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- // Copyright 2012, Hailiang Wang. All rights reserved.
- // Use of this source code is governed by a BSD-style
- // license that can be found in the LICENSE file.
-
- /*
- Package socks implements a SOCKS (SOCKS4, SOCKS4A and SOCKS5) proxy client.
-
- A complete example using this package:
- package main
-
- import (
- "code.as/core/socks"
- "fmt"
- "net/http"
- "io/ioutil"
- )
-
- func main() {
- dialSocksProxy := socks.DialSocksProxy(socks.SOCKS5, "127.0.0.1:1080")
- tr := &http.Transport{Dial: dialSocksProxy}
- httpClient := &http.Client{Transport: tr}
-
- bodyText, err := TestHttpsGet(httpClient, "https://h12.io/about")
- if err != nil {
- fmt.Println(err.Error())
- }
- fmt.Print(bodyText)
- }
-
- func TestHttpsGet(c *http.Client, url string) (bodyText string, err error) {
- resp, err := c.Get(url)
- if err != nil { return }
- defer resp.Body.Close()
-
- body, err := ioutil.ReadAll(resp.Body)
- if err != nil { return }
- bodyText = string(body)
- return
- }
- */
- package socks
-
- import (
- "errors"
- "fmt"
- "net"
- "strconv"
- )
-
- // Constants to choose which version of SOCKS protocol to use.
- const (
- SOCKS4 = iota
- SOCKS4A
- SOCKS5
- )
-
- // DialSocksProxy returns the dial function to be used in http.Transport object.
- // Argument socksType should be one of SOCKS4, SOCKS4A and SOCKS5.
- // Argument proxy should be in this format "127.0.0.1:1080".
- func DialSocksProxy(socksType int, proxy string) func(string, string) (net.Conn, error) {
- if socksType == SOCKS5 {
- return func(_, targetAddr string) (conn net.Conn, err error) {
- return dialSocks5(proxy, targetAddr)
- }
- }
-
- // SOCKS4, SOCKS4A
- return func(_, targetAddr string) (conn net.Conn, err error) {
- return dialSocks4(socksType, proxy, targetAddr)
- }
- }
-
- func dialSocks5(proxy, targetAddr string) (conn net.Conn, err error) {
- // dial TCP
- conn, err = net.Dial("tcp", proxy)
- if err != nil {
- return
- }
-
- // version identifier/method selection request
- req := []byte{
- 5, // version number
- 1, // number of methods
- 0, // method 0: no authentication (only anonymous access supported for now)
- }
- resp, err := sendReceive(conn, req)
- if err != nil {
- return
- } else if len(resp) != 2 {
- err = errors.New("Server does not respond properly.")
- return
- } else if resp[0] != 5 {
- err = errors.New("Server does not support Socks 5.")
- return
- } else if resp[1] != 0 { // no auth
- err = errors.New("socks method negotiation failed.")
- return
- }
-
- // detail request
- host, port, err := splitHostPort(targetAddr)
- req = []byte{
- 5, // version number
- 1, // connect command
- 0, // reserved, must be zero
- 3, // address type, 3 means domain name
- byte(len(host)), // address length
- }
- req = append(req, []byte(host)...)
- req = append(req, []byte{
- byte(port >> 8), // higher byte of destination port
- byte(port), // lower byte of destination port (big endian)
- }...)
- resp, err = sendReceive(conn, req)
- if err != nil {
- return
- } else if len(resp) != 10 {
- err = errors.New("Server does not respond properly.")
- } else if resp[1] != 0 {
- err = errors.New("Can't complete SOCKS5 connection.")
- }
-
- return
- }
-
- func dialSocks4(socksType int, proxy, targetAddr string) (conn net.Conn, err error) {
- // dial TCP
- conn, err = net.Dial("tcp", proxy)
- if err != nil {
- return
- }
-
- // connection request
- host, port, err := splitHostPort(targetAddr)
- if err != nil {
- return
- }
- ip := net.IPv4(0, 0, 0, 1).To4()
- if socksType == SOCKS4 {
- ip, err = lookupIP(host)
- if err != nil {
- return
- }
- }
- req := []byte{
- 4, // version number
- 1, // command CONNECT
- byte(port >> 8), // higher byte of destination port
- byte(port), // lower byte of destination port (big endian)
- ip[0], ip[1], ip[2], ip[3], // special invalid IP address to indicate the host name is provided
- 0, // user id is empty, anonymous proxy only
- }
- if socksType == SOCKS4A {
- req = append(req, []byte(host+"\x00")...)
- }
-
- resp, err := sendReceive(conn, req)
- if err != nil {
- return
- } else if len(resp) != 8 {
- err = errors.New("Server does not respond properly.")
- return
- }
- switch resp[1] {
- case 90:
- // request granted
- case 91:
- err = errors.New("Socks connection request rejected or failed.")
- case 92:
- err = errors.New("Socks connection request rejected becasue SOCKS server cannot connect to identd on the client.")
- case 93:
- err = errors.New("Socks connection request rejected because the client program and identd report different user-ids.")
- default:
- err = errors.New("Socks connection request failed, unknown error.")
- }
- return
- }
-
- func sendReceive(conn net.Conn, req []byte) (resp []byte, err error) {
- _, err = conn.Write(req)
- if err != nil {
- return
- }
- resp, err = readAll(conn)
- return
- }
-
- func readAll(conn net.Conn) (resp []byte, err error) {
- resp = make([]byte, 1024)
- n, err := conn.Read(resp)
- resp = resp[:n]
- return
- }
-
- func lookupIP(host string) (ip net.IP, err error) {
- ips, err := net.LookupIP(host)
- if err != nil {
- return
- }
- if len(ips) == 0 {
- err = errors.New(fmt.Sprintf("Cannot resolve host: %s.", host))
- return
- }
- ip = ips[0].To4()
- if len(ip) != net.IPv4len {
- fmt.Println(len(ip), ip)
- err = errors.New("IPv6 is not supported by SOCKS4.")
- return
- }
- return
- }
-
- func splitHostPort(addr string) (host string, port uint16, err error) {
- host, portStr, err := net.SplitHostPort(addr)
- portInt, err := strconv.ParseUint(portStr, 10, 16)
- port = uint16(portInt)
- return
- }
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