Add support for importing embedded self-quotes (#34584)

app/helpers/json_ld_helper.rb

@@ -72,6 +72,18 @@ module JsonLdHelper
     !haystack.casecmp(needle).zero?
   end
 
+  def safe_prefetched_embed(account, object, context)
+    return unless object.is_a?(Hash)
+
+    # NOTE: Replacing the object's context by that of the parent activity is
+    # not sound, but it's consistent with the rest of the codebase
+    object = object.merge({ '@context' => context })
+
+    return if value_or_id(first_of_value(object['attributedTo'])) != account.uri || non_matching_uri_hosts?(account.uri, object['id'])
+
+    object
+  end
+
   def canonicalize(json)
     graph = RDF::Graph.new << JSON::LD::API.toRdf(json, documentLoader: method(:load_jsonld_context))
     graph.dump(:normalize)

app/lib/activitypub/activity/create.rb

@@ -204,7 +204,9 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
 
     @quote.status = status
     @quote.save
-    ActivityPub::VerifyQuoteService.new.call(@quote, fetchable_quoted_uri: @quote_uri, request_id: @options[:request_id])
+
+    embedded_quote = safe_prefetched_embed(@account, @status_parser.quoted_object, @json['context'])
+    ActivityPub::VerifyQuoteService.new.call(@quote, fetchable_quoted_uri: @quote_uri, prefetched_quoted_object: embedded_quote, request_id: @options[:request_id])
   rescue Mastodon::UnexpectedResponseError, *Mastodon::HTTP_CONNECTION_ERRORS
     ActivityPub::RefetchAndVerifyQuoteWorker.perform_in(rand(30..600).seconds, @quote.id, @quote_uri, { 'request_id' => @options[:request_id] })
   end

app/lib/activitypub/parser/status_parser.rb

@@ -120,6 +120,11 @@ class ActivityPub::Parser::StatusParser
     end.first
   end
 
+  # The inlined quote; out of the attributes we support, only `https://w3id.org/fep/044f#quote` explicitly supports inlined objects
+  def quoted_object
+    as_array(@object['quote']).first
+  end
+
   def quote_approval_uri
     as_array(@object['quoteAuthorization']).first
   end

app/services/activitypub/process_status_update_service.rb

@@ -273,7 +273,6 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
   def update_quote!
     return unless Mastodon::Feature.inbound_quotes_enabled?
 
-    quote = nil
     quote_uri = @status_parser.quote_uri
 
     if quote_uri.present?
@@ -294,21 +293,23 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
         quote = Quote.create(status: @status, approval_uri: approval_uri)
         @quote_changed = true
       end
-    end
 
-    if quote.present?
-      begin
-        quote.save
-        ActivityPub::VerifyQuoteService.new.call(quote, fetchable_quoted_uri: quote_uri, request_id: @request_id)
-      rescue Mastodon::UnexpectedResponseError, *Mastodon::HTTP_CONNECTION_ERRORS
-        ActivityPub::RefetchAndVerifyQuoteWorker.perform_in(rand(30..600).seconds, quote.id, quote_uri, { 'request_id' => @request_id })
-      end
+      quote.save
+
+      fetch_and_verify_quote!(quote, quote_uri)
     elsif @status.quote.present?
       @status.quote.destroy!
       @quote_changed = true
     end
   end
 
+  def fetch_and_verify_quote!(quote, quote_uri)
+    embedded_quote = safe_prefetched_embed(@account, @status_parser.quoted_object, @activity_json['context'])
+    ActivityPub::VerifyQuoteService.new.call(quote, fetchable_quoted_uri: quote_uri, prefetched_quoted_object: embedded_quote, request_id: @request_id)
+  rescue Mastodon::UnexpectedResponseError, *Mastodon::HTTP_CONNECTION_ERRORS
+    ActivityPub::RefetchAndVerifyQuoteWorker.perform_in(rand(30..600).seconds, quote.id, quote_uri, { 'request_id' => @request_id })
+  end
+
   def update_counts!
     likes = @status_parser.favourites_count
     shares =  @status_parser.reblogs_count

app/services/activitypub/verify_quote_service.rb

@@ -4,15 +4,15 @@ class ActivityPub::VerifyQuoteService < BaseService
   include JsonLdHelper
 
