/
gosocks.go
243 lines (219 loc) · 5.55 KB
/
gosocks.go
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package main
import (
"flag"
"io"
"log"
"net"
"os"
)
var (
flagPort = flag.Int("port", 1080, "listening port")
)
func main() {
flag.Parse()
addr := &net.TCPAddr{IP: []byte{0, 0, 0, 0}, Port: *flagPort}
listener, err := net.ListenTCP("tcp", addr)
if err != nil {
log.Fatalf("Failed to listen on port %d: %v", *flagPort, err)
}
for {
client, err := listener.AcceptTCP()
if err != nil {
log.Fatalf("Failed to accept new client connection: %v", err)
e := err.(net.Error)
if !e.Temporary() {
os.Exit(1)
}
}
go clientLoop(client)
}
}
func clientLoop(client *net.TCPConn) {
addr := client.RemoteAddr()
defer client.Close()
var versionMethod [2]byte
_, err := io.ReadFull(client, versionMethod[:])
if err != nil {
log.Printf("%v: Failed to read the version and methods number: %v", addr, err)
return
}
if versionMethod[0] != 0x05 {
log.Printf("%v: Only implemented socks5 proxy currently: %X.", addr, versionMethod[0])
return
}
nMethods := versionMethod[1]
if nMethods == 0 {
log.Printf("%v: Must provide one method at least.", addr)
return
}
methods := make([]byte, nMethods)
_, err = io.ReadFull(client, methods)
if err != nil {
log.Printf("%v: Failed to read the methods: %v", addr, err)
return
}
hasMethod0 := false
for i := 0; i < int(nMethods); i++ {
if methods[i] == 0x00 {
hasMethod0 = true
break
}
}
if !hasMethod0 {
log.Printf("%v: Only implemented 'no authentication required' method currently.", addr)
return
}
versionMethod[1] = 0x00
nw, err := client.Write(versionMethod[:])
if err != nil || nw != len(versionMethod) {
log.Printf("%v: Failed to write version and method back to the client: %v", addr, err)
return
}
var requestHeader [4]byte
_, err = io.ReadFull(client, requestHeader[:])
if err != nil {
log.Printf("%v: Failed to read the request header: %v", addr, err)
return
}
var reply [22]byte
reply[0] = 0x05 // VER
reply[2] = 0x00 // RSV
if requestHeader[0] != 0x05 {
log.Printf("%v: Version number in the request does not match the previous one: %X", addr, requestHeader[0])
return
}
if requestHeader[1] != 0x01 {
log.Printf("%v: Only implemented CONNECT command currently.", addr)
reply[1] = 0x07
client.Write(reply[:4])
return
}
if requestHeader[2] != 0x00 {
log.Printf("%v: RESERVED field must be 0.", addr)
return
}
remoteAddress := new(net.TCPAddr)
switch requestHeader[3] {
case 0x01, 0x04:
{
ipLen := 4 * requestHeader[3]
buf := make([]byte, ipLen+2)
_, err = io.ReadFull(client, buf)
if err != nil {
log.Printf("%v: Failed to read requested address: %v", addr, err)
return
}
remoteAddress.IP = buf[:ipLen]
remoteAddress.Port = int(buf[ipLen])<<8 + int(buf[ipLen+1])
reply[3] = requestHeader[3]
}
case 0x03:
{
var hostLen [1]byte
_, err = io.ReadFull(client, hostLen[:])
if err != nil {
log.Printf("%v: Failed to read requested host len: %v", addr, err)
return
}
host := make([]byte, hostLen[0])
_, err = io.ReadFull(client, host)
if err != nil {
log.Printf("%v: Failed to read requested host name: %v", addr, err)
return
}
ips, err := net.LookupIP(string(host))
if err != nil {
log.Printf("%v: Failed to resolve requested host: %v", addr, err)
return
}
if len(ips) == 0 {
log.Printf("%v: There is no IP address corresponding to host '%s'.", addr, host)
return
}
remoteAddress.IP = ips[0]
reply[3] = len(ips[0]) / 4
var port [2]byte
_, err = io.ReadFull(client, port[:])
if err != nil {
log.Printf("%v: Failed to read requested port: %v", addr, err)
return
}
remoteAddress.Port = int(port[0])<<8 + int(port[1])
}
default:
log.Printf("%v: unknown address type: %X", addr, requestHeader[3])
reply[1] = 0x08
client.Write(reply[:4])
return
}
log.Printf("%v: Requested address: %v", addr, remoteAddress)
remote, err := net.DialTCP("tcp", nil, remoteAddress)
if err != nil {
log.Printf("%v: Failed to connect to the requested address: %v", addr, err)
reply[1] = 0x05
client.Write(reply[:6])
return
}
defer remote.Close()
reply[1] = 0x00
ipEnd := 4 + 4*reply[3]
copy(reply[4:ipEnd], remoteAddress.IP)
reply[ipEnd] = byte(remoteAddress.Port >> 8)
reply[ipEnd+1] = byte(remoteAddress.Port % 256)
_, err = client.Write(reply[:ipEnd+2])
if err != nil {
log.Printf("%v: Failed to write reply: %v", addr, err)
return
}
stopChan := make(chan bool)
go readClientLoop(client, remote, stopChan)
go readRemoteLoop(client, remote, stopChan)
_ = <-stopChan
_ = <-stopChan
}
func readClientLoop(client, remote *net.TCPConn, stopChan chan<- bool) {
defer func() {
stopChan <- true
}()
addr := client.RemoteAddr()
for {
var buf [4096]byte
nr, err := client.Read(buf[:])
if err != nil && err != os.EOF {
log.Printf("%v: Failed to read from the client: %v", addr, err)
return
}
start := 0
for start < nr {
nw, err := remote.Write(buf[start:nr])
if err != nil && err != os.EOF {
log.Printf("%v: Failed to write to the remote: %v", addr, err)
return
}
start += nw
}
}
}
func readRemoteLoop(client, remote *net.TCPConn, stopChan chan<- bool) {
defer func() {
stopChan <- true
}()
addr := client.RemoteAddr()
for {
var buf [4096]byte
nr, err := remote.Read(buf[:])
if err != nil && err != os.EOF {
log.Printf("%v: Failed to read from the remote: %v", addr, err)
return
}
start := 0
for start < nr {
nw, err := client.Write(buf[start:nr])
if err != nil && err != os.EOF {
log.Printf("%v: Failed to write to the client: %v", addr, err)
return
}
start += nw
}
}
}