Add m-esr52 at 52.6.0

1 files changed, 869 insertions, 0 deletions

diff --git a/services/sync/modules/browserid_identity.js b/services/sync/modules/browserid_identity.js
new file mode 100644
index 0000000000..db38215184
--- /dev/null
+++ b/services/sync/modules/browserid_identity.js
@@ -0,0 +1,869 @@
+/* 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/. */
+
+"use strict";
+
+this.EXPORTED_SYMBOLS = ["BrowserIDManager", "AuthenticationError"];
+
+var {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
+
+Cu.import("resource://gre/modules/Log.jsm");
+Cu.import("resource://services-common/async.js");
+Cu.import("resource://services-common/utils.js");
+Cu.import("resource://services-common/tokenserverclient.js");
+Cu.import("resource://services-crypto/utils.js");
+Cu.import("resource://services-sync/identity.js");
+Cu.import("resource://services-sync/util.js");
+Cu.import("resource://services-common/tokenserverclient.js");
+Cu.import("resource://gre/modules/Services.jsm");
+Cu.import("resource://services-sync/constants.js");
+Cu.import("resource://gre/modules/Promise.jsm");
+Cu.import("resource://services-sync/stages/cluster.js");
+Cu.import("resource://gre/modules/FxAccounts.jsm");
+
+// Lazy imports to prevent unnecessary load on startup.
+XPCOMUtils.defineLazyModuleGetter(this, "Weave",
+                                  "resource://services-sync/main.js");
+
+XPCOMUtils.defineLazyModuleGetter(this, "BulkKeyBundle",
+                                  "resource://services-sync/keys.js");
+
+XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
+                                  "resource://gre/modules/FxAccounts.jsm");
+
+XPCOMUtils.defineLazyGetter(this, 'log', function() {
+  let log = Log.repository.getLogger("Sync.BrowserIDManager");
+  log.level = Log.Level[Svc.Prefs.get("log.logger.identity")] || Log.Level.Error;
+  return log;
+});
+
+// FxAccountsCommon.js doesn't use a "namespace", so create one here.
+var fxAccountsCommon = {};
+Cu.import("resource://gre/modules/FxAccountsCommon.js", fxAccountsCommon);
+
+const OBSERVER_TOPICS = [
+  fxAccountsCommon.ONLOGIN_NOTIFICATION,
+  fxAccountsCommon.ONLOGOUT_NOTIFICATION,
+  fxAccountsCommon.ON_ACCOUNT_STATE_CHANGE_NOTIFICATION,
+];
+
+const PREF_SYNC_SHOW_CUSTOMIZATION = "services.sync-setup.ui.showCustomizationDialog";
+
+function deriveKeyBundle(kB) {
+  let out = CryptoUtils.hkdf(kB, undefined,
+                             "identity.mozilla.com/picl/v1/oldsync", 2*32);
+  let bundle = new BulkKeyBundle();
+  // [encryptionKey, hmacKey]
+  bundle.keyPair = [out.slice(0, 32), out.slice(32, 64)];
+  return bundle;
+}
+
+/*
+  General authentication error for abstracting authentication
+  errors from multiple sources (e.g., from FxAccounts, TokenServer).
+  details is additional details about the error - it might be a string, or
+  some other error object (which should do the right thing when toString() is
+  called on it)
+*/
+function AuthenticationError(details, source) {
+  this.details = details;
+  this.source = source;
+}
+
+AuthenticationError.prototype = {
+  toString: function() {
+    return "AuthenticationError(" + this.details + ")";
+  }
+}
+
+this.BrowserIDManager = function BrowserIDManager() {
+  // NOTE: _fxaService and _tokenServerClient are replaced with mocks by
+  // the test suite.
+  this._fxaService = fxAccounts;
+  this._tokenServerClient = new TokenServerClient();
+  this._tokenServerClient.observerPrefix = "weave:service";
+  // will be a promise that resolves when we are ready to authenticate
+  this.whenReadyToAuthenticate = null;
+  this._log = log;
+};
+
+this.BrowserIDManager.prototype = {
+  __proto__: IdentityManager.prototype,
+
+  _fxaService: null,
+  _tokenServerClient: null,
+  // https://docs.services.mozilla.com/token/apis.html
+  _token: null,
+  _signedInUser: null, // the signedinuser we got from FxAccounts.
