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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package websocket
// This file implements a protocol of hybi draft.
// http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-17
import (
"bufio"
"bytes"
"crypto/rand"
"crypto/sha1"
"encoding/base64"
"encoding/binary"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"strings"
)
const (
websocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
closeStatusNormal = 1000
closeStatusGoingAway = 1001
closeStatusProtocolError = 1002
closeStatusUnsupportedData = 1003
closeStatusFrameTooLarge = 1004
closeStatusNoStatusRcvd = 1005
closeStatusAbnormalClosure = 1006
closeStatusBadMessageData = 1007
closeStatusPolicyViolation = 1008
closeStatusTooBigData = 1009
closeStatusExtensionMismatch = 1010
maxControlFramePayloadLength = 125
)
var (
ErrBadMaskingKey = &ProtocolError{"bad masking key"}
ErrBadPongMessage = &ProtocolError{"bad pong message"}
ErrBadClosingStatus = &ProtocolError{"bad closing status"}
ErrUnsupportedExtensions = &ProtocolError{"unsupported extensions"}
ErrNotImplemented = &ProtocolError{"not implemented"}
handshakeHeader = map[string]bool{
"Host": true,
"Upgrade": true,
"Connection": true,
"Sec-Websocket-Key": true,
"Sec-Websocket-Origin": true,
"Sec-Websocket-Version": true,
"Sec-Websocket-Protocol": true,
"Sec-Websocket-Accept": true,
}
)
// A hybiFrameHeader is a frame header as defined in hybi draft.
type hybiFrameHeader struct {
Fin bool
Rsv [3]bool
OpCode byte
Length int64
MaskingKey []byte
data *bytes.Buffer
}
// A hybiFrameReader is a reader for hybi frame.
type hybiFrameReader struct {
reader io.Reader
header hybiFrameHeader
pos int64
length int
}
func (frame *hybiFrameReader) Read(msg []byte) (n int, err error) {
n, err = frame.reader.Read(msg)
if frame.header.MaskingKey != nil {
for i := 0; i < n; i++ {
msg[i] = msg[i] ^ frame.header.MaskingKey[frame.pos%4]
frame.pos++
}
}
return n, err
}
func (frame *hybiFrameReader) PayloadType() byte { return frame.header.OpCode }
func (frame *hybiFrameReader) HeaderReader() io.Reader {
if frame.header.data == nil {
return nil
}
if frame.header.data.Len() == 0 {
return nil
}
return frame.header.data
}
func (frame *hybiFrameReader) TrailerReader() io.Reader { return nil }
func (frame *hybiFrameReader) Len() (n int) { return frame.length }
// A hybiFrameReaderFactory creates new frame reader based on its frame type.
type hybiFrameReaderFactory struct {
*bufio.Reader
}
// NewFrameReader reads a frame header from the connection, and creates new reader for the frame.
// See Section 5.2 Base Framing protocol for detail.
// http://tools.ietf.org/html/draft-ietf-hybi-thewebsocketprotocol-17#section-5.2
func (buf hybiFrameReaderFactory) NewFrameReader() (frame frameReader, err error) {
hybiFrame := new(hybiFrameReader)
frame = hybiFrame
var header []byte
var b byte
// First byte. FIN/RSV1/RSV2/RSV3/OpCode(4bits)
b, err = buf.ReadByte()
if err != nil {
return
}
header = append(header, b)
hybiFrame.header.Fin = ((header[0] >> 7) & 1) != 0
for i := 0; i < 3; i++ {
j := uint(6 - i)
hybiFrame.header.Rsv[i] = ((header[0] >> j) & 1) != 0
}
hybiFrame.header.OpCode = header[0] & 0x0f
// Second byte. Mask/Payload len(7bits)
b, err = buf.ReadByte()
if err != nil {
return
}
header = append(header, b)
mask := (b & 0x80) != 0
b &= 0x7f
lengthFields := 0
switch {
case b <= 125: // Payload length 7bits.
hybiFrame.header.Length = int64(b)
case b == 126: // Payload length 7+16bits
lengthFields = 2
case b == 127: // Payload length 7+64bits
lengthFields = 8
}
for i := 0; i < lengthFields; i++ {
b, err = buf.ReadByte()
if err != nil {
return
}
if lengthFields == 8 && i == 0 { // MSB must be zero when 7+64 bits
b &= 0x7f
}
header = append(header, b)
hybiFrame.header.Length = hybiFrame.header.Length*256 + int64(b)
}
if mask {
// Masking key. 4 bytes.
