MVC 4 provided anti-forgery token was meant for us

Question

I've recently put Live a web application which was built using MVC 4 and Entity Framework 5. The MVC application uses Razor Views.

I noticed using Elmah that when users are logging into the application, sometimes they are getting the following error

The provided anti-forgery token was meant for user "" but the current user is "user"

I've done a bit of research already on how to fix this issue, but nothing seems to work for me. Please see my Login View and corresponding Controller Actions below.

Razor View

@if (!HttpContext.Current.User.Identity.IsAuthenticated)
{

using (Html.BeginForm())
{
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

     <div class="formEl_a">

        <fieldset>
            <legend>Login Information</legend>

            <div class="lbl_a">
                Email
            </div>
            <div class="editor-field">
                @Html.TextBoxFor(m => m.Email, new { @class = "inpt_a" })<br />
                @Html.ValidationMessageFor(m => m.Email)
            </div>

            <div class="lbl_a">
                @Html.LabelFor(m => m.Password)
            </div>
            <div class="editor-field sepH_b">
                @Html.PasswordFor(m => m.Password, new { @class = "inpt_a" })<br />
                @Html.ValidationMessageFor(m => m.Password)
            </div>


        </fieldset>
    </div>
    <br />
      <p>
            <input type="submit" value="Log In" class="btn btn_d sepV_a" />
        </p>

}    
}

Controller

[AllowAnonymous]
public ActionResult Login()
{
     return View();
}

[HttpPost]
[AllowAnonymous]
[ValidateAntiForgeryToken]
public ActionResult Login(LoginModel model, string returnUrl)
{
     if (ModelState.IsValid && _accountService.Logon(model.Email, model.Password, true))
     {
          //Validate
     }
     else
     {
          // inform of failed login
      }

}

I thought this all looked OK, but still the error persists. Does any have any ideas on how to fix this problem?

Your help is greatly appreciated.

Thanks.

Answer 1

I had the same problem when

• User logs in
• Then on the Home Page the User hits Back Button to go back to Login
• User logs in as a different User
• This gave the exception : The provided anti-forgery token was meant for user "" but the current user is "user"

I found this was happening only in IE and I fixed it by doing a couple of things

1. Disabled output caching for the login page, because in debug mode I found that hitting the back button did not generate a new request to the Login page

2. On the login page I added a check to see if the user is already authenticated, and if so logged out the user, and then redirected to the Login page again.

   [AllowAnonymous]
   [OutputCache(NoStore=true, Location=System.Web.UI.OutputCacheLocation.None)]
   public ActionResult Login)
   {
       if (HttpContext.Request.IsAuthenticated)
       {
           WebSecurity.Logout();
           Session.Abandon();
           return RedirectToAction("Login");
       }
   
       return View();
   }
   

Answer 2

I believe this is occurring because the users are double-clicking the submit button on the form. At least that's EXACTLY the case on my site.

Troubleshooting anti-forgery token problems

Answer 3

The validation code that runs against an AntiForgeryToken also checks your logged in user credentials haven’t changed – these are also encrypted in the cookie. This means that if you logged in or out in a popup or another browser tab, your form submission will fail with the following exception:

System.Web.Mvc.HttpAntiForgeryException (0x80004005):
The provided anti-forgery token was meant for user "", but the current user is "SomeOne".

You can turn this off by putting AntiForgeryConfig.SuppressIdentityHeuristicChecks = true; in Application_Start method inside Global.asax file.

When a AntiForgeryToken doesn’t validate your website will throw an Exception of type System.Web.Mvc.HttpAntiForgeryException. You can make this a little easier by at least giving the user a more informative page targeted at these exceptions by catching the HttpAntiForgeryException.

private void Application_Error(object sender, EventArgs e)
{
    Exception ex = Server.GetLastError();

    if (ex is HttpAntiForgeryException)
    {
        Response.Clear();
        Server.ClearError(); //make sure you log the exception first
        Response.Redirect("/error/antiforgery", true);
    }
}

More info:

Anti forgery token is meant for user “” but the current user is “username”

Html.AntiForgeryToken – Balancing Security with Usability