6 files changed, 930 insertions, 0 deletions
diff --git a/remote/components/Marionette.sys.mjs b/remote/components/Marionette.sys.mjs
new file mode 100644
index 0000000000..9be05dafae
--- /dev/null
+++ b/remote/components/Marionette.sys.mjs
@@ -0,0 +1,308 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  Preferences: "resource://gre/modules/Preferences.sys.mjs",
+
+  Deferred: "chrome://remote/content/shared/Sync.sys.mjs",
+  EnvironmentPrefs: "chrome://remote/content/marionette/prefs.sys.mjs",
+  Log: "chrome://remote/content/shared/Log.sys.mjs",
+  MarionettePrefs: "chrome://remote/content/marionette/prefs.sys.mjs",
+  RecommendedPreferences:
+    "chrome://remote/content/shared/RecommendedPreferences.sys.mjs",
+  TCPListener: "chrome://remote/content/marionette/server.sys.mjs",
+});
+
+XPCOMUtils.defineLazyGetter(lazy, "logger", () =>
+  lazy.Log.get(lazy.Log.TYPES.MARIONETTE)
+);
+
+XPCOMUtils.defineLazyGetter(lazy, "textEncoder", () => new TextEncoder());
+
+const NOTIFY_LISTENING = "marionette-listening";
+
+// Complements -marionette flag for starting the Marionette server.
+// We also set this if Marionette is running in order to start the server
+// again after a Firefox restart.
+const ENV_ENABLED = "MOZ_MARIONETTE";
+
+// Besides starting based on existing prefs in a profile and a command
+// line flag, we also support inheriting prefs out of an env var, and to
+// start Marionette that way.
+//
+// This allows marionette prefs to persist when we do a restart into
+// a different profile in order to test things like Firefox refresh.
+// The environment variable itself, if present, is interpreted as a
+// JSON structure, with the keys mapping to preference names in the
+// "marionette." branch, and the values to the values of those prefs. So
+// something like {"port": 4444} would result in the marionette.port
+// pref being set to 4444.
+const ENV_PRESERVE_PREFS = "MOZ_MARIONETTE_PREF_STATE_ACROSS_RESTARTS";
+
+// Map of Marionette-specific preferences that should be set via
+// RecommendedPreferences.
+const RECOMMENDED_PREFS = new Map([
+  // Automatically unload beforeunload alerts
+  ["dom.disable_beforeunload", true],
+]);
+
+const isRemote =
+  Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT;
+
+class MarionetteParentProcess {
+  #browserStartupFinished;
+
+  constructor() {
+    this.server = null;
+    this._activePortPath;
+
+    this.classID = Components.ID("{786a1369-dca5-4adc-8486-33d23c88010a}");
+    this.helpInfo = "  --marionette       Enable remote control server.\n";
+
+    // Initially set the enabled state based on the environment variable.
+    this.enabled = Services.env.exists(ENV_ENABLED);
+
+    Services.ppmm.addMessageListener("Marionette:IsRunning", this);
+
+    this.#browserStartupFinished = lazy.Deferred();
+  }
+
+  /**
+   * A promise that resolves when the initial application window has been opened.
+   *
+   * @returns {Promise}
+   *     Promise that resolves when the initial application window is open.
+   */
+  get browserStartupFinished() {
+    return this.#browserStartupFinished.promise;
+  }
+
+  get enabled() {
+    return this._enabled;
+  }
+
+  set enabled(value) {
+    // Return early if Marionette is already marked as being enabled.
+    // There is also no possibility to disable Marionette once it got enabled.
+    if (this._enabled || !value) {
+      return;
+    }
+
+    this._enabled = value;
+    lazy.logger.info(`Marionette enabled`);
+  }
+
+  get running() {
+    return !!this.server && this.server.alive;
+  }
+
+  receiveMessage({ name }) {
+    switch (name) {
+      case "Marionette:IsRunning":
+        return this.running;
+
+      default:
+        lazy.logger.warn("Unknown IPC message to parent process: " + name);
+        return null;
+    }
+  }
+
+  handle(cmdLine) {
+    // `handle` is called too late in certain cases (eg safe mode, see comment
+    // above "command-line-startup"). So the marionette command line argument
+    // will always be processed in `observe`.
+    // However it still needs to be consumed by the command-line-handler API,
+    // to avoid issues on macos.
+    // TODO: remove after Bug 1724251 is fixed.
