Fix anonymous access to outbox not being cached by the reverse proxy (#16458)

* Fix anonymous access to outbox not being cached by the reverse proxy

Up until now, anonymous access to outbox was marked as public, but with a
0 duration for caching, which means remote proxies would only serve from cache
when the server was completely overwhelmed.

Changed that cache duration to one minute, so that repeated anonymous access
to one account's outbox can be appropriately cached.

Also added `Signature` to the `Vary` header in case a page is requested, so
that authenticated fetches are never served from cache (which only contains
public toots).

* Remove Vary: Accept header from webfinger controller

Indeed, we have stopped returning xrd, and only ever return jrd, so the
Accept request header does not matter anymore.

* Cache negative webfinger hits for 3 minutes

app/controllers/activitypub/outboxes_controller.rb

@@ -11,7 +11,11 @@ class ActivityPub::OutboxesController < ActivityPub::BaseController
   before_action :set_cache_headers
 
   def show
-    expires_in(page_requested? ? 0 : 3.minutes, public: public_fetch_mode? && !(signed_request_account.present? && page_requested?))
+    if page_requested?
+      expires_in(1.minute, public: public_fetch_mode? && signed_request_account.nil?)
+    else
+      expires_in(3.minutes, public: public_fetch_mode?)
+    end
     render json: outbox_presenter, serializer: ActivityPub::OutboxSerializer, adapter: ActivityPub::Adapter, content_type: 'application/activity+json'
   end
 
@@ -76,4 +80,8 @@ class ActivityPub::OutboxesController < ActivityPub::BaseController
   def set_account
     @account = params[:account_username].present? ? Account.find_local!(username_param) : Account.representative
   end
+
+  def set_cache_headers
+    response.headers['Vary'] = 'Signature' if authorized_fetch_mode? || page_requested?
+  end
 end

app/controllers/well_known/webfinger_controller.rb

@@ -4,7 +4,6 @@ module WellKnown
   class WebfingerController < ActionController::Base
     include RoutingHelper
 
-    before_action { response.headers['Vary'] = 'Accept' }
     before_action :set_account
     before_action :check_account_suspension
 
@@ -39,10 +38,12 @@ module WellKnown
     end
 
     def bad_request
+      expires_in(3.minutes, public: true)
       head 400
     end
 
     def not_found
+      expires_in(3.minutes, public: true)
       head 404
     end
 

spec/controllers/activitypub/outboxes_controller_spec.rb

@@ -55,6 +55,10 @@ RSpec.describe ActivityPub::OutboxesController, type: :controller do
 
         it_behaves_like 'cachable response'
 
+        it 'does not have a Vary header' do
+          expect(response.headers['Vary']).to be_nil
+        end
+
         context 'when account is permanently suspended' do
           before do
             account.suspend!
@@ -96,6 +100,10 @@ RSpec.describe ActivityPub::OutboxesController, type: :controller do
 
         it_behaves_like 'cachable response'
 
+        it 'returns Vary header with Signature' do
+          expect(response.headers['Vary']).to include 'Signature'
+        end
+
         context 'when account is permanently suspended' do
           before do
             account.suspend!
@@ -144,7 +152,7 @@ RSpec.describe ActivityPub::OutboxesController, type: :controller do
         end
 
         it 'returns private Cache-Control header' do
-          expect(response.headers['Cache-Control']).to eq 'max-age=0, private'
+          expect(response.headers['Cache-Control']).to eq 'max-age=60, private'
         end
       end
 
@@ -170,7 +178,7 @@ RSpec.describe ActivityPub::OutboxesController, type: :controller do
         end
 
         it 'returns private Cache-Control header' do
-          expect(response.headers['Cache-Control']).to eq 'max-age=0, private'
+          expect(response.headers['Cache-Control']).to eq 'max-age=60, private'
         end
       end
 
@@ -195,7 +203,7 @@ RSpec.describe ActivityPub::OutboxesController, type: :controller do
         end
 
         it 'returns private Cache-Control header' do
-          expect(response.headers['Cache-Control']).to eq 'max-age=0, private'
+          expect(response.headers['Cache-Control']).to eq 'max-age=60, private'
         end
       end
 
@@ -220,7 +228,7 @@ RSpec.describe ActivityPub::OutboxesController, type: :controller do
         end
 
         it 'returns private Cache-Control header' do
-          expect(response.headers['Cache-Control']).to eq 'max-age=0, private'
+          expect(response.headers['Cache-Control']).to eq 'max-age=60, private'
         end
       end
     end

spec/controllers/well_known/webfinger_controller_spec.rb

@@ -24,6 +24,10 @@ describe WellKnown::WebfingerController, type: :controller do
         expect(response).to have_http_status(200)
       end
 
+      it 'does not set a Vary header' do
+        expect(response.headers['Vary']).to be_nil
+      end
+
       it 'returns application/jrd+json' do
         expect(response.media_type).to eq 'application/jrd+json'
       end