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jeremybenn |
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package proxy
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import (
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"errors"
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"io"
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"net"
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"strconv"
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)
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// SOCKS5 returns a Dialer that makes SOCKSv5 connections to the given address
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// with an optional username and password. See RFC 1928.
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func SOCKS5(network, addr string, auth *Auth, forward Dialer) (Dialer, error) {
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s := &socks5{
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network: network,
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addr: addr,
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forward: forward,
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}
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if auth != nil {
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s.user = auth.User
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s.password = auth.Password
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}
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return s, nil
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}
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type socks5 struct {
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user, password string
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network, addr string
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forward Dialer
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}
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const socks5Version = 5
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const (
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socks5AuthNone = 0
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socks5AuthPassword = 2
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)
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const socks5Connect = 1
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const (
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socks5IP4 = 1
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socks5Domain = 3
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socks5IP6 = 4
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)
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var socks5Errors = []string{
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"",
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"general failure",
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"connection forbidden",
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"network unreachable",
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"host unreachable",
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"connection refused",
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"TTL expired",
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"command not supported",
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"address type not supported",
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}
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// Dial connects to the address addr on the network net via the SOCKS5 proxy.
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func (s *socks5) Dial(network, addr string) (net.Conn, error) {
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switch network {
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case "tcp", "tcp6", "tcp4":
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break
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default:
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return nil, errors.New("proxy: no support for SOCKS5 proxy connections of type " + network)
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}
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conn, err := s.forward.Dial(s.network, s.addr)
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if err != nil {
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return nil, err
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}
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closeConn := &conn
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defer func() {
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if closeConn != nil {
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(*closeConn).Close()
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}
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}()
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host, portStr, err := net.SplitHostPort(addr)
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if err != nil {
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return nil, err
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}
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port, err := strconv.Atoi(portStr)
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if err != nil {
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return nil, errors.New("proxy: failed to parse port number: " + portStr)
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}
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if port < 1 || port > 0xffff {
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return nil, errors.New("proxy: port number out of range: " + portStr)
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}
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// the size here is just an estimate
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buf := make([]byte, 0, 6+len(host))
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buf = append(buf, socks5Version)
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if len(s.user) > 0 && len(s.user) < 256 && len(s.password) < 256 {
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buf = append(buf, 2, /* num auth methods */ socks5AuthNone, socks5AuthPassword)
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} else {
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buf = append(buf, 1, /* num auth methods */ socks5AuthNone)
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}
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if _, err = conn.Write(buf); err != nil {
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return nil, errors.New("proxy: failed to write greeting to SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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if _, err = io.ReadFull(conn, buf[:2]); err != nil {
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return nil, errors.New("proxy: failed to read greeting from SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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if buf[0] != 5 {
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return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " has unexpected version " + strconv.Itoa(int(buf[0])))
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}
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if buf[1] == 0xff {
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return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " requires authentication")
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}
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if buf[1] == socks5AuthPassword {
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buf = buf[:0]
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buf = append(buf, socks5Version)
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buf = append(buf, uint8(len(s.user)))
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buf = append(buf, s.user...)
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buf = append(buf, uint8(len(s.password)))
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buf = append(buf, s.password...)
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if _, err = conn.Write(buf); err != nil {
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return nil, errors.New("proxy: failed to write authentication request to SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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if _, err = io.ReadFull(conn, buf[:2]); err != nil {
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return nil, errors.New("proxy: failed to read authentication reply from SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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if buf[1] != 0 {
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return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " rejected username/password")
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}
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}
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buf = buf[:0]
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buf = append(buf, socks5Version, socks5Connect, 0 /* reserved */ )
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if ip := net.ParseIP(host); ip != nil {
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if len(ip) == 4 {
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buf = append(buf, socks5IP4)
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} else {
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buf = append(buf, socks5IP6)
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}
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buf = append(buf, []byte(ip)...)
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} else {
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buf = append(buf, socks5Domain)
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buf = append(buf, byte(len(host)))
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buf = append(buf, host...)
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}
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buf = append(buf, byte(port>>8), byte(port))
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if _, err = conn.Write(buf); err != nil {
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return nil, errors.New("proxy: failed to write connect request to SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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if _, err = io.ReadFull(conn, buf[:4]); err != nil {
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return nil, errors.New("proxy: failed to read connect reply from SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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failure := "unknown error"
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if int(buf[1]) < len(socks5Errors) {
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failure = socks5Errors[buf[1]]
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}
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if len(failure) > 0 {
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return nil, errors.New("proxy: SOCKS5 proxy at " + s.addr + " failed to connect: " + failure)
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}
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bytesToDiscard := 0
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switch buf[3] {
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case socks5IP4:
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bytesToDiscard = 4
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case socks5IP6:
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bytesToDiscard = 16
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case socks5Domain:
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_, err := io.ReadFull(conn, buf[:1])
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if err != nil {
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return nil, errors.New("proxy: failed to read domain length from SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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bytesToDiscard = int(buf[0])
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default:
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return nil, errors.New("proxy: got unknown address type " + strconv.Itoa(int(buf[3])) + " from SOCKS5 proxy at " + s.addr)
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}
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if cap(buf) < bytesToDiscard {
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buf = make([]byte, bytesToDiscard)
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} else {
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buf = buf[:bytesToDiscard]
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}
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if _, err = io.ReadFull(conn, buf); err != nil {
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return nil, errors.New("proxy: failed to read address from SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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// Also need to discard the port number
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if _, err = io.ReadFull(conn, buf[:2]); err != nil {
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return nil, errors.New("proxy: failed to read port from SOCKS5 proxy at " + s.addr + ": " + err.Error())
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}
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closeConn = nil
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return conn, nil
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}
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