/usr/lib/ruby/vendor_ruby/net/sftp/protocol/ is in ruby-net-sftp 1:2.1.2-3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/01/
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/01/attributes.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/01/base.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/01/name.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/02/
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/02/base.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/03/
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/03/base.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/04/
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/04/attributes.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/04/base.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/04/name.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/05/
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/05/base.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/06/
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/06/attributes.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/06/base.rb
/usr/lib/ruby/vendor_ruby/net/sftp/protocol/base.rb