.\"	$OpenBSD: OCSP_request_add1_nonce.3,v 1.4 2018/03/22 21:08:22 schwarze Exp $
.\"	OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
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.Dd $Mdocdate: March 22 2018 $
.Dt OCSP_REQUEST_ADD1_NONCE 3
.Os
.Sh NAME
.Nm OCSP_request_add1_nonce ,
.Nm OCSP_basic_add1_nonce ,
.Nm OCSP_check_nonce ,
.Nm OCSP_copy_nonce
.Nd OCSP nonce functions
.Sh SYNOPSIS
.In openssl/ocsp.h
.Ft int
.Fo OCSP_request_add1_nonce
.Fa "OCSP_REQUEST *req"
.Fa "unsigned char *val"
.Fa "int len"
.Fc
.Ft int
.Fo OCSP_basic_add1_nonce
.Fa "OCSP_BASICRESP *resp"
.Fa "unsigned char *val"
.Fa "int len"
.Fc
.Ft int
.Fo OCSP_check_nonce
.Fa "OCSP_REQUEST *req"
.Fa "OCSP_BASICRESP *resp"
.Fc
.Ft int
.Fo OCSP_copy_nonce
.Fa "OCSP_BASICRESP *resp"
.Fa "OCSP_REQUEST *req"
.Fc
.Sh DESCRIPTION
An OCSP nonce is typically added to an OCSP request to thwart replay
attacks by checking the same nonce value appears in the response.
.Pp
.Fn OCSP_request_add1_nonce
adds a nonce of value
.Fa val
and length
.Fa len
to OCSP request
.Fa req .
If
.Fa val
is
.Dv NULL ,
a random nonce is used.
If
.Fa len
is zero or negative, a default length will be used (currently 16 bytes).
For most purposes the nonce value in a request is set to a random value
so the
.Fa val
parameter in
.Fn OCSP_request_add1_nonce
is usually NULL.
.Pp
.Fn OCSP_basic_add1_nonce
is identical to
.Fn OCSP_request_add1_nonce
except it adds a nonce to OCSP basic response
.Fa resp .
.Pp
.Fn OCSP_check_nonce
compares the nonce value in
.Fa req
and
.Fa resp .
.Pp
.Fn OCSP_copy_nonce
copies any nonce value present in
.Fa req
to
.Fa resp .
.Pp
Some responders may include a nonce in all responses even if one is not
supplied.
.Pp
Some responders cache OCSP responses and do not sign each response for
performance reasons.
As a result they do not support nonces.
.Sh RETURN VALUES
.Fn OCSP_request_add1_nonce
and
.Fn OCSP_basic_add1_nonce
return 1 for success or 0 for failure.
.Pp
.Fn OCSP_copy_nonce
returns 1 if a nonce was successfully copied, 2 if no nonce was
present in
.Fa req ,
or 0 if an error occurred.
.Pp
.Fn OCSP_check_nonce
returns positive values for success: 1 if nonces are present and
equal, 2 if both nonces are absent, or 3 if a nonce is present in
the response only.
A zero return value indicates that both nonces are present but
mismatch: this should be treated as an error condition.
A return value of -1 indicates that a nonce is present in the request
only: this will happen if the responder doesn't support nonces.
.Sh SEE ALSO
.Xr OCSP_cert_to_id 3 ,
.Xr OCSP_REQUEST_new 3 ,
.Xr OCSP_resp_find_status 3 ,
.Xr OCSP_response_status 3 ,
.Xr OCSP_sendreq_new 3
.Sh HISTORY
These functions first appeared in OpenSSL 0.9.7
and have been available since
.Ox 3.2 .