How can I supply an AntiForgeryToken when posting JSON data using $.ajax?

Question

I am using the code as below of this post:

First I will fill an array variable with the correct values for the controller action.

Using the code below I think it should be very straightforward by just adding the following line to the JavaScript code:

data["__RequestVerificationToken"] = $('[name=__RequestVerificationToken]').val();

The <%= Html.AntiForgeryToken() %> is at its right place, and the action has a [ValidateAntiForgeryToken]

But my controller action keeps saying: "Invalid forgery token"

What am I doing wrong here?

Code

data["fiscalyear"] = fiscalyear;
data["subgeography"] = $(list).parent().find('input[name=subGeography]').val();
data["territories"] = new Array();

$(items).each(function() {
    data["territories"].push($(this).find('input[name=territory]').val());
});

    if (url != null) {
        $.ajax(
        {
            dataType: 'JSON',
            contentType: 'application/json; charset=utf-8',
            url: url,
            type: 'POST',
            context: document.body,
            data: JSON.stringify(data),
            success: function() { refresh(); }
        });
    }

Answer 1

You don't need the ValidationHttpRequestWrapper solution since MVC 4. According to this link.

1. Put the token in the headers.
2. Create a filter.
3. Put the attribute on your method.

Here is my solution:

var token = $('input[name="__RequestVerificationToken"]').val();
var headers = {};
headers['__RequestVerificationToken'] = token;
$.ajax({
    type: 'POST',
    url: '/MyTestMethod',
    contentType: 'application/json; charset=utf-8',
    headers: headers,
    data: JSON.stringify({
        Test: 'test'
    }),
    dataType: "json",
    success: function () {},
    error: function (xhr) {}
});


[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, AllowMultiple = false, Inherited = true)]
public class ValidateJsonAntiForgeryTokenAttribute : FilterAttribute, IAuthorizationFilter
{
    public void OnAuthorization(AuthorizationContext filterContext)
    {
        if (filterContext == null)
        {
            throw new ArgumentNullException("filterContext");
        }

        var httpContext = filterContext.HttpContext;
        var cookie = httpContext.Request.Cookies[AntiForgeryConfig.CookieName];
        AntiForgery.Validate(cookie != null ? cookie.Value : null, httpContext.Request.Headers["__RequestVerificationToken"]);
    }
}


[HttpPost]
[AllowAnonymous]
[ValidateJsonAntiForgeryToken]
public async Task<JsonResult> MyTestMethod(string Test)
{
    return Json(true);
}

Answer 2

I was just implementing this actual problem in my current project. I did it for all Ajax POSTs that needed an authenticated user.

First off, I decided to hook my jQuery Ajax calls so I do not to repeat myself too often. This JavaScript snippet ensures all ajax (post) calls will add my request validation token to the request. Note: the name __RequestVerificationToken is used by the .NET framework so I can use the standard Anti-CSRF features as shown below.

$(document).ready(function () {
    securityToken = $('[name=__RequestVerificationToken]').val();
    $('body').bind('ajaxSend', function (elm, xhr, s) {
        if (s.type == 'POST' && typeof securityToken != 'undefined') {
            if (s.data.length > 0) {
                s.data += "&__RequestVerificationToken=" + encodeURIComponent(securityToken);
            }
            else {
                s.data = "__RequestVerificationToken=" + encodeURIComponent(securityToken);
            }
        }
    });
});

In your Views where you need the token to be available to the above JavaScript code, just use the common HTML-Helper. You can basically add this code wherever you want. I placed it within a if(Request.IsAuthenticated) statement:

@Html.AntiForgeryToken() // You can provide a string as salt when needed which needs to match the one on the controller

In your controller simply use the standard ASP.NET MVC anti-CSRF mechanism. I did it like this (though I actually used a salt).

[HttpPost]
[Authorize]
[ValidateAntiForgeryToken]
public JsonResult SomeMethod(string param)
{
    // Do something
    return Json(true);
}

With Firebug or a similar tool you can easily see how your POST requests now have a __RequestVerificationToken parameter appended.

Answer 3

What is wrong is that the controller action that is supposed to handle this request and which is marked with the [ValidateAntiForgeryToken] expects a parameter called __RequestVerificationToken to be POSTed along with the request.

There's no such parameter POSTed as you are using JSON.stringify(data) which converts your form to its JSON representation and so the exception is thrown.

