HexaSync Auth Middleware

Authentication middleware for HexaSync services. Supports dual-mode token validation (ECDSA/JWKS and HMAC) for graceful migration from legacy HMAC tokens to ECDSA/JWKS tokens.

Installation

dotnet add package hexasync.auth.middleware

Or add to your .csproj:

<PackageReference Include="hexasync.auth.middleware" Version="1.0.0" />

Quick Start

1. Zero-Config (Environment Variables)

The simplest setup relies entirely on environment variables. This is perfect for containers and cloud deployments.

# Required
SSO_URL=https://sso.hexasync.com          
SSO_SERVICE_SECRET=your-hmac-secret       # For legacy HMAC support

# Optional
JWT_ISSUER=https://sso.hexasync.com       # Defaults to same as SSO_URL if omitted
JWT_AUDIENCE=your-service-audience        # Validates aud claim if provided

// Program.cs
builder.Services.AddHexaSyncAuthentication();

2. Manual Configuration (Delegate)

For more control or when not using environment variables:

builder.Services.AddHexaSyncAuthentication(options =>
{
    options.SsoUrl = "https://sso.hexasync.com";
    options.HmacSecretKey = builder.Configuration["Auth:HmacSecret"];
    options.ValidationMode = TokenValidationMode.DualMode;
});

ECDSA Only (Post-Migration)

After all tokens have been migrated to ECDSA:

builder.Services.AddHexaSyncAuthentication(options =>
{
    options.JwksEndpoint = "https://sso.hexasync.com/.well-known/jwks.json";
    options.Issuer = "https://sso.hexasync.com";
    options.ValidationMode = TokenValidationMode.EcdsaOnly;
});

HMAC Only (Legacy)

For services that only need HMAC validation:

builder.Services.AddHexaSyncAuthentication(options =>
{
    options.HmacSecretKey = builder.Configuration["Auth:HmacSecret"];
    options.Issuer = "https://sso.hexasync.com";
    options.ValidationMode = TokenValidationMode.HmacOnly;
});

Configuration Options

Option	Type	Default	Description
JwksEndpoint	string	null	URL of the JWKS endpoint
HmacSecretKey	string	null	HMAC secret for legacy tokens
Issuer	string	null	Expected token issuer
Audiences	string[]	null	Expected token audiences
ValidationMode	enum	DualMode	ECDSA, HMAC, or DualMode
ValidateIssuer	bool	true	Validate issuer claim
ValidateAudience	bool	true	Validate audience claim
ValidateLifetime	bool	true	Validate token expiration
ClockSkew	TimeSpan	5 min	Clock skew tolerance
JwksCacheDuration	TimeSpan	24 hours	JWKS cache duration (safe due to staging period)
JwksRequestTimeout	TimeSpan	30 sec	JWKS fetch timeout
RequireHttpsMetadata	bool	true	Require HTTPS for JWKS

Multiple Authentication Schemes

If you need to support multiple authentication schemes:

builder.Services.AddAuthentication()
    .AddHexaSync("HexaSync", options =>
    {
        options.JwksEndpoint = "https://sso.hexasync.com/.well-known/jwks.json";
        options.HmacSecretKey = builder.Configuration["Auth:HmacSecret"];
        options.ValidationMode = TokenValidationMode.DualMode;
    })
    .AddJwtBearer("AnotherScheme", options =>
    {
        // Other JWT configuration
    });

Migration Guide

Phase 1: Deploy Middleware (Dual Mode)

Deploy this middleware to all services with DualMode enabled:

options.ValidationMode = TokenValidationMode.DualMode;

Services can now validate both HMAC and ECDSA tokens.

Phase 2: Deploy V3 SSO Endpoints

Deploy the new SSO V3 endpoints that issue ECDSA tokens. New tokens will be validated via JWKS, legacy tokens via HMAC.