+
+  // null if no error, otherwise a LOGIN_FAILED_* value that indicates why
+  // we failed to authenticate (but note it might not be an actual
+  // authentication problem, just a transient network error or similar)
+  _authFailureReason: null,
+
+  // it takes some time to fetch a sync key bundle, so until this flag is set,
+  // we don't consider the lack of a keybundle as a failure state.
+  _shouldHaveSyncKeyBundle: false,
+
+  get needsCustomization() {
+    try {
+      return Services.prefs.getBoolPref(PREF_SYNC_SHOW_CUSTOMIZATION);
+    } catch (e) {
+      return false;
+    }
+  },
+
+  hashedUID() {
+    if (!this._token) {
+      throw new Error("hashedUID: Don't have token");
+    }
+    return this._token.hashed_fxa_uid
+  },
+
+  deviceID() {
+    return this._signedInUser && this._signedInUser.deviceId;
+  },
+
+  initialize: function() {
+    for (let topic of OBSERVER_TOPICS) {
+      Services.obs.addObserver(this, topic, false);
+    }
+    // and a background fetch of account data just so we can set this.account,
+    // so we have a username available before we've actually done a login.
+    // XXX - this is actually a hack just for tests and really shouldn't be
+    // necessary. Also, you'd think it would be safe to allow this.account to
+    // be set to null when there's no user logged in, but argue with the test
+    // suite, not with me :)
+    this._fxaService.getSignedInUser().then(accountData => {
+      if (accountData) {
+        this.account = accountData.email;
+      }
+    }).catch(err => {
+      // As above, this is only for tests so it is safe to ignore.
+    });
+  },
+
+  /**
+   * Ensure the user is logged in.  Returns a promise that resolves when
+   * the user is logged in, or is rejected if the login attempt has failed.
+   */
+  ensureLoggedIn: function() {
+    if (!this._shouldHaveSyncKeyBundle && this.whenReadyToAuthenticate) {
+      // We are already in the process of logging in.
+      return this.whenReadyToAuthenticate.promise;
+    }
+
+    // If we are already happy then there is nothing more to do.
+    if (this._syncKeyBundle) {
+      return Promise.resolve();
+    }
+
+    // Similarly, if we have a previous failure that implies an explicit
+    // re-entering of credentials by the user is necessary we don't take any
+    // further action - an observer will fire when the user does that.
+    if (Weave.Status.login == LOGIN_FAILED_LOGIN_REJECTED) {
+      return Promise.reject(new Error("User needs to re-authenticate"));
+    }
+
+    // So - we've a previous auth problem and aren't currently attempting to
+    // log in - so fire that off.
+    this.initializeWithCurrentIdentity();
+    return this.whenReadyToAuthenticate.promise;
+  },
+
+  finalize: function() {
+    // After this is called, we can expect Service.identity != this.
+    for (let topic of OBSERVER_TOPICS) {
+      Services.obs.removeObserver(this, topic);
+    }
+    this.resetCredentials();
+    this._signedInUser = null;
+  },
+
+  offerSyncOptions: function () {
+    // If the user chose to "Customize sync options" when signing
+    // up with Firefox Accounts, ask them to choose what to sync.
+    const url = "chrome://browser/content/sync/customize.xul";
+    const features = "centerscreen,chrome,modal,dialog,resizable=no";
+    let win = Services.wm.getMostRecentWindow("navigator:browser");
+
+    let data = {accepted: false};
+    win.openDialog(url, "_blank", features, data);
+
+    return data;
+  },
+
+  initializeWithCurrentIdentity: function(isInitialSync=false) {
+    // While this function returns a promise that resolves once we've started
+    // the auth process, that process is complete when
+    // this.whenReadyToAuthenticate.promise resolves.
+    this._log.trace("initializeWithCurrentIdentity");
+
+    // Reset the world before we do anything async.
