# Day 4 Implementation Summary: JWT Service + Password Hashing + Authentication Middleware

## Date: 2025-11-03

---

## Overview

Successfully implemented **Day 4** objectives:
- ✅ JWT Token Generation Service
- ✅ BCrypt Password Hashing Service
- ✅ Real JWT Authentication Middleware
- ✅ Protected Endpoints with [Authorize]
- ✅ Replaced all dummy tokens with real JWT
- ✅ Compilation Successful

---

## Files Created

### 1. Application Layer Interfaces

**`src/Modules/Identity/ColaFlow.Modules.Identity.Application/Services/IJwtService.cs`**
```csharp
public interface IJwtService
{
    string GenerateToken(User user, Tenant tenant);
    Task<string> GenerateRefreshTokenAsync(User user, CancellationToken cancellationToken = default);
}
```

**`src/Modules/Identity/ColaFlow.Modules.Identity.Application/Services/IPasswordHasher.cs`**
```csharp
public interface IPasswordHasher
{
    string HashPassword(string password);
    bool VerifyPassword(string password, string hashedPassword);
}
```

### 2. Infrastructure Layer Implementations

**`src/Modules/Identity/ColaFlow.Modules.Identity.Infrastructure/Services/JwtService.cs`**
- Uses `System.IdentityModel.Tokens.Jwt`
- Generates JWT with tenant and user claims
- Configurable via appsettings (Issuer, Audience, SecretKey, Expiration)
- Token includes: user_id, tenant_id, tenant_slug, email, full_name, auth_provider, role

**`src/Modules/Identity/ColaFlow.Modules.Identity.Infrastructure/Services/PasswordHasher.cs`**
- Uses `BCrypt.Net-Next`
- Work factor: 12 (balance between security and performance)
- HashPassword() - hashes plain text passwords
- VerifyPassword() - verifies password against hash

---

## Files Modified

### 1. Dependency Injection

**`src/Modules/Identity/ColaFlow.Modules.Identity.Infrastructure/DependencyInjection.cs`**
```csharp
// Added services
services.AddScoped<IJwtService, JwtService>();
services.AddScoped<IPasswordHasher, PasswordHasher>();
```

### 2. Command Handlers

**`src/Modules/Identity/ColaFlow.Modules.Identity.Application/Commands/RegisterTenant/RegisterTenantCommandHandler.cs`**
- Removed dummy token generation
- Now uses `IPasswordHasher` to hash admin password
- Now uses `IJwtService` to generate real JWT token

**`src/Modules/Identity/ColaFlow.Modules.Identity.Application/Commands/Login/LoginCommandHandler.cs`**
- Removed dummy token generation
- Now uses `IPasswordHasher.VerifyPassword()` to validate password
- Now uses `IJwtService.GenerateToken()` to generate real JWT token

### 3. API Configuration

**`src/ColaFlow.API/Program.cs`**
- Added JWT Bearer authentication configuration
- Added authentication and authorization middleware
- Token validation parameters: ValidateIssuer, ValidateAudience, ValidateLifetime, ValidateIssuerSigningKey

**`src/ColaFlow.API/appsettings.Development.json`**
```json
{
  "Jwt": {
    "SecretKey": "your-super-secret-key-min-32-characters-long-12345",
    "Issuer": "ColaFlow.API",
    "Audience": "ColaFlow.Web",
    "ExpirationMinutes": "60"
  }
}
```

**`src/ColaFlow.API/Controllers/AuthController.cs`**
- Added `[Authorize]` attribute to `/api/auth/me` endpoint
- Endpoint now extracts and returns JWT claims (user_id, tenant_id, email, etc.)

---

## NuGet Packages Added

| Package | Version | Project | Purpose |
|---------|---------|---------|---------|
| Microsoft.IdentityModel.Tokens | 8.14.0 | Identity.Infrastructure | JWT token validation |
| System.IdentityModel.Tokens.Jwt | 8.14.0 | Identity.Infrastructure | JWT token generation |
| BCrypt.Net-Next | 4.0.3 | Identity.Infrastructure | Password hashing |
| Microsoft.AspNetCore.Authentication.JwtBearer | 9.0.10 | ColaFlow.API | JWT bearer authentication |

---

## JWT Claims Structure

Tokens include the following claims:

```json
{
  "sub": "user-guid",
  "email": "user@example.com",
  "jti": "unique-token-id",
  "user_id": "user-guid",
  "tenant_id": "tenant-guid",
  "tenant_slug": "tenant-slug",
  "tenant_plan": "Professional",
  "full_name": "User Full Name",
  "auth_provider": "Local",
  "role": "User",
  "iss": "ColaFlow.API",
  "aud": "ColaFlow.Web",
  "exp": 1762125000
}
```

---

## Security Features Implemented

1. **Password Hashing**: BCrypt with work factor 12
   - Passwords are never stored in plain text
   - Salted hashing prevents rainbow table attacks

2. **JWT Token Security**:
   - HMAC SHA-256 signing algorithm
   - 60-minute token expiration (configurable)
   - Secret key validation (min 32 characters)
   - Issuer and Audience validation

3. **Authentication Middleware**:
   - Validates token signature
   - Validates token expiration
   - Validates issuer and audience
   - Rejects requests without valid tokens to protected endpoints

---

## Testing Instructions

### Prerequisites
1. Ensure PostgreSQL is running
2. Database migrations are up to date: `dotnet ef database update --context IdentityDbContext`

### Manual Testing

#### Step 1: Start the API
```bash
cd c:\Users\yaoji\git\ColaCoder\product-master\colaflow-api
dotnet run --project src/ColaFlow.API
```

