SV-204601r991589: The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon uses privilege separation. | 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 uses privilege separation.

Description

Discussion Text

SSH daemon privilege separation causes the SSH process to drop root privileges when not needed, which would decrease the impact of software vulnerabilities in the unprivileged section.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000366SV-86889V-72265

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 privilege separation.

Check that the SSH daemon performs privilege separation with the following command:

# grep -i usepriv /etc/ssh/sshd_config

UsePrivilegeSeparation sandbox

If the "UsePrivilegeSeparation" keyword 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:171
# The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon uses privilege separation.
# 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 UsePrivilegeSeparation in /etc/ssh/sshd_config
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  ( (sed -En 's/^[\s]*(?i)UsePrivilegeSeparation(?-i)[\s]+(\w+)[\s]*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -qxF 'sandbox' ) || ( (sed -En 's/^[\s]*(?i)UsePrivilegeSeparation(?-i)[\s]+(\w+)[\s]*(?:|(?:#.*))?$/\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
# DISA STIG / SCAP compliance check for RHEL SSH daemon privilege separation
if rpm -q --quiet openssh-server; then
    if [ ! -f "/etc/ssh/sshd_config" ]; then
        echo "PASS"; exit 0;
    fi
    if grep -qE "^[\s]*(?i)UsePrivilegeSeparation[\s]+(sandbox|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 "UsePrivilegeSeparation" 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 "sandbox" or "yes":

UsePrivilegeSeparation sandbox

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