Fix an information disclosure when requesting access to a group containing private projects

The issue was with the `User#groups` and `User#projects` associations
which goes through the `User#group_members` and `User#project_members`.

Initially I chose to use a secure approach by storing the requester's
user ID in `Member#created_by_id` instead of `Member#user_id` because I
was aware that there was a security risk since I didn't know the
codebase well enough.

Then during the review, we decided to change that and directly store the
requester's user ID into `Member#user_id` (for the sake of simplifying
the code I believe), meaning that every `group_members` / `project_members`
association would include the requesters by default...

My bad for not checking that all the `group_members` / `project_members`
associations and the ones that go through them (e.g. `Group#users` and
`Project#users`) were made safe with the `where(requested_at: nil)` /
`where(members: { requested_at: nil })` scopes.

Now they are all secure.

Signed-off-by: Rémy Coutable <remy@rymai.me>

2 files changed, 35 insertions, 0 deletions

diff --git a/spec/features/groups/members/user_requests_access_spec.rb b/spec/features/groups/members/user_requests_access_spec.rb
index 1ea607cbca0..4944301c938 100644
--- a/spec/features/groups/members/user_requests_access_spec.rb
+++ b/spec/features/groups/members/user_requests_access_spec.rb
@@ -4,6 +4,7 @@ feature 'Groups > Members > User requests access', feature: true do
   let(:user) { create(:user) }
   let(:owner) { create(:user) }
   let(:group) { create(:group, :public) }
+  let!(:project) { create(:project, :private, namespace: group) }
 
   background do
     group.add_owner(owner)
@@ -24,6 +25,20 @@ feature 'Groups > Members > User requests access', feature: true do
     expect(page).not_to have_content 'Leave Group'
   end
 
+  scenario 'user does not see private projects' do
+    perform_enqueued_jobs { click_link 'Request Access' }
+
+    expect(page).not_to have_content project.name
+  end
+
+  scenario 'user does not see group in the Dashboard > Groups page' do
+    perform_enqueued_jobs { click_link 'Request Access' }
+
+    visit dashboard_groups_path
+
+    expect(page).not_to have_content group.name
+  end
+
   scenario 'user is not listed in the group members page' do
     click_link 'Request Access'
 
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 73bee535fe3..328254ed56b 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -31,6 +31,26 @@ describe User, models: true do
     it { is_expected.to have_many(:spam_logs).dependent(:destroy) }
     it { is_expected.to have_many(:todos).dependent(:destroy) }
     it { is_expected.to have_many(:award_emoji).dependent(:destroy) }
+
+    describe '#group_members' do
+      it 'does not include group memberships for which user is a requester' do
+        user = create(:user)
+        group = create(:group, :public)
+        group.request_access(user)
+
+        expect(user.group_members).to be_empty
+      end
+    end
+
+    describe '#project_members' do
+      it 'does not include project memberships for which user is a requester' do
+        user = create(:user)
+        project = create(:project, :public)
+        project.request_access(user)
+
+        expect(user.project_members).to be_empty
+      end
+    end
   end
 
   describe 'validations' do