Setting domain on Authentication Cookie breaks authentication in MVC

Question

I'd like to share authentication between two websites as I slowly rewrite functionality from the old one and transition to the new one. I found an answer on here to do that: Sharing Authentication between ASP.NET sites

The problem is that when I set the domain property, the authentication cookie stops working. The user still is authenticated succesfully, and the cookie appears to be created and set correctly... but when the site is loaded the user is forced to the login screen.

I'm using the standard MVC generated authentication code, which works fine as long as domain is not set:

public void SignIn(string userName, bool createPersistentCookie)
        {
            if (String.IsNullOrEmpty(userName)) throw new ArgumentException("Value cannot be null or empty.", "userName");

            FormsAuthentication.SetAuthCookie(userName, createPersistentCookie);

        }

If I debug and look at the FormsAuthentication object it looks like the domain and everything else is set correctly.

So what could be causing this, and how do I fix it?

Efe Kaptan Efe Kaptan · Accepted Answer · 2011-08-17T21:04:08

Could you please try with setting a machine key in your web.config? It must be the same within every web site.

http://aspnetresources.com/tools/machineKey

Setting domain on Authentication Cookie breaks authentication in MVC

1 Answers