Enforce the fork_project permission in Projects::CreateService

Projects::ForkService delegates to this service almost entirely, but needed
one small change so it would propagate create errors correctly.

CreateService#execute needs significant refactoring; it is now right at the
complexity limit set by Rubocop. I avoided doing so in this commit to keep the
diff as small as possible.

Several tests depend on the insecure behaviour of ForkService, so fi them up at
the same time.

app/services/projects/create_service.rb

@@ -15,6 +15,11 @@ module Projects
         return @project
       end
+      unless allowed_fork?(forked_from_project_id)
+        @project.errors.add(:forked_from_project_id, 'is forbidden')
+        return @project
+      end
+
       # Set project name from path
       if @project.name.present? && @project.path.present?
         # if both name and path set - everything is ok
@@ -71,6 +76,13 @@ module Projects
       @project.errors.add(:namespace, "is not valid")
     end
+    def allowed_fork?(source_project_id)
+      return true if source_project_id.nil?
+
+      source_project = Project.find_by(id: source_project_id)
+      current_user.can?(:fork_project, source_project)
+    end
+
     def allowed_namespace?(user, namespace_id)
       namespace = Namespace.find_by(id: namespace_id)
       current_user.can?(:create_projects, namespace)

app/services/projects/fork_service.rb

@@ -16,6 +16,8 @@ module Projects
       end
       new_project = CreateService.new(current_user, new_params).execute
+      return new_project unless new_project.persisted?
+
       builds_access_level = @project.project_feature.builds_access_level
       new_project.project_feature.update_attributes(builds_access_level: builds_access_level)

features/steps/project/fork.rb

@@ -70,6 +70,7 @@ class Spinach::Features::ProjectFork < Spinach::FeatureSteps
   step 'There is an existent fork of the "Shop" project' do
     user = create(:user, name: 'Mike')
+    @project.team << [user, :reporter]
     @forked_project = Projects::ForkService.new(@project, user).execute
   end

spec/controllers/users_controller_spec.rb

@@ -73,8 +73,8 @@ describe UsersController do
     end
     context 'forked project' do
-      let!(:project) { create(:project) }
-      let!(:forked_project) { Projects::ForkService.new(project, user).execute }
+      let(:project) { create(:project) }
+      let(:forked_project) { Projects::ForkService.new(project, user).execute }
       before do
         sign_in(user)

spec/helpers/projects_helper_spec.rb

@@ -11,7 +11,7 @@ describe ProjectsHelper do
   describe "can_change_visibility_level?" do
     let(:project) { create(:project) }
-    let(:user) { create(:user) }
+    let(:user) { create(:project_member, :reporter, user: create(:user), project: project).user }
     let(:fork_project) { Projects::ForkService.new(project, user).execute }
     it "returns false if there are no appropriate permissions" do

spec/models/forked_project_link_spec.rb

@@ -6,6 +6,7 @@ describe ForkedProjectLink, "add link on fork" do
   let(:user) { create(:user, namespace: namespace) }
   before do
+    create(:project_member, :reporter, user: user, project: project_from)
     @project_to = fork_project(project_from, user)
   end

spec/requests/api/fork_spec.rb

@@ -18,7 +18,7 @@ describe API::API, api: true  do
   end
   let(:project_user2) do
-    create(:project_member, :guest, user: user2, project: project)
+    create(:project_member, :reporter, user: user2, project: project)
   end
   describe 'POST /projects/fork/:id' do

spec/services/projects/fork_service_spec.rb

@@ -12,12 +12,26 @@ describe Projects::ForkService, services: true do
                              description: 'wow such project')
       @to_namespace = create(:namespace)
       @to_user = create(:user, namespace: @to_namespace)
+      @from_project.add_user(@to_user, :developer)
     end
     context 'fork project' do
+      context 'when forker is a guest' do
+        before do
+          @guest = create(:user)
+          @from_project.add_user(@guest, :guest)
+        end
+        subject { fork_project(@from_project, @guest) }
+
+        it { is_expected.not_to be_persisted }
+        it { expect(subject.errors[:forked_from_project_id]).to eq(['is forbidden']) }
+      end
+
       describe "successfully creates project in the user namespace" do
         let(:to_project) { fork_project(@from_project, @to_user) }
+        it { expect(to_project).to be_persisted }
+        it { expect(to_project.errors).to be_empty }
         it { expect(to_project.owner).to eq(@to_user) }
         it { expect(to_project.namespace).to eq(@to_user.namespace) }
         it { expect(to_project.star_count).to be_zero }
@@ -29,7 +43,9 @@ describe Projects::ForkService, services: true do
       it "fails due to validation, not transaction failure" do
         @existing_project = create(:project, creator_id: @to_user.id, name: @from_project.name, namespace: @to_namespace)
         @to_project = fork_project(@from_project, @to_user)
-        expect(@existing_project.persisted?).to be_truthy
+        expect(@existing_project).to be_persisted
+
+        expect(@to_project).not_to be_persisted
         expect(@to_project.errors[:name]).to eq(['has already been taken'])
         expect(@to_project.errors[:path]).to eq(['has already been taken'])
       end
@@ -81,18 +97,23 @@ describe Projects::ForkService, services: true do
       @group = create(:group)
       @group.add_user(@group_owner, GroupMember::OWNER)
       @group.add_user(@developer,   GroupMember::DEVELOPER)
+      @project.add_user(@developer,   :developer)
+      @project.add_user(@group_owner, :developer)
       @opts = { namespace: @group }
     end
     context 'fork project for group' do
       it 'group owner successfully forks project into the group' do
         to_project = fork_project(@project, @group_owner, @opts)
+
+        expect(to_project).to             be_persisted
+        expect(to_project.errors).to      be_empty
         expect(to_project.owner).to       eq(@group)
         expect(to_project.namespace).to   eq(@group)
         expect(to_project.name).to        eq(@project.name)
         expect(to_project.path).to        eq(@project.path)
         expect(to_project.description).to eq(@project.description)
-        expect(to_project.star_count).to     be_zero
+        expect(to_project.star_count).to  be_zero
       end
     end

spec/services/system_note_service_spec.rb

@@ -445,7 +445,7 @@ describe SystemNoteService, services: true do
     end
     context 'commit with cross-reference from fork' do
-      let(:author2) { create(:user) }
+      let(:author2) { create(:project_member, :reporter, user: create(:user), project: project).user }
       let(:forked_project) { Projects::ForkService.new(project, author2).execute }
       let(:commit2) { forked_project.commit }