Remove dependency in package:jwt_decoder

packages/google_sign_in/google_sign_in_web/example/integration_test/src/jwt_examples.dart

@@ -6,29 +6,41 @@ import 'package:google_identity_services_web/id.dart';
 
 import 'jsify_as.dart';
 
-/// A JWT token with null `credential`.
+/// A CredentialResponse with null `credential`.
 final CredentialResponse nullCredential =
     jsifyAs<CredentialResponse>(<String, Object?>{
   'credential': null,
 });
 
-/// A JWT token for predefined values.
+/// A CredentialResponse wrapping a known good JWT Token as its `credential`.
+final CredentialResponse goodCredential =
+    jsifyAs<CredentialResponse>(<String, Object?>{
+  'credential': goodJwtToken,
+});
+
+/// A JWT token with predefined values.
 ///
 /// 'email': 'adultman@example.com',
 /// 'sub': '123456',
 /// 'name': 'Vincent Adultman',
 /// 'picture': 'https://thispersondoesnotexist.com/image?x=.jpg',
 ///
 /// Signed with HS256 and the private key: 'symmetric-encryption-is-weak'
-final CredentialResponse okCredential =
-    jsifyAs<CredentialResponse>(<String, Object?>{
-  'credential':
-      'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJlbWFpbCI6ImFkdWx0bWFuQGV4YW1wbGUuY29tIiwic3ViIjoiMTIzNDU2IiwibmFtZSI6IlZpbmNlbnQgQWR1bHRtYW4iLCJwaWN0dXJlIjoiaHR0cHM6Ly90aGlzcGVyc29uZG9lc25vdGV4aXN0LmNvbS9pbWFnZT94PS5qcGcifQ.lqzULA_U3YzEl_-fL7YLU-kFXmdD2ttJLTv-UslaNQ4',
-});
+const String goodJwtToken =
+    'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.$goodPayload.lqzULA_U3YzEl_-fL7YLU-kFXmdD2ttJLTv-UslaNQ4';
+
+/// The payload of a JWT token that contains predefined values.
+///
+/// 'email': 'adultman@example.com',
+/// 'sub': '123456',
+/// 'name': 'Vincent Adultman',
+/// 'picture': 'https://thispersondoesnotexist.com/image?x=.jpg',
+const String goodPayload =
+    'eyJlbWFpbCI6ImFkdWx0bWFuQGV4YW1wbGUuY29tIiwic3ViIjoiMTIzNDU2IiwibmFtZSI6IlZpbmNlbnQgQWR1bHRtYW4iLCJwaWN0dXJlIjoiaHR0cHM6Ly90aGlzcGVyc29uZG9lc25vdGV4aXN0LmNvbS9pbWFnZT94PS5qcGcifQ';
 
-// More encrypted credential responses may be created on https://jwt.io.
+// More encrypted JWT Tokens may be created on https://jwt.io.
 //
-// First, decode the credential that's listed above, modify to your heart's
+// First, decode the `goodJwtToken` above, modify to your heart's
 // content, and add a new credential here.
 //
-// (It can also be done with `package:jose` and `dart:convert`.)
+// (New tokens can also be created with `package:jose` and `dart:convert`.)

packages/google_sign_in/google_sign_in_web/example/integration_test/utils_test.dart

@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:convert';
+
 import 'package:flutter_test/flutter_test.dart';
 import 'package:google_identity_services_web/id.dart';
 import 'package:google_identity_services_web/oauth2.dart';
@@ -18,6 +20,7 @@ void main() {
   group('gisResponsesToTokenData', () {
     testWidgets('null objects -> no problem', (_) async {
       final GoogleSignInTokenData tokens = gisResponsesToTokenData(null, null);
+
       expect(tokens.accessToken, isNull);
       expect(tokens.idToken, isNull);
       expect(tokens.serverAuthCode, isNull);
@@ -36,6 +39,7 @@ void main() {
       });
       final GoogleSignInTokenData tokens =
           gisResponsesToTokenData(credential, token);
+
       expect(tokens.accessToken, expectedAccessToken);
       expect(tokens.idToken, expectedIdToken);
       expect(tokens.serverAuthCode, isNull);
@@ -44,22 +48,21 @@ void main() {
 
