JWT- und Session-Validierung verbessert, UI aktualisiert

- JWT-Authentifizierung prüft nun, ob User aktiv und existent ist
- Session-Validierung beim App-Start via ValidateSessionAsync
- Ungültige Sessions werden entfernt, SignalR-Verbindung getrennt
- ApiService und IApiService um ValidateSessionAsync erweitert
- LoginViewModel nutzt Session-Check und behandelt SignalR-Fehler
- UI für eigene Phrasen auf <Border> mit Stil-Anpassung umgestellt

SlipItIn.Server/Program.cs

@@ -4,6 +4,7 @@ using Microsoft.IdentityModel.Tokens;
 using SlipItIn.Server.Data;
 using SlipItIn.Server.Hubs;
 using SlipItIn.Server.Services;
+using System.Security.Claims;
 using System.Text;
 
 var builder = WebApplication.CreateBuilder(args);
@@ -50,6 +51,24 @@ builder.Services
                     context.Token = accessToken;
                 }
                 return Task.CompletedTask;
+            },
+            OnTokenValidated = async context =>
+            {
+                var userIdClaim = context.Principal?.FindFirst(ClaimTypes.NameIdentifier)?.Value;
+                if (!int.TryParse(userIdClaim, out var userId))
+                {
+                    context.Fail("Invalid user claim.");
+                    return;
+                }
+
+                var dbFactory = context.HttpContext.RequestServices.GetRequiredService<IDbContextFactory<SlipItInDbContext>>();
+                await using var db = await dbFactory.CreateDbContextAsync();
+
+                var userExists = await db.Users.AnyAsync(u => u.Id == userId && u.IsActive);
+                if (!userExists)
+                {
+                    context.Fail("User no longer exists or is inactive.");
+                }
             }
         };
     });

SlipItIn/App.xaml.cs

@@ -35,17 +35,27 @@ public partial class App : Application
 			var authSession = ServiceHelper.GetRequiredService<IAuthSessionService>();
 			var signalR = ServiceHelper.GetRequiredService<ISignalRService>();
 			var gameStateService = ServiceHelper.GetRequiredService<IGameStateService>();
+			var apiService = ServiceHelper.GetRequiredService<IApiService>();
 
 			await authSession.InitializeAsync();
 			await gameStateService.InitializeAsync();
 
-			if (!string.IsNullOrWhiteSpace(authSession.AccessToken))
+			if (string.IsNullOrWhiteSpace(authSession.AccessToken))
+				return;
+
+			var isSessionValid = await apiService.ValidateSessionAsync();
+			if (!isSessionValid)
 			{
+				await authSession.ClearSessionAsync();
+				await gameStateService.ClearLocalGameDataAsync();
+				await signalR.DisconnectAsync();
+				return;
+			}
+
 			var connected = await signalR.ConnectAsync(authSession.AccessToken);
 			if (connected)
 				await gameStateService.ResyncAsync();
 		}
-		}
 		catch
 		{
 			// Start darf nicht abstürzen, wenn Session/Netzwerk fehlschlägt.

SlipItIn/Services/ApiService.cs

@@ -28,6 +28,23 @@ public class ApiService : IApiService
     public Task<AuthResponseDto> LoginAsync(LoginRequestDto request, CancellationToken cancellationToken = default)
         => PostAuthAsync("api/auth/login", request, cancellationToken);
 
+    public async Task<bool> ValidateSessionAsync(CancellationToken cancellationToken = default)
+    {
+        if (string.IsNullOrWhiteSpace(_authSession.AccessToken))
+            return false;
+
+        try
+        {
+            AttachAuthHeader();
+            var response = await _httpClient.GetAsync("api/auth/me", cancellationToken);
+            return response.IsSuccessStatusCode;
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
     public Task LogoutAsync() => _authSession.ClearSessionAsync();
 
     private async Task<AuthResponseDto> PostAuthAsync<TRequest>(string endpoint, TRequest request, CancellationToken cancellationToken)

SlipItIn/Services/Interfaces/IApiService.cs

@@ -6,5 +6,6 @@ public interface IApiService
 {
     Task<AuthResponseDto> RegisterAsync(RegisterRequestDto request, CancellationToken cancellationToken = default);
     Task<AuthResponseDto> LoginAsync(LoginRequestDto request, CancellationToken cancellationToken = default);
+    Task<bool> ValidateSessionAsync(CancellationToken cancellationToken = default);
     Task LogoutAsync();
 }

SlipItIn/ViewModels/LoginViewModel.cs

@@ -42,7 +42,11 @@ public partial class LoginViewModel : BaseViewModel
             });
 
             await _authSession.SetSessionAsync(response);
-            await _signalR.ConnectAsync(response.Token);
+
+            var connected = await _signalR.ConnectAsync(response.Token);
+            if (!connected)
+                throw new InvalidOperationException("Verbindung zum Spielserver fehlgeschlagen.");
+
             await _gameStateService.InitializeAsync();
             await Shell.Current.GoToAsync(nameof(LobbyPage));
         }, "Anmeldung läuft...");
@@ -51,11 +55,24 @@ public partial class LoginViewModel : BaseViewModel
     [RelayCommand]
     public async Task InitializeAsync()
     {
-        bool isAuthenticated = _authSession.IsAuthenticated;
+        if (!_authSession.IsAuthenticated)
+            return;
 
-        if (isAuthenticated)
+        var isSessionValid = await _apiService.ValidateSessionAsync();
+        if (!isSessionValid)
         {
+            await _authSession.ClearSessionAsync();
+            await _gameStateService.ClearLocalGameDataAsync();
+            await _signalR.DisconnectAsync();
+            return;
+        }
+
+        var token = _authSession.AccessToken;
+        if (string.IsNullOrWhiteSpace(token))
+            return;
+
+        var connected = await _signalR.ConnectAsync(token);
+        if (connected)
             await Shell.Current.GoToAsync(nameof(LobbyPage));
     }
 }
-}

SlipItIn/Views/GameBoardPage.xaml

@@ -20,7 +20,7 @@
                 <CollectionView ItemsSource="{Binding MyCards}">
                     <CollectionView.ItemTemplate>
                         <DataTemplate>
-                            <Frame Margin="0,4" Padding="10">
+                            <Border Margin="0,4" Padding="10" Stroke="LightGray" StrokeThickness="1" StrokeShape="RoundRectangle 10" BackgroundColor="White">
                                 <VerticalStackLayout>
                                     <Label Text="{Binding Text}" />
                                     <HorizontalStackLayout>
@@ -28,7 +28,7 @@
                                         <Button Text="Beschuldigen" Command="{Binding Source={RelativeSource AncestorType={x:Type ContentPage}}, Path=BindingContext.ChallengeCardCommand}" CommandParameter="{Binding .}" />
                                     </HorizontalStackLayout>
                                 </VerticalStackLayout>
-                            </Frame>
+                            </Border>
                         </DataTemplate>
                     </CollectionView.ItemTemplate>
                 </CollectionView>