コード例 #1
0
ファイル: output.go プロジェクト: xyz12810/v2ray-core
func (this *AuthenticationWriter) Write(payload *alloc.Buffer) error {
	defer payload.Release()

	this.Authenticator.Seal(payload)
	_, err := this.Writer.Write(payload.Value)
	return err
}
コード例 #2
0
ファイル: crypt.go プロジェクト: DZLZHCODE/v2ray-core
func (this *SimpleAuthenticator) Open(buffer *alloc.Buffer) bool {
	len := buffer.Len()
	xtra := 4 - len%4
	if xtra != 0 {
		buffer.Slice(0, len+xtra)
	}
	xorbkd(buffer.Value)
	if xtra != 0 {
		buffer.Slice(0, len)
	}

	fnvHash := fnv.New32a()
	fnvHash.Write(buffer.Value[4:])
	if serial.BytesToUint32(buffer.Value[:4]) != fnvHash.Sum32() {
		return false
	}

	length := serial.BytesToUint16(buffer.Value[4:6])
	if buffer.Len()-6 != int(length) {
		return false
	}

	buffer.SliceFrom(6)

	return true
}
コード例 #3
0
func (this *OutboundConnectionHandler) Dispatch(destination v2net.Destination, payload *alloc.Buffer, ray ray.OutboundRay) error {
	input := ray.OutboundInput()
	output := ray.OutboundOutput()

	this.Destination = destination
	if !payload.IsEmpty() {
		this.ConnOutput.Write(payload.Value)
	}
	payload.Release()

	writeFinish := &sync.Mutex{}

	writeFinish.Lock()

	go func() {
		v2writer := v2io.NewAdaptiveWriter(this.ConnOutput)
		defer v2writer.Release()

		v2io.Pipe(input, v2writer)
		writeFinish.Unlock()
		input.Release()
	}()

	writeFinish.Lock()

	v2reader := v2io.NewAdaptiveReader(this.ConnInput)
	defer v2reader.Release()

	v2io.Pipe(v2reader, output)
	output.Close()

	return nil
}
コード例 #4
0
ファイル: outbound.go プロジェクト: DZLZHCODE/v2ray-core
func (this *VMessOutboundHandler) handleRequest(session *encoding.ClientSession, conn internet.Connection, request *protocol.RequestHeader, payload *alloc.Buffer, input v2io.Reader, finish *sync.Mutex) {
	defer finish.Unlock()

	writer := v2io.NewBufferedWriter(conn)
	defer writer.Release()
	session.EncodeRequestHeader(request, writer)

	bodyWriter := session.EncodeRequestBody(writer)
	var streamWriter v2io.Writer = v2io.NewAdaptiveWriter(bodyWriter)
	if request.Option.Has(protocol.RequestOptionChunkStream) {
		streamWriter = vmessio.NewAuthChunkWriter(streamWriter)
	}
	if !payload.IsEmpty() {
		if err := streamWriter.Write(payload); err != nil {
			conn.SetReusable(false)
		}
	}
	writer.SetCached(false)

	err := v2io.Pipe(input, streamWriter)
	if err != io.EOF {
		conn.SetReusable(false)
	}

	if request.Option.Has(protocol.RequestOptionChunkStream) {
		err := streamWriter.Write(alloc.NewLocalBuffer(32).Clear())
		if err != nil {
			conn.SetReusable(false)
		}
	}
	streamWriter.Release()
	return
}
コード例 #5
0
ファイル: freedom.go プロジェクト: xyz12810/v2ray-core
func (this *FreedomConnection) Dispatch(destination v2net.Destination, payload *alloc.Buffer, ray ray.OutboundRay) error {
	log.Info("Freedom: Opening connection to ", destination)

	defer payload.Release()
	defer ray.OutboundInput().Release()
	defer ray.OutboundOutput().Close()

	var conn internet.Connection
	if this.domainStrategy == Config_USE_IP && destination.Address.Family().IsDomain() {
		destination = this.ResolveIP(destination)
	}
	err := retry.ExponentialBackoff(5, 100).On(func() error {
		rawConn, err := internet.Dial(this.meta.Address, destination, this.meta.GetDialerOptions())
		if err != nil {
			return err
		}
		conn = rawConn
		return nil
	})
	if err != nil {
		log.Warning("Freedom: Failed to open connection to ", destination, ": ", err)
		return err
	}
	defer conn.Close()

