/usr/lib/ruby/vendor_ruby/ is in ruby-riddle 1.5.12-4ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/riddle/
/usr/lib/ruby/vendor_ruby/riddle.rb
/usr/lib/ruby/vendor_ruby/riddle/0.9.8.rb
/usr/lib/ruby/vendor_ruby/riddle/0.9.9/
/usr/lib/ruby/vendor_ruby/riddle/0.9.9.rb
/usr/lib/ruby/vendor_ruby/riddle/0.9.9/client/
/usr/lib/ruby/vendor_ruby/riddle/0.9.9/client.rb
/usr/lib/ruby/vendor_ruby/riddle/0.9.9/client/filter.rb
/usr/lib/ruby/vendor_ruby/riddle/0.9.9/configuration/
/usr/lib/ruby/vendor_ruby/riddle/0.9.9/configuration/searchd.rb
/usr/lib/ruby/vendor_ruby/riddle/1.10/
/usr/lib/ruby/vendor_ruby/riddle/1.10.rb
/usr/lib/ruby/vendor_ruby/riddle/1.10/client.rb
/usr/lib/ruby/vendor_ruby/riddle/2.0.1/
/usr/lib/ruby/vendor_ruby/riddle/2.0.1.rb
/usr/lib/ruby/vendor_ruby/riddle/2.0.1/client.rb
/usr/lib/ruby/vendor_ruby/riddle/2.1.0.rb
/usr/lib/ruby/vendor_ruby/riddle/auto_version.rb
/usr/lib/ruby/vendor_ruby/riddle/client/
/usr/lib/ruby/vendor_ruby/riddle/client.rb
/usr/lib/ruby/vendor_ruby/riddle/client/filter.rb
/usr/lib/ruby/vendor_ruby/riddle/client/message.rb
/usr/lib/ruby/vendor_ruby/riddle/client/response.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/
/usr/lib/ruby/vendor_ruby/riddle/configuration.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/common.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/distributed_index.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/index.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/index_settings.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/indexer.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/parser.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/realtime_index.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/remote_index.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/searchd.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/section.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/source.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/sql_source.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/template_index.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/tsv_source.rb
/usr/lib/ruby/vendor_ruby/riddle/configuration/xml_source.rb
/usr/lib/ruby/vendor_ruby/riddle/controller.rb
/usr/lib/ruby/vendor_ruby/riddle/query/
/usr/lib/ruby/vendor_ruby/riddle/query.rb
/usr/lib/ruby/vendor_ruby/riddle/query/delete.rb
/usr/lib/ruby/vendor_ruby/riddle/query/insert.rb
/usr/lib/ruby/vendor_ruby/riddle/query/select.rb