cis-ubuntu1604-v200-1-4-2

name	cis-ubuntu1604-v200-1-4-2
description	Ensure bootloader password is set
category	cis-iam
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","bootloader","grub","password","secure-boot"]
cis_id	1.4.2
cis_benchmark	CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - 1.4.2

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, the configuration files will have to be edited via the 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. Password will still be required to edit menu items.

More Information: https://help.ubuntu.com/community/Grub2/Passwords

Audit Procedure

Command Line

Run the following commands and verify output matches:

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

Expected output: set superusers="<username>"

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

Expected output: password_pbkdf2 <username> <encrypted-password>

Expected Result

The set superusers and password_pbkdf2 lines should be present in /boot/grub/grub.cfg.

Remediation

Command Line

Create an encrypted password with grub-mkpasswd-pbkdf2:

grub-mkpasswd-pbkdf2

Enter password: <password>
Reenter password: <password>
PBKDF2 hash of your password is <encrypted-password>

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