ref: 009439541d2c6e8af2596f8fb1b4df85861fd212
dir: /third_party/boringssl/src/crypto/fipsmodule/ecdsa/ecdsa.c.inc/
/* ====================================================================
* Copyright (c) 1998-2005 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
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*
* 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
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* 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
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* ====================================================================
*
* This product includes cryptographic software written by Eric Young
* (eay@cryptsoft.com). This product includes software written by Tim
* Hudson (tjh@cryptsoft.com). */
#include <openssl/ecdsa.h>
#include <assert.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/err.h>
#include <openssl/mem.h>
#include <openssl/sha.h>
#include "../../internal.h"
#include "../bn/internal.h"
#include "../ec/internal.h"
#include "../service_indicator/internal.h"
#include "internal.h"
// digest_to_scalar interprets |digest_len| bytes from |digest| as a scalar for
// ECDSA.
static void digest_to_scalar(const EC_GROUP *group, EC_SCALAR *out,
const uint8_t *digest, size_t digest_len) {
const BIGNUM *order = EC_GROUP_get0_order(group);
size_t num_bits = BN_num_bits(order);
// Need to truncate digest if it is too long: first truncate whole bytes.
size_t num_bytes = (num_bits + 7) / 8;
if (digest_len > num_bytes) {
digest_len = num_bytes;
}
bn_big_endian_to_words(out->words, order->width, digest, digest_len);
// If it is still too long, truncate remaining bits with a shift.
if (8 * digest_len > num_bits) {
bn_rshift_words(out->words, out->words, 8 - (num_bits & 0x7), order->width);
}
// |out| now has the same bit width as |order|, but this only bounds by
// 2*|order|. Subtract the order if out of range.
//
// Montgomery multiplication accepts the looser bounds, so this isn't strictly
// necessary, but it is a cleaner abstraction and has no performance impact.
BN_ULONG tmp[EC_MAX_WORDS];
bn_reduce_once_in_place(out->words, 0 /* no carry */, order->d, tmp,
order->width);
}
int ecdsa_verify_fixed_no_self_test(const uint8_t *digest, size_t digest_len,
const uint8_t *sig, size_t sig_len,
const EC_KEY *eckey) {
const EC_GROUP *group = EC_KEY_get0_group(eckey);
const EC_POINT *pub_key = EC_KEY_get0_public_key(eckey);
if (group == NULL || pub_key == NULL || sig == NULL) {
OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_MISSING_PARAMETERS);
return 0;
}
size_t scalar_len = BN_num_bytes(EC_GROUP_get0_order(group));
EC_SCALAR r, s, u1, u2, s_inv_mont, m;
if (sig_len != 2 * scalar_len ||
!ec_scalar_from_bytes(group, &r, sig, scalar_len) ||
ec_scalar_is_zero(group, &r) ||
!ec_scalar_from_bytes(group, &s, sig + scalar_len, scalar_len) ||
ec_scalar_is_zero(group, &s)) {
OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_BAD_SIGNATURE);
return 0;
}
// s_inv_mont = s^-1 in the Montgomery domain.
if (!ec_scalar_to_montgomery_inv_vartime(group, &s_inv_mont, &s)) {
OPENSSL_PUT_ERROR(ECDSA, ERR_R_INTERNAL_ERROR);
return 0;
}
// u1 = m * s^-1 mod order
// u2 = r * s^-1 mod order
//
// |s_inv_mont| is in Montgomery form while |m| and |r| are not, so |u1| and
// |u2| will be taken out of Montgomery form, as desired.
digest_to_scalar(group, &m, digest, digest_len);
ec_scalar_mul_montgomery(group, &u1, &m, &s_inv_mont);
ec_scalar_mul_montgomery(group, &u2, &r, &s_inv_mont);
EC_JACOBIAN point;
if (!ec_point_mul_scalar_public(group, &point, &u1, &pub_key->raw, &u2)) {
OPENSSL_PUT_ERROR(ECDSA, ERR_R_EC_LIB);
return 0;
}
if (!ec_cmp_x_coordinate(group, &point, &r)) {
OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_BAD_SIGNATURE);
return 0;
}
return 1;
}
int ecdsa_verify_fixed(const uint8_t *digest, size_t digest_len,
const uint8_t *sig, size_t sig_len, const EC_KEY *key) {
boringssl_ensure_ecc_self_test();
return ecdsa_verify_fixed_no_self_test(digest, digest_len, sig, sig_len, key);
}
static int ecdsa_sign_impl(const EC_GROUP *group, int *out_retry, uint8_t *sig,
size_t *out_sig_len, size_t max_sig_len,
const EC_SCALAR *priv_key, const EC_SCALAR *k,
const uint8_t *digest, size_t digest_len) {
*out_retry = 0;
// Check that the size of the group order is FIPS compliant (FIPS 186-4
// B.5.2).
const BIGNUM *order = EC_GROUP_get0_order(group);
if (BN_num_bits(order) < 160) {
OPENSSL_PUT_ERROR(EC, EC_R_INVALID_GROUP_ORDER);
return 0;
}
size_t sig_len = 2 * BN_num_bytes(order);
if (sig_len > max_sig_len) {
OPENSSL_PUT_ERROR(EC, EC_R_BUFFER_TOO_SMALL);
return 0;
}
// Compute r, the x-coordinate of k * generator.
