Google Authenticator, and (all?) other rotating-pin multi-factor authentication systems, rely on the clock on the token device (in this case your smart-phone or tablet) and the authenticating system (in this case the OpenVPN server). If the clocks are different by more than a few seconds or so, it will break your authentication.

In a previous post I dealt with setting up an OpenVPN Community Edition server which is the free version of OpenVPN. I had initially hoped to use Authy for two-factor authentication in addition to LDAP but later found out that wasn’t going to work. So now I am looking at using DUO for two-factor authentication […]