Phase 3: Switch to ECDSA Only

After all legacy tokens have expired (30 days), switch to ECDSA only:

options.ValidationMode = TokenValidationMode.EcdsaOnly;
options.HmacSecretKey = null; // Remove HMAC secret

Debugging

The middleware adds a token_validation_method claim to indicate which method was used:

var method = User.FindFirst("token_validation_method")?.Value;
// Returns "ECDSA" or "HMAC"

Security Considerations

1. HTTPS Required: Always use HTTPS for the JWKS endpoint in production
2. Secret Management: Store HMAC secrets securely (e.g., Azure Key Vault, AWS Secrets Manager)
3. Key Rotation: JWKS keys are cached; the cache refreshes automatically
4. Clock Skew: Default 5-minute tolerance; adjust based on your infrastructure

Troubleshooting

JWKS Fetch Fails

Check:

• Network connectivity to JWKS endpoint
• HTTPS certificate validity
• Firewall rules

Token Validation Fails

Check:

• Token expiration
• Issuer/audience mismatch
• Clock synchronization between services

Performance

• JWKS keys are cached for 1 hour by default
• Adjust JwksCacheDuration based on your key rotation frequency

Client Credentials (Service-to-Service Auth)

Obtain access tokens for service-to-service communication using OAuth client credentials flow.

Configuration

# Environment variables
SSO_URL=https://sso.hexasync.com
SSO_CLIENT_ID=your-service-client-id
SSO_CLIENT_SECRET=your-service-client-secret

Setup

// Program.cs

// Option 1: Use IConfiguration (recommended)
builder.Services.AddClientCredentials(builder.Configuration);

// Option 2: Manual configuration
builder.Services.AddClientCredentials(options =>
{
    options.ClientId = "your-client-id";
    options.ClientSecret = "your-client-secret";
    options.SsoUrl = "https://sso.hexasync.com";
});

// Option 3: Explicit values
builder.Services.AddClientCredentials(
    clientId: "your-client-id",
    clientSecret: "your-client-secret");

Usage

public class MyService
{
    private readonly IClientCredentialsService _tokenService;
    private readonly HttpClient _httpClient;

    public MyService(IClientCredentialsService tokenService, HttpClient httpClient)
    {
        _tokenService = tokenService;
        _httpClient = httpClient;
    }

    public async Task CallProtectedApiAsync()
    {
        // Get access token (automatically cached until near expiration)
        var token = await _tokenService.GetAccessTokenAsync();

        // Use token in API call
        _httpClient.DefaultRequestHeaders.Authorization = 
            new AuthenticationHeaderValue("Bearer", token);

        var response = await _httpClient.GetAsync("https://api.example.com/data");
    }
}

Capability-Based Authorization

The middleware includes a capability-based authorization system that works with the system_role JWT claim.

Configuration

Set environment variables or appsettings.json:

# Environment variables (optional - defaults shown)
SSO_URL=https://sso.hexasync.com
SSO_CAPABILITY_CACHE_MINUTES=5
SSO_REQUEST_TIMEOUT_SECONDS=10

Or in appsettings.json:

{
  "Capabilities": {
    "SsoUrl": "https://sso.hexasync.com",
    "CacheMinutes": 5,
    "RequestTimeoutSeconds": 10,
    "EnableCaching": true
  }
}

Setup

// Program.cs

// Option 1: Use IConfiguration (recommended - reads from env vars and appsettings)
builder.Services.AddCapabilityResolution(builder.Configuration);

// Option 2: Manual configuration
builder.Services.AddCapabilityResolution(options =>
{
    options.SsoUrl = "https://sso.hexasync.com";
    options.CacheMinutes = 5;
});

// Option 3: Simple setup with just URL
builder.Services.AddCachedCapabilityResolution(
    ssoBaseUrl: "https://sso.hexasync.com",
    cacheDuration: TimeSpan.FromMinutes(5));

// Option 4: Custom resolver (e.g., direct database access)
builder.Services.AddCapabilityResolution<MyCapabilityResolver>();

// Add middleware (after UseAuthorization)
app.UseAuthentication();
app.UseAuthorization();
app.UseCapabilities(); // Resolves capabilities from system_role claim

