// Program.cs

WebApplicationBuilder builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();

builder.Services.AddAuthentication(IISDefaults.AuthenticationScheme);

builder.Services.AddAuthorization(options =>
{
    options.FallbackPolicy = options.DefaultPolicy;
});

WebApplication app = builder.Build();

app.UseHttpsRedirection();

app.UseAuthentication();
app.UseAuthorization();

app.MapControllers();

app.Run();

// Controller

[Route("api/[controller]")]
[ApiController]
public class MyController : ControllerBase
{
    [HttpGet]
    [Authorize]
    public IActionResult Ping()
    {
        return Ok($"Ping Ok. Auth: {WindowsIdentity.GetCurrent()?.Name}");
    }
}