[thelist] cascading authentication

[John DeStefano]

Here's a relatively simple query regarding a more complex problem: say
a pool of users log in to different systems via various different
authentication methods, including grid certificates, Kerberos, LDAP,
BasicAuth... is there an existing technology that can manage those
users via some sort of cascading authentication method?  For example,
if a user presents a grid certificate, that user is authenticated; if
not, a Kerberos token is sought and checked; if not, an LDAP password
is checked; etc.

Is it possibly in any way to unite users with such diverse
authentication methods, without forcing adherence to a single method?

Thanks,
~John