这是我参与「第五届青训营 」伴学笔记创作活动的第 1 天
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前言
根据教程的做法，是使用一步一步迭代进行完整的代理服务器搭建，其实思路跟验证模块差不多，先在框架下把一个模块验证完整后再添加新的模块。这里根据教程中的四次迭代进行笔记撰写。
第一代：简单复读机
package main
import (
"bufio"
"log"
"net"
)
func main() {
server, err := net.Listen("tcp", "127.0.0.1:1080")
if err != nil {
panic(err)
}
for {
client, err := server.Accept()
if err != nil {
log.Printf("Accept failed %v", err)
continue
}
go process(client)
}
}
func process(conn net.Conn) {
defer conn.Close()
reader := bufio.NewReader(conn)
for {
b, err := reader.ReadByte()
if err != nil {
break
}
_, err = conn.Write([]byte{b})
if err != nil {
break
}
}
}
使用nc（netcat）进行简单tcp链接
nc 127.0.0.1 1080
此时，服务器返回的数据取决于客户端发送的数据
因为在
process函数中，服务端循环读取客户端发送的数据，并将其逐个输出到屏幕中。
然而实际上，在执行中，会将循环读取的操作合并，以减少资源消耗
第二代 鉴权
package main
import (
"bufio"
"fmt"
"io"
"log"
"net"
)
const socks5Ver = 0x05
const cmdBind = 0x01
const atypIPV4 = 0x01
const atypeHOST = 0x03
const atypeIPV6 = 0x04
func main() {
server, err := net.Listen("tcp", "127.0.0.1:1080")
if err != nil {
panic(err)
}
for {
client, err := server.Accept()
if err != nil {
log.Printf("Accept failed %v", err)
continue
}
go process(client)
}
}
func process(conn net.Conn) {
defer conn.Close()
reader := bufio.NewReader(conn)
err := auth(reader, conn)
if err != nil {
log.Printf("client %v auth failed:%v", conn.RemoteAddr(), err)
return
}
log.Println("auth success")
}
func auth(reader *bufio.Reader, conn net.Conn) (err error) {
ver, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read ver failed:%w", err)
}
if ver != socks5Ver {
return fmt.Errorf("not supported ver:%v", ver)
}
methodSize, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read methodSize failed:%w", err)
}
method := make([]byte, methodSize)
_, err = io.ReadFull(reader, method)
if err != nil {
return fmt.Errorf("read method failed:%w", err)
}
log.Println("ver", ver, "method", method)
_, err = conn.Write([]byte{socks5Ver, 0x00})
if err != nil {
return fmt.Errorf("write failed:%w", err)
}
return nil
}
这里使用的是无需鉴权，但是已经开始进行socks5协议的匹配。 这里一共读取了三个字段，分别是
1.版本号
2.支持认证方法的数量
3.认证方式
第三代 连接
package main
import (
"bufio"
"encoding/binary"
"errors"
"fmt"
"io"
"log"
"net"
)
const socks5Ver = 0x05
const cmdBind = 0x01
const atypIPV4 = 0x01
const atypeHOST = 0x03
const atypeIPV6 = 0x04
func main() {
server, err := net.Listen("tcp", "127.0.0.1:1080")
if err != nil {
panic(err)
}
for {
client, err := server.Accept()
if err != nil {
log.Printf("Accept failed %v", err)
continue
}
go process(client)
}
}
func process(conn net.Conn) {
defer conn.Close()
reader := bufio.NewReader(conn)
err := auth(reader, conn)
if err != nil {
log.Printf("client %v auth failed:%v", conn.RemoteAddr(), err)
return
}
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) (err error) {
ver, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read ver failed:%w", err)
}
if ver != socks5Ver {
return fmt.Errorf("not supported ver:%v", ver)
}
methodSize, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read methodSize failed:%w", err)
}
method := make([]byte, methodSize)
_, err = io.ReadFull(reader, method)
if err != nil {
return fmt.Errorf("read method failed:%w", err)
}
_, err = conn.Write([]byte{socks5Ver, 0x00})
if err != nil {
return fmt.Errorf("write failed:%w", err)
}
return nil
}
func connect(reader *bufio.Reader, conn net.Conn) (err error) {
buf := make([]byte, 4)
_, err = io.ReadFull(reader, buf)
if err != nil {
return fmt.Errorf("read header failed:%w", err)
}
ver, cmd, atyp := buf[0], buf[1], buf[3]
if ver != socks5Ver {
return fmt.Errorf("not supported ver:%v", ver)
}
if cmd != cmdBind {
return fmt.Errorf("not supported cmd:%v", ver)
}
addr := ""
switch atyp {
case atypIPV4:
_, err = io.ReadFull(reader, buf)
