GOSOCKS

Basic golang implementation of a socks5 proxy. This implementation is currently not feature complete and only supports the CONNECT command and no authentication.

This implemention also defines some handlers you can use to implement your own protocol behind this proxy server. This can be useful if you come a across a protocol that can be abused for proxy functionality and build a socks5 proxy around it.

The SOCKS protocol is defined in rfc1928

Documentation

https://pkg.go.dev/github.com/firefart/gosocks

Handler Interface

type ProxyHandler interface {
	Init(net.Addr, Request) (io.ReadWriteCloser, *Error)
	ReadFromClient(context.Context, io.ReadCloser, io.WriteCloser) error
	ReadFromRemote(context.Context, io.ReadCloser, io.WriteCloser) error
	Close() error
}

Init

Init is called before the copy operations and it should return a connection to the target that is ready to receive data.

ReadFromClient

ReadFromClient is the method that handles the data copy from the client (you) to the remote connection. You can see the DefaultHandler for a sample implementation.

ReadFromRemote

ReadFromRemote is the method that handles the data copy from the remote connection to the client (you). You can see the DefaultHandler for a sample implementation.

Close

Close is called after the request finishes or errors out. Client and remote connections are closed before this method is called.

Usage

Default Usage

package main

import (
	"time"

	socks "github.com/wikylyu/gosocks"
)

func main() {
	handler := socks.DefaultHandler{
		Timeout: 1 * time.Second,
	}
	listen := "127.0.0.1:8181"
	p := socks.Proxy{
		ServerAddr:   listen,
		Proxyhandler: handler,
		Timeout:      1 * time.Second,
	}
	if err := p.Start(); err != nil {
		panic(err)
	}
	<-p.Done
}

Usage with custom handlers

package main

import (
	"context"
	"io"
	"net"
	"time"

	socks "github.com/wikylyu/gosocks"
)

func main() {
	handler := &MyCustomHandler{
		Timeout: 1 * time.Second,
		PropA:   "A",
		PropB:   "B",
	}
	p := socks.Proxy{
		ServerAddr:   "127.0.0.1:8282",
		Proxyhandler: handler,
		Timeout:      1 * time.Second,
	}
	if err := p.Start(); err != nil {
		panic(err)
	}
	<-p.Done
}

type MyCustomHandler struct {
	Timeout time.Duration
	PropA   string
	PropB   string
}

func (s *MyCustomHandler) Init(addr net.Addr, request socks.Request) (io.ReadWriteCloser, *socks.Error) {
	conn, err := net.DialTimeout("tcp", request.GetDestinationString(), s.Timeout)
	if err != nil {
		return nil, socks.NewError(socks.RequestReplyHostUnreachable, err)
	}
	return conn, nil
}

func (s *MyCustomHandler) ReadFromRemote(ctx context.Context, remote io.ReadCloser, client io.WriteCloser) error {
	_, err := io.Copy(client, remote)
	if err != nil {
		return err
	}
	return nil
}

func (s *MyCustomHandler) ReadFromClient(ctx context.Context, client io.ReadCloser, remote io.WriteCloser) error {
	_, err := io.Copy(remote, client)
	if err != nil {
		return err
	}
	return nil
}

func (s *MyCustomHandler) Close() error {
	return nil
}