#31842: django.core.signing.dumps() and loads() not backwards compatible
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Reporter: Markus Holtermann | Owner: nobody
Type: Bug | Status: new
Component: Core (Other) | Version: 3.1
Severity: Release blocker | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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In Django 3.1, the default algorithm for `django.core.signing.Signer` was
changed from sha1 to sha256. That's good!
However, the `django.core.signing.dumps()` and
`django.core.signing.loads()` functions don't expose the algorithm. I
think, that that makes an upgrade from 3.0 to 3.1 impossible when one uses
the `dumps()` function in a multi-node Django setup.
Let's say there are two servers. Both run an application with Django 3.0.
and make use of `dumps()` and `loads()`. Then server 1 is upgraded to use
Django 3.1. At this point, because of to the backwards compatibility parts
in the decoding/signature validation, a token signed by server 2 can be
loaded on server 1 and 2. However, a token signed by server 1 cannot be
loaded on server 2.
This problem could be mitigated by exposing the algorithm in the `dumps()`
method and setting it to `sha1`. Once all servers run Django 3.1, the
algorithm could be changed to `sha256`.
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Ticket URL: <https://code.djangoproject.com/ticket/31842>
Django <https://code.djangoproject.com/>
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