ecs_ossl.c revision 325337
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 64static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen, 65 const BIGNUM *, const BIGNUM *, 66 EC_KEY *eckey); 67static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, 68 BIGNUM **rp); 69static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len, 70 const ECDSA_SIG *sig, EC_KEY *eckey); 71 72static 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 85const ECDSA_METHOD *ECDSA_OpenSSL(void) 86{ 87 return &openssl_ecdsa_meth; 88} 89 90static 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 int order_bits; 99 100 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) { 101 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER); 102 return 0; 103 } 104 105 if (ctx_in == NULL) { 106 if ((ctx = BN_CTX_new()) == NULL) { 107 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE); 108 return 0; 109 } 110 } else 111 ctx = ctx_in; 112 113 k = BN_new(); /* this value is later returned in *kinvp */ 114 r = BN_new(); /* this value is later returned in *rp */ 115 order = BN_new(); 116 X = BN_new(); 117 if (!k || !r || !order || !X) { 118 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE); 119 goto err; 120 } 121 if ((tmp_point = EC_POINT_new(group)) == NULL) { 122 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 123 goto err; 124 } 125 if (!EC_GROUP_get_order(group, order, ctx)) { 126 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 127 goto err; 128 } 129 130 /* Preallocate space */ 131 order_bits = BN_num_bits(order); 132 if (!BN_set_bit(k, order_bits) 133 || !BN_set_bit(r, order_bits) 134 || !BN_set_bit(X, order_bits)) 135 goto err; 136 137 do { 138 /* get random k */ 139 do 140 if (!BN_rand_range(k, order)) { 141 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, 142 ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED); 143 goto err; 144 } 145 while (BN_is_zero(k)) ; 146 147 /* 148 * We do not want timing information to leak the length of k, so we 149 * compute G*k using an equivalent scalar of fixed bit-length. 150 * 151 * We unconditionally perform both of these additions to prevent a 152 * small timing information leakage. We then choose the sum that is 153 * one bit longer than the order. This guarantees the code 154 * path used in the constant time implementations elsewhere. 155 * 156 * TODO: revisit the BN_copy aiming for a memory access agnostic 157 * conditional copy. 158 */ 159 if (!BN_add(r, k, order) 160 || !BN_add(X, r, order) 161 || !BN_copy(k, BN_num_bits(r) > order_bits ? r : X)) 162 goto err; 163 164 /* compute r the x-coordinate of generator * k */ 165 if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) { 166 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 167 goto err; 168 } 169 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == 170 NID_X9_62_prime_field) { 171 if (!EC_POINT_get_affine_coordinates_GFp 172 (group, tmp_point, X, NULL, ctx)) { 173 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 174 goto err; 175 } 176 } 177#ifndef OPENSSL_NO_EC2M 178 else { /* NID_X9_62_characteristic_two_field */ 179 180 if (!EC_POINT_get_affine_coordinates_GF2m(group, 181 tmp_point, X, NULL, 182 ctx)) { 183 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 184 goto err; 185 } 186 } 187#endif 188 if (!BN_nnmod(r, X, order, ctx)) { 189 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 190 goto err; 191 } 192 } 193 while (BN_is_zero(r)); 194 195 /* compute the inverse of k */ 196 if (EC_GROUP_get_mont_data(group) != NULL) { 197 /* 198 * We want inverse in constant time, therefore we utilize the fact 199 * order must be prime and use Fermats Little Theorem instead. 200 */ 201 if (!BN_set_word(X, 2)) { 202 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 203 goto err; 204 } 205 if (!BN_mod_sub(X, order, X, order, ctx)) { 206 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 207 goto err; 208 } 209 BN_set_flags(X, BN_FLG_CONSTTIME); 210 if (!BN_mod_exp_mont_consttime 211 (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) { 212 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 213 goto err; 214 } 215 } else { 216 if (!BN_mod_inverse(k, k, order, ctx)) { 217 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 218 goto err; 219 } 220 } 221 222 /* clear old values if necessary */ 223 if (*rp != NULL) 224 BN_clear_free(*rp); 225 if (*kinvp != NULL) 226 BN_clear_free(*kinvp); 227 /* save the pre-computed values */ 228 *rp = r; 229 *kinvp = k; 230 ret = 1; 231 err: 232 if (!ret) { 233 if (k != NULL) 234 BN_clear_free(k); 235 if (r != NULL) 236 BN_clear_free(r); 237 } 238 if (ctx_in == NULL) 239 BN_CTX_free(ctx); 240 if (order != NULL) 241 BN_free(order); 242 if (tmp_point != NULL) 243 EC_POINT_free(tmp_point); 244 if (X) 245 BN_clear_free(X); 246 return (ret); 247} 248 249static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len, 250 const BIGNUM *in_kinv, const BIGNUM *in_r, 251 EC_KEY *eckey) 252{ 253 int ok = 0, i; 254 BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL; 255 const BIGNUM *ckinv; 256 BN_CTX *ctx = NULL; 257 const EC_GROUP *group; 258 ECDSA_SIG *ret; 259 ECDSA_DATA *ecdsa; 260 const BIGNUM *priv_key; 261 262 ecdsa = ecdsa_check(eckey); 263 group = EC_KEY_get0_group(eckey); 264 priv_key = EC_KEY_get0_private_key(eckey); 265 266 if (group == NULL || priv_key == NULL || ecdsa == NULL) { 267 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER); 268 return NULL; 269 } 270 271 ret = ECDSA_SIG_new(); 272 if (!ret) { 273 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE); 274 return NULL; 275 } 276 s = ret->s; 277 278 if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL || 279 (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) { 280 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE); 281 goto err; 282 } 283 284 if (!EC_GROUP_get_order(group, order, ctx)) { 285 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB); 286 goto err; 287 } 288 i = BN_num_bits(order); 289 /* 290 * Need to truncate digest if it is too long: first truncate whole bytes. 