michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: this.EXPORTED_SYMBOLS = ["BrowserIDManager"];
michael@0: 
michael@0: const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
michael@0: 
michael@0: Cu.import("resource://gre/modules/Log.jsm");
michael@0: Cu.import("resource://services-common/async.js");
michael@0: Cu.import("resource://services-common/utils.js");
michael@0: Cu.import("resource://services-common/tokenserverclient.js");
michael@0: Cu.import("resource://services-crypto/utils.js");
michael@0: Cu.import("resource://services-sync/identity.js");
michael@0: Cu.import("resource://services-sync/util.js");
michael@0: Cu.import("resource://services-common/tokenserverclient.js");
michael@0: Cu.import("resource://gre/modules/Services.jsm");
michael@0: Cu.import("resource://services-sync/constants.js");
michael@0: Cu.import("resource://gre/modules/Promise.jsm");
michael@0: Cu.import("resource://services-sync/stages/cluster.js");
michael@0: Cu.import("resource://gre/modules/FxAccounts.jsm");
michael@0: 
michael@0: // Lazy imports to prevent unnecessary load on startup.
michael@0: XPCOMUtils.defineLazyModuleGetter(this, "Weave",
michael@0:                                   "resource://services-sync/main.js");
michael@0: 
michael@0: XPCOMUtils.defineLazyModuleGetter(this, "BulkKeyBundle",
michael@0:                                   "resource://services-sync/keys.js");
michael@0: 
michael@0: XPCOMUtils.defineLazyModuleGetter(this, "fxAccounts",
michael@0:                                   "resource://gre/modules/FxAccounts.jsm");
michael@0: 
michael@0: XPCOMUtils.defineLazyGetter(this, 'log', function() {
michael@0:   let log = Log.repository.getLogger("Sync.BrowserIDManager");
michael@0:   log.level = Log.Level[Svc.Prefs.get("log.logger.identity")] || Log.Level.Error;
michael@0:   return log;
michael@0: });
michael@0: 
michael@0: // FxAccountsCommon.js doesn't use a "namespace", so create one here.
michael@0: let fxAccountsCommon = {};
michael@0: Cu.import("resource://gre/modules/FxAccountsCommon.js", fxAccountsCommon);
michael@0: 
michael@0: const OBSERVER_TOPICS = [
michael@0:   fxAccountsCommon.ONLOGIN_NOTIFICATION,
michael@0:   fxAccountsCommon.ONLOGOUT_NOTIFICATION,
michael@0: ];
michael@0: 
michael@0: const PREF_SYNC_SHOW_CUSTOMIZATION = "services.sync.ui.showCustomizationDialog";
michael@0: 
michael@0: function deriveKeyBundle(kB) {
michael@0:   let out = CryptoUtils.hkdf(kB, undefined,
michael@0:                              "identity.mozilla.com/picl/v1/oldsync", 2*32);
michael@0:   let bundle = new BulkKeyBundle();
michael@0:   // [encryptionKey, hmacKey]
michael@0:   bundle.keyPair = [out.slice(0, 32), out.slice(32, 64)];
michael@0:   return bundle;
michael@0: }
michael@0: 
michael@0: /*
michael@0:   General authentication error for abstracting authentication
michael@0:   errors from multiple sources (e.g., from FxAccounts, TokenServer).
michael@0:   details is additional details about the error - it might be a string, or
michael@0:   some other error object (which should do the right thing when toString() is
michael@0:   called on it)
michael@0: */
michael@0: function AuthenticationError(details) {
michael@0:   this.details = details;
michael@0: }
michael@0: 
michael@0: AuthenticationError.prototype = {
michael@0:   toString: function() {
michael@0:     return "AuthenticationError(" + this.details + ")";
michael@0:   }
michael@0: }
michael@0: 
michael@0: this.BrowserIDManager = function BrowserIDManager() {
michael@0:   // NOTE: _fxaService and _tokenServerClient are replaced with mocks by
michael@0:   // the test suite.