So I can see two possible solutions here:

Number 1: Use x-www-form-urlencoded instead of JSON for sending your request parameters:

data["__RequestVerificationToken"] = $('[name=__RequestVerificationToken]').val();
data["fiscalyear"] = fiscalyear;
// ... other data if necessary

$.ajax({
    url: url,
    type: 'POST',
    context: document.body,
    data: data,
    success: function() { refresh(); }
});

Number 2: Separate the request into two parameters:

data["fiscalyear"] = fiscalyear;
// ... other data if necessary
var token = $('[name=__RequestVerificationToken]').val();

$.ajax({
    url: url,
    type: 'POST',
    context: document.body,
    data: { __RequestVerificationToken: token, jsonRequest: JSON.stringify(data) },
    success: function() { refresh(); }
});

So in all cases you need to POST the __RequestVerificationToken value.

Answer 4

You can set $.ajax 's traditional attribute and set it to true, to send json data as url encoded form. Make sure to set type:'POST'. With this method you can even send arrays and you do not have to use JSON.stringyfy or any changes on server side (e.g. creating custom attributes to sniff header )

I have tried this on ASP.NET MVC3 and jquery 1.7 setup and it's working

following is the code snippet.

var data = { items: [1, 2, 3], someflag: true};

data.__RequestVerificationToken = $(':input[name="__RequestVerificationToken"]').val();

$.ajax({
    url: 'Test/FakeAction'
    type: 'POST',
    data: data
    dataType: 'json',
    traditional: true,
    success: function (data, status, jqxhr) {
        // some code after succes
    },
    error: function () {
        // alert the error
    }
});

This will match with MVC action with following signature

[HttpPost]
[Authorize]
[ValidateAntiForgeryToken]
public ActionResult FakeAction(int[] items, bool someflag)
{
}

Answer 5

You won't ever have to validate an AntiForgeryToken when you receive posted JSON.

The reason is that AntiForgeryToken has been created to prevent CSRF. Since you can't post AJAX data to another host and HTML forms can't submit JSON as the request body, you don't have to protect your app against posted JSON.

Answer 6

I have resolved it globally with RequestHeader.

$.ajaxPrefilter(function (options, originalOptions, jqXhr) {
    if (options.type.toUpperCase() === "POST") {
        // We need to add the verificationToken to all POSTs
        if (requestVerificationTokenVariable.length > 0)
            jqXhr.setRequestHeader("__RequestVerificationToken", requestVerificationTokenVariable);
    }
});

where the requestVerificationTokenVariable is an variable string that contains the token value. Then all ajax call send the token to the server, but the default ValidateAntiForgeryTokenAttribute get the Request.Form value. I have writed and added this globalFilter that copy token from header to request.form, than i can use the default ValidateAntiForgeryTokenAttribute:

public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{
      filters.Add(new GlobalAntiForgeryTokenAttribute(false));
}


public class GlobalAntiForgeryTokenAttribute : FilterAttribute, IAuthorizationFilter
{
    private readonly bool autoValidateAllPost;

    public GlobalAntiForgeryTokenAttribute(bool autoValidateAllPost)
    {
        this.autoValidateAllPost = autoValidateAllPost;
    }

    private const string RequestVerificationTokenKey = "__RequestVerificationToken";
    public void OnAuthorization(AuthorizationContext filterContext)
    {
        var req = filterContext.HttpContext.Request;
        if (req.HttpMethod.ToUpperInvariant() == "POST")
        {
            //gestione per ValidateAntiForgeryToken che gestisce solo il recupero da Request.Form (non disponibile per le chiamate ajax json)
            if (req.Form[RequestVerificationTokenKey] == null && req.IsAjaxRequest())
            {
                var token = req.Headers[RequestVerificationTokenKey];
                if (!string.IsNullOrEmpty(token))
                {
                    req.Form.SetReadOnly(false);
                    req.Form[RequestVerificationTokenKey] = token;
                    req.Form.SetReadOnly(true);
                }
            }

            if (autoValidateAllPost)
                AntiForgery.Validate();
        }
    }
}

public static class NameValueCollectionExtensions
{
    private static readonly PropertyInfo NameObjectCollectionBaseIsReadOnly = typeof(NameObjectCollectionBase).GetProperty("IsReadOnly", BindingFlags.FlattenHierarchy | BindingFlags.NonPublic | BindingFlags.Instance);

    public static void SetReadOnly(this NameValueCollection source, bool readOnly)
    {
        NameObjectCollectionBaseIsReadOnly.SetValue(source, readOnly);
    }
}

This work for me :)

Answer 7

You can't validate an content of type contentType: 'application/json; charset=utf-8' because your date will be uploaded not in the Form property of the request, but in the InputStream property, and you will never have this Request.Form["__RequestVerificationToken"].

This will be always empty and validation will fail.

