1

pkg/proxy/socks5.go

@@ -0,0 +1,145 @@
+package proxy
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+	"net"
+)
+
+const (
+	socks5Version = 0x05
+	noAuth        = 0x00
+	cmdConnect    = 0x01
+	atypIPv4      = 0x01
+	atypDomain    = 0x03
+	atypIPv6      = 0x04
+)
+
+// SOCKS5Server SOCKS5 代理服务
+type SOCKS5Server struct {
+	dialer Dialer
+}
+
+// Dialer 连接拨号器接口
+type Dialer interface {
+	Dial(network, address string) (net.Conn, error)
+}
+
+// NewSOCKS5Server 创建 SOCKS5 服务
+func NewSOCKS5Server(dialer Dialer) *SOCKS5Server {
+	return &SOCKS5Server{dialer: dialer}
+}
+
+// HandleConn 处理 SOCKS5 连接
+func (s *SOCKS5Server) HandleConn(conn net.Conn) error {
+	defer conn.Close()
+
+	// 握手阶段
+	if err := s.handshake(conn); err != nil {
+		return err
+	}
+
+	// 获取请求
+	target, err := s.readRequest(conn)
+	if err != nil {
+		return err
+	}
+
+	// 连接目标
+	remote, err := s.dialer.Dial("tcp", target)
+	if err != nil {
+		s.sendReply(conn, 0x05) // Connection refused
+		return err
+	}
+	defer remote.Close()
+
+	// 发送成功响应
+	if err := s.sendReply(conn, 0x00); err != nil {
+		return err
+	}
+
+	// 双向转发
+	go io.Copy(remote, conn)
+	io.Copy(conn, remote)
+
+	return nil
+}
+
+// handshake 处理握手
+func (s *SOCKS5Server) handshake(conn net.Conn) error {
+	buf := make([]byte, 2)
+	if _, err := io.ReadFull(conn, buf); err != nil {
+		return err
+	}
+	if buf[0] != socks5Version {
+		return errors.New("unsupported SOCKS version")
+	}
+
+	nmethods := int(buf[1])
+	methods := make([]byte, nmethods)
+	if _, err := io.ReadFull(conn, methods); err != nil {
+		return err
+	}
+
+	// 响应：使用无认证
+	_, err := conn.Write([]byte{socks5Version, noAuth})
+	return err
+}
+
+// readRequest 读取请求
+func (s *SOCKS5Server) readRequest(conn net.Conn) (string, error) {
+	buf := make([]byte, 4)
+	if _, err := io.ReadFull(conn, buf); err != nil {
+		return "", err
+	}
+
+	if buf[0] != socks5Version || buf[1] != cmdConnect {
+		return "", errors.New("unsupported command")
+	}
+
+	var host string
+	switch buf[3] {
+	case atypIPv4:
+		ip := make([]byte, 4)
+		if _, err := io.ReadFull(conn, ip); err != nil {
+			return "", err
+		}
+		host = net.IP(ip).String()
+	case atypDomain:
+		lenBuf := make([]byte, 1)
+		if _, err := io.ReadFull(conn, lenBuf); err != nil {
+			return "", err
+		}
+		domain := make([]byte, lenBuf[0])
+		if _, err := io.ReadFull(conn, domain); err != nil {
+			return "", err
+		}
+		host = string(domain)
+	case atypIPv6:
+		ip := make([]byte, 16)
+		if _, err := io.ReadFull(conn, ip); err != nil {
+			return "", err
+		}
+		host = net.IP(ip).String()
+	default:
+		return "", errors.New("unsupported address type")
+	}
+
+	portBuf := make([]byte, 2)
+	if _, err := io.ReadFull(conn, portBuf); err != nil {
+		return "", err
+	}
+	port := binary.BigEndian.Uint16(portBuf)
+
+	return fmt.Sprintf("%s:%d", host, port), nil
+}
+
+// sendReply 发送响应
+func (s *SOCKS5Server) sendReply(conn net.Conn, rep byte) error {
+	// VER REP RSV ATYP BND.ADDR BND.PORT
+	reply := []byte{socks5Version, rep, 0x00, atypIPv4, 0, 0, 0, 0, 0, 0}
+	_, err := conn.Write(reply)
+	return err
+}