michael@0:   this._fxaService = fxAccounts;
michael@0:   this._tokenServerClient = new TokenServerClient();
michael@0:   this._tokenServerClient.observerPrefix = "weave:service";
michael@0:   // will be a promise that resolves when we are ready to authenticate
michael@0:   this.whenReadyToAuthenticate = null;
michael@0:   this._log = log;
michael@0: };
michael@0: 
michael@0: this.BrowserIDManager.prototype = {
michael@0:   __proto__: IdentityManager.prototype,
michael@0: 
michael@0:   _fxaService: null,
michael@0:   _tokenServerClient: null,
michael@0:   // https://docs.services.mozilla.com/token/apis.html
michael@0:   _token: null,
michael@0:   _signedInUser: null, // the signedinuser we got from FxAccounts.
michael@0: 
michael@0:   // null if no error, otherwise a LOGIN_FAILED_* value that indicates why
michael@0:   // we failed to authenticate (but note it might not be an actual
michael@0:   // authentication problem, just a transient network error or similar)
michael@0:   _authFailureReason: null,
michael@0: 
michael@0:   // it takes some time to fetch a sync key bundle, so until this flag is set,
michael@0:   // we don't consider the lack of a keybundle as a failure state.
michael@0:   _shouldHaveSyncKeyBundle: false,
michael@0: 
michael@0:   get readyToAuthenticate() {
michael@0:     // We are finished initializing when we *should* have a sync key bundle,
michael@0:     // although we might not actually have one due to auth failures etc.
michael@0:     return this._shouldHaveSyncKeyBundle;
michael@0:   },
michael@0: 
michael@0:   get needsCustomization() {
michael@0:     try {
michael@0:       return Services.prefs.getBoolPref(PREF_SYNC_SHOW_CUSTOMIZATION);
michael@0:     } catch (e) {
michael@0:       return false;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   initialize: function() {
michael@0:     for (let topic of OBSERVER_TOPICS) {
michael@0:       Services.obs.addObserver(this, topic, false);
michael@0:     }
michael@0:     return this.initializeWithCurrentIdentity();
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Ensure the user is logged in.  Returns a promise that resolves when
michael@0:    * the user is logged in, or is rejected if the login attempt has failed.
michael@0:    */
michael@0:   ensureLoggedIn: function() {
michael@0:     if (!this._shouldHaveSyncKeyBundle) {
michael@0:       // We are already in the process of logging in.
michael@0:       return this.whenReadyToAuthenticate.promise;
michael@0:     }
michael@0: 
michael@0:     // If we are already happy then there is nothing more to do.
michael@0:     if (this._syncKeyBundle) {
michael@0:       return Promise.resolve();
michael@0:     }
michael@0: 
michael@0:     // Similarly, if we have a previous failure that implies an explicit
michael@0:     // re-entering of credentials by the user is necessary we don't take any
michael@0:     // further action - an observer will fire when the user does that.
michael@0:     if (Weave.Status.login == LOGIN_FAILED_LOGIN_REJECTED) {
michael@0:       return Promise.reject();
michael@0:     }
michael@0: 
michael@0:     // So - we've a previous auth problem and aren't currently attempting to
michael@0:     // log in - so fire that off.
michael@0:     this.initializeWithCurrentIdentity();
michael@0:     return this.whenReadyToAuthenticate.promise;
michael@0:   },
michael@0: 
michael@0:   finalize: function() {
michael@0:     // After this is called, we can expect Service.identity != this.
michael@0:     for (let topic of OBSERVER_TOPICS) {
michael@0:       Services.obs.removeObserver(this, topic);
michael@0:     }
michael@0:     this.resetCredentials();
michael@0:     this._signedInUser = null;
michael@0:     return Promise.resolve();
michael@0:   },
michael@0: 
michael@0:   offerSyncOptions: function () {
michael@0:     // If the user chose to "Customize sync options" when signing
michael@0:     // up with Firefox Accounts, ask them to choose what to sync.
