MIX_ENV=prod on a Phoenix server crashes on starting with PORT=80

Question

I am having some issues with mix, and MIX_ENV=prod with mix phoenix.server, where it fails on starting. Running all latest (Elixir 1.0.5, Phoenix 0.14.0) except Erlang (17.x, 17.3 I think) on Linode's Ubuntu 14.04.

$ MIX_ENV=prod PORT=80 mix phoenix.server
{"Kernel pid terminated",application_controller,"{application_start_failure,elirc_site,{{shutdown,{failed_to_start_child,'Elixir.ElircSite.Endpoint',{shutdown,{failed_to_start_child,'Elixir.Phoenix.Endpoint.Server',{shutdown,{failed_to_start_child,{ranch_listener_sup,'Elixir.ElircSite.Endpoint.HTTP'},{shutdown,{failed_to_start_child,ranch_acceptors_sup,{{badmatch,{error,eacces}},[{ranch_acceptors_sup,init,1,[{file,\"src/ranch_acceptors_sup.erl\"},{line,30}]},{supervisor,init,1,[{file,\"supervisor.erl\"},{line,243}]},{gen_server,init_it,6,[{file,\"gen_server.erl\"},{line,306}]},{proc_lib,init_p_do_apply,3,[{file,\"proc_lib.erl\"},{line,239}]}]}}}}}}}}},{'Elixir.ElircSite',start,[normal,[]]}}}"}

Specifically I think its this part of the trace.

{{badmatch,{error,eacces}},[{ranch_acceptors_sup,init,1,[{file,\"src/ranch_acceptors_sup.erl\"},{line,30}]}

Answer 1

As Nick Meharry pointed out you are trying to run your Phoenix server process on a port that traditionally on Unix, only root can bind to (low ports (<1024)).

Running your process as root is not recommended because of security reasons - an attacker who would take over the process could get root access to the whole operating system.

It's more secure to work around this by running your server on a high port (for instance, 4000) and use a simple iptables rule to forward the connections from port 80 to port 4000. Note that any user on your machine can bind to port 4000 - so you lose the extra protection from the low ports.

Another solution is to allow certain programs (mix, elixir) to bind to ports below 1024 using CAP_NET_BIND_SERVICE Linux kernels capability (available since 2.6.24) which can be set using setcap. But then still any user can use this executables unless they are available only to a certain user by using proper file access rights.