   # Optionally fetch quoted post, and verify the quote is authorized
-  def call(quote, fetchable_quoted_uri: nil, prefetched_body: nil, request_id: nil)
+  def call(quote, fetchable_quoted_uri: nil, prefetched_quoted_object: nil, prefetched_approval: nil, request_id: nil)
     @request_id = request_id
     @quote = quote
     @fetching_error = nil
 
-    fetch_quoted_post_if_needed!(fetchable_quoted_uri)
+    fetch_quoted_post_if_needed!(fetchable_quoted_uri, prefetched_body: prefetched_quoted_object)
     return if fast_track_approval! || quote.approval_uri.blank?
 
-    @json = fetch_approval_object(quote.approval_uri, prefetched_body:)
+    @json = fetch_approval_object(quote.approval_uri, prefetched_body: prefetched_approval)
     return quote.reject! if @json.nil?
 
     return if non_matching_uri_hosts?(quote.approval_uri, value_or_id(@json['attributedTo']))
@@ -68,11 +68,11 @@ class ActivityPub::VerifyQuoteService < BaseService
     ActivityPub::TagManager.instance.uri_for(@quote.status) == value_or_id(@json['interactingObject'])
   end
 
-  def fetch_quoted_post_if_needed!(uri)
+  def fetch_quoted_post_if_needed!(uri, prefetched_body: nil)
     return if uri.nil? || @quote.quoted_status.present?
 
     status = ActivityPub::TagManager.instance.uri_to_resource(uri, Status)
-    status ||= ActivityPub::FetchRemoteStatusService.new.call(uri, on_behalf_of: @quote.account.followers.local.first, request_id: @request_id)
+    status ||= ActivityPub::FetchRemoteStatusService.new.call(uri, on_behalf_of: @quote.account.followers.local.first, prefetched_body:, request_id: @request_id)
 
     @quote.update(quoted_status: status) if status.present?
   rescue Mastodon::UnexpectedResponseError, *Mastodon::HTTP_CONNECTION_ERRORS => e

spec/services/activitypub/verify_quote_service_spec.rb

@@ -89,6 +89,37 @@ RSpec.describe ActivityPub::VerifyQuoteService do
       end
     end
 
+    context 'with a valid activity for a post that cannot be fetched but is passed as fetched_quoted_object' do
+      let(:quoted_status) { nil }
+
+      let(:approval_interaction_target) { 'https://b.example.com/unknown-quoted' }
+      let(:prefetched_object) do
+        {
+          '@context': 'https://www.w3.org/ns/activitystreams',
+          type: 'Note',
+          id: 'https://b.example.com/unknown-quoted',
+          to: 'https://www.w3.org/ns/activitystreams#Public',
+          attributedTo: ActivityPub::TagManager.instance.uri_for(quoted_account),
+          content: 'previously unknown post',
+        }.with_indifferent_access
+      end
+
+      before do
+        stub_request(:get, 'https://b.example.com/unknown-quoted')
+          .to_return(status: 404)
+      end
+
+      it 'updates the status' do
+        expect { subject.call(quote, fetchable_quoted_uri: 'https://b.example.com/unknown-quoted', prefetched_quoted_object: prefetched_object) }
+          .to change(quote, :state).to('accepted')
+
+        expect(a_request(:get, approval_uri))
+          .to have_been_made.once
+
+        expect(quote.reload.quoted_status.content).to eq 'previously unknown post'
+      end
+    end
+
     context 'with a valid activity for a post that cannot be fetched but is inlined' do
       let(:quoted_status) { nil }
 
@@ -148,7 +179,7 @@ RSpec.describe ActivityPub::VerifyQuoteService do
 
     context 'with a valid activity for already-fetched posts, with a pre-fetched approval' do
       it 'updates the status without fetching the activity' do
-        expect { subject.call(quote, prefetched_body: Oj.dump(json)) }
+        expect { subject.call(quote, prefetched_approval: Oj.dump(json)) }
           .to change(quote, :state).to('accepted')
 
         expect(a_request(:get, approval_uri))