for i := 0; i < 4; i++ {
b, err = buf.ReadByte()
if err != nil {
return
}
header = append(header, b)
hybiFrame.header.MaskingKey = append(hybiFrame.header.MaskingKey, b)
}
}
hybiFrame.reader = io.LimitReader(buf.Reader, hybiFrame.header.Length)
hybiFrame.header.data = bytes.NewBuffer(header)
hybiFrame.length = len(header) + int(hybiFrame.header.Length)
return
}
// A HybiFrameWriter is a writer for hybi frame.
type hybiFrameWriter struct {
writer *bufio.Writer
header *hybiFrameHeader
}
func (frame *hybiFrameWriter) Write(msg []byte) (n int, err error) {
var header []byte
var b byte
if frame.header.Fin {
b |= 0x80
}
for i := 0; i < 3; i++ {
if frame.header.Rsv[i] {
j := uint(6 - i)
b |= 1 << j
}
}
b |= frame.header.OpCode
header = append(header, b)
if frame.header.MaskingKey != nil {
b = 0x80
} else {
b = 0
}
lengthFields := 0
length := len(msg)
switch {
case length <= 125:
b |= byte(length)
case length < 65536:
b |= 126
lengthFields = 2
default:
b |= 127
lengthFields = 8
}
header = append(header, b)
for i := 0; i < lengthFields; i++ {
j := uint((lengthFields - i - 1) * 8)
b = byte((length >> j) & 0xff)
header = append(header, b)
}
if frame.header.MaskingKey != nil {
if len(frame.header.MaskingKey) != 4 {
return 0, ErrBadMaskingKey
}
header = append(header, frame.header.MaskingKey...)
frame.writer.Write(header)
data := make([]byte, length)
for i := range data {
data[i] = msg[i] ^ frame.header.MaskingKey[i%4]
}
frame.writer.Write(data)
err = frame.writer.Flush()
return length, err
}
frame.writer.Write(header)
frame.writer.Write(msg)
err = frame.writer.Flush()
return length, err
}
func (frame *hybiFrameWriter) Close() error { return nil }
type hybiFrameWriterFactory struct {
*bufio.Writer
needMaskingKey bool
}
func (buf hybiFrameWriterFactory) NewFrameWriter(payloadType byte) (frame frameWriter, err error) {
frameHeader := &hybiFrameHeader{Fin: true, OpCode: payloadType}
if buf.needMaskingKey {
frameHeader.MaskingKey, err = generateMaskingKey()
if err != nil {
return nil, err
}
}
return &hybiFrameWriter{writer: buf.Writer, header: frameHeader}, nil
}
type hybiFrameHandler struct {
conn *Conn
payloadType byte
}
func (handler *hybiFrameHandler) HandleFrame(frame frameReader) (frameReader, error) {
if handler.conn.IsServerConn() {
// The client MUST mask all frames sent to the server.
if frame.(*hybiFrameReader).header.MaskingKey == nil {
handler.WriteClose(closeStatusProtocolError)
return nil, io.EOF
}
} else {
// The server MUST NOT mask all frames.
if frame.(*hybiFrameReader).header.MaskingKey != nil {
handler.WriteClose(closeStatusProtocolError)
return nil, io.EOF
}
}
if header := frame.HeaderReader(); header != nil {
io.Copy(ioutil.Discard, header)
}
switch frame.PayloadType() {
case ContinuationFrame:
frame.(*hybiFrameReader).header.OpCode = handler.payloadType
case TextFrame, BinaryFrame:
handler.payloadType = frame.PayloadType()
case CloseFrame:
return nil, io.EOF
case PingFrame, PongFrame:
b := make([]byte, maxControlFramePayloadLength)
n, err := io.ReadFull(frame, b)
if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
return nil, err
}
io.Copy(ioutil.Discard, frame)
if frame.PayloadType() == PingFrame {
if _, err := handler.WritePong(b[:n]); err != nil {
return nil, err
}
}
return nil, nil
}
return frame, nil
}
func (handler *hybiFrameHandler) WriteClose(status int) (err error) {
handler.conn.wio.Lock()
defer handler.conn.wio.Unlock()
w, err := handler.conn.frameWriterFactory.NewFrameWriter(CloseFrame)
if err != nil {
return err
}
msg := make([]byte, 2)
binary.BigEndian.PutUint16(msg, uint16(status))
_, err = w.Write(msg)
w.Close()
return err
}
func (handler *hybiFrameHandler) WritePong(msg []byte) (n int, err error) {
handler.conn.wio.Lock()
defer handler.conn.wio.Unlock()
w, err := handler.conn.frameWriterFactory.NewFrameWriter(PongFrame)
if err != nil {
return 0, err
}
n, err = w.Write(msg)
w.Close()
return n, err
}
// newHybiConn creates a new WebSocket connection speaking hybi draft protocol.