michael@0:     const url = "chrome://browser/content/sync/customize.xul";
michael@0:     const features = "centerscreen,chrome,modal,dialog,resizable=no";
michael@0:     let win = Services.wm.getMostRecentWindow("navigator:browser");
michael@0: 
michael@0:     let data = {accepted: false};
michael@0:     win.openDialog(url, "_blank", features, data);
michael@0: 
michael@0:     return data;
michael@0:   },
michael@0: 
michael@0:   initializeWithCurrentIdentity: function(isInitialSync=false) {
michael@0:     // While this function returns a promise that resolves once we've started
michael@0:     // the auth process, that process is complete when
michael@0:     // this.whenReadyToAuthenticate.promise resolves.
michael@0:     this._log.trace("initializeWithCurrentIdentity");
michael@0: 
michael@0:     // Reset the world before we do anything async.
michael@0:     this.whenReadyToAuthenticate = Promise.defer();
michael@0:     this.whenReadyToAuthenticate.promise.then(null, (err) => {
michael@0:       this._log.error("Could not authenticate: " + err);
michael@0:     });
michael@0: 
michael@0:     this._shouldHaveSyncKeyBundle = false;
michael@0:     this._authFailureReason = null;
michael@0: 
michael@0:     return this._fxaService.getSignedInUser().then(accountData => {
michael@0:       if (!accountData) {
michael@0:         this._log.info("initializeWithCurrentIdentity has no user logged in");
michael@0:         this.account = null;
michael@0:         // and we are as ready as we can ever be for auth.
michael@0:         this._shouldHaveSyncKeyBundle = true;
michael@0:         this.whenReadyToAuthenticate.reject("no user is logged in");
michael@0:         return;
michael@0:       }
michael@0: 
michael@0:       this.account = accountData.email;
michael@0:       this._updateSignedInUser(accountData);
michael@0:       // The user must be verified before we can do anything at all; we kick
michael@0:       // this and the rest of initialization off in the background (ie, we
michael@0:       // don't return the promise)
michael@0:       this._log.info("Waiting for user to be verified.");
michael@0:       this._fxaService.whenVerified(accountData).then(accountData => {
michael@0:         this._updateSignedInUser(accountData);
michael@0:         this._log.info("Starting fetch for key bundle.");
michael@0:         if (this.needsCustomization) {
michael@0:           let data = this.offerSyncOptions();
michael@0:           if (data.accepted) {
michael@0:             Services.prefs.clearUserPref(PREF_SYNC_SHOW_CUSTOMIZATION);
michael@0: 
michael@0:             // Mark any non-selected engines as declined.
michael@0:             Weave.Service.engineManager.declineDisabled();
michael@0:           } else {
michael@0:             // Log out if the user canceled the dialog.
michael@0:             return this._fxaService.signOut();
michael@0:           }
michael@0:         }
michael@0:       }).then(() => {
michael@0:         return this._fetchTokenForUser();
michael@0:       }).then(token => {
michael@0:         this._token = token;
michael@0:         this._shouldHaveSyncKeyBundle = true; // and we should actually have one...
michael@0:         this.whenReadyToAuthenticate.resolve();
michael@0:         this._log.info("Background fetch for key bundle done");
michael@0:         Weave.Status.login = LOGIN_SUCCEEDED;
michael@0:         if (isInitialSync) {
michael@0:           this._log.info("Doing initial sync actions");
michael@0:           Svc.Prefs.set("firstSync", "resetClient");
michael@0:           Services.obs.notifyObservers(null, "weave:service:setup-complete", null);
michael@0:           Weave.Utils.nextTick(Weave.Service.sync, Weave.Service);
michael@0:         }
michael@0:       }).then(null, err => {
michael@0:         this._shouldHaveSyncKeyBundle = true; // but we probably don't have one...
