fix: validate devtoolsOptionsUri in extensionEnabledState handler

packages/devtools_shared/CHANGELOG.md

@@ -3,6 +3,11 @@ Copyright 2025 The Flutter Authors
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file or at https://developers.google.com/open-source/licenses/bsd.
 -->
+# 13.0.2
+* Validate the `devtoolsOptionsUri` query parameter in the extension enabled
+  state handler so it must be a `file:` URI named `devtools_options.yaml`,
+  preventing arbitrary file writes by the DevTools server process.
+
 # 13.0.1
 * Handle null values for `FlutterStore.flutterClientId`.
 

packages/devtools_shared/lib/src/server/handlers/_devtools_extensions.dart

@@ -80,6 +80,27 @@ extension _ExtensionsApiHandler on Never {
     final devtoolsOptionsFileUriString =
         queryParams[ExtensionsApi.devtoolsOptionsUriPropertyName]!;
     final devtoolsOptionsFileUri = Uri.parse(devtoolsOptionsFileUriString);
+
+    // Validate that the URI is a local file URI whose file name is exactly
+    // 'devtools_options.yaml'. Accepting arbitrary URIs from the query string
+    // would allow an untrusted caller to create or overwrite any file writable
+    // by the DevTools server process. Resolving the name through
+    // `Uri.toFilePath()` + `p.basename` handles both '/' and '\' path
+    // separators, so the check holds for Windows file URIs as well. Requiring
+    // an empty host rejects UNC paths (e.g. `file://server/share/...`) and
+    // keeps `toFilePath()` from throwing on a non-local authority.
+    final isFileUri = devtoolsOptionsFileUri.scheme == 'file' &&
+        devtoolsOptionsFileUri.host.isEmpty;
+    final fileName = isFileUri
+        ? p.basename(devtoolsOptionsFileUri.toFilePath())
+        : '';
+    if (!isFileUri || fileName != 'devtools_options.yaml') {
+      return api.badRequest(
+        'Invalid devtoolsOptionsUri: must be a file: URI named '
+        "'devtools_options.yaml'.",
+      );
+    }
+
     final extensionName = queryParams[ExtensionsApi.extensionNamePropertyName]!;
 
     final activate = queryParams[ExtensionsApi.enabledStatePropertyName];

packages/devtools_shared/lib/src/server/server_api.dart

@@ -11,6 +11,7 @@ import 'dart:io';
 import 'package:collection/collection.dart';
 import 'package:dtd/dtd.dart';
 import 'package:meta/meta.dart';
+import 'package:path/path.dart' as p;
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:vm_service/vm_service.dart';
 

packages/devtools_shared/pubspec.yaml

@@ -4,7 +4,7 @@
 name: devtools_shared
 description: Package of shared Dart structures between devtools_app, dds, and other tools.
 
-version: 13.0.1
+version: 13.0.2
 
 repository: https://github.com/flutter/devtools/tree/master/packages/devtools_shared
 

packages/devtools_shared/test/server/devtools_extensions_api_test.dart

@@ -49,10 +49,9 @@ void main() {
       includeDependenciesWithExtensions: includeDependenciesWithExtensions,
       includeBadExtension: includeBadExtension,
     );
-    await testDtdConnection!.setIDEWorkspaceRoots(
-      dtd!.info!.secret!,
-      [extensionTestManager.packagesRootUri],
-    );
+    await testDtdConnection!.setIDEWorkspaceRoots(dtd!.info!.secret!, [
+      extensionTestManager.packagesRootUri,
+    ]);
   }
 
