Tweak fetch security checks #819

Merged
floatingghost merged 2 commits from Oneric/akkoma:id-refetch into develop 2024-10-16 14:16:15 +00:00

2 commits

Author SHA1 Message Date
d5b0720596 Allow cross-domain redirects on AP requests
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Since we now remember the final location redirects lead to
and use it for all further checks since
3e134b07fa, these redirects
can no longer be exploited to serve counterfeit objects.

This fixes:
 - display URLs from independent webapp clients
   redirecting to the canonical domain
 - Peertube display URLs for remote content
   (acting like the above)
2024-10-14 01:42:51 +02:00
940792f8ba Refetch on AP ID mismatch
As hinted at in the commit message when strict checking
was added in 8684964c5d,
refetching is more robust than display URL comparison
but in exchange is harder to implement correctly.

A similar refetch approach is also employed by
e.g. Mastodon, IceShrimp and FireFish.

To make sure no checks can be bypassed by forcing
a refetch, id checking is placed at the very end.

This will fix:
 - Peertube display URL arrays our transmogrifier fails to normalise
 - non-canonical display URLs from alternative frontends
   (theoretical; we didnt’t get any actual reports about this)

It will also be helpful in the planned key handling overhaul.

The modified user collision test was introduced in
https://git.pleroma.social/pleroma/pleroma/-/merge_requests/461
and unfortunately the issues this fixes aren’t public.
Afaict it was just meant to guard against someone serving
faked data belonging to an unrelated domain. Since we now
refetch and the id actually is mocked, lookup now succeeds
but will use the real data from the authorative server
making it unproblematic. Instead modify the fake data further
and make sure we don’t end up using the spoofed version.
2024-10-14 01:42:43 +02:00