From 6b880ba22d1850b0b572cb93aca786884e5c4d08 Mon Sep 17 00:00:00 2001
From: Toby <tobyxdd@gmail.com>
Date: Sat, 26 Feb 2022 13:05:52 -0800
Subject: [PATCH] feat wip: SOCKS5 client DialTCP

---
 pkg/socks5/client.go | 118 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 pkg/socks5/client.go

diff --git a/pkg/socks5/client.go b/pkg/socks5/client.go
new file mode 100644
index 0000000..e8ea466
--- /dev/null
+++ b/pkg/socks5/client.go
@@ -0,0 +1,118 @@
+package socks5
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"github.com/txthinking/socks5"
+	"net"
+	"time"
+)
+
+type Client struct {
+	ServerTCPAddr *net.TCPAddr
+	Username      string
+	Password      string
+	NegTimeout    time.Duration
+}
+
+func NewClient(serverAddr string, username string, password string, negTimeout time.Duration) (*Client, error) {
+	tcpAddr, err := net.ResolveTCPAddr("tcp", serverAddr)
+	if err != nil {
+		return nil, err
+	}
+	return &Client{
+		ServerTCPAddr: tcpAddr,
+		Username:      username,
+		Password:      password,
+		NegTimeout:    negTimeout,
+	}, nil
+}
+
+func (c *Client) negotiate(conn *net.TCPConn) error {
+	m := []byte{socks5.MethodNone}
+	if c.Username != "" && c.Password != "" {
+		m = append(m, socks5.MethodUsernamePassword)
+	}
+	rq := socks5.NewNegotiationRequest(m)
+	_, err := rq.WriteTo(conn)
+	if err != nil {
+		return err
+	}
+	rs, err := socks5.NewNegotiationReplyFrom(conn)
+	if err != nil {
+		return err
+	}
+	if rs.Method == socks5.MethodUsernamePassword {
+		urq := socks5.NewUserPassNegotiationRequest([]byte(c.Username), []byte(c.Password))
+		_, err = urq.WriteTo(conn)
+		if err != nil {
+			return err
+		}
+		urs, err := socks5.NewUserPassNegotiationReplyFrom(conn)
+		if err != nil {
+			return err
+		}
+		if urs.Status != socks5.UserPassStatusSuccess {
+			return ErrUserPassAuth
+		}
+	} else if rs.Method != socks5.MethodNone {
+		return errors.New("unsupported auth method")
+	}
+	return nil
+}
+
+func (c *Client) Request(conn *net.TCPConn, r *socks5.Request) (*socks5.Reply, error) {
+	if _, err := r.WriteTo(conn); err != nil {
+		return nil, err
+	}
+	reply, err := socks5.NewReplyFrom(conn)
+	if err != nil {
+		return nil, err
+	}
+	return reply, nil
+}
+
+func (c *Client) DialTCP(raddr *net.TCPAddr) (*net.TCPConn, error) {
+	conn, err := net.DialTCP("tcp", nil, c.ServerTCPAddr)
+	if err != nil {
+		return nil, err
+	}
+	if err := conn.SetDeadline(time.Now().Add(c.NegTimeout)); err != nil {
+		return nil, err
+	}
+	err = c.negotiate(conn)
+	if err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	var atyp byte
+	var addr, port []byte
+	if ip4 := raddr.IP.To4(); ip4 != nil {
+		atyp = socks5.ATYPIPv4
+		addr = ip4
+	} else if ip6 := raddr.IP.To16(); ip6 != nil {
+		atyp = socks5.ATYPIPv6
+		addr = ip6
+	} else {
+		_ = conn.Close()
+		return nil, errors.New("unsupported address type")
+	}
+	port = make([]byte, 2)
+	binary.BigEndian.PutUint16(port, uint16(raddr.Port))
+	r := socks5.NewRequest(socks5.CmdConnect, atyp, addr, port)
+	reply, err := c.Request(conn, r)
+	if err != nil {
+		_ = conn.Close()
+		return nil, err
+	}
+	if reply.Rep != socks5.RepSuccess {
+		_ = conn.Close()
+		return nil, fmt.Errorf("request failed: %s", reply.Rep)
+	}
+	// Negotiation succeed, disable timeout
+	if err := conn.SetDeadline(time.Time{}); err != nil {
+		return nil, err
+	}
+	return conn, nil
+}