Current logic unconditionally adds public adressing to "cc"
and follower adressing to "to" after attempting to strip it
from the other one. This creates serious problems:
First the bug prompting this investigation and fix,
unconditional addition creates duplicates when adressing
URIs already were in their intended final field; e.g.
this is prominently the case for all "unlisted" posts.
Since List.delete only removes the first occurence,
this then broke follower-adress stripping later on
making the policy ineffective.
It’s also just not safe in general wrt to non-public adressing:
e.g. pre-existing duplicates didn’t get fully stripped,
bespoke adressing modes with only one of public addressing
or follower addressing are mangled — and most importantly:
any belatedly received DM or follower-only post
also got public adressing added!
Shockingly this last point was actually asserted as "correct" in tests;
it appears to be a mistake from mindless match adjustments
while fixing crashes on nil adressing in
10c792110e.
Clean up this sloppy logic up, making sure no more duplicates are
added by us, all instances of relevant adresses are purged and only
readded when they actually existed to begin with.
Current AP spec demands anonymous objects to have an id value,
but explicitly set it to JSON null. Howeveras it turns out this is
incompatible with JSON-LD requiring `@id` to be a string and thus AP
spec is incompatible iwth the Ativity Streams spec it is based on.
This is an issue for (the few) AP implementers actually performing
JSON-LD processing, like IceShrimp.NET.
This was uncovered by IceShrimp.NET’s zotan due to our adoption of
anonymous objects for emoj in f101886709.
The issues is being discussed by W3C, and will most likely be resolved
via an errata redefining anonymous objects to completely omit the id
field just like transient objects already do. See:
https://github.com/w3c/activitypub/issues/476
Fixes: https://akkoma.dev/AkkomaGang/akkoma/issues/848
Currently `mix test` prints a slew of logs in the terminal
with messages from different tests intermsparsed. Globally
enabling capture log hides log messages unless a test fails
reducing noise and making it easier to anylse the important
(from failed tests) messages.
Compiler warnings and a few messages not printed via Logger
still show up but its much more readable than before.
Ported from: 3aed111a42
Usually an id should point to another AP object
and the image file isn’t an AP object. We currently
do not provide standalone AP objects for emoji and
don't keep track of remote emoji at all.
Thus just federate them as anonymous objects,
i.e. objects only existing within a parent context
and using an explicit null id.
IceShrimp.NET previously adopted anonymous objects
for remote emoji without any apparent issues. See:
333611f65e
Fixes: https://akkoma.dev/AkkomaGang/akkoma/issues/694
Trying to display non-media as media crashed the renderer,
but when posting a status with a valid, non-media object id
the post was still created, but then crashed e.g. timeline rendering.
It also crashed C2S inbox reads, so this could not be used to leak
private posts.
In Mastodon media can only be used by owners and only be associated with
a single post. We currently allow media to be associated with several
posts and until now did not limit their usage in posts to media owners.
However, media update and GET lookup was already limited to owners.
(In accordance with allowing media reuse, we also still allow GET
lookups of media already used in a post unlike Mastodon)
Allowing reuse isn’t problematic per se, but allowing use by non-owners
can be problematic if media ids of private-scoped posts can be guessed
since creating a new post with this media id will reveal the uploaded
file content and alt text.
Given media ids are currently just part of a sequentieal series shared
with some other objects, guessing media ids is with some persistence
indeed feasible.
E.g. sampline some public media ids from a real-world
instance with 112 total and 61 monthly-active users:
17.465.096 at t0
17.472.673 at t1 = t0 + 4h
17.473.248 at t2 = t1 + 20min
This gives about 30 new ids per minute of which most won't be
local media but remote and local posts, poll answers etc.
Assuming the default ratelimit of 15 post actions per 10s, scraping all
media for the 4h interval takes about 84 minutes and scraping the 20min
range mere 6.3 minutes. (Until the preceding commit, post updates were
not rate limited at all, allowing even faster scraping.)
If an attacker can infer (e.g. via reply to a follower-only post not
accessbile to the attacker) some sensitive information was uploaded
during a specific time interval and has some pointers regarding the
nature of the information, identifying the specific upload out of all
scraped media for this timerange is not impossible.
Thus restrict media usage to owners.
Checking ownership just in ActivitDraft would already be sufficient,
since when a scheduled status actually gets posted it goes through
ActivityDraft again, but would erroneously return a success status
when scheduling an illegal post.
Independently discovered and fixed by mint in Pleroma
1afde067b1
In MastoAPI media descriptions are updated via the
media update API not upon post creation or post update.
This functionality was originally added about 6 years ago in
ba93396649 which was part of
https://git.pleroma.social/pleroma/pleroma/-/merge_requests/626 and
https://git.pleroma.social/pleroma/pleroma-fe/-/merge_requests/450.
They introduced image descriptions to the front- and backend,
but predate adoption of Mastodon API.
For a while adding an `descriptions` array on post creation might have
continued to work as an undocumented Pleroma extension to Masto API, but
at latest when OpenAPI specs were added for those endpoints four years
ago in 7803a85d2c, these codepaths ceased
to be used. The API specs don’t list a `descriptions` parameter and
any unknown parameters are stripped out.
The attachments_from_ids function is only called from
ScheduledActivity and ActivityDraft.create with the latter
only being called by CommonAPI.{post,update} whihc in turn
are only called from ScheduledActivity again, MastoAPI controller
and without any attachment or description parameter WelcomeMessage.
Therefore no codepath can contain a descriptions parameter.
