From 3a2003ba863252f305fb32098bcd3f095b10e2ff Mon Sep 17 00:00:00 2001
From: Jack Jennings <jack@standard-library.com>
Date: Mon, 29 May 2017 09:22:22 -0700
Subject: [PATCH] Extract authorization policy for viewing statuses (#3150)

---
 Gemfile                                       |  1 +
 Gemfile.lock                                  |  3 +
 .../api/activitypub/activities_controller.rb  |  4 +-
 .../api/activitypub/notes_controller.rb       |  4 +-
 app/controllers/api/v1/statuses_controller.rb |  7 +-
 app/controllers/concerns/authorization.rb     | 22 ++++++
 app/controllers/media_controller.rb           |  7 +-
 app/controllers/statuses_controller.rb        |  7 +-
 app/controllers/stream_entries_controller.rb  |  8 ++-
 app/models/status.rb                          | 12 +---
 app/policies/status_policy.rb                 | 20 ++++++
 app/services/favourite_service.rb             |  4 +-
 app/services/reblog_service.rb                |  4 +-
 spec/controllers/media_controller_spec.rb     |  2 +-
 spec/models/status_spec.rb                    | 60 ----------------
 spec/policies/status_policy_spec.rb           | 70 +++++++++++++++++++
 16 files changed, 155 insertions(+), 80 deletions(-)
 create mode 100644 app/controllers/concerns/authorization.rb
 create mode 100644 app/policies/status_policy.rb
 create mode 100644 spec/policies/status_policy_spec.rb

diff --git a/Gemfile b/Gemfile
index 811dd1f99f..1246658374 100644
--- a/Gemfile
+++ b/Gemfile
@@ -38,6 +38,7 @@ gem 'nokogiri', '~> 1.7'
 gem 'oj', '~> 3.0'
 gem 'ostatus2', '~> 2.0'
 gem 'ox', '~> 2.5'
+gem 'pundit', '~> 1.1'
 gem 'rabl', '~> 0.13'
 gem 'rack-attack', '~> 5.0'
 gem 'rack-cors', '~> 0.4', require: 'rack/cors'
diff --git a/Gemfile.lock b/Gemfile.lock
index e8c3ba4870..69429c979b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -283,6 +283,8 @@ GEM
       pry (>= 0.10.4)
     public_suffix (2.0.5)
     puma (3.8.2)
+    pundit (1.1.0)
+      activesupport (>= 3.0.0)
     rabl (0.13.1)
       activesupport (>= 2.3.14)
     rack (2.0.3)
@@ -519,6 +521,7 @@ DEPENDENCIES
   pkg-config (~> 1.2)
   pry-rails (~> 0.3)
   puma (~> 3.8)
+  pundit (~> 1.1)
   rabl (~> 0.13)
   rack-attack (~> 5.0)
   rack-cors (~> 0.4)
diff --git a/app/controllers/api/activitypub/activities_controller.rb b/app/controllers/api/activitypub/activities_controller.rb
index ba03738fc9..025ab960e3 100644
--- a/app/controllers/api/activitypub/activities_controller.rb
+++ b/app/controllers/api/activitypub/activities_controller.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class Api::Activitypub::ActivitiesController < ApiController
+  include Authorization
+
   # before_action :set_follow, only: [:show_follow]
   before_action :set_status, only: [:show_status]
 
@@ -8,7 +10,7 @@ class Api::Activitypub::ActivitiesController < ApiController
 
   # Show a status in AS2 format, as either an Announce (reblog) or a Create (post) activity.
   def show_status
-    return forbidden unless @status.permitted?
+    authorize @status, :show?
 
     if @status.reblog?
       render :show_status_announce
diff --git a/app/controllers/api/activitypub/notes_controller.rb b/app/controllers/api/activitypub/notes_controller.rb
index 6489243dc0..ff9383413b 100644
--- a/app/controllers/api/activitypub/notes_controller.rb
+++ b/app/controllers/api/activitypub/notes_controller.rb
@@ -1,12 +1,14 @@
 # frozen_string_literal: true
 
 class Api::Activitypub::NotesController < ApiController
+  include Authorization
+
   before_action :set_status
 
   respond_to :activitystreams2
 
   def show
-    forbidden unless @status.permitted?
+    authorize @status, :show?
   end
 
