NAME

       X509_cmp, X509_NAME_cmp, X509_issuer_and_serial_cmp, X509_issuer_name_cmp, X509_subject_name_cmp,
       X509_CRL_cmp, X509_CRL_match - compare X509 certificates and related values

SYNOPSIS

        #include <openssl/x509.h>

        int X509_cmp(const X509 *a, const X509 *b);
        int X509_NAME_cmp(const X509_NAME *a, const X509_NAME *b);
        int X509_issuer_and_serial_cmp(const X509 *a, const X509 *b);
        int X509_issuer_name_cmp(const X509 *a, const X509 *b);
        int X509_subject_name_cmp(const X509 *a, const X509 *b);
        int X509_CRL_cmp(const X509_CRL *a, const X509_CRL *b);
        int X509_CRL_match(const X509_CRL *a, const X509_CRL *b);

DESCRIPTION

       This set of functions are used to compare X509 objects, including X509 certificates, X509 CRL objects and
       various values in an X509 certificate.

       The X509_cmp() function compares two X509 objects indicated by parameters a and b. The comparison is
       based on the memcmp result of the hash values of two X509 objects and the canonical (DER) encoding
       values.

       The X509_NAME_cmp() function compares two X509_NAME objects indicated by parameters a and b. The
       comparison is based on the memcmp result of the canonical (DER) encoding values of the two objects using
       i2d_X509_NAME(3).  This procedure adheres to the matching rules for Distinguished Names (DN) given in RFC
       4517 section 4.2.15 and RFC 5280 section 7.1.  In particular, the order of Relative Distinguished Names
       (RDNs) is relevant.  On the other hand, if an RDN is multi-valued, i.e., it contains a set of
       AttributeValueAssertions (AVAs), its members are effectively not ordered.

       The X509_issuer_and_serial_cmp() function compares the serial number and issuer values in the given X509
       objects a and b.

       The X509_issuer_name_cmp(), X509_subject_name_cmp() and X509_CRL_cmp() functions are effectively wrappers
       of the X509_NAME_cmp() function. These functions compare issuer names and subject names of the  objects,
       or issuers of X509_CRL objects, respectively.

       The X509_CRL_match() function compares two X509_CRL objects. Unlike the X509_CRL_cmp() function, this
       function compares the whole CRL content instead of just the issuer name.

RETURN VALUES

       The X509 comparison functions return -1, 0, or 1 if object a is found to be less than, to match, or be
       greater than object b, respectively.

       X509_NAME_cmp(), X509_issuer_and_serial_cmp(), X509_issuer_name_cmp(), X509_subject_name_cmp(),
       X509_CRL_cmp(), and X509_CRL_match() may return -2 to indicate an error.

NOTES

       These functions in fact utilize the underlying memcmp of the C library to do the comparison job. Data to
       be compared varies from DER encoding data, hash value or ASN1_STRING. The sign of the comparison can be
       used to order the objects but it does not have a special meaning in some cases.

       X509_NAME_cmp() and wrappers utilize the value -2 to indicate errors in some circumstances, which could
       cause confusion for the applications.

SEE ALSO

       i2d_X509_NAME(3), i2d_X509(3)

COPYRIGHT

       Copyright 2019-2021 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
       <https://www.openssl.org/source/license.html>.