clue/socks-server

Async SOCKS proxy server (SOCKS4, SOCKS4a and SOCKS5), built on top of React PHP.

The SOCKS protocol family can be used to easily tunnel TCP connections independent of the actual application level protocol, such as HTTP, SMTP, IMAP, Telnet etc.

Table of contents

• Quickstart example
• Usage
  • Server
    • Protocol version
    • Authentication
    • Proxy chaining
• Install
• License
• More

Quickstart example

Once installed, you can use the following code to create a SOCKS proxy server listening for connections on localhost:1080:

$loop = React\EventLoop\Factory::create();

// listen on localhost:1080
$socket = new Socket($loop);
$socket->listen(1080,'localhost');

// start a new server listening for incoming connection on the given socket
$server = new Server($loop, $socket);

$loop->run();

See also the examples.

Usage

Server

The Server is responsible for accepting incoming communication from SOCKS clients and forwarding the requested connection to the target host. It also registers everything with the main EventLoop and an underlying TCP/IP socket server like this:

$loop = \React\EventLoop\Factory::create();

// listen on localhost:$port
$socket = new Socket($loop);
$socket->listen($port,'localhost');

$server = new Server($loop, $socket);

If you need custom connector settings (DNS resolution, timeouts etc.), you can explicitly pass a custom instance of the ConnectorInterface:

// use local DNS server
$dnsResolverFactory = new DnsFactory();
$resolver = $dnsResolverFactory->createCached('127.0.0.1', $loop);

// outgoing connections to target host via interface 192.168.10.1
$connector = new DnsConnector(
    new TcpConnector($loop, array('bindto' => '192.168.10.1:0')),
    $resolver
);

$server = new Server($loop, $socket, $connector);

Protocol version

The Server supports all protocol versions (SOCKS4, SOCKS4a and SOCKS5) by default.

While SOCKS4 already had (a somewhat limited) support for SOCKS BIND requests and SOCKS5 added generic UDP support (SOCKS UDPASSOCIATE), this library focuses on the most commonly used core feature of SOCKS CONNECT. In this mode, a SOCKS server acts as a generic proxy allowing higher level application protocols to work through it.

	SOCKS4	SOCKS4a	SOCKS5
Protocol specification	SOCKS4.protocol	SOCKS4A.protocol	RFC 1928
Tunnel outgoing TCP connections	✓	✓	✓
Remote DNS resolving	✗	✓	✓
IPv6 addresses	✗	✗	✓
Username/Password authentication	✗	✗	✓ (as per RFC 1929)
Handshake # roundtrips	1	1	2 (3 with authentication)
Handshake traffic + remote DNS	17 bytes ✗	17 bytes + hostname + 1	variable (+ auth + IPv6) + hostname - 3

Note, this is not a full SOCKS5 implementation due to missing GSSAPI authentication (but it's unlikely you're going to miss it anyway).

If want to explicitly set the protocol version, use the supported values 4, 4a or 5:

$server->setProtocolVersion(5);

In order to reset the protocol version to its default (i.e. automatic detection), use null as protocol version.

$server->setProtocolVersion(null);

Authentication

By default, the Server does not require any authentication from the clients. You can enable authentication support so that clients need to pass a valid username and password before forwarding any connections.

Setting authentication on the Server enforces each further connected client to use protocol version 5 (SOCKS5). If a client tries to use any other protocol version, does not send along authentication details or if authentication details can not be verified, the connection will be rejected.

Because your authentication mechanism might take some time to actually check the provided authentication credentials (like querying a remote database or webservice), the server side uses a Promise based interface. While this might seem complex at first, it actually provides a very simple way to handle simultanous connections in a non-blocking fashion and increases overall performance.

$server->setAuth(function ($username, $password) {
    // either return a boolean success value right away
    // or use promises for delayed authentication
});

Or if you only accept static authentication details, you can use the simple array-based authentication method as a shortcut:

$server->setAuthArray(array(
    'tom' => 'password',
    'admin' => 'root'
));

If you do not want to use authentication anymore:

$server->unsetAuth();

Proxy chaining

The Server is responsible for creating connections to the target host.

Client -> SocksServer -> TargetHost

Sometimes it may be required to establish outgoing connections via another SOCKS server. For example, this can be useful if your target SOCKS server requires authentication, but your client does not support sending authentication information (e.g. like most webbrowser).

Client -> MiddlemanSocksServer -> TargetSocksServer -> TargetHost

The Server uses any instance of the ConnectorInterface to establish outgoing connections. In order to connect through another SOCKS server, you can simply use a SOCKS connector from the following SOCKS client package:

$ composer require clue/socks-react:^0.4

You can now create a SOCKS Client instance like this:

// set next SOCKS server localhost:$targetPort as target
$target = new Clue\React\Socks\Client('127.0.0.1:' . $targetPort, $loop);
$target->setAuth('user', 'p@ssw0rd');

// listen on localhost:$middlemanPort
$socket = new Socket($loop);
$socket->listen($middlemanPort, 'localhost');

// start a new server which forwards all connections to the other SOCKS server
$server = new Server($loop, $socket, $target->createConnector());

Install

The recommended way to install this library is through Composer. New to Composer?

This will install the latest supported version:

$ composer require clue/socks-server:^0.5

See also the CHANGELOG for details about version upgrades.

License

MIT, see LICENSE

More

• If you're looking for an end-user SOCKS server daemon, you may want to use clue/psocksd.
• If you're looking for a SOCKS client implementation, consider using clue/socks-react.