michael@0:         this.whenReadyToAuthenticate.reject(err);
michael@0:         // report what failed...
michael@0:         this._log.error("Background fetch for key bundle failed: " + err);
michael@0:       });
michael@0:       // and we are done - the fetch continues on in the background...
michael@0:     }).then(null, err => {
michael@0:       this._log.error("Processing logged in account: " + err);
michael@0:     });
michael@0:   },
michael@0: 
michael@0:   _updateSignedInUser: function(userData) {
michael@0:     // This object should only ever be used for a single user.  It is an
michael@0:     // error to update the data if the user changes (but updates are still
michael@0:     // necessary, as each call may add more attributes to the user).
michael@0:     // We start with no user, so an initial update is always ok.
michael@0:     if (this._signedInUser && this._signedInUser.email != userData.email) {
michael@0:       throw new Error("Attempting to update to a different user.")
michael@0:     }
michael@0:     this._signedInUser = userData;
michael@0:   },
michael@0: 
michael@0:   logout: function() {
michael@0:     // This will be called when sync fails (or when the account is being
michael@0:     // unlinked etc).  It may have failed because we got a 401 from a sync
michael@0:     // server, so we nuke the token.  Next time sync runs and wants an
michael@0:     // authentication header, we will notice the lack of the token and fetch a
michael@0:     // new one.
michael@0:     this._token = null;
michael@0:   },
michael@0: 
michael@0:   observe: function (subject, topic, data) {
michael@0:     this._log.debug("observed " + topic);
michael@0:     switch (topic) {
michael@0:     case fxAccountsCommon.ONLOGIN_NOTIFICATION:
michael@0:       // This should only happen if we've been initialized without a current
michael@0:       // user - otherwise we'd have seen the LOGOUT notification and been
michael@0:       // thrown away.
michael@0:       // The exception is when we've initialized with a user that needs to
michael@0:       // reauth with the server - in that case we will also get here, but
michael@0:       // should have the same identity.
michael@0:       // initializeWithCurrentIdentity will throw and log if these contraints
michael@0:       // aren't met, so just go ahead and do the init.
michael@0:       this.initializeWithCurrentIdentity(true);
michael@0:       break;
michael@0: 
michael@0:     case fxAccountsCommon.ONLOGOUT_NOTIFICATION:
michael@0:       Weave.Service.startOver();
michael@0:       // startOver will cause this instance to be thrown away, so there's
michael@0:       // nothing else to do.
michael@0:       break;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Compute the sha256 of the message bytes.  Return bytes.
michael@0:    */
michael@0:   _sha256: function(message) {
michael@0:     let hasher = Cc["@mozilla.org/security/hash;1"]
michael@0:                     .createInstance(Ci.nsICryptoHash);
michael@0:     hasher.init(hasher.SHA256);
michael@0:     return CryptoUtils.digestBytes(message, hasher);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Compute the X-Client-State header given the byte string kB.
michael@0:    *
michael@0:    * Return string: hex(first16Bytes(sha256(kBbytes)))
michael@0:    */
michael@0:   _computeXClientState: function(kBbytes) {
michael@0:     return CommonUtils.bytesAsHex(this._sha256(kBbytes).slice(0, 16), false);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Provide override point for testing token expiration.
michael@0:    */
michael@0:   _now: function() {
michael@0:     return this._fxaService.now()
michael@0:   },
michael@0: 
michael@0:   get _localtimeOffsetMsec() {
michael@0:     return this._fxaService.localtimeOffsetMsec;
michael@0:   },
michael@0: 
michael@0:   usernameFromAccount: function(val) {
michael@0:     // we don't differentiate between "username" and "account"
michael@0:     return val;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Obtains the HTTP Basic auth password.
michael@0:    *
michael@0:    * Returns a string if set or null if it is not set.
