Kohana-auth-driver-ldap is a project mainly written in PHP, it's free.
Auth LDAP driver for Kohana 3.x
This is an LDAP driver for the Kohana Auth module. The only method implemented
is login, which attempts to bind the given username and password to LDAP.
This module is dependent on Zend_LDAP. You can install Zend as a Kohana module
using https://github.com/kolanos/kohana-zend. After installing, create your
own ldap.php in application/config, and configure as needed. The Auth
driver parameter should be set to ldap.