 verification of client certificates with any authentication
       method that supports <code class="literal">hostssl</code> entries.
      </p><p>
       On any record using client certificate authentication (i.e. one
       using the <code class="literal">cert</code> authentication method or one
       using the <code class="literal">clientcert</code> option), you can specify
       which part of the client certificate credentials to match using
       the <code class="literal">clientname</code> option. 