Passing Kerberos token of the authenticated user from IIS 7 to REST web services

I have a web site running on IIS7 configured to use Windows authentication. I'd like to make a call from the site to a REST web service and pass the Kerberos token of the user (authentic开发者_运维知识库ated while accessing the web site) in Authorization header (or any HTTP header). I want REST service to extract additional info like user groups, etc.