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?

Keelia

configure settings on startup either via options or concrete object model and then resolve them through the HttpContext.RequestServices – Argumentative

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.

Argumentative

Thank you. I think I am a bit closer to getting this implemented now, I have implemented a class with a dictionary to pull the section from settings, no errors there. But I have a build error on the line var settings = services.GetService<MySettings>();. The error reads CS0308 The non-generic method 'IServiceProvider.GetService(Type)' cannot be used with type arguments – Keelia

@Keelia GetSrvice<T> is an extension method. You are most likely missing a using name space for dependency injection. – Argumentative

Ah ha! I added using Microsoft.Extensions.DependencyInjection; to get access to the generic method which resolved my error. Thank you for your help :) – Keelia

Answer 2

I had the same problem and so you solve it

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
public class AllowGroupsAttribute : AuthorizeAttribute, IAuthorizationFilter
{
    IConfigurationBuilder builder = new ConfigurationBuilder()
            .SetBasePath(Directory.GetCurrentDirectory())
            .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true);

            IConfigurationRoot configuration = builder.Build();
            var user = configuration.GetSection("AppConfig").GetSection("user").Value;
            var pass = configuration.GetSection("AppConfig").GetSection("pass").Value;

..........

}

in appsettings.json

"AppConfig": {
    "user": "hola",
    "pass": "mundo"
  },

Gaullism