Ensure authentication required for single user mode

MediumLevel 1Automatedcos

Description

Single user mode (rescue mode) is used for recovery when the system detects an issue during boot or by manual selection from the bootloader. Requiring authentication in single user mode (rescue mode) prevents an unauthorized user from rebooting the system into single user to gain root privileges without credentials.

How it is checked

Audit method: Shell command

shell

alt0() { command -v grep >/dev/null 2>&1 || { echo "step1: grep not installed"; return 1; }; o=$(bash -c 'grep /systemd-sulogin-shell /usr/lib/systemd/system/rescue.service' 2>&1); printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- 'ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue' || { echo step1: missing 'ExecStart=-/usr/lib/systemd/systemd-sulogin-shell rescue'; return 1; }; command -v grep >/dev/null 2>&1 || { echo "step2: grep not installed"; return 1; }; o=$(bash -c 'grep /systemd-sulogin-shell /usr/lib/systemd/system/emergency.service' 2>&1); printf '%s\n' "$o" | tr -s ' \t' '  ' | sed 's/^ //;s/ $//' | grep -Fxq -- 'ExecStart=-/usr/lib/systemd/systemd-sulogin-shell emergency' || { echo step2: missing 'ExecStart=-/usr/lib/systemd/systemd-sulogin-shell emergency'; return 1; }; }; if alt0; then echo compliant; fi

Expected output: compliant

How it is fixed

Fix method: Guidance or infrastructure patch

Rootfs is read-only file system. Therefore, update to an OS image which requires single user mode authentication.

Properties

Operating systems: Any
Tags: authcontainer-optimized-oscos
Reference: CIS Google Container-Optimized OS Benchmark v1.2.0 - 1.3.1 Ensure authentication required for single user mode

Check this host

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

shell

tmaegis scan --target cos