SV-281257r1184757: RHEL 10 must be configured so that the Secure Shell (SSH) daemon does not allow known hosts authentication. | Red Hat Enterprise Linux 10 STIG SCAP Benchmark

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Assessment Title

Rule Text

RHEL 10 must be configured so that the Secure Shell (SSH) daemon does not allow known hosts authentication.

Description

Discussion Text

Configuring the "IgnoreUserKnownHosts" setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere. OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

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

IA Controls

NIST SP 800-53

Not mappedCCI-002696

References

DPMS Target Red Hat Enterprise Linux 10 DISA DPMS Target Red Hat Enterprise Linux 10 5733

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.rhel10os:def:281257
# RHEL 10 must be configured so that the Secure Shell (SSH) daemon does not allow known hosts authentication.
# 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:IgnoreUserKnownHosts == yes
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  (sed -En 's/^\s*(?i)IgnoreUserKnownHosts(?-i)[ \t]+([\w\"]+)[\s]*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -Pq '^(yes|"yes")$'
}
# /etc/ssh/sshd_config includes sshd_config.d
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  (sed -En 's/^\s*include\s+(.*)\s*$/\1/p' '/etc/ssh/sshd_config') | grep -qxF '/etc/ssh/sshd_config.d/*.conf'
}
# /etc/ssh/sshd_config.d:IgnoreUserKnownHosts == yes
# textfilecontent54_object (textfilecontent54_test)
test_3() {
  (grep -rhP --include='*.conf' '^\s*(?i)IgnoreUserKnownHosts(?-i)[ \t]+([\w\"]+)[\s]*(?:|(?:#.*))?$' '/etc/ssh/sshd_config.d' | sed -En 's/^\s*(?i)IgnoreUserKnownHosts(?-i)[ \t]+([\w\"]+)[\s]*(?:|(?:#.*))?$/\1/p') | grep -Pq '^(yes|"yes")$'
}

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 Definition: oval:mil.disa.stig.rhel10os:def:281257

if [ ! -f "/etc/ssh/sshd_config" ]; then
    echo "PASS"
    exit 0
fi

if [ ! -d "/etc/ssh/sshd_config.d" ]; then
    echo "PASS"
    exit 0
fi

grep -q "^\\s*include\\s+\/etc/ssh/sshd_config.d/.*\\.conf\\s*$" /etc/ssh/sshd_config || echo "PASS"

if [ ! -f "/etc/ssh/sshd_config.d/00-my-sshd-config.conf" ]; then
    echo "PASS"
    exit 0
fi

grep -q "^(yes|\"yes\")$" /etc/ssh/sshd_config.d/00-my-sshd-config.conf || echo "PASS"

echo "PASS"
exit 0

Remediation

Configure RHEL 10 SSH daemons to not allow known hosts authentication.

In "/etc/ssh/sshd_config.d", create a drop file that will lexicographically precede 50-redhat.conf and add the following line:

IgnoreUserKnownHosts yes

Restart the SSH service with the following command for the changes to take effect:

$ sudo systemctl restart sshd.service