Setting up OpenVPN on Azure From Scratch

Why do this? One of the major benefits being able to use the internet with a specified IP address. If you’re going to be working systems that whitelist specific IP addresses, you can use this solution to allow for access regardless of both machine and location.

This guide assumes that you:

  • Have an Azure subscription in place.
  • Have a means of SSHing into a virtual machine, such as OpenSSH.

Setting up OpenVPN Server

Create a virtual machine in Azure with the following specs:

  • Image: Ubuntu Server 18.04 LTS (or later)
  • Size: B1s
  • NSG Ports: 22, 80, 443

Once the virtual machine is created, create an inbound rule that allows access to port 943.

Once that’s done, SSH into the machine and install OpenVPN Access Server:

sudo su

apt update && apt -y install ca-certificates wget net-tools gnupg

wget -qO - https://as-repository.openvpn.net/as-repo-public.gpg | sudo apt-key add -

echo "deb http://as-repository.openvpn.net/as/debian bionic main" > /etc/apt/sources.list.d/openvpn-as-repo.list

apt update && apt -y install openvpn-as

exit

After OpenVPN is installed, set up an admin password:

passwd openvpn

After creating a password, log into OpenVPN with the above credentials at https://YOUR_SERVER_ID/admin.

Enabling HTTPS with Let’s Encrypt

To set up a certificate for OpenVPN using Let’s Encrypt, first set up a domain to use with OpenVPN. This can either be:

  1. A domain created from a DNS name label in the Azure Public IP.
  2. A separate domain pointing to the DNS name label above with A and/or CNAME records.

install Certbot onto the OpenVPN server:

sudo apt-get update
sudo apt-get install software-properties-common
sudo add-apt-repository universe
sudo add-apt-repository ppa:certbot/certbot
sudo apt-get update && sudo apt-get install -y certbot

Then run the following commands to stop OpenVPN, apply cert, and start OpenVPN again :

sudo service openvpnas stop

sudo certbot certonly  --standalone --non-interactive --agree-tos --email YOUR_EMAIL --domains YOUR_DOMAIN --pre-hook 'sudo service openvpnas stop' --post-hook 'sudo service openvpnas start'

sudo ln -s -f /etc/letsencrypt/live/YOUR_DOMAIN/cert.pem /usr/local/openvpn_as/etc/web-ssl/server.crt
sudo ln -s -f /etc/letsencrypt/live/YOUR_DOMAIN/privkey.pem /usr/local/openvpn_as/etc/web-ssl/server.key

sudo service openvpnas start

This command will also handle automatically renewing the cert every three months (via pre-hook and post-hook), which will shut down the VPN for a few seconds while renewing, while removing everyone’s connections. If this is an issue, you can set up a reverse proxy with Apache or NGINX and apply the cert at the reverse proxy level, keeping users connected during renewal.

Finally, verify the URL above is secured.

HTTP -> HTTPS Redirect

The last step is setting up HTTP to redirect to HTTPS, which can be done with a Python script. Create the following file at /usr/local/openvpn_as/port80redirect.py:

import SimpleHTTPServer
import SocketServer
class myHandler(SimpleHTTPServer.SimpleHTTPRequestHandler):
  def do_GET(self):
    print "Request received, sending redirect..."
    self.send_response(301)
    self.send_header('Location', 'https://YOUR_DOMAIN.com' + self.path)
    self.end_headers()
PORT = 80
handler = SocketServer.TCPServer(("", PORT), myHandler)
print "serving at port 80"
handler.serve_forever()

Now set up the script to run at boot:

sudo crontab -e

Add this line to the bottom:

@reboot /usr/bin/screen -dmS port80redirect /usr/bin/python /usr/local/openvpn_as/port80redirect.py

Reboot the server, and verify that accessing via HTTP redirects to HTTPS.

References

Installing OpenVPN on Ubuntu: https://openvpn.net/vpn-software-packages/ubuntu/

Setting up Let’s Encrypt on OpenVPN AS: https://loige.co/using-lets-encrypt-and-certbot-to-automate-the-creation-of-certificates-for-openvpn/

Redirect HTTP -> HTTPS in OpenVPN: https://openvpn.net/vpn-server-resources/how-to-redirect-http-to-https/