client.go 8.41 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110
// Copyright 2009 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

import (
	"bufio"
	"bytes"
	"container/vector"
	"crypto/tls"
	"fmt"
	"http"
	"io"
	"net"
	"os"
	"rand"
	"strings"
)

type ProtocolError struct {
	os.ErrorString
}

var (
	ErrBadScheme            = os.ErrorString("bad scheme")
	ErrBadStatus            = &ProtocolError{"bad status"}
	ErrBadUpgrade           = &ProtocolError{"missing or bad upgrade"}
	ErrBadWebSocketOrigin   = &ProtocolError{"missing or bad WebSocket-Origin"}
	ErrBadWebSocketLocation = &ProtocolError{"missing or bad WebSocket-Location"}
	ErrBadWebSocketProtocol = &ProtocolError{"missing or bad WebSocket-Protocol"}
	ErrChallengeResponse    = &ProtocolError{"mismatch challange/response"}
	secKeyRandomChars       [0x30 - 0x21 + 0x7F - 0x3A]byte
)

type DialError struct {
	URL      string
	Protocol string
	Origin   string
	Error    os.Error
}

func (e *DialError) String() string {
	return "websocket.Dial " + e.URL + ": " + e.Error.String()
}

func init() {
	i := 0
	for ch := byte(0x21); ch < 0x30; ch++ {
		secKeyRandomChars[i] = ch
		i++
	}
	for ch := byte(0x3a); ch < 0x7F; ch++ {
		secKeyRandomChars[i] = ch
		i++
	}
}

type handshaker func(resourceName, host, origin, location, protocol string, br *bufio.Reader, bw *bufio.Writer) os.Error

// newClient creates a new Web Socket client connection.
func newClient(resourceName, host, origin, location, protocol string, rwc io.ReadWriteCloser, handshake handshaker) (ws *Conn, err os.Error) {
	br := bufio.NewReader(rwc)
	bw := bufio.NewWriter(rwc)
	err = handshake(resourceName, host, origin, location, protocol, br, bw)
	if err != nil {
		return
	}
	buf := bufio.NewReadWriter(br, bw)
	ws = newConn(origin, location, protocol, buf, rwc)
	return
}

/*
Dial opens a new client connection to a Web Socket.

A trivial example client:

	package main

	import (
		"websocket"
		"strings"
	)

	func main() {
	 	ws, err := websocket.Dial("ws://localhost/ws", "", "http://localhost/");
	 	if err != nil {
			panic("Dial: " + err.String())
		}
		if _, err := ws.Write([]byte("hello, world!\n")); err != nil {
			panic("Write: " + err.String())
		}
		var msg = make([]byte, 512);
		if n, err := ws.Read(msg); err != nil {
			panic("Read: " + err.String())
		}
		// use msg[0:n]
	}
*/
func Dial(url, protocol, origin string) (ws *Conn, err os.Error) {
	var client net.Conn

	parsedUrl, err := http.ParseURL(url)
	if err != nil {
		goto Error
	}

	switch parsedUrl.Scheme {
	case "ws":
111
		client, err = net.Dial("tcp", parsedUrl.Host)
112 113

	case "wss":
114
		client, err = tls.Dial("tcp", parsedUrl.Host, nil)
115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247

	default:
		err = ErrBadScheme
	}
	if err != nil {
		goto Error
	}

	ws, err = newClient(parsedUrl.RawPath, parsedUrl.Host, origin, url, protocol, client, handshake)
	if err != nil {
		goto Error
	}
	return

Error:
	return nil, &DialError{url, protocol, origin, err}
}

/*
Generates handshake key as described in 4.1 Opening handshake step 16 to 22.
cf. http://www.whatwg.org/specs/web-socket-protocol/
*/
func generateKeyNumber() (key string, number uint32) {
	// 16.  Let /spaces_n/ be a random integer from 1 to 12 inclusive.
	spaces := rand.Intn(12) + 1

	// 17. Let /max_n/ be the largest integer not greater than
	//     4,294,967,295 divided by /spaces_n/
	max := int(4294967295 / uint32(spaces))

	// 18. Let /number_n/ be a random integer from 0 to /max_n/ inclusive.
	number = uint32(rand.Intn(max + 1))

	// 19. Let /product_n/ be the result of multiplying /number_n/ and
	//     /spaces_n/ together.
	product := number * uint32(spaces)

	// 20. Let /key_n/ be a string consisting of /product_n/, expressed
	// in base ten using the numerals in the range U+0030 DIGIT ZERO (0)
	// to U+0039 DIGIT NINE (9).
	key = fmt.Sprintf("%d", product)

	// 21. Insert between one and twelve random characters from the ranges
	//     U+0021 to U+002F and U+003A to U+007E into /key_n/ at random
	//     positions.
	n := rand.Intn(12) + 1
	for i := 0; i < n; i++ {
		pos := rand.Intn(len(key)) + 1
		ch := secKeyRandomChars[rand.Intn(len(secKeyRandomChars))]
		key = key[0:pos] + string(ch) + key[pos:]
	}