michael@0:    */
michael@0:   get basicPassword() {
michael@0:     this._log.error("basicPassword getter should be not used in BrowserIDManager");
michael@0:     return null;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Set the HTTP basic password to use.
michael@0:    *
michael@0:    * Changes will not persist unless persistSyncCredentials() is called.
michael@0:    */
michael@0:   set basicPassword(value) {
michael@0:     throw "basicPassword setter should be not used in BrowserIDManager";
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Obtain the Sync Key.
michael@0:    *
michael@0:    * This returns a 26 character "friendly" Base32 encoded string on success or
michael@0:    * null if no Sync Key could be found.
michael@0:    *
michael@0:    * If the Sync Key hasn't been set in this session, this will look in the
michael@0:    * password manager for the sync key.
michael@0:    */
michael@0:   get syncKey() {
michael@0:     if (this.syncKeyBundle) {
michael@0:       // TODO: This is probably fine because the code shouldn't be
michael@0:       // using the sync key directly (it should use the sync key
michael@0:       // bundle), but I don't like it. We should probably refactor
michael@0:       // code that is inspecting this to not do validation on this
michael@0:       // field directly and instead call a isSyncKeyValid() function
michael@0:       // that we can override.
michael@0:       return "99999999999999999999999999";
michael@0:     }
michael@0:     else {
michael@0:       return null;
michael@0:     }
michael@0:   },
michael@0: 
michael@0:   set syncKey(value) {
michael@0:     throw "syncKey setter should be not used in BrowserIDManager";
michael@0:   },
michael@0: 
michael@0:   get syncKeyBundle() {
michael@0:     return this._syncKeyBundle;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Resets/Drops all credentials we hold for the current user.
michael@0:    */
michael@0:   resetCredentials: function() {
michael@0:     this.resetSyncKey();
michael@0:     this._token = null;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Resets/Drops the sync key we hold for the current user.
michael@0:    */
michael@0:   resetSyncKey: function() {
michael@0:     this._syncKey = null;
michael@0:     this._syncKeyBundle = null;
michael@0:     this._syncKeyUpdated = true;
michael@0:     this._shouldHaveSyncKeyBundle = false;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * The current state of the auth credentials.
michael@0:    *
michael@0:    * This essentially validates that enough credentials are available to use
michael@0:    * Sync.
michael@0:    */
michael@0:   get currentAuthState() {
michael@0:     if (this._authFailureReason) {
michael@0:       this._log.info("currentAuthState returning " + this._authFailureReason +
michael@0:                      " due to previous failure");
michael@0:       return this._authFailureReason;
michael@0:     }
michael@0:     // TODO: need to revisit this. Currently this isn't ready to go until
michael@0:     // both the username and syncKeyBundle are both configured and having no
michael@0:     // username seems to make things fail fast so that's good.
michael@0:     if (!this.username) {
michael@0:       return LOGIN_FAILED_NO_USERNAME;
michael@0:     }
michael@0: 
michael@0:     // No need to check this.syncKey as our getter for that attribute
michael@0:     // uses this.syncKeyBundle
michael@0:     // If bundle creation started, but failed.
michael@0:     if (this._shouldHaveSyncKeyBundle && !this.syncKeyBundle) {
michael@0:       return LOGIN_FAILED_NO_PASSPHRASE;
michael@0:     }
michael@0: 
michael@0:     return STATUS_OK;
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Do we have a non-null, not yet expired token for the user currently
michael@0:    * signed in?
michael@0:    */
michael@0:   hasValidToken: function() {
michael@0:     if (!this._token) {
michael@0:       return false;
michael@0:     }
michael@0:     if (this._token.expiration < this._now()) {
michael@0:       return false;
michael@0:     }
michael@0:     return true;
michael@0:   },
michael@0: 
michael@0:   // Refresh the sync token for our user.