+    this.whenReadyToAuthenticate = Promise.defer();
+    this.whenReadyToAuthenticate.promise.catch(err => {
+      this._log.error("Could not authenticate", err);
+    });
+
+    // initializeWithCurrentIdentity() can be called after the
+    // identity module was first initialized, e.g., after the
+    // user completes a force authentication, so we should make
+    // sure all credentials are reset before proceeding.
+    this.resetCredentials();
+    this._authFailureReason = null;
+
+    return this._fxaService.getSignedInUser().then(accountData => {
+      if (!accountData) {
+        this._log.info("initializeWithCurrentIdentity has no user logged in");
+        this.account = null;
+        // and we are as ready as we can ever be for auth.
+        this._shouldHaveSyncKeyBundle = true;
+        this.whenReadyToAuthenticate.reject("no user is logged in");
+        return;
+      }
+
+      this.account = accountData.email;
+      this._updateSignedInUser(accountData);
+      // The user must be verified before we can do anything at all; we kick
+      // this and the rest of initialization off in the background (ie, we
+      // don't return the promise)
+      this._log.info("Waiting for user to be verified.");
+      this._fxaService.whenVerified(accountData).then(accountData => {
+        this._updateSignedInUser(accountData);
+        this._log.info("Starting fetch for key bundle.");
+        if (this.needsCustomization) {
+          let data = this.offerSyncOptions();
+          if (data.accepted) {
+            Services.prefs.clearUserPref(PREF_SYNC_SHOW_CUSTOMIZATION);
+
+            // Mark any non-selected engines as declined.
+            Weave.Service.engineManager.declineDisabled();
+          } else {
+            // Log out if the user canceled the dialog.
+            return this._fxaService.signOut();
+          }
+        }
+      }).then(() => {
+        return this._fetchTokenForUser();
+      }).then(token => {
+        this._token = token;
+        this._shouldHaveSyncKeyBundle = true; // and we should actually have one...
+        this.whenReadyToAuthenticate.resolve();
+        this._log.info("Background fetch for key bundle done");
+        Weave.Status.login = LOGIN_SUCCEEDED;
+        if (isInitialSync) {
+          this._log.info("Doing initial sync actions");
+          Svc.Prefs.set("firstSync", "resetClient");
+          Services.obs.notifyObservers(null, "weave:service:setup-complete", null);
+          Weave.Utils.nextTick(Weave.Service.sync, Weave.Service);
+        }
+      }).catch(authErr => {
+        // report what failed...
+        this._log.error("Background fetch for key bundle failed", authErr);
+        this._shouldHaveSyncKeyBundle = true; // but we probably don't have one...
+        this.whenReadyToAuthenticate.reject(authErr);
+      });
+      // and we are done - the fetch continues on in the background...
+    }).catch(err => {
+      this._log.error("Processing logged in account", err);
+    });
+  },
+
+  _updateSignedInUser: function(userData) {
+    // This object should only ever be used for a single user.  It is an
+    // error to update the data if the user changes (but updates are still
+    // necessary, as each call may add more attributes to the user).
+    // We start with no user, so an initial update is always ok.
+    if (this._signedInUser && this._signedInUser.email != userData.email) {
+      throw new Error("Attempting to update to a different user.")
+    }
+    this._signedInUser = userData;
+  },
+
+  logout: function() {
+    // This will be called when sync fails (or when the account is being
+    // unlinked etc).  It may have failed because we got a 401 from a sync
+    // server, so we nuke the token.  Next time sync runs and wants an
+    // authentication header, we will notice the lack of the token and fetch a
+    // new one.
+    this._token = null;
+  },
+
+  observe: function (subject, topic, data) {
+    this._log.debug("observed " + topic);
+    switch (topic) {
+    case fxAccountsCommon.ONLOGIN_NOTIFICATION:
+      // This should only happen if we've been initialized without a current
+      // user - otherwise we'd have seen the LOGOUT notification and been
+      // thrown away.
+      // The exception is when we've initialized with a user that needs to
+      // reauth with the server - in that case we will also get here, but
+      // should have the same identity.
+      // initializeWithCurrentIdentity will throw and log if these constraints
+      // aren't met (indirectly, via _updateSignedInUser()), so just go ahead
+      // and do the init.