	// 22. Insert /spaces_n/ U+0020 SPACE characters into /key_n/ at random
	//     positions other than the start or end of the string.
	for i := 0; i < spaces; i++ {
		pos := rand.Intn(len(key)-1) + 1
		key = key[0:pos] + " " + key[pos:]
	}

	return
}

/*
Generates handshake key_3 as described in 4.1 Opening handshake step 26.
cf. http://www.whatwg.org/specs/web-socket-protocol/
*/
func generateKey3() (key []byte) {
	// 26. Let /key3/ be a string consisting of eight random bytes (or
	//  equivalently, a random 64 bit integer encoded in big-endian order).
	key = make([]byte, 8)
	for i := 0; i < 8; i++ {
		key[i] = byte(rand.Intn(256))
	}
	return
}

/*
Web Socket protocol handshake based on
http://www.whatwg.org/specs/web-socket-protocol/
(draft of http://tools.ietf.org/html/draft-hixie-thewebsocketprotocol)
*/
func handshake(resourceName, host, origin, location, protocol string, br *bufio.Reader, bw *bufio.Writer) (err os.Error) {
	// 4.1. Opening handshake.
	// Step 5.  send a request line.
	bw.WriteString("GET " + resourceName + " HTTP/1.1\r\n")

	// Step 6-14. push request headers in fields.
	var fields vector.StringVector
	fields.Push("Upgrade: WebSocket\r\n")
	fields.Push("Connection: Upgrade\r\n")
	fields.Push("Host: " + host + "\r\n")
	fields.Push("Origin: " + origin + "\r\n")
	if protocol != "" {
		fields.Push("Sec-WebSocket-Protocol: " + protocol + "\r\n")
	}
	// TODO(ukai): Step 15. send cookie if any.

	// Step 16-23. generate keys and push Sec-WebSocket-Key<n> in fields.
	key1, number1 := generateKeyNumber()
	key2, number2 := generateKeyNumber()
	fields.Push("Sec-WebSocket-Key1: " + key1 + "\r\n")
	fields.Push("Sec-WebSocket-Key2: " + key2 + "\r\n")

	// Step 24. shuffle fields and send them out.
	for i := 1; i < len(fields); i++ {
		j := rand.Intn(i)
		fields[i], fields[j] = fields[j], fields[i]
	}
	for i := 0; i < len(fields); i++ {
		bw.WriteString(fields[i])
	}
	// Step 25. send CRLF.
	bw.WriteString("\r\n")

	// Step 26. genearte 8 bytes random key.
	key3 := generateKey3()
	// Step 27. send it out.
	bw.Write(key3)
	if err = bw.Flush(); err != nil {
		return
	}

	// Step 28-29, 32-40. read response from server.
	resp, err := http.ReadResponse(br, "GET")
	if err != nil {
		return err
	}
	// Step 30. check response code is 101.
	if resp.StatusCode != 101 {
		return ErrBadStatus
	}

	// Step 41. check websocket headers.
248 249
	if resp.Header.Get("Upgrade") != "WebSocket" ||
		strings.ToLower(resp.Header.Get("Connection")) != "upgrade" {
250 251 252
		return ErrBadUpgrade
	}

253
	if resp.Header.Get("Sec-Websocket-Origin") != origin {
254 255 256
		return ErrBadWebSocketOrigin
	}

257
	if resp.Header.Get("Sec-Websocket-Location") != location {
258 259 260
		return ErrBadWebSocketLocation
	}

261
	if protocol != "" && resp.Header.Get("Sec-Websocket-Protocol") != protocol {
262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306
		return ErrBadWebSocketProtocol
	}

	// Step 42-43. get expected data from challange data.
	expected, err := getChallengeResponse(number1, number2, key3)
	if err != nil {
		return err
	}

	// Step 44. read 16 bytes from server.
	reply := make([]byte, 16)
	if _, err = io.ReadFull(br, reply); err != nil {
		return err
	}

	// Step 45. check the reply equals to expected data.
	if !bytes.Equal(expected, reply) {
		return ErrChallengeResponse
	}
	// WebSocket connection is established.
	return
}

/*
Handhake described in (soon obsolete)
draft-hixie-thewebsocket-protocol-75.
*/
func draft75handshake(resourceName, host, origin, location, protocol string, br *bufio.Reader, bw *bufio.Writer) (err os.Error) {
	bw.WriteString("GET " + resourceName + " HTTP/1.1\r\n")
	bw.WriteString("Upgrade: WebSocket\r\n")
	bw.WriteString("Connection: Upgrade\r\n")
	bw.WriteString("Host: " + host + "\r\n")
	bw.WriteString("Origin: " + origin + "\r\n")
	if protocol != "" {
		bw.WriteString("WebSocket-Protocol: " + protocol + "\r\n")
	}
	bw.WriteString("\r\n")
	bw.Flush()
	resp, err := http.ReadResponse(br, "GET")
	if err != nil {
		return
	}
	if resp.Status != "101 Web Socket Protocol Handshake" {
		return ErrBadStatus
	}
307 308
	if resp.Header.Get("Upgrade") != "WebSocket" ||
		resp.Header.Get("Connection") != "Upgrade" {
309 310
		return ErrBadUpgrade
	}
311
	if resp.Header.Get("Websocket-Origin") != origin {
312 313
		return ErrBadWebSocketOrigin
	}
314
	if resp.Header.Get("Websocket-Location") != location {
315 316
		return ErrBadWebSocketLocation
	}
317
	if protocol != "" && resp.Header.Get("Websocket-Protocol") != protocol {
318 319 320 321
		return ErrBadWebSocketProtocol
	}
	return
}