Fix unbounded recursion in post discovery (#23506)

* Add a limit to how many posts can get fetched as a result of a single request

* Add tests

* Always pass `request_id` when processing `Announce` activities

---------

Co-authored-by: nametoolong <nametoolong@users.noreply.github.com>

app/lib/activitypub/activity.rb

@@ -106,7 +106,8 @@ class ActivityPub::Activity
       actor_id = value_or_id(first_of_value(@object['attributedTo']))
 
       if actor_id == @account.uri
-        return ActivityPub::Activity.factory({ 'type' => 'Create', 'actor' => actor_id, 'object' => @object }, @account).perform
+        virtual_object = { 'type' => 'Create', 'actor' => actor_id, 'object' => @object }
+        return ActivityPub::Activity.factory(virtual_object, @account, request_id: @options[:request_id]).perform
       end
     end
 
@@ -152,9 +153,9 @@ class ActivityPub::Activity
   def fetch_remote_original_status
     if object_uri.start_with?('http')
       return if ActivityPub::TagManager.instance.local_uri?(object_uri)
-      ActivityPub::FetchRemoteStatusService.new.call(object_uri, id: true, on_behalf_of: @account.followers.local.first)
+      ActivityPub::FetchRemoteStatusService.new.call(object_uri, id: true, on_behalf_of: @account.followers.local.first, request_id: @options[:request_id])
     elsif @object['url'].present?
-      ::FetchRemoteStatusService.new.call(@object['url'])
+      ::FetchRemoteStatusService.new.call(@object['url'], request_id: @options[:request_id])
     end
   end
 

app/lib/activitypub/activity/create.rb

@@ -327,18 +327,18 @@ class ActivityPub::Activity::Create < ActivityPub::Activity
   def resolve_thread(status)
     return unless status.reply? && status.thread.nil? && Request.valid_url?(in_reply_to_uri)
 
-    ThreadResolveWorker.perform_async(status.id, in_reply_to_uri)
+    ThreadResolveWorker.perform_async(status.id, in_reply_to_uri, { 'request_id' => @options[:request_id]})
   end
 
   def fetch_replies(status)
     collection = @object['replies']
     return if collection.nil?
 
-    replies = ActivityPub::FetchRepliesService.new.call(status, collection, false)
+    replies = ActivityPub::FetchRepliesService.new.call(status, collection, allow_synchronous_requests: false, request_id: @options[:request_id])
     return unless replies.nil?
 
     uri = value_or_id(collection)
-    ActivityPub::FetchRepliesWorker.perform_async(status.id, uri) unless uri.nil?
+    ActivityPub::FetchRepliesWorker.perform_async(status.id, uri, { 'request_id' => @options[:request_id]}) unless uri.nil?
   end
 
   def conversation_from_uri(uri)

app/services/activitypub/fetch_remote_status_service.rb

@@ -2,10 +2,13 @@
 
 class ActivityPub::FetchRemoteStatusService < BaseService
   include JsonLdHelper
+  include Redisable
+
+  DISCOVERIES_PER_REQUEST = 1000
 
   # Should be called when uri has already been checked for locality
   def call(uri, id: true, prefetched_body: nil, on_behalf_of: nil, expected_actor_uri: nil, request_id: nil)
-    @request_id = request_id
+    @request_id = request_id || "#{Time.now.utc.to_i}-status-#{uri}"
     @json = begin
       if prefetched_body.nil?
         fetch_resource(uri, id, on_behalf_of)
@@ -42,7 +45,13 @@ class ActivityPub::FetchRemoteStatusService < BaseService
     # activity as an update rather than create
     activity_json['type'] = 'Update' if equals_or_includes_any?(activity_json['type'], %w(Create)) && Status.where(uri: object_uri, account_id: actor.id).exists?
 
