2018-07-30 02:07:02 +00:00
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/* ====================================================================
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* Copyright (c) 1998-2005 The OpenSSL Project. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. All advertising materials mentioning features or use of this
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* software must display the following acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
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*
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* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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* endorse or promote products derived from this software without
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* prior written permission. For written permission, please contact
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* openssl-core@OpenSSL.org.
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*
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* 5. Products derived from this software may not be called "OpenSSL"
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* nor may "OpenSSL" appear in their names without prior written
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* permission of the OpenSSL Project.
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*
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* 6. Redistributions of any form whatsoever must retain the following
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* acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
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*
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* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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* ====================================================================
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*
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* This product includes cryptographic software written by Eric Young
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* (eay@cryptsoft.com). This product includes software written by Tim
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* Hudson (tjh@cryptsoft.com). */
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#include <openssl/ecdsa.h>
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#include <assert.h>
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#include <string.h>
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#include <openssl/bn.h>
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#include <openssl/err.h>
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#include <openssl/mem.h>
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#include <openssl/sha.h>
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#include <openssl/type_check.h>
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#include "../bn/internal.h"
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#include "../ec/internal.h"
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#include "../../internal.h"
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// digest_to_scalar interprets |digest_len| bytes from |digest| as a scalar for
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// ECDSA. Note this value is not fully reduced modulo the order, only the
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// correct number of bits.
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2019-12-31 13:08:08 +00:00
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static void digest_to_scalar(const EC_GROUP *group, EC_SCALAR *out,
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2018-07-30 02:07:02 +00:00
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const uint8_t *digest, size_t digest_len) {
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const BIGNUM *order = &group->order;
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size_t num_bits = BN_num_bits(order);
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// Need to truncate digest if it is too long: first truncate whole bytes.
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2019-12-31 13:08:08 +00:00
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size_t num_bytes = (num_bits + 7) / 8;
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if (digest_len > num_bytes) {
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digest_len = num_bytes;
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2018-07-30 02:07:02 +00:00
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}
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OPENSSL_memset(out, 0, sizeof(EC_SCALAR));
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for (size_t i = 0; i < digest_len; i++) {
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out->bytes[i] = digest[digest_len - 1 - i];
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}
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2019-12-31 13:08:08 +00:00
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// If it is still too long, truncate remaining bits with a shift.
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2018-07-30 02:07:02 +00:00
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if (8 * digest_len > num_bits) {
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2019-12-31 13:08:08 +00:00
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bn_rshift_words(out->words, out->words, 8 - (num_bits & 0x7), order->width);
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2018-07-30 02:07:02 +00:00
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}
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2019-12-31 13:08:08 +00:00
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// |out| now has the same bit width as |order|, but this only bounds by
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// 2*|order|. Subtract the order if out of range.
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2018-07-30 02:07:02 +00:00
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//
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2019-12-31 13:08:08 +00:00
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// Montgomery multiplication accepts the looser bounds, so this isn't strictly
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// necessary, but it is a cleaner abstraction and has no performance impact.
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BN_ULONG tmp[EC_MAX_WORDS];
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bn_reduce_once_in_place(out->words, 0 /* no carry */, order->d, tmp,
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order->width);
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2018-07-30 02:07:02 +00:00
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}
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ECDSA_SIG *ECDSA_SIG_new(void) {
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ECDSA_SIG *sig = OPENSSL_malloc(sizeof(ECDSA_SIG));
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if (sig == NULL) {
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return NULL;
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}
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sig->r = BN_new();
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sig->s = BN_new();
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if (sig->r == NULL || sig->s == NULL) {
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ECDSA_SIG_free(sig);
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return NULL;
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}
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return sig;
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}
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void ECDSA_SIG_free(ECDSA_SIG *sig) {
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if (sig == NULL) {
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return;
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}
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BN_free(sig->r);
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BN_free(sig->s);
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OPENSSL_free(sig);
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}
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void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **out_r,
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const BIGNUM **out_s) {
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if (out_r != NULL) {
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*out_r = sig->r;
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}
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if (out_s != NULL) {
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*out_s = sig->s;
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}
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}
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int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s) {
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if (r == NULL || s == NULL) {
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return 0;
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}
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BN_free(sig->r);
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BN_free(sig->s);
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sig->r = r;
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sig->s = s;
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return 1;
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}
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int ECDSA_do_verify(const uint8_t *digest, size_t digest_len,
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const ECDSA_SIG *sig, const EC_KEY *eckey) {
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const EC_GROUP *group = EC_KEY_get0_group(eckey);
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const EC_POINT *pub_key = EC_KEY_get0_public_key(eckey);
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if (group == NULL || pub_key == NULL || sig == NULL) {
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OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_MISSING_PARAMETERS);
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return 0;
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}
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2019-12-31 13:08:08 +00:00
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EC_SCALAR r, s, u1, u2, s_inv_mont, m;
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2018-07-30 02:07:02 +00:00
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if (BN_is_zero(sig->r) ||
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!ec_bignum_to_scalar(group, &r, sig->r) ||
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BN_is_zero(sig->s) ||
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!ec_bignum_to_scalar(group, &s, sig->s)) {
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OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_BAD_SIGNATURE);
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2019-12-31 13:08:08 +00:00
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return 0;
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2018-07-30 02:07:02 +00:00
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}
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2019-12-31 13:08:08 +00:00
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// s_inv_mont = s^-1 in the Montgomery domain. This is
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ec_scalar_inv_montgomery_vartime(group, &s_inv_mont, &s);
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2018-07-30 02:07:02 +00:00
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// u1 = m * s^-1 mod order
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// u2 = r * s^-1 mod order
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//
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// |s_inv_mont| is in Montgomery form while |m| and |r| are not, so |u1| and
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// |u2| will be taken out of Montgomery form, as desired.
