[Dovecot] Master user creds for proxy stored statically/locally?

I have successfully set up the master user on the destination server (2.0.11) and tests have worked. now I'm working on the proxy Before I had the proxy just forward everything to the backend and had the destination server do the authentication.

My authentication is done via LDAP but not really sure how to append the master user and password to the users credentials after authentication is done. id rather not have the master user/pass in each users ldap entry and returned after doing a lookup or add a destuser field for each user... basically i prefer not having to add any new attributes to LDAP

Can the information be stored locally in a file on the proxy? do i just make the same master user file that I have on the backend?

Thanks!