-    ActivityPub::Activity.factory(activity_json, actor, request_id: request_id).perform
+    with_redis do |redis|
+      discoveries = redis.incr("status_discovery_per_request:#{@request_id}")
+      redis.expire("status_discovery_per_request:#{@request_id}", 5.minutes.seconds)
+      return nil if discoveries > DISCOVERIES_PER_REQUEST
+    end
+
+    ActivityPub::Activity.factory(activity_json, actor, request_id: @request_id).perform
   end
 
   private

app/services/activitypub/fetch_replies_service.rb

@@ -3,14 +3,14 @@
 class ActivityPub::FetchRepliesService < BaseService
   include JsonLdHelper
 
-  def call(parent_status, collection_or_uri, allow_synchronous_requests = true)
+  def call(parent_status, collection_or_uri, allow_synchronous_requests: true, request_id: nil)
     @account = parent_status.account
     @allow_synchronous_requests = allow_synchronous_requests
 
     @items = collection_items(collection_or_uri)
     return if @items.nil?
 
-    FetchReplyWorker.push_bulk(filtered_replies)
+    FetchReplyWorker.push_bulk(filtered_replies) { |reply_uri| [reply_uri, { 'request_id' => request_id}] }
 
     @items
   end

app/services/fetch_remote_status_service.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
 class FetchRemoteStatusService < BaseService
-  def call(url, prefetched_body = nil)
+  def call(url, prefetched_body: nil, request_id: nil)
     if prefetched_body.nil?
       resource_url, resource_options = FetchResourceService.new.call(url)
     else
@@ -9,6 +9,6 @@ class FetchRemoteStatusService < BaseService
       resource_options = { prefetched_body: prefetched_body }
     end
 
-    ActivityPub::FetchRemoteStatusService.new.call(resource_url, **resource_options) unless resource_url.nil?
+    ActivityPub::FetchRemoteStatusService.new.call(resource_url, **resource_options.merge(request_id: request_id)) unless resource_url.nil?
   end
 end

app/services/resolve_url_service.rb

@@ -25,7 +25,7 @@ class ResolveURLService < BaseService
     if equals_or_includes_any?(type, ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES)
       ActivityPub::FetchRemoteActorService.new.call(resource_url, prefetched_body: body)
     elsif equals_or_includes_any?(type, ActivityPub::Activity::Create::SUPPORTED_TYPES + ActivityPub::Activity::Create::CONVERTED_TYPES)
-      status = FetchRemoteStatusService.new.call(resource_url, body)
+      status = FetchRemoteStatusService.new.call(resource_url, prefetched_body: body)
       authorize_with @on_behalf_of, status, :show? unless status.nil?
       status
     end

app/workers/activitypub/fetch_replies_worker.rb

@@ -6,8 +6,8 @@ class ActivityPub::FetchRepliesWorker
 
   sidekiq_options queue: 'pull', retry: 3
 
-  def perform(parent_status_id, replies_uri)
-    ActivityPub::FetchRepliesService.new.call(Status.find(parent_status_id), replies_uri)
+  def perform(parent_status_id, replies_uri, options = {})
+    ActivityPub::FetchRepliesService.new.call(Status.find(parent_status_id), replies_uri, **options.deep_symbolize_keys)
   rescue ActiveRecord::RecordNotFound
     true
   end

app/workers/fetch_reply_worker.rb

@@ -6,7 +6,7 @@ class FetchReplyWorker
 
   sidekiq_options queue: 'pull', retry: 3
 
-  def perform(child_url)
-    FetchRemoteStatusService.new.call(child_url)
+  def perform(child_url, options = {})
+    FetchRemoteStatusService.new.call(child_url, **options.deep_symbolize_keys)
   end
 end

app/workers/thread_resolve_worker.rb

@@ -6,9 +6,9 @@ class ThreadResolveWorker
 
   sidekiq_options queue: 'pull', retry: 3
 
-  def perform(child_status_id, parent_url)
+  def perform(child_status_id, parent_url, options = {})
     child_status  = Status.find(child_status_id)
-    parent_status = FetchRemoteStatusService.new.call(parent_url)
+    parent_status = FetchRemoteStatusService.new.call(parent_url, **options.deep_symbolize_keys)
 
     return if parent_status.nil?