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// Copyright 2013 Gary Burd. 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"
"errors"
"net"
"net/http"
"strings"
)
// HandshakeError describes an error with the handshake from the peer.
type HandshakeError struct {
message string
}
func (e HandshakeError) Error() string { return e.message }
// Upgrade upgrades the HTTP server connection to the WebSocket protocol.
//
// The application is responsible for checking the request origin before
// calling Upgrade. An example implementation of the same origin policy is:
//
// if req.Header.Get("Origin") != "http://"+req.Host {
// http.Error(w, "Origin not allowed", 403)
// return
// }
//
// If the endpoint supports subprotocols, then the application is responsible
// for negotiating the protocol used on the connection. Use the Subprotocols()
// function to get the subprotocols requested by the client. Use the
// Sec-Websocket-Protocol response header to specify the subprotocol selected
// by the application.
//
// The responseHeader is included in the response to the client's upgrade
// request. Use the responseHeader to specify cookies (Set-Cookie) and the
// negotiated subprotocol (Sec-Websocket-Protocol).
//
// The connection buffers IO to the underlying network connection. The
// readBufSize and writeBufSize parameters specify the size of the buffers to
// use. Messages can be larger than the buffers.
//
// If the request is not a valid WebSocket handshake, then Upgrade returns an
// error of type HandshakeError. Applications should handle this error by
// replying to the client with an HTTP error response.
func Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header, readBufSize, writeBufSize int) (*Conn, error) {
if values := r.Header["Sec-Websocket-Version"]; len(values) == 0 || values[0] != "13" {
return nil, HandshakeError{"websocket: version != 13"}
}
if !tokenListContainsValue(r.Header, "Connection", "upgrade") {
return nil, HandshakeError{"websocket: connection header != upgrade"}
}
if !tokenListContainsValue(r.Header, "Upgrade", "websocket") {
return nil, HandshakeError{"websocket: upgrade != websocket"}
}
var challengeKey string
values := r.Header["Sec-Websocket-Key"]
if len(values) == 0 || values[0] == "" {
return nil, HandshakeError{"websocket: key missing or blank"}
}
challengeKey = values[0]
var (
netConn net.Conn
br *bufio.Reader
err error
)
h, ok := w.(http.Hijacker)
if !ok {
return nil, errors.New("websocket: response does not implement http.Hijacker")
}
var rw *bufio.ReadWriter
netConn, rw, err = h.Hijack()
br = rw.Reader
if br.Buffered() > 0 {
netConn.Close()
return nil, errors.New("websocket: client sent data before handshake is complete")
}
c := newConn(netConn, true, readBufSize, writeBufSize)
if responseHeader != nil {
c.subprotocol = responseHeader.Get("Sec-Websocket-Protocol")
}
p := c.writeBuf[:0]
p = append(p, "HTTP/1.1 101 Switching Protocols\r\nUpgrade: websocket\r\nConnection: Upgrade\r\nSec-WebSocket-Accept: "...)
p = append(p, computeAcceptKey(challengeKey)...)
p = append(p, "\r\n"...)
for k, vs := range responseHeader {
for _, v := range vs {
p = append(p, k...)
p = append(p, ": "...)
for i := 0; i < len(v); i++ {
b := v[i]
if b <= 31 {
// prevent response splitting.
b = ' '
}
p = append(p, b)
}
p = append(p, "\r\n"...)
}
}
p = append(p, "\r\n"...)
if _, err = netConn.Write(p); err != nil {
netConn.Close()
return nil, err
}
return c, nil
}
// Subprotocols returns the subprotocols requested by the client in the
// Sec-Websocket-Protocol header.
func Subprotocols(r *http.Request) []string {
h := strings.TrimSpace(r.Header.Get("Sec-Websocket-Protocol"))
if h == "" {
return nil
}
protocols := strings.Split(h, ",")
for i := range protocols {
protocols[i] = strings.TrimSpace(protocols[i])
}
return protocols
}
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