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@@ -0,0 +1,210 @@
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+// 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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+
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+package proxy
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+
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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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+
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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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+
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+ return s, nil
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+}
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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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+
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+const socks5Version = 5
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+
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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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+
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+const socks5Connect = 1
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+
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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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+
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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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+
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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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+ 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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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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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+
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+ if buf[1] == socks5AuthPassword {
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+ buf = buf[:0]
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+ buf = append(buf, 1 /* password protocol version */)
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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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+
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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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+
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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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+
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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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+
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+ buf = buf[:0]
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+ buf = append(buf, socks5Version, socks5Connect, 0 /* reserved */)
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+
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+ if ip := net.ParseIP(host); ip != nil {
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+ if ip4 := ip.To4(); ip4 != nil {
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+ buf = append(buf, socks5IP4)
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+ ip = ip4
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+ } else {
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+ buf = append(buf, socks5IP6)
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+ }
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+ buf = append(buf, ip...)
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+ } else {
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+ if len(host) > 255 {
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+ return nil, errors.New("proxy: destination hostname too long: " + host)
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+ }
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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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+
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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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+
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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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+
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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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+
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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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+
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+ bytesToDiscard := 0
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+ switch buf[3] {
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+ case socks5IP4:
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+ bytesToDiscard = net.IPv4len
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+ case socks5IP6:
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+ bytesToDiscard = net.IPv6len
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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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+
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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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+
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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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+
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+ closeConn = nil
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+ return conn, nil
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+}
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