Merge commit from fork

* enhance: Add a few validation fixes from Sharkey

See the original MR on the GitLab instance:
https://activitypub.software/TransFem-org/Sharkey/-/merge_requests/484

Co-Authored-By: Dakkar <dakkar@thenautilus.net>

* fix: primitive 2: acceptance of cross-origin alternate

Co-Authored-By: Laura Hausmann <laura@hausmann.dev>

* fix: primitive 3: validation of non-final url

* fix: primitive 4: missing same-origin identifier validation of collection-wrapped activities

* fix: primitives 5 & 8: reject activities with non
string identifiers

Co-Authored-By: Laura Hausmann <laura@hausmann.dev>

* fix: primitive 6: reject anonymous objects that were fetched by their id

* fix: primitives 9, 10 & 11: http signature validation
doesn't enforce required headers or specify auth header name

Co-Authored-By: Laura Hausmann <laura@hausmann.dev>

* fix: primitive 14: improper validation of outbox, followers, following & shared inbox collections

* fix: code style for primitive 14

* fix: primitive 15: improper same-origin validation for
note uri and url

Co-Authored-By: Laura Hausmann <laura@hausmann.dev>

* fix: primitive 16: improper same-origin validation for user uri and url

* fix: primitive 17: note same-origin identifier validation can be bypassed by wrapping the id in an array

* fix: code style for primitive 17

* fix: check attribution against actor in notes

While this isn't strictly required to fix the exploits at hand, this
mirrors the fix in `ApQuestionService` for GHSA-5h8r-gq97-xv69, as a
preemptive countermeasure.

* fix: primitive 18: `ap/get` bypasses access checks

One might argue that we could make this one actually preform access
checks against the returned activity object, but I feel like that's a
lot more work than just restricting it to administrators, since, to me
at least, it seems more like a debugging tool than anything else.

* fix: primitive 19 & 20: respect blocks and hide more

Ideally, the user property should also be hidden (as leaving it in leaks
information slightly), but given the schema of the note endpoint, I
don't think that would be possible without introducing some kind of
"ghost" user, who is attributed for posts by users who have you blocked.

* fix: primitives 21, 22, and 23: reuse resolver

This also increases the default `recursionLimit` for `Resolver`, as it
theoretically will go higher that it previously would and could possibly
fail on non-malicious collection activities.

* fix: primitives 25-33: proper local instance checks

* revert: fix: primitive 19 & 20

This reverts commit 465a9fe6591de90f78bd3d084e3c01e65dc3cf3c.

---------

Co-authored-by: Dakkar <dakkar@thenautilus.net>
Co-authored-by: Laura Hausmann <laura@hausmann.dev>
Co-authored-by: syuilo <4439005+syuilo@users.noreply.github.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/packages/backend/src/core/HttpRequestService.ts b/packages/backend/src/core/HttpRequestService.ts
index 7f3cac7c58..08e9f46b2d 100644
--- a/packages/backend/src/core/HttpRequestService.ts
+++ b/packages/backend/src/core/HttpRequestService.ts
@@ -15,6 +15,7 @@ import type { Config } from '@/config.js';
 import { StatusError } from '@/misc/status-error.js';
 import { bindThis } from '@/decorators.js';
 import { validateContentTypeSetAsActivityPub } from '@/core/activitypub/misc/validator.js';
+import { assertActivityMatchesUrls } from '@/core/activitypub/misc/check-against-url.js';
 import type { IObject } from '@/core/activitypub/type.js';
 import type { Response } from 'node-fetch';
 import type { URL } from 'node:url';
@@ -125,7 +126,12 @@ export class HttpRequestService {
 			validators: [validateContentTypeSetAsActivityPub],
 		});
 
-		return await res.json() as IObject;
+		const finalUrl = res.url; // redirects may have been involved
+		const activity = await res.json() as IObject;
+
+		assertActivityMatchesUrls(activity, [finalUrl]);
+
+		return activity;
 	}
 
 	@bindThis