=pod =head1 NAME X509_check_ca - check if given certificate is CA certificate =head1 SYNOPSIS #include <openssl/x509v3.h> int X509_check_ca(X509 *cert); =head1 DESCRIPTION This function checks if given certificate is CA certificate (can be used to sign other certificates). =head1 RETURN VALUES Function return 0, if it is not CA certificate, 1 if it is proper X509v3 CA certificate with B<basicConstraints> extension CA:TRUE, 3, if it is self-signed X509 v1 certificate, 4, if it is certificate with B<keyUsage> extension with bit B<keyCertSign> set, but without B<basicConstraints>, and 5 if it has outdated Netscape Certificate Type extension telling that it is CA certificate. Actually, any non-zero value means that this certificate could have been used to sign other certificates. =head1 SEE ALSO L<X509_verify_cert(3)>, L<X509_check_issued(3)>, L<X509_check_purpose(3)> =head1 COPYRIGHT Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved. Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L<https://www.openssl.org/source/license.html>. =cut