Expose PipelineBasic if user can read pipeline

expose last_pipeline entry in commit details only if the
current_user can read pipelines.

changelogs/unreleased/security-commits-api-last-pipeline-status.yml

+---
+title: Disable access to last_pipeline in commits API for users without read permissions
+merge_request:
+author:
+type: security

lib/api/commits.rb

@@ -154,7 +154,7 @@ module API
 
         not_found! 'Commit' unless commit
 
-        present commit, with: Entities::CommitDetail, stats: params[:stats]
+        present commit, with: Entities::CommitDetail, stats: params[:stats], current_user: current_user
       end
 
       desc 'Get the diff for a specific commit of a project' do

lib/api/entities.rb

@@ -491,8 +491,18 @@ module API
     class CommitDetail < Commit
       expose :stats, using: Entities::CommitStats, if: :stats
       expose :status
-      expose :last_pipeline, using: 'API::Entities::PipelineBasic'
       expose :project_id
+
+      expose :last_pipeline do |commit, options|
+        pipeline = commit.last_pipeline if can_read_pipeline?
+        ::API::Entities::PipelineBasic.represent(pipeline, options)
+      end
+
+      private
+
+      def can_read_pipeline?
+        Ability.allowed?(options[:current_user], :read_pipeline, object.last_pipeline)
+      end
     end
 
     class CommitSignature < Grape::Entity

spec/requests/api/commits_spec.rb

@@ -8,6 +8,7 @@ describe API::Commits do
 
   let(:user) { create(:user) }
   let(:guest) { create(:user).tap { |u| project.add_guest(u) } }
+  let(:developer) { create(:user).tap { |u| project.add_developer(u) } }
   let(:project) { create(:project, :repository, creator: user, path: 'my.project') }
   let(:branch_with_dot) { project.repository.find_branch('ends-with.json') }
   let(:branch_with_slash) { project.repository.find_branch('improve/awesome') }
@@ -964,6 +965,56 @@ describe API::Commits do
       end
     end
 
+    shared_examples_for 'ref with pipeline' do
+      let!(:pipeline) do
+        project
+          .ci_pipelines
+          .create!(source: :push, ref: 'master', sha: commit.sha, protected: false)
+      end
+
+      it 'includes status as "created" and a last_pipeline object' do
+        get api(route, current_user)
+
+        expect(response).to have_gitlab_http_status(200)
+        expect(response).to match_response_schema('public_api/v4/commit/detail')
+        expect(json_response['status']).to eq('created')
+        expect(json_response['last_pipeline']['id']).to eq(pipeline.id)
+        expect(json_response['last_pipeline']['ref']).to eq(pipeline.ref)
+        expect(json_response['last_pipeline']['sha']).to eq(pipeline.sha)
+        expect(json_response['last_pipeline']['status']).to eq(pipeline.status)
+      end
+
+      context 'when pipeline succeeds' do
+        before do
+          pipeline.update!(status: 'success')
+        end
+
+        it 'includes a "success" status' do
+          get api(route, current_user)
+
+          expect(response).to have_gitlab_http_status(200)
+          expect(response).to match_response_schema('public_api/v4/commit/detail')
+          expect(json_response['status']).to eq('success')
+        end
+      end
+    end
+
+    shared_examples_for 'ref with unaccessible pipeline' do
+      let!(:pipeline) do
+        project
+          .ci_pipelines
+          .create!(source: :push, ref: 'master', sha: commit.sha, protected: false)
+      end
+
+      it 'does not include last_pipeline' do
+        get api(route, current_user)
+
+        expect(response).to match_response_schema('public_api/v4/commit/detail')
+        expect(response).to have_gitlab_http_status(200)
+        expect(json_response['last_pipeline']).to be_nil
+      end
+    end
+
     context 'when stat param' do
       let(:route) { "/projects/#{project_id}/repository/commits/#{commit_id}" }
 
@@ -993,6 +1044,15 @@ describe API::Commits do
       let(:project) { create(:project, :public, :repository) }
 
       it_behaves_like 'ref commit'
+      it_behaves_like 'ref with pipeline'
+
+      context 'with private builds' do
+        before do
+          project.project_feature.update!(builds_access_level: ProjectFeature::PRIVATE)
+        end
+
+        it_behaves_like 'ref with unaccessible pipeline'
+      end
     end
 
     context 'when unauthenticated', 'and project is private' do
@@ -1006,6 +1066,17 @@ describe API::Commits do
       let(:current_user) { user }
 
       it_behaves_like 'ref commit'
+      it_behaves_like 'ref with pipeline'
+
+      context 'when builds are disabled' do
+        before do
+          project
+            .project_feature
+            .update!(builds_access_level: ProjectFeature::DISABLED)
+        end
+
+        it_behaves_like 'ref with unaccessible pipeline'
+      end
 
       context 'when branch contains a dot' do
         let(:commit) { project.repository.commit(branch_with_dot.name) }
@@ -1041,35 +1112,53 @@ describe API::Commits do
           it_behaves_like 'ref commit'
         end
       end
+    end
 
-      context 'when the ref has a pipeline' do
-        let!(:pipeline) { project.ci_pipelines.create(source: :push, ref: 'master', sha: commit.sha, protected: false) }
+    context 'when authenticated', 'as a developer' do
+      let(:current_user) { developer }
 
-        it 'includes a "created" status' do
-          get api(route, current_user)
+      it_behaves_like 'ref commit'
+      it_behaves_like 'ref with pipeline'
 
-          expect(response).to have_gitlab_http_status(200)
-          expect(response).to match_response_schema('public_api/v4/commit/detail')
-          expect(json_response['status']).to eq('created')
-          expect(json_response['last_pipeline']['id']).to eq(pipeline.id)
-          expect(json_response['last_pipeline']['ref']).to eq(pipeline.ref)
-          expect(json_response['last_pipeline']['sha']).to eq(pipeline.sha)
-          expect(json_response['last_pipeline']['status']).to eq(pipeline.status)
+      context 'with private builds' do
+        before do
+          project.project_feature.update!(builds_access_level: ProjectFeature::PRIVATE)
         end
 
-        context 'when pipeline succeeds' do
-          before do
-            pipeline.update(status: 'success')
+        it_behaves_like 'ref with pipeline'
+      end
     end
 
-          it 'includes a "success" status' do
-            get api(route, current_user)
+    context 'when authenticated', 'as a guest' do
+      let(:current_user) { guest }
 
-            expect(response).to have_gitlab_http_status(200)
-            expect(response).to match_response_schema('public_api/v4/commit/detail')
-            expect(json_response['status']).to eq('success')
+      it_behaves_like '403 response' do
+        let(:request) { get api(route, guest) }
+        let(:message) { '403 Forbidden' }
+      end
+    end
+
+    context 'when authenticated', 'as a non member' do
+      let(:current_user) { create(:user) }
+
+      it_behaves_like '403 response' do
+        let(:request) { get api(route, guest) }
+        let(:message) { '403 Forbidden' }
       end
     end
+
+    context 'when authenticated', 'as non_member and project is public' do
+      let(:current_user) { create(:user) }
+      let(:project) { create(:project, :public, :repository) }
+
+      it_behaves_like 'ref with pipeline'
+
+      context 'with private builds' do
+        before do
+          project.project_feature.update!(builds_access_level: ProjectFeature::PRIVATE)
+        end
+
+        it_behaves_like 'ref with unaccessible pipeline'
       end
     end
   end