func newHybiConn(config *Config, buf *bufio.ReadWriter, rwc io.ReadWriteCloser, request *http.Request) *Conn {
if buf == nil {
br := bufio.NewReader(rwc)
bw := bufio.NewWriter(rwc)
buf = bufio.NewReadWriter(br, bw)
}
ws := &Conn{config: config, request: request, buf: buf, rwc: rwc,
frameReaderFactory: hybiFrameReaderFactory{buf.Reader},
frameWriterFactory: hybiFrameWriterFactory{
buf.Writer, request == nil},
PayloadType: TextFrame,
defaultCloseStatus: closeStatusNormal}
ws.frameHandler = &hybiFrameHandler{conn: ws}
return ws
}
// generateMaskingKey generates a masking key for a frame.
func generateMaskingKey() (maskingKey []byte, err error) {
maskingKey = make([]byte, 4)
if _, err = io.ReadFull(rand.Reader, maskingKey); err != nil {
return
}
return
}
// generateNonce generates a nonce consisting of a randomly selected 16-byte
// value that has been base64-encoded.
func generateNonce() (nonce []byte) {
key := make([]byte, 16)
if _, err := io.ReadFull(rand.Reader, key); err != nil {
panic(err)
}
nonce = make([]byte, 24)
base64.StdEncoding.Encode(nonce, key)
return
}
// removeZone removes IPv6 zone identifer from host.
// E.g., "[fe80::1%en0]:8080" to "[fe80::1]:8080"
func removeZone(host string) string {
if !strings.HasPrefix(host, "[") {
return host
}
i := strings.LastIndex(host, "]")
if i < 0 {
return host
}
j := strings.LastIndex(host[:i], "%")
if j < 0 {
return host
}
return host[:j] + host[i:]
}
// getNonceAccept computes the base64-encoded SHA-1 of the concatenation of
// the nonce ("Sec-WebSocket-Key" value) with the websocket GUID string.
func getNonceAccept(nonce []byte) (expected []byte, err error) {
h := sha1.New()
if _, err = h.Write(nonce); err != nil {
return
}
if _, err = h.Write([]byte(websocketGUID)); err != nil {
return
}
expected = make([]byte, 28)
base64.StdEncoding.Encode(expected, h.Sum(nil))
return
}
// Client handshake described in draft-ietf-hybi-thewebsocket-protocol-17
func hybiClientHandshake(config *Config, br *bufio.Reader, bw *bufio.Writer) (err error) {
bw.WriteString("GET " + config.Location.RequestURI() + " HTTP/1.1\r\n")
// According to RFC 6874, an HTTP client, proxy, or other
// intermediary must remove any IPv6 zone identifier attached
// to an outgoing URI.
bw.WriteString("Host: " + removeZone(config.Location.Host) + "\r\n")
bw.WriteString("Upgrade: websocket\r\n")
bw.WriteString("Connection: Upgrade\r\n")
nonce := generateNonce()
if config.handshakeData != nil {
nonce = []byte(config.handshakeData["key"])
}
bw.WriteString("Sec-WebSocket-Key: " + string(nonce) + "\r\n")
bw.WriteString("Origin: " + strings.ToLower(config.Origin.String()) + "\r\n")
if config.Version != ProtocolVersionHybi13 {
return ErrBadProtocolVersion
}
bw.WriteString("Sec-WebSocket-Version: " + fmt.Sprintf("%d", config.Version) + "\r\n")
if len(config.Protocol) > 0 {
bw.WriteString("Sec-WebSocket-Protocol: " + strings.Join(config.Protocol, ", ") + "\r\n")
}
// TODO(ukai): send Sec-WebSocket-Extensions.
