CAS integration components for LDAP built on ldaptive have been developed by Marvin Addison, a CAS core committer and LDAP module lead. The components are available on GitHub.
The authentication components have been tested thoroughly and found to be an improvement in some notable respects over the Spring LDAP components that ship with CAS. The following GitHub wiki pages elaborate on benefits.
See the GitHub wiki start page for a Spring wiring example that demonstrates how to integrate the components into CAS.