cloudflared-mirror/websocket/websocket.go

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package websocket
import (
"crypto/sha1"
"encoding/base64"
"io"
"net"
"net/http"
"net/url"
"time"
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"github.com/cloudflare/cloudflared/h2mux"
"github.com/gorilla/websocket"
"github.com/rs/zerolog"
)
var stripWebsocketHeaders = []string{
"Upgrade",
"Connection",
"Sec-Websocket-Key",
"Sec-Websocket-Version",
"Sec-Websocket-Extensions",
}
// IsWebSocketUpgrade checks to see if the request is a WebSocket connection.
func IsWebSocketUpgrade(req *http.Request) bool {
return websocket.IsWebSocketUpgrade(req)
}
// ClientConnect creates a WebSocket client connection for provided request. Caller is responsible for closing
// the connection. The response body may not contain the entire response and does
// not need to be closed by the application.
func ClientConnect(req *http.Request, dialler *websocket.Dialer) (*websocket.Conn, *http.Response, error) {
req.URL.Scheme = ChangeRequestScheme(req.URL)
wsHeaders := websocketHeaders(req)
if dialler == nil {
dialler = &websocket.Dialer{
Proxy: http.ProxyFromEnvironment,
}
}
conn, response, err := dialler.Dial(req.URL.String(), wsHeaders)
if err != nil {
return nil, response, err
}
response.Header.Set("Sec-WebSocket-Accept", generateAcceptKey(req))
return conn, response, nil
}
// StartProxyServer will start a websocket server that will decode
// the websocket data and write the resulting data to the provided
func StartProxyServer(
log *zerolog.Logger,
listener net.Listener,
staticHost string,
shutdownC <-chan struct{},
streamHandler func(originConn io.ReadWriter, remoteConn net.Conn, log *zerolog.Logger),
) error {
upgrader := websocket.Upgrader{
ReadBufferSize: 1024,
WriteBufferSize: 1024,
}
h := handler{
upgrader: upgrader,
log: log,
staticHost: staticHost,
streamHandler: streamHandler,
}
httpServer := &http.Server{Addr: listener.Addr().String(), Handler: &h}
go func() {
<-shutdownC
_ = httpServer.Close()
}()
return httpServer.Serve(listener)
}
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// HTTP handler for the websocket proxy.
type handler struct {
log *zerolog.Logger
staticHost string
upgrader websocket.Upgrader
streamHandler func(originConn io.ReadWriter, remoteConn net.Conn, log *zerolog.Logger)
}
func (h *handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// If remote is an empty string, get the destination from the client.
finalDestination := h.staticHost
if finalDestination == "" {
if jumpDestination := r.Header.Get(h2mux.CFJumpDestinationHeader); jumpDestination == "" {
h.log.Error().Msg("Did not receive final destination from client. The --destination flag is likely not set")
return
} else {
finalDestination = jumpDestination
}
}
stream, err := net.Dial("tcp", finalDestination)
if err != nil {
h.log.Err(err).Msg("Cannot connect to remote")
return
}
defer stream.Close()
if !websocket.IsWebSocketUpgrade(r) {
_, _ = w.Write(nonWebSocketRequestPage())
return
}
conn, err := h.upgrader.Upgrade(w, r, nil)
if err != nil {
h.log.Err(err).Msg("failed to upgrade")
return
}
_ = conn.SetReadDeadline(time.Now().Add(pongWait))
conn.SetPongHandler(func(string) error { _ = conn.SetReadDeadline(time.Now().Add(pongWait)); return nil })
gorillaConn := &GorillaConn{Conn: conn, log: h.log}
go gorillaConn.pinger(r.Context())
defer conn.Close()
h.streamHandler(gorillaConn, stream, h.log)
}
// NewResponseHeader returns headers needed to return to origin for completing handshake
func NewResponseHeader(req *http.Request) http.Header {
header := http.Header{}
header.Add("Connection", "Upgrade")
header.Add("Sec-Websocket-Accept", generateAcceptKey(req))
header.Add("Upgrade", "websocket")
return header
}
// the gorilla websocket library sets its own Upgrade, Connection, Sec-WebSocket-Key,
// Sec-WebSocket-Version and Sec-Websocket-Extensions headers.
// https://github.com/gorilla/websocket/blob/master/client.go#L189-L194.
func websocketHeaders(req *http.Request) http.Header {
wsHeaders := make(http.Header)
for key, val := range req.Header {
wsHeaders[key] = val
}
// Assume the header keys are in canonical format.
for _, header := range stripWebsocketHeaders {
wsHeaders.Del(header)
}
wsHeaders.Set("Host", req.Host) // See TUN-1097
return wsHeaders
}
// sha1Base64 sha1 and then base64 encodes str.
func sha1Base64(str string) string {
hasher := sha1.New()
_, _ = io.WriteString(hasher, str)
hash := hasher.Sum(nil)
return base64.StdEncoding.EncodeToString(hash)
}
// generateAcceptKey returns the string needed for the Sec-WebSocket-Accept header.
// https://tools.ietf.org/html/rfc6455#section-1.3 describes this process in more detail.
func generateAcceptKey(req *http.Request) string {
return sha1Base64(req.Header.Get("Sec-WebSocket-Key") + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11")
}
// ChangeRequestScheme is needed as the gorilla websocket library requires the ws scheme.
// (even though it changes it back to http/https, but ¯\_(ツ)_/¯.)
func ChangeRequestScheme(reqURL *url.URL) string {
switch reqURL.Scheme {
case "https":
return "wss"
case "http":
return "ws"
case "":
return "ws"
default:
return reqURL.Scheme
}
}