+      this.initializeWithCurrentIdentity(true);
+      break;
+
+    case fxAccountsCommon.ONLOGOUT_NOTIFICATION:
+      Weave.Service.startOver();
+      // startOver will cause this instance to be thrown away, so there's
+      // nothing else to do.
+      break;
+
+    case fxAccountsCommon.ON_ACCOUNT_STATE_CHANGE_NOTIFICATION:
+      // throw away token and fetch a new one
+      this.resetCredentials();
+      this._ensureValidToken().catch(err =>
+        this._log.error("Error while fetching a new token", err));
+      break;
+    }
+  },
+
+  /**
+   * Compute the sha256 of the message bytes.  Return bytes.
+   */
+  _sha256: function(message) {
+    let hasher = Cc["@mozilla.org/security/hash;1"]
+                    .createInstance(Ci.nsICryptoHash);
+    hasher.init(hasher.SHA256);
+    return CryptoUtils.digestBytes(message, hasher);
+  },
+
+  /**
+   * Compute the X-Client-State header given the byte string kB.
+   *
+   * Return string: hex(first16Bytes(sha256(kBbytes)))
+   */
+  _computeXClientState: function(kBbytes) {
+    return CommonUtils.bytesAsHex(this._sha256(kBbytes).slice(0, 16), false);
+  },
+
+  /**
+   * Provide override point for testing token expiration.
+   */
+  _now: function() {
+    return this._fxaService.now()
+  },
+
+  get _localtimeOffsetMsec() {
+    return this._fxaService.localtimeOffsetMsec;
+  },
+
+  usernameFromAccount: function(val) {
+    // we don't differentiate between "username" and "account"
+    return val;
+  },
+
+  /**
+   * Obtains the HTTP Basic auth password.
+   *
+   * Returns a string if set or null if it is not set.
+   */
+  get basicPassword() {
+    this._log.error("basicPassword getter should be not used in BrowserIDManager");
+    return null;
+  },
+
+  /**
+   * Set the HTTP basic password to use.
+   *
+   * Changes will not persist unless persistSyncCredentials() is called.
+   */
+  set basicPassword(value) {
+    throw "basicPassword setter should be not used in BrowserIDManager";
+  },
+
+  /**
+   * Obtain the Sync Key.
+   *
+   * This returns a 26 character "friendly" Base32 encoded string on success or
+   * null if no Sync Key could be found.
+   *
+   * If the Sync Key hasn't been set in this session, this will look in the
+   * password manager for the sync key.
+   */
+  get syncKey() {
+    if (this.syncKeyBundle) {
+      // TODO: This is probably fine because the code shouldn't be
+      // using the sync key directly (it should use the sync key
+      // bundle), but I don't like it. We should probably refactor
+      // code that is inspecting this to not do validation on this
+      // field directly and instead call a isSyncKeyValid() function
+      // that we can override.
+      return "99999999999999999999999999";
+    }
+    else {
+      return null;
+    }
+  },
+
+  set syncKey(value) {
+    throw "syncKey setter should be not used in BrowserIDManager";
+  },
+
+  get syncKeyBundle() {
+    return this._syncKeyBundle;
+  },
+
+  /**
+   * Resets/Drops all credentials we hold for the current user.
+   */
+  resetCredentials: function() {
+    this.resetSyncKey();
+    this._token = null;
+    // The cluster URL comes from the token, so resetting it to empty will
+    // force Sync to not accidentally use a value from an earlier token.
+    Weave.Service.clusterURL = null;
+  },
+
+  /**
+   * Resets/Drops the sync key we hold for the current user.
+   */
+  resetSyncKey: function() {
+    this._syncKey = null;
+    this._syncKeyBundle = null;
+    this._syncKeyUpdated = true;
+    this._shouldHaveSyncKeyBundle = false;
+  },
+
+  /**
+   * Pre-fetches any information that might help with migration away from this
+   * identity.  Called after every sync and is really just an optimization that
+   * allows us to avoid a network request for when we actually need the
+   * migration info.
