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openssl1.0/crypto/ecdsa/ecs_ossl.c

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/* crypto/ecdsa/ecs_ossl.c */
/*
* Written by Nils Larsch for the OpenSSL project
*/
/* ====================================================================
* Copyright (c) 1998-2018 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@OpenSSL.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* This product includes cryptographic software written by Eric Young
* (eay@cryptsoft.com). This product includes software written by Tim
* Hudson (tjh@cryptsoft.com).
*
*/
#include "ecs_locl.h"
#include <openssl/err.h>
#include <openssl/obj_mac.h>
#include <openssl/bn.h>
#include "bn_int.h"
static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen,
const BIGNUM *, const BIGNUM *,
EC_KEY *eckey);
static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
BIGNUM **rp);
static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
const ECDSA_SIG *sig, EC_KEY *eckey);
static ECDSA_METHOD openssl_ecdsa_meth = {
"OpenSSL ECDSA method",
ecdsa_do_sign,
ecdsa_sign_setup,
ecdsa_do_verify,
#if 0
NULL, /* init */
NULL, /* finish */
#endif
0, /* flags */
NULL /* app_data */
};
const ECDSA_METHOD *ECDSA_OpenSSL(void)
{
return &openssl_ecdsa_meth;
}
static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
BIGNUM **rp)
{
BN_CTX *ctx = NULL;
BIGNUM *k = NULL, *r = NULL, *order = NULL, *X = NULL;
EC_POINT *tmp_point = NULL;
const EC_GROUP *group;
int ret = 0;
int order_bits;
if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
if (ctx_in == NULL) {
if ((ctx = BN_CTX_new()) == NULL) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
return 0;
}
} else
ctx = ctx_in;
k = BN_new(); /* this value is later returned in *kinvp */
r = BN_new(); /* this value is later returned in *rp */
order = BN_new();
X = BN_new();
if (!k || !r || !order || !X) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
goto err;
}
if ((tmp_point = EC_POINT_new(group)) == NULL) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
goto err;
}
if (!EC_GROUP_get_order(group, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
goto err;
}
/* Preallocate space */
order_bits = BN_num_bits(order);
if (!BN_set_bit(k, order_bits)
|| !BN_set_bit(r, order_bits)
|| !BN_set_bit(X, order_bits))
goto err;
do {
/* get random k */
do
if (!BN_rand_range(k, order)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,
ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);
goto err;
}
while (BN_is_zero(k)) ;
/*
* We do not want timing information to leak the length of k, so we
* compute G*k using an equivalent scalar of fixed bit-length.
*
* We unconditionally perform both of these additions to prevent a
* small timing information leakage. We then choose the sum that is
* one bit longer than the order. This guarantees the code
* path used in the constant time implementations elsewhere.
*
* TODO: revisit the BN_copy aiming for a memory access agnostic
* conditional copy.
*/
if (!BN_add(r, k, order)
|| !BN_add(X, r, order)
|| !BN_copy(k, BN_num_bits(r) > order_bits ? r : X))
goto err;
/* compute r the x-coordinate of generator * k */
if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
goto err;
}
if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
NID_X9_62_prime_field) {
if (!EC_POINT_get_affine_coordinates_GFp
(group, tmp_point, X, NULL, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
goto err;
}
}
#ifndef OPENSSL_NO_EC2M
else { /* NID_X9_62_characteristic_two_field */
if (!EC_POINT_get_affine_coordinates_GF2m(group,
tmp_point, X, NULL,
ctx)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
goto err;
}
}
#endif
if (!BN_nnmod(r, X, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
goto err;
}
}
while (BN_is_zero(r));
/* compute the inverse of k */
if (EC_GROUP_get_mont_data(group) != NULL) {
/*
* We want inverse in constant time, therefore we utilize the fact
* order must be prime and use Fermats Little Theorem instead.
*/
if (!BN_set_word(X, 2)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
goto err;
}
if (!BN_mod_sub(X, order, X, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
goto err;
}
BN_set_flags(X, BN_FLG_CONSTTIME);
if (!BN_mod_exp_mont_consttime
(k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
goto err;
}
} else {
if (!BN_mod_inverse(k, k, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
goto err;
}
}
/* clear old values if necessary */
if (*rp != NULL)
BN_clear_free(*rp);
if (*kinvp != NULL)
BN_clear_free(*kinvp);
/* save the pre-computed values */
*rp = r;
*kinvp = k;
ret = 1;
err:
if (!ret) {
if (k != NULL)
BN_clear_free(k);
if (r != NULL)
BN_clear_free(r);
}
if (ctx_in == NULL)
BN_CTX_free(ctx);
if (order != NULL)
BN_free(order);
if (tmp_point != NULL)
EC_POINT_free(tmp_point);
if (X)
BN_clear_free(X);
return (ret);
}
static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
const BIGNUM *in_kinv, const BIGNUM *in_r,
EC_KEY *eckey)
{
int ok = 0, i;
BIGNUM *kinv = NULL, *s, *m = NULL, *order = NULL;
const BIGNUM *ckinv;
BN_CTX *ctx = NULL;
const EC_GROUP *group;
ECDSA_SIG *ret;
ECDSA_DATA *ecdsa;
const BIGNUM *priv_key;
BN_MONT_CTX *mont_data;
ecdsa = ecdsa_check(eckey);
group = EC_KEY_get0_group(eckey);
priv_key = EC_KEY_get0_private_key(eckey);
if (group == NULL || priv_key == NULL || ecdsa == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);
return NULL;
}
ret = ECDSA_SIG_new();
if (!ret) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
return NULL;
}
s = ret->s;
if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
(m = BN_new()) == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
goto err;
}
if (!EC_GROUP_get_order(group, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
goto err;
}
mont_data = EC_GROUP_get_mont_data(group);
i = BN_num_bits(order);
/*
* Need to truncate digest if it is too long: first truncate whole bytes.