if err != nil {
return fmt.Errorf("read atyp failed:%w", err)
}
addr = fmt.Sprintf("%d.%d.%d.%d", buf[0], buf[1], buf[2], buf[3])
case atypeHOST:
hostSize, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read hostSize failed:%w", err)
}
host := make([]byte, hostSize)
_, err = io.ReadFull(reader, host)
if err != nil {
return fmt.Errorf("read host failed:%w", err)
}
addr = string(host)
case atypeIPV6:
return errors.New("IPv6: no supported yet")
default:
return errors.New("invalid atyp")
}
_, err = io.ReadFull(reader, buf[:2])
if err != nil {
return fmt.Errorf("read port failed:%w", err)
}
port := binary.BigEndian.Uint16(buf[:2])
log.Println("dial", addr, port)
_, err = conn.Write([]byte{0x05, 0x00, 0x00, 0x01, 0, 0, 0, 0, 0, 0})
if err != nil {
return fmt.Errorf("write failed: %w", err)
}
return nil
}
经过修改后，则此时可以正常识别到请求报文中的请求地址、端口等信息。
第四代 代理
package main
import (
"bufio"
"context"
"encoding/binary"
"errors"
"fmt"
"io"
"log"
"net"
)
const socks5Ver = 0x05
const cmdBind = 0x01
const atypIPV4 = 0x01
const atypeHOST = 0x03
const atypeIPV6 = 0x04
func main() {
server, err := net.Listen("tcp", "127.0.0.1:10800")
if err != nil {
panic(err)
}
for {
client, err := server.Accept()
if err != nil {
log.Printf("Accept failed %v", err)
continue
}
go process(client)
}
}
func process(conn net.Conn) {
defer conn.Close()
reader := bufio.NewReader(conn)
err := auth(reader, conn)
if err != nil {
log.Printf("client %v auth failed:%v", conn.RemoteAddr(), err)
return
}
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) (err error) {
ver, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read ver failed:%w", err)
}
if ver != socks5Ver {
return fmt.Errorf("not supported ver:%v", ver)
}
methodSize, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read methodSize failed:%w", err)
}
method := make([]byte, methodSize)
_, err = io.ReadFull(reader, method)
if err != nil {
return fmt.Errorf("read method failed:%w", err)
}
_, err = conn.Write([]byte{socks5Ver, 0x00})
if err != nil {
return fmt.Errorf("write failed:%w", err)
}
return nil
}
func connect(reader *bufio.Reader, conn net.Conn) (err error) {
buf := make([]byte, 4)
_, err = io.ReadFull(reader, buf)
if err != nil {
return fmt.Errorf("read header failed:%w", err)
}
ver, cmd, atyp := buf[0], buf[1], buf[3]
if ver != socks5Ver {
return fmt.Errorf("not supported ver:%v", ver)
}
if cmd != cmdBind {
return fmt.Errorf("not supported cmd:%v", ver)
}
addr := ""
switch atyp {
case atypIPV4:
_, err = io.ReadFull(reader, buf)
if err != nil {
return fmt.Errorf("read atyp failed:%w", err)
}
addr = fmt.Sprintf("%d.%d.%d.%d", buf[0], buf[1], buf[2], buf[3])
case atypeHOST:
hostSize, err := reader.ReadByte()
if err != nil {
return fmt.Errorf("read hostSize failed:%w", err)
}
host := make([]byte, hostSize)
_, err = io.ReadFull(reader, host)
if err != nil {
return fmt.Errorf("read host failed:%w", err)
}
addr = string(host)
case atypeIPV6:
return errors.New("IPv6: no supported yet")
default:
return errors.New("invalid atyp")
}
_, err = io.ReadFull(reader, buf[:2])
if err != nil {
return fmt.Errorf("read port failed:%w", err)
}
port := binary.BigEndian.Uint16(buf[:2])
dest, err := net.Dial("tcp", fmt.Sprintf("%v:%v", addr, port))
if err != nil {
return fmt.Errorf("dial dst failed:%w", err)
}
defer dest.Close()
log.Println("dial", addr, port)
_, err = conn.Write([]byte{0x05, 0x00, 0x00, 0x01, 0, 0, 0, 0, 0, 0})
if err != nil {
return fmt.Errorf("write failed: %w", err)
}
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
go func() {
_, _ = io.Copy(dest, reader)
cancel()
}()
go func() {
_, _ = io.Copy(conn, dest)
cancel()
}()
<-ctx.Done()
return nil
}
此时服务器可以正常代理，转发请求了。
在代码的第173行，使用了双向转发
并且使用了context机制，在通信双方任意一方终止通讯时才会结束程序。
