mod_sslcrl is a module for the Apache Web server. It verifies the validity of client certificates against the Certificate Revocation Lists (CRL) issued by Certification Authorities (CA). It may be used as an extension to mod_ssl when x509 client certificate authentication is used. mod_sslcrl replaces the mod_ssl directives SSLCARevocationFile and SSLCARevocationPath and automatically downloads CRL files from CAs via HTTP(S).
mod_sslcrl is available at http://modsslcrl.sourceforge.net/.