I digged through google and found many things called CAS or similar...
did you mean this: http://www.zope.org/Members/mrlex/ACUF ?
I meant http://www.zope.org/Members/regebro/CAS4PAS. It's Zope2 stuff,
but may be somewhat helpful because it's a plugin for PAS (pluggable
authentication services) which (I think) is similiar to PAU in Zope3.
In general you should take a look at Readme and interfaces.py in PAU
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