Implement App Check auto refresh timing and opt out flag (#4847)

Author: hsubox76

packages/app-check-types/index.d.ts

@@ -18,9 +18,17 @@
 export interface FirebaseAppCheck {
   /**
    * Activate AppCheck
-   * @param siteKeyOrOrovider - reCAPTCHA sitekey or custom token provider
+   * @param siteKeyOrProvider - reCAPTCHA sitekey or custom token provider
+   * @param isTokenAutoRefreshEnabled - If true, enables SDK to automatically
+   * refresh AppCheck token as needed. If undefined, the value will default
+   * to the value of `app.automaticDataCollectionEnabled`. That property
+   * defaults to false and can be set in the app config.
    */
-  activate(siteKeyOrProvider: string | AppCheckProvider): void;
+  activate(
+    siteKeyOrProvider: string | AppCheckProvider,
+    isTokenAutoRefreshEnabled?: boolean
+  ): void;
+  setTokenAutoRefreshEnabled(isTokenAutoRefreshEnabled: boolean): void;
 }
 
 interface AppCheckProvider {

packages/app-check/src/api.test.ts

@@ -17,7 +17,7 @@
 import '../test/setup';
 import { expect } from 'chai';
 import { stub } from 'sinon';
-import { activate } from './api';
+import { activate, setTokenAutoRefreshEnabled } from './api';
 import {
   FAKE_SITE_KEY,
   getFakeApp,
@@ -41,6 +41,18 @@ describe('api', () => {
       expect(getState(app).activated).to.equal(true);
     });
 
+    it('isTokenAutoRefreshEnabled value defaults to global setting', () => {
+      app = getFakeApp({ automaticDataCollectionEnabled: false });
+      activate(app, FAKE_SITE_KEY);
+      expect(getState(app).isTokenAutoRefreshEnabled).to.equal(false);
+    });
+
+    it('sets isTokenAutoRefreshEnabled correctly, overriding global setting', () => {
+      app = getFakeApp({ automaticDataCollectionEnabled: false });
+      activate(app, FAKE_SITE_KEY, true);
+      expect(getState(app).isTokenAutoRefreshEnabled).to.equal(true);
+    });
+
     it('can only be called once', () => {
       activate(app, FAKE_SITE_KEY);
       expect(() => activate(app, FAKE_SITE_KEY)).to.throw(
@@ -67,4 +79,11 @@ describe('api', () => {
       expect(initReCAPTCHAStub).to.have.not.been.called;
     });
   });
+  describe('setTokenAutoRefreshEnabled()', () => {
+    it('sets isTokenAutoRefreshEnabled correctly', () => {
+      const app = getFakeApp({ automaticDataCollectionEnabled: false });
+      setTokenAutoRefreshEnabled(app, true);
+      expect(getState(app).isTokenAutoRefreshEnabled).to.equal(true);
+    });
+  });
 });

packages/app-check/src/api.ts

@@ -24,11 +24,15 @@ import { getState, setState, AppCheckState } from './state';
 /**
  *
  * @param app
- * @param provider - optional custom attestation provider
+ * @param siteKeyOrProvider - optional custom attestation provider
+ * or reCAPTCHA siteKey
+ * @param isTokenAutoRefreshEnabled - if true, enables auto refresh
+ * of appCheck token.
  */
 export function activate(
   app: FirebaseApp,
-  siteKeyOrProvider: string | AppCheckProvider
+  siteKeyOrProvider: string | AppCheckProvider,
+  isTokenAutoRefreshEnabled?: boolean
 ): void {
   const state = getState(app);
   if (state.activated) {
@@ -44,6 +48,14 @@ export function activate(
     newState.customProvider = siteKeyOrProvider;
   }
 
+  // Use value of global `automaticDataCollectionEnabled` (which
+  // itself defaults to false if not specified in config) if
+  // `isTokenAutoRefreshEnabled` param was not provided by user.
+  newState.isTokenAutoRefreshEnabled =
+    isTokenAutoRefreshEnabled === undefined
+      ? app.automaticDataCollectionEnabled
+      : isTokenAutoRefreshEnabled;
+
   setState(app, newState);
 
