Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 756 insertions, 0 deletions

diff --git a/services/fxaccounts/FxAccountsWebChannel.sys.mjs b/services/fxaccounts/FxAccountsWebChannel.sys.mjs
new file mode 100644
index 0000000000..a231608473
--- /dev/null
+++ b/services/fxaccounts/FxAccountsWebChannel.sys.mjs
@@ -0,0 +1,756 @@
+/* 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/. */
+
+/**
+ * Firefox Accounts Web Channel.
+ *
+ * Uses the WebChannel component to receive messages
+ * about account state changes.
+ */
+
+import { XPCOMUtils } from "resource://gre/modules/XPCOMUtils.sys.mjs";
+
+const {
+  COMMAND_PROFILE_CHANGE,
+  COMMAND_LOGIN,
+  COMMAND_LOGOUT,
+  COMMAND_DELETE,
+  COMMAND_CAN_LINK_ACCOUNT,
+  COMMAND_SYNC_PREFERENCES,
+  COMMAND_CHANGE_PASSWORD,
+  COMMAND_FXA_STATUS,
+  COMMAND_PAIR_HEARTBEAT,
+  COMMAND_PAIR_SUPP_METADATA,
+  COMMAND_PAIR_AUTHORIZE,
+  COMMAND_PAIR_DECLINE,
+  COMMAND_PAIR_COMPLETE,
+  COMMAND_PAIR_PREFERENCES,
+  COMMAND_FIREFOX_VIEW,
+  FX_OAUTH_CLIENT_ID,
+  ON_PROFILE_CHANGE_NOTIFICATION,
+  PREF_LAST_FXA_USER,
+  WEBCHANNEL_ID,
+  log,
+  logPII,
+} = ChromeUtils.import("resource://gre/modules/FxAccountsCommon.js");
+
+const lazy = {};
+
+ChromeUtils.defineESModuleGetters(lazy, {
+  CryptoUtils: "resource://services-crypto/utils.sys.mjs",
+  FxAccountsPairingFlow: "resource://gre/modules/FxAccountsPairing.sys.mjs",
+  FxAccountsStorageManagerCanStoreField:
+    "resource://gre/modules/FxAccountsStorage.sys.mjs",
+  PrivateBrowsingUtils: "resource://gre/modules/PrivateBrowsingUtils.sys.mjs",
+  Weave: "resource://services-sync/main.sys.mjs",
+  WebChannel: "resource://gre/modules/WebChannel.sys.mjs",
+});
+XPCOMUtils.defineLazyGetter(lazy, "fxAccounts", () => {
+  return ChromeUtils.importESModule(
+    "resource://gre/modules/FxAccounts.sys.mjs"
+  ).getFxAccountsSingleton();
+});
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "pairingEnabled",
+  "identity.fxaccounts.pairing.enabled"
+);
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "separatePrivilegedMozillaWebContentProcess",
+  "browser.tabs.remote.separatePrivilegedMozillaWebContentProcess",
+  false
+);
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "separatedMozillaDomains",
+  "browser.tabs.remote.separatedMozillaDomains",
+  "",
+  false,
+  val => val.split(",")
+);
+XPCOMUtils.defineLazyPreferenceGetter(
+  lazy,
+  "accountServer",
+  "identity.fxaccounts.remote.root",
+  null,
+  false,
+  val => Services.io.newURI(val)
+);
+
+// These engines were added years after Sync had been introduced, they need
+// special handling since they are system add-ons and are un-available on
+// older versions of Firefox.
+const EXTRA_ENGINES = ["addresses", "creditcards"];
+
+/**
+ * A helper function that extracts the message and stack from an error object.
+ * Returns a `{ message, stack }` tuple. `stack` will be null if the error
+ * doesn't have a stack trace.
+ */
+function getErrorDetails(error) {
+  // Replace anything that looks like it might be a filepath on Windows or Unix
+  let cleanMessage = String(error)
+    .replace(/\\.*\\/gm, "[REDACTED]")
+    .replace(/\/.*\//gm, "[REDACTED]");
+  let details = { message: cleanMessage, stack: null };
+
+  // Adapted from Console.sys.mjs.
