1// Copyright 2013 The Gorilla WebSocket Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package websocket
6
7import (
8 "bufio"
9 "errors"
10 "net"
11 "net/http"
12 "net/url"
13 "strings"
14 "time"
15)
16
17// HandshakeError describes an error with the handshake from the peer.
18type HandshakeError struct {
19 message string
20}
21
22func (e HandshakeError) Error() string { return e.message }
23
24// Upgrader specifies parameters for upgrading an HTTP connection to a
25// WebSocket connection.
26type Upgrader struct {
27 // HandshakeTimeout specifies the duration for the handshake to complete.
28 HandshakeTimeout time.Duration
29
30 // ReadBufferSize and WriteBufferSize specify I/O buffer sizes. If a buffer
31 // size is zero, then buffers allocated by the HTTP server are used. The
32 // I/O buffer sizes do not limit the size of the messages that can be sent
33 // or received.
34 ReadBufferSize, WriteBufferSize int
35
36 // Subprotocols specifies the server's supported protocols in order of
37 // preference. If this field is set, then the Upgrade method negotiates a
38 // subprotocol by selecting the first match in this list with a protocol
39 // requested by the client.
40 Subprotocols []string
41
42 // Error specifies the function for generating HTTP error responses. If Error
43 // is nil, then http.Error is used to generate the HTTP response.
44 Error func(w http.ResponseWriter, r *http.Request, status int, reason error)
45
46 // CheckOrigin returns true if the request Origin header is acceptable. If
47 // CheckOrigin is nil, the host in the Origin header must not be set or
48 // must match the host of the request.
49 CheckOrigin func(r *http.Request) bool
50
51 // EnableCompression specify if the server should attempt to negotiate per
52 // message compression (RFC 7692). Setting this value to true does not
53 // guarantee that compression will be supported. Currently only "no context
54 // takeover" modes are supported.
55 EnableCompression bool
56}
57
58func (u *Upgrader) returnError(w http.ResponseWriter, r *http.Request, status int, reason string) (*Conn, error) {
59 err := HandshakeError{reason}
60 if u.Error != nil {
61 u.Error(w, r, status, err)
62 } else {
63 w.Header().Set("Sec-Websocket-Version", "13")
64 http.Error(w, http.StatusText(status), status)
65 }
66 return nil, err
67}
68
69// checkSameOrigin returns true if the origin is not set or is equal to the request host.
70func checkSameOrigin(r *http.Request) bool {
71 origin := r.Header["Origin"]
72 if len(origin) == 0 {
73 return true
74 }
75 u, err := url.Parse(origin[0])
76 if err != nil {
77 return false
78 }
79 return u.Host == r.Host
80}
81
82func (u *Upgrader) selectSubprotocol(r *http.Request, responseHeader http.Header) string {
83 if u.Subprotocols != nil {
84 clientProtocols := Subprotocols(r)
85 for _, serverProtocol := range u.Subprotocols {
86 for _, clientProtocol := range clientProtocols {
87 if clientProtocol == serverProtocol {
88 return clientProtocol
89 }
90 }
91 }
92 } else if responseHeader != nil {
93 return responseHeader.Get("Sec-Websocket-Protocol")
94 }
95 return ""
96}
97
98// Upgrade upgrades the HTTP server connection to the WebSocket protocol.
99//
100// The responseHeader is included in the response to the client's upgrade
101// request. Use the responseHeader to specify cookies (Set-Cookie) and the
102// application negotiated subprotocol (Sec-Websocket-Protocol).
103//
104// If the upgrade fails, then Upgrade replies to the client with an HTTP error
105// response.
106func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header) (*Conn, error) {
107 if r.Method != "GET" {
108 return u.returnError(w, r, http.StatusMethodNotAllowed, "websocket: not a websocket handshake: request method is not GET")
109 }
110
111 if _, ok := responseHeader["Sec-Websocket-Extensions"]; ok {
112 return u.returnError(w, r, http.StatusInternalServerError, "websocket: application specific 'Sec-Websocket-Extensions' headers are unsupported")
113 }
114
115 if !tokenListContainsValue(r.Header, "Connection", "upgrade") {
116 return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: 'upgrade' token not found in 'Connection' header")
117 }
118
119 if !tokenListContainsValue(r.Header, "Upgrade", "websocket") {
120 return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: 'websocket' token not found in 'Upgrade' header")
121 }
122
123 if !tokenListContainsValue(r.Header, "Sec-Websocket-Version", "13") {
124 return u.returnError(w, r, http.StatusBadRequest, "websocket: unsupported version: 13 not found in 'Sec-Websocket-Version' header")
125 }
126
127 checkOrigin := u.CheckOrigin
128 if checkOrigin == nil {
129 checkOrigin = checkSameOrigin
130 }
131 if !checkOrigin(r) {
132 return u.returnError(w, r, http.StatusForbidden, "websocket: 'Origin' header value not allowed")
133 }
134
135 challengeKey := r.Header.Get("Sec-Websocket-Key")
136 if challengeKey == "" {
137 return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: `Sec-Websocket-Key' header is missing or blank")
138 }
139
140 subprotocol := u.selectSubprotocol(r, responseHeader)
141
142 // Negotiate PMCE
143 var compress bool
144 if u.EnableCompression {
145 for _, ext := range parseExtensions(r.Header) {
146 if ext[""] != "permessage-deflate" {
147 continue
148 }
149 compress = true
150 break
151 }
152 }
153
154 var (
155 netConn net.Conn
156 err error
157 )
158
159 h, ok := w.(http.Hijacker)
160 if !ok {
161 return u.returnError(w, r, http.StatusInternalServerError, "websocket: response does not implement http.Hijacker")
162 }
163 var brw *bufio.ReadWriter
164 netConn, brw, err = h.Hijack()
165 if err != nil {
166 return u.returnError(w, r, http.StatusInternalServerError, err.Error())
167 }
168
169 if brw.Reader.Buffered() > 0 {
170 netConn.Close()
171 return nil, errors.New("websocket: client sent data before handshake is complete")
172 }
173
174 c := newConnBRW(netConn, true, u.ReadBufferSize, u.WriteBufferSize, brw)
175 c.subprotocol = subprotocol
176
177 if compress {
178 c.newCompressionWriter = compressNoContextTakeover
179 c.newDecompressionReader = decompressNoContextTakeover
180 }
181
182 p := c.writeBuf[:0]
183 p = append(p, "HTTP/1.1 101 Switching Protocols\r\nUpgrade: websocket\r\nConnection: Upgrade\r\nSec-WebSocket-Accept: "...)
