Opened 3 years ago

Closed 3 years ago

#22638 closed Bug (fixed)

Form wizard may raise unreasonable exceptions in case of SECRET_KEY change

Reported by: Erik Romijn Owned by: Erik Romijn
Component: contrib.formtools Version: 1.6
Severity: Normal Keywords:
Cc: denis.cornehl@… Triage Stage: Ready for checkin
Has patch: yes Needs documentation: no
Needs tests: no Patch needs improvement: no
Easy pickings: no UI/UX: no

Description

Our form wizard has two storage options: sessions and cookies, with SessionWizardView and CookieWizardView. To prevent manipulation, the cookies storage uses the signed cookies from django.core.signing. This creates a signature based on the SECRET_KEY. If the secret key is changed, request.get_signed_cookie will raise an exception, in which case the storage will raise WizardViewCookieModified, a subclass of SuspiciousOperation.

The cookie is loaded very early in the rendering of a the form wizard view. This means that if a user starts a form wizard, and the secret key is changed, any requests to the wizard will result in an exception and likely a 500 error. The user can only recover from this by deleting the cookie or restarting the browser (it seems to only persist in the current session).

It may appear sensible to raise a SuspiciousOperation for a possible cookie manipulation, but we currently don't do this in any other place, like sessions. Currently, user may suddenly get 500 errors for no clear reason, and the developer of the project has no ability to help them. Leaving this as is may also discourage people from rotating their secret key when needed.

I suggest that in case of an invalid wizard cookie, we simply ignore the value and thereby return the user to the first step.

Change History (11)

comment:1 Changed 3 years ago by Tim Graham

Triage Stage: UnreviewedAccepted

comment:2 Changed 3 years ago by nott

WizardViewCookieModified, a subclass of SuspiciousOperation, is raised in this situation since 1.6

comment:3 Changed 3 years ago by nott

Owner: changed from nobody to nott
Status: newassigned

comment:4 Changed 3 years ago by Erik Romijn

Has patch: set

Apologies, forgot to assign this to myself before working on it. Wrote a PR on https://github.com/django/django/pull/2673

comment:5 Changed 3 years ago by Erik Romijn

Owner: nott deleted
Status: assignednew

comment:6 Changed 3 years ago by Denis Cornehl

tested the behavior with a test-application, looks fine to me.

comment:7 Changed 3 years ago by Denis Cornehl

Cc: denis.cornehl@… added
Patch needs improvement: set

comment:8 Changed 3 years ago by Erik Romijn

Patch needs improvement: unset

comment:9 Changed 3 years ago by Claude Paroz

Triage Stage: AcceptedReady for checkin

comment:10 Changed 3 years ago by Erik Romijn

Owner: set to Erik Romijn
Status: newassigned

comment:11 Changed 3 years ago by Erik Romijn <eromijn@…>

Resolution: fixed
Status: assignedclosed

In ba5ddf7aed542d25f0fdb25a04d87305de0f3972:

Fixed #22638 -- Changed CookieWizardView to ignore invalid cookies

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