SV-238218r991591: The Ubuntu operating system must not allow unattended or automatic login via SSH. | Canonical Ubuntu 20.04 LTS STIG SCAP Benchmark

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Assessment Title

Rule Text

The Ubuntu operating system must not allow unattended or automatic login via SSH.

Description

Discussion Text

Failure to restrict system access to authenticated users negatively impacts Ubuntu operating system security.

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

IA Controls

NIST SP 800-53

Not mappedCCI-000366

References

DPMS Target Canonical Ubuntu 20.04 LTS DISA DPMS Target Canonical Ubuntu 20.04 LTS 5318

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.ubuntu2004:def:114
# The Ubuntu operating system must not allow unattended or automatic login via SSH.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# The PermitEmptyPasswords option is set to no in /etc/ssh/sshd_config.
# textfilecontent54_object (textfilecontent54_test)
test_1() {
  (sed -En 's/^\s*(?i)PermitEmptyPasswords(?-i)\s+(\w+)\s*$/\1/p' '/etc/ssh/sshd_config') | grep -Pq '^no$'
}
# The PermitUserEnvironment option is set to no in /etc/ssh/sshd_config.
# textfilecontent54_object (textfilecontent54_test)
test_2() {
  (sed -En 's/^\s*(?i)PermitUserEnvironment(?-i)\s+(\w+)\s*$/\1/p' '/etc/ssh/sshd_config') | grep -Pq '^no$'
}

if ( test_1 && test_2 ); then
  echo "PASS"
else
  echo "FAIL"
fi

Remediation

Configure the Ubuntu operating system to allow the SSH daemon to not allow unattended or automatic login to the system. 
 
Add or edit the following lines in the "/etc/ssh/sshd_config" file: 
 
PermitEmptyPasswords no 
PermitUserEnvironment no 
 
Restart the SSH daemon for the changes to take effect: 
 
$ sudo systemctl restart sshd.service