Fix labels finder to filter visible issuables

Use project scopes to filter project labels

Add changelog file

Check  issuables visibility in  LabelsFinder

Add specs for issuables visibility cases

Rename Project method to reuse in LabelsFinder

Remove commented code

Improve changelog title

app/finders/labels_finder.rb

@@ -51,7 +51,7 @@ class LabelsFinder < UnionFinder
       end
 
       label_ids << Label.where(group_id: projects.group_ids)
-      label_ids << Label.where(project_id: projects.select(:id)) unless only_group_labels?
+      label_ids << Label.where(project_id: ids_user_can_read_labels(projects)) unless only_group_labels?
     end
 
     label_ids
@@ -188,4 +188,10 @@ class LabelsFinder < UnionFinder
       groups.select { |group| authorized_to_read_labels?(group) }
     end
   end
+
+  # rubocop: disable CodeReuse/ActiveRecord
+  def ids_user_can_read_labels(projects)
+    Project.where(id: projects.select(:id)).ids_with_issuables_available_for(current_user)
+  end
+  # rubocop: enable CodeReuse/ActiveRecord
 end

app/models/project.rb

@@ -609,11 +609,11 @@ class Project < ApplicationRecord
       joins(:namespace).where(namespaces: { type: 'Group' }).select(:namespace_id)
     end
 
-    # Returns ids of projects with milestones available for given user
+    # Returns ids of projects with issuables available for given user
     #
-    # Used on queries to find milestones which user can see
-    # For example: Milestone.where(project_id: ids_with_milestone_available_for(user))
-    def ids_with_milestone_available_for(user)
+    # Used on queries to find milestones or labels which user can see
+    # For example: Milestone.where(project_id: ids_with_issuables_available_for(user))
+    def ids_with_issuables_available_for(user)
       with_issues_enabled = with_issues_available_for_user(user).select(:id)
       with_merge_requests_enabled = with_merge_requests_available_for_user(user).select(:id)
 

changelogs/unreleased/security-2914-labels-visible-despite-no-access-to-issues-repositories.yml

+---
+title: Do not display project labels that are not visible for user accessing group labels
+merge_request:
+author:
+type: security

lib/gitlab/search_results.rb

@@ -163,7 +163,7 @@ module Gitlab
       return Milestone.none if project_ids.nil?
 
       authorized_project_ids_relation =
-        Project.where(id: project_ids).ids_with_milestone_available_for(current_user)
+        Project.where(id: project_ids).ids_with_issuables_available_for(current_user)
 
       milestones.where(project_id: authorized_project_ids_relation)
     end

spec/finders/labels_finder_spec.rb

@@ -128,6 +128,89 @@ describe LabelsFinder do
           expect(finder.execute).to eq [private_subgroup_label_1]
         end
       end
+
+      context 'when including labels from group projects with limited visibility' do
+        let(:finder)                     { described_class.new(user, group_id: group_4.id) }
+        let(:group_4)                    { create(:group) }
+        let(:limited_visibility_project) { create(:project, :public, group: group_4) }
+        let(:visible_project)            { create(:project, :public, group: group_4) }
+        let!(:group_label_1)             { create(:group_label, group: group_4) }
+        let!(:limited_visibility_label)  { create(:label, project: limited_visibility_project) }
+        let!(:visible_label)             { create(:label, project: visible_project) }
+
+        shared_examples 'with full visibility' do
+          it 'returns all projects labels' do
+            expect(finder.execute).to eq [group_label_1, limited_visibility_label, visible_label]
+          end
+        end
+
+        shared_examples 'with limited visibility' do
+          it 'returns only authorized projects labels' do
+            expect(finder.execute).to eq [group_label_1, visible_label]
+          end
+        end
+
+        context 'when merge requests and issues are not visible for non members' do
+          before do
+            limited_visibility_project.project_feature.update!(
+              merge_requests_access_level: ProjectFeature::PRIVATE,
+              issues_access_level: ProjectFeature::PRIVATE
+            )
+          end
+
+          context 'when user is not a group member' do
+            it_behaves_like 'with limited visibility'
+          end
+
+          context 'when user is a group member' do
+            before do
+              group_4.add_developer(user)
+            end
+
+            it_behaves_like 'with full visibility'
+          end
+        end
+
+        context 'when merge requests are not visible for non members' do
+          before do
+            limited_visibility_project.project_feature.update!(
+              merge_requests_access_level: ProjectFeature::PRIVATE
+            )
+          end
+
+          context 'when user is not a group member' do
+            it_behaves_like 'with full visibility'
+          end
+
+          context 'when user is a group member' do
+            before do
+              group_4.add_developer(user)
+            end
+
+            it_behaves_like 'with full visibility'
+          end
+        end
+
+        context 'when issues are not visible for non members' do
+          before do
+            limited_visibility_project.project_feature.update!(
+              issues_access_level: ProjectFeature::PRIVATE
+            )
+          end
+
+          context 'when user is not a group member' do
+            it_behaves_like 'with full visibility'
+          end
+
+          context 'when user is a group member' do
+            before do
+              group_4.add_developer(user)
+            end
+
+            it_behaves_like 'with full visibility'
+          end
+        end
+      end
     end
 
     context 'filtering by project_id' do

spec/models/project_spec.rb

@@ -3416,7 +3416,7 @@ describe Project do
     end
   end
 
-  describe '.ids_with_milestone_available_for' do
+  describe '.ids_with_issuables_available_for' do
     let!(:user) { create(:user) }
 
     it 'returns project ids with milestones available for user' do
@@ -3426,7 +3426,7 @@ describe Project do
       project_4 = create(:project, :public)
       project_4.project_feature.update(issues_access_level: ProjectFeature::PRIVATE, merge_requests_access_level: ProjectFeature::PRIVATE )
 
-      project_ids = described_class.ids_with_milestone_available_for(user).pluck(:id)
+      project_ids = described_class.ids_with_issuables_available_for(user).pluck(:id)
 
       expect(project_ids).to include(project_2.id, project_3.id)
       expect(project_ids).not_to include(project_1.id, project_4.id)