michael@0:   _fetchTokenForUser: function() {
michael@0:     let tokenServerURI = Svc.Prefs.get("tokenServerURI");
michael@0:     let log = this._log;
michael@0:     let client = this._tokenServerClient;
michael@0:     let fxa = this._fxaService;
michael@0:     let userData = this._signedInUser;
michael@0: 
michael@0:     log.info("Fetching assertion and token from: " + tokenServerURI);
michael@0: 
michael@0:     let maybeFetchKeys = () => {
michael@0:       // This is called at login time and every time we need a new token - in
michael@0:       // the latter case we already have kA and kB, so optimise that case.
michael@0:       if (userData.kA && userData.kB) {
michael@0:         return;
michael@0:       }
michael@0:       return this._fxaService.getKeys().then(
michael@0:         newUserData => {
michael@0:           userData = newUserData;
michael@0:           this._updateSignedInUser(userData); // throws if the user changed.
michael@0:         }
michael@0:       );
michael@0:     }
michael@0: 
michael@0:     let getToken = (tokenServerURI, assertion) => {
michael@0:       log.debug("Getting a token");
michael@0:       let deferred = Promise.defer();
michael@0:       let cb = function (err, token) {
michael@0:         if (err) {
michael@0:           return deferred.reject(err);
michael@0:         }
michael@0:         log.debug("Successfully got a sync token");
michael@0:         return deferred.resolve(token);
michael@0:       };
michael@0: 
michael@0:       let kBbytes = CommonUtils.hexToBytes(userData.kB);
michael@0:       let headers = {"X-Client-State": this._computeXClientState(kBbytes)};
michael@0:       client.getTokenFromBrowserIDAssertion(tokenServerURI, assertion, cb, headers);
michael@0:       return deferred.promise;
michael@0:     }
michael@0: 
michael@0:     let getAssertion = () => {
michael@0:       log.debug("Getting an assertion");
michael@0:       let audience = Services.io.newURI(tokenServerURI, null, null).prePath;
michael@0:       return fxa.getAssertion(audience);
michael@0:     };
michael@0: 
michael@0:     // wait until the account email is verified and we know that
michael@0:     // getAssertion() will return a real assertion (not null).
michael@0:     return fxa.whenVerified(this._signedInUser)
michael@0:       .then(() => maybeFetchKeys())
michael@0:       .then(() => getAssertion())
michael@0:       .then(assertion => getToken(tokenServerURI, assertion))
michael@0:       .then(token => {
michael@0:         // TODO: Make it be only 80% of the duration, so refresh the token
michael@0:         // before it actually expires. This is to avoid sync storage errors
michael@0:         // otherwise, we get a nasty notification bar briefly. Bug 966568.
michael@0:         token.expiration = this._now() + (token.duration * 1000) * 0.80;
michael@0:         if (!this._syncKeyBundle) {
michael@0:           // We are given kA/kB as hex.
michael@0:           this._syncKeyBundle = deriveKeyBundle(Utils.hexToBytes(userData.kB));
michael@0:         }
michael@0:         return token;
michael@0:       })
michael@0:       .then(null, err => {
michael@0:         // TODO: unify these errors - we need to handle errors thrown by
michael@0:         // both tokenserverclient and hawkclient.
michael@0:         // A tokenserver error thrown based on a bad response.
michael@0:         if (err.response && err.response.status === 401) {
michael@0:           err = new AuthenticationError(err);
michael@0:         // A hawkclient error.
michael@0:         } else if (err.code === 401) {
michael@0:           err = new AuthenticationError(err);
michael@0:         }
michael@0: 
michael@0:         // TODO: write tests to make sure that different auth error cases are handled here
michael@0:         // properly: auth error getting assertion, auth error getting token (invalid generation
michael@0:         // and client-state error)
michael@0:         if (err instanceof AuthenticationError) {
michael@0:           this._log.error("Authentication error in _fetchTokenForUser: " + err);
michael@0:           // set it to the "fatal" LOGIN_FAILED_LOGIN_REJECTED reason.