+    cmdLine.handleFlag("marionette", false);
+  }
+
+  async observe(subject, topic) {
+    if (this.enabled) {
+      lazy.logger.trace(`Received observer notification ${topic}`);
+    }
+
+    switch (topic) {
+      case "profile-after-change":
+        Services.obs.addObserver(this, "command-line-startup");
+        break;
+
+      // In safe mode the command line handlers are getting parsed after the
+      // safe mode dialog has been closed. To allow Marionette to start
+      // earlier, use the CLI startup observer notification for
+      // special-cased handlers, which gets fired before the dialog appears.
+      case "command-line-startup":
+        Services.obs.removeObserver(this, topic);
+
+        this.enabled = subject.handleFlag("marionette", false);
+
+        if (this.enabled) {
+          // Marionette needs to be initialized before any window is shown.
+          Services.obs.addObserver(this, "final-ui-startup");
+
+          // We want to suppress the modal dialog that's shown
+          // when starting up in safe-mode to enable testing.
+          if (Services.appinfo.inSafeMode) {
+            Services.obs.addObserver(this, "domwindowopened");
+          }
+
+          lazy.RecommendedPreferences.applyPreferences(RECOMMENDED_PREFS);
+
+          // Only set preferences to preserve in a new profile
+          // when Marionette is enabled.
+          for (let [pref, value] of lazy.EnvironmentPrefs.from(
+            ENV_PRESERVE_PREFS
+          )) {
+            lazy.Preferences.set(pref, value);
+          }
+        }
+        break;
+
+      case "domwindowopened":
+        Services.obs.removeObserver(this, topic);
+        this.suppressSafeModeDialog(subject);
+        break;
+
+      case "final-ui-startup":
+        Services.obs.removeObserver(this, topic);
+
+        Services.obs.addObserver(this, "browser-idle-startup-tasks-finished");
+        Services.obs.addObserver(this, "mail-idle-startup-tasks-finished");
+        Services.obs.addObserver(this, "quit-application");
+
+        await this.init();
+        break;
+
+      // Used to wait until the initial application window has been opened.
+      case "browser-idle-startup-tasks-finished":
+      case "mail-idle-startup-tasks-finished":
+        Services.obs.removeObserver(
+          this,
+          "browser-idle-startup-tasks-finished"
+        );
+        Services.obs.removeObserver(this, "mail-idle-startup-tasks-finished");
+        this.#browserStartupFinished.resolve();
+        break;
+
+      case "quit-application":
+        Services.obs.removeObserver(this, topic);
+        await this.uninit();
+        break;
+    }
+  }
+
+  suppressSafeModeDialog(win) {
+    win.addEventListener(
+      "load",
+      () => {
+        let dialog = win.document.getElementById("safeModeDialog");
+        if (dialog) {
+          // accept the dialog to start in safe-mode
+          lazy.logger.trace("Safe mode detected, supressing dialog");
+          win.setTimeout(() => {
+            dialog.getButton("accept").click();
+          });
+        }
+      },
+      { once: true }
+    );
+  }
+
+  async init() {
+    if (!this.enabled || this.running) {
+      lazy.logger.debug(
+        `Init aborted (enabled=${this.enabled}, running=${this.running})`
+      );
+      return;
+    }
+
+    try {
+      this.server = new lazy.TCPListener(lazy.MarionettePrefs.port);
+      this.server.start();
+    } catch (e) {
+      lazy.logger.fatal("Marionette server failed to start", e);
+      await this.uninit();
+      Services.startup.quit(Ci.nsIAppStartup.eForceQuit);
+      return;
+    }
+
+    Services.env.set(ENV_ENABLED, "1");
+    Services.obs.notifyObservers(this, NOTIFY_LISTENING, true);
+    lazy.logger.debug("Marionette is listening");
+
+    // Write Marionette port to MarionetteActivePort file within the profile.
