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.
This protects us from falling for obvious spoofs as from the current
upload exploit (unfortunately we can’t reasonably do anything about
spoofs with exact matches as was possible via emoji and proxy).
Such objects being invalid is supported by the spec, sepcifically
sections 3.1 and 3.2: https://www.w3.org/TR/activitypub/#obj-id
Anonymous objects are not relevant here (they can only exists within
parent objects iiuc) and neither is client-to-server or transient objects
(as those cannot be fetched in the first place).
This leaves us with the requirement for `id` to (a) exist and
(b) be a publicly dereferencable URI from the originating server.
This alone does not yet demand strict equivalence, but the spec then
further explains objects ought to be fetchable _via their ID_.
Meaning an object not retrievable via its ID, is invalid.
This reading is supported by the fact, e.g. GoToSocial (recently) and
Mastodon (for 6+ years) do already implement such strict ID checks,
additionally proving this doesn’t cause federation issues in practice.
However, apart from canonical IDs there can also be additional display
URLs. *omas first redirect those to their canonical location, but *keys
and Mastodon directly serve the AP representation without redirects.
Mastodon and GTS deal with this in two different ways,
but both constitute an effective countermeasure:
- Mastodon:
Unless it already is a known AP id, two fetches occur.
The first fetch just reads the `id` property and then refetches from
the id. The last fetch requires the returned id to exactly match the
URL the content was fetched from. (This can be optimised by skipping
the second fetch if it already matches)
05eda8d193/app/helpers/jsonld_helper.rb (L168)63f0979799
- GTS:
Only does a single fetch and then checks if _either_ the id
_or_ url property (which can be an object) match the original fetch
URL. This relies on implementations always including their display URL
as "url" if differing from the id. For actors this is true for all
investigated implementations, for posts only Mastodon includes an
"url", but it is also the only one with a differing display URL.
2bafd7daf5 (diff-943bbb02c8ac74ac5dc5d20807e561dcdfaebdc3b62b10730f643a20ac23c24fR222)
Albeit Mastodon’s refetch offers higher compatibility with theoretical
implmentations using either multiple different display URL or not
denoting any of them as "url" at all, for now we chose to adopt a
GTS-like refetch-free approach to avoid additional implementation
concerns wrt to whether redirects should be allowed when fetching a
canonical AP id and potential for accidentally loosening some checks
(e.g. cross-domain refetches) for one of the fetches.
This may be reconsidered in the future.
If it’s not already in the database,
it must be counterfeit (or just not exists at all)
Changed test URLs were only ever used from "local: false" users anyway.
OTP builds to 1.15
Changelog entry
Ensure policies are fully loaded
Fix :warn
use main branch for linkify
Fix warn in tests
Migrations for phoenix 1.17
Revert "Migrations for phoenix 1.17"
This reverts commit 6a3b2f15b7.
Oban upgrade
Add default empty whitelist
mix format
limit test to amd64
OTP 26 tests for 1.15
use OTP_VERSION tag
baka
just 1.15
Massive deps update
Update locale, deps
Mix format
shell????
multiline???
?
max cases 1
use assert_recieve
don't put_env in async tests
don't async conn/fs tests
mix format
FIx some uploader issues
Fix tests
`context` fields for objects and activities can now be generated based
on the object/activity `inReplyTo` field or its ActivityPub ID, as a
fallback method in cases where `context` fields are missing for incoming
activities and objects.
This fixes a race condition bug where keys could be regenerated
post-federation, causing activities and HTTP signatures from an user to
be dropped due to key differences.
Use Websockex to replace websocket_client
Test that server will disconnect websocket upon token revocation
Lint
Execute session disconnect in background
Refactor streamer test
allow multi-streams
rebase websocket change
Incoming Pleroma replies to a Misskey thread were rejected due to a
broken context fix, which caused them to not be visible until a
non-Pleroma user interacted with the replies.
This fix properly sets the post-fix object context to its parent Create
activity as well, if it was changed.
