SV-204588r991589: The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not allow authentication using RSA rhosts authentication. | 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 allow authentication using RSA rhosts authentication.

Description

Discussion Text

Configuring this setting for the SSH daemon provides additional assurance that remote logon via SSH will require a password, 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-000366V-72239SV-86863

References

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

Checks

DISA STIG (Manual Reference)

Check the version of the operating system with the following command:

# cat /etc/redhat-release

If the release is 7.4 or newer this requirement is Not Applicable.

Verify the SSH daemon does not allow authentication using RSA rhosts authentication.

To determine how the SSH daemon's "RhostsRSAAuthentication" option is set, run the following command:

# grep RhostsRSAAuthentication /etc/ssh/sshd_config
RhostsRSAAuthentication no

If the value is returned as "yes", the returned line is commented out, or no output is returned, 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:1379
# The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not allow authentication using RSA rhosts authentication.
# 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 )
}
# package openssh-server is version 7.4 or higher
# rpminfo_object (rpminfo_test)
test_2() {
  (rpm -q --qf '%|EPOCH?{%{EPOCH}}:{0}|:%{VERSION}-%{RELEASE}' 'openssh-server') | grep -qxF '0:7.4p1-0'
}
# Check RhostsRSAAuthentication in /etc/ssh/sshd_config
# textfilecontent54_object (textfilecontent54_test)
test_3() {
  (sed -En 's/^[\s]*(?i)RhostsRSAAuthentication(?-i)[\s]+(\w+)[\s]*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -qxF 'no'
}

if ( test_1 || ( test_2 || test_3 ) ); 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.rhel7:def:1379

if ! rpm -q openssh-server &> /dev/null; then
  echo "PASS"
  exit 0
fi

if ! rpm -q openssh-server &> /dev/null || rpm -qp -v openssh-server | grep -qE '7\.4p1-0|7\.4p1-.*'; then
  echo "FAIL"
  exit 1
fi

if ! grep -qE '^[[:space:]]*(?i)RhostsRSAAuthentication(?-i)[[:space:]]+no[[:space:]]*(?:#|.*)?$' /etc/ssh/sshd_config; then
  echo "FAIL"
  exit 1
fi

echo "PASS"
exit 0

Remediation

Configure the SSH daemon to not allow authentication using RSA rhosts authentication.

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

RhostsRSAAuthentication no

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