Introduce ServerAdapter

Summary:
Introduce ServerAdapter which should be used as a base class for different server implementations e.g. RSocket, WebSocket.

The type is not used elsewhere at this point but this is a good chance to look at the API and suggest changes and/or improvements.

Reviewed By: passy

Differential Revision: D29958434

fbshipit-source-id: 50ba46332d40e836b0a87bcf354d3237bf8fe7c5

desktop/app/src/comms/ServerAdapter.tsx

@@ -0,0 +1,173 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import {
+  CertificateExchangeMedium,
+  SecureServerConfig,
+} from '../utils/CertificateProvider';
+import Client, {ClientQuery} from '../Client';
+import {ClientConnection} from './ClientConnection';
+import {transformCertificateExchangeMediumToType} from './Utilities';
+
+/**
+ * ClientCsrQuery defines a client query with CSR
+ * information.
+ */
+export type ClientCsrQuery = {
+  csr?: string | undefined;
+  csr_path?: string | undefined;
+};
+
+/**
+ * SecureClientQuery combines a ClientQuery with
+ * ClientCsrQuery. It also adds medium information.
+ */
+export type SecureClientQuery = ClientQuery &
+  ClientCsrQuery & {medium: number | undefined};
+
+/**
+ * Defines an interface for events triggered by a running server interacting
+ * with a client.
+ */
+export interface ServerEventsListener {
+  /**
+   * Server started and listening at the specified port.
+   * @param port The port in which the server is listening to.
+   */
+  onListening(port: number): void;
+  /**
+   * An insecure connection attempt has been made by a client. At this
+   * point, a connection should be already be available but needs to be
+   * validated by the server.
+   * @param clientQuery A ClientQuery instance containing metadata about
+   * the client e.g. OS, device, app, etc.
+   */
+  onConnectionAttempt(clientQuery: ClientQuery): void;
+  /**
+   * A TLS connection attempt has been made by a client. At this
+   * point, a connection should be already be available but needs to be
+   * validated by the server.
+   * @param clientQuery A SecureClientQuery instance containing metadata about
+   * the client and CSR information as exchanged on the previously
+   * established insecure connection.
+   */
+  onSecureConnectionAttempt(clientQuery: SecureClientQuery): void;
+  /**
+   * CSR received by the server and needs to be processed. If successfully
+   * processed, it should return a generated device identifier.
+   * @param unsanitizedCSR CSR as sent by the client, will need to be sanitized
+   * before usage.
+   * @param clientQuery A ClientQuery instance containing metadata about
+   * the client e.g. OS, device, app, etc.
+   * @param appDirectory App directory in which to deploy the CA and client
+   * certificates.
+   * @param medium Certificate exchange medium type e.g. FS_ACCESS, WWW.
+   */
+  onProcessCSR(
+    unsanitizedCSR: string,
+    clientQuery: ClientQuery,
+    appDirectory: string,
+    medium: CertificateExchangeMedium,
+  ): Promise<{deviceId: string}>;
+  /**
+   * A secure connection has been established with a validated client.
+   * A promise to a Client instance needs to be returned.
+   * @param clientQuery A SecureClientQuery instance containing metadata about
+   * the client and CSR information as exchanged on the previously
+   * established insecure connection.
+   * @param clientConnection A valid client connection.
+   */
+  onConnectionCreated(
+    clientQuery: SecureClientQuery,
+    clientConnection: ClientConnection,
+  ): Promise<Client>;
+  /**
+   * A connection with a client has been closed.
+   * @param id The client identifier.
+   */
+  onConnectionClosed(id: string): void;
+  /**
+   * An error has occurred.
+   * @param error An Error instance.
+   */
+  onError(error: Error): void;
+}
+
+/**
+ * Defines the base class to be used by any server implementation e.g.
+ * RSocket, WebSocket, etc.
+ */
+abstract class ServerAdapter {
+  listener: ServerEventsListener;
+
+  constructor(listener: ServerEventsListener) {
+    this.listener = listener;
+  }
+
+  /**
+   * Start and bind server to the specified port.
+   * @param port A port number.
+   * @param sslConfig An optional SSL configuration to be used for
+   * TLS servers.
+   */
+  abstract start(
+    port: number,
+    sslConfig?: SecureServerConfig,
+  ): Promise<boolean>;
+  /**
+   * Stop the server.
+   */
+  abstract stop(): Promise<void>;
+
+  /**
+   * Handle a message received over an insecure connection. The only
+   * supported message is to sign certificates.
+   * @param clientQuery A ClientQuery instance containing metadata about
+   * the client e.g. OS, device, app, etc.
+   * @param rawData Raw data as sent by the client.
+   * @returns The response to be sent back to the client. If the received
+   * request is to sign a certificate and no errors were found, the response
+   * should contain the device identifier to use by the client.
+   */
+  async _onHandleUntrustedMessage(
+    clientQuery: ClientQuery,
+    rawData: any,
+  ): Promise<any> {
+    // OSS's older Client SDK might not send medium information.
+    // This is not an issue for internal FB users, as Flipper release
+    // is insync with client SDK through launcher.
+    const message: {
+      method: 'signCertificate';
+      csr: string;
+      destination: string;
+      medium: number | undefined;
+    } = rawData;
+
+    if (message.method === 'signCertificate') {
+      console.debug('CSR received from device', 'server');
+
+      const {csr, destination, medium} = message;
+
+      const result = await this.listener.onProcessCSR(
+        csr,
+        clientQuery,
+        destination,
+        transformCertificateExchangeMediumToType(medium),
+      );
+      const response = JSON.stringify({
+        deviceId: result.deviceId,
+      });
+      return response;
+    }
+
+    return Promise.resolve();
+  }
+}
+
+export default ServerAdapter;