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.\" ========================================================================
.\"
.IX Title "OCSP_request_add1_nonce 3"
.TH OCSP_request_add1_nonce 3 "2020-12-10" "1.1.1i" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
OCSP_request_add1_nonce, OCSP_basic_add1_nonce, OCSP_check_nonce, OCSP_copy_nonce \- OCSP nonce functions
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/ocsp.h>
\&
\& int OCSP_request_add1_nonce(OCSP_REQUEST *req, unsigned char *val, int len);
\& int OCSP_basic_add1_nonce(OCSP_BASICRESP *resp, unsigned char *val, int len);
\& int OCSP_copy_nonce(OCSP_BASICRESP *resp, OCSP_REQUEST *req);
\& int OCSP_check_nonce(OCSP_REQUEST *req, OCSP_BASICRESP *resp);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBOCSP_request_add1_nonce()\fR adds a nonce of value \fBval\fR and length \fBlen\fR to
\&\s-1OCSP\s0 request \fBreq\fR. If \fBval\fR is \fB\s-1NULL\s0\fR a random nonce is used. If \fBlen\fR
is zero or negative a default length will be used (currently 16 bytes).
.PP
\&\fBOCSP_basic_add1_nonce()\fR is identical to \fBOCSP_request_add1_nonce()\fR except
it adds a nonce to \s-1OCSP\s0 basic response \fBresp\fR.
.PP
\&\fBOCSP_check_nonce()\fR compares the nonce value in \fBreq\fR and \fBresp\fR.
.PP
\&\fBOCSP_copy_nonce()\fR copies any nonce value present in \fBreq\fR to \fBresp\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBOCSP_request_add1_nonce()\fR and \fBOCSP_basic_add1_nonce()\fR return 1 for success
and 0 for failure.
.PP
\&\fBOCSP_copy_nonce()\fR returns 1 if a nonce was successfully copied, 2 if no nonce
was present in \fBreq\fR and 0 if an error occurred.
.PP
\&\fBOCSP_check_nonce()\fR returns the result of the nonce comparison between \fBreq\fR
and \fBresp\fR. The return value indicates the result of the comparison.  If
nonces are present and equal 1 is returned. If the nonces are absent 2 is
returned. If a nonce is present in the response only 3 is returned. If nonces
are present and unequal 0 is returned. If the nonce is present in the request
only then \-1 is returned.
.SH "NOTES"
.IX Header "NOTES"
For most purposes the nonce value in a request is set to a random value so
the \fBval\fR parameter in \fBOCSP_request_add1_nonce()\fR is usually \s-1NULL.\s0
.PP
An \s-1OCSP\s0 nonce is typically added to an \s-1OCSP\s0 request to thwart replay attacks
by checking the same nonce value appears in the response.
.PP
Some responders may include a nonce in all responses even if one is not
supplied.
.PP
Some responders cache \s-1OCSP\s0 responses and do not sign each response for
performance reasons. As a result they do not support nonces.
.PP
The return values of \fBOCSP_check_nonce()\fR can be checked to cover each case.  A
positive return value effectively indicates success: nonces are both present
and match, both absent or present in the response only. A nonzero return
additionally covers the case where the nonce is present in the request only:
this will happen if the responder doesn't support nonces. A zero return value
indicates present and mismatched nonces: this should be treated as an error
condition.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBcrypto\fR\|(7),
\&\fBOCSP_cert_to_id\fR\|(3),
\&\fBOCSP_REQUEST_new\fR\|(3),
\&\fBOCSP_resp_find_status\fR\|(3),
\&\fBOCSP_response_status\fR\|(3),
\&\fBOCSP_sendreq_new\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2015\-2020 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (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>.