EC_JACOBIAN tmp_point;
EC_SCALAR r;
if (!ec_point_mul_scalar_base(group, &tmp_point, k) ||
!ec_get_x_coordinate_as_scalar(group, &r, &tmp_point)) {
return 0;
}
if (constant_time_declassify_int(ec_scalar_is_zero(group, &r))) {
*out_retry = 1;
return 0;
}
// s = priv_key * r. Note if only one parameter is in the Montgomery domain,
// |ec_scalar_mod_mul_montgomery| will compute the answer in the normal
// domain.
EC_SCALAR s;
ec_scalar_to_montgomery(group, &s, &r);
ec_scalar_mul_montgomery(group, &s, priv_key, &s);
// s = m + priv_key * r.
EC_SCALAR tmp;
digest_to_scalar(group, &tmp, digest, digest_len);
ec_scalar_add(group, &s, &s, &tmp);
// s = k^-1 * (m + priv_key * r). First, we compute k^-1 in the Montgomery
// domain. This is |ec_scalar_to_montgomery| followed by
// |ec_scalar_inv0_montgomery|, but |ec_scalar_inv0_montgomery| followed by
// |ec_scalar_from_montgomery| is equivalent and slightly more efficient.
// Then, as above, only one parameter is in the Montgomery domain, so the
// result is in the normal domain. Finally, note k is non-zero (or computing r
// would fail), so the inverse must exist.
ec_scalar_inv0_montgomery(group, &tmp, k); // tmp = k^-1 R^2
ec_scalar_from_montgomery(group, &tmp, &tmp); // tmp = k^-1 R
ec_scalar_mul_montgomery(group, &s, &s, &tmp);
if (constant_time_declassify_int(ec_scalar_is_zero(group, &s))) {
*out_retry = 1;
return 0;
}
CONSTTIME_DECLASSIFY(r.words, sizeof(r.words));
CONSTTIME_DECLASSIFY(s.words, sizeof(r.words));
size_t len;
ec_scalar_to_bytes(group, sig, &len, &r);
assert(len == sig_len / 2);
ec_scalar_to_bytes(group, sig + len, &len, &s);
assert(len == sig_len / 2);
*out_sig_len = sig_len;
return 1;
}
int ecdsa_sign_fixed_with_nonce_for_known_answer_test(
const uint8_t *digest, size_t digest_len, uint8_t *sig, size_t *out_sig_len,
size_t max_sig_len, const EC_KEY *eckey, const uint8_t *nonce,
size_t nonce_len) {
if (eckey->ecdsa_meth && eckey->ecdsa_meth->sign) {
OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_NOT_IMPLEMENTED);
return 0;
}
const EC_GROUP *group = EC_KEY_get0_group(eckey);
if (group == NULL || eckey->priv_key == NULL) {
OPENSSL_PUT_ERROR(ECDSA, ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
const EC_SCALAR *priv_key = &eckey->priv_key->scalar;
EC_SCALAR k;
if (!ec_scalar_from_bytes(group, &k, nonce, nonce_len)) {
return 0;
}
int retry_ignored;
return ecdsa_sign_impl(group, &retry_ignored, sig, out_sig_len, max_sig_len,
priv_key, &k, digest, digest_len);
}
int ecdsa_sign_fixed(const uint8_t *digest, size_t digest_len, uint8_t *sig,
size_t *out_sig_len, size_t max_sig_len,
const EC_KEY *eckey) {
boringssl_ensure_ecc_self_test();
if (eckey->ecdsa_meth && eckey->ecdsa_meth->sign) {
OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_NOT_IMPLEMENTED);
return 0;
}
const EC_GROUP *group = EC_KEY_get0_group(eckey);
if (group == NULL || eckey->priv_key == NULL) {
OPENSSL_PUT_ERROR(ECDSA, ERR_R_PASSED_NULL_PARAMETER);
return 0;
}
const BIGNUM *order = EC_GROUP_get0_order(group);
const EC_SCALAR *priv_key = &eckey->priv_key->scalar;
// Pass a SHA512 hash of the private key and digest as additional data
// into the RBG. This is a hardening measure against entropy failure.
static_assert(SHA512_DIGEST_LENGTH >= 32,
"additional_data is too large for SHA-512");
FIPS_service_indicator_lock_state();
SHA512_CTX sha;
uint8_t additional_data[SHA512_DIGEST_LENGTH];
SHA512_Init(&sha);
SHA512_Update(&sha, priv_key->words, order->width * sizeof(BN_ULONG));
SHA512_Update(&sha, digest, digest_len);
SHA512_Final(additional_data, &sha);
// Cap iterations so callers who supply invalid values as custom groups do not
// infinite loop. This does not impact valid parameters (e.g. those covered by
// FIPS) because the probability of requiring even one retry is negligible,
// let alone 32.
static const int kMaxIterations = 32;
int ret = 0;
int iters = 0;
for (;;) {
EC_SCALAR k;
if (!ec_random_nonzero_scalar(group, &k, additional_data)) {
goto out;
}
// TODO(davidben): Move this inside |ec_random_nonzero_scalar| or lower, so
// that all scalars we generate are, by default, secret.
CONSTTIME_SECRET(k.words, sizeof(k.words));
int retry;
ret = ecdsa_sign_impl(group, &retry, sig, out_sig_len, max_sig_len,
priv_key, &k, digest, digest_len);
if (ret || !retry) {
goto out;
}
iters++;
if (iters > kMaxIterations) {
OPENSSL_PUT_ERROR(ECDSA, ECDSA_R_TOO_MANY_ITERATIONS);
goto out;
}
}
out:
FIPS_service_indicator_unlock_state();
return ret;
}