   private
diff --git a/app/controllers/api/v1/statuses_controller.rb b/app/controllers/api/v1/statuses_controller.rb
index 852ffc3ab1..592540f457 100644
--- a/app/controllers/api/v1/statuses_controller.rb
+++ b/app/controllers/api/v1/statuses_controller.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class Api::V1::StatusesController < ApiController
+  include Authorization
+
   before_action :authorize_if_got_token, except:            [:create, :destroy, :reblog, :unreblog, :favourite, :unfavourite, :mute, :unmute]
   before_action -> { doorkeeper_authorize! :write }, only:  [:create, :destroy, :reblog, :unreblog, :favourite, :unfavourite, :mute, :unmute]
   before_action :require_user!, except:  [:show, :context, :card, :reblogged_by, :favourited_by]
@@ -130,7 +132,10 @@ class Api::V1::StatusesController < ApiController
 
   def set_status
     @status = Status.find(params[:id])
-    raise ActiveRecord::RecordNotFound unless @status.permitted?(current_account)
+    authorize @status, :show?
+  rescue Mastodon::NotPermittedError
+    # Reraise in order to get a 404 instead of a 403 error code
+    raise ActiveRecord::RecordNotFound
   end
 
   def set_conversation
diff --git a/app/controllers/concerns/authorization.rb b/app/controllers/concerns/authorization.rb
new file mode 100644
index 0000000000..7828fe48de
--- /dev/null
+++ b/app/controllers/concerns/authorization.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module Authorization
+  extend ActiveSupport::Concern
+  include Pundit
+
+  def pundit_user
+    current_account
+  end
+
+  def authorize(*)
+    super
+  rescue Pundit::NotAuthorizedError
+    raise Mastodon::NotPermittedError
+  end
+
+  def authorize_with(user, record, query)
+    Pundit.authorize(user, record, query)
+  rescue Pundit::NotAuthorizedError
+    raise Mastodon::NotPermittedError
+  end
+end
diff --git a/app/controllers/media_controller.rb b/app/controllers/media_controller.rb
index fa1daf012a..f652f5acef 100644
--- a/app/controllers/media_controller.rb
+++ b/app/controllers/media_controller.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class MediaController < ApplicationController
+  include Authorization
+
   before_action :verify_permitted_status
 
   def show
@@ -14,6 +16,9 @@ class MediaController < ApplicationController
   end
 
   def verify_permitted_status
-    raise ActiveRecord::RecordNotFound unless media_attachment.status.permitted?(current_account)
+    authorize media_attachment.status, :show?
+  rescue Mastodon::NotPermittedError
+    # Reraise in order to get a 404 instead of a 403 error code
+    raise ActiveRecord::RecordNotFound
   end
 end
diff --git a/app/controllers/statuses_controller.rb b/app/controllers/statuses_controller.rb
index 696bb4f521..59c9d0a87f 100644
--- a/app/controllers/statuses_controller.rb
+++ b/app/controllers/statuses_controller.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class StatusesController < ApplicationController
+  include Authorization
+
   layout 'public'
 
   before_action :set_account
@@ -30,7 +32,10 @@ class StatusesController < ApplicationController
     @stream_entry = @status.stream_entry
     @type         = @stream_entry.activity_type.downcase
 
-    raise ActiveRecord::RecordNotFound unless @status.permitted?(current_account)
+    authorize @status, :show?
+  rescue Mastodon::NotPermittedError
+    # Reraise in order to get a 404
+    raise ActiveRecord::RecordNotFound
   end
 
   def check_account_suspension
diff --git a/app/controllers/stream_entries_controller.rb b/app/controllers/stream_entries_controller.rb
index baff4317a3..314d596190 100644
--- a/app/controllers/stream_entries_controller.rb
+++ b/app/controllers/stream_entries_controller.rb
@@ -1,6 +1,8 @@
 # frozen_string_literal: true
 
 class StreamEntriesController < ApplicationController
+  include Authorization
+
   layout 'public'
 
   before_action :set_account
@@ -42,7 +44,11 @@ class StreamEntriesController < ApplicationController
     @stream_entry = @account.stream_entries.where(activity_type: 'Status').find(params[:id])
     @type         = @stream_entry.activity_type.downcase
 
-    raise ActiveRecord::RecordNotFound if @stream_entry.activity.nil? || (@stream_entry.hidden? && !@stream_entry.activity.permitted?(current_account))
+    raise ActiveRecord::RecordNotFound if @stream_entry.activity.nil?
+    authorize @stream_entry.activity, :show? if @stream_entry.hidden?
+  rescue Mastodon::NotPermittedError
+    # Reraise in order to get a 404
+    raise ActiveRecord::RecordNotFound
   end
 
   def check_account_suspension
diff --git a/app/models/status.rb b/app/models/status.rb
index a3dbce9f13..a371083d05 100644
--- a/app/models/status.rb
+++ b/app/models/status.rb
@@ -113,16 +113,6 @@ class Status < ApplicationRecord
     private_visibility? || direct_visibility?
   end
 
