Try using LDAP directory service.
To use only the Cisco Unified CallManager database for users, which is the default functionality when you install Cisco Unified CallManager, Release 5.0, create users with End User Configuration to add to the database (password, names, device association, and so forth). Authentication takes place against the information that is configured in Cisco Unified CallManager Administration. End users and administrators can make password changes if this method is used. This method does not entail LDAP synchronization.
http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide_chapter09186a00806b0386.html#wp1068959