.\"	$OpenBSD: X509_check_ca.3,v 1.3 2017/01/06 19:19:54 schwarze Exp $
.\"	OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
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.Dd $Mdocdate: January 6 2017 $
.Dt X509_CHECK_CA 3
.Os
.Sh NAME
.Nm X509_check_ca
.Nd check whether a certificate is a CA certificate
.Sh SYNOPSIS
.In openssl/x509v3.h
.Ft int
.Fo X509_check_ca
.Fa "X509 *cert"
.Fc
.Sh DESCRIPTION
This function checks whether the given certificate is a CA certificate,
that is, whether it can be used to sign other certificates.
.Sh RETURN VALUES
This functions returns non-zero if
.Fa cert
is a CA certificate or 0 otherwise.
.Pp
The following return values identify specific kinds of CA certificates:
.Bl -tag -width 2n
.It 1
an X.509 v3 CA certificate with
.Sy basicConstraints
extension CA:TRUE
.It 3
a self-signed X.509 v1 certificate
.It 4
a certificate with
.Sy keyUsage
extension with bit
.Sy keyCertSign
set, but without
.Sy basicConstraints
.It 5
a certificate with an outdated Netscape Certificate Type extension telling
that it is a CA certificate
.El
.Sh SEE ALSO
.Xr X509_check_issued 3 ,
.Xr X509_verify_cert 3