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=head1 NAME

X509_check_issued - checks if certificate is issued by another
certificate

=head1 SYNOPSIS

 #include <openssl/x509v3.h>

 int X509_check_issued(X509 *issuer, X509 *subject);


=head1 DESCRIPTION

This function checks if certificate I<subject> was issued using CA
certificate I<issuer>. This function takes into account not only
matching of issuer field of I<subject> with subject field of I<issuer>,
but also compares B<authorityKeyIdentifier> extension of I<subject> with
B<subjectKeyIdentifier> of I<issuer> if B<authorityKeyIdentifier>
present in the I<subject> certificate and checks B<keyUsage> field of
I<issuer>.

=head1 RETURN VALUES

Function return B<X509_V_OK> if certificate I<subject> is issued by
I<issuer> or some B<X509_V_ERR*> constant to indicate an error.

=head1 SEE ALSO

L<X509_verify_cert(3)>,
L<X509_check_ca(3)>,
L<verify(1)>

=head1 COPYRIGHT

Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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>.

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