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.\" ========================================================================
.\"
.IX Title "X509_CMP 3SSL"
.TH X509_CMP 3SSL "2021-03-22" "1.1.1d" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH "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
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This set of functions are used to compare X509 objects, including X509
certificates, X509 \s-1CRL\s0 objects and various values in an X509 certificate.
.PP
The \fBX509_cmp()\fR function compares two \fBX509\fR objects indicated by parameters
\&\fBa\fR and \fBb\fR. The comparison is based on the \fBmemcmp\fR result of the hash
values of two \fBX509\fR objects and the canonical (\s-1DER\s0) encoding values.
.PP
The \fBX509_NAME_cmp()\fR function compares two \fBX509_NAME\fR objects indicated by
parameters \fBa\fR and \fBb\fR. The comparison is based on the \fBmemcmp\fR result of
the canonical (\s-1DER\s0) encoding values of the two objects. \fBi2d_X509_NAME\fR\|(3)
has a more detailed description of the \s-1DER\s0 encoding of the \fBX509_NAME\fR structure.
.PP
The \fBX509_issuer_and_serial_cmp()\fR function compares the serial number and issuer
values in the given \fBX509\fR objects \fBa\fR and \fBb\fR.
.PP
The \fBX509_issuer_name_cmp()\fR, \fBX509_subject_name_cmp()\fR and \fBX509_CRL_cmp()\fR functions
are effectively wrappers of the \fBX509_NAME_cmp()\fR function. These functions compare
issuer names and subject names of the  objects, or issuers of \fBX509_CRL\fR
objects, respectively.
.IX Xref "509"
.PP
The \fBX509_CRL_match()\fR function compares two \fBX509_CRL\fR objects. Unlike the
\&\fBX509_CRL_cmp()\fR function, this function compares the whole \s-1CRL\s0 content instead
of just the issuer name.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
Like common memory comparison functions, the \fBX509\fR comparison functions return
an integer less than, equal to, or greater than zero if object \fBa\fR is found to
be less than, to match, or be greater than object \fBb\fR, respectively.
.PP
\&\fBX509_NAME_cmp()\fR, \fBX509_issuer_and_serial_cmp()\fR, \fBX509_issuer_name_cmp()\fR,
\&\fBX509_subject_name_cmp()\fR and \fBX509_CRL_cmp()\fR may return \fB\-2\fR to indicate an error.
.SH "NOTES"
.IX Header "NOTES"
These functions in fact utilize the underlying \fBmemcmp\fR of the C library to do
the comparison job. Data to be compared varies from \s-1DER\s0 encoding data, hash
value or \fB\s-1ASN1_STRING\s0\fR. The sign of the comparison can be used to order the
objects but it does not have a special meaning in some cases.
.PP
\&\fBX509_NAME_cmp()\fR and wrappers utilize the value \fB\-2\fR to indicate errors in some
circumstances, which could cause confusion for the applications.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBi2d_X509_NAME\fR\|(3), \fBi2d_X509\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.