291 */ 292 if (8 * dgst_len > i) 293 dgst_len = (i + 7) / 8; 294 if (!BN_bin2bn(dgst, dgst_len, m)) { 295 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 296 goto err; 297 } 298 /* If still too long truncate remaining bits with a shift */ 299 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) { 300 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 301 goto err; 302 } 303 do { 304 if (in_kinv == NULL || in_r == NULL) { 305 if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) { 306 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_ECDSA_LIB); 307 goto err; 308 } 309 ckinv = kinv; 310 } else { 311 ckinv = in_kinv; 312 if (BN_copy(ret->r, in_r) == NULL) { 313 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE); 314 goto err; 315 } 316 } 317 318 if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) { 319 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 320 goto err; 321 } 322 if (!BN_mod_add_quick(s, tmp, m, order)) { 323 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 324 goto err; 325 } 326 if (!BN_mod_mul(s, s, ckinv, order, ctx)) { 327 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 328 goto err; 329 } 330 if (BN_is_zero(s)) { 331 /* 332 * if kinv and r have been supplied by the caller don't to 333 * generate new kinv and r values 334 */ 335 if (in_kinv != NULL && in_r != NULL) { 336 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, 337 ECDSA_R_NEED_NEW_SETUP_VALUES); 338 goto err; 339 } 340 } else 341 /* s != 0 => we have a valid signature */ 342 break; 343 } 344 while (1); 345 346 ok = 1; 347 err: 348 if (!ok) { 349 ECDSA_SIG_free(ret); 350 ret = NULL; 351 } 352 if (ctx) 353 BN_CTX_free(ctx); 354 if (m) 355 BN_clear_free(m); 356 if (tmp) 357 BN_clear_free(tmp); 358 if (order) 359 BN_free(order); 360 if (kinv) 361 BN_clear_free(kinv); 362 return ret; 363} 364 365static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len, 366 const ECDSA_SIG *sig, EC_KEY *eckey) 367{ 368 int ret = -1, i; 369 BN_CTX *ctx; 370 BIGNUM *order, *u1, *u2, *m, *X; 371 EC_POINT *point = NULL; 372 const EC_GROUP *group; 373 const EC_POINT *pub_key; 374 375 /* check input values */ 376 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL || 377 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) { 378 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS); 379 return -1; 380 } 381 382 ctx = BN_CTX_new(); 383 if (!ctx) { 384 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE); 385 return -1; 386 } 387 BN_CTX_start(ctx); 388 order = BN_CTX_get(ctx); 389 u1 = BN_CTX_get(ctx); 390 u2 = BN_CTX_get(ctx); 391 m = BN_CTX_get(ctx); 392 X = BN_CTX_get(ctx); 393 if (!X) { 394 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 395 goto err; 396 } 397 398 if (!EC_GROUP_get_order(group, order, ctx)) { 399 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 400 goto err; 401 } 402 403 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 404 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) || 405 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) { 406 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE); 407 ret = 0; /* signature is invalid */ 408 goto err; 409 } 410 /* calculate tmp1 = inv(S) mod order */ 411 if (!BN_mod_inverse(u2, sig->s, order, ctx)) { 412 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 413 goto err; 414 } 415 /* digest -> m */ 416 i = BN_num_bits(order); 417 /* 418 * Need to truncate digest if it is too long: first truncate whole bytes. 419 */ 420 if (8 * dgst_len > i) 421 dgst_len = (i + 7) / 8; 422 if (!BN_bin2bn(dgst, dgst_len, m)) { 423 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 424 goto err; 425 } 426 /* If still too long truncate remaining bits with a shift */ 427 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) { 428 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 429 goto err; 430 } 431 /* u1 = m * tmp mod order */ 432 if (!BN_mod_mul(u1, m, u2, order, ctx)) { 433 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 434 goto err; 435 } 436 /* u2 = r * w mod q */ 437 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) { 438 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 439 goto err; 440 } 441 442 if ((point = EC_POINT_new(group)) == NULL) { 443 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE); 444 goto err; 445 } 446 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) { 447 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 448 goto err; 449 } 450 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == 451 NID_X9_62_prime_field) { 452 if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) { 453 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 454 goto err; 455 } 456 } 457#ifndef OPENSSL_NO_EC2M 458 else { /* NID_X9_62_characteristic_two_field */ 459 460 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) { 461 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 462 goto err; 463 } 464 } 465#endif 466 if (!BN_nnmod(u1, X, order, ctx)) { 467 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 468 goto err; 469 } 470 /* if the signature is correct u1 is equal to sig->r */ 471 ret = (BN_ucmp(u1, sig->r) == 0); 472 err: 473 BN_CTX_end(ctx); 474 BN_CTX_free(ctx); 475 if (point) 476 EC_POINT_free(point); 477 return ret; 478} 479