+  if (error.stack) {
+    let frames = [];
+    for (let frame = error.stack; frame; frame = frame.caller) {
+      frames.push(String(frame).padStart(4));
+    }
+    details.stack = frames.join("\n");
+  }
+
+  return details;
+}
+
+/**
+ * Create a new FxAccountsWebChannel to listen for account updates
+ *
+ * @param {Object} options Options
+ *   @param {Object} options
+ *     @param {String} options.content_uri
+ *     The FxA Content server uri
+ *     @param {String} options.channel_id
+ *     The ID of the WebChannel
+ *     @param {String} options.helpers
+ *     Helpers functions. Should only be passed in for testing.
+ * @constructor
+ */
+export function FxAccountsWebChannel(options) {
+  if (!options) {
+    throw new Error("Missing configuration options");
+  }
+  if (!options.content_uri) {
+    throw new Error("Missing 'content_uri' option");
+  }
+  this._contentUri = options.content_uri;
+
+  if (!options.channel_id) {
+    throw new Error("Missing 'channel_id' option");
+  }
+  this._webChannelId = options.channel_id;
+
+  // options.helpers is only specified by tests.
+  XPCOMUtils.defineLazyGetter(this, "_helpers", () => {
+    return options.helpers || new FxAccountsWebChannelHelpers(options);
+  });
+
+  this._setupChannel();
+}
+
+FxAccountsWebChannel.prototype = {
+  /**
+   * WebChannel that is used to communicate with content page
+   */
+  _channel: null,
+
+  /**
+   * Helpers interface that does the heavy lifting.
+   */
+  _helpers: null,
+
+  /**
+   * WebChannel ID.
+   */
+  _webChannelId: null,
+  /**
+   * WebChannel origin, used to validate origin of messages
+   */
+  _webChannelOrigin: null,
+
+  /**
+   * Release all resources that are in use.
+   */
+  tearDown() {
+    this._channel.stopListening();
+    this._channel = null;
+    this._channelCallback = null;
+  },
+
+  /**
+   * Configures and registers a new WebChannel
+   *
+   * @private
+   */
+  _setupChannel() {
+    // if this.contentUri is present but not a valid URI, then this will throw an error.
+    try {
+      this._webChannelOrigin = Services.io.newURI(this._contentUri);
+      this._registerChannel();
+    } catch (e) {
+      log.error(e);
+      throw e;
+    }
+  },
+
+  _receiveMessage(message, sendingContext) {
+    const { command, data } = message;
+    let shouldCheckRemoteType =
+      lazy.separatePrivilegedMozillaWebContentProcess &&
+      lazy.separatedMozillaDomains.some(function (val) {
+        return (
+          lazy.accountServer.asciiHost == val ||
+          lazy.accountServer.asciiHost.endsWith("." + val)
+        );
+      });
+    let { currentRemoteType } = sendingContext.browsingContext;
+    if (shouldCheckRemoteType && currentRemoteType != "privilegedmozilla") {
+      log.error(
+        `Rejected FxA webchannel message from remoteType = ${currentRemoteType}`
+      );
+      return;
+    }
+
+    let browser = sendingContext.browsingContext.top.embedderElement;
+    switch (command) {
+      case COMMAND_PROFILE_CHANGE:
+        Services.obs.notifyObservers(
+          null,
+          ON_PROFILE_CHANGE_NOTIFICATION,
+          data.uid
+        );
+        break;
+      case COMMAND_LOGIN:
+        this._helpers
+          .login(data)
+          .catch(error => this._sendError(error, message, sendingContext));
+        break;
+      case COMMAND_LOGOUT:
+      case COMMAND_DELETE:
+        this._helpers
+          .logout(data.uid)
+          .catch(error => this._sendError(error, message, sendingContext));
+        break;
+      case COMMAND_CAN_LINK_ACCOUNT:
+        let canLinkAccount = this._helpers.shouldAllowRelink(data.email);
+
+        let response = {
+          command,
+          messageId: message.messageId,
+          data: { ok: canLinkAccount },
+        };
+
+        log.debug("FxAccountsWebChannel response", response);
+        this._channel.send(response, sendingContext);
+        break;
+      case COMMAND_SYNC_PREFERENCES:
+        this._helpers.openSyncPreferences(browser, data.entryPoint);
+        break;
+      case COMMAND_PAIR_PREFERENCES:
