[SR-Users] Proxied authentication

I'm having trouble divining the proper way to authenticate calls to remote destinations that require it. I'm hoping someone can clear it up.

Freeswitch client server A is authenticated to Kamailio. Freeswitch test server B is authenticated to Kamailio.

Calls from A -> Kamailio -> B fail with rejection of the authentication information that A is using to Kamailio.

As far as I understand, I need to rewrite the authentication information with UAC? However, UAC's uacreg table seems to tie remote users to remote destinations, when all I want to do is authenticate all calls routed to the destination regardless of what the user or the source is. Am I using the wrong module?