	input := ray.OutboundInput()
	output := ray.OutboundOutput()

	if !payload.IsEmpty() {
		conn.Write(payload.Value)
	}

	go func() {
		v2writer := v2io.NewAdaptiveWriter(conn)
		defer v2writer.Release()

		v2io.Pipe(input, v2writer)
		if tcpConn, ok := conn.(*tcp.RawConnection); ok {
			tcpConn.CloseWrite()
		}
	}()

	var reader io.Reader = conn

	timeout := this.timeout
	if destination.Network == v2net.Network_UDP {
		timeout = 16
	}
	if timeout > 0 {
		reader = v2net.NewTimeOutReader(timeout /* seconds */, conn)
	}

	v2reader := v2io.NewAdaptiveReader(reader)
	v2io.Pipe(v2reader, output)
	v2reader.Release()
	ray.OutboundOutput().Close()

	return nil
}
コード例 #6
0
ファイル: dokodemo.go プロジェクト: DZLZHCODE/v2ray-core
func (this *DokodemoDoor) handleUDPResponse(dest v2net.Destination, payload *alloc.Buffer) {
	defer payload.Release()
	this.udpMutex.RLock()
	defer this.udpMutex.RUnlock()
	if !this.accepting {
		return
	}
	this.udpHub.WriteTo(payload.Value, dest)
}
コード例 #7
0
ファイル: blackhole.go プロジェクト: xyz12810/v2ray-core
func (this *BlackHole) Dispatch(destination v2net.Destination, payload *alloc.Buffer, ray ray.OutboundRay) error {
	payload.Release()

	this.response.WriteTo(ray.OutboundOutput())
	ray.OutboundOutput().Close()

	ray.OutboundInput().Release()

	return nil
}
コード例 #8
0
ファイル: listener.go プロジェクト: xyz12810/v2ray-core
func (this *Listener) OnReceive(payload *alloc.Buffer, session *proxy.SessionInfo) {
	defer payload.Release()

	src := session.Source

	if valid := this.authenticator.Open(payload); !valid {
		log.Info("KCP|Listener: discarding invalid payload from ", src)
		return
	}
	if !this.running {
		return
	}
	this.Lock()
	defer this.Unlock()
	if !this.running {
		return
	}
	if payload.Len() < 4 {
		return
	}
	conv := serial.BytesToUint16(payload.Value)
	cmd := Command(payload.Value[2])
	sourceId := src.NetAddr() + "|" + serial.Uint16ToString(conv)
	conn, found := this.sessions[sourceId]
	if !found {
		if cmd == CommandTerminate {
			return
		}
		log.Debug("KCP|Listener: Creating session with id(", sourceId, ") from ", src)
		writer := &Writer{
			id:       sourceId,
			hub:      this.hub,
			dest:     src,
			listener: this,
		}
		srcAddr := &net.UDPAddr{
			IP:   src.Address.IP(),
			Port: int(src.Port),
		}
		auth, err := this.config.GetAuthenticator()
		if err != nil {
			log.Error("KCP|Listener: Failed to create authenticator: ", err)
		}
		conn = NewConnection(conv, writer, this.Addr().(*net.UDPAddr), srcAddr, auth, this.config)
		select {
		case this.awaitingConns <- conn:
		case <-time.After(time.Second * 5):
			conn.Close()
			return
		}
		this.sessions[sourceId] = conn
	}
	conn.Input(payload.Value)
}
コード例 #9
0
ファイル: server_udp.go プロジェクト: DZLZHCODE/v2ray-core
func (this *Server) handleUDPPayload(payload *alloc.Buffer, session *proxy.SessionInfo) {
	source := session.Source
	log.Info("Socks: Client UDP connection from ", source)
	request, err := protocol.ReadUDPRequest(payload.Value)
	payload.Release()

	if err != nil {
		log.Error("Socks: Failed to parse UDP request: ", err)
		return
	}
	if request.Data.Len() == 0 {
		request.Data.Release()
		return
	}
	if request.Fragment != 0 {
		log.Warning("Socks: Dropping fragmented UDP packets.")
		// TODO handle fragments
		request.Data.Release()
		return
	}

