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106 lines
1.9 KiB
Go
106 lines
1.9 KiB
Go
package socks
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import (
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"encoding/binary"
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"fmt"
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"io"
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"log"
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"net"
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)
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type socks4Conn struct {
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server_conn net.Conn
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client_conn net.Conn
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dial dialFunc
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}
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func (s4 *socks4Conn) Serve() {
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defer s4.Close()
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if err := s4.processRequest(); err != nil {
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log.Println(err)
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return
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}
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}
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func (s4 *socks4Conn) Close() {
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if s4.client_conn != nil {
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s4.client_conn.Close()
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}
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if s4.server_conn != nil {
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s4.server_conn.Close()
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}
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}
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func (s4 *socks4Conn) forward() {
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go func() {
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io.Copy(s4.client_conn, s4.server_conn)
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}()
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io.Copy(s4.server_conn, s4.client_conn)
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}
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func (s4 *socks4Conn) processRequest() error {
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// version has already read out by socksConn.Serve()
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// process command and target here
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buf := make([]byte, 128)
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n, err := io.ReadAtLeast(s4.client_conn, buf, 8)
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if err != nil {
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return err
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}
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// only support connect
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if buf[0] != cmdConnect {
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return fmt.Errorf("error command %s", buf[0])
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}
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port := binary.BigEndian.Uint16(buf[1:3])
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ip := net.IP(buf[3:7])
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// NULL-terminated user string
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// jump to NULL character
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var j int
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for j = 7; j < n; j++ {
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if buf[j] == 0x00 {
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break
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}
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}
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host := ip.String()
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// socks4a
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// 0.0.0.x
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if ip[0] == 0x00 && ip[1] == 0x00 && ip[2] == 0x00 && ip[3] != 0x00 {
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j++
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var i = j
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// jump to the end of hostname
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for j = i; j < n; j++ {
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if buf[j] == 0x00 {
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break
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}
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}
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host = string(buf[i:j])
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}
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target := net.JoinHostPort(host, fmt.Sprintf("%d", port))
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// reply user with connect success
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// if dial to target failed, user will receive connection reset
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s4.client_conn.Write([]byte{0x00, 0x5a, 0x01, 0x02, 0x00, 0x00, 0x00, 0x00})
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log.Printf("connecting to %s", target)
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// connect to the target
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s4.server_conn, err = s4.dial("tcp", target)
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if err != nil {
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return err
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}
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// enter data exchange
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s4.forward()
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return nil
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}
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