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Re: Grub2 Security

From: Joāo Ricardo Sares Teles de Matos
Subject: Re: Grub2 Security
Date: Sat, 30 May 2015 01:05:28 +0100
User-agent: K-9 Mail for Android

It's right here:
Set a superuser that can't actually be used and use --unrestricted on the entries.

How to set up an "unauthenticatable" superuser is my question.
Maybe setting an invalid password hash with password_pbkdf2 or just not setting the user's password will suffice.

On May 29, 2015 10:28:17 PM GMT+01:00, "Boyce, Kevin P. (AS)" <address@hidden> wrote:

I am hoping someone can help me with a grub2 configuration question. I
would like to be able to secure grub menu entries from being modified.
I do not want to have to enter a password to boot the system (which
doesn't appear to be the current behavior of grub2 when set
superusers="root" directive is used).
I do not want to have to create users and associated passwords (null
password is OK).

I would like everyone to be able to select either one of these two boot
entries without the need for a password, but i do not want them to be
able to enter command mode or edit mode in which they could boot single
user mode (my Rescue enviroment is being customized for recovery purposes).

My bootloader and configuration will be permanently installed in a
read-only device like ROM and never changed. I use the configfile
directive to point to the real bootloader configu ration on a different
device I want to use.

Here is my current config file, documentation on grub2 security seems a
little lacking. I recall being able to achieve this behavior by using
the lock directive in legacy-grub.
Any help would be appreciated.


# Load GPT Partition Support
insmod part_gpt

# Load XFS File System Support
insmod xfs

# Load EXT File System Support
insmod ext2

# Set a timeout before we pick the default
set timeout=7

# Set the default boot entry
set default="0"
set fallback="1"

# Don't want any accounts that can bypass either one of these two entries
set superusers=""

# Default boot entry redirecting to config file on RAID
# Secure without granting users permission to modify
menuentry "Redirect Boot to RAID Device" --users "" {
search --no-floppy --set=root --label RAID configfile /.firmware/boot.cfg

# Create an entry for loading troubleshooting environment
# Secure without granting users permission to modify this entry
menuentry "Rescue" --users "" {
search --no-floppy --set=root --label RESCUE
linux /vmlinuz rescue
initrd /initrd.img

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