ValidateAntiForgeryToken with SPA architecture

I would read this article on how to use antiforgery tokens using javascript. The article is written for WebApi but it can easily applied to an MVC controller if you want to.

The short answer is something like this: Inside your cshtml view:

<script>
    @functions{
        public string TokenHeaderValue()
        {
            string cookieToken, formToken;
            AntiForgery.GetTokens(null, out cookieToken, out formToken);
            return cookieToken + ":" + formToken;                
        }
    }

    $.ajax("api/values", {
        type: "post",
        contentType: "application/json",
        data: {  }, // JSON data goes here
        dataType: "json",
        headers: {
            'RequestVerificationToken': '@TokenHeaderValue()'
        }
    });
</script>

Then inside your asp.net controller you need to validate the token like so:

void ValidateRequestHeader(HttpRequestMessage request)
{
    string cookieToken = "";
    string formToken = "";

    IEnumerable<string> tokenHeaders;
    if (request.Headers.TryGetValues("RequestVerificationToken", out tokenHeaders))
    {
        string[] tokens = tokenHeaders.First().Split(':');
        if (tokens.Length == 2)
        {
            cookieToken = tokens[0].Trim();
            formToken = tokens[1].Trim();
        }
    }
    AntiForgery.Validate(cookieToken, formToken);
}

The reason you want to pass it in the headers is because if you pass it as a parameter data parameter in your ajax call, inside the querystring or body, of the request. Then it will be harder for you to get the antiforgery token for all your different scenarios. Because you will have to deserialize the body and then find the token. In the headers its pretty consistent and easy to retrieve.

---

**edit for ray

Here is an example of an action filter which you can use to attribute web api methods to validate if a antiforgerytoken is provided.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Helpers;
using System.Web.Http.Filters;
using System.Net.Http;
using System.Net;
using System.Threading.Tasks;
using System.Web.Http.Controllers;
using System.Threading;

namespace PAWS.Web.Classes.Filters
{
    public class ValidateJsonAntiForgeryTokenAttribute : FilterAttribute, IAuthorizationFilter
    {
        public Task<HttpResponseMessage> ExecuteAuthorizationFilterAsync(HttpActionContext actionContext, CancellationToken cancellationToken, Func<Task<HttpResponseMessage>> continuation)
        {
            if (actionContext == null)
            {
                throw new ArgumentNullException("HttpActionContext");
            }

            if (actionContext.Request.Method != HttpMethod.Get)
            {
                return ValidateAntiForgeryToken(actionContext, cancellationToken, continuation);
            }

            return continuation();
        }

        private Task<HttpResponseMessage> FromResult(HttpResponseMessage result)
        {
            var source = new TaskCompletionSource<HttpResponseMessage>();
            source.SetResult(result);
            return source.Task;
        }

        private Task<HttpResponseMessage> ValidateAntiForgeryToken(HttpActionContext actionContext, CancellationToken cancellationToken, Func<Task<HttpResponseMessage>> continuation)
        {
            try
            {
                string cookieToken = "";
                string formToken = "";
                IEnumerable<string> tokenHeaders;
                if (actionContext.Request.Headers.TryGetValues("RequestVerificationToken", out tokenHeaders))
                {
                    string[] tokens = tokenHeaders.First().Split(':');
                    if (tokens.Length == 2)
                    {
                        cookieToken = tokens[0].Trim();
                        formToken = tokens[1].Trim();
                    }
                }
                AntiForgery.Validate(cookieToken, formToken);
            }
            catch (System.Web.Mvc.HttpAntiForgeryException ex)
            {
                actionContext.Response = new HttpResponseMessage
                {
                    StatusCode = HttpStatusCode.Forbidden,
                    RequestMessage = actionContext.ControllerContext.Request
                };
                return FromResult(actionContext.Response);
            }
            return continuation();
        }
    }
}

Grab value of token in JS var

var antiForgeryToken = $('input[name="__RequestVerificationToken"]').val();

Then just add to your ajax POST headers in the beforeSend function of the .ajax call

beforeSend: function (xhr, settings) {
            if (settings.data != "") {
                settings.data += '&';
            }
            settings.data += '__RequestVerificationToken=' +  encodeURIComponent(antiForgeryToken);
}