/usr/lib/ruby/vendor_ruby/ is in ruby-warden 1.2.3-2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/warden/test/
/usr/lib/ruby/vendor_ruby/warden/manager.rb
/usr/lib/ruby/vendor_ruby/warden/
/usr/lib/ruby/vendor_ruby/warden/version.rb
/usr/lib/ruby/vendor_ruby/warden/session_serializer.rb
/usr/lib/ruby/vendor_ruby/warden/errors.rb
/usr/lib/ruby/vendor_ruby/warden/strategies.rb
/usr/lib/ruby/vendor_ruby/warden/mixins/
/usr/lib/ruby/vendor_ruby/warden/mixins/common.rb
/usr/lib/ruby/vendor_ruby/warden/test/helpers.rb
/usr/lib/ruby/vendor_ruby/warden/test/warden_helpers.rb
/usr/lib/ruby/vendor_ruby/warden/config.rb
/usr/lib/ruby/vendor_ruby/warden/strategies/
/usr/lib/ruby/vendor_ruby/warden/strategies/base.rb
/usr/lib/ruby/vendor_ruby/warden/hooks.rb
/usr/lib/ruby/vendor_ruby/warden/proxy.rb
/usr/lib/ruby/vendor_ruby/warden.rb