#24496: Check CSRF Referer against CSRF_TRUSTED_ORIGINS
------------------------------+------------------------------------
Reporter: mattrobenolt | Owner: joshkehn
Type: New feature | Status: assigned
Component: CSRF | Version: master
Severity: Normal | Resolution:
Keywords: csrf | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by carljm):
Replying to [comment:21 joshkehn]:
> Right, my question was with `CSRF_TRUSTED_ORIGINS` explicitly set
wouldn't someone reasonably assume that it's a filter on top of
`CSRF_COOKIE_DOMAIN`?
>
> Example: Set `CSRF_COOKIE_DOMAIN` to `.example.com` for convenience of
configuration so that the cookie is shared among any subdomain. Set
`CSRF_TRUSTED_ORIGINS` to only allow certain referers to pass the CSRF
checks.
>
> My suggestion would be to only use `CSRF_COOKIE_DOMAIN` if
`CSRF_TRUSTED_ORIGINS` is empty and make that a separate branch of logic.
It's a reasonable point, but I don't think so. Any host you are willing to
share the CSRF cookie with is implicitly trusted to make use of it.
Sharing the cookie is actually already a much deeper level of trust than
that provided by CSRF_TRUSTED_ORIGINS alone, because it allows that host
to get past both parts of the CSRF check, referrer and token.
CSRF_TRUSTED_ORIGINS is a technique for adding _additional_ hosts who can
bypass the referrer check, it's not a mechanism for restriction.
With your proposed behavior, it would be impossible to both have many
wildcarded subdomains AND an external CORS-using host. That would be
pretty frustrating.
Certainly the interaction of the two settings should be documented
clearly.
> Carl, I'm not sure if there's an easy way to split out into a new
ticket. Do you have one? If not, I can manually do it a bit later today.
No, there's no secret technique for that. Shouldn't be too hard; I
wouldn't try to copy all the comments or anything. Just open a new ticket
and say "some previous discussion in #24496", and re-title your pull
request so it gets linked up with the new ticket.
--
Ticket URL: <https://code.djangoproject.com/ticket/24496#comment:22>
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