1 /* $OpenBSD: ecs_ossl.c,v 1.5 2014/07/12 16:03:37 miod Exp $ */ 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 <openssl/opensslconf.h> 60 61 #include "ecs_locl.h" 62 #include <openssl/err.h> 63 #include <openssl/obj_mac.h> 64 #include <openssl/bn.h> 65 66 static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen, 67 const BIGNUM *, const BIGNUM *, EC_KEY *eckey); 68 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, 69 BIGNUM **rp); 70 static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len, 71 const ECDSA_SIG *sig, EC_KEY *eckey); 72 73 static ECDSA_METHOD openssl_ecdsa_meth = { 74 .name = "OpenSSL ECDSA method", 75 .ecdsa_do_sign = ecdsa_do_sign, 76 .ecdsa_sign_setup = ecdsa_sign_setup, 77 .ecdsa_do_verify = ecdsa_do_verify 78 }; 79 80 const ECDSA_METHOD * 81 ECDSA_OpenSSL(void) 82 { 83 return &openssl_ecdsa_meth; 84 } 85 86 static int 87 ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 88 { 89 BN_CTX *ctx = NULL; 90 BIGNUM *k = NULL, *r = NULL, *order = NULL, *X = NULL; 91 EC_POINT *tmp_point = NULL; 92 const EC_GROUP *group; 93 int ret = 0; 94 95 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) { 96 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER); 97 return 0; 98 } 99 100 if (ctx_in == NULL) { 101 if ((ctx = BN_CTX_new()) == NULL) { 102 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, 103 ERR_R_MALLOC_FAILURE); 104 return 0; 105 } 106 } else 107 ctx = ctx_in; 108 109 k = BN_new(); /* this value is later returned in *kinvp */ 110 r = BN_new(); /* this value is later returned in *rp */ 111 order = BN_new(); 112 X = BN_new(); 113 if (!k || !r || !order || !X) { 114 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE); 115 goto err; 116 } 117 if ((tmp_point = EC_POINT_new(group)) == NULL) { 118 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 119 goto err; 120 } 121 if (!EC_GROUP_get_order(group, order, ctx)) { 122 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 123 goto err; 124 } 125 126 do { 127 /* get random k */ 128 do 129 if (!BN_rand_range(k, order)) { 130 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, 131 ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED); 132 goto err; 133 } 134 while (BN_is_zero(k)); 135 136 /* We do not want timing information to leak the length of k, 137 * so we compute G*k using an equivalent scalar of fixed 138 * bit-length. */ 139 if (!BN_add(k, k, order)) 140 goto err; 141 if (BN_num_bits(k) <= BN_num_bits(order)) 142 if (!BN_add(k, k, order)) 143 goto err; 144 145 BN_set_flags(k, BN_FLG_CONSTTIME); 146 147 /* compute r the x-coordinate of generator * k */ 148 if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) { 149 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 150 goto err; 151 } 152 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == 153 NID_X9_62_prime_field) { 154 if (!EC_POINT_get_affine_coordinates_GFp(group, 155 tmp_point, X, NULL, ctx)) { 156 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, 157 ERR_R_EC_LIB); 158 goto err; 159 } 160 } 161 #ifndef OPENSSL_NO_EC2M 162 else /* NID_X9_62_characteristic_two_field */ 163 { 164 if (!EC_POINT_get_affine_coordinates_GF2m(group, 165 tmp_point, X, NULL, ctx)) { 166 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, 167 ERR_R_EC_LIB); 168 goto err; 169 } 170 } 171 #endif 172 if (!BN_nnmod(r, X, order, ctx)) { 173 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 174 goto err; 175 } 176 } while (BN_is_zero(r)); 177 178 /* compute the inverse of k */ 179 if (!BN_mod_inverse(k, k, order, ctx)) { 180 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 181 goto err; 182 } 183 /* clear old values if necessary */ 184 BN_clear_free(*rp); 185 BN_clear_free(*kinvp); 186 /* save the pre-computed values */ 187 *rp = r; 188 *kinvp = k; 189 ret = 1; 190 191 err: 192 if (!ret) { 193 BN_clear_free(k); 194 BN_clear_free(r); 195 } 196 if (ctx_in == NULL) 197 BN_CTX_free(ctx); 198 BN_free(order); 199 EC_POINT_free(tmp_point); 200 BN_clear_free(X); 201 return (ret); 202 } 203 204 205 static ECDSA_SIG * 206 ecdsa_do_sign(const unsigned char *dgst, int dgst_len, 207 const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey) 208 { 209 int ok = 0, i; 210 BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL; 211 const BIGNUM *ckinv; 212 BN_CTX *ctx = NULL; 213 const EC_GROUP *group; 214 ECDSA_SIG *ret; 215 ECDSA_DATA *ecdsa; 216 const BIGNUM *priv_key; 217 218 ecdsa = ecdsa_check(eckey); 219 group = EC_KEY_get0_group(eckey); 220 priv_key = EC_KEY_get0_private_key(eckey); 221 222 if (group == NULL || priv_key == NULL || ecdsa == NULL) { 223 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER); 224 return NULL; 225 } 226 227 ret = ECDSA_SIG_new(); 228 if (!ret) { 229 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE); 230 return NULL; 231 } 232 s = ret->s; 233 234 if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL || 235 (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) { 236 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE); 237 goto err; 238 } 239 240 if (!EC_GROUP_get_order(group, order, ctx)) { 241 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB); 242 goto err; 243 } 244 i = BN_num_bits(order); 245 /* Need to truncate digest if it is too long: first truncate whole 246 * bytes. 