cis-ubuntu1804-v220-1-4-1

name	cis-ubuntu1804-v220-1-4-1
description	Ensure bootloader password is set
category	cis-storage
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","grub","bootloader","password","secure-boot"]
cis_id	1.4.1
cis_benchmark	CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

1.4.1 Ensure bootloader password is set (Automated)

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

Setting the boot loader password will require that anyone rebooting the system must enter a password before being able to set command line boot parameters.

Rationale

Requiring a boot password upon execution of the boot loader will prevent an unauthorized user from entering boot parameters or changing the boot partition. This prevents users from weakening security (e.g. turning off AppArmor at boot time).

Impact

If password protection is enabled, only the designated superuser can edit a GRUB 2 menu item by pressing "e" or access the GRUB 2 command line by pressing "c".

If GRUB 2 is set up to boot automatically to a password-protected menu entry the user has no option to back out of the password prompt to select another menu entry. Holding the SHIFT key will not display the menu in this case. The user must enter the correct username and password. If unable to do so, the configuration files will have to be edited via a LiveCD or other means to fix the problem.

You can add --unrestricted to the menu entries to allow the system to boot without entering a password. A password will still be required to edit menu items.

Audit Procedure

Command Line

Run the following commands and verify output matches:

grep "^set superusers" /boot/grub/grub.cfg

grep "^password" /boot/grub/grub.cfg

Expected Result

set superusers="<username>"
password_pbkdf2 <username> <encrypted-password>

Remediation

Command Line

Create an encrypted password with grub-mkpasswd-pbkdf2:

grub-mkpasswd-pbkdf2

Add the following into a custom /etc/grub.d configuration file:

cat <<EOF
set superusers="<username>"
password_pbkdf2 <username> <encrypted-password>
EOF

The superuser/user information and password should not be contained in the /etc/grub.d/00_header file as this file could be overwritten in a package update. If there is a requirement to be able to boot/reboot without entering the password, edit /etc/grub.d/10_linux and add --unrestricted to the line CLASS=.

Example: