Apache http & ws reverse proxy + password authentication

Hello! I'm running Apache http & ws reverse proxy on my ispconfig3 server with the following apache directives under options tab.
RewriteEngine On
RewriteCond %{HTTP:Upgrade} =websocket [NC]
RewriteRule /(.*) ws://ip/$1 [P,L]
RewriteCond %{HTTP:Upgrade} !=websocket [NC]
RewriteRule /(.*) ptth://ip/$1 [P,L]
ProxyPassReverse / ptth://ip/

Which, and where, additional directives are needed to restrict access to proxy server (front end) by unauthorised users?
Thanks!