title: is it possible to authenticate a DB user in RDS (postgresql) via the certificate used to encrypt SSL connections?
body: <p>I'm trying to apply security best practices to an AWS RDS postgresql instance, but Amazon seems to have gone out of its way to prevent some fairly common and routine features around authentication. I don't seem to be able to authenticate against any external source, which sucks, since now I have to maintain db users completely separately from normal user management. But it seems that, despite the fact that I can use SSL to connect, none of the functionality that might actually validate a client's cert against the server's CA is accessible in RDS.  Is this true?  It seems like the easiest thing in the world to have amazon sign certs with it CA and then validate those certs against that CA when connections are established, yet I cannot find any mention of how to do it in the documentation or out on the web.  Am I really confined ONLY to password authentication of db-internal users? This is almost hard to believe, but after days of research, is the only conclusion I have been able to support.</p>