Once you write an OWIN Middleware service, it can be reused everywhere as long as OWIN is supported. In my last post, I discussed how you could write an Authentication Handler in Katana for Hawk (HMAC Authentication). Good news is NancyFx can be run as an OWIN handler, so you can use many of existing middleware services, including the ones that are ship with Katana.

Running NancyFx as a OWIN handler is pretty straightforward, and discussed in detail as part of the NancyFx documentation here. After run the steps described there and you have the application working, only a few more steps are required to register the additional middleware services.

The example bellow shows how the Startup class is modified to include Hawk authentication.

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        app.UseHawkAuthentication(new HawkAuthenticationOptions
        {
            Credentials = (id) =>
            {
                return new HawkCredential
                {
                    Id = "dh37fgj492je",
                    Key = "werxhqb98rpaxn39848xrunpaw3489ruxnpa98w4rxn",
                    Algorithm = "hmacsha256",
                    User = "steve"
                };
            }
        });

        app.UseNancy();
    }
}

This code registers the Hawk Authentication Handler on top of the OWIN pipeline, so it will try to authenticate the calls before the request messages are passed over to NancyFx.

The authentication handlers in Katana set the user principal in the OWIN environment using the key “server.User”. The following code shows how you can get that principal in a NancyFx module,

public class HomeModule : NancyModule
{
  public HomeModule()
  {
    Get["/"] = x =>
    {
      var env = (IDictionary<string, object>)Context.Items[NancyOwinHost.RequestEnvironmentKey];

      if (!env.ContainsKey("server.User") || env["server.User"] == null)
      {
          return HttpStatusCode.Unauthorized;
      }

      var identity = (ClaimsPrincipal)env["server.User"];

      return "Hello " + identity.Identity.Name; 
    };
}

}

Thanks to OWIN, you don’t know any details of how these cross cutting concerns can be implemented in every possible web application framework.