Add initial support for ingesting and verifying remote quote posts (#34370)

app/services/activitypub/process_status_update_service.rb

@@ -16,6 +16,7 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
     @account                   = status.account
     @media_attachments_changed = false
     @poll_changed              = false
+    @quote_changed             = false
     @request_id                = request_id
 
     # Only native types can be updated at the moment
@@ -158,7 +159,7 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
     @status.sensitive    = @account.sensitized? || @status_parser.sensitive || false
     @status.language     = @status_parser.language
 
-    @significant_changes = text_significantly_changed? || @status.spoiler_text_changed? || @media_attachments_changed || @poll_changed
+    @significant_changes = text_significantly_changed? || @status.spoiler_text_changed? || @media_attachments_changed || @poll_changed || @quote_changed
 
     @status.edited_at = @status_parser.edited_at if significant_changes?
 
@@ -183,6 +184,7 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
     update_tags!
     update_mentions!
     update_emojis!
+    update_quote!
   end
 
   def update_tags!
@@ -262,6 +264,45 @@ class ActivityPub::ProcessStatusUpdateService < BaseService
     end
   end
 
+  def update_quote!
+    return unless Mastodon::Feature.inbound_quotes_enabled?
+
+    quote = nil
+    quote_uri = @status_parser.quote_uri
+
+    if quote_uri.present?
+      approval_uri = @status_parser.quote_approval_uri
+      approval_uri = nil if unsupported_uri_scheme?(approval_uri)
+
+      if @status.quote.present?
+        # If the quoted post has changed, discard the old object and create a new one
+        if @status.quote.quoted_status.present? && ActivityPub::TagManager.instance.uri_for(@status.quote.quoted_status) != quote_uri
+          @status.quote.destroy
+          quote = Quote.create(status: @status, approval_uri: approval_uri)
+          @quote_changed = true
+        else
+          quote = @status.quote
+          quote.update(approval_uri: approval_uri, state: :pending) if quote.approval_uri != @status_parser.quote_approval_uri
+        end
+      else
+        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
+    elsif @status.quote.present?
+      @status.quote.destroy!
+      @quote_changed = true
+    end
+  end
+
   def update_counts!
     likes = @status_parser.favourites_count
     shares =  @status_parser.reblogs_count

app/services/activitypub/verify_quote_service.rb

@@ -0,0 +1,112 @@
+# frozen_string_literal: true
+
+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)
+    @request_id = request_id
+    @quote = quote
+    @fetching_error = nil
+
+    fetch_quoted_post_if_needed!(fetchable_quoted_uri)
+    return if fast_track_approval! || quote.approval_uri.blank?
+
+    @json = fetch_approval_object(quote.approval_uri, prefetched_body:)
+    return quote.reject! if @json.nil?
+
+    return if non_matching_uri_hosts?(quote.approval_uri, value_or_id(@json['attributedTo']))
+    return unless matching_type? && matching_quote_uri?
+
+    # Opportunistically import embedded posts if needed
+    return if import_quoted_post_if_needed!(fetchable_quoted_uri) && fast_track_approval!
+
+    # Raise an error if we failed to fetch the status
+    raise @fetching_error if @quote.status.nil? && @fetching_error
+
+    return unless matching_quoted_post? && matching_quoted_author?
+
+    quote.accept!
+  end
+
+  private
+
+  # FEP-044f defines rules that don't require the approval flow
+  def fast_track_approval!
+    return false if @quote.quoted_status_id.blank?
+
+    # Always allow someone to quote themselves
+    if @quote.account_id == @quote.quoted_account_id
+      @quote.accept!
+
+      true
+    end
+
+    # Always allow someone to quote posts in which they are mentioned
+    if @quote.quoted_status.active_mentions.exists?(mentions: { account_id: @quote.account_id })
+      @quote.accept!
+
+      true
+    else
+      false
+    end
+  end
+
+  def fetch_approval_object(uri, prefetched_body: nil)
+    if prefetched_body.nil?
+      fetch_resource(uri, true, @quote.account.followers.local.first, raise_on_error: :temporary)
+    else
+      body_to_json(prefetched_body, compare_id: uri)
+    end
+  end
+
+  def matching_type?
+    supported_context?(@json) && equals_or_includes?(@json['type'], 'QuoteAuthorization')
+  end
+
+  def matching_quote_uri?
+    ActivityPub::TagManager.instance.uri_for(@quote.status) == value_or_id(@json['interactingObject'])
+  end
+
+  def fetch_quoted_post_if_needed!(uri)
+    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)
+
+    @quote.update(quoted_status: status) if status.present?
+  rescue Mastodon::UnexpectedResponseError, *Mastodon::HTTP_CONNECTION_ERRORS => e
+    @fetching_error = e
+  end
+
+  def import_quoted_post_if_needed!(uri)
+    # No need to fetch if we already have a post
+    return if uri.nil? || @quote.quoted_status_id.present? || !@json['interactionTarget'].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 = @json['interactionTarget'].merge({ '@context' => @json['@context'] })
+
+    # It's not safe to fetch if the inlined object is cross-origin or doesn't match expectations
+    return if object['id'] != uri || non_matching_uri_hosts?(@quote.approval_uri, object['id'])
+
+    status = ActivityPub::FetchRemoteStatusService.new.call(object['id'], prefetched_body: object, on_behalf_of: @quote.account.followers.local.first, request_id: @request_id)
+
+    if status.present?
+      @quote.update(quoted_status: status)
+      true
+    else
+      false
+    end
+  end
+
+  def matching_quoted_post?
+    return false if @quote.quoted_status_id.blank?
+
+    ActivityPub::TagManager.instance.uri_for(@quote.quoted_status) == value_or_id(@json['interactionTarget'])
+  end
+
+  def matching_quoted_author?
+    ActivityPub::TagManager.instance.uri_for(@quote.quoted_account) == value_or_id(@json['attributedTo'])
+  end
+end