   // initialize reCAPTCHA if siteKey is provided
@@ -53,3 +65,20 @@ export function activate(
     });
   }
 }
+
+export function setTokenAutoRefreshEnabled(
+  app: FirebaseApp,
+  isTokenAutoRefreshEnabled: boolean
+): void {
+  const state = getState(app);
+  // This will exist if any product libraries have called
+  // `addTokenListener()`
+  if (state.tokenRefresher) {
+    if (isTokenAutoRefreshEnabled === true) {
+      state.tokenRefresher.start();
+    } else {
+      state.tokenRefresher.stop();
+    }
+  }
+  setState(app, { ...state, isTokenAutoRefreshEnabled });
+}

packages/app-check/src/client.test.ts

@@ -74,7 +74,8 @@ describe('client', () => {
 
     expect(response).to.deep.equal({
       token: 'fake-appcheck-token',
-      expireTimeMillis: 3600
+      expireTimeMillis: 3600,
+      issuedAtTimeMillis: 0
     });
   });
 

packages/app-check/src/client.ts

@@ -22,8 +22,8 @@ import {
 } from './constants';
 import { FirebaseApp } from '@firebase/app-types';
 import { ERROR_FACTORY, AppCheckError } from './errors';
-import { AppCheckToken } from '@firebase/app-check-types';
 import { Provider } from '@firebase/component';
+import { AppCheckTokenInternal } from './state';
 
 /**
  * Response JSON returned from AppCheck server endpoint.
@@ -42,7 +42,7 @@ interface AppCheckRequest {
 export async function exchangeToken(
   { url, body }: AppCheckRequest,
   platformLoggerProvider: Provider<'platform-logger'>
-): Promise<AppCheckToken> {
+): Promise<AppCheckTokenInternal> {
   const headers: HeadersInit = {
     'Content-Type': 'application/json'
   };
@@ -95,9 +95,11 @@ export async function exchangeToken(
   }
   const timeToLiveAsNumber = Number(match[1]) * 1000;
 
+  const now = Date.now();
   return {
     token: responseBody.attestationToken,
-    expireTimeMillis: Date.now() + timeToLiveAsNumber
+    expireTimeMillis: now + timeToLiveAsNumber,
+    issuedAtTimeMillis: now
   };
 }
 

packages/app-check/src/factory.ts

@@ -16,7 +16,7 @@
  */
 
 import { FirebaseAppCheck, AppCheckProvider } from '@firebase/app-check-types';
-import { activate } from './api';
+import { activate, setTokenAutoRefreshEnabled } from './api';
 import { FirebaseApp } from '@firebase/app-types';
 import { FirebaseAppCheckInternal } from '@firebase/app-check-interop-types';
 import {
@@ -28,8 +28,12 @@ import { Provider } from '@firebase/component';
 
 export function factory(app: FirebaseApp): FirebaseAppCheck {
   return {
-    activate: (siteKeyOrProvider: string | AppCheckProvider) =>
-      activate(app, siteKeyOrProvider)
+    activate: (
+      siteKeyOrProvider: string | AppCheckProvider,
+      isTokenAutoRefreshEnabled?: boolean
+    ) => activate(app, siteKeyOrProvider, isTokenAutoRefreshEnabled),
+    setTokenAutoRefreshEnabled: (isTokenAutoRefreshEnabled: boolean) =>
+      setTokenAutoRefreshEnabled(app, isTokenAutoRefreshEnabled)
   };
 }
 

packages/app-check/src/indexeddb.ts

@@ -15,9 +15,9 @@
  * limitations under the License.
  */
 
-import { AppCheckToken } from '@firebase/app-check-types';
 import { FirebaseApp } from '@firebase/app-types';
 import { ERROR_FACTORY, AppCheckError } from './errors';
+import { AppCheckTokenInternal } from './state';
 const DB_NAME = 'firebase-app-check-database';
 const DB_VERSION = 1;
 const STORE_NAME = 'firebase-app-check-store';
@@ -74,13 +74,13 @@ function getDBPromise(): Promise<IDBDatabase> {
 
