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/* rsa_sha1.c
*
* Signatures using RSA and SHA1.
*/
/* nettle, low-level cryptographics library
*
* Copyright (C) 2001 Niels Möller
*
* The nettle library is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2.1 of the License, or (at your
* option) any later version.
*
* The nettle library is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with the nettle library; see the file COPYING.LIB. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
* MA 02111-1307, USA.
*/
#if HAVE_CONFIG_H
#include "config.h"
#endif
#if HAVE_LIBGMP
#include "rsa.h"
#include "bignum.h"
#include <assert.h>
#include <stdlib.h>
#include <string.h>
/* Forward declarations */
static void
pkcs1_encode_sha1(mpz_t m, unsigned length, struct sha1_ctx *hash);
void
rsa_sha1_sign(struct rsa_private_key *key,
struct sha1_ctx *hash,
mpz_t s)
{
assert(key->pub.size >= 45);
pkcs1_encode_sha1(s, key->pub.size - 1, hash);
rsa_compute_root(key, s, s);
}
int
rsa_sha1_verify(struct rsa_public_key *key,
struct sha1_ctx *hash,
const mpz_t s)
{
int res;
mpz_t m1;
mpz_t m2;
if ( (mpz_sgn(s) <= 0)
|| (mpz_cmp(s, key->n) >= 0) )
return 0;
mpz_init(m1); mpz_init(m2);
mpz_powm(m1, s, key->e, key->n);
/* FIXME: Is it cheaper to convert s to a string and check that? */
pkcs1_encode_sha1(m2, key->size - 1, hash);
res = !mpz_cmp(m1, m2);
mpz_clear(m1); mpz_clear(m2);
return res;
}
/* From pkcs-1v2
*
* id-sha1 OBJECT IDENTIFIER ::=
* {iso(1) identified-organization(3) oiw(14) secsig(3)
* algorithms(2) 26}
*
* The default hash function is SHA-1:
* sha1Identifier ::= AlgorithmIdentifier {id-sha1, NULL}
*/
static const uint8_t sha1_prefix[] =
{
/* 15 octets prefix, 20 octets hash, total 35 */
0x30, 33, /* SEQUENCE */
0x30, 9, /* SEQUENCE */
0x06, 5, /* OBJECT IDENTIFIER */
0x2b, 0x0e, 0x03, 0x02, 0x1a,
0x05, 0, /* NULL */
0x04, 20 /* OCTET STRING */
/* Here comes the raw hash value */
};
static void
pkcs1_encode_sha1(mpz_t m, unsigned length, struct sha1_ctx *hash)
{
uint8_t *em = alloca(length);
unsigned i;
assert(length >= SHA1_DIGEST_SIZE);
i = length - SHA1_DIGEST_SIZE;
sha1_digest(hash, SHA1_DIGEST_SIZE, em + i);
assert(i >= sizeof(sha1_prefix));
i -= sizeof(sha1_prefix);
memcpy(em + i, sha1_prefix, sizeof(sha1_prefix));
assert(i);
em[--i] = 0;
assert(i >= 9);
em[0] = 1;
memset(em + 1, 0xff, i - 1);
nettle_mpz_set_str_256(m, length, em);
}
#endif /* HAVE_LIBGMP */
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