private boolean isCertificateAllowed(final X509Certificate cert) {
        return regExSubjectDnPattern == null || doesNameMatchPattern(cert.getSubjectDN(), this.regExSubjectDnPattern);
    }
Checks if is certificate allowed based no the pattern given.

@param cert the cert
@return true, if  certificate allowed
support/cas-server-support-x509-core/src/main/java/org/apereo/cas/adaptors/x509/authentication/handler/support/X509CredentialsAuthenticationHandler.java