michael@0:           this._authFailureReason = LOGIN_FAILED_LOGIN_REJECTED;
michael@0:         } else {
michael@0:           this._log.error("Non-authentication error in _fetchTokenForUser: " + err.message);
michael@0:           // for now assume it is just a transient network related problem.
michael@0:           this._authFailureReason = LOGIN_FAILED_NETWORK_ERROR;
michael@0:         }
michael@0:         // Drop the sync key bundle, but still expect to have one.
michael@0:         // This will arrange for us to be in the right 'currentAuthState'
michael@0:         // such that UI will show the right error.
michael@0:         this._shouldHaveSyncKeyBundle = true;
michael@0:         Weave.Status.login = this._authFailureReason;
michael@0:         Services.obs.notifyObservers(null, "weave:service:login:error", null);
michael@0:         throw err;
michael@0:       });
michael@0:   },
michael@0: 
michael@0:   // Returns a promise that is resolved when we have a valid token for the
michael@0:   // current user stored in this._token.  When resolved, this._token is valid.
michael@0:   _ensureValidToken: function() {
michael@0:     if (this.hasValidToken()) {
michael@0:       this._log.debug("_ensureValidToken already has one");
michael@0:       return Promise.resolve();
michael@0:     }
michael@0:     return this._fetchTokenForUser().then(
michael@0:       token => {
michael@0:         this._token = token;
michael@0:       }
michael@0:     );
michael@0:   },
michael@0: 
michael@0:   getResourceAuthenticator: function () {
michael@0:     return this._getAuthenticationHeader.bind(this);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * Obtain a function to be used for adding auth to RESTRequest instances.
michael@0:    */
michael@0:   getRESTRequestAuthenticator: function() {
michael@0:     return this._addAuthenticationHeader.bind(this);
michael@0:   },
michael@0: 
michael@0:   /**
michael@0:    * @return a Hawk HTTP Authorization Header, lightly wrapped, for the .uri
michael@0:    * of a RESTRequest or AsyncResponse object.
michael@0:    */
michael@0:   _getAuthenticationHeader: function(httpObject, method) {
michael@0:     let cb = Async.makeSpinningCallback();
michael@0:     this._ensureValidToken().then(cb, cb);
michael@0:     try {
michael@0:       cb.wait();
michael@0:     } catch (ex) {
michael@0:       this._log.error("Failed to fetch a token for authentication: " + ex);
michael@0:       return null;
michael@0:     }
michael@0:     if (!this._token) {
michael@0:       return null;
michael@0:     }
michael@0:     let credentials = {algorithm: "sha256",
michael@0:                        id: this._token.id,
michael@0:                        key: this._token.key,
michael@0:                       };
michael@0:     method = method || httpObject.method;
michael@0: 
michael@0:     // Get the local clock offset from the Firefox Accounts server.  This should
michael@0:     // be close to the offset from the storage server.
michael@0:     let options = {
michael@0:       now: this._now(),
michael@0:       localtimeOffsetMsec: this._localtimeOffsetMsec,
michael@0:       credentials: credentials,
michael@0:     };
michael@0: 
michael@0:     let headerValue = CryptoUtils.computeHAWK(httpObject.uri, method, options);
michael@0:     return {headers: {authorization: headerValue.field}};
michael@0:   },
michael@0: 
michael@0:   _addAuthenticationHeader: function(request, method) {
michael@0:     let header = this._getAuthenticationHeader(request, method);
michael@0:     if (!header) {
michael@0:       return null;
michael@0:     }
michael@0:     request.setHeader("authorization", header.headers.authorization);
michael@0:     return request;
michael@0:   },
michael@0: 
michael@0:   createClusterManager: function(service) {
michael@0:     return new BrowserIDClusterManager(service);
michael@0:   }
michael@0: 
michael@0: };
michael@0: 
michael@0: /* An implementation of the ClusterManager for this identity
michael@0:  */
michael@0: 
michael@0: function BrowserIDClusterManager(service) {
michael@0:   ClusterManager.call(this, service);
michael@0: }
michael@0: 
michael@0: BrowserIDClusterManager.prototype = {
michael@0:   __proto__: ClusterManager.prototype,
michael@0: 
michael@0:   _findCluster: function() {
michael@0:     let endPointFromIdentityToken = function() {
michael@0:       let endpoint = this.identity._token.endpoint;
michael@0:       // For Sync 1.5 storage endpoints, we use the base endpoint verbatim.
