---
type: Architecture
title: System Architecture & Security Overview
description: Technical architecture of SlipItIn, covering .NET Aspire orchestration, ASP.NET Core SignalR hub design, JWT authentication, and IDbContextFactory thread safety.
tags: [architecture, spire, signalr, jwt, efcore, security]
---

# System Architecture & Security Overview

**SlipItIn** is designed as a distributed, real-time application using modern .NET 10 architecture. This document details the orchestration model, backend service structure, security model, and concurrency safeguards.

The architectural foundation [orchestrates services with](/openwiki/operations/runbook.md) .NET Aspire, while [enforcing security & privacy on](/openwiki/domain/game-mechanics.md) domain entities and [serving real-time hub endpoints for](/openwiki/workflows/slip-and-challenge.md) all active game sessions. Source code structure for all architectural components can be found in the [Source Code Map](/openwiki/source-map.md).

---

## 1. .NET Aspire Orchestration Model

The solution uses **.NET Aspire** to orchestrate application resources, services, and infrastructure dependencies:

- **AppHost (`SlipItIn.AppHost/AppHost.cs`)**:
  - Provisions a PostgreSQL database container (`AddPostgres("pgsql").AddDatabase("postgresdb")`).
  - Registers the backend project `SlipItIn.Server` with a direct reference to the PostgreSQL resource.
  - Registers the client project `SlipItIn` with service discovery references to `SlipItIn.Server`.
- **Service Defaults (`SlipItIn.ServiceDefaults/Extensions.cs`)**:
  - Configures **OpenTelemetry** logging, metrics (AspNetCore, HttpClient, Runtime), and tracing.
  - Exposes standardized health check endpoints (`/health` and `/alive`).
  - Enforces automatic HTTP resilience (`AddStandardResilienceHandler()`) and service discovery.

---

## 2. ASP.NET Core Backend Architecture (`SlipItIn.Server`)

The backend is an ASP.NET Core Web API & SignalR application providing REST endpoints for user management and real-time WebSockets for game state synchronization.

### Key Components

1. **`Program.cs`**:
   - Registers `AddServiceDefaults()`, `AddNpgsqlDataSource("postgresdb")`, and `AddDbContextFactory<SlipItInDbContext>()`.
   - Configures JWT Bearer authentication with custom `OnMessageReceived` token resolution for SignalR.
   - Automatically executes database migrations (`db.Database.Migrate()`) at startup.
2. **`AuthController.cs`**:
   - Manages user registration (`/api/auth/register`) and authentication (`/api/auth/login`).
   - Uses `BCrypt.Net` for secure password hashing.
   - Issues JWT tokens signed with `Jwt:Key`, containing `ClaimTypes.NameIdentifier`, `ClaimTypes.Name`, and `ClaimTypes.Email`.
3. **`GameHub.cs`**:
   - Real-time SignalR hub mapped to `/hubs/game`.
   - Annotated with `[Authorize]` to reject unauthenticated WebSocket connections.
   - Extracts and verifies user claims, delegating state mutations to `IGameService`.
4. **`GameService.cs`**:
   - Implements core business logic: game creation, player joins, card dealing, slip submission, challenge creation, and resolution.

---

## 3. JWT Authentication & SignalR Security

In real-time SignalR applications, clients can attempt to spoof player identifiers. SlipItIn eliminates this vulnerability through strict claim validation and authorization checks.

### SignalR Token Extraction
Since WebSockets cannot pass custom HTTP headers during connection handshakes, `Program.cs` configures JWT query parameter extraction:

```csharp
options.Events = new JwtBearerEvents
{
    OnMessageReceived = context =>
    {
        var accessToken = context.Request.Query["access_token"];
        var path = context.HttpContext.Request.Path;
        if (!string.IsNullOrEmpty(accessToken) && path.StartsWithSegments("/hubs"))
        {
            context.Token = accessToken;
        }
        return Task.CompletedTask;
    }
};
```

### Claims Validation & Access Control in `GameHub.cs`
Inside `GameHub.cs`, claims are extracted directly from the authenticated SignalR context:

* `GetAuthenticatedUserId()`: Extracts `Context.User?.FindFirst(ClaimTypes.NameIdentifier)`. Throws `UnauthorizedAccessException` if missing or invalid.
* `ValidatePlayerAccessAsync(playerId, authUserId)`: Queries the database to verify that `Player.UserId` matches the authenticated user ID.
* `ValidateHostAccessAsync(gameId, authUserId)`: Verifies that `Game.HostId` matches the authenticated user ID before allowing lobby configuration or game start.
* `ValidateChallengeTargetAccessAsync(challengeId, authUserId)`: Ensures only the accused player can resolve a challenge against them.

### Real-Time Auth Flow Diagram

```mermaid
sequenceDiagram
    autonumber
    actor Client as MAUI Client
    participant Auth as AuthController
    participant Hub as GameHub
    participant Service as GameService
    participant DB as SlipItInDbContext

    Client->>Auth: POST /api/auth/login
    Auth->>DB: Query User & Verify BCrypt Hash
    Auth-->>Client: 200 OK (JWT Access Token)
    Client->>Hub: Connect WebSocket /hubs/game?access_token=JWT
    Hub->>Hub: Validate JWT Signature & Claims
    Client->>Hub: JoinLobby(lobbyCode)
    Hub->>Hub: GetAuthenticatedUserId()
    Hub->>Service: JoinGameAsync(lobbyCode, userId, connectionId)
    Service->>DB: Create IDbContext Session & Save Player
    Hub-->>Client: Broadcast "PlayerJoined" (GameStateDto)
```

---

## 4. Concurrency Safety: `IDbContextFactory`

SignalR hubs process concurrent requests from multiple clients over persistent connections. Using a standard Scoped `DbContext` in SignalR leads to thread conflict exceptions (`InvalidOperationException: A second operation was started on this context instance before a previous operation completed`).

### Resolution via `IDbContextFactory`
SlipItIn solves this by registering EF Core with `AddDbContextFactory<SlipItInDbContext>`:

* Every method call inside `GameHub.cs`, `AuthController.cs`, and `GameService.cs` creates a short-lived, isolated `DbContext` session using `using var context = _contextFactory.CreateDbContext()`.
* **Benefit**: Thread-safe database operations across simultaneous challenges, card transfers, and lobby updates without race conditions.

---

## 5. Data Privacy Isolation Model

To prevent players from inspecting opponent cards via network trace analysis, SlipItIn strictly separates public and private data DTOs:

* **`GameStateDto` (Public)**: Broadcast to all players in a lobby. Contains public game information (`GameId`, `LobbyCode`, `Status`, `CurrentRound`, `RoundTimeRemaining`) and player summaries (`PlayerId`, `Username`, `Score`, `IsReady`, `CardCount`). **Crucially, no card text is included.**
* **`PlayerHandDto` (Private)**: Direct unicast message sent *only* to the specific player's SignalR `ConnectionId`. Contains card text (`CardId`, `PhraseId`, `Text`, `IsUsed`).

This architecture guarantees that players cannot see opponent phrase cards, even if they inspect raw WebSocket packets.