fix(app): harden Hivemind control-plane trust boundaries (#8)

Bound and nonce-bind control responses, reject redirects, and pin session tunnel coordinates so control-plane compromise cannot redirect VPN traffic.

lib/logic/hivemind_service.dart

@@ -13,6 +13,7 @@ class HivemindService {
 
   static const _ua = 'Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 '
       '(KHTML, like Gecko) Chrome/131.0.0.0 Mobile Safari/537.36';
+  static const int _maxControlResponseBytes = 256 * 1024;
   static const _pollBackoff = <Duration>[
     Duration(seconds: 1),
     Duration(seconds: 2),
@@ -24,10 +25,61 @@ class HivemindService {
     Uri uri, {
     Duration timeout = const Duration(seconds: 5),
   }) {
-    return http.get(uri, headers: {'User-Agent': _ua}).timeout(timeout);
+    return controlGet(uri, timeout: timeout);
   }
 
-  static void cancel() => _currentCallId++;
+  static Future<http.Response> controlGet(
+    Uri uri, {
+    Duration timeout = const Duration(seconds: 5),
+  }) async {
+    final client = http.Client();
+    final request = http.Request('GET', uri)
+      ..headers['User-Agent'] = _ua
+      ..followRedirects = false;
+
+    Future<http.Response> read() async {
+      final streamed = await client.send(request);
+      final declaredLength = streamed.contentLength;
+      if (declaredLength != null && declaredLength > _maxControlResponseBytes) {
+        throw const FormatException('Control response is too large.');
+      }
+
+      final bytes = <int>[];
+      await for (final chunk in streamed.stream) {
+        if (bytes.length + chunk.length > _maxControlResponseBytes) {
+          throw const FormatException('Control response is too large.');
+        }
+        bytes.addAll(chunk);
+      }
+
+      return http.Response.bytes(
+        bytes,
+        streamed.statusCode,
+        headers: streamed.headers,
+        isRedirect: streamed.isRedirect,
+        persistentConnection: streamed.persistentConnection,
+        reasonPhrase: streamed.reasonPhrase,
+        request: request,
+      );
+    }
+
+    try {
+      return await read().timeout(
+        timeout,
+        onTimeout: () {
+          client.close();
+          throw TimeoutException('Control request timed out.', timeout);
+        },
+      );
+    } finally {
+      client.close();
+    }
+  }
+
+  static void cancel() {
+    _currentCallId++;
+    _expectedNonce = null;
+  }
 
   static void setExpectedNonce(String nonce) {
     _expectedNonce = nonce;
@@ -37,13 +89,19 @@ class HivemindService {
     void Function(int attempt, int total)? onAttempt,
     bool skipAdBypass = false,
   }) async {
-    final deviceId = await CryptoService.getDeviceId();
+    // Capture the generation before the first await. Otherwise a disconnect
+    // that lands while secure storage is resolving the device ID can be lost
+    // and the cancelled call can resume network work with a fresh generation.
     final callId = ++_currentCallId;
+    final deviceId = await CryptoService.getDeviceId();
+    _throwIfCancelled(callId);
+
     final nonce = _newNonce();
     _expectedNonce = nonce;
 
     if (!skipAdBypass) {
       await _runConfiguredBypass(deviceId, nonce);
+      _throwIfCancelled(callId);
     }
 
     const maxAttempts = 5;
@@ -53,6 +111,7 @@ class HivemindService {
 
       try {
         final session = await _fetchActiveSession(deviceId, nonce);
+        _throwIfCancelled(callId);
         if (session != null) {
           _expectedNonce = null;
           return session.toVlessUrl();
@@ -73,7 +132,7 @@ class HivemindService {
 
   static Future<bool> checkHealth() async {
     try {
-      final response = await directGet(
+      final response = await controlGet(
         _publicUrl('/health'),
         timeout: const Duration(seconds: 3),
       );
@@ -109,15 +168,15 @@ class HivemindService {
     final statusUri = _publicUrl('/session/status').replace(
       queryParameters: {'device_id': deviceId},
     );
-    final response = await directGet(statusUri);
+    final response = await controlGet(statusUri);
     if (response.statusCode != 200) return null;
 
     final decoded = jsonDecode(response.body);
     if (decoded is! Map<String, dynamic>) return null;
 
