Question

Using Basic Authentication, and the asp.net Web-Api, where JSON Get/Post’s to my API, I need to check that the username/password exists in the membership table. Which the code below does:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.Security;

namespace MvcApplication4.Filter
{
    public class BasicAuthenticationAttribute : System.Web.Http.Filters.ActionFilterAttribute
    {
        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
        {
            if (actionContext.Request.Headers.Authorization == null)
            {
                actionContext.Response = new System.Net.Http.HttpResponseMessage(System.Net.HttpStatusCode.Unauthorized);
            }
            else
            {
                string authToken = actionContext.Request.Headers.Authorization.Parameter;
                string decodedToken = Encoding.UTF8.GetString(Convert.FromBase64String(authToken));
                string username = decodedToken.Substring(0, decodedToken.IndexOf(":"));
                string password = decodedToken.Substring(decodedToken.IndexOf(":") + 1);

                if (Membership.Provider.ValidateUser(username, password))
                {
                    // User exists in the membership table
                }
                else
                {
                    // User doesn't exist - so return Unathorized
                    actionContext.Response = new System.Net.Http.HttpResponseMessage(System.Net.HttpStatusCode.Unauthorized);
                }
            }
        }
    }
}

I need to make reference to the username in my other controllers, to make sure the username also exists in a lookup table, which says which cars the user is allowed to query. I have a table in my database, and an associated class:

public class ApiMembers
    {
        public int id { get; set; }
        public string UserName { get; set; }
        public int car_id { get; set; }
    }


 [BasicAuthentication]
        public IEnumerable<Cars> GetCars(long id)
        {
            var auth = dba.ApiMembers.Select(a => a.car_id == id && a.UserName=***AuthorisedUserName***).FirstOrDefault();
            if (auth == null || !auth.Any())
                 {
                        throw new HttpResponseException(Request.CreateResponse(HttpStatusCode.Unauthorized));
                 }
            else
            {
                // User exists in table, so give them info on car
            }

My question is, without having to read the HTTP headers again, how do I get the UserName into the AuthorisedUserName part? Is there a way of “logging in” the user in the BasicAuthentication filter, or can you use session variables, like in webforms? Or is there a better way of knowing who has been authenticated in other controllers?

Answer 1

You could set the current principal:

if (Membership.Provider.ValidateUser(username, password))
{
    // User exists in the membership table
    var identity = new GenericIdentity(username);
    Thread.CurrentPrincipal = new GenericPrincipal(identity, null);
}

Now inside your ApiController you could use the User property to access the currently connected username (remark this property was added in ASP.NET MVC 4 RC – in previous versions you could use the Request.GetPrincipal extension method).

[BasicAuthentication]
public HttpResponseMessage Get()
{
    string username = User.Identity.Name;

    ...
}