   group('gisResponsesToUserData', () {
     testWidgets('happy case', (_) async {
-      final GoogleSignInUserData data = gisResponsesToUserData(okCredential)!;
+      final GoogleSignInUserData data = gisResponsesToUserData(goodCredential)!;
 
       expect(data.displayName, 'Vincent Adultman');
       expect(data.id, '123456');
       expect(data.email, 'adultman@example.com');
       expect(data.photoUrl, 'https://thispersondoesnotexist.com/image?x=.jpg');
-      expect(data.idToken, okCredential.credential);
+      expect(data.idToken, goodJwtToken);
     });
 
     testWidgets('null response -> null', (_) async {
       expect(gisResponsesToUserData(null), isNull);
     });
 
     testWidgets('null response.credential -> null', (_) async {
-      final CredentialResponse response = nullCredential;
-      expect(gisResponsesToUserData(response), isNull);
+      expect(gisResponsesToUserData(nullCredential), isNull);
     });
 
     testWidgets('invalid payload -> null', (_) async {
@@ -70,4 +73,101 @@ void main() {
       expect(gisResponsesToUserData(response), isNull);
     });
   });
+
+  group('getJwtTokenPayload', () {
+    testWidgets('happy case -> data', (_) async {
+      final Map<String, Object?>? data = getJwtTokenPayload(goodJwtToken);
+
+      expect(data, isNotNull);
+      expect(data, containsPair('name', 'Vincent Adultman'));
+      expect(data, containsPair('email', 'adultman@example.com'));
+      expect(data, containsPair('sub', '123456'));
+      expect(
+          data,
+          containsPair(
+            'picture',
+            'https://thispersondoesnotexist.com/image?x=.jpg',
+          ));
+    });
+
+    testWidgets('null Token -> null', (_) async {
+      final Map<String, Object?>? data = getJwtTokenPayload(null);
+
+      expect(data, isNull);
+    });
+
+    testWidgets('Token not matching the format -> null', (_) async {
+      final Map<String, Object?>? data = getJwtTokenPayload('1234.4321');
+
+      expect(data, isNull);
+    });
+
+    testWidgets('Bad token that matches the format -> null', (_) async {
+      final Map<String, Object?>? data = getJwtTokenPayload('1234.abcd.4321');
+
+      expect(data, isNull);
+    });
+  });
+
+  group('decodeJwtPayload', () {
+    testWidgets('Good payload -> data', (_) async {
+      final Map<String, Object?>? data = decodeJwtPayload(goodPayload);
+
+      expect(data, isNotNull);
+      expect(data, containsPair('name', 'Vincent Adultman'));
+      expect(data, containsPair('email', 'adultman@example.com'));
+      expect(data, containsPair('sub', '123456'));
+      expect(
+          data,
+          containsPair(
+            'picture',
+            'https://thispersondoesnotexist.com/image?x=.jpg',
+          ));
+    });
+
+    testWidgets('Proper JSON payload -> data', (_) async {
+      final String payload = base64.encode(utf8.encode('{"properJson": true}'));
+
+      final Map<String, Object?>? data = decodeJwtPayload(payload);
+
+      expect(data, isNotNull);
+      expect(data, containsPair('properJson', true));
+    });
+
+    testWidgets('Not-normalized base-64 payload -> data', (_) async {
+      // This is the payload generated by the "Proper JSON payload" test, but
+      // we remove the leading "=" symbols so it's length is not a multiple of 4
+      // anymore!
+      final String payload = 'eyJwcm9wZXJKc29uIjogdHJ1ZX0='.replaceAll('=', '');
+
+      final Map<String, Object?>? data = decodeJwtPayload(payload);
+
+      expect(data, isNotNull);
+      expect(data, containsPair('properJson', true));
+    });
+
+    testWidgets('Invalid JSON payload -> null', (_) async {
+      final String payload = base64.encode(utf8.encode('{properJson: false}'));
+
+      final Map<String, Object?>? data = decodeJwtPayload(payload);
+
+      expect(data, isNull);
+    });
+
+    testWidgets('Non JSON payload -> null', (_) async {
+      final String payload = base64.encode(utf8.encode('not-json'));
+
+      final Map<String, Object?>? data = decodeJwtPayload(payload);
+
+      expect(data, isNull);
+    });
+
+    testWidgets('Non base-64 payload -> null', (_) async {
+      const String payload = 'not-base-64-at-all';
+
+      final Map<String, Object?>? data = decodeJwtPayload(payload);
+
+      expect(data, isNull);
+    });
+  });
 }

