Apache Reverse Proxy

What if you want to hide an internal server ? you need to configure apache to act as a reverse Proxy. This is the small snippet you need to configure a proxy pass on the public server. Everything is well known expect (for me at least) the directive ProxyPreserveHost that is needed to rewrite the HTTP_SERVER parameter for the hidden server. This way the application can ignore the fact that is behind a proxy.

<VirtualHost IP:443>
    ServerName public.domain.org
    SSLProxyEngine on
    ProxyRequests Off
    ProxyPreserveHost On
    ProxyPass / https://hidden.hiddendomain/
    ProxyPassReverse / https://hidden.hiddendomain/
    <Proxy https://hidden.hiddendomain>
            Order deny,allow
            Deny from all
            Allow from all
    </Proxy>
</VirtualHost>