Line data Source code
1 : /* crypto/ecdsa/ecs_ossl.c */
2 : /*
3 : * Written by Nils Larsch for the OpenSSL project
4 : */
5 : /* ====================================================================
6 : * Copyright (c) 1998-2004 The OpenSSL Project. All rights reserved.
7 : *
8 : * Redistribution and use in source and binary forms, with or without
9 : * modification, are permitted provided that the following conditions
10 : * are met:
11 : *
12 : * 1. Redistributions of source code must retain the above copyright
13 : * notice, this list of conditions and the following disclaimer.
14 : *
15 : * 2. Redistributions in binary form must reproduce the above copyright
16 : * notice, this list of conditions and the following disclaimer in
17 : * the documentation and/or other materials provided with the
18 : * distribution.
19 : *
20 : * 3. All advertising materials mentioning features or use of this
21 : * software must display the following acknowledgment:
22 : * "This product includes software developed by the OpenSSL Project
23 : * for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
24 : *
25 : * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
26 : * endorse or promote products derived from this software without
27 : * prior written permission. For written permission, please contact
28 : * openssl-core@OpenSSL.org.
29 : *
30 : * 5. Products derived from this software may not be called "OpenSSL"
31 : * nor may "OpenSSL" appear in their names without prior written
32 : * permission of the OpenSSL Project.
33 : *
34 : * 6. Redistributions of any form whatsoever must retain the following
35 : * acknowledgment:
36 : * "This product includes software developed by the OpenSSL Project
37 : * for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
38 : *
39 : * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
40 : * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
41 : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
42 : * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
43 : * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44 : * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
45 : * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
46 : * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
48 : * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
49 : * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
50 : * OF THE POSSIBILITY OF SUCH DAMAGE.
51 : * ====================================================================
52 : *
53 : * This product includes cryptographic software written by Eric Young
54 : * (eay@cryptsoft.com). This product includes software written by Tim
55 : * Hudson (tjh@cryptsoft.com).
56 : *
57 : */
58 :
59 : #include "ecs_locl.h"
60 : #include <openssl/err.h>
61 : #include <openssl/obj_mac.h>
62 : #include <openssl/bn.h>
63 :
64 : static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen,
65 : const BIGNUM *, const BIGNUM *,
66 : EC_KEY *eckey);
67 : static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
68 : BIGNUM **rp);
69 : static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
70 : const ECDSA_SIG *sig, EC_KEY *eckey);
71 :
72 : static ECDSA_METHOD openssl_ecdsa_meth = {
73 : "OpenSSL ECDSA method",
74 : ecdsa_do_sign,
75 : ecdsa_sign_setup,
76 : ecdsa_do_verify,
77 : #if 0
78 : NULL, /* init */
79 : NULL, /* finish */
80 : #endif
81 : 0, /* flags */
82 : NULL /* app_data */
83 : };
84 :
85 0 : const ECDSA_METHOD *ECDSA_OpenSSL(void)
86 : {
87 0 : return &openssl_ecdsa_meth;
88 : }
89 :
90 0 : static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
91 : BIGNUM **rp)
92 : {
93 : BN_CTX *ctx = NULL;
94 : BIGNUM *k = NULL, *r = NULL, *order = NULL, *X = NULL;
95 : EC_POINT *tmp_point = NULL;
96 : const EC_GROUP *group;
97 : int ret = 0;
98 :
99 0 : if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
100 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
101 0 : return 0;
102 : }
103 :
104 0 : if (ctx_in == NULL) {
105 0 : if ((ctx = BN_CTX_new()) == NULL) {
106 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
107 0 : return 0;
108 : }
109 : } else
110 : ctx = ctx_in;
111 :
112 0 : k = BN_new(); /* this value is later returned in *kinvp */
113 0 : r = BN_new(); /* this value is later returned in *rp */
114 0 : order = BN_new();
115 0 : X = BN_new();
116 0 : if (!k || !r || !order || !X) {
117 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
118 0 : goto err;
119 : }
120 0 : if ((tmp_point = EC_POINT_new(group)) == NULL) {
121 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
122 0 : goto err;
123 : }
124 0 : if (!EC_GROUP_get_order(group, order, ctx)) {
125 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
126 0 : goto err;
127 : }
128 :
129 : do {
130 : /* get random k */
131 : do
132 0 : if (!BN_rand_range(k, order)) {
133 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,
134 : ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);
135 0 : goto err;
136 : }
137 0 : while (BN_is_zero(k)) ;
138 :
139 : /*
140 : * We do not want timing information to leak the length of k, so we
141 : * compute G*k using an equivalent scalar of fixed bit-length.
