What is SOCKS5 server with external authorization?

Question

System administration

I've looked all over Google and can't find it.
Need a Socks5 proxy server for *nix with support for external authorization (MySQL).
Ideally, with the ability to write your own authorization function (that is, connect to an existing customer base).
I looked at 3proxy (didn't find a working plugin for authorization), node.js socks5-proxy (the client didn't want to connect - protocol error), Dante (didn't understand if external authorization can be done in it), Simple Socks Server for Perl (protocol error), psocksd (didn't find an authorization implementation example).

The language does not matter, as long as it works out of the box and there is an example of the implementation of authorization.

Or can this be solved by raising a separate sshd with pam-mysql and port forwarding?

HTTP proxy, do not offer VPN ;)