+   */
+  prefetchMigrationSentinel: function(service) {
+    // nothing to do here until we decide to migrate away from FxA.
+  },
+
+  /**
+    * Return credentials hosts for this identity only.
+    */
+  _getSyncCredentialsHosts: function() {
+    return Utils.getSyncCredentialsHostsFxA();
+  },
+
+  /**
+   * The current state of the auth credentials.
+   *
+   * This essentially validates that enough credentials are available to use
+   * Sync. It doesn't check we have all the keys we need as the master-password
+   * may have been locked when we tried to get them - we rely on
+   * unlockAndVerifyAuthState to check that for us.
+   */
+  get currentAuthState() {
+    if (this._authFailureReason) {
+      this._log.info("currentAuthState returning " + this._authFailureReason +
+                     " due to previous failure");
+      return this._authFailureReason;
+    }
+    // TODO: need to revisit this. Currently this isn't ready to go until
+    // both the username and syncKeyBundle are both configured and having no
+    // username seems to make things fail fast so that's good.
+    if (!this.username) {
+      return LOGIN_FAILED_NO_USERNAME;
+    }
+
+    return STATUS_OK;
+  },
+
+  // Do we currently have keys, or do we have enough that we should be able
+  // to successfully fetch them?
+  _canFetchKeys: function() {
+    let userData = this._signedInUser;
+    // a keyFetchToken means we can almost certainly grab them.
+    // kA and kB means we already have them.
+    return userData && (userData.keyFetchToken || (userData.kA && userData.kB));
+  },
+
+  /**
+   * Verify the current auth state, unlocking the master-password if necessary.
+   *
+   * Returns a promise that resolves with the current auth state after
+   * attempting to unlock.
+   */
+  unlockAndVerifyAuthState: function() {
+    if (this._canFetchKeys()) {
+      log.debug("unlockAndVerifyAuthState already has (or can fetch) sync keys");
+      return Promise.resolve(STATUS_OK);
+    }
+    // so no keys - ensure MP unlocked.
+    if (!Utils.ensureMPUnlocked()) {
+      // user declined to unlock, so we don't know if they are stored there.
+      log.debug("unlockAndVerifyAuthState: user declined to unlock master-password");
+      return Promise.resolve(MASTER_PASSWORD_LOCKED);
+    }
+    // now we are unlocked we must re-fetch the user data as we may now have
+    // the details that were previously locked away.
+    return this._fxaService.getSignedInUser().then(
+      accountData => {
+        this._updateSignedInUser(accountData);
+        // If we still can't get keys it probably means the user authenticated
+        // without unlocking the MP or cleared the saved logins, so we've now
+        // lost them - the user will need to reauth before continuing.
+        let result;
+        if (this._canFetchKeys()) {
+          result = STATUS_OK;
+        } else {
+          result = LOGIN_FAILED_LOGIN_REJECTED;
+        }
+        log.debug("unlockAndVerifyAuthState re-fetched credentials and is returning", result);
+        return result;
+      }
+    );
+  },
+
+  /**
+   * Do we have a non-null, not yet expired token for the user currently
+   * signed in?
+   */
+  hasValidToken: function() {
+    // If pref is set to ignore cached authentication credentials for debugging,
+    // then return false to force the fetching of a new token.
+    let ignoreCachedAuthCredentials = false;
+    try {
+      ignoreCachedAuthCredentials = Svc.Prefs.get("debug.ignoreCachedAuthCredentials");
+    } catch(e) {
+      // Pref doesn't exist
+    }
+    if (ignoreCachedAuthCredentials) {
+      return false;
+    }
+    if (!this._token) {
+      return false;
+    }
+    if (this._token.expiration < this._now()) {
+      return false;
+    }
+    return true;
+  },
+
+  // Get our tokenServerURL - a private helper. Returns a string.
+  get _tokenServerUrl() {
+    // We used to support services.sync.tokenServerURI but this was a
+    // pain-point for people using non-default servers as Sync may auto-reset
+    // all services.sync prefs. So if that still exists, it wins.
