this post was submitted on 05 Sep 2024
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[Question] Encrypted Partition Unlock via Root Unlocking (programming.dev)
submitted 2 months ago by recursive_recursion@programming.dev to c/linux@programming.dev
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cross-posted from: https://programming.dev/post/19007507

For context:
I've encrypted the swap partition with:

cryptsetup -v luksFormat /dev/${DEVICE}
cryptsetup luksOpen /dev/${DEVICE} swap

And what I want is for the user to be able to enter their password only once to decrypt their root partition which would contain a keyfile to then decrypt their swap partition.

Does anyone know if this is possible?
Just thought I'd ask to see if anyone's done this already

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[–] haroldstork@lemm.ee 4 points 2 months ago (1 children)

Yes, very. I've seen people do a similar thing with a separate encrypted home partition which is decrypted by a key stored in your encrypted root. However, I'd strongly recommend you use an LVM on LUKS setup (this is what I do). That way you decrypt one partition and you don't have to mess around with keyfiles. https://wiki.archlinux.org/title/Dm-crypt/Encrypting_an_entire_system#LVM_on_LUKS

[–] recursive_recursion@programming.dev 2 points 2 months ago (1 children)

I’ve seen people do a similar thing with a separate encrypted home partition which is decrypted by a key stored in your encrypted root.

Do you happen to have a link to this?

However, I’d strongly recommend you use an LVM on LUKS setup (this is what I do). That way you decrypt one partition and you don’t have to mess around with keyfiles. #LVM_on_LUKS

Looking at the wiki it seems doable (in relation to revising my script) and as far as I can tell the tradeoffs seems better than #LUKS on a partition

much appreciated for the recommendation!

[–] Ooops 1 points 2 months ago* (last edited 2 months ago)

There is a difference here.

Unlocking home later in the boot process is not a problem, so the you can indeed have a keyfile on your root and get your home unlocked and mounted after root is done.

Swap however needs to be available early, at least if you want to use it for hibernation.