2 * Copyright 2002-2017 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 #include <openssl/err.h>
12 #include <openssl/obj_mac.h>
13 #include <openssl/bn.h>
14 #include <openssl/rand.h>
15 #include <openssl/ec.h>
18 int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
19 unsigned char *sig, unsigned int *siglen,
20 const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
23 RAND_seed(dgst, dlen);
24 s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
29 *siglen = i2d_ECDSA_SIG(s, &sig);
34 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
35 BIGNUM **kinvp, BIGNUM **rp,
36 const unsigned char *dgst, int dlen)
39 BIGNUM *k = NULL, *r = NULL, *X = NULL;
41 EC_POINT *tmp_point = NULL;
42 const EC_GROUP *group;
46 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
47 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
51 if (!EC_KEY_can_sign(eckey)) {
52 ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
57 if ((ctx = BN_CTX_new()) == NULL) {
58 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
64 k = BN_new(); /* this value is later returned in *kinvp */
65 r = BN_new(); /* this value is later returned in *rp */
67 if (k == NULL || r == NULL || X == NULL) {
68 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
71 if ((tmp_point = EC_POINT_new(group)) == NULL) {
72 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
75 order = EC_GROUP_get0_order(group);
77 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
81 /* Preallocate space */
82 order_bits = BN_num_bits(order);
83 if (!BN_set_bit(k, order_bits)
84 || !BN_set_bit(r, order_bits)
85 || !BN_set_bit(X, order_bits))
92 if (!BN_generate_dsa_nonce
93 (k, order, EC_KEY_get0_private_key(eckey), dgst, dlen,
95 ECerr(EC_F_ECDSA_SIGN_SETUP,
96 EC_R_RANDOM_NUMBER_GENERATION_FAILED);
100 if (!BN_rand_range(k, order)) {
101 ECerr(EC_F_ECDSA_SIGN_SETUP,
102 EC_R_RANDOM_NUMBER_GENERATION_FAILED);
106 while (BN_is_zero(k));
109 * We do not want timing information to leak the length of k, so we
110 * compute G*k using an equivalent scalar of fixed bit-length.
112 * We unconditionally perform both of these additions to prevent a
113 * small timing information leakage. We then choose the sum that is
114 * one bit longer than the order. This guarantees the code
115 * path used in the constant time implementations elsewhere.
117 * TODO: revisit the BN_copy aiming for a memory access agnostic
120 if (!BN_add(r, k, order)
121 || !BN_add(X, r, order)
122 || !BN_copy(k, BN_num_bits(r) > order_bits ? r : X))
125 /* compute r the x-coordinate of generator * k */
126 if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
127 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
130 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
131 NID_X9_62_prime_field) {
132 if (!EC_POINT_get_affine_coordinates_GFp
133 (group, tmp_point, X, NULL, ctx)) {
134 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
138 #ifndef OPENSSL_NO_EC2M
139 else { /* NID_X9_62_characteristic_two_field */
141 if (!EC_POINT_get_affine_coordinates_GF2m(group,
144 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
149 if (!BN_nnmod(r, X, order, ctx)) {
150 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
154 while (BN_is_zero(r));
156 /* compute the inverse of k */
157 if (EC_GROUP_get_mont_data(group) != NULL) {
159 * We want inverse in constant time, therefore we utilize the fact
160 * order must be prime and use Fermats Little Theorem instead.
162 if (!BN_set_word(X, 2)) {
163 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
166 if (!BN_mod_sub(X, order, X, order, ctx)) {
167 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
170 BN_set_flags(X, BN_FLG_CONSTTIME);
171 if (!BN_mod_exp_mont_consttime
172 (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
173 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
177 if (!BN_mod_inverse(k, k, order, ctx)) {
178 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
183 /* clear old values if necessary */
185 BN_clear_free(*kinvp);
186 /* save the pre-computed values */
197 EC_POINT_free(tmp_point);
202 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
205 return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
208 ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
209 const BIGNUM *in_kinv, const BIGNUM *in_r,
213 BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *blind = NULL;
214 BIGNUM *blindm = NULL;
215 const BIGNUM *order, *ckinv;
217 const EC_GROUP *group;
219 const BIGNUM *priv_key;
221 group = EC_KEY_get0_group(eckey);
222 priv_key = EC_KEY_get0_private_key(eckey);
224 if (group == NULL || priv_key == NULL) {
225 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
229 if (!EC_KEY_can_sign(eckey)) {
230 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
234 ret = ECDSA_SIG_new();
236 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
241 if (ret->r == NULL || ret->s == NULL) {
242 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
247 ctx = BN_CTX_secure_new();
249 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
254 tmp = BN_CTX_get(ctx);
256 blind = BN_CTX_get(ctx);
257 blindm = BN_CTX_get(ctx);
258 if (blindm == NULL) {
259 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
263 order = EC_GROUP_get0_order(group);
265 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_EC_LIB);
268 i = BN_num_bits(order);
270 * Need to truncate digest if it is too long: first truncate whole bytes.
