Commit graph

15467 commits

Author SHA1 Message Date
11ae8344eb Sanitise Content-Type of media proxy URLs
Just as with uploads and emoji before, this can otherwise be used
to place counterfeit AP objects or other malicious payloads.
In this case, even if we never assign a priviliged type to content,
the remote server can and until now we just mimcked whatever it told us.

Preview URLs already handle only specific, safe content types
and redirect to the external host for all else; thus no additional
sanitisiation is needed for them.

Non-previews are all delegated to the modified ReverseProxy module.
It already has consolidated logic for building response headers
making it easy to slip in sanitisation.

Although proxy urls are prefixed by a MAC built from a server secret,
attackers can still achieve a perfect id match when they are able to
change the contents of the pointed to URL. After sending an posts
containing an attachment at a controlled destination, the proxy URL can
be read back and inserted into the payload. After injection of
counterfeits in the target server the content can again be changed
to something innocuous lessening chance of detection.
2024-03-18 22:33:10 -01:00
bcc528b2e2 Never automatically assign privileged content types
By mapping all extensions related to our custom privileged types
back to innocuous text/plain, our custom types will never automatically
be inserted which was one of the factors making impersonation possible.

Note, this does not invalidate the upload and emoji Content-Type
restrictions from previous commits. Apart from counterfeit AP objects
there are other payloads with standard types this protects against,
e.g. *.js Javascript payloads as used in prior frontend injections.
2024-03-18 22:33:10 -01:00
e88d0a2853 Fix Content-Type of our schema
Strict servers fail to process anything from us otherwise.

Fixes: akkoma#716
2024-03-18 22:33:10 -01:00
ba558c0c24 Limit instance emoji to image types
Else malicious emoji packs or our EmojiStealer MRF can
put payloads into the same domain as the instance itself.
Sanitising the content type should prevent proper clients
from acting on any potential payload.

Note, this does not affect the default emoji shipped with Akkoma
as they are handled by another plug. However, those are fully trusted
and thus not in needed of sanitisation.
2024-03-18 22:33:10 -01:00
0ec62acb9d Always insert Dedupe upload filter
This actually was already intended before to eradict all future
path-traversal-style exploits and to fix issues with some
characters like akkoma#610 in 0b2ec0ccee. However, Dedupe and
AnonymizeFilename got mixed up. The latter only anonymises the name
in Content-Disposition headers GET parameters (with link_name),
_not_ the upload path.

Even without Dedupe, the upload path is prefixed by an UUID,
so it _should_ already be hard to guess for attackers. But now
we actually can be sure no path shenanigangs occur, uploads
reliably work and save some disk space.

While this makes the final path predictable, this prediction is
not exploitable. Insertion of a back-reference to the upload
itself requires pulling off a successfull preimage attack against
SHA-256, which is deemed infeasible for the foreseeable futures.

Dedupe was already included in the default list in config.exs
since 28cfb2c37a, but this will get overridde by whatever the
config generated by the "pleroma.instance gen" task chose.

Upload+delete tests running in parallel using Dedupe might be flaky, but
this was already true before and needs its own commit to fix eventually.
2024-03-18 22:33:10 -01:00
fef773ca35 Drop media base_url default and recommend different domain
Same-domain setups enabled now at least two exploits,
so they ought to be discouraged and definitely not be the default.
2024-03-18 22:33:10 -01:00
bdefbb8fd9 plug/upload_media: query config only once on init 2024-03-18 22:33:10 -01:00
f7c9793542 Sanitise Content-Type of uploads
The lack thereof enables spoofing ActivityPub objects.

A malicious user could upload fake activities as attachments
and (if having access to remote search) trick local and remote
fedi instances into fetching and processing it as a valid object.

If uploads are hosted on the same domain as the instance itself,
it is possible for anyone with upload access to impersonate(!)
other users of the same instance.
If uploads are exclusively hosted on a different domain, even the most
basic check of domain of the object id and fetch url matching should
prevent impersonation. However, it may still be possible to trick
servers into accepting bogus users on the upload (sub)domain and bogus
notes attributed to such users.
Instances which later migrated to a different domain and have a
permissive redirect rule in place can still be vulnerable.
If — like Akkoma — the fetching server is overly permissive with
redirects, impersonation still works.

This was possible because Plug.Static also uses our custom
MIME type mappings used for actually authentic AP objects.

