[Zope] User Folder

[javi lopez]

hello thanks for your help.
I am doing a new pluging for PAS, I need take users and login for
Plone. To do it, i did this class:

class ValidaPlugin(BasePlugin):

    """ PAS plugin
    """
    uservar = 'X_REMOTE_USER'
    meta_type = 'ValidaPlugin'
    security = ClassSecurityInfo()

    _properties = ({'id':'uservar','type':'string'},)

    def __init__(self, id, title=None):
        self._id = self.id = id
        self.title = title

    security.declarePrivate('authenticateCredentials')
    def authenticateCredentials(self, credentials):
        """ Authentication Part """
        login = credentials.get('login', '')
        password = credentials.get('password', '')
        return login, login

classImplements(ValidaPlugin, IAuthenticationPlugin)

InitializeClass(ValidaPlugin)

it work bad, it start with everything i put on username and password,
it don´t validate if user exist. How can i do it???