184 p = append(p, computeAcceptKey(challengeKey)...)
185 p = append(p, "\r\n"...)
186 if c.subprotocol != "" {
187 p = append(p, "Sec-Websocket-Protocol: "...)
188 p = append(p, c.subprotocol...)
189 p = append(p, "\r\n"...)
190 }
191 if compress {
192 p = append(p, "Sec-Websocket-Extensions: permessage-deflate; server_no_context_takeover; client_no_context_takeover\r\n"...)
193 }
194 for k, vs := range responseHeader {
195 if k == "Sec-Websocket-Protocol" {
196 continue
197 }
198 for _, v := range vs {
199 p = append(p, k...)
200 p = append(p, ": "...)
201 for i := 0; i < len(v); i++ {
202 b := v[i]
203 if b <= 31 {
204 // prevent response splitting.
205 b = ' '
206 }
207 p = append(p, b)
208 }
209 p = append(p, "\r\n"...)
210 }
211 }
212 p = append(p, "\r\n"...)
213
214 // Clear deadlines set by HTTP server.
215 netConn.SetDeadline(time.Time{})
216
217 if u.HandshakeTimeout > 0 {
218 netConn.SetWriteDeadline(time.Now().Add(u.HandshakeTimeout))
219 }
220 if _, err = netConn.Write(p); err != nil {
221 netConn.Close()
222 return nil, err
223 }
224 if u.HandshakeTimeout > 0 {
225 netConn.SetWriteDeadline(time.Time{})
226 }
227
228 return c, nil
229}
230
231// Upgrade upgrades the HTTP server connection to the WebSocket protocol.
232//
233// This function is deprecated, use websocket.Upgrader instead.
234//
235// The application is responsible for checking the request origin before
236// calling Upgrade. An example implementation of the same origin policy is:
237//
238// if req.Header.Get("Origin") != "http://"+req.Host {
239// http.Error(w, "Origin not allowed", 403)
240// return
241// }
242//
243// If the endpoint supports subprotocols, then the application is responsible
244// for negotiating the protocol used on the connection. Use the Subprotocols()
245// function to get the subprotocols requested by the client. Use the
246// Sec-Websocket-Protocol response header to specify the subprotocol selected
247// by the application.
248//
249// The responseHeader is included in the response to the client's upgrade
250// request. Use the responseHeader to specify cookies (Set-Cookie) and the
251// negotiated subprotocol (Sec-Websocket-Protocol).
252//
253// The connection buffers IO to the underlying network connection. The
254// readBufSize and writeBufSize parameters specify the size of the buffers to
255// use. Messages can be larger than the buffers.
256//
257// If the request is not a valid WebSocket handshake, then Upgrade returns an
258// error of type HandshakeError. Applications should handle this error by
259// replying to the client with an HTTP error response.
260func Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header, readBufSize, writeBufSize int) (*Conn, error) {
261 u := Upgrader{ReadBufferSize: readBufSize, WriteBufferSize: writeBufSize}
262 u.Error = func(w http.ResponseWriter, r *http.Request, status int, reason error) {
263 // don't return errors to maintain backwards compatibility
264 }
265 u.CheckOrigin = func(r *http.Request) bool {
266 // allow all connections by default
267 return true
268 }
269 return u.Upgrade(w, r, responseHeader)
270}
271
272// Subprotocols returns the subprotocols requested by the client in the
273// Sec-Websocket-Protocol header.
274func Subprotocols(r *http.Request) []string {
275 h := strings.TrimSpace(r.Header.Get("Sec-Websocket-Protocol"))
276 if h == "" {
277 return nil
278 }
279 protocols := strings.Split(h, ",")
280 for i := range protocols {
281 protocols[i] = strings.TrimSpace(protocols[i])
282 }
283 return protocols
284}
285
286// IsWebSocketUpgrade returns true if the client requested upgrade to the
287// WebSocket protocol.
288func IsWebSocketUpgrade(r *http.Request) bool {
289 return tokenListContainsValue(r.Header, "Connection", "upgrade") &&
290 tokenListContainsValue(r.Header, "Upgrade", "websocket")
291}