Ensure private project snippets are not viewable by unauthorized people

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/14607.

app/controllers/projects/snippets_controller.rb

@@ -3,7 +3,7 @@ class Projects::SnippetsController < Projects::ApplicationController
   before_action :snippet, only: [:show, :edit, :destroy, :update, :raw]
 
   # Allow read any snippet
-  before_action :authorize_read_project_snippet!
+  before_action :authorize_read_project_snippet!, except: [:index]
 
   # Allow write(create) snippet
   before_action :authorize_create_project_snippet!, only: [:new, :create]
@@ -81,6 +81,10 @@ class Projects::SnippetsController < Projects::ApplicationController
     @snippet ||= @project.snippets.find(params[:id])
   end
 
+  def authorize_read_project_snippet!
+    return render_404 unless can?(current_user, :read_project_snippet, @snippet)
+  end
+
   def authorize_update_project_snippet!
     return render_404 unless can?(current_user, :update_project_snippet, @snippet)
   end

app/models/ability.rb

@@ -27,6 +27,8 @@ class Ability
       case true
       when subject.is_a?(PersonalSnippet)
         anonymous_personal_snippet_abilities(subject)
+      when subject.is_a?(ProjectSnippet)
+        anonymous_project_snippet_abilities(subject)
       when subject.is_a?(CommitStatus)
         anonymous_commit_status_abilities(subject)
       when subject.is_a?(Project) || subject.respond_to?(:project)
@@ -100,6 +102,14 @@ class Ability
       end
     end
 
+    def anonymous_project_snippet_abilities(snippet)
+      if snippet.public?
+        [:read_project_snippet]
+      else
+        []
+      end
+    end
+
     def global_abilities(user)
       rules = []
       rules << :create_group if user.can_create_group

spec/controllers/projects/snippets_controller_spec.rb

@@ -0,0 +1,107 @@
+require 'spec_helper'
+
+describe Projects::SnippetsController do
+  let(:project) { create(:project_empty_repo, :public, snippets_enabled: true) }
+  let(:user)    { create(:user) }
+  let(:user2)   { create(:user) }
+
+  before do
+    project.team << [user, :master]
+    project.team << [user2, :master]
+  end
+
+  describe 'GET #index' do
+    context 'when the project snippet is private' do
+      let!(:project_snippet) { create(:project_snippet, :private, project: project, author: user) }
+
+      context 'when anonymous' do
+        it 'does not include the private snippet' do
+          get :index, namespace_id: project.namespace.path, project_id: project.path
+
+          expect(assigns(:snippets)).not_to include(project_snippet)
+          expect(response.status).to eq(200)
+        end
+      end
+
+      context 'when signed in as the author' do
+        before { sign_in(user) }
+
+        it 'renders the snippet' do
+          get :index, namespace_id: project.namespace.path, project_id: project.path
+
+          expect(assigns(:snippets)).to include(project_snippet)
+          expect(response.status).to eq(200)
+        end
+      end
+
+      context 'when signed in as a project member' do
+        before { sign_in(user2) }
+
+        it 'renders the snippet' do
+          get :index, namespace_id: project.namespace.path, project_id: project.path
+
+          expect(assigns(:snippets)).to include(project_snippet)
+          expect(response.status).to eq(200)
+        end
+      end
+    end
+  end
+
+  %w[show raw].each do |action|
+    describe "GET ##{action}" do
+      context 'when the project snippet is private' do
+        let(:project_snippet) { create(:project_snippet, :private, project: project, author: user) }
+
+        context 'when anonymous' do
+          it 'responds with status 404' do
+            get action, namespace_id: project.namespace.path, project_id: project.path, id: project_snippet.to_param
+
+            expect(response.status).to eq(404)
+          end
+        end
+
+        context 'when signed in as the author' do
+          before { sign_in(user) }
+
+          it 'renders the snippet' do
+            get action, namespace_id: project.namespace.path, project_id: project.path, id: project_snippet.to_param
+
+            expect(assigns(:snippet)).to eq(project_snippet)
+            expect(response.status).to eq(200)
+          end
+        end
+
+        context 'when signed in as a project member' do
+          before { sign_in(user2) }
+
+          it 'renders the snippet' do
+            get action, namespace_id: project.namespace.path, project_id: project.path, id: project_snippet.to_param
+
+            expect(assigns(:snippet)).to eq(project_snippet)
+            expect(response.status).to eq(200)
+          end
+        end
+      end
+
+      context 'when the project snippet does not exist' do
+        context 'when anonymous' do
+          it 'responds with status 404' do
+            get action, namespace_id: project.namespace.path, project_id: project.path, id: 42
+
+            expect(response.status).to eq(404)
+          end
+        end
+
+        context 'when signed in' do
+          before { sign_in(user) }
+
+          it 'responds with status 404' do
+            get action, namespace_id: project.namespace.path, project_id: project.path, id: 42
+
+            expect(response.status).to eq(404)
+          end
+        end
+      end
+    end
+  end
+end