 export function readTokenFromIndexedDB(
   app: FirebaseApp
-): Promise<AppCheckToken | undefined> {
-  return read(computeKey(app)) as Promise<AppCheckToken | undefined>;
+): Promise<AppCheckTokenInternal | undefined> {
+  return read(computeKey(app)) as Promise<AppCheckTokenInternal | undefined>;
 }
 
 export function writeTokenToIndexedDB(
   app: FirebaseApp,
-  token: AppCheckToken
+  token: AppCheckTokenInternal
 ): Promise<void> {
   return write(computeKey(app), token);
 }

packages/app-check/src/internal-api.test.ts

@@ -59,12 +59,14 @@ describe('internal api', () => {
     const fakeRecaptchaToken = 'fake-recaptcha-token';
     const fakeRecaptchaAppCheckToken = {
       token: 'fake-recaptcha-app-check-token',
-      expireTimeMillis: 123
+      expireTimeMillis: 123,
+      issuedAtTimeMillis: 0
     };
 
     const fakeCachedAppCheckToken = {
       token: 'fake-cached-app-check-token',
-      expireTimeMillis: 123
+      expireTimeMillis: 123,
+      issuedAtTimeMillis: 0
     };
 
     it('uses customTokenProvider to get an AppCheck token', async () => {
@@ -295,6 +297,7 @@ describe('internal api', () => {
 
     it('starts proactively refreshing token after adding the first listener', () => {
       const listener = (): void => {};
+      setState(app, { ...getState(app), isTokenAutoRefreshEnabled: true });
       expect(getState(app).tokenListeners.length).to.equal(0);
       expect(getState(app).tokenRefresher).to.equal(undefined);
 
@@ -317,7 +320,8 @@ describe('internal api', () => {
         ...getState(app),
         token: {
           token: `fake-memory-app-check-token`,
-          expireTimeMillis: 123
+          expireTimeMillis: 123,
+          issuedAtTimeMillis: 0
         }
       });
 
@@ -330,7 +334,8 @@ describe('internal api', () => {
       stub(storage, 'readTokenFromStorage').returns(
         Promise.resolve({
           token: `fake-cached-app-check-token`,
-          expireTimeMillis: 123
+          expireTimeMillis: 123,
+          issuedAtTimeMillis: 0
         })
       );
 
@@ -389,6 +394,7 @@ describe('internal api', () => {
 
     it('should stop proactively refreshing token after deleting the last listener', () => {
       const listener = (): void => {};
+      setState(app, { ...getState(app), isTokenAutoRefreshEnabled: true });
 
       addTokenListener(app, fakePlatformLoggingProvider, listener);
       expect(getState(app).tokenListeners.length).to.equal(1);

packages/app-check/src/internal-api.ts

@@ -21,8 +21,12 @@ import {
   AppCheckTokenResult,
   AppCheckTokenListener
 } from '@firebase/app-check-interop-types';
-import { AppCheckToken } from '@firebase/app-check-types';
-import { getDebugState, getState, setState } from './state';
+import {
+  AppCheckTokenInternal,
+  getDebugState,
+  getState,
+  setState
+} from './state';
 import { TOKEN_REFRESH_TIME } from './constants';
 import { Refresher } from './proactive-refresh';
 import { ensureActivated } from './util';
@@ -33,7 +37,7 @@ import {
 } from './client';
 import { writeTokenToStorage, readTokenFromStorage } from './storage';
 import { getDebugToken, isDebugMode } from './debug';
-import { base64 } from '@firebase/util';
+import { base64, issuedAtTime } from '@firebase/util';
 import { ERROR_FACTORY, AppCheckError } from './errors';
 import { logger } from './logger';
 import { Provider } from '@firebase/component';
@@ -72,7 +76,7 @@ export async function getToken(
    * return the debug token directly
    */
   if (isDebugMode()) {
-    const tokenFromDebugExchange: AppCheckToken = await exchangeToken(
+    const tokenFromDebugExchange: AppCheckTokenInternal = await exchangeToken(
       getExchangeDebugTokenRequest(app, await getDebugToken()),
       platformLoggerProvider
     );
@@ -81,7 +85,7 @@ export async function getToken(
 
   const state = getState(app);
 
