Handle anti-fakes at login, even though it is already logged in? ASP.NET MVC

Question

When a user logs in and goes to the login page. If he tries to log in again, you will get Anti-fake.

The fake ban cannot be decrypted. If this application is hosted by a web farm or cluster, make sure that all computers have the same version of ASP.NET web pages and that explicit encryption and verification keys are specified in the configuration. AutoGenerate cannot be used in a cluster.

Another type of error I get:

The anti-fake token provided was intended for a different user based on requirements than the current user.

How to deal with anti-fake errors?

Answer 1

Create an action filter that inherits HandleErrorAttribute, as shown in the following example. Then you can check the request and handle the error.

public class AntiForgeryHandleErrorAttribute : HandleErrorAttribute { public override void OnException(ExceptionContext context) { if (context.Exception is HttpAntiForgeryException) { var url = string.Empty; if (!context.HttpContext.User.Identity.IsAuthenticated) { var requestContext = new RequestContext(context.HttpContext, context.RouteData); url = RouteTable.Routes.GetVirtualPath(requestContext, new RouteValueDictionary(new {Controller = "User", action = "Login"})).VirtualPath; } else { context.HttpContext.Response.StatusCode = 200; context.ExceptionHandled = true; url = GetRedirectUrl(context); } context.HttpContext.Response.Redirect(url, true); } else { base.OnException(context); } } private string GetRedirectUrl(ExceptionContext context) { try { var requestContext = new RequestContext(context.HttpContext, context.RouteData); var url = RouteTable.Routes.GetVirtualPath(requestContext, new RouteValueDictionary(new { Controller = "User", action = "AlreadySignIn" })).VirtualPath; return url; } catch (Exception) { throw new NullReferenceException(); } } } 

This is my example, remember that you must process your redirect sections, depending on your request and requirements.

Then login

 [HttpPost] [AllowAnonymous] [AntiForgeryHandleError] [ValidateAntiForgeryToken] public async Task<ActionResult> Login(UserLoginViewModel model, string returnUrl) { //Your code... } 

Edited for comments

Use another controller / action like AlreadySignIn ()

Controller code

 public ActionResult AlreadySignIn() { return View(); } 

View razor

 @using Microsoft.AspNet.Identity @{ ViewBag.Title = "Switch Accounts"; Layout = "~/Views/Shared/_LayoutLoginRegister.cshtml"; } <div class="col-md-12"> <div class="block-flat text-center" style="padding: 20px; margin-bottom: 0; padding-bottom: 0;"> <i class="glyphicon glyphicon-user"></i> <br /> <label style="padding-bottom: 10px; padding-top: 10px">You're already signed in as <strong>@User.Identity.Name</strong></label> <label style="padding-bottom: 5px; padding-top: 5px">@Html.ActionLink("Remain signed in with this account.", "Login", "User", routeValues: null, htmlAttributes: new { id = "loginLink" })</label> <label style="padding-bottom: 5px; padding-top: 2px">@Html.ActionLink("Click here to sign out and sign with a different account", "LogOff", "User", routeValues: null, htmlAttributes: new { id = "loginLink" })</label> </div> </div> 

Hope this helps.