272 if (8 * dgst_len > i)
273 dgst_len = (i + 7) / 8;
274 if (!BN_bin2bn(dgst, dgst_len, m)) {
275 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
278 /* If still too long truncate remaining bits with a shift */
279 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
280 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
284 if (in_kinv == NULL || in_r == NULL) {
285 if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
286 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
292 if (BN_copy(ret->r, in_r) == NULL) {
293 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
299 * The normal signature calculation is:
301 * s := k^-1 * (m + r * priv_key) mod order
303 * We will blind this to protect against side channel attacks
305 * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod order
308 /* Generate a blinding value */
310 if (!BN_rand(blind, BN_num_bits(order) - 1, BN_RAND_TOP_ANY,
313 } while (BN_is_zero(blind));
314 BN_set_flags(blind, BN_FLG_CONSTTIME);
315 BN_set_flags(blindm, BN_FLG_CONSTTIME);
316 BN_set_flags(tmp, BN_FLG_CONSTTIME);
318 /* tmp := blind * priv_key * r mod order */
319 if (!BN_mod_mul(tmp, blind, priv_key, order, ctx)) {
320 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
323 if (!BN_mod_mul(tmp, tmp, ret->r, order, ctx)) {
324 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
328 /* blindm := blind * m mod order */
329 if (!BN_mod_mul(blindm, blind, m, order, ctx)) {
330 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
334 /* s : = (blind * priv_key * r) + (blind * m) mod order */
335 if (!BN_mod_add_quick(s, tmp, blindm, order)) {
336 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
340 /* s := s * k^-1 mod order */
341 if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
342 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
346 /* s:= s * blind^-1 mod order */
347 if (BN_mod_inverse(blind, blind, order, ctx) == NULL) {
348 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
351 if (!BN_mod_mul(s, s, blind, order, ctx)) {
352 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
358 * if kinv and r have been supplied by the caller don't to
359 * generate new kinv and r values
361 if (in_kinv != NULL && in_r != NULL) {
362 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
366 /* s != 0 => we have a valid signature */
385 * 1: correct signature
386 * 0: incorrect signature
389 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
390 const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
393 const unsigned char *p = sigbuf;
394 unsigned char *der = NULL;
401 if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
403 /* Ensure signature uses DER and doesn't have trailing garbage */
404 derlen = i2d_ECDSA_SIG(s, &der);
405 if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
407 ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
409 OPENSSL_clear_free(der, derlen);
414 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
415 const ECDSA_SIG *sig, EC_KEY *eckey)
420 BIGNUM *u1, *u2, *m, *X;
421 EC_POINT *point = NULL;
422 const EC_GROUP *group;
423 const EC_POINT *pub_key;
425 /* check input values */
426 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
427 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
428 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
432 if (!EC_KEY_can_sign(eckey)) {
433 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
439 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
443 u1 = BN_CTX_get(ctx);
444 u2 = BN_CTX_get(ctx);
448 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
452 order = EC_GROUP_get0_order(group);
454 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
458 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
459 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
460 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
461 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
462 ret = 0; /* signature is invalid */
465 /* calculate tmp1 = inv(S) mod order */
466 if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
467 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
471 i = BN_num_bits(order);
473 * Need to truncate digest if it is too long: first truncate whole bytes.
475 if (8 * dgst_len > i)
476 dgst_len = (i + 7) / 8;
477 if (!BN_bin2bn(dgst, dgst_len, m)) {
478 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
481 /* If still too long truncate remaining bits with a shift */
482 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
483 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
486 /* u1 = m * tmp mod order */
487 if (!BN_mod_mul(u1, m, u2, order, ctx)) {
488 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
491 /* u2 = r * w mod q */
492 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
493 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
497 if ((point = EC_POINT_new(group)) == NULL) {
498 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
501 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
502 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
505 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
506 NID_X9_62_prime_field) {
507 if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
508 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
512 #ifndef OPENSSL_NO_EC2M
513 else { /* NID_X9_62_characteristic_two_field */
515 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
516 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
521 if (!BN_nnmod(u1, X, order, ctx)) {
522 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
525 /* if the signature is correct u1 is equal to sig->r */
526 ret = (BN_ucmp(u1, sig->r) == 0);
530 EC_POINT_free(point);