-  let token: AppCheckToken | undefined = state.token;
+  let token: AppCheckTokenInternal | undefined = state.token;
   let error: Error | undefined = undefined;
 
   /**
@@ -111,7 +115,20 @@ export async function getToken(
    */
   try {
     if (state.customProvider) {
-      token = await state.customProvider.getToken();
+      const customToken = await state.customProvider.getToken();
+      // Try to extract IAT from custom token, in case this token is not
+      // being newly issued. JWT timestamps are in seconds since epoch.
+      const issuedAtTimeSeconds = issuedAtTime(customToken.token);
+      // Very basic validation, use current timestamp as IAT if JWT
+      // has no `iat` field or value is out of bounds.
+      const issuedAtTimeMillis =
+        issuedAtTimeSeconds !== null &&
+        issuedAtTimeSeconds < Date.now() &&
+        issuedAtTimeSeconds > 0
+          ? issuedAtTimeSeconds * 1000
+          : Date.now();
+
+      token = { ...customToken, issuedAtTimeMillis };
     } else {
       const attestedClaimsToken = await getReCAPTCHAToken(app).catch(_e => {
         // reCaptcha.execute() throws null which is not very descriptive.
@@ -183,7 +200,12 @@ export function addTokenListener(
       newState.tokenRefresher = tokenRefresher;
     }
 
-    if (!newState.tokenRefresher.isRunning()) {
+    // Create the refresher but don't start it if `isTokenAutoRefreshEnabled`
+    // is not true.
+    if (
+      !newState.tokenRefresher.isRunning() &&
+      state.isTokenAutoRefreshEnabled === true
+    ) {
       newState.tokenRefresher.start();
     }
 
@@ -253,12 +275,20 @@ function createTokenRefresher(
       const state = getState(app);
 
       if (state.token) {
-        return Math.max(
-          0,
-          state.token.expireTimeMillis -
-            Date.now() -
-            TOKEN_REFRESH_TIME.OFFSET_DURATION
+        // issuedAtTime + (50% * total TTL) + 5 minutes
+        let nextRefreshTimeMillis =
+          state.token.issuedAtTimeMillis +
+          (state.token.expireTimeMillis - state.token.issuedAtTimeMillis) *
+            0.5 +
+          5 * 60 * 1000;
+        // Do not allow refresh time to be past (expireTime - 5 minutes)
+        const latestAllowableRefresh =
+          state.token.expireTimeMillis - 5 * 60 * 1000;
+        nextRefreshTimeMillis = Math.min(
+          nextRefreshTimeMillis,
+          latestAllowableRefresh
         );
+        return Math.max(0, nextRefreshTimeMillis - Date.now());
       } else {
         return 0;
       }
@@ -283,7 +313,7 @@ function notifyTokenListeners(
   }
 }
 
-function isValid(token: AppCheckToken): boolean {
+function isValid(token: AppCheckTokenInternal): boolean {
   return token.expireTimeMillis - Date.now() > 0;
 }
 

packages/app-check/src/state.ts

@@ -21,14 +21,19 @@ import { AppCheckTokenListener } from '@firebase/app-check-interop-types';
 import { Refresher } from './proactive-refresh';
 import { Deferred } from '@firebase/util';
 import { GreCAPTCHA } from './recaptcha';
+
+export interface AppCheckTokenInternal extends AppCheckToken {
+  issuedAtTimeMillis: number;
+}
 export interface AppCheckState {
   activated: boolean;
   tokenListeners: AppCheckTokenListener[];
   customProvider?: AppCheckProvider;
   siteKey?: string;
-  token?: AppCheckToken;
+  token?: AppCheckTokenInternal;
   tokenRefresher?: Refresher;
   reCAPTCHAState?: ReCAPTCHAState;
+  isTokenAutoRefreshEnabled?: boolean;
 }
 
 export interface ReCAPTCHAState {