anchor.diff:  authentication server, a success code is returned.
   
   
  -User Level:
  ------------
  +===== User Level
   
   Although, user level configuration of pam_yubico is possible, this might
   not be a desired configuration option in case of OpenVPN daemon in most
   enterprise.
   
   ii) Configuration of PAM modules for OpenVPN:
  ----------------------------------------------
   
   To configure PAM modules for OpenVPN, create a file named 
   `/etc/pam.d/openvpn` (file name must be one which is specified
   in `/etc/openvpn/server.conf` along with 'plugin' directive)
   and list all the PAM modules in this files accordingly.
   
  -d) Test Setup:
  ---------------
  +==== Test Setup
   
   Our test environment is as follows:
   
  
positive.code:  auth-user-pass
  
  
  b) Installation of pam_yubico module:
  -------------------------------------
  
  Build instructions for pam_yubico are available in its README.
  
  c) Configuration of pam_yubico module:
  --------------------------------------
  
  *) Configuration for user and YubiKey PublicID mapping
  
  There are two ways of user and YubiKey PublicID (token ID) mapping.
  It can be either done at administrative level or at individual user level.
  
  Administrative Level
  --------------------
  
  In Administrative level, system administrators hold right to configure
  the user and YubiKey PublicID mapping. Administrators can achieve this
  
negative.code: 
  We assume that OpenVPN server is already installed on the server.
  
  ==== Configuration of OpenVPN server to support PAM authentication:
  
  * Edit the OpenVPN server configuration file `/etc/openvpn/server.conf`
    to add the following three lines to enable PAM modules for username
  