How do you access appsetting.json parameters in an AuthorizeAttribute class in .Net Core

Question

In my ASP.NET Core MVC app, I have a class that inherits from AuthorizeAttribute and implements IAuthorizationFilter.

namespace MyProject.Attributes
{
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
    public class AllowGroupsAttribute : AuthorizeAttribute, IAuthorizationFilter
    {
        private readonly List<PermissionGroups> groupList = null;
        public AllowGroupsAttribute(params PermissionGroups[] groups)
        {
            groupList = groups.ToList();
        }

        public void OnAuthorization(AuthorizationFilterContext context)
        {
            var executingUser = context.HttpContext.User;

            //If the user is not authenticated then prevent execution
            if (!executingUser.Identity.IsAuthenticated)
            {
                context.Result = new StatusCodeResult((int)System.Net.HttpStatusCode.Forbidden);
            }
        }
    }
}

This allows me to decorate a controller method with something like [AllowGroups(PermissionGroups.Admin, PermissionGroups.Level1]

What I plan to do, is retreive group names from appsettings.json based on the enum values listed and check that the user is a member of those groups.

My question is, what is the correct way to access the app settings from within my attribute class?

Answer 1

Configure settings on startup,

Either via options

services.Configure<MySettings>(Configuration.GetSection("groups"));

Or concrete object model

MySettings settings = Configuration.GetSection("groups").Get<MySettings>();
services.AddSingleton(settings);

And then resolve them through the HttpContext.RequestServices within the filter

//...

IServiceProvider services = context.HttpContext.RequestServices;

MySettings settings = services.GetService<MySettings>();
//-- OR --
//MySettings settings = services.GetService<IOptions<MySettings>>().Value;

//...

while a more service locator approach, it should allow for access to the desired configuration.