/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/ is in ruby-railties 2:4.2.6-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/controllers/
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/controllers/%name%/
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/controllers/%name%/application_controller.rb.tt
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/helpers/
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/helpers/%name%/
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/helpers/%name%/application_helper.rb.tt
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/views/
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/views/layouts/
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/views/layouts/%name%/
/usr/lib/ruby/vendor_ruby/rails/generators/rails/plugin/templates/app/views/layouts/%name%/application.html.erb.tt