*/
if (8 * dgst_len > i)
dgst_len = (i + 7) / 8;
if (!BN_bin2bn(dgst, dgst_len, m)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}
/* If still too long truncate remaining bits with a shift */
if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}
do {
if (in_kinv == NULL || in_r == NULL) {
if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_ECDSA_LIB);
goto err;
}
ckinv = kinv;
} else {
ckinv = in_kinv;
if (BN_copy(ret->r, in_r) == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
goto err;
}
}
/*
* With only one multiplicant being in Montgomery domain
* multiplication yields real result without post-conversion.
* Also note that all operations but last are performed with
* zero-padded vectors. Last operation, BN_mod_mul_montgomery
* below, returns user-visible value with removed zero padding.
*/
if (!bn_to_mont_fixed_top(s, ret->r, mont_data, ctx)
|| !bn_mul_mont_fixed_top(s, s, priv_key, mont_data, ctx)) {
goto err;
}
if (!bn_mod_add_fixed_top(s, s, m, order)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}
/*
* |s| can still be larger than modulus, because |m| can be. In
* such case we count on Montgomery reduction to tie it up.
*/
if (!bn_to_mont_fixed_top(s, s, mont_data, ctx)
|| !BN_mod_mul_montgomery(s, s, ckinv, mont_data, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
goto err;
}
if (BN_is_zero(s)) {
/*
* if kinv and r have been supplied by the caller don't to
* generate new kinv and r values
*/
if (in_kinv != NULL && in_r != NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
ECDSA_R_NEED_NEW_SETUP_VALUES);
goto err;
}
} else
/* s != 0 => we have a valid signature */
break;
}
while (1);
ok = 1;
err:
if (!ok) {
ECDSA_SIG_free(ret);
ret = NULL;
}
if (ctx)
BN_CTX_free(ctx);
if (m)
BN_clear_free(m);
if (order)
BN_free(order);
if (kinv)
BN_clear_free(kinv);
return ret;
}
static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
const ECDSA_SIG *sig, EC_KEY *eckey)
{
int ret = -1, i;
BN_CTX *ctx;
BIGNUM *order, *u1, *u2, *m, *X;
EC_POINT *point = NULL;
const EC_GROUP *group;
const EC_POINT *pub_key;
/* check input values */
if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
(pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);
return -1;
}
ctx = BN_CTX_new();
if (!ctx) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
return -1;
}
BN_CTX_start(ctx);
order = BN_CTX_get(ctx);
u1 = BN_CTX_get(ctx);
u2 = BN_CTX_get(ctx);
m = BN_CTX_get(ctx);
X = BN_CTX_get(ctx);
if (!X) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
goto err;
}
if (!EC_GROUP_get_order(group, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
goto err;
}
if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);
ret = 0; /* signature is invalid */
goto err;
}
/* calculate tmp1 = inv(S) mod order */
if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
goto err;
}
/* digest -> m */
i = BN_num_bits(order);
/*
* Need to truncate digest if it is too long: first truncate whole bytes.
*/
if (8 * dgst_len > i)
dgst_len = (i + 7) / 8;
if (!BN_bin2bn(dgst, dgst_len, m)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
goto err;
}
/* If still too long truncate remaining bits with a shift */
if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
goto err;
}
/* u1 = m * tmp mod order */
if (!BN_mod_mul(u1, m, u2, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
goto err;
}
/* u2 = r * w mod q */
if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
goto err;
}
if ((point = EC_POINT_new(group)) == NULL) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
goto err;
}
if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
goto err;
}
if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
NID_X9_62_prime_field) {
if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
goto err;
}
}
#ifndef OPENSSL_NO_EC2M
else { /* NID_X9_62_characteristic_two_field */
if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
goto err;
}
}
#endif
if (!BN_nnmod(u1, X, order, ctx)) {
ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
goto err;
}
/* if the signature is correct u1 is equal to sig->r */
ret = (BN_ucmp(u1, sig->r) == 0);
err:
BN_CTX_end(ctx);
BN_CTX_free(ctx);
if (point)
EC_POINT_free(point);
return ret;
}
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