How to integrate with Sharepoint online using claims based authentication from CRM Online sandboxed plugin

Hi,

I'm developing a solution integrating CRM Online with Sharepoint Online and requires to do some custom work from CRM Online plugin (sandboxed) to access Sharepoint Online Web Service.

Thus, claims based authentication is required, but I haven't found any solution which doesn't use WIF:  http://blogs.msdn.com/b/cjohnson/archive/2011/05/14/part-2-headless-authentication-with-sharepoint-online-and-the-client-side-object-model.aspx

 (because CRM online plugins is sandboxed and doesn't allow using Microsoft.Identity.Model.dll).

Any ideas?

Regards,

Rico