Write Firebase Token to Auth instance during exchange_token API

packages/auth/src/api/authentication/exchange_token.ts

@@ -27,8 +27,10 @@ export interface ExchangeTokenRequest {
 }
 
 export interface ExchangeTokenResponse {
+  // The firebase access token (JWT signed by Firebase Auth).
   accessToken: string;
-  expiresIn?: string;
+  // The time when the access token expires.
+  expiresIn: number;
 }
 
 export async function exchangeToken(

packages/auth/src/core/auth/auth_impl.ts

@@ -37,7 +37,8 @@ import {
   NextFn,
   Unsubscribe,
   PasswordValidationStatus,
-  TenantConfig
+  TenantConfig,
+  FirebaseToken
 } from '../../model/public_types';
 import {
   createSubscribe,
@@ -100,6 +101,7 @@ export const enum DefaultConfig {
 export class AuthImpl implements AuthInternal, _FirebaseService {
   currentUser: User | null = null;
   emulatorConfig: EmulatorConfig | null = null;
+  firebaseToken: FirebaseToken | null = null;
   private operations = Promise.resolve();
   private persistenceManager?: PersistenceUserManager;
   private redirectPersistenceManager?: PersistenceUserManager;
@@ -455,6 +457,12 @@ export class AuthImpl implements AuthInternal, _FirebaseService {
     });
   }
 
+  async _updateFirebaseToken(firebaseToken: FirebaseToken | null): Promise<void> {
+      if (firebaseToken) {
+      this.firebaseToken = firebaseToken;
+    }
+  }
+
   async signOut(): Promise<void> {
     if (_isFirebaseServerApp(this.app)) {
       return Promise.reject(

packages/auth/src/core/strategies/exchange_token.test.ts

@@ -24,6 +24,7 @@ import {
   testAuth,
   TestAuth
 } from '../../../test/helpers/mock_auth';
+import * as sinon from 'sinon';
 import * as mockFetch from '../../../test/helpers/mock_fetch';
 import { HttpHeader, RegionalEndpoint } from '../../api';
 import { exchangeToken } from './exhange_token';
@@ -35,19 +36,23 @@ use(chaiAsPromised);
 describe('core/strategies/exchangeToken', () => {
   let auth: TestAuth;
   let regionalAuth: TestAuth;
+  let now: number;
 
   beforeEach(async () => {
     auth = await testAuth();
     regionalAuth = await regionalTestAuth();
     mockFetch.setUp();
+    now = Date.now();
+    sinon.stub(Date, 'now').returns(now);
   });
   afterEach(mockFetch.tearDown);
+  afterEach(() => sinon.restore());
 
   it('should return a valid access token for Regional Auth', async () => {
     const mock = mockRegionalEndpointWithParent(
       RegionalEndpoint.EXCHANGE_TOKEN,
       'projects/test-project-id/locations/us/tenants/tenant-1/idpConfigs/idp-config',
-      { accessToken: 'outbound-token', expiresIn: '1000' }
+      { accessToken: 'outbound-token', expiresIn: 10000 }
     );
 
     const accessToken = await exchangeToken(
@@ -65,6 +70,8 @@ describe('core/strategies/exchangeToken', () => {
     expect(mock.calls[0].headers!.get(HttpHeader.CONTENT_TYPE)).to.eq(
       'application/json'
     );
+    expect(regionalAuth.firebaseToken?.token).to.equal('outbound-token');
+    expect(regionalAuth.firebaseToken?.expirationTime).to.equal(now + 10_000);
   });
 
   it('throws exception for default Auth', async () => {
@@ -106,5 +113,6 @@ describe('core/strategies/exchangeToken', () => {
     expect(mock.calls[0].headers!.get(HttpHeader.CONTENT_TYPE)).to.eq(
       'application/json'
     );
+    expect(regionalAuth.firebaseToken).is.null;
   });
 });

packages/auth/src/core/strategies/exhange_token.ts

@@ -54,7 +54,12 @@ export async function exchangeToken(
     parent: buildParent(auth, idpConfigId),
     token: customToken
   });
-  // TODO(sammansi): Write token to the Auth object passed.
+  if (token) {
+    await authInternal._updateFirebaseToken({
+      token: token.accessToken,
+      expirationTime: Date.now() + token.expiresIn * 1000
+    });
+  }
   return token.accessToken;
 }
 

packages/auth/src/model/auth.ts

@@ -20,6 +20,7 @@ import {
   AuthSettings,
   Config,
   EmulatorConfig,
+  FirebaseToken,
   PasswordPolicy,
   PasswordValidationStatus,
   PopupRedirectResolver,
@@ -75,6 +76,7 @@ export interface AuthInternal extends Auth {
   _initializationPromise: Promise<void> | null;
   _persistenceManagerAvailable: Promise<void>;
   _updateCurrentUser(user: UserInternal | null): Promise<void>;
+  _updateFirebaseToken(firebaseToken: FirebaseToken | null): Promise<void>;
 
   _onStorageEvent(): void;
 

packages/auth/src/model/public_types.ts

@@ -334,6 +334,14 @@ export interface Auth {
    * {@link @firebase/app#FirebaseServerApp}.
    */
   signOut(): Promise<void>;
+  /**
+   * The token response initialized via {@link exchangeToken} endpoint.
+   *
+   * @remarks
+   * This field is only supported for {@link Auth} instance that have defined
+   * {@link TenantConfig}.
+   */
+  readonly firebaseToken: FirebaseToken | null;
 }
 
 /**
@@ -966,6 +974,13 @@ export interface ReactNativeAsyncStorage {
   removeItem(key: string): Promise<void>;
 }
 
+export interface FirebaseToken {
+  // The firebase access token (JWT signed by Firebase Auth).
+  readonly token: string;
+  // The time when the access token expires.
+  readonly expirationTime: number; 
+}
+
 /**
  * A user account.
  *