Reverse Proxy Auth

I had asked earlier about LDAP/AD Integration in a self-hosted environment, and wanted to double-check another possibility. Is it possible to log in with a reverse proxy server doing Basic Authentication? Or alternatively, is there some other header that could be passed that would be specific to the Manager application?

Or even, is there any scheme where users credentials are kept external to the software? I am looking for somewhere that they can be centrally managed, even for a small org.