id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
37375	`ScryptPasswordHasher` cannot verify hashes with non-default derived key lengths	Dominic Roy		"`ScryptPasswordHasher` currently hardcodes `dklen=64` when calling
`hashlib.scrypt()`.

As a result, Django cannot verify otherwise valid scrypt password hashes
generated by another implementation when that implementation uses a larger
derived key length.

This came up while working on password hash compatibility in authentik
(https://goauthentik.io), where imported scrypt hashes may come from systems
using different `dklen` values.

Django should probably keep 64 bytes as the minimum accepted derived key
length rather than accepting arbitrary shorter hashes. However, hashes with a
larger `dklen`, for example 128 bytes, currently fail verification because
`verify()` always regenerates a 64-byte result.

The derived key length can be recovered from the length of the Base64-decoded
digest. `verify()` could use that value when it is at least 64, while Django
continues generating new hashes with `dklen=64`.

If appropriate under Django's backport policy, it would also be useful to
include this in Django 5.2 LTS.

I'm happy to submit a patch with tests if this approach is accepted."	Bug	new	contrib.auth	5.2	Normal		scrypt password hasher dklen	Dominic Roy	Unreviewed	0	0	0	0	0	0