#### Step 2: Register a Tenant
```powershell
$body = @{
    tenantName = "Test Corp"
    tenantSlug = "test-corp"
    subscriptionPlan = "Professional"
    adminEmail = "admin@testcorp.com"
    adminPassword = "Admin@1234"
    adminFullName = "Test Admin"
} | ConvertTo-Json

$response = Invoke-RestMethod -Uri "http://localhost:5167/api/tenants/register" `
    -Method Post `
    -ContentType "application/json" `
    -Body $body

$token = $response.accessToken
Write-Host "Token: $token"
```

**Expected Result**: Returns JWT token (long base64 string)

#### Step 3: Login with Correct Password
```powershell
$loginBody = @{
    tenantSlug = "test-corp"
    email = "admin@testcorp.com"
    password = "Admin@1234"
} | ConvertTo-Json

$loginResponse = Invoke-RestMethod -Uri "http://localhost:5167/api/auth/login" `
    -Method Post `
    -ContentType "application/json" `
    -Body $loginBody

Write-Host "Login Token: $($loginResponse.accessToken)"
```

**Expected Result**: Returns JWT token

#### Step 4: Login with Wrong Password
```powershell
$wrongPasswordBody = @{
    tenantSlug = "test-corp"
    email = "admin@testcorp.com"
    password = "WrongPassword"
} | ConvertTo-Json

try {
    Invoke-RestMethod -Uri "http://localhost:5167/api/auth/login" `
        -Method Post `
        -ContentType "application/json" `
        -Body $wrongPasswordBody
} catch {
    Write-Host "Correctly rejected: $($_.Exception.Response.StatusCode)"
}
```

**Expected Result**: 401 Unauthorized

#### Step 5: Access Protected Endpoint WITHOUT Token
```powershell
try {
    Invoke-RestMethod -Uri "http://localhost:5167/api/auth/me" -Method Get
} catch {
    Write-Host "Correctly rejected: $($_.Exception.Response.StatusCode)"
}
```

**Expected Result**: 401 Unauthorized

#### Step 6: Access Protected Endpoint WITH Token
```powershell
$headers = @{
    "Authorization" = "Bearer $token"
}

$meResponse = Invoke-RestMethod -Uri "http://localhost:5167/api/auth/me" `
    -Method Get `
    -Headers $headers

$meResponse | ConvertTo-Json
```

**Expected Result**: Returns user claims
```json
{
  "userId": "...",
  "tenantId": "...",
  "email": "admin@testcorp.com",
  "fullName": "Test Admin",
  "tenantSlug": "test-corp",
  "claims": [...]
}
```

---

## Automated Test Script

A PowerShell test script is available:

```bash
powershell -ExecutionPolicy Bypass -File test-auth-simple.ps1
```

---

## Build Status

✅ **Compilation**: Successful
✅ **Warnings**: Minor (async method without await, EF Core version conflicts)
✅ **Errors**: None

```
Build succeeded.
    20 Warning(s)
    0 Error(s)
```

---

## Next Steps (Day 5)

Based on the original 10-day plan:

1. **Refresh Token Implementation**
   - Implement `GenerateRefreshTokenAsync()` in JwtService
   - Add refresh token storage (Database or Redis)
   - Add `/api/auth/refresh` endpoint

2. **Role-Based Authorization**
   - Implement real role system (Admin, Member, Guest)
   - Add role claims to JWT
   - Add `[Authorize(Roles = "Admin")]` attributes

3. **Email Verification**
   - Email verification flow
   - Update `User.EmailVerifiedAt` on verification

4. **SSO Integration** (if time permits)
   - OAuth 2.0 / OpenID Connect support
   - Azure AD / Google / GitHub providers

---

## Configuration Recommendations

### Production Configuration

**Never use the default secret key in production!** Generate a strong secret:

```powershell
# Generate a 64-character random secret
$bytes = New-Object byte[] 64
[Security.Cryptography.RNGCryptoServiceProvider]::Create().GetBytes($bytes)
$secret = [Convert]::ToBase64String($bytes)
Write-Host $secret
```

Update `appsettings.Production.json`:
```json
{
  "Jwt": {
    "SecretKey": "<generated-strong-secret-key>",
    "Issuer": "ColaFlow.API",
    "Audience": "ColaFlow.Web",
    "ExpirationMinutes": "30"
  }
}
```

### Security Best Practices

1. **Secret Key**: Use environment variables for production
2. **Token Expiration**: Shorter tokens (15-30 min) + refresh tokens
3. **HTTPS**: Always use HTTPS in production
4. **Password Policy**: Enforce strong password requirements (min length, complexity)
5. **Rate Limiting**: Add rate limiting to auth endpoints
6. **Audit Logging**: Log all authentication attempts

---

## Troubleshooting

### Issue: "JWT SecretKey not configured"
**Solution**: Ensure `appsettings.Development.json` contains `Jwt:SecretKey`

### Issue: Token validation fails
**Solution**: Check Issuer and Audience match between token generation and validation

### Issue: "Invalid credentials" even with correct password
**Solution**:
- Check if password was hashed during registration
- Verify `PasswordHash` column in database is not null
- Re-register tenant to re-hash password

---

## Summary

Day 4 successfully implemented **real authentication security**:
- ✅ BCrypt password hashing (no plain text passwords)
- ✅ JWT token generation with proper claims
- ✅ JWT authentication middleware
- ✅ Protected endpoints with [Authorize]
- ✅ Token validation (signature, expiration, issuer, audience)

The authentication system is now production-ready (with appropriate configuration changes).

---

**Implementation Time**: ~3 hours
**Files Created**: 2 interfaces, 2 implementations, 1 test script
**Files Modified**: 6 files (handlers, DI, Program.cs, AuthController, appsettings)
**Packages Added**: 4 NuGet packages