Filter system notes with public and private cross references

app/models/note.rb

@@ -38,10 +38,12 @@ class Note < ActiveRecord::Base
   alias_attribute :last_edited_at, :updated_at
   alias_attribute :last_edited_by, :updated_by
 
-  # Attribute containing rendered and redacted Markdown as generated by
-  # Banzai::ObjectRenderer.
+  # Number of user visible references as generated by Banzai::ObjectRenderer
   attr_accessor :redacted_note_html
 
+  # Total of all references as generated by Banzai::ObjectRenderer
+  attr_accessor :total_reference_count
+
   # An Array containing the number of visible references as generated by
   # Banzai::ObjectRenderer
   attr_accessor :user_visible_reference_count
@@ -288,15 +290,7 @@ class Note < ActiveRecord::Base
   end
 
   def cross_reference_not_visible_for?(user)
-    cross_reference? && !has_referenced_mentionables?(user)
-  end
-
-  def has_referenced_mentionables?(user)
-    if user_visible_reference_count.present?
-      user_visible_reference_count > 0
-    else
-      referenced_mentionables(user).any?
-    end
+    cross_reference? && !all_referenced_mentionables_allowed?(user)
   end
 
   def award_emoji?
@@ -466,9 +460,18 @@ class Note < ActiveRecord::Base
     self.discussion_id ||= discussion_class.discussion_id(self)
   end
 
+  def all_referenced_mentionables_allowed?(user)
+    if user_visible_reference_count.present? && total_reference_count.present?
+      # if they are not equal, then there are private/confidential references as well
+      user_visible_reference_count > 0 && user_visible_reference_count == total_reference_count
+    else
+      referenced_mentionables(user).any?
+    end
+  end
+
   def force_cross_reference_regex_check?
     return unless system?
 
-    SystemNoteMetadata::TYPES_WITH_CROSS_REFERENCES.include?(system_note_metadata&.action)
+    system_note_metadata&.cross_reference_types&.include?(system_note_metadata&.action)
   end
 end

app/models/system_note_metadata.rb

@@ -9,6 +9,7 @@ class SystemNoteMetadata < ActiveRecord::Base
   TYPES_WITH_CROSS_REFERENCES = %w[
     commit cross_reference
     close duplicate
+    moved
   ].freeze
 
   ICON_TYPES = %w[
@@ -26,4 +27,8 @@ class SystemNoteMetadata < ActiveRecord::Base
   def icon_types
     ICON_TYPES
   end
+
+  def cross_reference_types
+    TYPES_WITH_CROSS_REFERENCES
+  end
 end

changelogs/unreleased/security-fix-leaking-private-project-namespace.yml

+---
+title: Properly filter private references from system notes
+merge_request:
+author:
+type: security

lib/banzai/object_renderer.rb

@@ -38,6 +38,7 @@ module Banzai
         redacted_data = redacted[index]
         object.__send__("redacted_#{attribute}_html=", redacted_data[:document].to_html(save_options).html_safe) # rubocop:disable GitlabSecurity/PublicSend
         object.user_visible_reference_count = redacted_data[:visible_reference_count] if object.respond_to?(:user_visible_reference_count)
+        object.total_reference_count = redacted_data[:total_reference_count] if object.respond_to?(:total_reference_count)
       end
     end
 

lib/banzai/redactor.rb

@@ -37,7 +37,13 @@ module Banzai
 
       all_document_nodes.each do |entry|
         nodes_for_document = entry[:nodes]
-        doc_data = { document: entry[:document], visible_reference_count: nodes_for_document.count }
+
+        doc_data = {
+          document:                entry[:document],
+          total_reference_count:   nodes_for_document.count,
+          visible_reference_count: nodes_for_document.count
+        }
+
         metadata << doc_data
 
         nodes_for_document.each do |node|

spec/models/note_spec.rb

@@ -231,13 +231,7 @@ describe Note do
     let(:ext_proj)  { create(:project, :public) }
     let(:ext_issue) { create(:issue, project: ext_proj) }
 
-    let(:note) do
-      create :note,
-        noteable: ext_issue, project: ext_proj,
-        note: "mentioned in issue #{private_issue.to_reference(ext_proj)}",
-        system: true
-    end
-
+    shared_examples "checks references" do
       it "returns true" do
         expect(note.cross_reference_not_visible_for?(ext_issue.author)).to be_truthy
       end
@@ -248,6 +242,7 @@ describe Note do
 
       it "returns false if user visible reference count set" do
         note.user_visible_reference_count = 1
+        note.total_reference_count = 1
 
         expect(note).not_to receive(:reference_mentionables)
         expect(note.cross_reference_not_visible_for?(ext_issue.author)).to be_falsy
@@ -261,6 +256,38 @@ describe Note do
       end
     end
 
+    context "when there is one reference in note" do
+      let(:note) do
+        create :note,
+          noteable: ext_issue, project: ext_proj,
+          note: "mentioned in issue #{private_issue.to_reference(ext_proj)}",
+          system: true
+      end
+
+      it_behaves_like "checks references"
+    end
+
+    context "when there are two references in note" do
+      let(:note) do
+        create :note,
+          noteable: ext_issue, project: ext_proj,
+          note: "mentioned in issue #{private_issue.to_reference(ext_proj)} and " \
+                "public issue #{ext_issue.to_reference(ext_proj)}",
+          system: true
+      end
+
+      it_behaves_like "checks references"
+
+      it "returns true if user visible reference count set and there is a private reference" do
+        note.user_visible_reference_count = 1
+        note.total_reference_count = 2
+
+        expect(note).not_to receive(:reference_mentionables)
+        expect(note.cross_reference_not_visible_for?(ext_issue.author)).to be_truthy
+      end
+    end
+  end
+
   describe '#cross_reference?' do
     it 'falsey for user-generated notes' do
       note = create(:note, system: false)
@@ -269,7 +296,7 @@ describe Note do
     end
 
     context 'when the note might contain cross references' do
-      SystemNoteMetadata::TYPES_WITH_CROSS_REFERENCES.each do |type|
+      SystemNoteMetadata.new.cross_reference_types.each do |type|
         let(:note) { create(:note, :system) }
         let!(:metadata) { create(:system_note_metadata, note: note, action: type) }