If you have tried to create a SharePoint web application in 2010 with multiple authentication providers you might have felt the need for a custom sign in page. SharePoint 2010 ships with a custom page that contains a drop down and allows the user to select the authentication provider of their choice. This however does not always meet the need, this is why SharePoint 2010 allows customization of sign in page by specifying the it during authentication provider configuration.

One scenario where this becomes even more important is where you don’t want to allow users to sign in using Windows Integrated authentication but need to allow it for search indexing purposes. Yes you can create another zone and enable windows authentication on that zone only. This is a possible option but will complicate search indexing.

In a simpler environment there is a simpler option that does not require any custom coding at all. Here is how to do it… Create a SharePoint Trusted Login Provider. Following links might help you get started with that.

http://blogs.msdn.com/spidentity/archive/2010/01/04/claims-based-authentication-cheat-sheet-part-1.aspx and http://blogs.msdn.com/spidentity/archive/2010/01/23/claims-based-authentication-cheat-sheet-part-2.aspx

Once this is done this will show up in the authentication provider configuration. Here testconnect is the name of the Trusted Login Provider.

After creating the Trusted Login Provider simply specify the following URL (adjusting testconnect to the name of your login provider).

When authentication is required the user will be redirected to this page which looks at the trust parameter in the query string. This parameter is used to automatically redirect the user to the login provider.

This is the quick and dirty way of specifying Sign in page URL. However this is not appropriate for all cases. I will try posting a follow up post that shows how to customize this sign in process a bit more.