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package main
import (
"bufio"
"encoding/binary"
"errors"
"fmt"
"io"
"log"
"net"
"sync"
)
const socks5Version = 0x05
const subnegotiation = 0x01
const connectCommand = 0x01
const bindCommand = 0x02
const udpAssociateCommand = 0x03
const ipv4AddressType = 0x01
const ipv6AddressType = 0x04
const domainAddressType = 0x03
func main() {
server, err := net.Listen("tcp", ":8080")
if err != nil {
panic(err)
}
for {
client, err := server.Accept()
if err != nil {
log.Printf("Error accepting client connection: %v", err)
continue
}
go process(client)
}
}
func process(conn net.Conn) {
defer conn.Close()
/* 开始协商 */
reader := bufio.NewReader(conn)
err := auth(reader, conn)
if err != nil {
log.Printf("client %v auth failed:%v", conn.RemoteAddr(), err)
return
}
//auReader := bufio.NewReader(conn)
//err = authenticate(auReader, conn)
//if err != nil {
// log.Printf("client %v auth failed:%v", conn.RemoteAddr(), err)
// return
//}
/* 协商成功, 进入请求阶段 */
err = connect(reader, conn)
if err != nil {
log.Printf("client %v auth failed:%v", conn.RemoteAddr(), err)
return
}
}
func auth(reader *bufio.Reader, conn net.Conn) error {
ver, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("Error reading ver: %v", err)
}
if ver != socks5Version {
log.Println(ver)
return fmt.Errorf("Unsupported socks5 version: %v", ver)
}
methodSize, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("Error reading method size: %v", err)
}
method := make([]byte, methodSize)
_, err = reader.Read(method)
if err != nil {
return fmt.Errorf("Error reading method: %v", err)
}
_, err = conn.Write([]byte{socks5Version, 0x00})
if err != nil {
return fmt.Errorf("Error writing method response: %v", err)
}
return nil
}
func authenticate(reader *bufio.Reader, conn net.Conn) error {
/**
* +----+------+----------+------+----------+
* |VER | ULEN | UNAME | PLEN | PASSWD |
* +----+------+----------+------+----------+
* | 1 | 1 | 1 to 255 | 1 | 1 to 255 |
* +----+------+----------+------+----------+
*/
ver, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read ver failed:%w", err)
}
if ver != subnegotiation {
log.Printf("subnegotiation：%v ", subnegotiation)
return fmt.Errorf("not supported ver:%v", ver)
}
ulen, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read ulen failed:%w", err)
}
uname := make([]byte, ulen)
_, err = io.ReadFull(reader, uname)
if err != nil {
return fmt.Errorf("read uname failed:%w", err)
}
if string(uname) != "admin" {
_, err = conn.Write([]byte{0x01, 0x01})
if err != nil {
return fmt.Errorf("write failed:%w", err)
}
return fmt.Errorf("auth uname failed:%w", err)
}
plen, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read plen failed:%w", err)
}
passwd := make([]byte, plen)
_, err = io.ReadFull(reader, passwd)
if err != nil {
return fmt.Errorf("read passwd failed:%w", err)
}
if string(passwd) != "123456" {
_, err = conn.Write([]byte{0x01, 0x01})
if err != nil {
return fmt.Errorf("write failed:%w", err)
}
return fmt.Errorf("auth uname failed:%w", err)
}
/* +----+--------+
* |VER | STATUS |
* +----+--------+
* | 1 | 1 |
* +----+--------+
*/
_, err = conn.Write([]byte{0x01, 0x00})
if err != nil {
return fmt.Errorf("write failed:%w", err)
}
return nil
}
func connect(reader *bufio.Reader, conn net.Conn) error {
// +----+-----+-------+------+----------+----------+
// |VER | CMD | RSV | ATYP | DST.ADDR | DST.PORT |
// +----+-----+-------+------+----------+----------+
// | 1 | 1 | X'00' | 1 | Variable | 2 |
// +----+-----+-------+------+----------+----------+
// VER 版本号，socks5的值为0x05
// CMD 0x01表示CONNECT请求
// RSV 保留字段，值为0x00
// ATYP 目标地址类型，DST.ADDR的数据对应这个字段的类型。
// 0x01表示IPv4地址，DST.ADDR为4个字节
// 0x03表示域名，DST.ADDR是一个可变长度的域名
// DST.ADDR 一个可变长度的值
// DST.PORT 目标端口，固定2个字节
buf := make([]byte, 4)
ipv4buf := make([]byte, 4)
ipv6buf := make([]byte, 16)
portbuf := make([]byte, 2)
_, err := reader.Read(buf)
if err != nil {
return fmt.Errorf("read header failed:%w", err)
}
ver, cmd, atyp := buf[0], buf[1], buf[3]
if ver != socks5Version {
return fmt.Errorf("Unsupported socks5 ver: %v", ver)
}
if cmd != connectCommand {
return fmt.Errorf("not supported cmd:%v", cmd)
}
addr := ""
switch atyp {
case ipv4AddressType:
_, err = reader.Read(ipv4buf)
if err != nil {
return fmt.Errorf("read ipv4 address failed:%w", err)
}
addr = net.IP(ipv4buf).String()
case ipv6AddressType:
_, err = reader.Read(ipv6buf)
if err != nil {
return fmt.Errorf("read ipv6 address failed:%w", err)
}
addr = net.IP(ipv6buf).String()
case domainAddressType:
hostSize, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read hostSize failed:%w", err)
}
host := make([]byte, hostSize)
_, err = reader.Read(host)
addr = string(host)
default:
return errors.New("invalid atyp")
}
_, err = reader.Read(portbuf)
port := binary.BigEndian.Uint16(portbuf)
if err != nil {
return fmt.Errorf("read port failed:%w", err)
}
dest, err := net.Dial("tcp", fmt.Sprintf("%s:%d", addr, port))
if err != nil {
return fmt.Errorf("connect to %s:%d failed:%w", addr, port, err)
}
defer dest.Close()
log.Println("dial", addr, port)
// +----+-----+-------+------+----------+----------+
// |VER | REP | RSV | ATYP | BND.ADDR | BND.PORT |
// +----+-----+-------+------+----------+----------+
// | 1 | 1 | X'00' | 1 | Variable | 2 |
// +----+-----+-------+------+----------+----------+
// VER socks版本，这里为0x05
// REP Relay field,内容取值如下 X’00’ succeeded
// RSV 保留字段
// ATYPE 地址类型
// BND.ADDR 服务绑定的地址
// BND.PORT 服务绑定的端口DST.PORT
_, err = conn.Write([]byte{0x05, 0x00, 0x00, ipv4AddressType, 0, 0, 0, 0, 0, 0})
if err != nil {
return fmt.Errorf("write failed: %w", err)
}
var wg sync.WaitGroup
wg.Add(2)
go func() {
defer wg.Done()
io.Copy(dest, conn)
}()
go func() {
defer wg.Done()
io.Copy(conn, dest)
}()
wg.Wait()
return nil
}
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