SV-230291r1069303: The RHEL 8 SSH daemon must not allow Kerberos authentication, except to fulfill documented and validated mission requirements. | Red Hat Enterprise Linux 8 STIG SCAP Benchmark

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Assessment Title

Rule Text

The RHEL 8 SSH daemon must not allow Kerberos authentication, except to fulfill documented and validated mission requirements.

Description

Discussion Text

Configuring these settings for the SSH daemon provides additional assurance that remote logon via SSH will not use unused methods of authentication, even in the event of misconfiguration elsewhere.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000366

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:230291
# The RHEL 8 SSH daemon must not allow Kerberos authentication, except to fulfill documented and validated mission requirements.
# 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:KerberosAuthentication == no
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  (sed -En 's/^\s*(?i)KerberosAuthentication(?-i)\s+(\w+)\s*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -Pq '^(no|"no")$'
}

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:mil.disa.stig.rhel8os:def:230291
if [ ! -f "/etc/ssh/sshd_config" ]; then echo "PASS"; exit 0; fi
grep -qE "^\\s*(?i)KerberosAuthentication(?-i)\\s+(\\w+)\\s*(?:|(?:#.*))?$" "/etc/ssh/sshd_config" || echo "PASS"; exit 0
awk '/^\\s*(?i)KerberosAuthentication(?-i)\\s+no\\s*(?:|(?:#.*))?$/ {print $0; exit 0}' "/etc/ssh/sshd_config" > /dev/null && echo "PASS" || echo "FAIL"; exit 1

Remediation

Configure the SSH daemon to not allow Kerberos authentication.

Add the following line in "/etc/ssh/sshd_config", or uncomment the line and set the value to "no":

KerberosAuthentication no

The SSH daemon must be restarted for the changes to take effect. To restart the SSH daemon, run the following command:

$ sudo systemctl restart sshd.service