The Red Hat Enterprise Linux operating system must not allow removable media to be used as the boot loader unless approved.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-204501	RHEL-07-021700	SV-204501r928576_rule		Medium

Description
Malicious users with removable boot media can gain access to a system configured to use removable media as the boot loader. If removable media is designed to be used as the boot loader, the requirement must be documented with the information system security officer (ISSO).

STIG	Date
Red Hat Enterprise Linux 7 Security Technical Implementation Guide	2023-09-08

Details

Check Text ( C-4625r928575_chk )
Verify the system is not configured to use a boot loader on removable media. Note: GRUB 2 reads its configuration from the "/boot/grub2/grub.cfg" file on traditional BIOS-based machines and from the "/boot/efi/EFI/redhat/grub.cfg" file on UEFI machines. Check for the existence of alternate boot loader configuration files with the following command: # find / -name grub.cfg /boot/efi/EFI/redhat/grub.cfg If a "grub.cfg" is found in any subdirectories other than "/boot/grub2/" and "/boot/efi/EFI/redhat/", ask the system administrator (SA) if there is documentation signed by the ISSO to approve the use of removable media as a boot loader. List the number of menu entries defined in the grub configuration file with the following command (the number will vary between systems): # grep -cw menuentry /boot/efi/EFI/redhat/grub.cfg 4 Check that the grub configuration file has the "set root" command for each menu entry with the following command ("set root" defines the disk and partition or directory where the kernel and GRUB 2 modules are stored): # grep 'set root' /boot/efi/EFI/redhat/grub.cfg set root='hd0,gpt2' set root='hd0,gpt2' set root='hd0,gpt2' set root='hd0,gpt2' If the system is using an alternate boot loader on removable media, and documentation does not exist approving the alternate configuration, this is a finding.

Check Text ( C-4625r928575_chk )

Verify the system is not configured to use a boot loader on removable media.

Note: GRUB 2 reads its configuration from the "/boot/grub2/grub.cfg" file on traditional BIOS-based machines and from the "/boot/efi/EFI/redhat/grub.cfg" file on UEFI machines.

Check for the existence of alternate boot loader configuration files with the following command:

# find / -name grub.cfg
/boot/efi/EFI/redhat/grub.cfg

If a "grub.cfg" is found in any subdirectories other than "/boot/grub2/" and "/boot/efi/EFI/redhat/", ask the system administrator (SA) if there is documentation signed by the ISSO to approve the use of removable media as a boot loader.

List the number of menu entries defined in the grub configuration file with the following command (the number will vary between systems):

# grep -cw menuentry /boot/efi/EFI/redhat/grub.cfg
4

Check that the grub configuration file has the "set root" command for each menu entry with the following command ("set root" defines the disk and partition or directory where the kernel and GRUB 2 modules are stored):

# grep 'set root' /boot/efi/EFI/redhat/grub.cfg
set root='hd0,gpt2'
set root='hd0,gpt2'
set root='hd0,gpt2'
set root='hd0,gpt2'

If the system is using an alternate boot loader on removable media, and documentation does not exist approving the alternate configuration, this is a finding.

Fix Text (F-4625r88696_fix)
Remove alternate methods of booting the system from removable media or document the configuration to boot from removable media with the ISSO.