What Gets Registered

When you call AddCapabilityResolution(IConfiguration), the following services are automatically registered:

• IOptions<CapabilityOptions> - Configuration options
• IDistributedCache - In-memory cache (can be overridden with Redis, etc.)
• IHttpClientFactory - HTTP client for calling SSO API
• ICapabilityResolver - The capability resolver (cached or non-cached based on config)

Protecting Endpoints

// Minimal API - OR logic (requires ANY of the capabilities)
app.MapGet("/users", GetUsers)
    .RequireCapability("users:read", "admin:full_access");

// Minimal API - AND logic (requires ALL capabilities)
app.MapPost("/users", CreateUser)
    .RequireAllCapabilities("users:write", "audit:enabled");

// MVC Controller
[RequireCapability("users:read", "admin:full_access")]
public IActionResult GetUsers() { ... }

// MVC Controller - AND logic
[RequireCapability("users:write", "audit:enabled", RequireAll = true)]
public IActionResult CreateUser() { ... }

Checking Capabilities in Code

Use the AppCapabilities class for type-safe capability references.

using hexasync.auth.middleware.Capabilities;

// Check single capability
if (httpContext.HasCapability(AppCapabilities.Sso.OAuthApps.Write))
{
    // User can write oauth apps
}

// Check any capability (OR)
if (httpContext.HasAnyCapability(
    AppCapabilities.Sso.OAuthApps.Read, 
    "admin:full_access"))
{
    // User has access
}

// Check all capabilities (AND)
if (httpContext.HasAllCapabilities(
    AppCapabilities.Sso.OAuthApps.Read, 
    AppCapabilities.Sso.OAuthApps.Write))
{
    // User has both read and write access
}

// Get all capabilities
var capabilities = httpContext.GetCapabilities();

// Get role ID from claims
var roleId = httpContext.GetSystemRoleId();

Capability Resolution Flow

The middleware resolves capabilities based on token type:

Token Type	JWT Claims	Resolution
User OAuth	sub, client_id, system_role	User caps ∩ App caps
Client Credentials	client_id, system_role	App caps (from role)
SSO UI (first-party)	sub, client_id, system_role	User caps only

For User OAuth tokens, the effective capabilities are the intersection of:

• User's capabilities (from system_role claim)
• App's capabilities (from client_id → app's role)

This ensures third-party apps can never exceed the user's permissions.

Custom Capability Resolver

Implement ICapabilityResolver for custom resolution logic:

public class MyCapabilityResolver : ICapabilityResolver
{
    private readonly IDistributedCache _cache;
    private readonly MyDbContext _db;

    public async Task<IReadOnlyList<string>> GetCapabilitiesAsync(
        Guid roleId, 
        CancellationToken cancellationToken = default)
    {
        // Check cache first
        var cacheKey = $"caps:{roleId}";
        var cached = await _cache.GetStringAsync(cacheKey, cancellationToken);
        if (!string.IsNullOrEmpty(cached))
        {
            return cached.Split(',');
        }

        // Query database
        var capabilities = await _db.RoleCapabilities
            .Where(rc => rc.RoleId == roleId)
            .Join(_db.Capabilities, rc => rc.CapabilityId, c => c.Id, (rc, c) => c.Name)
            .ToListAsync(cancellationToken);

        // Cache result
        await _cache.SetStringAsync(cacheKey, string.Join(",", capabilities),
            new DistributedCacheEntryOptions { AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5) },
            cancellationToken);

        return capabilities;
    }

    public async Task<IReadOnlyList<string>> GetAppCapabilitiesAsync(
        string clientId,
        CancellationToken cancellationToken = default)
    {
        // Resolve app's role and get capabilities
        var app = await _db.OAuthApplications
            .Where(a => a.ClientId == clientId)
            .Select(a => a.RoleId)
            .FirstOrDefaultAsync(cancellationToken);

        if (app == null) return Array.Empty<string>();

        return await GetCapabilitiesAsync(app.Value, cancellationToken);
    }
}

License

MIT