[dev] Adding to the user's session and login credentials

[Adrian Overbury]

Because of upstream authentication requirements (long story -- don't 
ask) I have to add a field the login forms for Horde and IMP that will 
get added to the credentials passed to the preauthenticate hook.  I also 
need to add a corresponding field to the user's session object that 
preauthenticate will combine with what the user entered in the 
credentials to determine if they're allowed to log in or not.

I'm not sure if it's even possible for me to pull something out of the 
user's session object in the preauthenticate hook -- some clarification 
here would be greatly appreciated, as well as an idea of where I should 
be putting the comparison code if preauth isn't going to do the job for me.

As I said, this is a requirement that's being passed down to me, so 
don't shoot the messenger/implementer if you think it's a bad idea. 
Thanks for your time.

Adrian