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server.go
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server.go
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package socks5
import (
"context"
"io"
"net"
"sync"
"time"
)
// TODO: need a logger as well
const (
CmdDialTCP = 0x01
CmdBindTCP = 0x02
CmdForwardUDP = 0x03
)
//
// if Handler returned ErrUnsupportCommand, the server will reply with StatusCommandUnsupported
//
type Handler interface {
DialTCP(ctx context.Context, addr *AddrPort)(net.Conn, error)
BindTCP(ctx context.Context, addr *AddrPort)(net.Listener, error)
BindUDP(ctx context.Context, addr *AddrPort)(net.PacketConn, error)
}
const DefaultSocksPort = ":1080"
type Server struct {
Addr string
Handler Handler
// If UserGuarder is set, the Username/password auth mode will be enabled
UserGuarder UserGuarder
DialTimeout time.Duration
initMux sync.Mutex
ctx context.Context
cancel context.CancelFunc
}
func (s *Server)init(){
s.initMux.Lock()
defer s.initMux.Unlock()
if s.ctx == nil {
s.ctx, s.cancel = context.WithCancel(context.Background())
}
}
func (s *Server)Serve(listener net.Listener)(err error){
s.init()
done := make(chan struct{}, 0)
go func(){
select {
case <-done:
case <-s.ctx.Done():
listener.Close()
}
}()
defer close(done)
for {
var conn net.Conn
if conn, err = listener.Accept(); err != nil {
return
}
go s.Handle(conn)
}
}
func Serve(listener net.Listener, handler Handler)(err error){
server := &Server{
Handler: handler,
}
return server.Serve(listener)
}
func (s *Server)ListenAndServe()(err error){
addr := s.Addr
if addr == "" {
addr = DefaultSocksPort
}
listener, err := net.Listen("tcp", addr)
if err != nil {
return
}
return s.Serve(listener)
}
func ListenAndServe(addr string, handler Handler)(err error){
server := &Server{
Addr: addr,
Handler: handler,
}
return server.ListenAndServe()
}
func (s *Server)Shutdown(ctx context.Context)(err error){
s.cancel()
// TODO: wait for all connections closed
return
}
func (s *Server)tryAuth(c *conn, auth AuthType)(ok bool, err error){
// TODO: add custom auths
switch auth {
case NoAuth:
if _, err = c.Write([]byte{Socks5Version, auth}); err != nil {
return
}
return true, nil
case UserAuth:
if s.UserGuarder == nil {
return false, nil
}
var b byte
if b, err = c.ReadByte(); err != nil {
return
}
if b != 0x01 {
return true, ErrUnsupportVersion
}
if b, err = c.ReadByte(); err != nil {
return
}
id := make([]byte, b)
if _, err = io.ReadFull(c, id); err != nil {
return
}
if b, err = c.ReadByte(); err != nil {
return
}
pw := make([]byte, b)
if _, err = io.ReadFull(c, pw); err != nil {
return
}
if !s.UserGuarder.Auth((string)(id), (string)(pw)) {
if _, err = c.Write([]byte{0x01, 0xff}); err != nil {
return
}
return true, ErrUnauthorized
}
if _, err = c.Write([]byte{0x01, 0x00}); err != nil {
return
}
return true, nil
}
return false, nil
}
func (s *Server)Handle(netconn net.Conn)(err error){
defer netconn.Close()
var (
ctx context.Context
cancel context.CancelFunc
)
if s.DialTimeout > 0 {
ctx, cancel = context.WithTimeout(s.ctx, s.DialTimeout)
}else{
ctx, cancel = context.WithCancel(s.ctx)
}
defer cancel()
// begin handshake & auth
c := &conn{
Conn: netconn,
}
var auths []AuthType
if auths, err = c.readHandShake(); err != nil {
return
}
ok := false
for _, auth := range auths {
if ok, err = s.tryAuth(c, auth); err != nil {
return
}
if ok {
break
}
}
if !ok {
if _, err = c.Write([]byte{Socks5Version, noAcceptableAuth}); err != nil {
return
}
return ErrNoAcceptableAuth
}
// begin request
cmd, addr, err := c.readRequest()
if err != nil {
return c.sendErrorResponse(err)
}
switch cmd {
case CmdDialTCP:
var conn net.Conn
if conn, err = s.Handler.DialTCP(ctx, addr); err != nil {
return c.sendErrorResponse(err)
}
if err = c.sendResponse(StatusGranted, nil); err != nil {
return
}
go io.Copy(conn, c)
_, err = io.Copy(c, conn)
return
case CmdBindTCP:
var listener net.Listener
if listener, err = s.Handler.BindTCP(ctx, addr); err != nil {
return c.sendErrorResponse(err)
}
var ladr *AddrPort
if ladr, err = AddrPortFromNetAddr(listener.Addr()); err != nil {
// should never reach
return
}
if err = c.sendResponse(StatusGranted, ladr); err != nil {
return
}
var conn net.Conn
if conn, err = listener.Accept(); err != nil {
return c.sendErrorResponse(err)
}
var laddr *AddrPort
if laddr, err = AddrPortFromNetAddr(conn.LocalAddr()); err != nil {
// should never reach
return
}
if err = c.sendResponse(StatusGranted, laddr); err != nil {
return
}
go io.Copy(conn, c)
_, err = io.Copy(c, conn)
return
case CmdForwardUDP: // TODO
break
var conn net.PacketConn
if conn, err = s.Handler.BindUDP(ctx, addr); err != nil {
return c.sendErrorResponse(err)
}
var listenIP net.IP
switch addr.Type {
case IPv4Addr:
listenIP = net.IPv4(127, 0, 0, 1)
case IPv6Addr:
listenIP = net.IPv6loopback
default:
listenIP = net.IPv4(127, 0, 0, 1)
}
var lc *net.UDPConn
if lc, err = net.ListenUDP("udp", &net.UDPAddr{IP: listenIP}); err != nil {
return c.sendResponse(StatusCommandUnsupported, nil)
}
defer lc.Close()
var laddr *AddrPort
if laddr, err = AddrPortFromNetAddr(lc.LocalAddr()); err != nil {
// should never reach
return
}
if err = c.sendResponse(StatusGranted, laddr); err != nil {
return
}
go forwardPacket(conn, lc, nil) // TODO
go forwardPacket(lc, conn, nil)
readUntilClosed(c)
return
}
if err = c.sendResponse(StatusCommandUnsupported, nil); err != nil {
return
}
return
}