9 must display the Standard Mandatory DOD Notice and Consent Banner before granting local or remote access to the system via a SSH logon.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# /etc/ssh/sshd_config:banner == /filepath
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  ( (sed -En 's/^\s*(?i)banner(?-i)[ \t\"]+([\w\\/]+)[\"\s]*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -Pq '^\/.+$' ) || ( (grep -rhP --include='*' '^\s*(?i)banner(?-i)[ \t\"]+([\w\/]+)[\"\s]*(?:|(?:#.*))?$' '/etc/ssh/sshd_config.d' | sed -En 's/^\s*(?i)banner(?-i)[ \t\"]+([\w\\/]+)[\"\s]*(?:|(?:#.*))?$/\1/p') | grep -Pq '^\/.+$' )
}
# /etc/ssh/sshd_config:banner != none
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  ( ! ( grep -Pq '^\s*(?i)banner(?-i)[ \t]*(?:none[\s]*|(?:#.*))?$' '/etc/ssh/sshd_config' &>/dev/null ) ) || ( ! ( grep -rqP --include='*' '^\s*(?i)banner(?-i)[ \t]*(?:none[\s]*|(?:#.*))?$' '/etc/ssh/sshd_config.d' &>/dev/null ) )
}

if ( test_1 && test_2 ); 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:mil.disa.stig.rhel9os:def:257981
if [ ! -f "/etc/ssh/sshd_config" ]; then echo "PASS"; exit 0; fi
if grep -q "^\\s*(?i)banner(?-i)[ \\t\\\"]+([\\w\\/]+)[\\\"\\s]*(?:|(?:#.*))?$" /etc/ssh/sshd_config && [ ! -z "$(grep -o '^\\s*(?i)banner(?-i)' /etc/ssh/sshd_config | wc -l)" ]; then echo "PASS"; exit 0; fi
if [ -d "/etc/ssh/sshd_config.d" ]; then for file in /etc/ssh/sshd_config.d/*; do if [ -f "$file" ]; then if grep -q "^\\s*(?i)banner(?-i)[ \\t\\\"]+([\\w\\/]+)[\\\"\\s]*(?:|(?:#.*))?$" "$file" && [ ! -z "$(grep -o '^\\s*(?i)banner(?-i)' "$file" | wc -l)" ]; then echo "PASS"; exit 0; fi; fi; done; fi
echo "FAIL"; exit 1

Remediation

Configure RHEL 9 to display the Standard Mandatory DOD Notice and Consent Banner before granting access to the system via ssh.

Edit the "etc/ssh/sshd_config" file or a file in "/etc/ssh/sshd_config.d" to uncomment the banner keyword and configure it to point to a file that will contain the logon banner (this file may be named differently or be in a different location if using a version of SSH that is provided by a third-party vendor).

An example configuration line is:

Banner /etc/issue