Doctrine-based CodeIgniter authentication/acl system
You can adapt any auth plugin/library to use Doctrine instead of ActiveRecord. It might be a lot of work to dig through the code, but essentially you'll have to figure out what the plugin/lib is attempting to do with a record (access, modify etc) and then replicate that with a doctrine statement and return the data as expected by the plugin/lib.
I've not used any Auth library/plugin with Doctrine but I've built an ACL for my app using hooks (pre-controller or post-controller works nicely) that works with Doctrine.