Merge commit from fork

* Add validation to reject quotes of reblogs

* Do not process quotes of reblogs as potentially valid quotes

* Refuse to serve quoted reblogs over REST API

app/models/quote.rb

@@ -34,6 +34,7 @@ class Quote < ApplicationRecord
   before_validation :set_activity_uri, only: :create, if: -> { account.local? && quoted_account&.remote? }
   validates :activity_uri, presence: true, if: -> { account.local? && quoted_account&.remote? }
   validate :validate_visibility
+  validate :validate_original_quoted_status
 
   def accept!
     update!(state: :accepted)
@@ -70,6 +71,10 @@ class Quote < ApplicationRecord
     errors.add(:quoted_status_id, :visibility_mismatch)
   end
 
+  def validate_original_quoted_status
+    errors.add(:quoted_status_id, :reblog_unallowed) if quoted_status&.reblog?
+  end
+
   def set_activity_uri
     self.activity_uri = [ActivityPub::TagManager.instance.uri_for(account), '/quote_requests/', SecureRandom.uuid].join
   end

app/serializers/rest/base_quote_serializer.rb

@@ -14,7 +14,7 @@ class REST::BaseQuoteSerializer < ActiveModel::Serializer
   end
 
   def quoted_status
-    object.quoted_status if object.accepted? && object.quoted_status.present? && !status_filter.filtered_for_quote?
+    object.quoted_status if object.accepted? && object.quoted_status.present? && !object.quoted_status&.reblog? && !status_filter.filtered_for_quote?
   end
 
   private

app/services/activitypub/verify_quote_service.rb

@@ -72,7 +72,7 @@ class ActivityPub::VerifyQuoteService < BaseService
 
     status ||= ActivityPub::FetchRemoteStatusService.new.call(uri, on_behalf_of: @quote.account.followers.local.first, prefetched_body:, request_id: @request_id, depth: @depth + 1)
 
-    @quote.update(quoted_status: status) if status.present?
+    @quote.update(quoted_status: status) if status.present? && !status.reblog?
   rescue Mastodon::RecursionLimitExceededError, Mastodon::UnexpectedResponseError, *Mastodon::HTTP_CONNECTION_ERRORS => e
     @fetching_error = e
   end
@@ -90,7 +90,7 @@ class ActivityPub::VerifyQuoteService < BaseService
 
     status = ActivityPub::FetchRemoteStatusService.new.call(object['id'], prefetched_body: object, on_behalf_of: @quote.account.followers.local.first, request_id: @request_id, depth: @depth)
 
-    if status.present?
+    if status.present? && !status.reblog?
       @quote.update(quoted_status: status)
       true
     else

spec/lib/activitypub/activity/create_spec.rb

@@ -1046,6 +1046,60 @@ RSpec.describe ActivityPub::Activity::Create do
         end
       end
 
+      context 'with a quote of a known reblog that is otherwise valid' do
+        let(:quoted_account) { Fabricate(:account, domain: 'quoted.example.com') }
+        let(:quoted_status) { Fabricate(:status, account: quoted_account, reblog: Fabricate(:status)) }
+        let(:approval_uri) { 'https://quoted.example.com/quote-approval' }
+
+        let(:object_json) do
+          build_object(
+            type: 'Note',
+            content: 'woah what she said is amazing',
+            quote: ActivityPub::TagManager.instance.uri_for(quoted_status),
+            quoteAuthorization: approval_uri
+          )
+        end
+
+        before do
+          stub_request(:get, approval_uri).to_return(headers: { 'Content-Type': 'application/activity+json' }, body: Oj.dump({
+            '@context': [
+              'https://www.w3.org/ns/activitystreams',
+              {
+                QuoteAuthorization: 'https://w3id.org/fep/044f#QuoteAuthorization',
+                gts: 'https://gotosocial.org/ns#',
+                interactionPolicy: {
+                  '@id': 'gts:interactionPolicy',
+                  '@type': '@id',
+                },
+                interactingObject: {
+                  '@id': 'gts:interactingObject',
+                  '@type': '@id',
+                },
+                interactionTarget: {
+                  '@id': 'gts:interactionTarget',
+                  '@type': '@id',
+                },
+              },
+            ],
+            type: 'QuoteAuthorization',
+            id: approval_uri,
+            attributedTo: ActivityPub::TagManager.instance.uri_for(quoted_status.account),
+            interactingObject: object_json[:id],
+            interactionTarget: ActivityPub::TagManager.instance.uri_for(quoted_status),
+          }))
+        end
+
+        it 'creates a status without the verified quote' do
+          expect { subject.perform }.to change(sender.statuses, :count).by(1)
+
+          status = sender.statuses.first
+          expect(status).to_not be_nil
+          expect(status.quote).to_not be_nil
+          expect(status.quote.state).to_not eq 'accepted'
+          expect(status.quote.quoted_status).to be_nil
+        end
+      end
+
       context 'when a vote to a local poll' do
         let(:poll) { Fabricate(:poll, options: %w(Yellow Blue)) }
         let!(:local_status) { Fabricate(:status, poll: poll) }

