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 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 235static 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 351static 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