Function verify

packages/engine.io/lib/server.ts:274–348

* Verifies a request. * * @param {EngineRequest} req * @param upgrade - whether it's an upgrade request * @param fn * @protected * @return whether the request is valid

(
    req: EngineRequest,
    upgrade: boolean,
    fn: ErrorCallback,
  )

   * @return whether the request is valid
   */
  protected verify(
    req: EngineRequest,
    upgrade: boolean,
    fn: ErrorCallback,
  ): void | boolean {
    class="cm">// transport check
    const transport = req._query.transport;
    class="cm">// WebTransport does not go through the verify() method, see the onWebTransportSession() method
    if (
      !~this.opts.transports.indexOf(transport as TransportName) ||
      transport === class="st">"webtransport"
    ) {
      debug(class="st">'unknown transport "%s"', transport);
      return fn(Server.errors.UNKNOWN_TRANSPORT, { transport });
    }

    class="cm">// class="st">'Origin' header check
    const isOriginInvalid = checkInvalidHeaderChar(req.headers.origin);
    if (isOriginInvalid) {
      const origin = req.headers.origin;
      req.headers.origin = null;
      debug(class="st">"origin header invalid");
      return fn(Server.errors.BAD_REQUEST, {
        name: class="st">"INVALID_ORIGIN",
        origin,
      });
    }

    class="cm">// sid check
    const sid = req._query.sid;
    if (sid) {
      if (!hasOwn(this.clients, sid)) {
        debug(class="st">'unknown sid "%s"', sid);
        return fn(Server.errors.UNKNOWN_SID, {
          sid,
        });
      }
      const previousTransport = this.clients[sid].transport.name;
      if (!upgrade && previousTransport !== transport) {
        debug(class="st">"bad request: unexpected transport without upgrade");
        return fn(Server.errors.BAD_REQUEST, {
          name: class="st">"TRANSPORT_MISMATCH",
          transport,
          previousTransport,
        });
      }
    } else {
      class="cm">// handshake is GET only
      if (class="st">"GET" !== req.method) {
        return fn(Server.errors.BAD_HANDSHAKE_METHOD, {
          method: req.method,
        });
      }

      if (transport === class="st">"websocket" && !upgrade) {
        debug(class="st">"invalid transport upgrade");
        return fn(Server.errors.BAD_REQUEST, {
          name: class="st">"TRANSPORT_HANDSHAKE_ERROR",