[Zope-PAS] PlonePas and authentification

[javi lopez]

hello, thanks for your help.
I am a plone portal and I am doing a product, a little plugin to
sustitute method authentificate from User Manager.
Where can i see this code source and how can I made a new code???

I put this, but it don´t work:

def authenticateCredentials(self, credentials):
        """ Authentication Part """

        userid = credentials.get('user_id')
        return userid, userid


it start with everything i put in login and password in plone portal,
CAn you help me?? thanks