[web] Use TrustedTypes in flutter.js and other tools (#112969)

dev/bots/service_worker_test.dart

@@ -25,12 +25,18 @@ final String _targetWithBlockedServiceWorkers = path.join('lib', 'service_worker
 final String _targetPath = path.join(_testAppDirectory, _target);
 
 enum ServiceWorkerTestType {
+  // Mocks how FF disables service workers.
   blockedServiceWorkers,
+  // Drops the main.dart.js directly on the page.
   withoutFlutterJs,
+  // Uses the standard, promise-based, flutterJS initialization.
   withFlutterJs,
+  // Uses the shorthand engineInitializer.autoStart();
   withFlutterJsShort,
+  // Uses onEntrypointLoaded callback instead of returned promise.
   withFlutterJsEntrypointLoadedEvent,
-
+  // Same as withFlutterJsEntrypointLoadedEvent, but with TrustedTypes enabled.
+  withFlutterJsTrustedTypesOn,
   // Entrypoint generated by `flutter create`.
   generatedEntrypoint,
 }
@@ -44,10 +50,12 @@ Future<void> main() async {
   await runWebServiceWorkerTest(headless: false, testType: ServiceWorkerTestType.withFlutterJs);
   await runWebServiceWorkerTest(headless: false, testType: ServiceWorkerTestType.withFlutterJsShort);
   await runWebServiceWorkerTest(headless: false, testType: ServiceWorkerTestType.withFlutterJsEntrypointLoadedEvent);
+  await runWebServiceWorkerTest(headless: false, testType: ServiceWorkerTestType.withFlutterJsTrustedTypesOn);
   await runWebServiceWorkerTestWithCachingResources(headless: false, testType: ServiceWorkerTestType.withoutFlutterJs);
   await runWebServiceWorkerTestWithCachingResources(headless: false, testType: ServiceWorkerTestType.withFlutterJs);
   await runWebServiceWorkerTestWithCachingResources(headless: false, testType: ServiceWorkerTestType.withFlutterJsShort);
   await runWebServiceWorkerTestWithCachingResources(headless: false, testType: ServiceWorkerTestType.withFlutterJsEntrypointLoadedEvent);
+  await runWebServiceWorkerTestWithCachingResources(headless: false, testType: ServiceWorkerTestType.withFlutterJsTrustedTypesOn);
   await runWebServiceWorkerTestWithGeneratedEntrypoint(headless: false);
   await runWebServiceWorkerTestWithBlockedServiceWorkers(headless: false);
 
@@ -112,6 +120,9 @@ String _testTypeToIndexFile(ServiceWorkerTestType type) {
     case ServiceWorkerTestType.withFlutterJsEntrypointLoadedEvent:
       indexFile = 'index_with_flutterjs_entrypoint_loaded.html';
       break;
+    case ServiceWorkerTestType.withFlutterJsTrustedTypesOn:
+      indexFile = 'index_with_flutterjs_el_tt_on.html';
+      break;
     case ServiceWorkerTestType.generatedEntrypoint:
       indexFile = 'generated_entrypoint.html';
       break;

dev/bots/test.dart

@@ -1195,10 +1195,12 @@ Future<void> _runWebLongRunningTests() async {
     () => runWebServiceWorkerTest(headless: true, testType: ServiceWorkerTestType.withFlutterJs),
     () => runWebServiceWorkerTest(headless: true, testType: ServiceWorkerTestType.withFlutterJsShort),
     () => runWebServiceWorkerTest(headless: true, testType: ServiceWorkerTestType.withFlutterJsEntrypointLoadedEvent),
+    () => runWebServiceWorkerTest(headless: true, testType: ServiceWorkerTestType.withFlutterJsTrustedTypesOn),
     () => runWebServiceWorkerTestWithCachingResources(headless: true, testType: ServiceWorkerTestType.withoutFlutterJs),
     () => runWebServiceWorkerTestWithCachingResources(headless: true, testType: ServiceWorkerTestType.withFlutterJs),
     () => runWebServiceWorkerTestWithCachingResources(headless: true, testType: ServiceWorkerTestType.withFlutterJsShort),
     () => runWebServiceWorkerTestWithCachingResources(headless: true, testType: ServiceWorkerTestType.withFlutterJsEntrypointLoadedEvent),
+    () => runWebServiceWorkerTestWithCachingResources(headless: true, testType: ServiceWorkerTestType.withFlutterJsTrustedTypesOn),
     () => runWebServiceWorkerTestWithGeneratedEntrypoint(headless: true),
     () => runWebServiceWorkerTestWithBlockedServiceWorkers(headless: true),
     () => _runWebStackTraceTest('profile', 'lib/stack_trace.dart'),

