ecdsa_i31_vrfy_asn1.c

/*
 * Copyright (c) 2016 Thomas Pornin <[email protected]>
 *
 * Permission is hereby granted, free of charge, to any person obtaining 
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be 
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "inner.h"

#define FIELD_LEN   ((BR_MAX_EC_SIZE + 7) >> 3)

/* see bearssl_ec.h */
uint32_t
br_ecdsa_i31_vrfy_asn1(const br_ec_impl *impl,
	const void *hash, size_t hash_len,
	const br_ec_public_key *pk,
	const void *sig, size_t sig_len)
{
	/*
	 * We use a double-sized buffer because a malformed ASN.1 signature
	 * may trigger a size expansion when converting to "raw" format.
	 */
	unsigned char rsig[(FIELD_LEN << 2) + 24];

	if (sig_len > ((sizeof rsig) >> 1)) {
		return 0;
	}
	memcpy(rsig, sig, sig_len);
	sig_len = br_ecdsa_asn1_to_raw(rsig, sig_len);
	return br_ecdsa_i31_vrfy_raw(impl, hash, hash_len, pk, rsig, sig_len);
}