ASP.NET Core - Authorization Using Windows Authentication

Question

I have configured my web api to work with windows authentication. My goal is essentially to restrict certain actions in my controllers based on a users windows account. Some will be able to preform read actions while others will be able to preform actions that will write to the underlying database. I have found plenty of documentation on how to set up claims based authorization which is the route I think I need to go. What I have not found is how to set this up with windows auth. I think I am missing a middle step such as registering the windows auth as the identity provider?

startup.cs

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc();

    services.AddAuthentication(IISDefaults.AuthenticationScheme);

    services.AddAuthorization(options =>
    {
        options.AddPolicy("readOnly", policy =>
                          policy.RequireClaim(`???????????????????????`));
        options.AddPolicy("write", policy =>
                          policy.RequireClaim(`???????????????????????`));
    });
}

Controller

[Authorize(Policy = "ReadOnly")]
public class MyController : Controller
{
    public ActionResult SomeReadOnlyAction()
    {
        //Return data from database
    }

    [Authorize(Policy = "Write")]
    public ActionResult AWriteAction()
    {
        //Create/Update/Delete data from database
    }
}

I guess another way to ask this question is how do you configure or access claims/roles etc... with windows authentication.

That's what may be missing. See link: learn.microsoft.com/en-us/aspnet/core/security/authentication/… — haldo
– haldo, Commented Nov 28, 2018 at 17:09
You are absolutely right. I have added that in and updated the code above. I guess my next question is how do i access the credentials to then build a policy around it so that i can use specific authorization attributes on my controller actions? — LCaraway
– LCaraway, Commented Nov 28, 2018 at 17:13

Nan Yu · Accepted Answer · 2018-11-29 06:26:28Z

12

That seems you want to use claims-based authorization via policies . After setting windows authentication in your application , you could add custom claim to ClaimsPrincipal ,check user's identity and confirm which permission current user has :

You can add a claims transformation service to your application:

class ClaimsTransformer : IClaimsTransformation
{
    public Task<ClaimsPrincipal> TransformAsync(ClaimsPrincipal principal)
    {
        var id = ((ClaimsIdentity)principal.Identity);

        var ci = new ClaimsIdentity(id.Claims, id.AuthenticationType, id.NameClaimType, id.RoleClaimType);
        if (ci.Name.Equals("name"))
        {
            ci.AddClaim(new Claim("permission", "readOnly"));
        }
        else
        {
            ci.AddClaim(new Claim("permission", "write"));

        }


        var cp = new ClaimsPrincipal(ci);

        return Task.FromResult(cp);
    }
}

Add to Startup.cs(.net Core 2.0) :

    services.AddTransient<IClaimsTransformation, ClaimsTransformer>();

Set your policy :

    services.AddAuthorization(options =>
    {
        options.AddPolicy("Readonly", policy =>
                          policy.RequireClaim("permission", "readOnly"));

        options.AddPolicy("Write", policy =>
                        policy.RequireClaim("permission", "write"));
    });

Restrict access to a controller or action by requiring this policy:

    [Authorize(Policy = "Write")]
    public IActionResult Contact()
    {
        ViewData["Message"] = "Your contact page.";

        return View();
    }

If you have already add groups(write,readonly) in your AD and add the related users to group , you can also check the groups :

public static class Security
{
    public static bool IsInGroup(this ClaimsPrincipal User, string GroupName)
    {
        var groups = new List<string>();

        var wi = (WindowsIdentity)User.Identity;
        if (wi.Groups != null)
        {
            foreach (var group in wi.Groups)
            {
                try
                {
                    groups.Add(group.Translate(typeof(NTAccount)).ToString());
                }
                catch (Exception)
                {
                    // ignored
                }
            }
            return groups.Contains(GroupName);
        }
        return false;
    }
}

And use like :

 if (User.IsInGroup("GroupName"))
 {

 }

answered Nov 29, 2018 at 6:26

Nan Yu

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7 Comments

LCaraway Over a year ago

This is great! Where does the if(User.IsInGroup)... go? Does it get dropped in the ClaimsTransformer Class?

LCaraway Over a year ago

Or would you use that as an alternative to the ClaimsTransformer?

Nan Yu Over a year ago

@LCaraway , it depends you , it can be in any class .

LCaraway Over a year ago

When the group.Translate() is ran it returns an exception stating the trust relationship between the workstation and the primary domain has failed...

Nan Yu Over a year ago

See how to solve the issue :support.microsoft.com/en-hk/help/2771040/… and support.citrix.com/article/CTX227147

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