Log in/out from non WP database

Hello, I’m looking for a way to handle access to my wordpress site using a separate database for user management.

Basically, my wordpress install resides on DB1 and my member accounts/passwords etc are in DB2.

DB2 is NOT a wordpress database, and I only need to be able to have users login using DB2. No need for registration, profile management, etc for this. Just a simple way to login/logout using DB2 to authenticate users.

Can anyone point me in the right direction? Thanks