Provided external storage providers don’t somehow return ActivityStream
Content-Types on their own, instances using those are also safe against
their users being spoofed via uploads.

Akkoma instances using the OnlyMedia upload filter
cannot be exploited as a vector in this way — IF the
fetching server validates the Content-Type of
fetched objects (Akkoma itself does this already).

However, restricting uploads to only multimedia files may be a bit too
heavy-handed. Instead this commit will restrict the returned
Content-Type headers for user uploaded files to a safe subset, falling
back to generic 'application/octet-stream' for anything else.
This will also protect against non-AP payloads as e.g. used in
past frontend code injection attacks.

It’s a slight regression in user comfort, if say PDFs are uploaded,
but this trade-off seems fairly acceptable.

(Note, just excluding our own custom types would offer no protection
 against non-AP payloads and bear a (perhaps small) risk of a silent
 regression should MIME ever decide to add a canonical extension for
 ActivityPub objects)

Now, one might expect there to be other defence mechanisms
besides Content-Type preventing counterfeits from being accepted,
like e.g. validation of the queried URL and AP ID matching.
Inserting a self-reference into our uploads is hard, but unfortunately
*oma does not verify the id in such a way and happily accepts _anything_
from the same domain (without even considering redirects).
E.g. Sharkey (and possibly other *keys) seem to attempt to guard
against this by immediately refetching the object from its ID, but
this is easily circumvented by just uploading two payloads with the
ID of one linking to the other.

Unfortunately *oma is thus _both_ a vector for spoofing and
vulnerable to those spoof payloads, resulting in an easy way
to impersonate our users.

Similar flaws exists for emoji and media proxy.

Subsequent commits will fix this by rigorously sanitising
content types in more areas, hardening our checks, improving
the default config and discouraging insecure config options.
2024-03-18 22:33:10 -01:00
7ef93c0b6d Add set_content_type to Plug.StaticNoCT 2024-03-04 17:50:20 +01:00
dbb6091d01 Import copy of Plug.Static from Plug 1.15.3
The following commit will apply the needed patch
2024-03-04 17:50:20 +01:00
5d467af6c5 Update notes on security exploit handling 2024-03-04 17:50:19 +01:00
889b57df82 2024.02 release 2024-02-24 13:54:21 +00:00
Weblate
34ffb92db4 Update translation files
Updated by "Squash Git commits" hook in Weblate.

Co-authored-by: Weblate <noreply@weblate.org>
Translate-URL: http://translate.akkoma.dev/projects/akkoma/akkoma-backend-posix-errors/
Translation: Pleroma fe/Akkoma Backend (Posix Errors)
2024-02-24 13:42:59 +00:00
Weblate
c6dceb1802 Translated using Weblate (Polish)
Currently translated at 100.0% (47 of 47 strings)

Co-authored-by: Weblate <noreply@weblate.org>
Co-authored-by: subtype <subtype@hollow.capital>
Translate-URL: http://translate.akkoma.dev/projects/akkoma/akkoma-backend-posix-errors/pl/
Translation: Pleroma fe/Akkoma Backend (Posix Errors)
2024-02-24 13:42:59 +00:00
Weblate
caaf2deb22 Translated using Weblate (Polish)
Currently translated at 18.1% (183 of 1006 strings)

Translated using Weblate (Polish)

Currently translated at 6.6% (67 of 1006 strings)

