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
ECDSA_OpenSSL(void)85 const ECDSA_METHOD *ECDSA_OpenSSL(void)
86 {
87 return &openssl_ecdsa_meth;
88 }
89
ecdsa_sign_setup(EC_KEY * eckey,BN_CTX * ctx_in,BIGNUM ** kinvp,BIGNUM ** rp)90 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 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
100 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
101 return 0;
102 }
103
104 if (ctx_in == NULL) {
105 if ((ctx = BN_CTX_new()) == NULL) {
106 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
107 return 0;
108 }
109 } else
110 ctx = ctx_in;
111
112 k = BN_new(); /* this value is later returned in *kinvp */
113 r = BN_new(); /* this value is later returned in *rp */
114 order = BN_new();
115 X = BN_new();
116 if (!k || !r || !order || !X) {
117 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
118 goto err;
119 }
120 if ((tmp_point = EC_POINT_new(group)) == NULL) {
121 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
122 goto err;
123 }
124 if (!EC_GROUP_get_order(group, order, ctx)) {
125 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
126 goto err;
127 }
128
129 do {
130 /* get random k */
131 do
132 if (!BN_rand_range(k, order)) {
133 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,
134 ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);
135 goto err;
136 }
137 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 if (!BN_add(k, k, order))
145 goto err;
146 if (BN_num_bits(k) <= BN_num_bits(order))
147 if (!BN_add(k, k, order))
148 goto err;
149
150 /* compute r the x-coordinate of generator * k */
151 if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
152 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
153 goto err;
154 }
155 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
156 NID_X9_62_prime_field) {
157 if (!EC_POINT_get_affine_coordinates_GFp
158 (group, tmp_point, X, NULL, ctx)) {
159 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
160 goto err;
161 }
162 }
163 #ifndef OPENSSL_NO_EC2M
164 else { /* NID_X9_62_characteristic_two_field */
165
166 if (!EC_POINT_get_affine_coordinates_GF2m(group,
167 tmp_point, X, NULL,
168 ctx)) {
169 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
170 goto err;
171 }
172 }
173 #endif
174 if (!BN_nnmod(r, X, order, ctx)) {
175 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
176 goto err;
177 }
178 }
179 while (BN_is_zero(r));
180
181 /* compute the inverse of k */
182 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 if (!BN_set_word(X, 2)) {
188 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
189 goto err;
190 }
191 if (!BN_mod_sub(X, order, X, order, ctx)) {
192 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
193 goto err;
194 }
195 BN_set_flags(X, BN_FLG_CONSTTIME);
196 if (!BN_mod_exp_mont_consttime
197 (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
198 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
199 goto err;
200 }
201 } else {
202 if (!BN_mod_inverse(k, k, order, ctx)) {
203 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
204 goto err;
205 }
206 }
207
208 /* clear old values if necessary */
209 if (*rp != NULL)
210 BN_clear_free(*rp);
211 if (*kinvp != NULL)
212 BN_clear_free(*kinvp);
213 /* save the pre-computed values */
214 *rp = r;
215 *kinvp = k;
216 ret = 1;
217 err:
218 if (!ret) {
219 if (k != NULL)
220 BN_clear_free(k);
221 if (r != NULL)
222 BN_clear_free(r);
223 }
224 if (ctx_in == NULL)
225 BN_CTX_free(ctx);
226 if (order != NULL)
227 BN_free(order);
228 if (tmp_point != NULL)
229 EC_POINT_free(tmp_point);
230 if (X)
231 BN_clear_free(X);
232 return (ret);
233 }
234
ecdsa_do_sign(const unsigned char * dgst,int dgst_len,const BIGNUM * in_kinv,const BIGNUM * in_r,EC_KEY * eckey)235 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 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 ecdsa = ecdsa_check(eckey);
249 group = EC_KEY_get0_group(eckey);
250 priv_key = EC_KEY_get0_private_key(eckey);
251
252 if (group == NULL || priv_key == NULL || ecdsa == NULL) {
253 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);
254 return NULL;
255 }
256
257 ret = ECDSA_SIG_new();
258 if (!ret) {
259 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
260 return NULL;
261 }
262 s = ret->s;
263
264 if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
265 (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
266 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
267 goto err;
268 }
269
270 if (!EC_GROUP_get_order(group, order, ctx)) {
271 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
272 goto err;
273 }
274 i = BN_num_bits(order);
275 /*
276 * Need to truncate digest if it is too long: first truncate whole bytes.