packages/google_sign_in/google_sign_in_web/lib/src/utils.dart

@@ -2,10 +2,57 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:convert';
+
 import 'package:google_identity_services_web/id.dart';
 import 'package:google_identity_services_web/oauth2.dart';
 import 'package:google_sign_in_platform_interface/google_sign_in_platform_interface.dart';
-import 'package:jwt_decoder/jwt_decoder.dart' as jwt;
+
+/// A codec that can encode/decode JWT payloads.
+///
+/// See https://www.rfc-editor.org/rfc/rfc7519#section-3
+final Codec<Object?, String> jwtCodec = json.fuse(utf8).fuse(base64);
+
+/// A RegExp that can match, and extract parts from a JWT Token.
+///
+/// A JWT token consists of 3 base-64 encoded parts of data separated by periods:
+///
+///   header.payload.signature
+///
+/// More info: https://regexr.com/789qc
+final RegExp jwtTokenRegexp = RegExp(
+    r'^(?<header>[^\.\s]+)\.(?<payload>[^\.\s]+)\.(?<signature>[^\.\s]+)$');
+
+/// Decodes the `claims` of a JWT token and returns them as a Map.
+///
+/// JWT `claims` are stored as a JSON object in the `payload` part of the token.
+///
+/// (This method does not validate the signature of the token.)
+///
+/// See https://www.rfc-editor.org/rfc/rfc7519#section-3
+Map<String, Object?>? getJwtTokenPayload(String? token) {
+  if (token != null) {
+    final RegExpMatch? match = jwtTokenRegexp.firstMatch(token);
+    if (match != null) {
+      return decodeJwtPayload(match.namedGroup('payload'));
+    }
+  }
+
+  return null;
+}
+
+/// Decodes a JWT payload using the [jwtCodec].
+Map<String, Object?>? decodeJwtPayload(String? payload) {
+  try {
+    // Payload must be normalized before passing it to the codec
+    return (jwtCodec.decode(base64.normalize(payload!))
+            as Map<String, Object?>?)
+        ?.cast<String, Object?>();
+  } catch (_) {
+    // Do nothing, we always return null for any failure.
+  }
+  return null;
+}
 
 /// Converts a [CredentialResponse] into a [GoogleSignInUserData].
 ///
@@ -18,7 +65,7 @@ GoogleSignInUserData? gisResponsesToUserData(
   }
 
   final Map<String, Object?>? payload =
-      jwt.JwtDecoder.tryDecode(credentialResponse.credential!);
+      getJwtTokenPayload(credentialResponse.credential);
 
   if (payload == null) {
     return null;

packages/google_sign_in/google_sign_in_web/pubspec.yaml

@@ -26,7 +26,6 @@ dependencies:
   google_sign_in_platform_interface: ^2.2.0
   http: ^0.13.5
   js: ^0.6.3
-  jwt_decoder: ^2.0.1
 
 dev_dependencies:
   flutter_test: