[dm-crypt] Can I test for LUKS passphrase strength without formatting a device?

Milan Broz gmazyland at gmail.com
Tue Nov 7 19:45:46 CET 2017


On 11/07/2017 05:51 PM, Jan Tulak wrote:
> Is it possible to test whether a passphrase is strong enough (and
> luksFormat will accept it), without the need to really create a device
> with this passphrase? I ask because I want to test the password before
> I run a sequence of commands and I don't want them to fail in the
> middle just because of a weak passphrase.

Cryptsetup/LUKS does not itself enforce any passphrase quality, it is libpwquality
that libcryptsetup can be linked to (optionally, we use it in all Red Hat distros).

See man for pwquality library (the idea is to enforce password policy for the whole
distro, so it uses configuration pwquality file).

> I checked for the --test-passphrase, but that verifies if the
> passphrase would decrypt an existing device, which is not what I want.

This tests only LUKS, pwquality is called only in Format.

m.


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