Answer 8

I hold the token in my JSON object and I ended up modifying the ValidateAntiForgeryToken class to check the InputStream of the Request object when the post is json. I've written a blog post about it, hopefully you might find it useful.

Answer 9

Check out Dixin's Blog for a great post on doing exactly that.

Also, why not use $.post instead of $.ajax?

Along with the jQuery plugin on that page, you can then do something as simple as:

        data = $.appendAntiForgeryToken(data,null);

        $.post(url, data, function() { refresh(); }, "json");

Answer 10

AJAX based model posting with AntiForgerytoken can be made bit easier with Newtonsoft.JSON library
Below approach worked for me:
Keep your AJAX post like this:

$.ajax({
  dataType: 'JSON',
  url: url,
  type: 'POST',
  context: document.body,
  data: {
    '__RequestVerificationToken': token,
    'model_json': JSON.stringify(data)
  };,
  success: function() {
    refresh();
  }
});

Then in your MVC action:

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(FormCollection data) {
 var model = JsonConvert.DeserializeObject < Order > (data["model_json"]);
 return Json(1);
}

Hope this helps :)

Answer 11

I had to be a little shady to validate anti-forgery tokens when posting JSON, but it worked.

//If it's not a GET, and the data they're sending is a string (since we already had a separate solution in place for form-encoded data), then add the verification token to the URL, if it's not already there.
$.ajaxSetup({
    beforeSend: function (xhr, options) {
        if (options.type && options.type.toLowerCase() !== 'get' && typeof (options.data) === 'string' && options.url.indexOf("?__RequestVerificationToken=") < 0 && options.url.indexOf("&__RequestVerificationToken=") < 0) {
            if (options.url.indexOf('?') < 0) {
                options.url += '?';
            }
            else {
                options.url += '&';
            }
            options.url += "__RequestVerificationToken=" + encodeURIComponent($('input[name=__RequestVerificationToken]').val());
        }
    }
});

But, as a few people already mentioned, the validation only checks the form - not JSON, and not the query string. So, we overrode the attribute's behavior. Re-implementing all of the validation would have been terrible (and probably not secure), so I just overrode the Form property to, if the token were passed in the QueryString, have the built-in validation THINK it was in the Form.

That's a little tricky because the form is read-only, but doable.

    if (IsAuth(HttpContext.Current) && !IsGet(HttpContext.Current))
    {
        //if the token is in the params but not the form, we sneak in our own HttpContext/HttpRequest
        if (HttpContext.Current.Request.Params != null && HttpContext.Current.Request.Form != null
            && HttpContext.Current.Request.Params["__RequestVerificationToken"] != null && HttpContext.Current.Request.Form["__RequestVerificationToken"] == null)
        {
            AntiForgery.Validate(new ValidationHttpContextWrapper(HttpContext.Current), null);
        }
        else
        {
            AntiForgery.Validate(new HttpContextWrapper(HttpContext.Current), null);
        }
    }

    //don't validate un-authenticated requests; anyone could do it, anyway
    private static bool IsAuth(HttpContext context)
    {
        return context.User != null && context.User.Identity != null && !string.IsNullOrEmpty(context.User.Identity.Name);
    }

    //only validate posts because that's what CSRF is for
    private static bool IsGet(HttpContext context)
    {
        return context.Request.HttpMethod.ToUpper() == "GET";
    }

...

internal class ValidationHttpContextWrapper : HttpContextBase
{
    private HttpContext _context;
    private ValidationHttpRequestWrapper _request;

    public ValidationHttpContextWrapper(HttpContext context)
        : base()
    {
        _context = context;
        _request = new ValidationHttpRequestWrapper(context.Request);
    }

    public override HttpRequestBase Request { get { return _request; } }

    public override IPrincipal User
    {
        get { return _context.User; }
        set { _context.User = value; }
    }
}

internal class ValidationHttpRequestWrapper : HttpRequestBase
{
    private HttpRequest _request;
    private System.Collections.Specialized.NameValueCollection _form;

    public ValidationHttpRequestWrapper(HttpRequest request)
        : base()
    {
        _request = request;
        _form = new System.Collections.Specialized.NameValueCollection(request.Form);
        _form.Add("__RequestVerificationToken", request.Params["__RequestVerificationToken"]);
    }

    public override System.Collections.Specialized.NameValueCollection Form { get { return _form; } }

    public override string ApplicationPath { get { return _request.ApplicationPath; } }
    public override HttpCookieCollection Cookies { get { return _request.Cookies; } }
}

There's some other stuff that's different about our solution (specifically, we're using an HttpModule so we don't have to add the attribute to every single POST) that I left out in favor of brevity. I can add it if necessary.