277 */
278 if (8 * dgst_len > i)
279 dgst_len = (i + 7) / 8;
280 if (!BN_bin2bn(dgst, dgst_len, m)) {
281 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
282 goto err;
283 }
284 /* If still too long truncate remaining bits with a shift */
285 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
286 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
287 goto err;
288 }
289 do {
290 if (in_kinv == NULL || in_r == NULL) {
291 if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) {
292 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_ECDSA_LIB);
293 goto err;
294 }
295 ckinv = kinv;
296 } else {
297 ckinv = in_kinv;
298 if (BN_copy(ret->r, in_r) == NULL) {
299 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
300 goto err;
301 }
302 }
303
304 if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
305 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
306 goto err;
307 }
308 if (!BN_mod_add_quick(s, tmp, m, order)) {
309 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
310 goto err;
311 }
312 if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
313 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
314 goto err;
315 }
316 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 if (in_kinv != NULL && in_r != NULL) {
322 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
323 ECDSA_R_NEED_NEW_SETUP_VALUES);
324 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 if (!ok) {
335 ECDSA_SIG_free(ret);
336 ret = NULL;
337 }
338 if (ctx)
339 BN_CTX_free(ctx);
340 if (m)
341 BN_clear_free(m);
342 if (tmp)
343 BN_clear_free(tmp);
344 if (order)
345 BN_free(order);
346 if (kinv)
347 BN_clear_free(kinv);
348 return ret;
349 }
350
ecdsa_do_verify(const unsigned char * dgst,int dgst_len,const ECDSA_SIG * sig,EC_KEY * eckey)351 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 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
363 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
364 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);
365 return -1;
366 }
367
368 ctx = BN_CTX_new();
369 if (!ctx) {
370 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
371 return -1;
372 }
373 BN_CTX_start(ctx);
374 order = BN_CTX_get(ctx);
375 u1 = BN_CTX_get(ctx);
376 u2 = BN_CTX_get(ctx);
377 m = BN_CTX_get(ctx);
378 X = BN_CTX_get(ctx);
379 if (!X) {
380 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
381 goto err;
382 }
383
384 if (!EC_GROUP_get_order(group, order, ctx)) {
385 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
386 goto err;
387 }
388
389 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
390 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
391 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
392 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);
393 ret = 0; /* signature is invalid */
394 goto err;
395 }
396 /* calculate tmp1 = inv(S) mod order */
397 if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
398 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
399 goto err;
400 }
401 /* digest -> m */
402 i = BN_num_bits(order);
403 /*
404 * Need to truncate digest if it is too long: first truncate whole bytes.
405 */
406 if (8 * dgst_len > i)
407 dgst_len = (i + 7) / 8;
408 if (!BN_bin2bn(dgst, dgst_len, m)) {
409 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
410 goto err;
411 }
412 /* If still too long truncate remaining bits with a shift */
413 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
414 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
415 goto err;
416 }
417 /* u1 = m * tmp mod order */
418 if (!BN_mod_mul(u1, m, u2, order, ctx)) {
419 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
420 goto err;
421 }
422 /* u2 = r * w mod q */
423 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
424 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
425 goto err;
426 }
427
428 if ((point = EC_POINT_new(group)) == NULL) {
429 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
430 goto err;
431 }
432 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
433 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
434 goto err;
435 }
436 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
437 NID_X9_62_prime_field) {
438 if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
439 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
440 goto err;
441 }
442 }
443 #ifndef OPENSSL_NO_EC2M
444 else { /* NID_X9_62_characteristic_two_field */
445
446 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
447 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
448 goto err;
449 }
450 }
451 #endif
452 if (!BN_nnmod(u1, X, order, ctx)) {
453 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
454 goto err;
455 }
456 /* if the signature is correct u1 is equal to sig->r */
457 ret = (BN_ucmp(u1, sig->r) == 0);
458 err:
459 BN_CTX_end(ctx);
460 BN_CTX_free(ctx);
461 if (point)
462 EC_POINT_free(point);
463 return ret;
464 }
465