Tunnerl is a versatile SOCKS4, SOCKS4a, and SOCKS5 proxy protocol implementation in Erlang/OTP. It enables you to create a powerful and flexible proxy server to facilitate secure and efficient communication across various network environments.

tunnerl offers a range of features for proxying TCP connections, making it a valuable tool for network communication. These features include:

• SOCKS Protocol Support:
  • SOCKS4: A protocol for TCP proxy across firewalls (socks4.protocol).
    • Supports the connect command only.
  • SOCKS 4A: A Simple Extension to SOCKS 4 Protocol (socks4a.protocol).
  • SOCKS Protocol Version 5 (RFC1928):
    • Supports the connect command only.
    • Username/Password Authentication for SOCKS V5 (RFC1929).
    • ATYPs: IPv4, IPv6, and domain.

Follow these steps to integrate Tunnerl into your Erlang or Elixir application:

1. Add tunnerl to your list of dependencies in rebar.config:

{deps, [
    {tunnerl, "1.0.0"}
]}.

2. Ensure tunnerl is started before your application:

{applications, [tunnerl]}.

3. Configure tunnerl to use custom handler::

{tunnerl, [
    {protocols, [socks4, socks5]},
    {handler, myapp_handler},
    {acceptors, 10},
    {ip, {0, 0, 0, 0}},
    {port, 1080}
]}.

4. Implement your own myapp_handler module. This module defines how tunnerl handles authentication and connection requests based on your application's requirements.

-module(myapp_handler).

%% This simple handler module accepts username authentication and
%% allows user with password "pass" do connect command.
%% Also, is accepts all connections on Socks4 for "root".

-export([auth_methods/0,
         auth/1,
         handle_command/1]).

auth_methods() -> [username].

auth(#{username := <<"user">>,
       password := <<"pass">>}) ->
    accept;
auth(_) -> reject.

handle_command(#{protocol := socks4,
                 command := connect,
                 username := <<"root">>}) ->
    accept;
handle_command(#{protocol := socks5,
                 command := connect,
                 username := <<"user">>}) ->
    accept;
handle_command(_) ->
    reject.

To test tunnerl, follow these steps:

1. Clone the tunnerl repository and compile the code:

$ git clone https://github.com/surik/tunnerl.git
$ cd tunnerl
$ rebar3 compile

2. Run Tunnerl with a predefined configuration that includes SOCKS4 and SOCKS5 support with no authentication:

$ rebar3 shell --name [email protected] --config tunnerl.config --apps tunnerl

3. You can run a series of common tests to ensure everything is working as expected:

$ rebar3 ct

Note: IPv6 tests may not work on all local machines.