Add avatar image to webfinger responses (#26558)

app/serializers/webfinger_serializer.rb

@@ -18,18 +18,31 @@ class WebfingerSerializer < ActiveModel::Serializer
   end
 
   def links
-    if object.instance_actor?
     [
-        { rel: 'http://webfinger.net/rel/profile-page', type: 'text/html', href: about_more_url(instance_actor: true) },
-        { rel: 'self', type: 'application/activity+json', href: instance_actor_url },
+      { rel: 'http://webfinger.net/rel/profile-page', type: 'text/html', href: profile_page_href },
+      { rel: 'self', type: 'application/activity+json', href: self_href },
       { rel: 'http://ostatus.org/schema/1.0/subscribe', template: "#{authorize_interaction_url}?uri={uri}" },
-      ]
-    else
-      [
-        { rel: 'http://webfinger.net/rel/profile-page', type: 'text/html', href: short_account_url(object) },
-        { rel: 'self', type: 'application/activity+json', href: account_url(object) },
-        { rel: 'http://ostatus.org/schema/1.0/subscribe', template: "#{authorize_interaction_url}?uri={uri}" },
-      ]
+    ].tap do |x|
+      x << { rel: 'http://webfinger.net/rel/avatar', type: object.avatar.content_type, href: full_asset_url(object.avatar_original_url) } if show_avatar?
     end
   end
+
+  private
+
+  def show_avatar?
+    media_present = object.avatar.present? && object.avatar.content_type.present?
+
+    # Show avatar only if an instance shows profiles to logged out users
+    allowed_by_config = ENV['DISALLOW_UNAUTHENTICATED_API_ACCESS'] != 'true' && !Rails.configuration.x.limited_federation_mode
+
+    media_present && allowed_by_config
+  end
+
+  def profile_page_href
+    object.instance_actor? ? about_more_url(instance_actor: true) : short_account_url(object)
+  end
+
+  def self_href
+    object.instance_actor? ? instance_actor_url : account_url(object)
+  end
 end

spec/controllers/well_known/webfinger_controller_spec.rb

@@ -3,6 +3,8 @@
 require 'rails_helper'
 
 describe WellKnown::WebfingerController do
+  include RoutingHelper
+
   render_views
 
   describe 'GET #show' do
@@ -167,5 +169,67 @@ describe WellKnown::WebfingerController do
         expect(response).to have_http_status(400)
       end
     end
+
+    context 'when an account has an avatar' do
+      let(:alice) { Fabricate(:account, username: 'alice', avatar: attachment_fixture('attachment.jpg')) }
+      let(:resource) { alice.to_webfinger_s }
+
+      it 'returns avatar in response' do
+        perform_show!
+
+        avatar_link = get_avatar_link(body_as_json)
+        expect(avatar_link).to_not be_nil
+        expect(avatar_link[:type]).to eq alice.avatar.content_type
+        expect(avatar_link[:href]).to eq full_asset_url(alice.avatar)
+      end
+
+      context 'with limited federation mode' do
+        before do
+          allow(Rails.configuration.x).to receive(:limited_federation_mode).and_return(true)
+        end
+
+        it 'does not return avatar in response' do
+          perform_show!
+
+          avatar_link = get_avatar_link(body_as_json)
+          expect(avatar_link).to be_nil
+        end
+      end
+
+      context 'when enabling DISALLOW_UNAUTHENTICATED_API_ACCESS' do
+        around do |example|
+          ClimateControl.modify DISALLOW_UNAUTHENTICATED_API_ACCESS: 'true' do
+            example.run
+          end
+        end
+
+        it 'does not return avatar in response' do
+          perform_show!
+
+          avatar_link = get_avatar_link(body_as_json)
+          expect(avatar_link).to be_nil
+        end
+      end
+    end
+
+    context 'when an account does not have an avatar' do
+      let(:alice) { Fabricate(:account, username: 'alice', avatar: nil) }
+      let(:resource) { alice.to_webfinger_s }
+
+      before do
+        perform_show!
+      end
+
+      it 'does not return avatar in response' do
+        avatar_link = get_avatar_link(body_as_json)
+        expect(avatar_link).to be_nil
+      end
+    end
+  end
+
+  private
+
+  def get_avatar_link(json)
+    json[:links].find { |link| link[:rel] == 'http://webfinger.net/rel/avatar' }
   end
 end