+    this._activePortPath = PathUtils.join(
+      PathUtils.profileDir,
+      "MarionetteActivePort"
+    );
+
+    const data = `${this.server.port}`;
+    try {
+      await IOUtils.write(this._activePortPath, lazy.textEncoder.encode(data));
+    } catch (e) {
+      lazy.logger.warn(
+        `Failed to create ${this._activePortPath} (${e.message})`
+      );
+    }
+  }
+
+  async uninit() {
+    if (this.running) {
+      this.server.stop();
+      Services.obs.notifyObservers(this, NOTIFY_LISTENING);
+      lazy.logger.debug("Marionette stopped listening");
+
+      try {
+        await IOUtils.remove(this._activePortPath);
+      } catch (e) {
+        lazy.logger.warn(
+          `Failed to remove ${this._activePortPath} (${e.message})`
+        );
+      }
+    }
+  }
+
+  get QueryInterface() {
+    return ChromeUtils.generateQI([
+      "nsICommandLineHandler",
+      "nsIMarionette",
+      "nsIObserver",
+    ]);
+  }
+}
+
+class MarionetteContentProcess {
+  constructor() {
+    this.classID = Components.ID("{786a1369-dca5-4adc-8486-33d23c88010a}");
+  }
+
+  get running() {
+    let reply = Services.cpmm.sendSyncMessage("Marionette:IsRunning");
+    if (!reply.length) {
+      lazy.logger.warn("No reply from parent process");
+      return false;
+    }
+    return reply[0];
+  }
+
+  get QueryInterface() {
+    return ChromeUtils.generateQI(["nsIMarionette"]);
+  }
+}
+
+export var Marionette;
+if (isRemote) {
+  Marionette = new MarionetteContentProcess();
+} else {
+  Marionette = new MarionetteParentProcess();
+}
+
+// This is used by the XPCOM codepath which expects a constructor
+export const MarionetteFactory = function() {
+  return Marionette;
+};
diff --git a/remote/components/RemoteAgent.sys.mjs b/remote/components/RemoteAgent.sys.mjs
new file mode 100644
index 0000000000..ca3e8da880
--- /dev/null
+++ b/remote/components/RemoteAgent.sys.mjs
@@ -0,0 +1,523 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  CDP: "chrome://remote/content/cdp/CDP.sys.mjs",
+  Deferred: "chrome://remote/content/shared/Sync.sys.mjs",
+  Log: "chrome://remote/content/shared/Log.sys.mjs",
+  WebDriverBiDi: "chrome://remote/content/webdriver-bidi/WebDriverBiDi.sys.mjs",
+});
+
+XPCOMUtils.defineLazyModuleGetters(lazy, {
+  HttpServer: "chrome://remote/content/server/HTTPD.jsm",
+});
+
+XPCOMUtils.defineLazyGetter(lazy, "logger", () => lazy.Log.get());
+
+XPCOMUtils.defineLazyGetter(lazy, "activeProtocols", () => {
+  const protocols = Services.prefs.getIntPref("remote.active-protocols");
+  if (protocols < 1 || protocols > 3) {
+    throw Error(`Invalid remote protocol identifier: ${protocols}`);
+  }
+
+  return protocols;
+});
+
+const WEBDRIVER_BIDI_ACTIVE = 0x1;
+const CDP_ACTIVE = 0x2;
+
+const DEFAULT_HOST = "localhost";
+const DEFAULT_PORT = 9222;
+
+const isRemote =
+  Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT;
+
+class RemoteAgentParentProcess {
+  #allowHosts;
+  #allowOrigins;
+  #browserStartupFinished;
+  #classID;
+  #enabled;
+  #host;
+  #port;
+  #server;
+
+  #cdp;
+  #webDriverBiDi;
+
+  constructor() {
+    this.#allowHosts = null;
+    this.#allowOrigins = null;
+    this.#browserStartupFinished = lazy.Deferred();
+    this.#classID = Components.ID("{8f685a9d-8181-46d6-a71d-869289099c6d}");
+    this.#enabled = false;
+
+    // Configuration for httpd.js
+    this.#host = DEFAULT_HOST;
+    this.#port = DEFAULT_PORT;
+    this.#server = null;
+
+    // Supported protocols
+    this.#cdp = null;
+    this.#webDriverBiDi = null;
+
+    Services.ppmm.addMessageListener("RemoteAgent:IsRunning", this);
+  }
+
+  get allowHosts() {
+    if (this.#allowHosts !== null) {
+      return this.#allowHosts;
+    }
+
+    if (this.#server) {
+      // If the server is bound to a hostname, not an IP address, return it as
+      // allowed host.
+      const hostUri = Services.io.newURI(`https://${this.#host}`);
+      if (!this.#isIPAddress(hostUri)) {
+        return [RemoteAgent.host];
+      }
+
+      // Following Bug 1220810 localhost is guaranteed to resolve to a loopback
+      // address (127.0.0.1 or ::1) unless network.proxy.allow_hijacking_localhost
+      // is set to true, which should not be the case.
