=pod =head1 NAME OCSP_request_add1_nonce, OCSP_basic_add1_nonce, OCSP_check_nonce, OCSP_copy_nonce - OCSP nonce functions =head1 SYNOPSIS #include 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); =head1 DESCRIPTION OCSP_request_add1_nonce() adds a nonce of value B and length B to OCSP request B. If B is B a random nonce is used. If B 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 B. OCSP_check_nonce() compares the nonce value in B and B. OCSP_copy_nonce() copys any nonce value present in B to B. =head1 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 B and 0 if an error occurred. OCSP_check_nonce() returns the result of the nonce comparison between B and B. 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. =head1 NOTES For most purposes the nonce value in a request is set to a random value so the B 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 non-zero 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. =head1 SEE ALSO L, L, L, L, L, L =head1 COPYRIGHT Copyright 2015-2016 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 L. =cut