Vulnerability Discussion

If the system does not require valid root 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.

Check

For systems that use UEFI, this is Not Applicable.

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

Check to see if an encrypted root password is set. On systems that use a BIOS, use the following command:

# grep -iw grub2_password /boot/grub2/user.cfg
GRUB2_PASSWORD=grub.pbkdf2.sha512.[password_hash]

If the root password does not begin with "grub.pbkdf2.sha512", this is a finding.

Verify that the "root" account is set as the "superusers":

# grep -iw "superusers" /boot/grub2/grub.cfg
set superusers="root"
export superusers

If "superusers" is not set to "root", this is a finding.

Fix

Configure the system to encrypt the boot password for root.

Generate an encrypted grub2 password for root with the following command:

Note: The hash generated is an example.

# grub2-setpassword
Enter password:
Confirm password:

Edit the /boot/grub2/grub.cfg file and add or modify the following lines in the "### BEGIN /etc/grub.d/01_users ###" section:

set superusers="root"
export superusers