External PKI for OpenVPN Certificates

How to deploy a Certificate-based SSL VPN Server

The Aviatrix OpenVPN solution provides certificate-based SSL VPN user authentication in addition to other multi-factor authentication methods such as DUO, Okta, SAML and LDAP. This document describes the process of allowing users to connect to your Cloud instances via OpenVPN when the external PKI mechanism is used.


Obtain the CA certificate, server certificate (for the OpenVPN gateway) and server key from your administrator. The CA certificate will be used to sign the server certificate and user certificate. Your CA certificate will need to contain the CRL Distribution Point URI or you can manually enter it during the configuration steps.

Please note that once you enable the feature, it cannot be disabled. Please test the feature on a separate controller before trying it on a production environment.

Note: Certificates, key, and CRL will need to be in PEM format.

Configuration steps:

  1. From the Aviatrix Controller, go to Settings > Advanced > Certificates page to make sure Certificates Checking is disabled.

  2. Go to OpenVPN > Certificate. Choose the corresponding files for the CA Certificate, Server Certificate, and Server Key.

  3. If your CA Certificate does not contain the CRL information, enter the CRL Distribution Point URI and the CRL Update Interval. By default, the CRL Update Interval is 60 minutes.

  4. Click Import to complete the process.

  5. Go to the Gateway page and click +New Gateway to create a new gateway. This new gateway will be created with those certificates and keys imported. Please refer to http://docs.aviatrix.com/HowTos/uservpn.html on how to create a gateway.

  6. Upon successful gateway creation, go to the OpenVPN > Certificate page.

  7. In the Download VPN Configuration box, select the VPC ID (where your gateway was created) and the LB Name. Click Download to obtain the OVPN file (for example None.ovpn).

Please note: Uploading the certificate files (ca.crt, server.key, server.crt crl uri) again will not update the certificates on gateways that are already deployed.

Client OVPN file

For each OpenVPN client, you will need to generate a certificate signed by the CA private key. Note that the CSR for the certificate must have the key usage attribute set to “e0” and the directive must be set to “TLS Web Client Authentication”. X509v3 Key Usage e0 stands for Digital Signature, Non Repudiation, Key Encipherment should be enabled (No more, no less). With your client certificate and client key ready, edit the None.ovpn with a text editor.

At the bottom of the None.ovpn, insert your client certificate and client key and save the file.

—–END OpenVPN Static key V1—–



CLIENT-CERT                        << Replace your client certificate here



CLIENT-KEY                          << Replace your client key here


Now your None.ovpn is ready for use. Download and install OpenVPN client on your laptop.

Download links:

  1. For Windows users, download the OpenVPN client from this link:


Instructions: https://openvpn.net/index.php/open-source/documentation/howto.html

  1. For MAC users, download Tunnelblick from this link:


      Instructions: https://openvpn.net/index.php/access-server/docs/admin-guides/183-how-to-connect-to-access-server-from-a-mac.html

Once your OpenVPN client is installed, you can use the None.ovpn to connect to your SSL OpenVPN gateway.

The common name field in the certificate will be used by the Controller to identify the user.

Sample scripts

The scripts provided here help you to generate client certificates with the correct attributes set:


Instructions are present in the zip file.

Sample certificates for reference


To view the certificate information(Key usage bits) you can use:

openssl x509 -in client.crt -text -noout

You need to expose the crl.pem over HTTP/HTTPS to the Aviatrix Controller and Gateway so that they can retrieve them via URL.


If you wish to use the profiles feature, you need to add users in the controller (OpenVPN > VPN Users). The username should match the common Name field in the client certificate. Note that you cannot add email here during user addition since certificates are generated externally. You can now associate these users to profiles under OpenVPN > Profiles.