This tutorial will help you hide your jenkins http page behind VPN

1. Edit jenkins config /etc/default/jenkins:
   • Change:

     HTTP_PORT=8080

     to

     HTTP_PORT=8081
     HTTP_HOST=127.0.0.1

   • Change:

     JENKINS_ARGS="--webroot=/var/cache/$NAME/war --httpPort=$HTTP_PORT"

     to:

     JENKINS_ARGS="--webroot=/var/cache/$NAME/war --httpPort=$HTTP_PORT --httpListenAddress=$HTTP_HOST"

2. Restart jenkins:

   service jenkins restart

3. Install nginx:

   apt install nginx-light

4. Create config file /etc/nginx/sites-available/jenkins:

   upstream app_server {
       server 127.0.0.1:8081 fail_timeout=0;
   }
   
   server {
       listen 8080;
       listen [::]:8080 default ipv6only=on;
       server_name <domain>;
   
       location / {
           # allow VPNs
           allow   <whitelisted ip>;
           allow   <another whitelisted ip>;
   
           # drop rest of the world
           deny    all;
   
           proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
           proxy_set_header Host $http_host;
           proxy_redirect off;
   
           if (!-f $request_filename) {
               proxy_pass http://app_server;
               break;
           }
       }
   }

5. Enable config:

    ln -s /etc/nginx/sites-available/jenkins /etc/nginx/sites-enabled/jenkins

6. Restart nginx:

   service nginx restart

7. #Profit

If you have any questions regarding this - ask Kamil