Re: PSA for LUKS users

[Vagrant Cascadian]

On 2023-04-19, Felix Lechner via wrote:
> Given the broad popularity of LUKS full-disk encryption among our
> fellow Guix users, I thought the community might appreciate reading
> about potentially weak key-derivation functions in older LUKS
> installations. [1]
>
> The article even offers fixes, although I cannot say whether your
> system will boot after you follow the steps since I do not use LUKS
> personally. Stay safe!
...
> [1] https://mjg59.dreamwidth.org/66429.html

In short, those instructions will almost certainly break Guix System!

While recent grub2 finally has limited support for luks2, it only
supports the weaker KDF (key derivation function) (PBKDF2?), as I
understand it, though would be happy to be proven wrong!

Because Guix System does not yet support a separate /boot partition,
this means if you want "full-disk encryption" you are limited to weak
KDF for the whole filesystem, instead of just a weak /boot partition
(e.g. either luks1, luks2 with weaker pbkdf2, or entirely
unencrypted). There is a bug about being able to use a split /boot
partition:

  https://issues.guix.gnu.org/48172

Alternately, you could probably get a weaker encrypted rootfs (using
luks1 or luks2+PBKDF) and still have a state-of-the-art luks2+argon2id
partition for /home. Maybe if you were adventurous /var/guix, which
might allow detecting a compromise with "guix gc" which contains the
checksums of files in /gnu/store?

With both the split /boot approach or the weaker rootfs with stronger
/home partition, there is some risk of a (admittedly very sophisticated
and still probably quite expensive) evil maid attack.

  https://en.wikipedia.org/wiki/Evil_maid_attack


Well... fun times, folks!


live well,
  vagrant

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