Merge branch 'fix/private-labels-permissions' into 'master'

Fix vulnerability that leaks private labels and milestones

## Summary

This fixes vulnerability that leaks information about private labels and milestones because of  insecure direct object reference in issueable create service.
This affects merge requests and issues.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/15439

## Fix

This MR introduces additional check that rejects labels and milestone that does not belong to the same project issue/merg request does.

## Further work

`IssuableBaseService` may benefit from encapsulating filters in separate class/module, which then may improve coherency in this class.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15439

See merge request !1954

6 files changed, 93 insertions, 23 deletions

diff --git a/CHANGELOG b/CHANGELOG
index ab8b86ba928..e7428834c1b 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -4,6 +4,7 @@ v 8.8.0 (unreleased)
 
 v 8.7.0 (unreleased)
   - Gitlab::GitAccess and Gitlab::GitAccessWiki are now instrumented
+  - Fix vulnerability that made it possible to gain access to private labels and milestones
   - The number of InfluxDB points stored per UDP packet can now be configured
   - Fix error when cross-project label reference used with non-existent project
   - Transactions for /internal/allowed now have an "action" tag set
diff --git a/app/services/issuable_base_service.rb b/app/services/issuable_base_service.rb
index 18f76d3f650..2b16089df1b 100644
--- a/app/services/issuable_base_service.rb
+++ b/app/services/issuable_base_service.rb
@@ -37,8 +37,9 @@ class IssuableBaseService < BaseService
   end
 
   def filter_params(issuable_ability_name = :issue)
-    params[:assignee_id]  = "" if params[:assignee_id] == IssuableFinder::NONE
-    params[:milestone_id] = "" if params[:milestone_id] == IssuableFinder::NONE
+    filter_assignee
+    filter_milestone
+    filter_labels
 
     ability = :"admin_#{issuable_ability_name}"
 
@@ -49,6 +50,29 @@ class IssuableBaseService < BaseService
     end
   end
 
+  def filter_assignee
+    if params[:assignee_id] == IssuableFinder::NONE
+      params[:assignee_id] = ''
+    end
+  end
+
+  def filter_milestone
+    milestone_id = params[:milestone_id]
+    return unless milestone_id
+
+    if milestone_id == IssuableFinder::NONE ||
+        project.milestones.find_by(id: milestone_id).nil?
+      params[:milestone_id] = ''
+    end
+  end
+
+  def filter_labels
+    return if params[:label_ids].to_a.empty?
+
+    params[:label_ids] =
+      project.labels.where(id: params[:label_ids]).pluck(:id)
+  end
+
   def update(issuable)
     change_state(issuable)
     filter_params
diff --git a/spec/services/issues/bulk_update_service_spec.rb b/spec/services/issues/bulk_update_service_spec.rb
index 6a7ea4b2f44..e91906d0d49 100644
--- a/spec/services/issues/bulk_update_service_spec.rb
+++ b/spec/services/issues/bulk_update_service_spec.rb
@@ -100,7 +100,7 @@ describe Issues::BulkUpdateService, services: true do
   describe :update_milestone do
 
     before do
-      @milestone = create :milestone
+      @milestone = create(:milestone, project: @project)
       @params = {
         issues_ids: [issue.id],
         milestone_id: @milestone.id
diff --git a/spec/services/issues/create_service_spec.rb b/spec/services/issues/create_service_spec.rb
index 5e7915db7e1..ac28b6f71f9 100644
--- a/spec/services/issues/create_service_spec.rb
+++ b/spec/services/issues/create_service_spec.rb
@@ -3,40 +3,75 @@ require 'spec_helper'
 describe Issues::CreateService, services: true do
   let(:project) { create(:empty_project) }
   let(:user) { create(:user) }
-  let(:assignee) { create(:user) }
 
-  describe :execute do
-    context 'valid params' do
+  describe '#execute' do
+    let(:issue) { described_class.new(project, user, opts).execute }
+
+    context 'when params are valid' do
+      let(:assignee) { create(:user) }
+      let(:milestone) { create(:milestone, project: project) }
+      let(:labels) { create_pair(:label, project: project) }
+
       before do
         project.team << [user, :master]
         project.team << [assignee, :master]
+      end
 