	log.Info("Socks: Send packet to ", request.Destination(), " with ", request.Data.Len(), " bytes")
	log.Access(source, request.Destination, log.AccessAccepted, "")
	this.udpServer.Dispatch(&proxy.SessionInfo{Source: source, Destination: request.Destination()}, request.Data, func(destination v2net.Destination, payload *alloc.Buffer) {
		response := &protocol.Socks5UDPRequest{
			Fragment: 0,
			Address:  request.Destination().Address(),
			Port:     request.Destination().Port(),
			Data:     payload,
		}
		log.Info("Socks: Writing back UDP response with ", payload.Len(), " bytes to ", destination)

		udpMessage := alloc.NewLocalBuffer(2048).Clear()
		response.Write(udpMessage)

		this.udpMutex.RLock()
		if !this.accepting {
			this.udpMutex.RUnlock()
			return
		}
		nBytes, err := this.udpHub.WriteTo(udpMessage.Value, destination)
		this.udpMutex.RUnlock()
		udpMessage.Release()
		response.Data.Release()
		if err != nil {
			log.Error("Socks: failed to write UDP message (", nBytes, " bytes) to ", destination, ": ", err)
		}
	})
}
コード例 #10
0
ファイル: ota.go プロジェクト: xyz12810/v2ray-core
func (this *ChunkWriter) Write(payload *alloc.Buffer) error {
	totalLength := payload.Len()
	payload.SliceBack(AuthSize)
	this.auth.Authenticate(payload.Value[:0], payload.Value[AuthSize:])
	payload.PrependUint16(uint16(totalLength))
	_, err := this.writer.Write(payload.Bytes())
	return err
}
コード例 #11
0
ファイル: writer.go プロジェクト: DZLZHCODE/v2ray-core
func Authenticate(buffer *alloc.Buffer) {
	fnvHash := fnv.New32a()
	fnvHash.Write(buffer.Value)
	buffer.PrependHash(fnvHash)

	buffer.PrependUint16(uint16(buffer.Len()))
}
コード例 #12
0
ファイル: writer.go プロジェクト: DZLZHCODE/v2ray-core
// Write implements Writer.Write(). Write() takes ownership of the given buffer.
func (this *AdaptiveWriter) Write(buffer *alloc.Buffer) error {
	defer buffer.Release()
	for !buffer.IsEmpty() {
		nBytes, err := this.writer.Write(buffer.Value)
		if err != nil {
			return err
		}
		buffer.SliceFrom(nBytes)
	}
	return nil
}
コード例 #13
0
ファイル: server.go プロジェクト: xyz12810/v2ray-core
func (this *Server) handlerUDPPayload(payload *alloc.Buffer, session *proxy.SessionInfo) {
	source := session.Source
	request, data, err := DecodeUDPPacket(this.user, payload)
	if err != nil {
		log.Info("Shadowsocks|Server: Skipping invalid UDP packet from: ", source, ": ", err)
		log.Access(source, "", log.AccessRejected, err)
		payload.Release()
		return
	}

	if request.Option.Has(RequestOptionOneTimeAuth) && this.account.OneTimeAuth == Account_Disabled {
		log.Info("Shadowsocks|Server: Client payload enables OTA but server doesn't allow it.")
		payload.Release()
		return
	}

	if !request.Option.Has(RequestOptionOneTimeAuth) && this.account.OneTimeAuth == Account_Enabled {
		log.Info("Shadowsocks|Server: Client payload disables OTA but server forces it.")
		payload.Release()
		return
	}

	dest := request.Destination()
	log.Access(source, dest, log.AccessAccepted, "")
	log.Info("Shadowsocks|Server: Tunnelling request to ", dest)

	this.udpServer.Dispatch(&proxy.SessionInfo{Source: source, Destination: dest, User: request.User, Inbound: this.meta}, data, func(destination v2net.Destination, payload *alloc.Buffer) {
		defer payload.Release()

		data, err := EncodeUDPPacket(request, payload)
		if err != nil {
			log.Warning("Shadowsocks|Server: Failed to encode UDP packet: ", err)
			return
		}
		defer data.Release()

		this.udpHub.WriteTo(data.Value, source)
	})
}
コード例 #14
0
ファイル: reader.go プロジェクト: DZLZHCODE/v2ray-core
func (this *AuthChunkReader) Read() (*alloc.Buffer, error) {
	var buffer *alloc.Buffer
	if this.last != nil {
		buffer = this.last
		this.last = nil
	} else {
		buffer = alloc.NewBufferWithSize(4096).Clear()
	}

