How to authenticate users on one site and pass credentials to other site? ( Windows Authentication, ASP.Net)

Question

Hi, We have multiple web-applications running Windows authentication.
Users log on to the websites using Domain\Username which is different from the DomainOther\UsernameOther that they use on their local computers.
Considering we have 2 sites One.xyz.com and Two.xyz.com both running Windows Authentication (and user logs in to both using Domain\Username), is it possible to have theuser redirect from a page on One.xyz.com to the homepage of Two.xyz.com without entering his credentials again once he has already entered them on One.xyz.com?
Is it possible to do this using ASP.Net?

Kind regards,

Answer 1

SharePoint supports SPNEGO authentication, a form of single sign-on. MSDN has documentation for using SPNEGO for single-sign on .net. Look at the Microsoft Security SSPI. I found this sample with a quick search.

SPNEGO is a Microsoft variation of Kerberos and it will interoperate with IBM products and Oracle WebLogic, as well.

If you want single-sign using an international standard that has wider interoperability than Kerberos, you should use SAML. See Active Directory Fedration for a Microsoft discussion of SAML. However, SAML is much more complicated to implement and configure.

Answer 2

What you are looking for is called Single Sign-On and there are a broad variety of commercial products capable of supporting your needs. Many of them pass credentials via server variables over HTTPS so that the users doesn't see the credentials in the URL. I've worked with companies that wanted to "roll their own" and who went for other approaches (session keys that reference a third server, encrypted and time-sensitive URL strings, etc.).

To get started, you'll want to read the Wikipedia entry on single sign-on (it links with SAML as well). You may want to visit some of the more popular commercial vendors' websites such as Passlogix and Imprivata as well (there are dozens, though, so don't take this list as exhaustive or even particularly recommended - just popular).