These two links offer some very interesting and detailed documents on Common Criteria's evaluation of SiteMinder R12sp1-cr3. In particular the "Security Target" document gives a wealth on information on the underlying workings of SiteMinder.
Find these documents and many more in their Access Control Device and System repository. As well as the SiteMinder documentation, it contains evaluations of other Identity and Access Management products.
Common Criteria Certified Product List