Limit the number of tags associated with a CI runner

Merge branch 'pedropombeiro/328593/14.7-limit-number-of-runner-tags' into '14-7-stable-ee'

See merge request gitlab-org/security/gitlab!2305

Changelog: security

app/models/ci/runner.rb

@@ -65,6 +65,8 @@ module Ci
     FORM_EDITABLE = %i[description tag_list active run_untagged locked access_level maximum_timeout_human_readable].freeze
     MINUTES_COST_FACTOR_FIELDS = %i[public_projects_minutes_cost_factor private_projects_minutes_cost_factor].freeze
+    TAG_LIST_MAX_LENGTH = 50
+
     has_many :builds
     has_many :runner_projects, inverse_of: :runner, autosave: true, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
     has_many :projects, through: :runner_projects
@@ -508,6 +510,11 @@ module Ci
         errors.add(:tags_list,
           'can not be empty when runner is not allowed to pick untagged jobs')
       end
+
+      if tag_list_changed? && tag_list.count > TAG_LIST_MAX_LENGTH
+        errors.add(:tags_list,
+          "Too many tags specified. Please limit the number of tags to #{TAG_LIST_MAX_LENGTH}")
+      end
     end
     # TODO: remove this method once feature flag ci_runners_short_circuit_assignable_for

spec/models/ci/runner_spec.rb

@@ -29,15 +29,25 @@ RSpec.describe Ci::Runner do
     context 'when runner is not allowed to pick untagged jobs' do
       context 'when runner does not have tags' do
+        let(:runner) { build(:ci_runner, tag_list: [], run_untagged: false) }
+
+        it 'is not valid' do
+          expect(runner).to be_invalid
+        end
+      end
+
+      context 'when runner has too many tags' do
+        let(:runner) { build(:ci_runner, tag_list: (1..::Ci::Runner::TAG_LIST_MAX_LENGTH + 1).map { |i| "tag#{i}" }, run_untagged: false) }
+
         it 'is not valid' do
-          runner = build(:ci_runner, tag_list: [], run_untagged: false)
           expect(runner).to be_invalid
         end
       end
       context 'when runner has tags' do
+        let(:runner) { build(:ci_runner, tag_list: ['tag'], run_untagged: false) }
+
         it 'is valid' do
-          runner = build(:ci_runner, tag_list: ['tag'], run_untagged: false)
           expect(runner).to be_valid
         end
       end

spec/requests/api/ci/runner/runners_post_spec.rb

@@ -116,6 +116,54 @@ RSpec.describe API::Ci::Runner, :clean_gitlab_redis_shared_state do
           expect(response).to have_gitlab_http_status(:created)
           expect(::Ci::Runner.last.ip_address).to eq('123.111.123.111')
         end
+
+        context 'when tags parameter is provided' do
+          def request
+            post api('/runners'), params: {
+              token: registration_token,
+              tag_list: tag_list
+            }
+          end
+
+          context 'with number of tags above limit' do
+            let(:tag_list) { (1..::Ci::Runner::TAG_LIST_MAX_LENGTH + 1).map { |i| "tag#{i}" } }
+
+            it 'uses tag_list value in registration and returns error' do
+              expect_next_instance_of(::Ci::RegisterRunnerService) do |service|
+                expected_params = { tag_list: tag_list }.stringify_keys
+
+                expect(service).to receive(:execute)
+                  .once
+                  .with(registration_token, a_hash_including(expected_params))
+                  .and_call_original
+              end
+
+              request
+
+              expect(response).to have_gitlab_http_status(:bad_request)
+              expect(json_response.dig('message', 'tags_list')).to contain_exactly("Too many tags specified. Please limit the number of tags to #{::Ci::Runner::TAG_LIST_MAX_LENGTH}")
+            end
+          end
+
+          context 'with number of tags below limit' do
+            let(:tag_list) { (1..20).map { |i| "tag#{i}" } }
+
+            it 'uses tag_list value in registration and successfully creates runner' do
+              expect_next_instance_of(::Ci::RegisterRunnerService) do |service|
+                expected_params = { tag_list: tag_list }.stringify_keys
+
+                expect(service).to receive(:execute)
+                  .once
+                  .with(registration_token, a_hash_including(expected_params))
+                  .and_call_original
+              end
+
+              request
+
+              expect(response).to have_gitlab_http_status(:created)
+            end
+          end
+        end
       end
     end
   end

spec/requests/api/ci/runners_spec.rb

@@ -366,6 +366,19 @@ RSpec.describe API::Ci::Runners do
           expect(shared_runner.reload.tag_list).to include('ruby2.1', 'pgsql', 'mysql')
         end
+        it 'unrelated runner attribute on an existing runner with too many tags' do
+          # This test ensures that it is possible to update any attribute on a runner that currently fails the
+          # validation that ensures that there aren't too many tags associated with a runner
+          existing_invalid_shared_runner = build(:ci_runner, :instance, tag_list: (1..::Ci::Runner::TAG_LIST_MAX_LENGTH + 1).map { |i| "tag#{i}" } )
+          existing_invalid_shared_runner.save!(validate: false)
+
+          active = existing_invalid_shared_runner.active
+          update_runner(existing_invalid_shared_runner.id, admin, active: !active)
+
+          expect(response).to have_gitlab_http_status(:ok)
+          expect(existing_invalid_shared_runner.reload.active).to eq(!active)
+        end
+
         it 'runner untagged flag' do
           # Ensure tag list is non-empty before setting untagged to false.
           update_runner(shared_runner.id, admin, tag_list: ['ruby2.1', 'pgsql', 'mysql'])