     final serverNonce = decoded['nonce'];
-    if (_expectedNonce != null &&
+    if (_expectedNonce != nonce ||
-        serverNonce is String &&
+        serverNonce is! String ||
         serverNonce != nonce) {
       return null;
     }
@@ -141,6 +200,13 @@ class HivemindService {
 }
 
 class _HivemindSessionConfig {
+  static final RegExp _uuidPattern = RegExp(
+    r'^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$',
+    caseSensitive: false,
+  );
+  static final RegExp _shortIdPattern =
+      RegExp(r'^[0-9a-f]{0,16}$', caseSensitive: false);
+
   final String uuid;
   final String host;
   final int port;
@@ -162,50 +228,174 @@ class _HivemindSessionConfig {
   });
 
   factory _HivemindSessionConfig.fromJson(Map<String, dynamic> json) {
-    final uuid = _requiredString(json, 'vless_uuid');
+    final uuid = _requiredString(json, 'vless_uuid', maxLength: 64);
-    final host = _stringOr(json['vless_ip'], AppConfig.serverIp);
+    if (!_uuidPattern.hasMatch(uuid)) {
-    final port = _portOr(json['vless_port'], 443);
+      throw const FormatException('Invalid VLESS UUID');
-    final sni = _requiredString(json, 'reality_sni');
+    }
+
+    // The API may rotate credentials and Reality parameters, but it must never
+    // choose the tunnel destination. Keep that trust anchor compiled into the
+    // app so an API/domain compromise can cause denial of service, not redirect
+    // VPN traffic to an attacker-controlled server.
+    final pinnedHost = _validatedPublicIp(AppConfig.serverIp, 'serverIp');
+    final advertisedHost = json['vless_ip'];
+    if (advertisedHost != null) {
+      if (advertisedHost is! String || advertisedHost.trim() != pinnedHost) {
+        throw const FormatException(
+          'Session VLESS host does not match compiled server pin',
+        );
+      }
+    }
+    final host = pinnedHost;
+
+    final advertisedPort = json['vless_port'];
+    if (advertisedPort != null &&
+        (advertisedPort is! num || advertisedPort.toInt() != 443)) {
+      throw const FormatException('Session VLESS port does not match compiled pin');
+    }
+    const port = 443;
+    final sni = _validatedHost(
+      _requiredString(json, 'reality_sni', maxLength: 253),
+      'reality_sni',
+    );
+    final publicKey = _requiredString(json, 'reality_pbk', maxLength: 128);
+    final shortId = _stringOr(json['reality_sid'], '').trim();
+    if (!_shortIdPattern.hasMatch(shortId)) {
+      throw const FormatException('Invalid Reality short ID');
+    }
+
+    final fingerprint =
+        _boundedString(json['reality_fp'], AppConfig.realityFp, 32, 'reality_fp');
+    final path =
+        _boundedString(json['xhttp_path'], AppConfig.vlessPath, 2048, 'xhttp_path');
+    if (!path.startsWith('/')) {
+      throw const FormatException('Invalid XHTTP path');
+    }
 
     return _HivemindSessionConfig(
       uuid: uuid,
       host: host,
       port: port,
-      publicKey: _stringOr(json['reality_pbk'], ''),
+      publicKey: publicKey,
-      shortId: _stringOr(json['reality_sid'], ''),
+      shortId: shortId,
       sni: sni,
-      fingerprint: _stringOr(json['reality_fp'], AppConfig.realityFp),
+      fingerprint: fingerprint,
-      path: _stringOr(json['xhttp_path'], AppConfig.vlessPath),
+      path: path,
     );
   }
 
   String toVlessUrl() {
-    return 'vless://$uuid@$host:$port'
+    return Uri(
-        '?security=${AppConfig.vlessSecurity}'
+      scheme: 'vless',
-        '&type=${AppConfig.vlessType}'
+      userInfo: uuid,
-        '&path=$path'
+      host: host,
-        '&pbk=${Uri.encodeComponent(publicKey)}'
+      port: port,
-        '&sni=${Uri.encodeComponent(sni)}'
+      queryParameters: <String, String>{
-        '&sid=${Uri.encodeComponent(shortId)}'
+        'security': AppConfig.vlessSecurity,
-        '&fp=${Uri.encodeComponent(fingerprint)}'
+        'type': AppConfig.vlessType,
-        '#Revolt VPN';
+        'path': path,
+        'pbk': publicKey,
+        'sni': sni,
+        'sid': shortId,
+        'fp': fingerprint,
+      },
+      fragment: 'Revolt VPN',
+    ).toString();
   }
 
