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OCSP_REQUEST_ADD1_NONCE(3)          OpenSSL         OCSP_REQUEST_ADD1_NONCE(3)
NAME
       OCSP_request_add1_nonce, OCSP_basic_add1_nonce, OCSP_check_nonce,
       OCSP_copy_nonce - OCSP nonce functions
SYNOPSIS
        #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);
DESCRIPTION
       OCSP_request_add1_nonce() adds a nonce of value val and length len to
       OCSP request req. If val is NULL a random nonce is used. If len is zero
       or negative a default length will be used (currently 16 bytes).
       OCSP_basic_add1_nonce() is identical to OCSP_request_add1_nonce()
       except it adds a nonce to OCSP basic response resp.
       OCSP_check_nonce() compares the nonce value in req and resp.
       OCSP_copy_nonce() copies any nonce value present in req to resp.
RETURN VALUES
       OCSP_request_add1_nonce() and OCSP_basic_add1_nonce() return 1 for
       success and 0 for failure.
       OCSP_copy_nonce() returns 1 if a nonce was successfully copied, 2 if no
       nonce was present in req and 0 if an error occurred.
       OCSP_check_nonce() returns the result of the nonce comparison between
       req and resp. 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.
NOTES
       For most purposes the nonce value in a request is set to a random value
       so the val parameter in OCSP_request_add1_nonce() is usually NULL.
       An OCSP nonce is typically added to an OCSP request to thwart replay
       attacks by checking the same nonce value appears in the response.
       Some responders may include a nonce in all responses even if one is not
       supplied.
       Some responders cache OCSP responses and do not sign each response for
       performance reasons. As a result they do not support nonces.
       The return values of OCSP_check_nonce() 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.
SEE ALSO
       crypto(7), OCSP_cert_to_id(3), OCSP_REQUEST_new(3),
       OCSP_resp_find_status(3), OCSP_response_status(3), OCSP_sendreq_new(3)
COPYRIGHT
       Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
       Licensed under the OpenSSL license (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>;.
1.1.1k                            2021-03-25        OCSP_REQUEST_ADD1_NONCE(3)