SV-257983r1262145: RHEL 9 SSHD must accept public key authentication. | Red Hat Enterprise Linux 9 STIG SCAP Benchmark

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Assessment Title

Rule Text

RHEL 9 SSHD must accept public key authentication.

Description

Discussion Text

Without the use of multifactor authentication, the ease of access to privileged functions is greatly increased. Multifactor authentication requires using two or more factors to achieve authentication. A privileged account is defined as an information system account with authorizations of a privileged user. A DoW common access card (CAC) with DoW-approved PKI is an example of multifactor authentication. Satisfies: SRG-OS-000105-GPOS-00052, SRG-OS-000106-GPOS-00053, SRG-OS-000107-GPOS-00054, SRG-OS-000108-GPOS-00055

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

IA Controls

NIST SP 800-53

Not mappedCCI-000765Not mappedCCI-000766Not mappedCCI-000767Not mappedCCI-000768

References

DPMS Target Red Hat Enterprise Linux 9 DISA DPMS Target Red Hat Enterprise Linux 9 5551

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.rhel9os:def:257983
# RHEL 9 SSHD must accept public key authentication.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# sshd_config includes sshd_config.d
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  (sed -En 's/^\s*include\s+(.*)\s*$/\1/p' '/etc/ssh/sshd_config') | grep -qxF '/etc/ssh/sshd_config.d/*.conf'
}
# /etc/ssh/sshd_config.d: PubkeyAuthentication is set to yes
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  (grep -rhP --include='*.conf' '^\s*(?i)PubkeyAuthentication(?-i)[ \t]+([\w\"]+)[\s]*(?:|(?:#.*))?$' '/etc/ssh/sshd_config.d' | sed -En 's/^\s*(?i)PubkeyAuthentication(?-i)[ \t]+([\w\"]+)[\s]*(?:|(?:#.*))?$/\1/p') | grep -Pq '^(yes|"yes")$'
}
# /etc/ssh/sshd_config: PubkeyAuthentication is set to yes
# textfilecontent54_object (textfilecontent54_test)
test_3() {
  (sed -En 's/^\s*(?i)PubkeyAuthentication(?-i)[ \t]+([\w\"]+)[\s]*(?:|(?:#.*))?$/\1/p' '/etc/ssh/sshd_config') | grep -Pq '^(yes|"yes")$'
}

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.rhel9os:def:257983

if grep -qE '^\\s*(?i)PubkeyAuthentication(?-i)[ \\t]+yes[\\s]*(?:|(?:#.*))?$' /etc/ssh/sshd_config || \
   grep -qE '^\\s*(?i)PubkeyAuthentication(?-i)[ \\t]+yes[\\s]*(?:|(?:#.*))?$' /etc/ssh/sshd_config.d/*.conf; then
    echo "PASS"
    exit 0
else
    echo "FAIL"
    exit 1
fi

Remediation

To configure the system, add or modify the following line in "/etc/ssh/sshd_config" or in a file in "/etc/ssh/sshd_config.d".

PubkeyAuthentication yes

Restart the SSH daemon for the settings to take effect:

$ sudo systemctl restart sshd.service