Map SSL certificate DN to OPRID

We're going to change our system to require client authentication, aka 2-way SSL.  The sign-on peoplecode in www_authentication gets a request parameter called "com.peoplesoft.tools.ssl_client_dn".  My question is:  does webLogic populate this request parameter automatically and if so how ?  Also, our certs contain a user ID appended to the end of the DN, so , I assume that I may have to parse the property value returned to get actual userID value to then pass to the SetAuthenticationResult function.  Many thanks for all responses !!!