// Copyright 2013 The Gorilla WebSocket 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"
"errors"
"net"
"net/http"
"net/url"
"strings"
"time"
)
// HandshakeError describes an error with the handshake from the peer.
type HandshakeError struct {
message string
}
func (e HandshakeError) Error() string { return e.message }
// Upgrader specifies parameters for upgrading an HTTP connection to a
// WebSocket connection.
type Upgrader struct {
// HandshakeTimeout specifies the duration for the handshake to complete.
HandshakeTimeout time.Duration
// ReadBufferSize and WriteBufferSize specify I/O buffer sizes. If a buffer
// size is zero, then buffers allocated by the HTTP server are used. The
// I/O buffer sizes do not limit the size of the messages that can be sent
// or received.
ReadBufferSize, WriteBufferSize int
// Subprotocols specifies the server's supported protocols in order of
// preference. If this field is set, then the Upgrade method negotiates a
// subprotocol by selecting the first match in this list with a protocol
// requested by the client.
Subprotocols []string
// Error specifies the function for generating HTTP error responses. If Error
// is nil, then http.Error is used to generate the HTTP response.
Error func(w http.ResponseWriter, r *http.Request, status int, reason error)
// CheckOrigin returns true if the request Origin header is acceptable. If
// CheckOrigin is nil, the host in the Origin header must not be set or
// must match the host of the request.
CheckOrigin func(r *http.Request) bool
// EnableCompression specify if the server should attempt to negotiate per
// message compression (RFC 7692). Setting this value to true does not
// guarantee that compression will be supported. Currently only "no context
// takeover" modes are supported.
EnableCompression bool
}
func (u *Upgrader) returnError(w http.ResponseWriter, r *http.Request, status int, reason string) (*Conn, error) {
err := HandshakeError{reason}
if u.Error != nil {
u.Error(w, r, status, err)
} else {
w.Header().Set("Sec-Websocket-Version", "13")
http.Error(w, http.StatusText(status), status)
}
return nil, err
}
// checkSameOrigin returns true if the origin is not set or is equal to the request host.
func checkSameOrigin(r *http.Request) bool {
origin := r.Header["Origin"]
if len(origin) == 0 {
return true
}
u, err := url.Parse(origin[0])
if err != nil {
return false
}
return u.Host == r.Host
}
func (u *Upgrader) selectSubprotocol(r *http.Request, responseHeader http.Header) string {
if u.Subprotocols != nil {
clientProtocols := Subprotocols(r)
for _, serverProtocol := range u.Subprotocols {
for _, clientProtocol := range clientProtocols {
if clientProtocol == serverProtocol {
return clientProtocol
}
}
}
} else if responseHeader != nil {
return responseHeader.Get("Sec-Websocket-Protocol")
}
return ""
}
// Upgrade upgrades the HTTP server connection to the WebSocket protocol.
//
// The responseHeader is included in the response to the client's upgrade
// request. Use the responseHeader to specify cookies (Set-Cookie) and the
// application negotiated subprotocol (Sec-Websocket-Protocol).
//
// If the upgrade fails, then Upgrade replies to the client with an HTTP error
// response.
func (u *Upgrader) Upgrade(w http.ResponseWriter, r *http.Request, responseHeader http.Header) (*Conn, error) {
if r.Method != "GET" {
return u.returnError(w, r, http.StatusMethodNotAllowed, "websocket: not a websocket handshake: request method is not GET")
}
if _, ok := responseHeader["Sec-Websocket-Extensions"]; ok {
return u.returnError(w, r, http.StatusInternalServerError, "websocket: application specific 'Sec-Websocket-Extensions' headers are unsupported")
}
if !tokenListContainsValue(r.Header, "Connection", "upgrade") {
return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: 'upgrade' token not found in 'Connection' header")
}
if !tokenListContainsValue(r.Header, "Upgrade", "websocket") {
return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: 'websocket' token not found in 'Upgrade' header")
}
if !tokenListContainsValue(r.Header, "Sec-Websocket-Version", "13") {
return u.returnError(w, r, http.StatusBadRequest, "websocket: unsupported version: 13 not found in 'Sec-Websocket-Version' header")
}
checkOrigin := u.CheckOrigin
if checkOrigin == nil {
checkOrigin = checkSameOrigin
}
if !checkOrigin(r) {
return u.returnError(w, r, http.StatusForbidden, "websocket: 'Origin' header value not allowed")
}
challengeKey := r.Header.Get("Sec-Websocket-Key")
if challengeKey == "" {
return u.returnError(w, r, http.StatusBadRequest, "websocket: not a websocket handshake: `Sec-Websocket-Key' header is missing or blank")
}
subprotocol := u.selectSubprotocol(r, responseHeader)
// Negotiate PMCE
var compress bool
if u.EnableCompression {
for _, ext := range parseExtensions(r.Header) {
if ext[""] != "permessage-deflate" {
continue
}
compress = true
break
}
}
var (
netConn net.Conn
err error
)
h, ok := w.(http.Hijacker)
if !ok {
return u.returnError(w, r, http.StatusInternalServerError, "websocket: response does not implement http.Hijacker")
}
var brw *bufio.ReadWriter
netConn, brw, err = h.Hijack()
if err != nil {
return u.returnError(w, r, http.StatusInternalServerError, err.Error())
}
if brw.Reader.Buffered() > 0 {
netConn.Close()
return nil, errors.New("websocket: client sent data before handshake is complete")
}
c := newConnBRW(netConn, true, u.ReadBufferSize, u.WriteBufferSize, brw)
c.subprotocol = subprotocol
if compress {
c.newCompressionWriter = compressNoContextTakeover
c.newDecompressionReader = decompressNoContextTakeover
}
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"...)
if c.subprotocol != "" {
p = append(p, "Sec-Websocket-Protocol: "...)
p = append(p, c.subprotocol...)
p = append(p, "\r\n"...)
}
if compress {
p = append(p, "Sec-Websocket-Extensions: permessage-deflate; server_no_context_takeover; client_no_context_takeover\r\n"...)
}
for k, vs := range responseHeader {
if k == "Sec-Websocket-Protocol" {
continue
}
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"...)
// Clear deadlines set by HTTP server.
netConn.SetDeadline(time.Time{})
if u.HandshakeTimeout > 0 {
netConn.SetWriteDeadline(time.Now().Add(u.HandshakeTimeout))
}
if _, err = netConn.Write(p); err != nil {
netConn.Close()
return nil, err
}
if u.HandshakeTimeout > 0 {
netConn.SetWriteDeadline(time.Time{})
}
return c, nil
}
// Upgrade upgrades the HTTP server connection to the WebSocket protocol.
//
// This function is deprecated, use websocket.Upgrader instead.
//
// 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) {
u := Upgrader{ReadBufferSize: readBufSize, WriteBufferSize: writeBufSize}
u.Error = func(w http.ResponseWriter, r *http.Request, status int, reason error) {
// don't return errors to maintain backwards compatibility
}
u.CheckOrigin = func(r *http.Request) bool {
// allow all connections by default
return true
}
return u.Upgrade(w, r, responseHeader)
}
// 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
}
// IsWebSocketUpgrade returns true if the client requested upgrade to the
// WebSocket protocol.
func IsWebSocketUpgrade(r *http.Request) bool {
return tokenListContainsValue(r.Header, "Connection", "upgrade") &&
tokenListContainsValue(r.Header, "Upgrade", "websocket")
}