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digest_to_scalar(group, &m, digest, digest_len);
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2019-12-31 13:08:08 +00:00
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ec_scalar_mul_montgomery(group, &u1, &m, &s_inv_mont);
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ec_scalar_mul_montgomery(group, &u2, &r, &s_inv_mont);
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2018-07-30 02:07:02 +00:00
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2019-12-31 13:08:08 +00:00
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EC_RAW_POINT point;
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if (!ec_point_mul_scalar_public(group, &point, &u1, &pub_key->raw, &u2)) {
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2018-07-30 02:07:02 +00:00
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OPENSSL_PUT_ERROR(ECDSA, ERR_R_EC_LIB);
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2019-12-31 13:08:08 +00:00
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return 0;
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2018-07-30 02:07:02 +00:00
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}
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2019-12-31 13:08:08 +00:00
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if (!ec_cmp_x_coordinate(group, &point, &r)) {
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2018-07-30 02:07:02 +00:00
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OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_BAD_SIGNATURE);
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2019-12-31 13:08:08 +00:00
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return 0;
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2018-07-30 02:07:02 +00:00
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}
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2019-12-31 13:08:08 +00:00
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return 1;
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2018-07-30 02:07:02 +00:00
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}
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2019-12-31 13:08:08 +00:00
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static int ecdsa_sign_setup(const EC_KEY *eckey, EC_SCALAR *out_kinv_mont,
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EC_SCALAR *out_r, const uint8_t *digest,
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size_t digest_len, const EC_SCALAR *priv_key) {
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2018-07-30 02:07:02 +00:00
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// Check that the size of the group order is FIPS compliant (FIPS 186-4
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// B.5.2).
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2019-12-31 13:08:08 +00:00
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const EC_GROUP *group = EC_KEY_get0_group(eckey);
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const BIGNUM *order = EC_GROUP_get0_order(group);
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2018-07-30 02:07:02 +00:00
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if (BN_num_bits(order) < 160) {
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OPENSSL_PUT_ERROR(ECDSA, EC_R_INVALID_GROUP_ORDER);
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2019-12-31 13:08:08 +00:00
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return 0;
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2018-07-30 02:07:02 +00:00
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}
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2019-12-31 13:08:08 +00:00
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int ret = 0;
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EC_SCALAR k;
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EC_RAW_POINT tmp_point;
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2018-07-30 02:07:02 +00:00
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do {
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// Include the private key and message digest in the k generation.
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if (eckey->fixed_k != NULL) {
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if (!ec_bignum_to_scalar(group, &k, eckey->fixed_k)) {
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goto err;
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}
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} else {
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// Pass a SHA512 hash of the private key and digest as additional data
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// into the RBG. This is a hardening measure against entropy failure.
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2019-12-31 13:08:08 +00:00
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OPENSSL_STATIC_ASSERT(SHA512_DIGEST_LENGTH >= 32,
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"additional_data is too large for SHA-512");
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2018-07-30 02:07:02 +00:00
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SHA512_CTX sha;
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uint8_t additional_data[SHA512_DIGEST_LENGTH];
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SHA512_Init(&sha);
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2019-12-31 13:08:08 +00:00
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SHA512_Update(&sha, priv_key->words, order->width * sizeof(BN_ULONG));
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2018-07-30 02:07:02 +00:00
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SHA512_Update(&sha, digest, digest_len);
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SHA512_Final(additional_data, &sha);
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if (!ec_random_nonzero_scalar(group, &k, additional_data)) {
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goto err;
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}
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}
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2019-12-31 13:08:08 +00:00
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// Compute k^-1 in the Montgomery domain. This is |ec_scalar_to_montgomery|
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// followed by |ec_scalar_inv_montgomery|, but |ec_scalar_inv_montgomery|
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// followed by |ec_scalar_from_montgomery| is equivalent and slightly more
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// efficient.
