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_check_nonce(OCSP_REQUEST *req, OCSP_BASICRESP *resp); int
OCSP_copy_nonce(OCSP_BASICRESP *resp, OCSP_REQUEST *req);

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. 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). 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. 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. 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.

RETURN VALUES

OCSP_request_add1_nonce() and OCSP_basic_add1_nonce() return 1 for success or 0 for failure. OCSP_copy_nonce() returns 1 if a nonce was successfully copied, 2 if no nonce was present in req, or 0 if an error occurred. 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.

SEE ALSO

OCSP_cert_to_id(3), OCSP_REQUEST_new(3), OCSP_resp_find_status(3), OCSP_response_status(3), OCSP_sendreq_new(3)

HISTORY

These functions first appeared in OpenSSL 0.9.7 and have been available since OpenBSD 3.2.