+      const loopbackAddresses = ["127.0.0.1", "[::1]"];
+
+      // If the server is bound to an IP address and this IP address is a localhost
+      // loopback address, return localhost as allowed host.
+      if (loopbackAddresses.includes(this.#host)) {
+        return ["localhost"];
+      }
+    }
+
+    // Otherwise return an empty array.
+    return [];
+  }
+
+  get allowOrigins() {
+    return this.#allowOrigins;
+  }
+
+  /**
+   * A promise that resolves when the initial application window has been opened.
+   *
+   * @returns {Promise}
+   *     Promise that resolves when the initial application window is open.
+   */
+  get browserStartupFinished() {
+    return this.#browserStartupFinished.promise;
+  }
+
+  get cdp() {
+    return this.#cdp;
+  }
+
+  get debuggerAddress() {
+    if (!this.#server) {
+      return "";
+    }
+
+    return `${this.#host}:${this.#port}`;
+  }
+
+  get enabled() {
+    return this.#enabled;
+  }
+
+  get host() {
+    return this.#host;
+  }
+
+  get port() {
+    return this.#port;
+  }
+
+  get running() {
+    return !!this.#server && !this.#server.isStopped();
+  }
+
+  get scheme() {
+    return this.#server?.identity.primaryScheme;
+  }
+
+  get server() {
+    return this.#server;
+  }
+
+  get webDriverBiDi() {
+    return this.#webDriverBiDi;
+  }
+
+  /**
+   * Check if the provided URI's host is an IP address.
+   *
+   * @param {nsIURI} uri
+   *     The URI to check.
+   * @return {boolean}
+   */
+  #isIPAddress(uri) {
+    try {
+      // getBaseDomain throws an explicit error if the uri host is an IP address.
+      Services.eTLD.getBaseDomain(uri);
+    } catch (e) {
+      return e.result == Cr.NS_ERROR_HOST_IS_IP_ADDRESS;
+    }
+    return false;
+  }
+
+  handle(cmdLine) {
+    // remote-debugging-port has to be consumed in nsICommandLineHandler:handle
+    // to avoid issues on macos. See Marionette.jsm::handle() for more details.
+    // TODO: remove after Bug 1724251 is fixed.
+    try {
+      cmdLine.handleFlagWithParam("remote-debugging-port", false);
+    } catch (e) {
+      cmdLine.handleFlag("remote-debugging-port", false);
+    }
+  }
+
+  async #listen(port) {
+    if (Services.appinfo.processType != Ci.nsIXULRuntime.PROCESS_TYPE_DEFAULT) {
+      throw Components.Exception(
+        "May only be instantiated in parent process",
+        Cr.NS_ERROR_LAUNCHED_CHILD_PROCESS
+      );
+    }
+
+    if (this.running) {
+      return;
+    }
+
+    // Try to resolve localhost to an IPv4  and / or IPv6 address so that the
+    // server can be started on a given IP. Only fallback to use localhost if
+    // the hostname cannot be resolved.
+    //
+    // Note: This doesn't force httpd.js to use the dual stack support.
+    let isIPv4Host = false;
+    try {
+      const addresses = await this.#resolveHostname(DEFAULT_HOST);
+      lazy.logger.trace(
+        `Available local IP addresses: ${addresses.join(", ")}`
+      );
+
+      // Prefer IPv4 over IPv6 addresses.
+      const addressesIPv4 = addresses.filter(value => !value.includes(":"));
+      isIPv4Host = !!addressesIPv4.length;
+      if (isIPv4Host) {
+        this.#host = addressesIPv4[0];
+      } else {
+        this.#host = addresses.length ? addresses[0] : DEFAULT_HOST;
+      }
+    } catch (e) {
+      this.#host = DEFAULT_HOST;
+
+      lazy.logger.debug(
+        `Failed to resolve hostname "localhost" to IP address: ${e.message}`
+      );
+    }
+
+    // nsIServerSocket uses -1 for atomic port allocation
+    if (port === 0) {
+      port = -1;
+    }
+
+    try {
+      // Bug 1783938: httpd.js refuses connections when started on a IPv4
+      // address. As workaround start on localhost and add another identity
+      // for that IP address.