Co-authored-by: Weblate <noreply@weblate.org>
Co-authored-by: subtype <subtype@hollow.capital>
Translate-URL: http://translate.akkoma.dev/projects/akkoma/akkoma-backend-config-descriptions/pl/
Translation: Pleroma fe/Akkoma Backend (Config Descriptions)
2024-02-24 13:42:59 +00:00
7d61fb0906 Merge pull request 'Fix static-fe Twitter metadata / URL previews' (#700) from Oneric/akkoma:staticfe-metadata into develop
Reviewed-on: AkkomaGang/akkoma#700
2024-02-24 13:42:55 +00:00
cdf73e0ac8 Merge pull request 'Better document database differences for Pleroma migrations' (#699) from Oneric/akkoma:doc_pleroma-migration-db into develop
Reviewed-on: AkkomaGang/akkoma#699
2024-02-24 04:33:43 +00:00
967e6b8ade Merge pull request 'Docs: Add description for mrf_reject_newly_created_account_notes' (#695) from YokaiRick/akkoma:doc_mrf_reject_acc_notes into develop
Reviewed-on: AkkomaGang/akkoma#695
2024-02-24 04:31:28 +00:00
bff2812a93 More prominently document db migrations in migrations from Pleroma
By now most instance will run a version past 2022-08 but the guide
only documented it for from source installs and Pleroma develop.
2024-02-23 23:54:14 +01:00
7964272c98 Document how to avoid data loss on migration from Pleroma 2024-02-23 23:54:09 +01:00
c08f49d88e Add tests for static-fe metadata tags 2024-02-21 00:33:32 +00:00
3111181d3c mix format 2024-02-20 15:09:04 +00:00
2f9aad0e65 Merge pull request '[Security] StealEmojiPolicy: Sanitize shortcodes' (#701) from erincandescent/akkoma:stealemojipolicy-sanitize into develop
Reviewed-on: AkkomaGang/akkoma#701
2024-02-20 15:08:54 +00:00
b387f4a1c1 Don't steal emoji who's shortcodes have dots or colons in their name
Mastodon at the very least seems to prevent the creation of emoji with
dots in their name (and refuses to accept them in federation). It feels
like being cautious in what we accept is reasonable here.

Colons are the emoji separator and so obviously should be blocked.

Perhaps instead of filtering out things like this we should just
do a regex match on `[a-zA-Z0-9_-]`? But that's plausibly a decision
for another day

    Perhaps we should also have a centralised "is this a valid emoji shortcode?"
    function
2024-02-20 11:33:55 +01:00
Haelwenn (lanodan) Monnier
7d94476dd6 StealEmojiPolicy: Sanitize shortcodes
Closes: https://git.pleroma.social/pleroma/pleroma/-/issues/3245
2024-02-20 11:19:00 +01:00
c25cfe9b7a fixed spelling 2024-02-19 23:25:20 +01:00
41dd37d796 doc/cheatsheet: add missing MRFs
Or mentions of MRFs in the main list
whose options were already documented.
2024-02-19 23:15:47 +01:00
9830d54fa1 doc/cheatsheet: sort main MRF list alphabetically
It is too cumbersome to find a specific policy atm
or to check if all are docuemtned yet.
Trivial placeholder policies are excluded from this.
2024-02-19 23:15:30 +01:00
f254e4f530 doc/cheatsheet: add missing MRF config detail docs
And remove “on by default” text from individual entries.
They are now laready in the “on by default” section.
2024-02-19 23:14:44 +01:00
da4190c46e doc/cheatsheet: split out always active MRFs
It doesn’t make sense to add/remove them from the policies list
2024-02-19 23:14:24 +01:00
7a2d68c3ab doc/cheatsheet: add link to ActivityExpiration config details 2024-02-19 23:14:07 +01:00
8e7a89605d doc/cheatsheet: move MRF policies key to end of section
This makes it easier to spot the transparency options
2024-02-19 23:13:48 +01:00
1640d19448 doc/cheatsheet: move :activitypub section ahead
Else it is too easy to mistake for another MRF policy.
2024-02-19 23:13:25 +01:00
8f1776a8a7 Purge leftovers from FollowBot MRF
It was dropped in 9db4c2429f
2024-02-19 23:13:05 +01:00
1ec6e193e6 doc: clarify RejectNewlyCreated uses local account discovery 2024-02-19 23:12:41 +01:00
37e2a35b86 Fix Twitter metadata
This partly reverts 1d884fd914
while fixing both the issue it addressed and the issue it caused.

The above commit successfully fixed OpenGraph metadata tags
which until then always showed the user bio instead of post content
by handing the activities AP ID as url to the Metadata builder
_instead_ of passing the internal ID as activity_id.
However, in doing so the commit instead inflicted this very problem
onto Twitter metadata tags which ironically are used by akkoma-fe.

This is because while the OpenGraph builder wants an URL as url,
the Twitter builder needs the internal ID to build the URL to the
embedded player for videos and has no URL property.

Thanks to twpol for tracking down this root cause in #644.

Now, once identified the problem is simple, but this simplicity
invites multiple possible solutions to bikeshed about.

