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 (!BN_mod_inverse(k, k, order, ctx)) {
183 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
184 goto err;
185 }
186 /* clear old values if necessary */
187 if (*rp != NULL)
188 BN_clear_free(*rp);
189 if (*kinvp != NULL)
190 BN_clear_free(*kinvp);
191 /* save the pre-computed values */
192 *rp = r;
193 *kinvp = k;
194 ret = 1;
195 err:
196 if (!ret) {
197 if (k != NULL)
198 BN_clear_free(k);
199 if (r != NULL)
200 BN_clear_free(r);
201 }
202 if (ctx_in == NULL)
203 BN_CTX_free(ctx);
204 if (order != NULL)
205 BN_free(order);
206 if (tmp_point != NULL)
207 EC_POINT_free(tmp_point);
208 if (X)
209 BN_clear_free(X);
210 return (ret);
211 }
212
ecdsa_do_sign(const unsigned char * dgst,int dgst_len,const BIGNUM * in_kinv,const BIGNUM * in_r,EC_KEY * eckey)213 static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
214 const BIGNUM *in_kinv, const BIGNUM *in_r,
215 EC_KEY *eckey)
216 {
217 int ok = 0, i;
218 BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;
219 const BIGNUM *ckinv;
220 BN_CTX *ctx = NULL;
221 const EC_GROUP *group;
222 ECDSA_SIG *ret;
223 ECDSA_DATA *ecdsa;
224 const BIGNUM *priv_key;
225
226 ecdsa = ecdsa_check(eckey);
227 group = EC_KEY_get0_group(eckey);
228 priv_key = EC_KEY_get0_private_key(eckey);
229
230 if (group == NULL || priv_key == NULL || ecdsa == NULL) {
231 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);
232 return NULL;
233 }
234
235 ret = ECDSA_SIG_new();
236 if (!ret) {
237 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
238 return NULL;
239 }
240 s = ret->s;
241
242 if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
243 (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
244 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
245 goto err;
246 }
247
248 if (!EC_GROUP_get_order(group, order, ctx)) {
249 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
250 goto err;
251 }
252 i = BN_num_bits(order);
253 /*
254 * Need to truncate digest if it is too long: first truncate whole bytes.
255 */
256 if (8 * dgst_len > i)
257 dgst_len = (i + 7) / 8;
258 if (!BN_bin2bn(dgst, dgst_len, m)) {
259 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
260 goto err;
261 }
262 /* If still too long truncate remaining bits with a shift */
263 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
264 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
265 goto err;
266 }
267 do {
268 if (in_kinv == NULL || in_r == NULL) {
269 if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) {
270 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_ECDSA_LIB);
271 goto err;
272 }
273 ckinv = kinv;
274 } else {
275 ckinv = in_kinv;
276 if (BN_copy(ret->r, in_r) == NULL) {
277 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
278 goto err;
279 }
280 }
281
282 if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
283 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
284 goto err;
285 }
286 if (!BN_mod_add_quick(s, tmp, m, order)) {
287 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
288 goto err;
289 }
290 if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
291 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
292 goto err;
293 }
294 if (BN_is_zero(s)) {
295 /*
296 * if kinv and r have been supplied by the caller don't to
297 * generate new kinv and r values
298 */
299 if (in_kinv != NULL && in_r != NULL) {
300 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,
301 ECDSA_R_NEED_NEW_SETUP_VALUES);
302 goto err;
303 }
304 } else
305 /* s != 0 => we have a valid signature */
306 break;
307 }
308 while (1);
309
310 ok = 1;
311 err:
312 if (!ok) {
313 ECDSA_SIG_free(ret);
314 ret = NULL;
315 }
316 if (ctx)
317 BN_CTX_free(ctx);
318 if (m)
319 BN_clear_free(m);
320 if (tmp)
321 BN_clear_free(tmp);
322 if (order)
323 BN_free(order);
324 if (kinv)
325 BN_clear_free(kinv);
326 return ret;
327 }
328
ecdsa_do_verify(const unsigned char * dgst,int dgst_len,const ECDSA_SIG * sig,EC_KEY * eckey)329 static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
330 const ECDSA_SIG *sig, EC_KEY *eckey)
331 {
332 int ret = -1, i;
333 BN_CTX *ctx;
334 BIGNUM *order, *u1, *u2, *m, *X;
335 EC_POINT *point = NULL;
336 const EC_GROUP *group;
337 const EC_POINT *pub_key;
338
339 /* check input values */
340 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
341 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
342 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);
343 return -1;
344 }
345
346 ctx = BN_CTX_new();
347 if (!ctx) {
348 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
349 return -1;
350 }
351 BN_CTX_start(ctx);
352 order = BN_CTX_get(ctx);
353 u1 = BN_CTX_get(ctx);
354 u2 = BN_CTX_get(ctx);
355 m = BN_CTX_get(ctx);
356 X = BN_CTX_get(ctx);
357 if (!X) {
358 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
359 goto err;
360 }
361
362 if (!EC_GROUP_get_order(group, order, ctx)) {
363 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
364 goto err;
365 }
366
367 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
368 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
369 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
370 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);
371 ret = 0; /* signature is invalid */
372 goto err;
373 }
374 /* calculate tmp1 = inv(S) mod order */
375 if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
376 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
377 goto err;
378 }
379 /* digest -> m */
380 i = BN_num_bits(order);
381 /*
382 * Need to truncate digest if it is too long: first truncate whole bytes.
383 */
384 if (8 * dgst_len > i)
385 dgst_len = (i + 7) / 8;
386 if (!BN_bin2bn(dgst, dgst_len, m)) {
387 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
388 goto err;
389 }
390 /* If still too long truncate remaining bits with a shift */
391 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
392 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
393 goto err;
394 }
395 /* u1 = m * tmp mod order */
396 if (!BN_mod_mul(u1, m, u2, order, ctx)) {
397 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
398 goto err;
399 }
400 /* u2 = r * w mod q */
401 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
402 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
403 goto err;
404 }
405
406 if ((point = EC_POINT_new(group)) == NULL) {
407 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
408 goto err;
409 }
410 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
411 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
412 goto err;
413 }
414 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
415 NID_X9_62_prime_field) {
416 if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
417 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
418 goto err;
419 }
420 }
421 #ifndef OPENSSL_NO_EC2M
422 else { /* NID_X9_62_characteristic_two_field */
423
424 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
425 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
426 goto err;
427 }
428 }
429 #endif
430 if (!BN_nnmod(u1, X, order, ctx)) {
431 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
432 goto err;
433 }
434 /* if the signature is correct u1 is equal to sig->r */
435 ret = (BN_ucmp(u1, sig->r) == 0);
436 err:
437 BN_CTX_end(ctx);
438 BN_CTX_free(ctx);
439 if (point)
440 EC_POINT_free(point);
441 return ret;
442 }
443