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.\" $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
.\"
.\" This file was written by Victor B. Wagner <vitus@cryptocom.ru>.
.\" Copyright (c) 2015, 2016 The OpenSSL Project. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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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a certificate with an outdated Netscape Certificate Type extension telling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
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