michael@0:       // However, it should end in "/" because we will extend it with
michael@0:       // well known path components. So we add a "/" if it's missing.
michael@0:       if (!endpoint.endsWith("/")) {
michael@0:         endpoint += "/";
michael@0:       }
michael@0:       log.debug("_findCluster returning " + endpoint);
michael@0:       return endpoint;
michael@0:     }.bind(this);
michael@0: 
michael@0:     // Spinningly ensure we are ready to authenticate and have a valid token.
michael@0:     let promiseClusterURL = function() {
michael@0:       return this.identity.whenReadyToAuthenticate.promise.then(
michael@0:         () => {
michael@0:           // We need to handle node reassignment here.  If we are being asked
michael@0:           // for a clusterURL while the service already has a clusterURL, then
michael@0:           // it's likely a 401 was received using the existing token - in which
michael@0:           // case we just discard the existing token and fetch a new one.
michael@0:           if (this.service.clusterURL) {
michael@0:             log.debug("_findCluster found existing clusterURL, so discarding the current token");
michael@0:             this.identity._token = null;
michael@0:           }
michael@0:           return this.identity._ensureValidToken();
michael@0:         }
michael@0:       ).then(endPointFromIdentityToken
michael@0:       );
michael@0:     }.bind(this);
michael@0: 
michael@0:     let cb = Async.makeSpinningCallback();
michael@0:     promiseClusterURL().then(function (clusterURL) {
michael@0:       cb(null, clusterURL);
michael@0:     }).then(
michael@0:       null, err => {
michael@0:       // service.js's verifyLogin() method will attempt to fetch a cluster
michael@0:       // URL when it sees a 401.  If it gets null, it treats it as a "real"
michael@0:       // auth error and sets Status.login to LOGIN_FAILED_LOGIN_REJECTED, which
michael@0:       // in turn causes a notification bar to appear informing the user they
michael@0:       // need to re-authenticate.
michael@0:       // On the other hand, if fetching the cluster URL fails with an exception,
michael@0:       // verifyLogin() assumes it is a transient error, and thus doesn't show
michael@0:       // the notification bar under the assumption the issue will resolve
michael@0:       // itself.
michael@0:       // Thus:
michael@0:       // * On a real 401, we must return null.
michael@0:       // * On any other problem we must let an exception bubble up.
michael@0:       if (err instanceof AuthenticationError) {
michael@0:         // callback with no error and a null result - cb.wait() returns null.
michael@0:         cb(null, null);
michael@0:       } else {
michael@0:         // callback with an error - cb.wait() completes by raising an exception.
michael@0:         cb(err);
michael@0:       }
michael@0:     });
michael@0:     return cb.wait();
michael@0:   },
michael@0: 
michael@0:   getUserBaseURL: function() {
michael@0:     // Legacy Sync and FxA Sync construct the userBaseURL differently. Legacy
michael@0:     // Sync appends path components onto an empty path, and in FxA Sync the
michael@0:     // token server constructs this for us in an opaque manner. Since the
michael@0:     // cluster manager already sets the clusterURL on Service and also has
michael@0:     // access to the current identity, we added this functionality here.
michael@0:     return this.service.clusterURL;
michael@0:   }
michael@0: }