The problem is about  keystone with sso
 
The situation:
1. the cloud based on OpenStack has use keystone to build its own user account system, and no third user account like ldap or google accounts
2. the cloud may have multi web application/entrance and have multi domain name, so we need sso 
 
So there are two choice to implement sso
1. use CAS or other open source components as sso service and use database authentication which query keystone database.(I think it's odd) 
2. use cookies(including keystone token) between multi web application/entrance
 
which is the better choice?  I think if we use only users from keystone, it's not necessary to use an extra sso service.