code: private X509Certificate []getClientCertificatesImpl()
      throws CertificateException
    {
      if (! (_s instanceof SSLSocket))
        return null;
      
      SSLSocket sslSocket = (SSLSocket) _s;
  
      SSLSession sslSession = sslSocket.getSession();
      if (sslSession == null)
        return null;
  
      try {
        return (X509Certificate []) sslSession.getPeerCertificates();
      } catch (SSLPeerUnverifiedException e) {
        if (log.isLoggable(Level.FINEST))
          log.log(Level.FINEST, e.toString(), e);
        
        return null;
      } catch (Throwable e) {
        log.log(Level.FINER, e.toString(), e);
      }
      
      return null;
    }
docs: Returns the client certificate.