-  def permitted?(other_account = nil)
-    if direct_visibility?
-      account.id == other_account&.id || mentions.where(account: other_account).exists?
-    elsif private_visibility?
-      account.id == other_account&.id || other_account&.following?(account) || mentions.where(account: other_account).exists?
-    else
-      other_account.nil? || !account.blocking?(other_account)
-    end
-  end
-
   def ancestors(account = nil)
     ids = Rails.cache.fetch("ancestors:#{id}") { (Status.find_by_sql(['WITH RECURSIVE search_tree(id, in_reply_to_id, path) AS (SELECT id, in_reply_to_id, ARRAY[id] FROM statuses WHERE id = ? UNION ALL SELECT statuses.id, statuses.in_reply_to_id, path || statuses.id FROM search_tree JOIN statuses ON statuses.id = search_tree.in_reply_to_id WHERE NOT statuses.id = ANY(path)) SELECT id FROM search_tree ORDER BY path DESC', id]) - [self]).pluck(:id) }
     find_statuses_from_tree_path(ids, account)
@@ -301,7 +291,7 @@ class Status < ApplicationRecord
     should_filter ||= account&.domain_blocking?(status.account.domain)
     should_filter ||= account&.muting?(status.account_id)
     should_filter ||= (status.account.silenced? && !account&.following?(status.account_id))
-    should_filter ||= !status.permitted?(account)
+    should_filter ||= !StatusPolicy.new(account, status).show?
     should_filter
   end
 end
diff --git a/app/policies/status_policy.rb b/app/policies/status_policy.rb
new file mode 100644
index 0000000000..658ba6d123
--- /dev/null
+++ b/app/policies/status_policy.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class StatusPolicy
+  attr_reader :account, :status
+
+  def initialize(account, status)
+    @account = account
+    @status = status
+  end
+
+  def show?
+    if status.direct_visibility?
+      status.account.id == account&.id || status.mentions.where(account: account).exists?
+    elsif status.private_visibility?
+      status.account.id == account&.id || account&.following?(status.account) || status.mentions.where(account: account).exists?
+    else
+      account.nil? || !status.account.blocking?(account)
+    end
+  end
+end
diff --git a/app/services/favourite_service.rb b/app/services/favourite_service.rb
index e92aada64f..f27145c961 100644
--- a/app/services/favourite_service.rb
+++ b/app/services/favourite_service.rb
@@ -1,12 +1,14 @@
 # frozen_string_literal: true
 
 class FavouriteService < BaseService
+  include Authorization
+
   # Favourite a status and notify remote user
   # @param [Account] account
   # @param [Status] status
   # @return [Favourite]
   def call(account, status)
-    raise Mastodon::NotPermittedError unless status.permitted?(account)
+    authorize_with account, status, :show?
 
     favourite = Favourite.create!(account: account, status: status)
 
diff --git a/app/services/reblog_service.rb b/app/services/reblog_service.rb
index 11446ce28b..9c44b1980e 100644
--- a/app/services/reblog_service.rb
+++ b/app/services/reblog_service.rb
@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 class ReblogService < BaseService
+  include Authorization
   include StreamEntryRenderer
 
   # Reblog a status and notify its remote author
@@ -10,7 +11,8 @@ class ReblogService < BaseService
   def call(account, reblogged_status)
     reblogged_status = reblogged_status.reblog if reblogged_status.reblog?
 
-    raise Mastodon::NotPermittedError if reblogged_status.direct_visibility? || reblogged_status.private_visibility? || !reblogged_status.permitted?(account)
+    authorize_with account, reblogged_status, :show?
+    raise Mastodon::NotPermittedError if reblogged_status.direct_visibility? || reblogged_status.private_visibility?
 
     reblog = account.statuses.create!(reblog: reblogged_status, text: '')
 
diff --git a/spec/controllers/media_controller_spec.rb b/spec/controllers/media_controller_spec.rb
index 2541df7344..5b03899e4c 100644
--- a/spec/controllers/media_controller_spec.rb
+++ b/spec/controllers/media_controller_spec.rb
@@ -30,7 +30,7 @@ describe MediaController do
     it 'raises when not permitted to view' do
       status = Fabricate(:status)
       media_attachment = Fabricate(:media_attachment, status: status)
-      allow_any_instance_of(Status).to receive(:permitted?).and_return(false)
+      allow_any_instance_of(MediaController).to receive(:authorize).and_raise(ActiveRecord::RecordNotFound)
       get :show, params: { id: media_attachment.to_param }
 
       expect(response).to have_http_status(:missing)
diff --git a/spec/models/status_spec.rb b/spec/models/status_spec.rb
index d3a66134b2..ec07e61568 100644
--- a/spec/models/status_spec.rb
+++ b/spec/models/status_spec.rb
@@ -119,66 +119,6 @@ RSpec.describe Status, type: :model do
     end
   end
 