+        if (lazy.pairingEnabled) {
+          let window = browser.ownerGlobal;
+          // We should close the FxA tab after we open our pref page
+          let selectedTab = window.gBrowser.selectedTab;
+          window.switchToTabHavingURI(
+            "about:preferences?action=pair#sync",
+            true,
+            {
+              ignoreQueryString: true,
+              replaceQueryString: true,
+              adoptIntoActiveWindow: true,
+              ignoreFragment: "whenComparing",
+              triggeringPrincipal:
+                Services.scriptSecurityManager.getSystemPrincipal(),
+            }
+          );
+          // close the tab
+          window.gBrowser.removeTab(selectedTab);
+        }
+        break;
+      case COMMAND_FIREFOX_VIEW:
+        this._helpers.openFirefoxView(browser, data.entryPoint);
+        break;
+      case COMMAND_CHANGE_PASSWORD:
+        this._helpers
+          .changePassword(data)
+          .catch(error => this._sendError(error, message, sendingContext));
+        break;
+      case COMMAND_FXA_STATUS:
+        log.debug("fxa_status received");
+
+        const service = data && data.service;
+        const isPairing = data && data.isPairing;
+        const context = data && data.context;
+        this._helpers
+          .getFxaStatus(service, sendingContext, isPairing, context)
+          .then(fxaStatus => {
+            let response = {
+              command,
+              messageId: message.messageId,
+              data: fxaStatus,
+            };
+            this._channel.send(response, sendingContext);
+          })
+          .catch(error => this._sendError(error, message, sendingContext));
+        break;
+      case COMMAND_PAIR_HEARTBEAT:
+      case COMMAND_PAIR_SUPP_METADATA:
+      case COMMAND_PAIR_AUTHORIZE:
+      case COMMAND_PAIR_DECLINE:
+      case COMMAND_PAIR_COMPLETE:
+        log.debug(`Pairing command ${command} received`);
+        const { channel_id: channelId } = data;
+        delete data.channel_id;
+        const flow = lazy.FxAccountsPairingFlow.get(channelId);
+        if (!flow) {
+          log.warn(`Could not find a pairing flow for ${channelId}`);
+          return;
+        }
+        flow.onWebChannelMessage(command, data).then(replyData => {
+          this._channel.send(
+            {
+              command,
+              messageId: message.messageId,
+              data: replyData,
+            },
+            sendingContext
+          );
+        });
+        break;
+      default:
+        log.warn("Unrecognized FxAccountsWebChannel command", command);
+        // As a safety measure we also terminate any pending FxA pairing flow.
+        lazy.FxAccountsPairingFlow.finalizeAll();
+        break;
+    }
+  },
+
+  _sendError(error, incomingMessage, sendingContext) {
+    log.error("Failed to handle FxAccountsWebChannel message", error);
+    this._channel.send(
+      {
+        command: incomingMessage.command,
+        messageId: incomingMessage.messageId,
+        data: {
+          error: getErrorDetails(error),
+        },
+      },
+      sendingContext
+    );
+  },
+
+  /**
+   * Create a new channel with the WebChannelBroker, setup a callback listener
+   * @private
+   */
+  _registerChannel() {
+    /**
+     * Processes messages that are called back from the FxAccountsChannel
+     *
+     * @param webChannelId {String}
+     *        Command webChannelId
+     * @param message {Object}
+     *        Command message
+     * @param sendingContext {Object}
+     *        Message sending context.
+     *        @param sendingContext.browsingContext {BrowsingContext}
+     *               The browsingcontext from which the
+     *               WebChannelMessageToChrome was sent.
+     *        @param sendingContext.eventTarget {EventTarget}
+     *               The <EventTarget> where the message was sent.
+     *        @param sendingContext.principal {Principal}
+     *               The <Principal> of the EventTarget where the message was sent.