+    let url = Svc.Prefs.get("tokenServerURI"); // Svc.Prefs "root" is services.sync
+    if (!url) {
+      url = Services.prefs.getCharPref("identity.sync.tokenserver.uri");
+    }
+    while (url.endsWith("/")) { // trailing slashes cause problems...
+      url = url.slice(0, -1);
+    }
+    return url;
+  },
+
+  // Refresh the sync token for our user. Returns a promise that resolves
+  // with a token (which may be null in one sad edge-case), or rejects with an
+  // error.
+  _fetchTokenForUser: function() {
+    // tokenServerURI is mis-named - convention is uri means nsISomething...
+    let tokenServerURI = this._tokenServerUrl;
+    let log = this._log;
+    let client = this._tokenServerClient;
+    let fxa = this._fxaService;
+    let userData = this._signedInUser;
+
+    // We need kA and kB for things to work.  If we don't have them, just
+    // return null for the token - sync calling unlockAndVerifyAuthState()
+    // before actually syncing will setup the error states if necessary.
+    if (!this._canFetchKeys()) {
+      log.info("Unable to fetch keys (master-password locked?), so aborting token fetch");
+      return Promise.resolve(null);
+    }
+
+    let maybeFetchKeys = () => {
+      // This is called at login time and every time we need a new token - in
+      // the latter case we already have kA and kB, so optimise that case.
+      if (userData.kA && userData.kB) {
+        return;
+      }
+      log.info("Fetching new keys");
+      return this._fxaService.getKeys().then(
+        newUserData => {
+          userData = newUserData;
+          this._updateSignedInUser(userData); // throws if the user changed.
+        }
+      );
+    }
+
+    let getToken = assertion => {
+      log.debug("Getting a token");
+      let deferred = Promise.defer();
+      let cb = function (err, token) {
+        if (err) {
+          return deferred.reject(err);
+        }
+        log.debug("Successfully got a sync token");
+        return deferred.resolve(token);
+      };
+
+      let kBbytes = CommonUtils.hexToBytes(userData.kB);
+      let headers = {"X-Client-State": this._computeXClientState(kBbytes)};
+      client.getTokenFromBrowserIDAssertion(tokenServerURI, assertion, cb, headers);
+      return deferred.promise;
+    }
+
+    let getAssertion = () => {
+      log.info("Getting an assertion from", tokenServerURI);
+      let audience = Services.io.newURI(tokenServerURI, null, null).prePath;
+      return fxa.getAssertion(audience);
+    };
+
+    // wait until the account email is verified and we know that
+    // getAssertion() will return a real assertion (not null).
+    return fxa.whenVerified(this._signedInUser)
+      .then(() => maybeFetchKeys())
+      .then(() => getAssertion())
+      .then(assertion => getToken(assertion))
+      .catch(err => {
+        // If we get a 401 fetching the token it may be that our certificate
+        // needs to be regenerated.
+        if (!err.response || err.response.status !== 401) {
+          return Promise.reject(err);
+        }
+        log.warn("Token server returned 401, refreshing certificate and retrying token fetch");
+        return fxa.invalidateCertificate()
+          .then(() => getAssertion())
+          .then(assertion => getToken(assertion))
+      })
+      .then(token => {
+        // TODO: Make it be only 80% of the duration, so refresh the token
+        // before it actually expires. This is to avoid sync storage errors
+        // otherwise, we get a nasty notification bar briefly. Bug 966568.
+        token.expiration = this._now() + (token.duration * 1000) * 0.80;
+        if (!this._syncKeyBundle) {
+          // We are given kA/kB as hex.
+          this._syncKeyBundle = deriveKeyBundle(Utils.hexToBytes(userData.kB));
+        }
+        return token;
+      })
+      .catch(err => {
+        // TODO: unify these errors - we need to handle errors thrown by
+        // both tokenserverclient and hawkclient.
+        // A tokenserver error thrown based on a bad response.
+        if (err.response && err.response.status === 401) {
+          err = new AuthenticationError(err, "tokenserver");
+        // A hawkclient error.
+        } else if (err.code && err.code === 401) {
+          err = new AuthenticationError(err, "hawkclient");
+        // An FxAccounts.jsm error.
