.NET MVC, Do something after ValidateAntiForgeryToken check fails

Question

In my form I have

@Html.AntiForgeryToken()

and the receiving controller action has

    [HttpPost, ValidateAntiForgeryToken]  
    public ActionResult Login(LoginViewModel model)  
    {
      //if detects a post request missing token, 
      //I wish to log form info for later inspection
    }

When a post request missing token occurs, the framework does not proceed into the method. If I wish to log form info for later inspection, what can I do and where?

Answer 1

Another approach is to create a Custom Exception Filter to catch AntiForgery exceptions and log the form details from there, details below:

public class AntiForgeryExceptionAttribute : FilterAttribute, IExceptionFilter
{
    public void OnException(ExceptionContext filterContext)
    {
        // ANTIFORGERY TOKEN NOT PRESENT
        if (!filterContext.ExceptionHandled && filterContext.Exception is HttpAntiForgeryException)
        {
            var request = new HttpRequestWrapper(System.Web.HttpContext.Current.Request);
            // Use your own logging service to log the results
            var _logger = new LoggingService();
            foreach (var key in request.Form.AllKeys)
            {
                var value = request.Form[key];
                // "key" is the form input name and "value" is the form input value
                _logger.Log("~~> " + key + " ==> " + value);
            }

            filterContext.ExceptionHandled = true;
        }
    }
}

and register the custom filter in global.asax:

protected void Application_Start()
{
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    GlobalFilters.Filters.Add(new AntiForgeryExceptionAttribute());
}