fix: prevent sending expired tokens

Author: dshukertjr

packages/realtime_client/lib/src/realtime_client.dart

@@ -54,6 +54,7 @@ class RealtimeCloseEvent {
 }
 
 class RealtimeClient {
+  // This is named `accessTokenValue` in supabase-js
   String? accessToken;
   List<RealtimeChannel> channels = [];
   final String endPoint;
@@ -89,6 +90,8 @@ class RealtimeClient {
   };
   int longpollerTimeout = 20000;
   SocketStates? connState;
+  // This is called `accessToken` in realtime-js
+  Future<String> Function()? customAccessToken;
 
   /// Initializes the Socket
   ///
@@ -403,15 +406,42 @@ class RealtimeClient {
   /// Sets the JWT access token used for channel subscription authorization and Realtime RLS.
   ///
   /// `token` A JWT strings.
-  void setAuth(String? token) {
-    accessToken = token;
+  Future<void> setAuth(String? token) async {
+    final tokenToSend =
+        token ?? (await customAccessToken?.call()) ?? accessToken;
+
+    if (tokenToSend != null) {
+      Map<String, dynamic>? parsed;
+      try {
+        final decoded =
+            utf8.decode(base64Url.decode(tokenToSend.split('.')[1]));
+        parsed = json.decode(decoded);
+      } catch (e) {
+        // ignore parsing errors
+      }
+      if (parsed != null && parsed['exp'] != null) {
+        final now = (DateTime.now().millisecondsSinceEpoch / 1000).floor();
+        final valid = now - parsed['exp'] < 0;
+        if (!valid) {
+          log(
+            'auth',
+            'InvalidJWTToken: Invalid value for JWT claim "exp" with value ${parsed['exp']}',
+            null,
+            Level.FINE,
+          );
+          throw 'InvalidJWTToken: Invalid value for JWT claim "exp" with value ${parsed['exp']}';
+        }
+      }
+    }
+
+    accessToken = tokenToSend;
 
     for (final channel in channels) {
-      if (token != null) {
-        channel.updateJoinPayload({'access_token': token});
+      if (tokenToSend != null) {
+        channel.updateJoinPayload({'access_token': tokenToSend});
       }
       if (channel.joinedOnce && channel.isJoined) {
-        channel.push(ChannelEvents.accessToken, {'access_token': token});
+        channel.push(ChannelEvents.accessToken, {'access_token': tokenToSend});
       }
     }
   }

packages/realtime_client/pubspec.yaml

@@ -19,3 +19,4 @@ dev_dependencies:
   lints: ^3.0.0
   mocktail: ^1.0.0
   test: ^1.16.5
+  crypto: ^3.0.6

packages/realtime_client/test/socket_test.dart

@@ -1,6 +1,7 @@
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:crypto/crypto.dart';
 import 'package:mocktail/mocktail.dart';
 import 'package:realtime_client/realtime_client.dart';
 import 'package:realtime_client/src/constants.dart';
@@ -16,6 +17,31 @@ typedef WebSocketChannelClosure = WebSocketChannel Function(
   Map<String, String> headers,
 );
 
+/// Generate a JWT token for testing purposes
+///
+/// [exp] in seconds since Epoch
+String generateJwt([int? exp]) {
+  final header = {'alg': 'HS256', 'typ': 'JWT'};
+
+  final now = DateTime.now();
+  final expiry = exp ??
+      (now.add(Duration(hours: 1)).millisecondsSinceEpoch / 1000).floor();
+
+  final payload = {'exp': expiry};
+
+  final key = 'your-256-bit-secret';
+
+  final encodedHeader = base64Url.encode(utf8.encode(json.encode(header)));
+  final encodedPayload = base64Url.encode(utf8.encode(json.encode(payload)));
+
+  final signatureInput = '$encodedHeader.$encodedPayload';
+  final hmac = Hmac(sha256, utf8.encode(key));
+  final digest = hmac.convert(utf8.encode(signatureInput));
+  final signature = base64Url.encode(digest.bytes);
+
+  return '$encodedHeader.$encodedPayload.$signature';
+}
+
 void main() {
   const int int64MaxValue = 9223372036854775807;
 