+        } else if (err.message == fxAccountsCommon.ERROR_AUTH_ERROR) {
+          err = new AuthenticationError(err, "fxaccounts");
+        }
+
+        // TODO: write tests to make sure that different auth error cases are handled here
+        // properly: auth error getting assertion, auth error getting token (invalid generation
+        // and client-state error)
+        if (err instanceof AuthenticationError) {
+          this._log.error("Authentication error in _fetchTokenForUser", err);
+          // set it to the "fatal" LOGIN_FAILED_LOGIN_REJECTED reason.
+          this._authFailureReason = LOGIN_FAILED_LOGIN_REJECTED;
+        } else {
+          this._log.error("Non-authentication error in _fetchTokenForUser", err);
+          // for now assume it is just a transient network related problem
+          // (although sadly, it might also be a regular unhandled exception)
+          this._authFailureReason = LOGIN_FAILED_NETWORK_ERROR;
+        }
+        // this._authFailureReason being set to be non-null in the above if clause
+        // ensures we are in the correct currentAuthState, and
+        // this._shouldHaveSyncKeyBundle being true ensures everything that cares knows
+        // that there is no authentication dance still under way.
+        this._shouldHaveSyncKeyBundle = true;
+        Weave.Status.login = this._authFailureReason;
+        throw err;
+      });
+  },
+
+  // Returns a promise that is resolved when we have a valid token for the
+  // current user stored in this._token.  When resolved, this._token is valid.
+  _ensureValidToken: function() {
+    if (this.hasValidToken()) {
+      this._log.debug("_ensureValidToken already has one");
+      return Promise.resolve();
+    }
+    const notifyStateChanged =
+      () => Services.obs.notifyObservers(null, "weave:service:login:change", null);
+    // reset this._token as a safety net to reduce the possibility of us
+    // repeatedly attempting to use an invalid token if _fetchTokenForUser throws.
+    this._token = null;
+    return this._fetchTokenForUser().then(
+      token => {
+        this._token = token;
+        notifyStateChanged();
+      },
+      error => {
+        notifyStateChanged();
+        throw error
+      }
+    );
+  },
+
+  getResourceAuthenticator: function () {
+    return this._getAuthenticationHeader.bind(this);
+  },
+
+  /**
+   * Obtain a function to be used for adding auth to RESTRequest instances.
+   */
+  getRESTRequestAuthenticator: function() {
+    return this._addAuthenticationHeader.bind(this);
+  },
+
+  /**
+   * @return a Hawk HTTP Authorization Header, lightly wrapped, for the .uri
+   * of a RESTRequest or AsyncResponse object.
+   */
+  _getAuthenticationHeader: function(httpObject, method) {
+    let cb = Async.makeSpinningCallback();
+    this._ensureValidToken().then(cb, cb);
+    // Note that in failure states we return null, causing the request to be
+    // made without authorization headers, thereby presumably causing a 401,
+    // which causes Sync to log out. If we throw, this may not happen as
+    // expected.
+    try {
+      cb.wait();
+    } catch (ex) {
+      if (Async.isShutdownException(ex)) {
+        throw ex;
+      }
+      this._log.error("Failed to fetch a token for authentication", ex);
+      return null;
+    }
+    if (!this._token) {
+      return null;
+    }
+    let credentials = {algorithm: "sha256",
+                       id: this._token.id,
+                       key: this._token.key,
+                      };
+    method = method || httpObject.method;
+
+    // Get the local clock offset from the Firefox Accounts server.  This should
+    // be close to the offset from the storage server.
+    let options = {
+      now: this._now(),
+      localtimeOffsetMsec: this._localtimeOffsetMsec,
+      credentials: credentials,
+    };
+
+    let headerValue = CryptoUtils.computeHAWK(httpObject.uri, method, options);
+    return {headers: {authorization: headerValue.field}};
+  },
+
+  _addAuthenticationHeader: function(request, method) {
+    let header = this._getAuthenticationHeader(request, method);
+    if (!header) {
+      return null;
+    }
+    request.setHeader("authorization", header.headers.authorization);
+    return request;
+  },
+
+  createClusterManager: function(service) {
+    return new BrowserIDClusterManager(service);
+  },
+
+  // Tell Sync what the login status should be if it saw a 401 fetching
+  // info/collections as part of login verification (typically immediately
+  // after login.)