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ec_scalar_inv_montgomery(group, out_kinv_mont, &k);
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ec_scalar_from_montgomery(group, out_kinv_mont, out_kinv_mont);
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2018-07-30 02:07:02 +00:00
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// Compute r, the x-coordinate of generator * k.
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2019-12-31 13:08:08 +00:00
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if (!ec_point_mul_scalar_base(group, &tmp_point, &k) ||
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!ec_get_x_coordinate_as_scalar(group, out_r, &tmp_point)) {
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2018-07-30 02:07:02 +00:00
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goto err;
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}
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2019-12-31 13:08:08 +00:00
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} while (ec_scalar_is_zero(group, out_r));
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2018-07-30 02:07:02 +00:00
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ret = 1;
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err:
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OPENSSL_cleanse(&k, sizeof(k));
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return ret;
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}
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ECDSA_SIG *ECDSA_do_sign(const uint8_t *digest, size_t digest_len,
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const EC_KEY *eckey) {
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if (eckey->ecdsa_meth && eckey->ecdsa_meth->sign) {
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OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_NOT_IMPLEMENTED);
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return NULL;
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}
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const EC_GROUP *group = EC_KEY_get0_group(eckey);
|
2019-12-31 13:08:08 +00:00
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if (group == NULL || eckey->priv_key == NULL) {
|
2018-07-30 02:07:02 +00:00
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OPENSSL_PUT_ERROR(ECDSA, ERR_R_PASSED_NULL_PARAMETER);
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return NULL;
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}
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const BIGNUM *order = EC_GROUP_get0_order(group);
|
2019-12-31 13:08:08 +00:00
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const EC_SCALAR *priv_key = &eckey->priv_key->scalar;
|
2018-07-30 02:07:02 +00:00
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int ok = 0;
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ECDSA_SIG *ret = ECDSA_SIG_new();
|
2019-12-31 13:08:08 +00:00
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EC_SCALAR kinv_mont, r_mont, s, m, tmp;
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if (ret == NULL) {
|
2018-07-30 02:07:02 +00:00
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OPENSSL_PUT_ERROR(ECDSA, ERR_R_MALLOC_FAILURE);
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return NULL;
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}
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digest_to_scalar(group, &m, digest, digest_len);
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for (;;) {
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2019-12-31 13:08:08 +00:00
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if (!ecdsa_sign_setup(eckey, &kinv_mont, &r_mont, digest, digest_len,
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priv_key) ||
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!bn_set_words(ret->r, r_mont.words, order->width)) {
|
2018-07-30 02:07:02 +00:00
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goto err;
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}
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// Compute priv_key * r (mod order). Note if only one parameter is in the
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2019-12-31 13:08:08 +00:00
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// Montgomery domain, |ec_scalar_mod_mul_montgomery| will compute the answer
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// in the normal domain.
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ec_scalar_to_montgomery(group, &r_mont, &r_mont);
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ec_scalar_mul_montgomery(group, &s, priv_key, &r_mont);
|
2018-07-30 02:07:02 +00:00
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// Compute tmp = m + priv_key * r.
|
2019-12-31 13:08:08 +00:00
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ec_scalar_add(group, &tmp, &m, &s);
|
2018-07-30 02:07:02 +00:00
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// Finally, multiply s by k^-1. That was retained in Montgomery form, so the
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// same technique as the previous multiplication works.
|
2019-12-31 13:08:08 +00:00
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ec_scalar_mul_montgomery(group, &s, &tmp, &kinv_mont);
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if (!bn_set_words(ret->s, s.words, order->width)) {
|
2018-07-30 02:07:02 +00:00
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goto err;
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}
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if (!BN_is_zero(ret->s)) {
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// s != 0 => we have a valid signature
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break;
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}
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}
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ok = 1;
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|
|
|
|
|
err:
|
|
|
|
if (!ok) {
|
|
|
|
ECDSA_SIG_free(ret);
|
|
|
|
ret = NULL;
|
|
|
|
}
|
|
|
|
OPENSSL_cleanse(&kinv_mont, sizeof(kinv_mont));
|
|
|
|
OPENSSL_cleanse(&r_mont, sizeof(r_mont));
|
|
|
|
OPENSSL_cleanse(&s, sizeof(s));
|
|
|
|
OPENSSL_cleanse(&tmp, sizeof(tmp));
|
|
|
|
OPENSSL_cleanse(&m, sizeof(m));
|
|
|
|
return ret;
|
|
|
|
}
|