pt

Overview ¶

Package pt implements the Tor pluggable transports specification.

Sample client usage:

var ptInfo pt.ClientInfo
...
func handler(conn *pt.SocksConn) error {
	defer conn.Close()
	remote, err := net.Dial("tcp", conn.Req.Target)
	if err != nil {
		conn.Reject()
		return err
	}
	defer remote.Close()
	err = conn.Grant(remote.RemoteAddr().(*net.TCPAddr))
	if err != nil {
		return err
	}
	// do something with conn and remote.
	return nil
}
func acceptLoop(ln *pt.SocksListener) error {
	defer ln.Close()
	for {
		conn, err := ln.AcceptSocks()
		if err != nil {
			if e, ok := err.(net.Error); ok && e.Temporary() {
				continue
			}
			return err
		}
		go handler(conn)
	}
	return nil
}
...
func main() {
	var err error
	ptInfo, err = pt.ClientSetup(nil)
	if err != nil {
		os.Exit(1)
	}
	if ptInfo.ProxyURL != nil {
		// you need to interpret the proxy URL yourself
		// call pt.ProxyDone instead if it's a type you understand
		pt.ProxyError("proxy %s is not supported")
		os.Exit(1)
	}
	for _, methodName := range ptInfo.MethodNames {
		switch methodName {
		case "foo":
			ln, err := pt.ListenSocks("tcp", "127.0.0.1:0")
			if err != nil {
				pt.CmethodError(methodName, err.Error())
				break
			}
			go acceptLoop(ln)
			pt.Cmethod(methodName, ln.Version(), ln.Addr())
		default:
			pt.CmethodError(methodName, "no such method")
		}
	}
	pt.CmethodsDone()
}

Sample server usage:

var ptInfo pt.ServerInfo
...
func handler(conn net.Conn) error {
	defer conn.Close()
	or, err := pt.DialOr(&ptInfo, conn.RemoteAddr().String(), "foo")
	if err != nil {
		return
	}
	defer or.Close()
	// do something with or and conn
	return nil
}
func acceptLoop(ln net.Listener) error {
	defer ln.Close()
	for {
		conn, err := ln.Accept()
		if err != nil {
			if e, ok := err.(net.Error); ok && e.Temporary() {
				continue
			}
			return err
		}
		go handler(conn)
	}
	return nil
}
...
func main() {
	var err error
	ptInfo, err = pt.ServerSetup(nil)
	if err != nil {
		os.Exit(1)
	}
	for _, bindaddr := range ptInfo.Bindaddrs {
		switch bindaddr.MethodName {
		case "foo":
			ln, err := net.ListenTCP("tcp", bindaddr.Addr)
			if err != nil {
				pt.SmethodError(bindaddr.MethodName, err.Error())
				break
			}
			go acceptLoop(ln)
			pt.Smethod(bindaddr.MethodName, ln.Addr())
		default:
			pt.SmethodError(bindaddr.MethodName, "no such method")
		}
	}
	pt.SmethodsDone()
}

Some additional care is needed to handle signals and shutdown properly. See the example programs dummy-client and dummy-server.

Tor pluggable transports specification: https://spec.torproject.org/pt-spec

Extended ORPort: https://gitweb.torproject.org/torspec.git/tree/proposals/196-transport-control-ports.txt.

Extended ORPort Authentication: https://gitweb.torproject.org/torspec.git/tree/proposals/217-ext-orport-auth.txt.

Pluggable Transport through SOCKS proxy: https://gitweb.torproject.org/torspec.git/tree/proposals/232-pluggable-transports-through-proxy.txt

The package implements a SOCKS5 server sufficient for a Tor client transport plugin.

https://www.ietf.org/rfc/rfc1928.txt https://www.ietf.org/rfc/rfc1929.txt