softaware.Authentication.Hmac 1.0.0

softaware.Authentication.Hmac

softaware.Authentication.Hmac.AspNetCore

Provides an AuthenticationHandler which supports HMAC authentication in an ASP.NET Core project.

Usage:

1. Get your HMAC authenticated clients, for example from the appsettings.json file. For HMAC authentication, an AppId and an ApiKey is required for each client which should get access.

var hmacAuthenticatedApps = this.Configuration
    .GetSection("Authentication")
    .GetSection("HmacAuthenticatedApps")
    .Get<HmacAuthenticationClientConfiguration[]>()
    .ToDictionary(e => e.AppId, e => e.ApiKey);

{
  "Authentication": {
    "HmacAuthenticatedApps": [
        {
            "AppId": "<some-app-id>",
            "ApiKey": "<some-api-key>"
        }
    ]
  }
}

2. Enable HMAC authentication in Startup.cs in the ConfigureServices method:

services
    .AddHmacAuthentication(HmacAuthenticationDefaults.AuthenticationScheme, "HMAC Authentication", o =>
    {
        o.MaxRequestAgeInSeconds = HmacAuthenticationDefaults.MaxRequestAgeInSeconds;
        o.HmacAuthenticatedApps = hmacAuthenticatedApps;
    });

3. Add MemoryCache (from Microsoft.Extensions.Caching.Memory) in Startup.cs in the ConfigureServices method. The MemoryCache is used by the HMAC AuthenticationHandler to determine replay attacks.

services.AddMemoryCache();

4. Enable authentication in Startup.cs in the Configure method:

app.UseAuthentication();

5. Optional: Specify HMAC as the authentication scheme for certain controllers:

[Authorize(AuthenticationSchemes = HmacAuthenticationDefaults.AuthenticationScheme)]
[Route("api/[controller]")]
public class HomeController : Controller
{
   // ...
}

softaware.Authentication.Hmac.Client

Provides a DelegatingHandler for adding an HMAC authorization header to HTTP requests.

Instantiate your HttpClient instance with the ApiKeyDelegatingHandler:

new HttpClient(new ApiKeyDelegatingHandler(appId, apiKey));

Or in case your WebAPI client is another ASP.NET WebAPI (>= ASP.NET Core 2.1), register your HttpClient in the Startup.cs for example as follows:

services.AddTransient(sp => new ApiKeyDelegatingHandler(appId, apiKey));

services
    .AddHttpClient("HmacHttpClient")
    .AddHttpMessageHandler<ApiKeyDelegatingHandler>();

Generate HMAC AppId and ApiKey

To generate an API Key, the following simple Console Application can be used. This implementation is also provided on .NET Fiddle.

using System.Security.Cryptography;

public class Program
{
    public static void Main()
    {
        Console.WriteLine($"AppID: {Guid.NewGuid()} or <some-speaking-name>");
        Console.WriteLine($"ApiKey: {GenerateApiKey()}");
    }

    private static string GenerateApiKey()
    {
        using (var cryptoProvider = new RNGCryptoServiceProvider())
        {
            byte[] secretKeyByteArray = new byte[32]; //256 bit
            cryptoProvider.GetBytes(secretKeyByteArray);
            return Convert.ToBase64String(secretKeyByteArray);
        }
    }
}