Question concerning Login Controller Hooks > login_authenticate_start and accessing via a third party extension

Greetings,

I am looking for a bit more information on the Login Controller Extension hooks; namely, login_authenticate_start.

I have been using an integrated LDAP login with our install of ExpressionEngine (both in 1.7X and also in 2.6.1); as of now, it involves hacking both the login.php and auth.php core files. I introduced a LDAP-based function that runs an LDAP query on the user’s login credentials. If successful, I then grab the locally stored EE account’s password and pass it on to the authenticate function on login.php. An extra function on auth.php keeps the extracted local password from getting double-hashed. This works for our needs, but obviously hacking the core files is not the best approach. As such, I want to build this into an EE extension. I have downloaded the excellent nce_ldap extension…But it does not work for our needs, as it automatically updates the local EE user’s password with the LDAP account’s password–and I don’t want to synchronize these due to security restrictions in our environment.

That being said, here is my question: is it possible to at least send an extracted password to login_authenticate_start via a third party extension? From what I have gathered via http://ellislab.com/expressionengine/user-guide/development/extension_hooks/cp/login/index.html - login_authenticate_start can “perform additional actions prior to/take over the control panel login routine.” If so, is there a particular syntax that must be used via the third party extension in order to pass another password to login_authenticate_start?

Thanks in advance!