@@ -427,8 +453,9 @@ void main() {
   });
 
   group('setAuth', () {
-    final updateJoinPayload = {'access_token': 'token123'};
-    final pushPayload = {'access_token': 'token123'};
+    final token = generateJwt();
+    final updateJoinPayload = {'access_token': token};
+    final pushPayload = {'access_token': token};
 
     test(
         "sets access token, updates channels' join payload, and pushes token to channels",
@@ -457,7 +484,9 @@ void main() {
       final channel1 = mockedSocket.channel(tTopic1);
       final channel2 = mockedSocket.channel(tTopic2);
 
-      mockedSocket.setAuth('token123');
+      mockedSocket.setAuth(token);
+
+      expect(mockedSocket.accessToken, token);
 
       verify(() => channel1.updateJoinPayload(updateJoinPayload)).called(1);
       verify(() => channel2.updateJoinPayload(updateJoinPayload)).called(1);
@@ -466,6 +495,62 @@ void main() {
       verify(() => channel2.push(ChannelEvents.accessToken, pushPayload))
           .called(1);
     });
+
+    test(
+        "sets access token, updates channels' join payload, and pushes token to channels if is not a jwt",
+        () {
+      final mockedChannel1 = MockChannel();
+      final mockedChannel2 = MockChannel();
+      final mockedChannel3 = MockChannel();
+
+      when(() => mockedChannel1.joinedOnce).thenReturn(true);
+      when(() => mockedChannel1.isJoined).thenReturn(true);
+      when(() => mockedChannel1.push(ChannelEvents.accessToken, any()))
+          .thenReturn(MockPush());
+
+      when(() => mockedChannel2.joinedOnce).thenReturn(false);
+      when(() => mockedChannel2.isJoined).thenReturn(false);
+      when(() => mockedChannel2.push(ChannelEvents.accessToken, any()))
+          .thenReturn(MockPush());
+
+      when(() => mockedChannel3.joinedOnce).thenReturn(true);
+      when(() => mockedChannel3.isJoined).thenReturn(true);
+      when(() => mockedChannel3.push(ChannelEvents.accessToken, any()))
+          .thenReturn(MockPush());
+
+      const tTopic1 = 'test-topic1';
+      const tTopic2 = 'test-topic2';
+      const tTopic3 = 'test-topic3';
+
+      final mockedSocket = SocketWithMockedChannel(socketEndpoint);
+      mockedSocket.mockedChannelLooker.addAll(<String, RealtimeChannel>{
+        tTopic1: mockedChannel1,
+        tTopic2: mockedChannel2,
+        tTopic3: mockedChannel3,
+      });
+
+      final channel1 = mockedSocket.channel(tTopic1);
+      final channel2 = mockedSocket.channel(tTopic2);
+      final channel3 = mockedSocket.channel(tTopic3);
+
+      const token = 'sb-key';
+      final pushPayload = {'access_token': token};
+      final updateJoinPayload = {'access_token': token};
+
+      mockedSocket.setAuth(token);
+
+      expect(mockedSocket.accessToken, token);
+
+      verify(() => channel1.updateJoinPayload(updateJoinPayload)).called(1);
+      verify(() => channel2.updateJoinPayload(updateJoinPayload)).called(1);
+      verify(() => channel3.updateJoinPayload(updateJoinPayload)).called(1);
+
+      verify(() => channel1.push(ChannelEvents.accessToken, pushPayload))
+          .called(1);
+      verifyNever(() => channel2.push(ChannelEvents.accessToken, pushPayload));
+      verify(() => channel3.push(ChannelEvents.accessToken, pushPayload))
+          .called(1);
+    });
   });
 
   group('sendHeartbeat', () {