	if this.chunkLength == -1 {
		for buffer.Len() < 6 {
			_, err := buffer.FillFrom(this.reader)
			if err != nil {
				buffer.Release()
				return nil, io.ErrUnexpectedEOF
			}
		}
		length := serial.BytesToUint16(buffer.Value[:2])
		this.chunkLength = int(length) - 4
		this.validator = NewValidator(serial.BytesToUint32(buffer.Value[2:6]))
		buffer.SliceFrom(6)
		if buffer.Len() < this.chunkLength && this.chunkLength <= 2048 {
			_, err := buffer.FillFrom(this.reader)
			if err != nil {
				buffer.Release()
				return nil, io.ErrUnexpectedEOF
			}
		}
	} else if buffer.Len() < this.chunkLength {
		_, err := buffer.FillFrom(this.reader)
		if err != nil {
			buffer.Release()
			return nil, io.ErrUnexpectedEOF
		}
	}

	if this.chunkLength == 0 {
		buffer.Release()
		return nil, io.EOF
	}

	if buffer.Len() < this.chunkLength {
		this.validator.Consume(buffer.Value)
		this.chunkLength -= buffer.Len()
	} else {
		this.validator.Consume(buffer.Value[:this.chunkLength])
		if !this.validator.Validate() {
			buffer.Release()
			return nil, transport.ErrCorruptedPacket
		}
		leftLength := buffer.Len() - this.chunkLength
		if leftLength > 0 {
			this.last = alloc.NewBufferWithSize(leftLength + 4096).Clear()
			this.last.Append(buffer.Value[this.chunkLength:])
			buffer.Slice(0, this.chunkLength)
		}

		this.chunkLength = -1
		this.validator = nil
	}

	return buffer, nil
}
コード例 #15
0
ファイル: srtp.go プロジェクト: xyz12810/v2ray-core
func (this *SRTP) Seal(payload *alloc.Buffer) {
	this.number++
	payload.PrependUint16(this.number)
	payload.PrependUint16(this.header)
}
コード例 #16
0
ファイル: server.go プロジェクト: DZLZHCODE/v2ray-core
func (this *Server) handlerUDPPayload(payload *alloc.Buffer, session *proxy.SessionInfo) {
	defer payload.Release()

	source := session.Source
	ivLen := this.config.Cipher.IVSize()
	iv := payload.Value[:ivLen]
	key := this.config.Key
	payload.SliceFrom(ivLen)

	stream, err := this.config.Cipher.NewDecodingStream(key, iv)
	if err != nil {
		log.Error("Shadowsocks: Failed to create decoding stream: ", err)
		return
	}

	reader := crypto.NewCryptionReader(stream, payload)

	request, err := ReadRequest(reader, NewAuthenticator(HeaderKeyGenerator(key, iv)), true)
	if err != nil {
		if err != io.EOF {
			log.Access(source, "", log.AccessRejected, err)
			log.Warning("Shadowsocks: Invalid request from ", source, ": ", err)
		}
		return
	}
	//defer request.Release()

	dest := v2net.UDPDestination(request.Address, request.Port)
	log.Access(source, dest, log.AccessAccepted, "")
	log.Info("Shadowsocks: Tunnelling request to ", dest)

	this.udpServer.Dispatch(&proxy.SessionInfo{Source: source, Destination: dest}, request.DetachUDPPayload(), func(destination v2net.Destination, payload *alloc.Buffer) {
		defer payload.Release()

		response := alloc.NewBuffer().Slice(0, ivLen)
		defer response.Release()

		rand.Read(response.Value)
		respIv := response.Value

		stream, err := this.config.Cipher.NewEncodingStream(key, respIv)
		if err != nil {
			log.Error("Shadowsocks: Failed to create encoding stream: ", err)
			return
		}

		writer := crypto.NewCryptionWriter(stream, response)

		switch request.Address.Family() {
		case v2net.AddressFamilyIPv4:
			writer.Write([]byte{AddrTypeIPv4})
			writer.Write(request.Address.IP())
		case v2net.AddressFamilyIPv6:
			writer.Write([]byte{AddrTypeIPv6})
			writer.Write(request.Address.IP())
		case v2net.AddressFamilyDomain:
			writer.Write([]byte{AddrTypeDomain, byte(len(request.Address.Domain()))})
			writer.Write([]byte(request.Address.Domain()))
		}