+     * @private
+     *
+     */
+    let listener = (webChannelId, message, sendingContext) => {
+      if (message) {
+        log.debug("FxAccountsWebChannel message received", message.command);
+        if (logPII) {
+          log.debug("FxAccountsWebChannel message details", message);
+        }
+        try {
+          this._receiveMessage(message, sendingContext);
+        } catch (error) {
+          this._sendError(error, message, sendingContext);
+        }
+      }
+    };
+
+    this._channelCallback = listener;
+    this._channel = new lazy.WebChannel(
+      this._webChannelId,
+      this._webChannelOrigin
+    );
+    this._channel.listen(listener);
+    log.debug(
+      "FxAccountsWebChannel registered: " +
+        this._webChannelId +
+        " with origin " +
+        this._webChannelOrigin.prePath
+    );
+  },
+};
+
+export function FxAccountsWebChannelHelpers(options) {
+  options = options || {};
+
+  this._fxAccounts = options.fxAccounts || lazy.fxAccounts;
+  this._weaveXPCOM = options.weaveXPCOM || null;
+  this._privateBrowsingUtils =
+    options.privateBrowsingUtils || lazy.PrivateBrowsingUtils;
+}
+
+FxAccountsWebChannelHelpers.prototype = {
+  // If the last fxa account used for sync isn't this account, we display
+  // a modal dialog checking they really really want to do this...
+  // (This is sync-specific, so ideally would be in sync's identity module,
+  // but it's a little more seamless to do here, and sync is currently the
+  // only fxa consumer, so...
+  shouldAllowRelink(acctName) {
+    return (
+      !this._needRelinkWarning(acctName) || this._promptForRelink(acctName)
+    );
+  },
+
+  /**
+   * stores sync login info it in the fxaccounts service
+   *
+   * @param accountData the user's account data and credentials
+   */
+  async login(accountData) {
+    // We don't act on customizeSync anymore, it used to open a dialog inside
+    // the browser to selecte the engines to sync but we do it on the web now.
+    log.debug("Webchannel is logging a user in.");
+    delete accountData.customizeSync;
+
+    // Save requested services for later.
+    const requestedServices = accountData.services;
+    delete accountData.services;
+
+    // the user has already been shown the "can link account"
+    // screen. No need to keep this data around.
+    delete accountData.verifiedCanLinkAccount;
+
+    // Remember who it was so we can log out next time.
+    if (accountData.verified) {
+      this.setPreviousAccountNameHashPref(accountData.email);
+    }
+
+    await this._fxAccounts.telemetry.recordConnection(
+      Object.keys(requestedServices || {}),
+      "webchannel"
+    );
+
+    // A sync-specific hack - we want to ensure sync has been initialized
+    // before we set the signed-in user.
+    // XXX - probably not true any more, especially now we have observerPreloads
+    // in FxAccounts.jsm?
+    let xps =
+      this._weaveXPCOM ||
+      Cc["@mozilla.org/weave/service;1"].getService(Ci.nsISupports)
+        .wrappedJSObject;
+    await xps.whenLoaded();
+    await this._fxAccounts._internal.setSignedInUser(accountData);
+
+    if (requestedServices) {
+      // User has enabled Sync.
+      if (requestedServices.sync) {
+        const { offeredEngines, declinedEngines } = requestedServices.sync;
+        if (offeredEngines && declinedEngines) {
+          EXTRA_ENGINES.forEach(engine => {
+            if (
+              offeredEngines.includes(engine) &&
+              !declinedEngines.includes(engine)
+            ) {
+              // These extra engines are disabled by default.
+              Services.prefs.setBoolPref(
+                `services.sync.engine.${engine}`,
+                true
+              );
+            }
+          });
+          log.debug("Received declined engines", declinedEngines);
+          lazy.Weave.Service.engineManager.setDeclined(declinedEngines);
+          declinedEngines.forEach(engine => {
+            Services.prefs.setBoolPref(`services.sync.engine.${engine}`, false);
+          });
+        }
+        log.debug("Webchannel is enabling sync");
+        await xps.Weave.Service.configure();
+      }
+    }
+  },
+
+  /**
+   * logout the fxaccounts service
+   *
+   * @param the uid of the account which have been logged out
+   */
+  async logout(uid) {
+    let fxa = this._fxAccounts;
+    let userData = await fxa._internal.getUserAccountData(["uid"]);
+    if (userData && userData.uid === uid) {
+      await fxa.telemetry.recordDisconnection(null, "webchannel");
+      // true argument is `localOnly`, because server-side stuff
+      // has already been taken care of by the content server
+      await fxa.signOut(true);
+    }
+  },
+
+  /**
+   * Check if `sendingContext` is in private browsing mode.