+      this.#server = new lazy.HttpServer();
+      const host = isIPv4Host ? DEFAULT_HOST : this.#host;
+      this.server._start(port, host);
+      this.#port = this.server._port;
+
+      if (isIPv4Host) {
+        this.server.identity.add("http", this.#host, this.#port);
+      }
+
+      Services.obs.notifyObservers(null, "remote-listening", true);
+
+      await Promise.all([this.#webDriverBiDi?.start(), this.#cdp?.start()]);
+    } catch (e) {
+      await this.#stop();
+      lazy.logger.error(`Unable to start remote agent: ${e.message}`, e);
+    }
+  }
+
+  /**
+   * Resolves a hostname to one or more IP addresses.
+   *
+   * @param {string} hostname
+   *
+   * @returns {Array<string>}
+   */
+  #resolveHostname(hostname) {
+    return new Promise((resolve, reject) => {
+      let originalRequest;
+
+      const onLookupCompleteListener = {
+        onLookupComplete(request, record, status) {
+          if (request === originalRequest) {
+            if (!Components.isSuccessCode(status)) {
+              reject({ message: ChromeUtils.getXPCOMErrorName(status) });
+              return;
+            }
+
+            record.QueryInterface(Ci.nsIDNSAddrRecord);
+
+            const addresses = [];
+            while (record.hasMore()) {
+              let addr = record.getNextAddrAsString();
+              if (addr.includes(":") && !addr.startsWith("[")) {
+                // Make sure that the IPv6 address is wrapped with brackets.
+                addr = `[${addr}]`;
+              }
+              if (!addresses.includes(addr)) {
+                // Sometimes there are duplicate records with the same IP.
+                addresses.push(addr);
+              }
+            }
+
+            resolve(addresses);
+          }
+        },
+      };
+
+      try {
+        originalRequest = Services.dns.asyncResolve(
+          hostname,
+          Ci.nsIDNSService.RESOLVE_TYPE_DEFAULT,
+          Ci.nsIDNSService.RESOLVE_BYPASS_CACHE,
+          null,
+          onLookupCompleteListener,
+          null, //Services.tm.mainThread,
+          {} /* defaultOriginAttributes */
+        );
+      } catch (e) {
+        reject({ message: e.message });
+      }
+    });
+  }
+
+  async #stop() {
+    if (!this.running) {
+      return;
+    }
+
+    try {
+      // Stop the CDP support before stopping the server.
+      // Otherwise the HTTP server will fail to stop.
+      await this.#cdp?.stop();
+      await this.#webDriverBiDi?.stop();
+
+      await this.#server.stop();
+      this.#server = null;
+      Services.obs.notifyObservers(null, "remote-listening");
+    } catch (e) {
+      // this function must never fail
+      lazy.logger.error("unable to stop listener", e);
+    }
+  }
+
+  /**
+   * Handle the --remote-debugging-port command line argument.
+   *
+   * @param {nsICommandLine} cmdLine
+   *     Instance of the command line interface.
+   *
+   * @return {boolean}
+   *     Return `true` if the command line argument has been found.
+   */
+  handleRemoteDebuggingPortFlag(cmdLine) {
+    let enabled = false;
+
+    try {
+      // Catch cases when the argument, and a port have been specified.
+      const port = cmdLine.handleFlagWithParam("remote-debugging-port", false);
+      if (port !== null) {
+        enabled = true;
+
+        // In case of an invalid port keep the default port
+        const parsed = Number(port);
+        if (!isNaN(parsed)) {
+          this.#port = parsed;
+        }
+      }
+    } catch (e) {
+      // If no port has been given check for the existence of the argument.
