ASP.NET Core Authorize AD Groups through web.config

Question

In my old .NET MVC app, I could enable Windows Authentication in IIS and disable anonymous. Then in my web.config file I just had to put in this:

<authorization> 
  <allow roles="Domain\MyADGroupToHaveAccess" />
  <deny users="*" /> 
</authorization> 

In .NET Core 2.0 this will not work – it denies anonymous correctly, but it authorizes all users no matter what.

If I do this:

[Authorize(Roles = "Domain\\MyADGroupToHaveAccess")]

on my HomeController, it works, but I don't want to hardcode this setting in my project as it's something that needs to be changed for other environments.

How can I make web.config to work with AD Authorization? Or is there another way to not hardcode this setting in ASP.NET Core?

Answer 1

I solved this by making it into a policy which is able to call appsettings.json. This way other people who have access to the server can then edit the group to their own.

In Startup.cs:

services.AddAuthorization(options =>
{
    options.AddPolicy("ADRoleOnly", policy => policy.RequireRole(Configuration["SecuritySettings:ADGroup"]));
});

services.AddMvc(config =>
{
    var policy = new AuthorizationPolicyBuilder()
        .RequireAuthenticatedUser()
        .Build();

    config.Filters.Add(new AuthorizeFilter(policy));
});

In appsettings.json (or perhaps appsettings.production.json if you have different):

"SecuritySettings": {
  "ADGroup": "YourDomain\\YourADGroup"
}

In your controllers you can then decorate it with this attribute:

[Authorize(Policy = "ADRoleOnly")]

Hope this can help other people

I have still to figure out how to apply this policy globally, so I don't have to authorize every controller, I'd figure it can be done in the services.AddMvc somehow?

Answer 2

To expand on Morten_564834's answer, here is our approach for this problem. Create a base controller that all controllers inherit from.

[Authorize(Policy = "AdUser")]
public class FTAControllerBase : Controller
{
    private readonly ApplicationDbContext _db;
    private readonly ILogHandler _logger;

    public FTAControllerBase(ApplicationDbContext DbContext, ILogHandler Logger, IWindowsAccountLinker WinAccountLinker)
    {
        _db = DbContext;
        _logger = Logger;

        /// get registered user via authenticated windows user.
        //var user = WinAccountLinker.LinkWindowsAccount();
    }
}

Then in your other controllers:

public class LettersController : FTAControllerBase
{ ... }

If you want granular permissions on methods:

[Authorize("GenerateLetterAdUser")]
[HttpGet]
public IActionResult Generate()
{
    return View();
}

Startup.cs:

// add authorization for application users
var section = Configuration.GetSection($"AuthorizedAdUsers");
var roles = section.Get<string[]>();
services.AddAuthorization(options =>
{
    options.AddPolicy("AdUser", policy => policy.RequireRole(roles));
});

AppSettings.json:

"AuthorizedAdUsers": [
"domain\\groupname"
],