spec/services/activitypub/process_status_update_service_spec.rb

@@ -733,6 +733,72 @@ RSpec.describe ActivityPub::ProcessStatusUpdateService do
     end
   end
 
+  context 'when the status adds a verifiable quote of a reblog through an explicit update' do
+    let(:quoted_account) { Fabricate(:account, domain: 'quoted.example.com') }
+    let(:quoted_status) { Fabricate(:status, account: quoted_account, reblog: Fabricate(:status)) }
+    let(:approval_uri) { 'https://quoted.example.com/approvals/1' }
+
+    let(:payload) do
+      {
+        '@context': [
+          'https://www.w3.org/ns/activitystreams',
+          {
+            '@id': 'https://w3id.org/fep/044f#quote',
+            '@type': '@id',
+          },
+          {
+            '@id': 'https://w3id.org/fep/044f#quoteAuthorization',
+            '@type': '@id',
+          },
+        ],
+        id: 'foo',
+        type: 'Note',
+        summary: 'Show more',
+        content: 'Hello universe',
+        updated: '2021-09-08T22:39:25Z',
+        quote: ActivityPub::TagManager.instance.uri_for(quoted_status),
+        quoteAuthorization: approval_uri,
+      }
+    end
+
+    before do
+      stub_request(:get, approval_uri).to_return(headers: { 'Content-Type': 'application/activity+json' }, body: Oj.dump({
+        '@context': [
+          'https://www.w3.org/ns/activitystreams',
+          {
+            QuoteAuthorization: 'https://w3id.org/fep/044f#QuoteAuthorization',
+            gts: 'https://gotosocial.org/ns#',
+            interactionPolicy: {
+              '@id': 'gts:interactionPolicy',
+              '@type': '@id',
+            },
+            interactingObject: {
+              '@id': 'gts:interactingObject',
+              '@type': '@id',
+            },
+            interactionTarget: {
+              '@id': 'gts:interactionTarget',
+              '@type': '@id',
+            },
+          },
+        ],
+        type: 'QuoteAuthorization',
+        id: approval_uri,
+        attributedTo: ActivityPub::TagManager.instance.uri_for(quoted_status.account),
+        interactingObject: ActivityPub::TagManager.instance.uri_for(status),
+        interactionTarget: ActivityPub::TagManager.instance.uri_for(quoted_status),
+      }))
+    end
+
+    it 'updates the approval URI but does not verify the quote' do
+      expect { subject.call(status, json, json) }
+        .to change(status, :quote).from(nil)
+      expect(status.quote.approval_uri).to eq approval_uri
+      expect(status.quote.state).to_not eq 'accepted'
+      expect(status.quote.quoted_status).to be_nil
+    end
+  end
+
   context 'when the status adds a unverifiable quote through an implicit update' do
     let(:quoted_account) { Fabricate(:account, domain: 'quoted.example.com') }
     let(:quoted_status) { Fabricate(:status, account: quoted_account) }