One directive affects the writing of CGIs.
SSLExportClientCertificates Server config, virtual host, .htaccess, directory
Exports client certificates and the chain behind them to CGIs. The certificates are base 64 encoded in the environment variables SSL_CLIENT_CERT and SSL_CLIENT_CERT_CHAIN_ n , where n runs from 1 up. This directive is only enabled if APACHE_SSL_EXPORT_CERTS is set to TRUE in .../src/include/buff.h.