+  // In our case, it almost certainly means a transient error fetching a token
+  // (and hitting this will cause us to logout, which will correctly handle an
+  // authoritative login issue.)
+  loginStatusFromVerification404() {
+    return LOGIN_FAILED_NETWORK_ERROR;
+  },
+};
+
+/* An implementation of the ClusterManager for this identity
+ */
+
+function BrowserIDClusterManager(service) {
+  ClusterManager.call(this, service);
+}
+
+BrowserIDClusterManager.prototype = {
+  __proto__: ClusterManager.prototype,
+
+  _findCluster: function() {
+    let endPointFromIdentityToken = function() {
+      // The only reason (in theory ;) that we can end up with a null token
+      // is when this.identity._canFetchKeys() returned false.  In turn, this
+      // should only happen if the master-password is locked or the credentials
+      // storage is screwed, and in those cases we shouldn't have started
+      // syncing so shouldn't get here anyway.
+      // But better safe than sorry! To keep things clearer, throw an explicit
+      // exception - the message will appear in the logs and the error will be
+      // treated as transient.
+      if (!this.identity._token) {
+        throw new Error("Can't get a cluster URL as we can't fetch keys.");
+      }
+      let endpoint = this.identity._token.endpoint;
+      // For Sync 1.5 storage endpoints, we use the base endpoint verbatim.
+      // However, it should end in "/" because we will extend it with
+      // well known path components. So we add a "/" if it's missing.
+      if (!endpoint.endsWith("/")) {
+        endpoint += "/";
+      }
+      log.debug("_findCluster returning " + endpoint);
+      return endpoint;
+    }.bind(this);
+
+    // Spinningly ensure we are ready to authenticate and have a valid token.
+    let promiseClusterURL = function() {
+      return this.identity.whenReadyToAuthenticate.promise.then(
+        () => {
+          // We need to handle node reassignment here.  If we are being asked
+          // for a clusterURL while the service already has a clusterURL, then
+          // it's likely a 401 was received using the existing token - in which
+          // case we just discard the existing token and fetch a new one.
+          if (this.service.clusterURL) {
+            log.debug("_findCluster has a pre-existing clusterURL, so discarding the current token");
+            this.identity._token = null;
+          }
+          return this.identity._ensureValidToken();
+        }
+      ).then(endPointFromIdentityToken
+      );
+    }.bind(this);
+
+    let cb = Async.makeSpinningCallback();
+    promiseClusterURL().then(function (clusterURL) {
+      cb(null, clusterURL);
+    }).then(
+      null, err => {
+      log.info("Failed to fetch the cluster URL", err);
+      // service.js's verifyLogin() method will attempt to fetch a cluster
+      // URL when it sees a 401.  If it gets null, it treats it as a "real"
+      // auth error and sets Status.login to LOGIN_FAILED_LOGIN_REJECTED, which
+      // in turn causes a notification bar to appear informing the user they
+      // need to re-authenticate.
+      // On the other hand, if fetching the cluster URL fails with an exception,
+      // verifyLogin() assumes it is a transient error, and thus doesn't show
+      // the notification bar under the assumption the issue will resolve
+      // itself.
+      // Thus:
+      // * On a real 401, we must return null.
+      // * On any other problem we must let an exception bubble up.
+      if (err instanceof AuthenticationError) {
+        // callback with no error and a null result - cb.wait() returns null.
+        cb(null, null);
+      } else {
+        // callback with an error - cb.wait() completes by raising an exception.
+        cb(err);
+      }
+    });
+    return cb.wait();
+  },
+
+  getUserBaseURL: function() {
+    // Legacy Sync and FxA Sync construct the userBaseURL differently. Legacy
+    // Sync appends path components onto an empty path, and in FxA Sync the
+    // token server constructs this for us in an opaque manner. Since the
+    // cluster manager already sets the clusterURL on Service and also has
+    // access to the current identity, we added this functionality here.
+    return this.service.clusterURL;
+  }
+}