How to controlling what users can access under al proxied location?

Hi forum.

I open this thread as a follow on of a previous one, once I successfully "mounted" a remote kibana server under a location.
Here is the current, base, vhost setup that allows me to do so:

location /kibana/ {
subs_filter_types text/html text/css text/xml;
subs_filter href=" href="http://publicwebserver.example.com/kibana/;
subs_filter src=" src="http://publicwebserver.example.com/kibana/;

proxy_pass http://elkserver.example.net/;
proxy_read_timeout 90;
}

location /elasticsearch/ {
proxy_pass http://elkserver.example.net;
proxy_read_timeout 90;
}

With this setup, I can access fully transparently to an internal kibana web interface.
Now I want to put some limits to this vhost... I feel it should be easy... but i'm not succeeding.

What I would like is
- When we point the browser to http://publicwebserver.example.com/kibana the browser loads
http://publicwebserver.example.net/kibana/#/dashboards/MyFunnyExampleDashboard
-As a bonus, it would be great that any intent on browsing manually http://publicwebserver.example.net/kibana/XXXXXX
where XXXXX is any kind of browsing will result futile... 404, 403, ie, no access.

Actually, as soon as I play with my current setup, I screw the thing and it all fails... but at the same time, as is, the current setup is equivalent to punching some rules on a firewall an let everyone go directly to the elk server...

Can some Nginx guru help here!

Thank you very much!
Best regards!