err = config.Header.WriteSubset(bw, handshakeHeader)
if err != nil {
return err
}
bw.WriteString("\r\n")
if err = bw.Flush(); err != nil {
return err
}
resp, err := http.ReadResponse(br, &http.Request{Method: "GET"})
if err != nil {
return err
}
if resp.StatusCode != 101 {
return ErrBadStatus
}
if strings.ToLower(resp.Header.Get("Upgrade")) != "websocket" ||
strings.ToLower(resp.Header.Get("Connection")) != "upgrade" {
return ErrBadUpgrade
}
expectedAccept, err := getNonceAccept(nonce)
if err != nil {
return err
}
if resp.Header.Get("Sec-WebSocket-Accept") != string(expectedAccept) {
return ErrChallengeResponse
}
if resp.Header.Get("Sec-WebSocket-Extensions") != "" {
return ErrUnsupportedExtensions
}
offeredProtocol := resp.Header.Get("Sec-WebSocket-Protocol")
if offeredProtocol != "" {
protocolMatched := false
for i := 0; i < len(config.Protocol); i++ {
if config.Protocol[i] == offeredProtocol {
protocolMatched = true
break
}
}
if !protocolMatched {
return ErrBadWebSocketProtocol
}
config.Protocol = []string{offeredProtocol}
}
return nil
}
// newHybiClientConn creates a client WebSocket connection after handshake.
func newHybiClientConn(config *Config, buf *bufio.ReadWriter, rwc io.ReadWriteCloser) *Conn {
return newHybiConn(config, buf, rwc, nil)
}
// A HybiServerHandshaker performs a server handshake using hybi draft protocol.
type hybiServerHandshaker struct {
*Config
accept []byte
}
func (c *hybiServerHandshaker) ReadHandshake(buf *bufio.Reader, req *http.Request) (code int, err error) {
c.Version = ProtocolVersionHybi13
if req.Method != "GET" {
return http.StatusMethodNotAllowed, ErrBadRequestMethod
}
// HTTP version can be safely ignored.
if strings.ToLower(req.Header.Get("Upgrade")) != "websocket" ||
!strings.Contains(strings.ToLower(req.Header.Get("Connection")), "upgrade") {
return http.StatusBadRequest, ErrNotWebSocket
}
key := req.Header.Get("Sec-Websocket-Key")
if key == "" {
return http.StatusBadRequest, ErrChallengeResponse
}
version := req.Header.Get("Sec-Websocket-Version")
switch version {
case "13":
c.Version = ProtocolVersionHybi13
default:
return http.StatusBadRequest, ErrBadWebSocketVersion
}
var scheme string
if req.TLS != nil {
scheme = "wss"
} else {
scheme = "ws"
}
c.Location, err = url.ParseRequestURI(scheme + "://" + req.Host + req.URL.RequestURI())
if err != nil {
return http.StatusBadRequest, err
}
protocol := strings.TrimSpace(req.Header.Get("Sec-Websocket-Protocol"))
if protocol != "" {
protocols := strings.Split(protocol, ",")
for i := 0; i < len(protocols); i++ {
c.Protocol = append(c.Protocol, strings.TrimSpace(protocols[i]))
}
}
c.accept, err = getNonceAccept([]byte(key))
if err != nil {
return http.StatusInternalServerError, err
}
return http.StatusSwitchingProtocols, nil
}
// Origin parses the Origin header in req.
// If the Origin header is not set, it returns nil and nil.
func Origin(config *Config, req *http.Request) (*url.URL, error) {
var origin string
switch config.Version {
case ProtocolVersionHybi13:
origin = req.Header.Get("Origin")
}
if origin == "" {
return nil, nil
}
return url.ParseRequestURI(origin)
}
func (c *hybiServerHandshaker) AcceptHandshake(buf *bufio.Writer) (err error) {
if len(c.Protocol) > 0 {
if len(c.Protocol) != 1 {
// You need choose a Protocol in Handshake func in Server.
return ErrBadWebSocketProtocol
}
}
buf.WriteString("HTTP/1.1 101 Switching Protocols\r\n")
buf.WriteString("Upgrade: websocket\r\n")
buf.WriteString("Connection: Upgrade\r\n")
buf.WriteString("Sec-WebSocket-Accept: " + string(c.accept) + "\r\n")
if len(c.Protocol) > 0 {
buf.WriteString("Sec-WebSocket-Protocol: " + c.Protocol[0] + "\r\n")
}
// TODO(ukai): send Sec-WebSocket-Extensions.
if c.Header != nil {
err := c.Header.WriteSubset(buf, handshakeHeader)
if err != nil {
return err
}
}
buf.WriteString("\r\n")
return buf.Flush()
}
func (c *hybiServerHandshaker) NewServerConn(buf *bufio.ReadWriter, rwc io.ReadWriteCloser, request *http.Request) *Conn {
return newHybiServerConn(c.Config, buf, rwc, request)
}
// newHybiServerConn returns a new WebSocket connection speaking hybi draft protocol.
func newHybiServerConn(config *Config, buf *bufio.ReadWriter, rwc io.ReadWriteCloser, request *http.Request) *Conn {
return newHybiConn(config, buf, rwc, request)
}