validation of username and passwrod during login

Hello, I'm working on a customized CPS 3.4.2 and I'm trying to store the
user passwords using a md5 encryption. So, I've solved the problem of
writing on the field 'password' (of the members shema) using a
customized method that encrypt like this (portal_mytool is an example of
a tool):

    * In the 'password' field of 'members' schema:

        Write expression: python: portal.portal_mytool.encryptMd5(value)


Now, I have to change the way the password is validated when a user logs
in the portal, but I cannot find the right point where this is done
(I've been looking at CMFCore.CookieCrumbler class and 'logged_in.py'
script, ...nothing)

Anybody knows where can I find that login validation feature? 

Thanks!
_______________________________________________
cps-devel mailing list
http://lists.nuxeo.com/mailman/listinfo/cps-devel