+      enabled = cmdLine.handleFlag("remote-debugging-port", false);
+    }
+
+    return enabled;
+  }
+
+  handleAllowHostsFlag(cmdLine) {
+    try {
+      const hosts = cmdLine.handleFlagWithParam("remote-allow-hosts", false);
+      return hosts.split(",");
+    } catch (e) {
+      return null;
+    }
+  }
+
+  handleAllowOriginsFlag(cmdLine) {
+    try {
+      const origins = cmdLine.handleFlagWithParam(
+        "remote-allow-origins",
+        false
+      );
+      return origins.split(",");
+    } catch (e) {
+      return null;
+    }
+  }
+
+  async observe(subject, topic) {
+    if (this.#enabled) {
+      lazy.logger.trace(`Received observer notification ${topic}`);
+    }
+
+    switch (topic) {
+      case "profile-after-change":
+        Services.obs.addObserver(this, "command-line-startup");
+        break;
+
+      case "command-line-startup":
+        Services.obs.removeObserver(this, topic);
+
+        this.#enabled = this.handleRemoteDebuggingPortFlag(subject);
+
+        if (this.#enabled) {
+          Services.obs.addObserver(this, "final-ui-startup");
+
+          this.#allowHosts = this.handleAllowHostsFlag(subject);
+          this.#allowOrigins = this.handleAllowOriginsFlag(subject);
+
+          Services.obs.addObserver(this, "browser-idle-startup-tasks-finished");
+          Services.obs.addObserver(this, "mail-idle-startup-tasks-finished");
+          Services.obs.addObserver(this, "quit-application");
+
+          // With Bug 1717899 we will extend the lifetime of the Remote Agent to
+          // the whole Firefox session, which will be identical to Marionette. For
+          // now prevent logging if the component is not enabled during startup.
+          if (
+            (lazy.activeProtocols & WEBDRIVER_BIDI_ACTIVE) ===
+            WEBDRIVER_BIDI_ACTIVE
+          ) {
+            this.#webDriverBiDi = new lazy.WebDriverBiDi(this);
+            if (this.#enabled) {
+              lazy.logger.debug("WebDriver BiDi enabled");
+            }
+          }
+
+          if ((lazy.activeProtocols & CDP_ACTIVE) === CDP_ACTIVE) {
+            this.#cdp = new lazy.CDP(this);
+            if (this.#enabled) {
+              lazy.logger.debug("CDP enabled");
+            }
+          }
+        }
+        break;
+
+      case "final-ui-startup":
+        Services.obs.removeObserver(this, topic);
+
+        try {
+          await this.#listen(this.#port);
+        } catch (e) {
+          throw Error(`Unable to start remote agent: ${e}`);
+        }
+
+        break;
+
+      // Used to wait until the initial application window has been opened.
+      case "browser-idle-startup-tasks-finished":
+      case "mail-idle-startup-tasks-finished":
+        Services.obs.removeObserver(
+          this,
+          "browser-idle-startup-tasks-finished"
+        );
+        Services.obs.removeObserver(this, "mail-idle-startup-tasks-finished");
+        this.#browserStartupFinished.resolve();
+        break;
+
+      // Listen for application shutdown to also shutdown the Remote Agent
+      // and a possible running instance of httpd.js.
+      case "quit-application":
+        Services.obs.removeObserver(this, topic);
+        this.#stop();
+        break;
+    }
+  }
+
+  receiveMessage({ name }) {
+    switch (name) {
+      case "RemoteAgent:IsRunning":
+        return this.running;
+
+      default:
+        lazy.logger.warn("Unknown IPC message to parent process: " + name);
+        return null;
+    }
+  }
+
+  // XPCOM
+
+  get classID() {
+    return this.#classID;
+  }
+
+  get helpInfo() {
+    return `  --remote-debugging-port [<port>] Start the Firefox Remote Agent,
+                     which is a low-level remote debugging interface used for WebDriver
+                     BiDi and CDP. Defaults to port 9222.
+  --remote-allow-hosts <hosts> Values of the Host header to allow for incoming requests.
+                     Please read security guidelines at https://firefox-source-docs.mozilla.org/remote/Security.html
+  --remote-allow-origins <origins> Values of the Origin header to allow for incoming requests.