 1. Just pass both properties to the builder and let them pick

 2. Drop the url parameter from the OpenGraph builder and instead
     a) build static-fe URL of the post from the ID (like Twitter)
     b) use the passed-in object’s AP ID as an URL

Approach 2a has the disadvantage of hardcoding the expected URL outside
the router, which will be problematic should it ever change.
Approach 2b is conceptually similar to how the builder works atm.
However, the og:url is supposed to be a _permanent_ ID, by changing it
we might, afaiui, technically violate OpenGraph specs(?). (Though its
real-world consequence may very well be near non-existent.)

This leaves just approach 1, which this commit implements.
Albeit it too is not without nits to pick, as it leaves the metadata
builders with an inconsistent interface.

Additionally, this will resolve the subotpimal Discord previews for
content-less image posts reported in #664.
Discord already prefers OpenGraph metadata, so it’s mostly unaffected.
However, it appears when encountering an explicitly empty OpenGraph
description and a non-empty Twitter description, it replaces just the
empty field with its Twitter counterpart, resulting in the user’s bio
slipping into the preview.
Secondly, regardless of any OpenGraph tags, Discord uses twitter:card to
decide how prominently images should be, but due to the bug the card
type was stuck as "summary", forcing images to always remain small.

Root cause identified by: twpol

Fixes: AkkomaGang/akkoma#644
Fixes: AkkomaGang/akkoma#664
2024-02-19 21:09:43 +00:00
086d6100e1 Merge pull request 'Disable busy waits in the default OTP vm.args configuration.' (#693) from erincandescent/akkoma:otp-tune-vm-busywait into develop
Reviewed-on: AkkomaGang/akkoma#693
2024-02-19 14:01:14 +00:00
3e24210e9f Merge pull request 'Prune old Update activities' (#683) from Oneric/akkoma:db-prune-old-updates into develop
Reviewed-on: AkkomaGang/akkoma#683
2024-02-19 13:59:33 +00:00
551ae69541 Merge pull request 'Fix and provide sane defaults for SMTP' (#686) from Oneric/akkoma:smtp-defaults into develop
Reviewed-on: AkkomaGang/akkoma#686
2024-02-19 13:39:15 +00:00
37f9626116 Merge pull request 'Docs: reword description for mrf_reject_newly_created_account_notes for more clarity' (#1) from stefan230/akkoma:doc_mrf_reject_acc_notes_patch into doc_mrf_reject_acc_notes
Reviewed-on: YokaiRick/akkoma#1
2024-02-17 22:19:32 +00:00
b4c832471c docs/docs/configuration/cheatsheet.md aktualisiert
fixed up some grammer / wording. removed a setence and made wording more in line with what I could find in Admin-FE (especially wording of "rejecting" vs. dropping)
2024-02-17 22:09:47 +00:00
db49daa4a5 make it clearer what it affects 2024-02-17 22:57:56 +01:00
718104117f fix link 2024-02-17 22:34:55 +01:00
12e7d0a25c added doc for mrf_reject_newly_created_account_notes 2024-02-17 22:25:12 +01:00
1a7839eaf2 Prune old Update activities
Once processed they serve no purpose anymore afaict.
Therefor, lets prune them like other transient activities
to not unnecessarily bloat the table.
2024-02-17 16:57:40 +01:00
1ef8b967d2 test: fix typos affecting remove factory
Apparently nothing used this factory until now
2024-02-17 16:57:40 +01:00
7a0e27a746 Disable busy waits in the default OTP vm.args configuration.
This vastly reduces idle CPU usage, which should generally be beneficial
for most small-to-medium sized instances.

Additionally update the documentation to specify how to override the vm.args
file for OTP installs
2024-02-17 13:21:56 +01:00
755c75d8a4 Merge pull request 'Clean up warnings (+fallback metrics)' (#685) from Oneric/akkoma:metrics into develop
Reviewed-on: AkkomaGang/akkoma#685
2024-02-17 11:41:10 +00:00
289f93f5a2 Merge pull request 'Return last_status_at as date, not datetime' (#681) from katafrakt/akkoma:fix-last-status-at into develop
Reviewed-on: AkkomaGang/akkoma#681
2024-02-17 11:37:19 +00:00
371b258c99 Merge pull request 'Fix SimplePolicy blocking account updates' (#692) from Oneric/akkoma:fix-background_removal into develop
Reviewed-on: AkkomaGang/akkoma#692
2024-02-17 10:34:16 +00:00