Security-Fixes aus dem flutter-security Audit

CRIT:
- Cloud-Token jetzt in flutter_secure_storage (Keystore/Keychain) statt SharedPreferences, mit Migration alter Eintraege
- usesCleartextTraffic entfernt (kein HTTP-Klartext mehr)
HIGH:
- Path-Traversal gefixt: p.basename bei YouTube-Download, Navidrome-Download und Cloud-Auto-Sync
MED:
- allowBackup=false (kein Backup von Token-Daten)
- Navidrome-Salt kryptographisch sicher (Random.secure statt Timestamp)

lib/services/cloud_service.dart

@@ -1,6 +1,7 @@
 import 'dart:convert';
 import 'dart:io';
 import 'package:http/http.dart' as http;
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import '../config/app_config.dart';
 import '../services/melo_logger.dart';
@@ -19,6 +20,10 @@ class CloudService {
   String _user = '';
   String _token = '';
 
+  /// Token liegt verschlüsselt im Keychain/Keystore (flutter_secure_storage) —
+  /// nicht mehr im Klartext in SharedPreferences (Security-Audit CRIT-1).
+  static const _secure = FlutterSecureStorage();
+
   String get user => _user;
   String get token => _token;
   bool get istAngemeldet => _token.isNotEmpty;
@@ -48,12 +53,29 @@ class CloudService {
   }
 
   /// Stellt gespeicherten Token wieder her (Auto-Login nach App-Start).
+  /// Migriert einmalig alte SharedPreferences-Einträge in SecureStorage.
   Future<bool> restoreLogin() async {
     final prefs = await SharedPreferences.getInstance();
-    final t = prefs.getString('melo_cloud_token') ?? '';
+    var t = await _secure.read(key: 'melo_cloud_token') ?? '';
+    var u = await _secure.read(key: 'melo_cloud_user') ?? '';
+    // Migration alter Versionen (Token lag früher in SharedPreferences)
+    if (t.isEmpty) {
+      final altT = prefs.getString('melo_cloud_token') ?? '';
+      final altU = prefs.getString('melo_cloud_user') ?? '';
+      if (altT.isNotEmpty) {
+        t = altT;
+        u = altU;
+        await _secure.write(key: 'melo_cloud_token', value: t);
+        if (u.isNotEmpty) {
+          await _secure.write(key: 'melo_cloud_user', value: u);
+        }
+        await prefs.remove('melo_cloud_token');
+        await prefs.remove('melo_cloud_user');
+      }
+    }
     if (t.isEmpty) return false;
     _token = t;
-    _user = prefs.getString('melo_cloud_user') ?? '';
+    _user = u;
     MeloLogger.cloudToken = t;
     return true;
   }
@@ -62,15 +84,13 @@ class CloudService {
     _token = '';
     _user = '';
     MeloLogger.cloudToken = null;
-    final prefs = await SharedPreferences.getInstance();
-    await prefs.remove('melo_cloud_token');
-    await prefs.remove('melo_cloud_user');
+    await _secure.delete(key: 'melo_cloud_token');
+    await _secure.delete(key: 'melo_cloud_user');
   }
 
   Future<void> _speichereToken() async {
-    final prefs = await SharedPreferences.getInstance();
-    await prefs.setString('melo_cloud_token', _token);
-    await prefs.setString('melo_cloud_user', _user);
+    await _secure.write(key: 'melo_cloud_token', value: _token);
+    await _secure.write(key: 'melo_cloud_user', value: _user);
   }
 
   Map<String, String> get _authHeader => {

lib/services/download_service.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 import 'dart:io';
 import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
+import 'package:path/path.dart' as p;
 import 'package:path_provider/path_provider.dart';
 import '../models/song.dart';
 import '../database/db_helper.dart';
@@ -249,8 +250,8 @@ class DownloadService extends ChangeNotifier {
           : Directory('${(await getApplicationDocumentsDirectory()).path}/music');
       if (!await dir.exists()) await dir.create(recursive: true);
 
-      // Sicheren Dateinamen erstellen
-      final safeName = titel.replaceAll(RegExp(r'[^\w\s-]'), '').trim();
+      // Sicheren Dateinamen erstellen (p.basename verhindert Path-Traversal)
+      final safeName = p.basename(titel).replaceAll(RegExp(r'[^\w\s-]'), '').trim();
       final lokalerName = '${safeName.isEmpty ? "song" : safeName}.mp3';
       dateiPfad = '${dir.path}/$lokalerName';
 

lib/services/navidrome_service.dart

@@ -1,8 +1,10 @@
 import 'dart:convert';
 import 'dart:io';
+import 'dart:math';
 import 'package:flutter/foundation.dart';
 import 'package:crypto/crypto.dart';
 import 'package:http/http.dart' as http;
+import 'package:path/path.dart' as p;
 import 'package:path_provider/path_provider.dart';
 import 'package:flutter_secure_storage/flutter_secure_storage.dart';
 import '../models/song.dart';
@@ -81,7 +83,9 @@ class NavidromeService {
     _serverUrl = url.endsWith('/') ? url.substring(0, url.length - 1) : url;
     _user = user;
     _password = password;
-    _salt = DateTime.now().millisecondsSinceEpoch.toString();
+    // Kryptographisch sicherer Salt (vorher millisecondsSinceEpoch = vorhersagbar)
+    final rng = Random.secure();
+    _salt = base64Encode(List.generate(16, (_) => rng.nextInt(256)));
     _token = md5.convert(utf8.encode(_password + _salt)).toString();
   }
 
@@ -180,7 +184,7 @@ class NavidromeService {
       final musikDir = Directory('${dir.path}/music');
       if (!await musikDir.exists()) await musikDir.create(recursive: true);
 
-      final safeName = s.titel.replaceAll(RegExp(r'[^\w\s-]'), '').trim();
+      final safeName = p.basename(s.titel).replaceAll(RegExp(r'[^\w\s-]'), '').trim();
       final kurzId = s.id.length > 8 ? s.id.substring(0, 8) : s.id;
       final dateiName = '${safeName.isEmpty ? "song" : safeName}_$kurzId.mp3';
       final dateiPfad = '${musikDir.path}/$dateiName';