Re: Grub2 Security

[Joāo Ricardo Sares Teles de Matos]

On second thought...
"If ‘superusers’ is set, then use of the command line is automatically restricted to superusers."

Setting an empty superusers list and adding --unresticted to your entries is probably what you want.

On May 30, 2015 1:05:28 AM GMT+01:00, "Joāo Ricardo Sares Teles de Matos" <address@hidden> wrote:

It's right here: https://www.gnu.org/software/grub/manual/grub.html#Security
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:

All,

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.

Thanks,
Kevin

# 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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