		writer.Write(request.Port.Bytes(nil))
		writer.Write(payload.Value)

		if request.OTA {
			respAuth := NewAuthenticator(HeaderKeyGenerator(key, respIv))
			respAuth.Authenticate(response.Value, response.Value[ivLen:])
		}

		this.udpHub.WriteTo(response.Value, source)
	})
}
コード例 #17
0
ファイル: client.go プロジェクト: xyz12810/v2ray-core
func (this *Client) Dispatch(destination v2net.Destination, payload *alloc.Buffer, ray ray.OutboundRay) error {
	defer payload.Release()
	defer ray.OutboundInput().Release()
	defer ray.OutboundOutput().Close()

	network := destination.Network

	var server *protocol.ServerSpec
	var conn internet.Connection

	err := retry.ExponentialBackoff(5, 100).On(func() error {
		server = this.serverPicker.PickServer()
		dest := server.Destination()
		dest.Network = network
		rawConn, err := internet.Dial(this.meta.Address, dest, this.meta.GetDialerOptions())
		if err != nil {
			return err
		}
		conn = rawConn

		return nil
	})
	if err != nil {
		return errors.New("Shadowsocks|Client: Failed to find an available destination:" + err.Error())
	}
	log.Info("Shadowsocks|Client: Tunneling request to ", destination, " via ", server.Destination())

	conn.SetReusable(false)

	request := &protocol.RequestHeader{
		Version: Version,
		Address: destination.Address,
		Port:    destination.Port,
	}
	if destination.Network == v2net.Network_TCP {
		request.Command = protocol.RequestCommandTCP
	} else {
		request.Command = protocol.RequestCommandUDP
	}

	user := server.PickUser()
	rawAccount, err := user.GetTypedAccount()
	if err != nil {
		return errors.New("Shadowsocks|Client: Failed to get a valid user account: " + err.Error())
	}
	account := rawAccount.(*ShadowsocksAccount)
	request.User = user

	if account.OneTimeAuth == Account_Auto || account.OneTimeAuth == Account_Enabled {
		request.Option |= RequestOptionOneTimeAuth
	}

	if request.Command == protocol.RequestCommandTCP {
		bufferedWriter := v2io.NewBufferedWriter(conn)
		defer bufferedWriter.Release()

		bodyWriter, err := WriteTCPRequest(request, bufferedWriter)
		defer bodyWriter.Release()

		if err != nil {
			return errors.New("Shadowsock|Client: Failed to write request: " + err.Error())
		}

		if err := bodyWriter.Write(payload); err != nil {
			return errors.New("Shadowsocks|Client: Failed to write payload: " + err.Error())
		}

		var responseMutex sync.Mutex
		responseMutex.Lock()

		go func() {
			defer responseMutex.Unlock()

			responseReader, err := ReadTCPResponse(user, conn)
			if err != nil {
				log.Warning("Shadowsocks|Client: Failed to read response: " + err.Error())
				return
			}

			v2io.Pipe(responseReader, ray.OutboundOutput())
		}()

		bufferedWriter.SetCached(false)
		v2io.Pipe(ray.OutboundInput(), bodyWriter)

		responseMutex.Lock()
	}

	if request.Command == protocol.RequestCommandUDP {
		timedReader := v2net.NewTimeOutReader(16, conn)
		var responseMutex sync.Mutex
		responseMutex.Lock()

		go func() {
			defer responseMutex.Unlock()

			reader := &UDPReader{
				Reader: timedReader,
				User:   user,
			}

			v2io.Pipe(reader, ray.OutboundOutput())
		}()

		writer := &UDPWriter{
			Writer:  conn,
			Request: request,
		}
		if !payload.IsEmpty() {
			if err := writer.Write(payload); err != nil {
				return errors.New("Shadowsocks|Client: Failed to write payload: " + err.Error())
			}
		}
		v2io.Pipe(ray.OutboundInput(), writer)

