Redact unsubscribe links in issuable texts

It's possible that user pastes accidentally also unsubscribe link
which is included in footer of notification emails. This unsubscribe
link contains personal token which attacker then use to act as the
original user (e.g. for sending comments under his/her identity).

1 files changed, 33 insertions, 0 deletions

diff --git a/app/models/concerns/redactable.rb b/app/models/concerns/redactable.rb
new file mode 100644
index 00000000000..5ad96d6cc46
--- /dev/null
+++ b/app/models/concerns/redactable.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+# This module searches and redacts sensitive information in
+# redactable fields. Currently only unsubscribe link is redacted.
+# Add following lines into your model:
+#
+#     include Redactable
+#     redact_field :foo
+#
+module Redactable
+  extend ActiveSupport::Concern
+
+  UNSUBSCRIBE_PATTERN = %r{/sent_notifications/\h{32}/unsubscribe}
+
+  class_methods do
+    def redact_field(field)
+      before_validation do
+        redact_field!(field) if attribute_changed?(field)
+      end
+    end
+  end
+
+  private
+
+  def redact_field!(field)
+    text = public_send(field) # rubocop:disable GitlabSecurity/PublicSend
+    return unless text.present?
+
+    redacted = text.gsub(UNSUBSCRIBE_PATTERN, '/sent_notifications/REDACTED/unsubscribe')
+
+    public_send("#{field}=", redacted) # rubocop:disable GitlabSecurity/PublicSend
+  end
+end