+                     Please read security guidelines at https://firefox-source-docs.mozilla.org/remote/Security.html\n`;
+  }
+
+  get QueryInterface() {
+    return ChromeUtils.generateQI([
+      "nsICommandLineHandler",
+      "nsIObserver",
+      "nsIRemoteAgent",
+    ]);
+  }
+}
+
+class RemoteAgentContentProcess {
+  #classID;
+
+  constructor() {
+    this.#classID = Components.ID("{8f685a9d-8181-46d6-a71d-869289099c6d}");
+  }
+
+  get running() {
+    let reply = Services.cpmm.sendSyncMessage("RemoteAgent:IsRunning");
+    if (!reply.length) {
+      lazy.logger.warn("No reply from parent process");
+      return false;
+    }
+    return reply[0];
+  }
+
+  get QueryInterface() {
+    return ChromeUtils.generateQI(["nsIRemoteAgent"]);
+  }
+}
+
+export var RemoteAgent;
+if (isRemote) {
+  RemoteAgent = new RemoteAgentContentProcess();
+} else {
+  RemoteAgent = new RemoteAgentParentProcess();
+}
+
+// This is used by the XPCOM codepath which expects a constructor
+export var RemoteAgentFactory = function() {
+  return RemoteAgent;
+};
diff --git a/remote/components/components.conf b/remote/components/components.conf
new file mode 100644
index 0000000000..e518af3dd5
--- /dev/null
+++ b/remote/components/components.conf
@@ -0,0 +1,29 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Classes = [
+    # Remote Agent
+    {
+        "cid": "{8f685a9d-8181-46d6-a71d-869289099c6d}",
+        "contract_ids": ["@mozilla.org/remote/agent;1"],
+        "categories": {
+            "command-line-handler": "m-remote",
+            "profile-after-change": "RemoteAgent",
+        },
+        'esModule': "chrome://remote/content/components/RemoteAgent.sys.mjs",
+        "constructor": "RemoteAgentFactory",
+    },
+
+    # Marionette
+    {
+        "cid": "{786a1369-dca5-4adc-8486-33d23c88010a}",
+        "contract_ids": ["@mozilla.org/remote/marionette;1"],
+        "categories": {
+            "command-line-handler": "m-marionette",
+            "profile-after-change": "Marionette",
+        },
+        'esModule': "chrome://remote/content/components/Marionette.sys.mjs",
+        "constructor": "MarionetteFactory",
+    },
+]
diff --git a/remote/components/moz.build b/remote/components/moz.build
new file mode 100644
index 0000000000..99b56e2add
--- /dev/null
+++ b/remote/components/moz.build
@@ -0,0 +1,17 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+XPIDL_MODULE = "remote"
+
+XPIDL_SOURCES += [
+    "nsIMarionette.idl",
+    "nsIRemoteAgent.idl",
+]
+
+XPCOM_MANIFESTS += ["components.conf"]
+
+with Files("Marionette.sys.mjs"):
+    BUG_COMPONENT = ("Testing", "Marionette")
+with Files("nsIMarionette.idl"):
+    BUG_COMPONENT = ("Testing", "Marionette")
diff --git a/remote/components/nsIMarionette.idl b/remote/components/nsIMarionette.idl
new file mode 100644
index 0000000000..c10bf4b17b
--- /dev/null
+++ b/remote/components/nsIMarionette.idl
@@ -0,0 +1,17 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+%{C++
+#define NS_MARIONETTE_CONTRACTID "@mozilla.org/remote/marionette;1"
+%}
+
+/** Interface for accessing the Marionette server instance. */
+[scriptable, uuid(13fa7d76-f976-4711-a00c-29ac9c1881e1)]
+interface nsIMarionette : nsISupports
+{
+  /** Indicates whether Marionette is running. */
+  readonly attribute boolean running;
+};
diff --git a/remote/components/nsIRemoteAgent.idl b/remote/components/nsIRemoteAgent.idl
new file mode 100644
index 0000000000..89d637bed2
--- /dev/null
+++ b/remote/components/nsIRemoteAgent.idl
@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsISupports.idl"
+
+/**
+ * The Gecko remote agent is an RPC subsystem that exposes
+ * browser-internal interfaces and services to the surrounding
+ * system.
+ *
+ * Consumers, whether remote or browser-local, can interface with
+ * the browser through an assorted set of services ranging from
+ * document introspection and script evaluation, to instrumentation,
+ * user interaction simulation, and event subscription.
+ */
+[scriptable, uuid(8f685a9d-8181-46d6-a71d-869289099c6d)]
+interface nsIRemoteAgent : nsISupports
+{
+  /**
+   * Address of the HTTP server under which the remote agent is reachable.
+   */
+  readonly attribute AString debuggerAddress;
+
+  /**
+   * Indicates whether the Remote Agent is running.
+   */
+  readonly attribute boolean running;
+};
+
+%{C++
+#define NS_REMOTEAGENT_CONTRACTID "@mozilla.org/remote/agent;1"
+#define NS_REMOTEAGENT_CID \
+  { 0x8f685a9d, 0x8181, 0x46d6, \
+    { 0xa7, 0x1d, x86, x92, x89, x09, x9c, x6d } }
+%}