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)
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_priv_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 Fermat's 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;
214 const BIGNUM *order, *ckinv;
216 const EC_GROUP *group;
218 const BIGNUM *priv_key;
220 group = EC_KEY_get0_group(eckey);
221 priv_key = EC_KEY_get0_private_key(eckey);
223 if (group == NULL || priv_key == NULL) {
224 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
228 if (!EC_KEY_can_sign(eckey)) {
229 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
233 ret = ECDSA_SIG_new();
235 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
240 if (ret->r == NULL || ret->s == NULL) {
241 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
246 if ((ctx = BN_CTX_new()) == NULL ||
247 (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
248 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
252 order = EC_GROUP_get0_order(group);
254 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_EC_LIB);
257 i = BN_num_bits(order);
259 * Need to truncate digest if it is too long: first truncate whole bytes.
261 if (8 * dgst_len > i)
262 dgst_len = (i + 7) / 8;
263 if (!BN_bin2bn(dgst, dgst_len, m)) {
264 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
267 /* If still too long truncate remaining bits with a shift */
268 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
269 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
273 if (in_kinv == NULL || in_r == NULL) {
274 if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
275 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
281 if (BN_copy(ret->r, in_r) == NULL) {
282 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
287 if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
288 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
291 if (!BN_mod_add_quick(s, tmp, m, order)) {
292 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
295 if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
296 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
301 * if kinv and r have been supplied by the caller don't to
302 * generate new kinv and r values
304 if (in_kinv != NULL && in_r != NULL) {
305 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
309 /* s != 0 => we have a valid signature */
329 * 1: correct signature
330 * 0: incorrect signature
333 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
334 const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
337 const unsigned char *p = sigbuf;
338 unsigned char *der = NULL;
345 if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
347 /* Ensure signature uses DER and doesn't have trailing garbage */
348 derlen = i2d_ECDSA_SIG(s, &der);
349 if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
351 ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
353 OPENSSL_clear_free(der, derlen);
358 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
359 const ECDSA_SIG *sig, EC_KEY *eckey)
364 BIGNUM *u1, *u2, *m, *X;
365 EC_POINT *point = NULL;
366 const EC_GROUP *group;
367 const EC_POINT *pub_key;
369 /* check input values */
370 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
371 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
372 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
376 if (!EC_KEY_can_sign(eckey)) {
377 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
383 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
387 u1 = BN_CTX_get(ctx);
388 u2 = BN_CTX_get(ctx);
392 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
396 order = EC_GROUP_get0_order(group);
398 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
402 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
403 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
404 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
405 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
406 ret = 0; /* signature is invalid */
409 /* calculate tmp1 = inv(S) mod order */
410 if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
411 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
415 i = BN_num_bits(order);
417 * Need to truncate digest if it is too long: first truncate whole bytes.
419 if (8 * dgst_len > i)
420 dgst_len = (i + 7) / 8;
421 if (!BN_bin2bn(dgst, dgst_len, m)) {
422 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
425 /* If still too long truncate remaining bits with a shift */
426 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
427 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
430 /* u1 = m * tmp mod order */
431 if (!BN_mod_mul(u1, m, u2, order, ctx)) {
432 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
435 /* u2 = r * w mod q */
436 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
437 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
441 if ((point = EC_POINT_new(group)) == NULL) {
442 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
445 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
446 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
449 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
450 NID_X9_62_prime_field) {
451 if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
452 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
456 #ifndef OPENSSL_NO_EC2M
457 else { /* NID_X9_62_characteristic_two_field */
459 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
460 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
465 if (!BN_nnmod(u1, X, order, ctx)) {
466 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
469 /* if the signature is correct u1 is equal to sig->r */
470 ret = (BN_ucmp(u1, sig->r) == 0);
474 EC_POINT_free(point);