SV-274159r1120465: Amazon Linux 2023 must insure all interactive users have a primary group that exists. | Amazon Linux 2023 STIG SCAP Benchmark

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Assessment Title

Rule Text

Amazon Linux 2023 must insure all interactive users have a primary group that exists.

Description

Discussion Text

If a user is assigned the group identifier (GID) of a group that does not exist on the system, and a group with the GID is subsequently created, the user may have unintended rights to any files associated with the group. Satisfies: SRG-OS-000104-GPOS-00051, SRG-OS-000121-GPOS-00062, SRG-OS-000042-GPOS-00020

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

IA Controls

NIST SP 800-53

Not mappedCCI-000764Not mappedCCI-000804Not mappedCCI-000135

References

DPMS Target Amazon Linux 2023 DISA DPMS Target Amazon Linux 2023 5700

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.amzlx23os:def:274159
# Amazon Linux 2023 must insure all interactive users have a primary group that exists.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# All local users have valid GID
# password_object (password_test)
test_1() {
  [ "$(getent passwd '.*' | cut -d: -f4)" = "$(sed -En 's/^[^:#]*:[^:]*:(\d+)/\1/p' '/etc/group')" ]
}

if test_1; 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.amzlx23os:def:274159

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

declare -a users
while IFS=: read -r username _ _ _ _ _ _ _ gid _; do users+=("$username $gid"); done < /etc/passwd

for user in "${users[@]}"; do
  username=$(echo "$user" | cut -d''-f1)
  gid=$(echo "$user" | cut -d' ' -f6)
  if ! grep -q "^$gid:" /etc/group; then
    echo "FAIL"; exit 1
  fi
done

echo "PASS"; exit 0

Remediation

Configure Amazon Linux 2023 so that all GIDs are referenced in "/etc/passwd" are defined in "/etc/group".

Edit the file "/etc/passwd" and ensure that every user's GID is a valid GID.