dev/integration_tests/web/web/index_with_flutterjs_el_tt_on.html

@@ -0,0 +1,46 @@
+<!DOCTYPE HTML>
+<!-- Copyright 2014 The Flutter Authors. All rights reserved.
+Use of this source code is governed by a BSD-style license that can be
+found in the LICENSE file. -->
+<html>
+<head>
+  <meta charset="UTF-8">
+  <meta content="IE=Edge" http-equiv="X-UA-Compatible">
+
+  <title>Integration test. App load with flutter.js and onEntrypointLoaded API. Trusted Types enabled.</title>
+
+  <!-- Enable TrustedTypes for 'script'-->
+  <meta http-equiv="Content-Security-Policy" content="require-trusted-types-for 'script'">
+
+  <!-- iOS meta tags & icons -->
+  <meta name="apple-mobile-web-app-capable" content="yes">
+  <meta name="apple-mobile-web-app-status-bar-style" content="black">
+  <meta name="apple-mobile-web-app-title" content="Web Test">
+  <link rel="manifest" href="manifest.json">
+  <script>
+    // The value below is injected by flutter build, do not touch.
+    var serviceWorkerVersion = null;
+  </script>
+  <!-- This script adds the flutter initialization JS code -->
+  <script src="flutter.js" defer></script>
+</head>
+<body>
+  <script>
+    window.addEventListener('load', function(ev) {
+      // Download main.dart.js
+      _flutter.loader.loadEntrypoint({
+        onEntrypointLoaded: onEntrypointLoaded,
+        serviceWorker: {
+          serviceWorkerVersion: serviceWorkerVersion,
+        }
+      });
+
+      // Once the entrypoint is ready, do things!
+      async function onEntrypointLoaded(engineInitializer) {
+        const appRunner = await engineInitializer.initializeEngine();
+        appRunner.runApp();
+      }
+    });
+  </script>
+</body>
+</html>

packages/flutter_tools/lib/src/web/bootstrap.dart

@@ -94,18 +94,45 @@ document.addEventListener('dart-app-ready', function (e) {
    styleSheet.parentNode.removeChild(styleSheet);
 });
 
+// A map containing the URLs for the bootstrap scripts in debug.
+let _scriptUrls = {
+  "mapper": "$mapperUrl",
+  "requireJs": "$requireUrl"
+};
+
+// Create a TrustedTypes policy so we can attach Scripts...
+let _ttPolicy;
+if (window.trustedTypes) {
+  _ttPolicy = trustedTypes.createPolicy("flutter-tools-bootstrap", {
+    createScriptURL: (url) => {
+      let scriptUrl = _scriptUrls[url];
+      if (!scriptUrl) {
+        console.error("Unknown Flutter Web bootstrap resource!", url);
+      }
+      return scriptUrl;
+    }
+  });
+}
+
+// Creates a TrustedScriptURL for a given `scriptName`.
+// See `_scriptUrls` and `_ttPolicy` above.
+function getTTScriptUrl(scriptName) {
+  let defaultUrl = _scriptUrls[scriptName];
+  return _ttPolicy ? _ttPolicy.createScriptURL(scriptName) : defaultUrl;
+}
+
 // Attach source mapping.
 var mapperEl = document.createElement("script");
 mapperEl.defer = true;
 mapperEl.async = false;
-mapperEl.src = "$mapperUrl";
+mapperEl.src = getTTScriptUrl("mapper");
 document.head.appendChild(mapperEl);
 
 // Attach require JS.
 var requireEl = document.createElement("script");
 requireEl.defer = true;
 requireEl.async = false;
-requireEl.src = "$requireUrl";
+requireEl.src = getTTScriptUrl("requireJs");
 // This attribute tells require JS what to load as main (defined below).
 requireEl.setAttribute("data-main", "main_module.bootstrap");
 document.head.appendChild(requireEl);

