Currently VyOS does not support user password authentication, it is possible to make it work using openvpn-options only after commenting out checks in /opt/vyatta/share/perl5/Vyatta/OpenVPN/Config.pm. It would be great if an option was added to the CLI that allows the user to pick between cert based or password based authentication. This mode would bypass the checks for shared-secret-file, tls key, and TLS cert-file as they are not required for auth-user-pass authentication.

More info here:

http://forum.vyos.net/archive/index.php?thread-26487.html

Thanks you!