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144 lines
2.4 KiB
Go
144 lines
2.4 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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/*
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socks4 protocol
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request
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byte | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ... |
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|0x04|cmd| port | ip | user\0 |
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reply
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byte | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7|
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|0x00|status| | |
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socks4a protocol
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request
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byte | 0 | 1 | 2 | 3 |4 | 5 | 6 | 7 | 8 | ... |... |
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|0x04|cmd| port | 0.0.0.x | user\0 |domain\0|
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reply
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byte | 0 | 1 | 2 | 3 | 4 | 5 | 6| 7 |
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|0x00|staus| port | ip |
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*/
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type socks4Conn struct {
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serverConn net.Conn
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clientConn 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.clientConn != nil {
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s4.clientConn.Close()
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}
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if s4.serverConn != nil {
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s4.serverConn.Close()
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}
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}
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func (s4 *socks4Conn) forward() {
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c := make(chan int, 2)
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go func() {
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io.Copy(s4.clientConn, s4.serverConn)
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c <- 1
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}()
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go func() {
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io.Copy(s4.serverConn, s4.clientConn)
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c <- 1
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}()
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<-c
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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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// read header
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n, err := io.ReadAtLeast(s4.clientConn, buf, 8)
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if err != nil {
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return err
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}
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// command only support connect
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if buf[0] != cmdConnect {
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return fmt.Errorf("error command %d", buf[0])
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}
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// get port
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port := binary.BigEndian.Uint16(buf[1:3])
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// get ip
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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.clientConn.Write([]byte{0x00, 0x5a, 0x01, 0x02, 0x00, 0x00, 0x00, 0x00})
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//log.Printf("connecting to %s\r\n", target)
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// connect to the target
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s4.serverConn, 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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