   Future<Response> serveExtensions(
@@ -66,8 +65,9 @@ void main() {
         host: 'localhost',
         path: ExtensionsApi.apiServeAvailableExtensions,
         queryParameters: {
-          ExtensionsApi.packageRootUriPropertyName:
-              includeRuntimeRoot ? extensionTestManager.runtimeAppRoot : null,
+          ExtensionsApi.packageRootUriPropertyName: includeRuntimeRoot
+              ? extensionTestManager.runtimeAppRoot
+              : null,
         },
       ),
     );
@@ -128,9 +128,7 @@ void main() {
     test(
       'fails when an exception is thrown and there are no valid extensions',
       () async {
-        await initializeTestDirectory(
-          includeDependenciesWithExtensions: false,
-        );
+        await initializeTestDirectory(includeDependenciesWithExtensions: false);
         extensionsManager = _TestExtensionsManager();
         final response = await serveExtensions(extensionsManager);
         expect(response.statusCode, HttpStatus.internalServerError);
@@ -159,6 +157,7 @@ void main() {
     Future<Response> sendEnabledStateRequest({
       required String extensionName,
       bool? enable,
+      String? optionsUriOverride,
     }) async {
       final request = Request(
         'post',
@@ -167,7 +166,8 @@ void main() {
           host: 'localhost',
           path: ExtensionsApi.apiExtensionEnabledState,
           queryParameters: {
-            ExtensionsApi.devtoolsOptionsUriPropertyName: optionsFileUriString,
+            ExtensionsApi.devtoolsOptionsUriPropertyName:
+                optionsUriOverride ?? optionsFileUriString,
             ExtensionsApi.extensionNamePropertyName: extensionName,
             if (enable != null)
               ExtensionsApi.enabledStatePropertyName: enable.toString(),
@@ -181,6 +181,37 @@ void main() {
       );
     }
 
+    test('rejects a devtoolsOptionsUri that is not a devtools_options.yaml '
+        'file', () async {
+      await serveExtensions(extensionsManager);
+      const invalidUris = [
+        // Wrong file name.
+        'file:///tmp/evil.txt',
+        'file:///tmp/devtools_options.yaml.bak',
+        // Non-file scheme.
+        'https://evil.example.com/devtools_options.yaml',
+        // UNC path / non-empty host.
+        'file://remotehost/share/devtools_options.yaml',
+      ];
+      for (final invalidUri in invalidUris) {
+        final response = await sendEnabledStateRequest(
+          extensionName: 'drift',
+          optionsUriOverride: invalidUri,
+        );
+        expect(
+          response.statusCode,
+          HttpStatus.badRequest,
+          reason: 'expected $invalidUri to be rejected',
+        );
+      }
+    });
+
+    test('accepts a valid devtools_options.yaml file: URI', () async {
+      await serveExtensions(extensionsManager);
+      final response = await sendEnabledStateRequest(extensionName: 'drift');
+      expect(response.statusCode, HttpStatus.ok);
+    });
+
     test('options file does not exist until first acesss', () async {
       await serveExtensions(extensionsManager);
       expect(optionsFile.existsSync(), isFalse);
@@ -202,16 +233,16 @@ void main() {
         ExtensionEnabledState.none.name,
       );
 
-// TODO(kenz): why is existsSync() returning false when I can verify the file
-// contents on the file system at [optionsFileUriString]?
-//       expect(optionsFile.existsSync(), isTrue);
-//       expect(
-//         optionsFile.readAsStringSync(),
-//         '''
-// description: This file stores settings for Dart & Flutter DevTools.
-// documentation: https://docs.flutter.dev/tools/devtools/extensions#configure-extension-enablement-states
-// extensions:''',
-//       );
+      // TODO(kenz): why is existsSync() returning false when I can verify the file
+      // contents on the file system at [optionsFileUriString]?
+      //       expect(optionsFile.existsSync(), isTrue);
+      //       expect(
+      //         optionsFile.readAsStringSync(),
+      //         '''
+      // description: This file stores settings for Dart & Flutter DevTools.
+      // documentation: https://docs.flutter.dev/tools/devtools/extensions#configure-extension-enablement-states
+      // extensions:''',
+      //       );
 
       response = await sendEnabledStateRequest(
         extensionName: 'drift',
@@ -233,16 +264,16 @@ void main() {
         ExtensionEnabledState.disabled.name,
       );
 
-//       expect(optionsFile.existsSync(), isTrue);
-//       expect(
-//         optionsFile.readAsStringSync(),
-//         '''
-// description: This file stores settings for Dart & Flutter DevTools.
-// documentation: https://docs.flutter.dev/tools/devtools/extensions#configure-extension-enablement-states
-// extensions:
-//   - drift: true
-//   - provider: false''',
-//       );
+      //       expect(optionsFile.existsSync(), isTrue);
+      //       expect(
+      //         optionsFile.readAsStringSync(),
+      //         '''
+      // description: This file stores settings for Dart & Flutter DevTools.
+      // documentation: https://docs.flutter.dev/tools/devtools/extensions#configure-extension-enablement-states
+      // extensions:
+      //   - drift: true
+      //   - provider: false''',
+      //       );
     });
   });
 }