-  describe '#permitted?' do
-    it 'returns true when direct and account is viewer' do
-      subject.visibility = :direct
-      expect(subject.permitted?(subject.account)).to be true
-    end
-
-    it 'returns true when direct and viewer is mentioned' do
-      subject.visibility = :direct
-      subject.mentions = [Fabricate(:mention, account: alice)]
-
-      expect(subject.permitted?(alice)).to be true
-    end
-
-    it 'returns false when direct and viewer is not mentioned' do
-      viewer = Fabricate(:account)
-      subject.visibility = :direct
-
-      expect(subject.permitted?(viewer)).to be false
-    end
-
-    it 'returns true when private and account is viewer' do
-      subject.visibility = :direct
-      expect(subject.permitted?(subject.account)).to be true
-    end
-
-    it 'returns true when private and account is following viewer' do
-      follow = Fabricate(:follow)
-      subject.visibility = :private
-      subject.account = follow.target_account
-
-      expect(subject.permitted?(follow.account)).to be true
-    end
-
-    it 'returns true when private and viewer is mentioned' do
-      subject.visibility = :private
-      subject.mentions = [Fabricate(:mention, account: alice)]
-
-      expect(subject.permitted?(alice)).to be true
-    end
-
-    it 'returns false when private and viewer is not mentioned or followed' do
-      viewer = Fabricate(:account)
-      subject.visibility = :private
-
-      expect(subject.permitted?(viewer)).to be false
-    end
-
-    it 'returns true when no viewer' do
-      expect(subject.permitted?).to be true
-    end
-
-    it 'returns false when viewer is blocked' do
-      block = Fabricate(:block)
-      subject.visibility = :private
-      subject.account = block.target_account
-
-      expect(subject.permitted?(block.account)).to be false
-    end
-  end
-
   describe '#ancestors' do
     let!(:alice)  { Fabricate(:account, username: 'alice') }
     let!(:bob)    { Fabricate(:account, username: 'bob', domain: 'example.com') }
diff --git a/spec/policies/status_policy_spec.rb b/spec/policies/status_policy_spec.rb
new file mode 100644
index 0000000000..ee7060b989
--- /dev/null
+++ b/spec/policies/status_policy_spec.rb
@@ -0,0 +1,70 @@
+require 'rails_helper'
+require 'pundit/rspec'
+
+RSpec.describe StatusPolicy, type: :model do
+  subject { described_class }
+
+  let(:alice) { Fabricate(:account, username: 'alice') }
+  let(:status) { Fabricate(:status, account: alice) }
+
+  permissions :show? do
+    it 'grants access when direct and account is viewer' do
+      status.visibility = :direct
+      expect(subject).to permit(status.account, status)
+    end
+
+    it 'grants access when direct and viewer is mentioned' do
+      status.visibility = :direct
+      status.mentions = [Fabricate(:mention, account: alice)]
+
+      expect(subject).to permit(alice, status)
+    end
+
+    it 'denies access when direct and viewer is not mentioned' do
+      viewer = Fabricate(:account)
+      status.visibility = :direct
+
+      expect(subject).to_not permit(viewer, status)
+    end
+
+    it 'grants access when private and account is viewer' do
+      status.visibility = :direct
+
+      expect(subject).to permit(status.account, status)
+    end
+
+    it 'grants access when private and account is following viewer' do
+      follow = Fabricate(:follow)
+      status.visibility = :private
+      status.account = follow.target_account
+
+      expect(subject).to permit(follow.account, status)
+    end
+
+    it 'grants access when private and viewer is mentioned' do
+      status.visibility = :private
+      status.mentions = [Fabricate(:mention, account: alice)]
+
+      expect(subject).to permit(alice, status)
+    end
+
+    it 'denies access when private and viewer is not mentioned or followed' do
+      viewer = Fabricate(:account)
+      status.visibility = :private
+
+      expect(subject).to_not permit(viewer, status)
+    end
+
+    it 'grants access when no viewer' do
+      expect(subject).to permit(nil, status)
+    end
+
+    it 'denies access when viewer is blocked' do
+      block = Fabricate(:block)
+      status.visibility = :private
+      status.account = block.target_account
+
+      expect(subject).to_not permit(block.account, status)
+    end
+  end
+end