[Zope-CMF] Verifying a user based on __ac and __ac_name

[Gitte Wange]

Hello,

I a trying to integrate a payment server into my cmf site.
When people have ordered their stuff and checked out their items, the
payment server fetches a specific page from the zope system. This page is a
reciept.
Since it's the server that fetched the page, the user is not logged in.
But I'm sending the HTTP_COOKIE with the request so I have this when the
payment server fetches the receipt.

Now I was wondering if I could make some sort of script that looped through
all the portal member finding a member matching name in __ac_name and
verifying that the password in __ac is the same as the portal members
password.

Any hints on this ?

TIA,
Gitte Wange