+   */
+  isPrivateBrowsingMode(sendingContext) {
+    if (!sendingContext) {
+      log.error("Unable to check for private browsing mode, assuming true");
+      return true;
+    }
+
+    let browser = sendingContext.browsingContext.top.embedderElement;
+    const isPrivateBrowsing =
+      this._privateBrowsingUtils.isBrowserPrivate(browser);
+    log.debug("is private browsing", isPrivateBrowsing);
+    return isPrivateBrowsing;
+  },
+
+  /**
+   * Check whether sending fxa_status data should be allowed.
+   */
+  shouldAllowFxaStatus(service, sendingContext, isPairing, context) {
+    // Return user data for any service in non-PB mode. In PB mode,
+    // only return user data if service==="sync" or is in pairing mode
+    // (as service will be equal to the OAuth client ID and not "sync").
+    //
+    // This behaviour allows users to click the "Manage Account"
+    // link from about:preferences#sync while in PB mode and things
+    // "just work". While in non-PB mode, users can sign into
+    // Pocket w/o entering their password a 2nd time, while in PB
+    // mode they *will* have to enter their email/password again.
+    //
+    // The difference in behaviour is to try to match user
+    // expectations as to what is and what isn't part of the browser.
+    // Sync is viewed as an integral part of the browser, interacting
+    // with FxA as part of a Sync flow should work all the time. If
+    // Sync is broken in PB mode, users will think Firefox is broken.
+    // See https://bugzilla.mozilla.org/show_bug.cgi?id=1323853
+    log.debug("service", service);
+    return (
+      !this.isPrivateBrowsingMode(sendingContext) ||
+      service === "sync" ||
+      context === "fx_desktop_v3" ||
+      isPairing
+    );
+  },
+
+  /**
+   * Get fxa_status information. Resolves to { signedInUser: <user_data> }.
+   * If returning status information is not allowed or no user is signed into
+   * Sync, `user_data` will be null.
+   */
+  async getFxaStatus(service, sendingContext, isPairing, context) {
+    let signedInUser = null;
+
+    if (
+      this.shouldAllowFxaStatus(service, sendingContext, isPairing, context)
+    ) {
+      const userData = await this._fxAccounts._internal.getUserAccountData([
+        "email",
+        "sessionToken",
+        "uid",
+        "verified",
+      ]);
+      if (userData) {
+        signedInUser = {
+          email: userData.email,
+          sessionToken: userData.sessionToken,
+          uid: userData.uid,
+          verified: userData.verified,
+        };
+      }
+    }
+
+    return {
+      signedInUser,
+      clientId: FX_OAUTH_CLIENT_ID,
+      capabilities: {
+        multiService: true,
+        pairing: lazy.pairingEnabled,
+        engines: this._getAvailableExtraEngines(),
+      },
+    };
+  },
+
+  _getAvailableExtraEngines() {
+    return EXTRA_ENGINES.filter(engineName => {
+      try {
+        return Services.prefs.getBoolPref(
+          `services.sync.engine.${engineName}.available`
+        );
+      } catch (e) {
+        return false;
+      }
+    });
+  },
+
+  async changePassword(credentials) {
+    // If |credentials| has fields that aren't handled by accounts storage,
+    // updateUserAccountData will throw - mainly to prevent errors in code
+    // that hard-codes field names.
+    // However, in this case the field names aren't really in our control.
+    // We *could* still insist the server know what fields names are valid,
+    // but that makes life difficult for the server when Firefox adds new
+    // features (ie, new fields) - forcing the server to track a map of
+    // versions to supported field names doesn't buy us much.
+    // So we just remove field names we know aren't handled.
+    let newCredentials = {
+      device: null, // Force a brand new device registration.
+      // We force the re-encryption of the send tab keys using the new sync key after the password change
+      encryptedSendTabKeys: null,
+    };
+    for (let name of Object.keys(credentials)) {
+      if (
+        name == "email" ||
+        name == "uid" ||
+        lazy.FxAccountsStorageManagerCanStoreField(name)
+      ) {
+        newCredentials[name] = credentials[name];
+      } else {
+        log.info("changePassword ignoring unsupported field", name);
+      }
+    }
+    await this._fxAccounts._internal.updateUserAccountData(newCredentials);
+    await this._fxAccounts._internal.updateDeviceRegistration();
+  },
+
+  /**
+   * Get the hash of account name of the previously signed in account
+   */
+  getPreviousAccountNameHashPref() {
+    try {
+      return Services.prefs.getStringPref(PREF_LAST_FXA_USER);
+    } catch (_) {
+      return "";
+    }
+  },
+
+  /**
+   * Given an account name, set the hash of the previously signed in account
+   *
+   * @param acctName the account name of the user's account.