packages/flutter_tools/lib/src/web/file_generators/flutter_js.dart

@@ -56,12 +56,53 @@ _flutter.loader = null;
     });
   }
 
+  /**
+   * Handles the creation of a TrustedTypes `policy` that validates URLs based
+   * on an (optional) incoming array of RegExes.
+   */
+  class FlutterTrustedTypesPolicy {
+    /**
+     * Constructs the policy.
+     * @param {[RegExp]} validPatterns the patterns to test URLs
+     * @param {String} policyName the policy name (optional)
+     */
+    constructor(validPatterns, policyName = "flutter-js") {
+      const patterns = validPatterns || [
+        /\.dart\.js$/,
+        /^flutter_service_worker.js$/
+      ];
+      if (window.trustedTypes) {
+        this.policy = trustedTypes.createPolicy(policyName, {
+          createScriptURL: function(url) {
+            const parsed = new URL(url, window.location);
+            const file = parsed.pathname.split("/").pop();
+            const matches = patterns.some((pattern) => pattern.test(file));
+            if (matches) {
+              return parsed.toString();
+            }
+            console.error(
+              "URL rejected by TrustedTypes policy",
+              policyName, ":", url, "(download prevented)");
+          }
+        });
+      }
+    }
+  }
+
   /**
    * Handles loading/reloading Flutter's service worker, if configured.
    *
    * @see: https://developers.google.com/web/fundamentals/primers/service-workers
    */
   class FlutterServiceWorkerLoader {
+    /**
+     * Injects a TrustedTypesPolicy (or undefined if the feature is not supported).
+     * @param {TrustedTypesPolicy | undefined} policy
+     */
+    setTrustedTypesPolicy(policy) {
+      this._ttPolicy = policy;
+    }
+
     /**
      * Returns a Promise that resolves when the latest Flutter service worker,
      * configured by `settings` has been loaded and activated.
@@ -84,8 +125,14 @@ _flutter.loader = null;
         timeoutMillis = 4000,
       } = settings;
 
+      // Apply the TrustedTypes policy, if present.
+      let url = serviceWorkerUrl;
+      if (this._ttPolicy != null) {
+        url = this._ttPolicy.createScriptURL(url);
+      }
+
       const serviceWorkerActivation = navigator.serviceWorker
-        .register(serviceWorkerUrl)
+        .register(url)
         .then(this._getNewServiceWorker)
         .then(this._waitForServiceWorkerActivation);
 
@@ -173,6 +220,14 @@ _flutter.loader = null;
       this._scriptLoaded = false;
     }
 
+    /**
+     * Injects a TrustedTypesPolicy (or undefined if the feature is not supported).
+     * @param {TrustedTypesPolicy | undefined} policy
+     */
+    setTrustedTypesPolicy(policy) {
+      this._ttPolicy = policy;
+    }
+
     /**
      * Loads flutter main entrypoint, specified by `entrypointUrl`, and calls a
      * user-specified `onEntrypointLoaded` callback with an EngineInitializer
@@ -262,7 +317,12 @@ _flutter.loader = null;
     _createScriptTag(url) {
       const scriptTag = document.createElement("script");
       scriptTag.type = "application/javascript";
-      scriptTag.src = url;
+      // Apply TrustedTypes validation, if available.
+      let trustedUrl = url;
+      if (this._ttPolicy != null) {
+        trustedUrl = this._ttPolicy.createScriptURL(url);
+      }
+      scriptTag.src = trustedUrl;
       return scriptTag;
     }
   }
@@ -285,9 +345,13 @@ _flutter.loader = null;
     async loadEntrypoint(options) {
       const { serviceWorker, ...entrypoint } = options || {};
 
+      // A Trusted Types policy that is going to be used by the loader.
+      const flutterTT = new FlutterTrustedTypesPolicy();
+
       // The FlutterServiceWorkerLoader instance could be injected as a dependency
       // (and dynamically imported from a module if not present).
       const serviceWorkerLoader = new FlutterServiceWorkerLoader();
+      serviceWorkerLoader.setTrustedTypesPolicy(flutterTT.policy);
       await serviceWorkerLoader.loadServiceWorker(serviceWorker).catch(e => {
         // Regardless of what happens with the injection of the SW, the show must go on
         console.warn("Exception while loading service worker:", e);
@@ -296,6 +360,7 @@ _flutter.loader = null;
       // The FlutterEntrypointLoader instance could be injected as a dependency
       // (and dynamically imported from a module if not present).
       const entrypointLoader = new FlutterEntrypointLoader();
+      entrypointLoader.setTrustedTypesPolicy(flutterTT.policy);
       // Install the `didCreateEngineInitializer` listener where Flutter web expects it to be.
       this.didCreateEngineInitializer =
         entrypointLoader.didCreateEngineInitializer.bind(entrypointLoader);

packages/flutter_tools/test/general.shard/web/bootstrap_test.dart

@@ -14,9 +14,11 @@ void main() {
       mapperUrl: 'mapper.js',
     );
     // require js source is interpolated correctly.
-    expect(result, contains('requireEl.src = "require.js";'));
+    expect(result, contains('"requireJs": "require.js"'));
+    expect(result, contains('requireEl.src = getTTScriptUrl("requireJs");'));
     // stack trace mapper source is interpolated correctly.
-    expect(result, contains('mapperEl.src = "mapper.js";'));
+    expect(result, contains('"mapper": "mapper.js"'));
+    expect(result, contains('mapperEl.src = getTTScriptUrl("mapper");'));
     // data-main is set to correct bootstrap module.
     expect(result, contains('requireEl.setAttribute("data-main", "main_module.bootstrap");'));
   });