142 : */
143 :
144 0 : if (!BN_add(k, k, order))
145 : goto err;
146 0 : if (BN_num_bits(k) <= BN_num_bits(order))
147 0 : if (!BN_add(k, k, order))
148 : goto err;
149 :
150 : /* compute r the x-coordinate of generator * k */
151 0 : if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
152 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
153 0 : goto err;
154 : }
155 0 : if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
156 : NID_X9_62_prime_field) {
157 0 : if (!EC_POINT_get_affine_coordinates_GFp
158 0 : (group, tmp_point, X, NULL, ctx)) {
159 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
160 0 : goto err;
161 : }
162 : }
163 : #ifndef OPENSSL_NO_EC2M
164 : else { /* NID_X9_62_characteristic_two_field */
165 :
166 0 : if (!EC_POINT_get_affine_coordinates_GF2m(group,
167 : tmp_point, X, NULL,
168 : ctx)) {
169 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
170 0 : goto err;
171 : }
172 : }
173 : #endif
174 0 : if (!BN_nnmod(r, X, order, ctx)) {
175 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
176 0 : goto err;
177 : }
178 : }
179 0 : while (BN_is_zero(r));
180 :
181 : /* compute the inverse of k */
182 0 : if (EC_GROUP_get_mont_data(group) != NULL) {
183 : /*
184 : * We want inverse in constant time, therefore we utilize the fact
185 : * order must be prime and use Fermats Little Theorem instead.
186 : */
187 0 : if (!BN_set_word(X, 2)) {
188 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
189 0 : goto err;
190 : }
191 0 : if (!BN_mod_sub(X, order, X, order, ctx)) {
192 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
193 0 : goto err;
194 : }
195 0 : BN_set_flags(X, BN_FLG_CONSTTIME);
196 0 : if (!BN_mod_exp_mont_consttime
197 0 : (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
198 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
199 0 : goto err;
200 : }
201 : } else {
202 0 : if (!BN_mod_inverse(k, k, order, ctx)) {
203 0 : ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
204 0 : goto err;
205 : }
206 : }
207 :
208 : /* clear old values if necessary */
209 0 : if (*rp != NULL)
210 0 : BN_clear_free(*rp);
211 0 : if (*kinvp != NULL)
212 0 : BN_clear_free(*kinvp);
213 : /* save the pre-computed values */
214 0 : *rp = r;
215 0 : *kinvp = k;
216 : ret = 1;
217 : err:
218 0 : if (!ret) {
219 0 : if (k != NULL)
220 0 : BN_clear_free(k);
221 0 : if (r != NULL)
222 0 : BN_clear_free(r);
223 : }
224 0 : if (ctx_in == NULL)
225 0 : BN_CTX_free(ctx);
226 0 : if (order != NULL)
227 0 : BN_free(order);
228 0 : if (tmp_point != NULL)
229 0 : EC_POINT_free(tmp_point);
230 0 : if (X)
231 0 : BN_clear_free(X);
232 0 : return (ret);
233 : }
234 :
235 0 : static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
236 : const BIGNUM *in_kinv, const BIGNUM *in_r,
237 : EC_KEY *eckey)
238 : {
239 : int ok = 0, i;
240 0 : BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;
241 : const BIGNUM *ckinv;
242 : BN_CTX *ctx = NULL;
243 : const EC_GROUP *group;
244 : ECDSA_SIG *ret;
245 : ECDSA_DATA *ecdsa;
246 : const BIGNUM *priv_key;
247 :
248 0 : ecdsa = ecdsa_check(eckey);
249 0 : group = EC_KEY_get0_group(eckey);
250 0 : priv_key = EC_KEY_get0_private_key(eckey);
251 :
252 0 : if (group == NULL || priv_key == NULL || ecdsa == NULL) {
253 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);
254 0 : return NULL;
255 : }
256 :
257 0 : ret = ECDSA_SIG_new();
258 0 : if (!ret) {
259 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
260 0 : return NULL;
261 : }
262 0 : s = ret->s;
263 :
264 0 : if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
265 0 : (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
266 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
267 0 : goto err;
268 : }
269 :
270 0 : if (!EC_GROUP_get_order(group, order, ctx)) {
271 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
272 0 : goto err;
273 : }
274 0 : i = BN_num_bits(order);
275 : /*
276 : * Need to truncate digest if it is too long: first truncate whole bytes.