-  static String _requiredString(Map<String, dynamic> json, String key) {
+  static String _requiredString(
+    Map<String, dynamic> json,
+    String key, {
+    int maxLength = 4096,
+  }) {
     final value = json[key];
-    if (value is String && value.trim().isNotEmpty) return value.trim();
+    if (value is! String) {
-    throw FormatException('Missing required session field: $key');
+      throw FormatException('Missing required session field: $key');
+    }
+    final trimmed = value.trim();
+    if (trimmed.isEmpty || trimmed.length > maxLength) {
+      throw FormatException('Invalid session field: $key');
+    }
+    return trimmed;
   }
 
   static String _stringOr(Object? value, String fallback) {
-    return value is String && value.isNotEmpty ? value : fallback;
+    return value is String && value.trim().isNotEmpty ? value.trim() : fallback;
   }
 
-  static int _portOr(Object? value, int fallback) {
+  static String _boundedString(
-    final parsed = value is num ? value.toInt() : fallback;
+    Object? value,
-    if (parsed <= 0 || parsed > 65535) {
+    String fallback,
-      throw const FormatException('Invalid VLESS port');
+    int maxLength,
+    String field,
+  ) {
+    final result = _stringOr(value, fallback);
+    if (result.isEmpty || result.length > maxLength) {
+      throw FormatException('Invalid session field: $field');
     }
-    return parsed;
+    return result;
+  }
+
+  static String _validatedHost(String input, String field) {
+    final value = input.trim();
+    if (value.isEmpty ||
+        value.length > 253 ||
+        value.contains(RegExp(r'[\s/@?#]'))) {
+      throw FormatException('Invalid session host: $field');
+    }
+    try {
+      final probe = Uri(scheme: 'https', host: value);
+      if (probe.host.isEmpty) {
+        throw FormatException('Invalid session host: $field');
+      }
+    } on FormatException {
+      throw FormatException('Invalid session host: $field');
+    }
+    return value;
+  }
+
+  static String _validatedPublicIp(String input, String field) {
+    final value = input.trim().toLowerCase();
+    if (_isPublicIpv4(value) || _isPublicIpv6(value)) return value;
+    throw FormatException('Invalid public IP pin: $field');
+  }
+
+  static bool _isPublicIpv4(String value) {
+    final parts = value.split('.');
+    if (parts.length != 4) return false;
+    final octets = <int>[];
+    for (final part in parts) {
+      if (part.isEmpty || (part.length > 1 && part.startsWith('0'))) return false;
+      final parsed = int.tryParse(part);
+      if (parsed == null || parsed < 0 || parsed > 255) return false;
+      octets.add(parsed);
+    }
+    final a = octets[0];
+    final b = octets[1];
+    if (a == 0 || a == 10 || a == 127 || a >= 224) return false;
+    if (a == 100 && b >= 64 && b <= 127) return false;
+    if (a == 169 && b == 254) return false;
+    if (a == 172 && b >= 16 && b <= 31) return false;
+    if (a == 192 && b == 168) return false;
+    if (a == 192 && b == 0 && octets[2] == 2) return false;
+    if (a == 198 && b == 51 && octets[2] == 100) return false;
+    if (a == 203 && b == 0 && octets[2] == 113) return false;
+    return true;
+  }
+
+  static bool _isPublicIpv6(String value) {
+    if (!value.contains(':') || value.contains('.')) return false;
+    try {
+      final parsed = Uri.parse('https://[$value]/');
+      if (parsed.host.isEmpty || !parsed.host.contains(':')) return false;
+    } on FormatException {
+      return false;
+    }
+    if (value == '::' || value == '::1') return false;
+    if (value.startsWith('fc') || value.startsWith('fd')) return false;
+    if (value.startsWith('fe8') || value.startsWith('fe9') || value.startsWith('fea') || value.startsWith('feb')) return false;
+    if (value.startsWith('ff')) return false;
+    if (value.startsWith('2001:db8:') || value == '2001:db8::') return false;
+    return true;
   }
 }