1=pod
2
3=head1 NAME
4
5OCSP_request_add1_nonce, OCSP_basic_add1_nonce, OCSP_check_nonce, OCSP_copy_nonce - OCSP nonce functions
6
7=head1 SYNOPSIS
8
9 #include <openssl/ocsp.h>
10
11 int OCSP_request_add1_nonce(OCSP_REQUEST *req, unsigned char *val, int len);
12 int OCSP_basic_add1_nonce(OCSP_BASICRESP *resp, unsigned char *val, int len);
13 int OCSP_copy_nonce(OCSP_BASICRESP *resp, OCSP_REQUEST *req);
14 int OCSP_check_nonce(OCSP_REQUEST *req, OCSP_BASICRESP *resp);
15
16=head1 DESCRIPTION
17
18OCSP_request_add1_nonce() adds a nonce of value B<val> and length B<len> to
19OCSP request B<req>. If B<val> is B<NULL> a random nonce is used. If B<len>
20is zero or negative a default length will be used (currently 16 bytes).
21
22OCSP_basic_add1_nonce() is identical to OCSP_request_add1_nonce() except
23it adds a nonce to OCSP basic response B<resp>.
24
25OCSP_check_nonce() compares the nonce value in B<req> and B<resp>.
26
27OCSP_copy_nonce() copies any nonce value present in B<req> to B<resp>.
28
29=head1 RETURN VALUES
30
31OCSP_request_add1_nonce() and OCSP_basic_add1_nonce() return 1 for success
32and 0 for failure.
33
34OCSP_copy_nonce() returns 1 if a nonce was successfully copied, 2 if no nonce
35was present in B<req> and 0 if an error occurred.
36
37OCSP_check_nonce() returns the result of the nonce comparison between B<req>
38and B<resp>. The return value indicates the result of the comparison.  If
39nonces are present and equal 1 is returned. If the nonces are absent 2 is
40returned. If a nonce is present in the response only 3 is returned. If nonces
41are present and unequal 0 is returned. If the nonce is present in the request
42only then -1 is returned.
43
44=head1 NOTES
45
46For most purposes the nonce value in a request is set to a random value so
47the B<val> parameter in OCSP_request_add1_nonce() is usually NULL.
48
49An OCSP nonce is typically added to an OCSP request to thwart replay attacks
50by checking the same nonce value appears in the response.
51
52Some responders may include a nonce in all responses even if one is not
53supplied.
54
55Some responders cache OCSP responses and do not sign each response for
56performance reasons. As a result they do not support nonces.
57
58The return values of OCSP_check_nonce() can be checked to cover each case.  A
59positive return value effectively indicates success: nonces are both present
60and match, both absent or present in the response only. A nonzero return
61additionally covers the case where the nonce is present in the request only:
62this will happen if the responder doesn't support nonces. A zero return value
63indicates present and mismatched nonces: this should be treated as an error
64condition.
65
66=head1 SEE ALSO
67
68L<crypto(7)>,
69L<OCSP_cert_to_id(3)>,
70L<OCSP_REQUEST_new(3)>,
71L<OCSP_resp_find_status(3)>,
72L<OCSP_response_status(3)>,
73L<OCSP_sendreq_new(3)>
74
75=head1 COPYRIGHT
76
77Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
78
79Licensed under the Apache License 2.0 (the "License").  You may not use
80this file except in compliance with the License.  You can obtain a copy
81in the file LICENSE in the source distribution or at
82L<https://www.openssl.org/source/license.html>.
83
84=cut
85