Ensure default group for the root account is GID 0

MediumLevel 1Automatedcos

Description

The usermod command can be used to specify which group the root user belongs to. This affects permissions of files that are created by the root user. Using GID 0 for the root account helps prevent root -owned files from accidentally becoming accessible to non-privileged users.

How it is checked

Audit method: Shell command

shell

alt0() { command -v cut >/dev/null 2>&1 || { echo "step1: cut not installed"; return 1; }; command -v grep >/dev/null 2>&1 || { echo "step1: grep not installed"; return 1; }; o=$(bash -c 'grep "^root:" /etc/passwd | cut -f4 -d:' 2>&1); printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- 0 || { echo step1: missing 0; return 1; }; }; if alt0; then echo compliant; fi

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Run the following command to set the root user default group to GID 0 : # usermod -g 0 root

Properties

Operating systems: Any
Tags: container-optimized-oscos
Reference: CIS Google Container-Optimized OS Benchmark v1.2.0 - 5.3.3 Ensure default group for the root account is GID 0

Check this host

Run this on a machine you are allowed to audit. The scan is read-only.

shell

tmaegis scan --target cos