Fix poll API not requiring authentication on non-public polls (#10960)

* Fix poll API not requiring authentication on non-public polls

That API does not reveal the content of the status, i.e. the question
itself, nor who the author is, nor which status it belongs to, but it
does reveal the poll options and how many answers they got

Fix #10959

* Add test

app/controllers/api/v1/polls_controller.rb

@@ -1,13 +1,28 @@
 # frozen_string_literal: true
 
 class Api::V1::PollsController < Api::BaseController
+  include Authorization
+
   before_action -> { authorize_if_got_token! :read, :'read:statuses' }, only: :show
+  before_action :set_poll
+  before_action :refresh_poll
 
   respond_to :json
 
   def show
-    @poll = Poll.attached.find(params[:id])
-    ActivityPub::FetchRemotePollService.new.call(@poll, current_account) if user_signed_in? && @poll.possibly_stale?
     render json: @poll, serializer: REST::PollSerializer, include_results: true
   end
+
+  private
+
+  def set_poll
+    @poll = Poll.attached.find(params[:id])
+    authorize @poll.status, :show?
+  rescue Mastodon::NotPermittedError
+    raise ActiveRecord::RecordNotFound
+  end
+
+  def refresh_poll
+    ActivityPub::FetchRemotePollService.new.call(@poll, current_account) if user_signed_in? && @poll.possibly_stale?
+  end
 end

spec/controllers/api/v1/polls_controller_spec.rb

@@ -10,14 +10,26 @@ RSpec.describe Api::V1::PollsController, type: :controller do
   before { allow(controller).to receive(:doorkeeper_token) { token } }
 
   describe 'GET #show' do
-    let(:poll) { Fabricate(:poll) }
+    let(:poll) { Fabricate(:poll, status: Fabricate(:status, visibility: visibility)) }
 
     before do
       get :show, params: { id: poll.id }
     end
 
+    context 'when parent status is public' do
+      let(:visibility) { 'public' }
+
       it 'returns http success' do
         expect(response).to have_http_status(200)
       end
     end
+
+    context 'when parent status is private' do
+      let(:visibility) { 'private' }
+
+      it 'returns http not found' do
+        expect(response).to have_http_status(404)
+      end
+    end
+  end
 end