277 : */
278 0 : if (8 * dgst_len > i)
279 0 : dgst_len = (i + 7) / 8;
280 0 : if (!BN_bin2bn(dgst, dgst_len, m)) {
281 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
282 0 : goto err;
283 : }
284 : /* If still too long truncate remaining bits with a shift */
285 0 : if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
286 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
287 0 : goto err;
288 : }
289 : do {
290 0 : if (in_kinv == NULL || in_r == NULL) {
291 0 : if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) {
292 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_ECDSA_LIB);
293 0 : goto err;
294 : }
295 0 : ckinv = kinv;
296 : } else {
297 : ckinv = in_kinv;
298 0 : if (BN_copy(ret->r, in_r) == NULL) {
299 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
300 0 : goto err;
301 : }
302 : }
303 :
304 0 : if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
305 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
306 0 : goto err;
307 : }
308 0 : if (!BN_mod_add_quick(s, tmp, m, order)) {
309 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
310 0 : goto err;
311 : }
312 0 : if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
313 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
314 0 : goto err;
315 : }
316 0 : if (BN_is_zero(s)) {
317 : /*
318 : * if kinv and r have been supplied by the caller don't to
319 : * generate new kinv and r values
320 : */
321 0 : if (in_kinv != NULL && in_r != NULL) {
322 0 : ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
323 : ECDSA_R_NEED_NEW_SETUP_VALUES);
324 0 : goto err;
325 : }
326 : } else
327 : /* s != 0 => we have a valid signature */
328 : break;
329 : }
330 : while (1);
331 :
332 : ok = 1;
333 : err:
334 0 : if (!ok) {
335 0 : ECDSA_SIG_free(ret);
336 : ret = NULL;
337 : }
338 0 : if (ctx)
339 0 : BN_CTX_free(ctx);
340 0 : if (m)
341 0 : BN_clear_free(m);
342 0 : if (tmp)
343 0 : BN_clear_free(tmp);
344 0 : if (order)
345 0 : BN_free(order);
346 0 : if (kinv)
347 0 : BN_clear_free(kinv);
348 0 : return ret;
349 : }
350 :
351 0 : static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
352 : const ECDSA_SIG *sig, EC_KEY *eckey)
353 : {
354 : int ret = -1, i;
355 : BN_CTX *ctx;
356 : BIGNUM *order, *u1, *u2, *m, *X;
357 : EC_POINT *point = NULL;
358 : const EC_GROUP *group;
359 : const EC_POINT *pub_key;
360 :
361 : /* check input values */
362 0 : if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
363 0 : (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
364 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);
365 0 : return -1;
366 : }
367 :
368 0 : ctx = BN_CTX_new();
369 0 : if (!ctx) {
370 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
371 0 : return -1;
372 : }
373 0 : BN_CTX_start(ctx);
374 0 : order = BN_CTX_get(ctx);
375 0 : u1 = BN_CTX_get(ctx);
376 0 : u2 = BN_CTX_get(ctx);
377 0 : m = BN_CTX_get(ctx);
378 0 : X = BN_CTX_get(ctx);
379 0 : if (!X) {
380 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
381 0 : goto err;
382 : }
383 :
384 0 : if (!EC_GROUP_get_order(group, order, ctx)) {
385 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
386 0 : goto err;
387 : }
388 :
389 0 : if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
390 0 : BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
391 0 : BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
392 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);
393 : ret = 0; /* signature is invalid */
394 0 : goto err;
395 : }
396 : /* calculate tmp1 = inv(S) mod order */
397 0 : if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
398 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
399 0 : goto err;
400 : }
401 : /* digest -> m */
402 0 : i = BN_num_bits(order);
403 : /*
404 : * Need to truncate digest if it is too long: first truncate whole bytes.
405 : */
406 0 : if (8 * dgst_len > i)
407 0 : dgst_len = (i + 7) / 8;
408 0 : if (!BN_bin2bn(dgst, dgst_len, m)) {
409 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
410 0 : goto err;
411 : }
412 : /* If still too long truncate remaining bits with a shift */
413 0 : if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
414 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
415 0 : goto err;
416 : }
417 : /* u1 = m * tmp mod order */
418 0 : if (!BN_mod_mul(u1, m, u2, order, ctx)) {
419 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
420 0 : goto err;
421 : }
422 : /* u2 = r * w mod q */
423 0 : if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
424 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
425 0 : goto err;
426 : }
427 :
428 0 : if ((point = EC_POINT_new(group)) == NULL) {
429 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
430 0 : goto err;
431 : }
432 0 : if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
433 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
434 0 : goto err;
435 : }
436 0 : if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
437 : NID_X9_62_prime_field) {
438 0 : if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
439 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
440 0 : goto err;
441 : }
442 : }
443 : #ifndef OPENSSL_NO_EC2M
444 : else { /* NID_X9_62_characteristic_two_field */
445 :
446 0 : if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
447 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
448 0 : goto err;
449 : }
450 : }
451 : #endif
452 0 : if (!BN_nnmod(u1, X, order, ctx)) {
453 0 : ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
454 0 : goto err;
455 : }
456 : /* if the signature is correct u1 is equal to sig->r */
457 0 : ret = (BN_ucmp(u1, sig->r) == 0);
458 : err:
459 0 : BN_CTX_end(ctx);
460 0 : BN_CTX_free(ctx);
461 0 : if (point)
462 0 : EC_POINT_free(point);
463 0 : return ret;
464 : }
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