OpenBSD Full Disk Encryption with CoreBoot and Tianocore Payload

It has been a while since I have posted here so I wanted to share something that was surprisingly difficult for me to figure out.  I have a Thinkpad T440p that I have flashed with Coreboot 4.11 with some special patches that allow the newer machine to work.  When I got the laptop, the default BIOS was UEFI and I installed two operating systems.

  • Windows 10 with bitlocker full disk encryption on the “normal” drive (I replaced the spinning 2.5″ disk with an SSD)
  • Ubuntu 19.10 on the m.2 SATA drive that I installed using LUKS full disk encryption

I purchased one of those carriers for the optical bay that allows you to install a third SSD and so I did that with the intent of putting OpenBSD on it.  Since my other two operating systems were running full disk encryption, I wanted to do the same on OpenBSD.

Turns out that with a UEFI install, it is surprisingly hard.  My first attempts failed miserably.  Then, I had some inspiration.  I decided to install OpenBSD with no encryption and see if I could get things working with booting that from the Grub2 menu in Linux (where I also had an entry for Windows 10).  If I could do that, I figured I could go back and drop the non EFI partition and replace it with a softraid encrypted partition.

I installed OpenBSD “straight up” and was able to boot the disk from the boot menu in Tianocoare’s implementation of UEFI.  The trick was now to figure out what entry I had to make in Grub2 under Ubuntu to get things working.  I shot in the dark based on one web search after another and got no joy.  I decided to sleep on it.

When I attempted again, I remembered that you could hit the “c” key from the Grub2 boot menu and get an interactive Grub2 command prompt.  From here, I used the ls command to find the Grub2 name of my OpenBSD EFI partition that was created by the installer.  In my case, it turned out to be (hd2,gpt2).  I did an ls like this:

ls (hd2,gpt2)/

and was able to see the efi subdirectory (note the trailing slash!) and then could use ls to further explore and find the /efi/boot/ directory that contained the bootx64.efi bootloader file.

OK.  Now how can I get Grub2 to boot that.  Turns out there is a module you have to load called “part_msdos” (because the EFI partition is an msdos partition secretly).  I tried issuing the insmod part_msdos command (which was successful) and then used:

chainloader (hd2,gpt2)/efi/boot/bootx64.efi

Then I issued the “boot” command and I booted into my unencrypted OpenBSD partition.

Now that I had this, it was a simple matter to edit the 40_custom file in /etc/grub.d on the Ubuntu 19.10 system to create a special entry for OpenBSD:

menuentry “OpenBSD” (on /dev/sdc2) $menuentry_id_option ‘openbsd’ {
insmod part_msdos
chainloader (hd2,gpt2)/efi/boot/bootx64.efi
}

With that, I was able to boot from the Grub2 boot menu into my unencrypted OpenBSD partition!  w00t indeed!!

Now, to make it an encrypted partition.  I booted up from my USB install media for OpenBSD, dropped to a shell, and used fdisk in interactive mode to delete all of the non swap OpenBSD partitions from the disk – don’t delete the EFI partition!!!!!  After that, I created on single “a” partition and made it’s filesystem type “RAID”.  From there, I issued the bioctl command to turn that partition into a softraid encrypted partition:

bioctl -c C -l /dev/sd2a softraid0

I provided my password to decrypt the partition twice and voila, I had an sd4 encrypted disk.  I went back into the installer with the ‘exit’ command and installed OpenBSD as normal on the new sd4 encrypted partition that was visible.

Now for the acid test.  Without changing anything in Grub2, I rebooted and selected my “OpenBSD” menu entry.  Drumroll… Yep.  Everything worked!  I now have a Thinkpad T440p (hotrodded with a T450 touchpad, a 1080p IPS panel, 16 GB of RAM and an i7 4712MQ processor) running Coreboot instead of the stock BIOS with three SSDs, all encrypted with a nice menu to choose between OpenBSD 6.6, Ubuntu 19.10 and Windows 10 – all with full disk encryption!

By the way, if you are thinking about Corebooting a Thinkpad T440p, remember two things:

  1. You can’t use the stock 4.11 codebase, you need to add the special patches from “Archfan”.
  2. The OctoPerf site has a great breakdown of what you can upgrade with links to the magic necessary to get Windows 10 to allow you to install (and keep!) the driver for the Thinkpad T450 trackpad that replaces the horrific “clunkpad” that came with the T440p.

Happy Corebooting!

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