package websocket import ( "bufio" "crypto/sha1" "crypto/tls" "encoding/base64" "encoding/binary" "encoding/json" "errors" "io" "net" "net/http" "time" "github.com/cloudflare/cloudflared/sshserver" "github.com/gorilla/websocket" "github.com/sirupsen/logrus" ) const ( // Time allowed to write a message to the peer. writeWait = 10 * time.Second // Time allowed to read the next pong message from the peer. pongWait = 60 * time.Second // Send pings to peer with this period. Must be less than pongWait. pingPeriod = (pongWait * 9) / 10 ) var stripWebsocketHeaders = []string{ "Upgrade", "Connection", "Sec-Websocket-Key", "Sec-Websocket-Version", "Sec-Websocket-Extensions", } // Conn is a wrapper around the standard gorilla websocket // but implements a ReadWriter type Conn struct { *websocket.Conn } // Read will read messages from the websocket connection func (c *Conn) Read(p []byte) (int, error) { _, message, err := c.Conn.ReadMessage() if err != nil { return 0, err } return copy(p, message), nil } // Write will write messages to the websocket connection func (c *Conn) Write(p []byte) (int, error) { if err := c.Conn.WriteMessage(websocket.BinaryMessage, p); err != nil { return 0, err } return len(p), nil } // 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, tlsClientConfig *tls.Config) (*websocket.Conn, *http.Response, error) { req.URL.Scheme = changeRequestScheme(req) wsHeaders := websocketHeaders(req) d := &websocket.Dialer{TLSClientConfig: tlsClientConfig} conn, response, err := d.Dial(req.URL.String(), wsHeaders) if err != nil { return nil, response, err } response.Header.Set("Sec-WebSocket-Accept", generateAcceptKey(req)) return conn, response, err } // HijackConnection takes over an HTTP connection. Caller is responsible for closing connection. func HijackConnection(w http.ResponseWriter) (net.Conn, *bufio.ReadWriter, error) { hj, ok := w.(http.Hijacker) if !ok { return nil, nil, errors.New("hijack error") } conn, brw, err := hj.Hijack() if err != nil { return nil, nil, err } return conn, brw, nil } // Stream copies copy data to & from provided io.ReadWriters. func Stream(conn, backendConn io.ReadWriter) { proxyDone := make(chan struct{}, 2) go func() { io.Copy(conn, backendConn) proxyDone <- struct{}{} }() go func() { io.Copy(backendConn, conn) proxyDone <- struct{}{} }() // If one side is done, we are done. <-proxyDone } // StartProxyServer will start a websocket server that will decode // the websocket data and write the resulting data to the provided // address func StartProxyServer(logger *logrus.Logger, listener net.Listener, remote string, shutdownC <-chan struct{}) error { upgrader := websocket.Upgrader{ ReadBufferSize: 1024, WriteBufferSize: 1024, } httpServer := &http.Server{Addr: listener.Addr().String(), Handler: nil} go func() { <-shutdownC httpServer.Close() }() http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { stream, err := net.Dial("tcp", remote) if err != nil { logger.WithError(err).Error("Cannot connect to remote.") return } defer stream.Close() if !websocket.IsWebSocketUpgrade(r) { w.Write(nonWebSocketRequestPage()) return } conn, err := upgrader.Upgrade(w, r, nil) if err != nil { logger.WithError(err).Error("failed to upgrade") return } conn.SetReadDeadline(time.Now().Add(pongWait)) conn.SetPongHandler(func(string) error { conn.SetReadDeadline(time.Now().Add(pongWait)); return nil }) done := make(chan struct{}) go pinger(logger, conn, done) defer func() { done <- struct{}{} conn.Close() }() token := r.Header.Get("cf-access-token") if destination := r.Header.Get("CF-Access-SSH-Destination"); destination != "" { if err := sendSSHPreamble(stream, destination, token); err != nil { logger.WithError(err).Error("Failed to send SSH preamble") return } } Stream(&Conn{conn}, stream) }) return httpServer.Serve(listener) } // sendSSHPreamble sends the final SSH destination address to the cloudflared SSH proxy // The destination is preceded by its length func sendSSHPreamble(stream net.Conn, destination, token string) error { preamble := &sshserver.SSHPreamble{Destination: destination, JWT: token} payload, err := json.Marshal(preamble) if err != nil { return err } if uint16(len(payload)) > ^uint16(0) { return errors.New("ssh preamble payload too large") } sizeBytes := make([]byte, sshserver.SSHPreambleLength) binary.BigEndian.PutUint16(sizeBytes, uint16(len(payload))) if _, err := stream.Write(sizeBytes); err != nil { return err } if _, err := stream.Write(payload); err != nil { return err } return nil } // 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(req *http.Request) string { switch req.URL.Scheme { case "https": return "wss" case "http": return "ws" default: return req.URL.Scheme } } // pinger simulates the websocket connection to keep it alive func pinger(logger *logrus.Logger, ws *websocket.Conn, done chan struct{}) { ticker := time.NewTicker(pingPeriod) defer ticker.Stop() for { select { case <-ticker.C: if err := ws.WriteControl(websocket.PingMessage, []byte{}, time.Now().Add(writeWait)); err != nil { logger.WithError(err).Debug("failed to send ping message") } case <-done: return } } }