SV-204600r991589: The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon performs strict mode checking of home directory configuration files. | 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 performs strict mode checking of home directory configuration files.

Description

Discussion Text

If other users have access to modify user-specific SSH configuration files, they may be able to log on to the system as another user.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000366SV-86887V-72263

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 performs strict mode checking of home directory configuration files.

The location of the "sshd_config" file may vary if a different daemon is in use.

Inspect the "sshd_config" file with the following command:

# grep -i strictmodes /etc/ssh/sshd_config

StrictModes yes

If "StrictModes" is set to "no", is missing, 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:164
# The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon performs strict mode checking of home directory configuration files.
# 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 StrictModes in /etc/ssh/sshd_config
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  (sed -En 's/^[\s]*(?i)StrictModes(?-i)[\s]+(\w+)[\s]*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -qxF 'yes'
}

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 Definition: oval:mil.disa.stig.rhel7:def:164


if rpm -q openssh-server > /dev/null 2>&1; then
    if grep -q "^[\\s]*(?i)StrictModes(?-i)[\\s]+yes[\\s]*(?:#|.*)?$" /etc/ssh/sshd_config; then
        echo "PASS"
        exit 0
    else
        echo "FAIL"
        exit 1
    fi
else
    echo "PASS"
    exit 0
fi

Remediation

Uncomment the "StrictModes" 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 "yes":

StrictModes yes

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