/usr/lib/ruby/vendor_ruby/net/ssh/authentication/ is in ruby-net-ssh 1:2.2.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/agent.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/constants.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/key_manager.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/methods/
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/methods/abstract.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/methods/hostbased.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/methods/keyboard_interactive.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/methods/password.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/methods/publickey.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/pageant.rb
/usr/lib/ruby/vendor_ruby/net/ssh/authentication/session.rb