-        opts = {
-          title: 'Awesome issue',
+      let(:opts) do
+        { title: 'Awesome issue',
           description: 'please fix',
-          assignee: assignee
-        }
-
-        @issue = Issues::CreateService.new(project, user, opts).execute
+          assignee: assignee,
+          label_ids: labels.map(&:id),
+          milestone_id: milestone.id }
       end
 
-      it { expect(@issue).to be_valid }
-      it { expect(@issue.title).to eq('Awesome issue') }
-      it { expect(@issue.assignee).to eq assignee }
+      it { expect(issue).to be_valid }
+      it { expect(issue.title).to eq('Awesome issue') }
+      it { expect(issue.assignee).to eq assignee }
+      it { expect(issue.labels).to match_array labels }
+      it { expect(issue.milestone).to eq milestone }
 
       it 'creates a pending todo for new assignee' do
         attributes = {
           project: project,
           author: user,
           user: assignee,
-          target_id: @issue.id,
-          target_type: @issue.class.name,
+          target_id: issue.id,
+          target_type: issue.class.name,
           action: Todo::ASSIGNED,
           state: :pending
         }
 
         expect(Todo.where(attributes).count).to eq 1
       end
+
+      context 'when label belongs to different project' do
+        let(:label) { create(:label) }
+
+        let(:opts) do
+          { title: 'Title',
+            description: 'Description',
+            label_ids: [label.id] }
+        end
+
+        it 'does not assign label'do
+          expect(issue.labels).to_not include label
+        end
+      end
+
+      context 'when milestone belongs to different project' do
+        let(:milestone) { create(:milestone) }
+
+        let(:opts) do
+          { title: 'Title',
+            description: 'Description',
+            milestone_id: milestone.id }
+        end
+
+        it 'does not assign milestone' do
+          expect(issue.milestone).to_not eq milestone
+        end
+      end
     end
   end
 end
diff --git a/spec/services/issues/update_service_spec.rb b/spec/services/issues/update_service_spec.rb
index 6b214a0d96b..52f69306994 100644
--- a/spec/services/issues/update_service_spec.rb
+++ b/spec/services/issues/update_service_spec.rb
@@ -4,10 +4,15 @@ describe Issues::UpdateService, services: true do
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
   let(:user3) { create(:user) }
-  let(:issue) { create(:issue, title: 'Old title', assignee_id: user3.id) }
-  let(:label) { create(:label) }
+  let(:project) { create(:empty_project) }
+  let(:label) { create(:label, project: project) }
   let(:label2) { create(:label) }
-  let(:project) { issue.project }
+
+  let(:issue) do
+    create(:issue, title: 'Old title',
+                   assignee_id: user3.id,
+                   project: project)
+  end
 
   before do
     project.team << [user, :master]
diff --git a/spec/services/merge_requests/update_service_spec.rb b/spec/services/merge_requests/update_service_spec.rb
index cb8cff2fa8c..213e8c2eb3a 100644
--- a/spec/services/merge_requests/update_service_spec.rb
+++ b/spec/services/merge_requests/update_service_spec.rb
@@ -1,14 +1,19 @@
 require 'spec_helper'
 
 describe MergeRequests::UpdateService, services: true do
+  let(:project) { create(:project) }
   let(:user) { create(:user) }
   let(:user2) { create(:user) }
   let(:user3) { create(:user) }
-  let(:merge_request) { create(:merge_request, :simple, title: 'Old title', assignee_id: user3.id) }
-  let(:project) { merge_request.project }
-  let(:label) { create(:label) }
+  let(:label) { create(:label, project: project) }
   let(:label2) { create(:label) }
 
+  let(:merge_request) do
+    create(:merge_request, :simple, title: 'Old title',
+                                    assignee_id: user3.id,
+                                    source_project: project)
+  end
+
   before do
     project.team << [user, :master]
     project.team << [user2, :developer]