Red Hat Enterprise Linux operating systems version 7.2 or newer booted with United Extensible Firmware Interface (UEFI) must have a unique name for the grub superusers account when booting into single-user mode and maintenance.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-244558	RHEL-07-010492	SV-244558r833187_rule		Medium

Description
If the system does not require valid authentication before it boots into single-user or maintenance mode, anyone who invokes single-user or maintenance mode is granted privileged access to all files on the system. GRUB 2 is the default boot loader for RHEL 7 and is designed to require a password to boot into single-user mode or make modifications to the boot menu. The GRUB 2 superuser account is an account of last resort. Establishing a unique username for this account hardens the boot loader against brute force attacks. Due to the nature of the superuser account database being distinct from the OS account database, this allows the use of a username that is not among those within the OS account database. Examples of non-unique superusers names are root, superuser, unlock, etc.

Description

If the system does not require valid authentication before it boots into single-user or maintenance mode, anyone who invokes single-user or maintenance mode is granted privileged access to all files on the system. GRUB 2 is the default boot loader for RHEL 7 and is designed to require a password to boot into single-user mode or make modifications to the boot menu. The GRUB 2 superuser account is an account of last resort. Establishing a unique username for this account hardens the boot loader against brute force attacks. Due to the nature of the superuser account database being distinct from the OS account database, this allows the use of a username that is not among those within the OS account database. Examples of non-unique superusers names are root, superuser, unlock, etc.

STIG	Date
Red Hat Enterprise Linux 7 Security Technical Implementation Guide	2022-12-06

Details

Check Text ( C-47833r792839_chk )
For systems that use BIOS, this is Not Applicable. For systems that are running a version of RHEL prior to 7.2, this is Not Applicable. Verify that a unique name is set as the "superusers" account: $ sudo grep -iw "superusers" /boot/efi/EFI/redhat/grub.cfg set superusers="[someuniquestringhere]" export superusers If "superusers" is identical to any OS account name or is missing a name, this is a finding.

Check Text ( C-47833r792839_chk )

For systems that use BIOS, this is Not Applicable.

For systems that are running a version of RHEL prior to 7.2, this is Not Applicable.

Verify that a unique name is set as the "superusers" account:

$ sudo grep -iw "superusers" /boot/efi/EFI/redhat/grub.cfg
set superusers="[someuniquestringhere]"
export superusers

If "superusers" is identical to any OS account name or is missing a name, this is a finding.

Fix Text (F-47790r833186_fix)
Configure the system to have a unique name for the grub superusers account. Edit the /etc/grub.d/01_users file and add or modify the following lines: set superusers="[someuniquestringhere]" export superusers password_pbkdf2 [someuniquestringhere] ${GRUB2_PASSWORD} Generate a new grub.cfg file with the following command: $ sudo grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg