SV-204598r958796: The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not permit Generic Security Service Application Program Interface (GSSAPI) authentication unless needed. | Red Hat Enterprise Linux 7 STIG SCAP Benchmark

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Assessment Title

Rule Text

The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not permit Generic Security Service Application Program Interface (GSSAPI) authentication unless needed.

Description

Discussion Text

GSSAPI authentication is used to provide additional authentication mechanisms to applications. Allowing GSSAPI authentication through SSH exposes the system's GSSAPI to remote hosts, increasing the attack surface of the system. GSSAPI authentication must be disabled unless needed.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000318Not mappedCCI-000368Not mappedCCI-001812Not mappedCCI-001813Not mappedCCI-001814V-72259SV-86883

References

DPMS Target Red Hat Enterprise Linux 7 DISA DPMS Target Red Hat Enterprise Linux 7 2899

Checks

DISA STIG (Manual Reference)

Verify the SSH daemon does not permit GSSAPI authentication unless approved.

Check that the SSH daemon does not permit GSSAPI authentication with the following command:

# grep -i gssapiauth /etc/ssh/sshd_config
GSSAPIAuthentication no

If the "GSSAPIAuthentication" keyword is missing, is set to "yes" and is not documented with the Information System Security Officer (ISSO), or the returned 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.rhel7:def:160
# The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not permit Generic Security Service Application Program Interface (GSSAPI) authentication unless needed.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# package openssh-server is removed
# rpminfo_object (rpminfo_test)
test_1() {
  ! ( rpm -q --quiet 'openssh-server' &>/dev/null )
}
# Check GSSAPIAuthentication in /etc/ssh/sshd_config
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  (sed -En 's/^[\s]*(?i)GSSAPIAuthentication(?-i)[\s]+(\w+)[\s]*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -qxF 'no'
}

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
# DISA STIG / SCAP compliance check for RHEL SSH GSSAPIAuthentication setting
if ! command -v rpm &> /dev/null; then
  echo "PASS"
  exit 0
fi

if ! rpm -qa | grep -q openssh-server; then
  echo "PASS"
  exit 0
fi

if ! grep -q "^[\\s]*(?i)GSSAPIAuthentication(?-i)[\\s]+no[\\s]*(?:|(?:#.*))?$" /etc/ssh/sshd_config; then
  echo "FAIL"
  exit 1
fi

echo "PASS"
exit 0

Remediation

Uncomment the "GSSAPIAuthentication" keyword in "/etc/ssh/sshd_config" (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) and set the value to "no": 

GSSAPIAuthentication no

The SSH service must be restarted for changes to take effect.

If GSSAPI authentication is required, it must be documented, to include the location of the configuration file, with the ISSO.