247 */ 248 if (8 * dgst_len > i) 249 dgst_len = (i + 7)/8; 250 if (!BN_bin2bn(dgst, dgst_len, m)) { 251 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 252 goto err; 253 } 254 /* If still too long truncate remaining bits with a shift */ 255 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) { 256 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 257 goto err; 258 } 259 do { 260 if (in_kinv == NULL || in_r == NULL) { 261 if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) { 262 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, 263 ERR_R_ECDSA_LIB); 264 goto err; 265 } 266 ckinv = kinv; 267 } else { 268 ckinv = in_kinv; 269 if (BN_copy(ret->r, in_r) == NULL) { 270 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, 271 ERR_R_MALLOC_FAILURE); 272 goto err; 273 } 274 } 275 276 if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) { 277 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 278 goto err; 279 } 280 if (!BN_mod_add_quick(s, tmp, m, order)) { 281 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 282 goto err; 283 } 284 if (!BN_mod_mul(s, s, ckinv, order, ctx)) { 285 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 286 goto err; 287 } 288 if (BN_is_zero(s)) { 289 /* if kinv and r have been supplied by the caller 290 * don't to generate new kinv and r values */ 291 if (in_kinv != NULL && in_r != NULL) { 292 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, 293 ECDSA_R_NEED_NEW_SETUP_VALUES); 294 goto err; 295 } 296 } else 297 /* s != 0 => we have a valid signature */ 298 break; 299 } while (1); 300 301 ok = 1; 302 303 err: 304 if (!ok) { 305 ECDSA_SIG_free(ret); 306 ret = NULL; 307 } 308 BN_CTX_free(ctx); 309 BN_clear_free(m); 310 BN_clear_free(tmp); 311 BN_free(order); 312 BN_clear_free(kinv); 313 return ret; 314 } 315 316 static int 317 ecdsa_do_verify(const unsigned char *dgst, int dgst_len, const ECDSA_SIG *sig, 318 EC_KEY *eckey) 319 { 320 int ret = -1, i; 321 BN_CTX *ctx; 322 BIGNUM *order, *u1, *u2, *m, *X; 323 EC_POINT *point = NULL; 324 const EC_GROUP *group; 325 const EC_POINT *pub_key; 326 327 /* check input values */ 328 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL || 329 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) { 330 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS); 331 return -1; 332 } 333 334 ctx = BN_CTX_new(); 335 if (!ctx) { 336 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE); 337 return -1; 338 } 339 BN_CTX_start(ctx); 340 order = BN_CTX_get(ctx); 341 u1 = BN_CTX_get(ctx); 342 u2 = BN_CTX_get(ctx); 343 m = BN_CTX_get(ctx); 344 X = BN_CTX_get(ctx); 345 if (!X) { 346 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 347 goto err; 348 } 349 350 if (!EC_GROUP_get_order(group, order, ctx)) { 351 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 352 goto err; 353 } 354 355 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 356 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) || 357 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) { 358 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE); 359 ret = 0; /* signature is invalid */ 360 goto err; 361 } 362 /* calculate tmp1 = inv(S) mod order */ 363 if (!BN_mod_inverse(u2, sig->s, order, ctx)) { 364 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 365 goto err; 366 } 367 /* digest -> m */ 368 i = BN_num_bits(order); 369 /* Need to truncate digest if it is too long: first truncate whole 370 * bytes. 371 */ 372 if (8 * dgst_len > i) 373 dgst_len = (i + 7)/8; 374 if (!BN_bin2bn(dgst, dgst_len, m)) { 375 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 376 goto err; 377 } 378 /* If still too long truncate remaining bits with a shift */ 379 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) { 380 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 381 goto err; 382 } 383 /* u1 = m * tmp mod order */ 384 if (!BN_mod_mul(u1, m, u2, order, ctx)) { 385 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 386 goto err; 387 } 388 /* u2 = r * w mod q */ 389 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) { 390 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 391 goto err; 392 } 393 394 if ((point = EC_POINT_new(group)) == NULL) { 395 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE); 396 goto err; 397 } 398 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) { 399 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 400 goto err; 401 } 402 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == 403 NID_X9_62_prime_field) { 404 if (!EC_POINT_get_affine_coordinates_GFp(group, 405 point, X, NULL, ctx)) { 406 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 407 goto err; 408 } 409 } 410 #ifndef OPENSSL_NO_EC2M 411 else /* NID_X9_62_characteristic_two_field */ 412 { 413 if (!EC_POINT_get_affine_coordinates_GF2m(group, 414 point, X, NULL, ctx)) { 415 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 416 goto err; 417 } 418 } 419 #endif 420 if (!BN_nnmod(u1, X, order, ctx)) { 421 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 422 goto err; 423 } 424 /* if the signature is correct u1 is equal to sig->r */ 425 ret = (BN_ucmp(u1, sig->r) == 0); 426 427 err: 428 BN_CTX_end(ctx); 429 BN_CTX_free(ctx); 430 EC_POINT_free(point); 431 return ret; 432 } 433