		responseMutex.Lock()
	}

	return nil
}
コード例 #18
0
ファイル: utp.go プロジェクト: DZLZHCODE/v2ray-core
func (this *UTP) Seal(payload *alloc.Buffer) {
	payload.PrependUint16(this.connectionId)
	payload.PrependBytes(this.header, this.extension)
}
コード例 #19
0
ファイル: protocol.go プロジェクト: xyz12810/v2ray-core
func DecodeUDPPacket(user *protocol.User, payload *alloc.Buffer) (*protocol.RequestHeader, *alloc.Buffer, error) {
	rawAccount, err := user.GetTypedAccount()
	if err != nil {
		return nil, nil, errors.New("Shadowsocks|UDP: Failed to parse account: " + err.Error())
	}
	account := rawAccount.(*ShadowsocksAccount)

	ivLen := account.Cipher.IVSize()
	iv := payload.Value[:ivLen]
	payload.SliceFrom(ivLen)

	stream, err := account.Cipher.NewDecodingStream(account.Key, iv)
	if err != nil {
		return nil, nil, errors.New("Shadowsocks|UDP: Failed to initialize decoding stream: " + err.Error())
	}
	stream.XORKeyStream(payload.Value, payload.Value)

	authenticator := NewAuthenticator(HeaderKeyGenerator(account.Key, iv))
	request := &protocol.RequestHeader{
		Version: Version,
		User:    user,
		Command: protocol.RequestCommandUDP,
	}

	addrType := (payload.Value[0] & 0x0F)
	if (payload.Value[0] & 0x10) == 0x10 {
		request.Option |= RequestOptionOneTimeAuth
	}

	if request.Option.Has(RequestOptionOneTimeAuth) {
		payloadLen := payload.Len() - AuthSize
		authBytes := payload.Value[payloadLen:]

		actualAuth := authenticator.Authenticate(nil, payload.Value[0:payloadLen])
		if !bytes.Equal(actualAuth, authBytes) {
			return nil, nil, errors.New("Shadowsocks|UDP: Invalid OTA.")
		}

		payload.Slice(0, payloadLen)
	}

	payload.SliceFrom(1)

	switch addrType {
	case AddrTypeIPv4:
		request.Address = v2net.IPAddress(payload.Value[:4])
		payload.SliceFrom(4)
	case AddrTypeIPv6:
		request.Address = v2net.IPAddress(payload.Value[:16])
		payload.SliceFrom(16)
	case AddrTypeDomain:
		domainLength := int(payload.Value[0])
		request.Address = v2net.DomainAddress(string(payload.Value[1 : 1+domainLength]))
		payload.SliceFrom(1 + domainLength)
	default:
		return nil, nil, errors.New("Shadowsocks|UDP: Unknown address type")
	}

	request.Port = v2net.PortFromBytes(payload.Value[:2])
	payload.SliceFrom(2)

	return request, payload, nil
}
コード例 #20
0
ファイル: udp.go プロジェクト: DZLZHCODE/v2ray-core
func (request *Socks5UDPRequest) Write(buffer *alloc.Buffer) {
	buffer.AppendBytes(0, 0, request.Fragment)
	switch request.Address.Family() {
	case v2net.AddressFamilyIPv4:
		buffer.AppendBytes(AddrTypeIPv4).Append(request.Address.IP())
	case v2net.AddressFamilyIPv6:
		buffer.AppendBytes(AddrTypeIPv6).Append(request.Address.IP())
	case v2net.AddressFamilyDomain:
		buffer.AppendBytes(AddrTypeDomain, byte(len(request.Address.Domain()))).Append([]byte(request.Address.Domain()))
	}
	buffer.AppendUint16(request.Port.Value())
	buffer.Append(request.Data.Value)
}
コード例 #21
0
ファイル: srtp.go プロジェクト: xyz12810/v2ray-core
func (this *SRTP) Open(payload *alloc.Buffer) bool {
	payload.SliceFrom(this.Overhead())
	return true
}
コード例 #22
0
ファイル: crypt.go プロジェクト: DZLZHCODE/v2ray-core
func (this *SimpleAuthenticator) Seal(buffer *alloc.Buffer) {
	buffer.PrependUint16(uint16(buffer.Len()))
	fnvHash := fnv.New32a()
	fnvHash.Write(buffer.Value)
	buffer.PrependHash(fnvHash)

	len := buffer.Len()
	xtra := 4 - len%4
	if xtra != 0 {
		buffer.Slice(0, len+xtra)
	}
	xorfwd(buffer.Value)
	if xtra != 0 {
		buffer.Slice(0, len)
	}
}