ASP.NET Core - Using IClaimsTransformation with Windows Authentication

In ASP.NET Core you can implement the IClaimsTransformation interface. This allows you to extend/change the incoming claimsprincipal:

	class ClaimsTransformer : IClaimsTransformation
	{
	public Task<ClaimsPrincipal> TransformAsync(ClaimsPrincipal principal)
	{
	((ClaimsIdentity)principal.Identity).AddClaim(new Claim("now", DateTime.Now.ToString()));
	return Task.FromResult(principal);
	}
	}

view raw ClaimsTransformer.cs hosted with ❤ by GitHub

	public void ConfigureServices(IServiceCollection services)
	{
	services.AddMvc();
	services.AddTransient<IClaimsTransformation, ClaimsTransformer>();
	}

view raw Startup.cs hosted with ❤ by GitHub

Unfortunately my ClaimsTransformer was never invoked when I used Windows Authentication in IIS.

The trick was to explicitly specify the IISServerDefaults.AuthenticationScheme:

	public void ConfigureServices(IServiceCollection services)
	{
	services.AddMvc();
	services.AddTransient<IClaimsTransformation, ClaimsTransformer>();
	services.AddAuthentication(IISServerDefaults.AuthenticationScheme);
	}

view raw Startup.cs hosted with ❤ by GitHub