+   */
+  setPreviousAccountNameHashPref(acctName) {
+    Services.prefs.setStringPref(
+      PREF_LAST_FXA_USER,
+      lazy.CryptoUtils.sha256Base64(acctName)
+    );
+  },
+
+  /**
+   * Open Sync Preferences in the current tab of the browser
+   *
+   * @param {Object} browser the browser in which to open preferences
+   * @param {String} [entryPoint] entryPoint to use for logging
+   */
+  openSyncPreferences(browser, entryPoint) {
+    let uri = "about:preferences";
+    if (entryPoint) {
+      uri += "?entrypoint=" + encodeURIComponent(entryPoint);
+    }
+    uri += "#sync";
+
+    browser.loadURI(Services.io.newURI(uri), {
+      triggeringPrincipal: Services.scriptSecurityManager.getSystemPrincipal(),
+    });
+  },
+
+  /**
+   * Open Firefox View in the browser's window
+   *
+   * @param {Object} browser the browser in whose window we'll open Firefox View
+   * @param {String} [entryPoint] entryPoint Optional string to use for logging
+   */
+  openFirefoxView(browser, entryPoint) {
+    browser.ownerGlobal.FirefoxViewHandler.openTab(entryPoint);
+  },
+
+  /**
+   * If a user signs in using a different account, the data from the
+   * previous account and the new account will be merged. Ask the user
+   * if they want to continue.
+   *
+   * @private
+   */
+  _needRelinkWarning(acctName) {
+    let prevAcctHash = this.getPreviousAccountNameHashPref();
+    return (
+      prevAcctHash && prevAcctHash != lazy.CryptoUtils.sha256Base64(acctName)
+    );
+  },
+
+  /**
+   * Show the user a warning dialog that the data from the previous account
+   * and the new account will be merged.
+   *
+   * @private
+   */
+  _promptForRelink(acctName) {
+    let sb = Services.strings.createBundle(
+      "chrome://browser/locale/syncSetup.properties"
+    );
+    let continueLabel = sb.GetStringFromName("continue.label");
+    let title = sb.GetStringFromName("relinkVerify.title");
+    let description = sb.formatStringFromName("relinkVerify.description", [
+      acctName,
+    ]);
+    let body =
+      sb.GetStringFromName("relinkVerify.heading") + "\n\n" + description;
+    let ps = Services.prompt;
+    let buttonFlags =
+      ps.BUTTON_POS_0 * ps.BUTTON_TITLE_IS_STRING +
+      ps.BUTTON_POS_1 * ps.BUTTON_TITLE_CANCEL +
+      ps.BUTTON_POS_1_DEFAULT;
+
+    // If running in context of the browser chrome, window does not exist.
+    let pressed = Services.prompt.confirmEx(
+      null,
+      title,
+      body,
+      buttonFlags,
+      continueLabel,
+      null,
+      null,
+      null,
+      {}
+    );
+    return pressed === 0; // 0 is the "continue" button
+  },
+};
+
+var singleton;
+
+// The entry-point for this module, which ensures only one of our channels is
+// ever created - we require this because the WebChannel is global in scope
+// (eg, it uses the observer service to tell interested parties of interesting
+// things) and allowing multiple channels would cause such notifications to be
+// sent multiple times.
+export var EnsureFxAccountsWebChannel = () => {
+  let contentUri = Services.urlFormatter.formatURLPref(
+    "identity.fxaccounts.remote.root"
+  );
+  if (singleton && singleton._contentUri !== contentUri) {
+    singleton.tearDown();
+    singleton = null;
+  }
+  if (!singleton) {
+    try {
+      if (contentUri) {
+        // The FxAccountsWebChannel listens for events and updates
+        // the state machine accordingly.
+        singleton = new FxAccountsWebChannel({
+          content_uri: contentUri,
+          channel_id: WEBCHANNEL_ID,
+        });
+      } else {
+        log.warn("FxA WebChannel functionaly is disabled due to no URI pref.");
+      }
+    } catch (ex) {
+      log.error("Failed to create FxA WebChannel", ex);
+    }
+  }
+};