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 /* compute r the x-coordinate of generator * k */ 146 if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) { 147 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB); 148 goto err; 149 } 150 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == 151 NID_X9_62_prime_field) { 152 if (!EC_POINT_get_affine_coordinates_GFp(group, 153 tmp_point, X, NULL, ctx)) { 154 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, 155 ERR_R_EC_LIB); 156 goto err; 157 } 158 } 159 #ifndef OPENSSL_NO_EC2M 160 else /* NID_X9_62_characteristic_two_field */ 161 { 162 if (!EC_POINT_get_affine_coordinates_GF2m(group, 163 tmp_point, X, NULL, ctx)) { 164 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, 165 ERR_R_EC_LIB); 166 goto err; 167 } 168 } 169 #endif 170 if (!BN_nnmod(r, X, order, ctx)) { 171 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 172 goto err; 173 } 174 } while (BN_is_zero(r)); 175 176 /* compute the inverse of k */ 177 if (!BN_mod_inverse(k, k, order, ctx)) { 178 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB); 179 goto err; 180 } 181 /* clear old values if necessary */ 182 BN_clear_free(*rp); 183 BN_clear_free(*kinvp); 184 /* save the pre-computed values */ 185 *rp = r; 186 *kinvp = k; 187 ret = 1; 188 189 err: 190 if (!ret) { 191 BN_clear_free(k); 192 BN_clear_free(r); 193 } 194 if (ctx_in == NULL) 195 BN_CTX_free(ctx); 196 BN_free(order); 197 EC_POINT_free(tmp_point); 198 BN_clear_free(X); 199 return (ret); 200 } 201 202 203 static ECDSA_SIG * 204 ecdsa_do_sign(const unsigned char *dgst, int dgst_len, 205 const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey) 206 { 207 int ok = 0, i; 208 BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL; 209 const BIGNUM *ckinv; 210 BN_CTX *ctx = NULL; 211 const EC_GROUP *group; 212 ECDSA_SIG *ret; 213 ECDSA_DATA *ecdsa; 214 const BIGNUM *priv_key; 215 216 ecdsa = ecdsa_check(eckey); 217 group = EC_KEY_get0_group(eckey); 218 priv_key = EC_KEY_get0_private_key(eckey); 219 220 if (group == NULL || priv_key == NULL || ecdsa == NULL) { 221 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER); 222 return NULL; 223 } 224 225 ret = ECDSA_SIG_new(); 226 if (!ret) { 227 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE); 228 return NULL; 229 } 230 s = ret->s; 231 232 if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL || 233 (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) { 234 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE); 235 goto err; 236 } 237 238 if (!EC_GROUP_get_order(group, order, ctx)) { 239 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB); 240 goto err; 241 } 242 i = BN_num_bits(order); 243 /* Need to truncate digest if it is too long: first truncate whole 244 * bytes. 245 */ 246 if (8 * dgst_len > i) 247 dgst_len = (i + 7)/8; 248 if (!BN_bin2bn(dgst, dgst_len, m)) { 249 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 250 goto err; 251 } 252 /* If still too long truncate remaining bits with a shift */ 253 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) { 254 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 255 goto err; 256 } 257 do { 258 if (in_kinv == NULL || in_r == NULL) { 259 if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) { 260 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, 261 ERR_R_ECDSA_LIB); 262 goto err; 263 } 264 ckinv = kinv; 265 } else { 266 ckinv = in_kinv; 267 if (BN_copy(ret->r, in_r) == NULL) { 268 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, 269 ERR_R_MALLOC_FAILURE); 270 goto err; 271 } 272 } 273 274 if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) { 275 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 276 goto err; 277 } 278 if (!BN_mod_add_quick(s, tmp, m, order)) { 279 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 280 goto err; 281 } 282 if (!BN_mod_mul(s, s, ckinv, order, ctx)) { 283 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB); 284 goto err; 285 } 286 if (BN_is_zero(s)) { 287 /* if kinv and r have been supplied by the caller 288 * don't to generate new kinv and r values */ 289 if (in_kinv != NULL && in_r != NULL) { 290 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, 291 ECDSA_R_NEED_NEW_SETUP_VALUES); 292 goto err; 293 } 294 } else 295 /* s != 0 => we have a valid signature */ 296 break; 297 } while (1); 298 299 ok = 1; 300 301 err: 302 if (!ok) { 303 ECDSA_SIG_free(ret); 304 ret = NULL; 305 } 306 BN_CTX_free(ctx); 307 BN_clear_free(m); 308 BN_clear_free(tmp); 309 BN_free(order); 310 BN_clear_free(kinv); 311 return ret; 312 } 313 314 static int 315 ecdsa_do_verify(const unsigned char *dgst, int dgst_len, const ECDSA_SIG *sig, 316 EC_KEY *eckey) 317 { 318 int ret = -1, i; 319 BN_CTX *ctx; 320 BIGNUM *order, *u1, *u2, *m, *X; 321 EC_POINT *point = NULL; 322 const EC_GROUP *group; 323 const EC_POINT *pub_key; 324 325 /* check input values */ 326 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL || 327 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) { 328 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS); 329 return -1; 330 } 331 332 ctx = BN_CTX_new(); 333 if (!ctx) { 334 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE); 335 return -1; 336 } 337 BN_CTX_start(ctx); 338 order = BN_CTX_get(ctx); 339 u1 = BN_CTX_get(ctx); 340 u2 = BN_CTX_get(ctx); 341 m = BN_CTX_get(ctx); 342 X = BN_CTX_get(ctx); 343 if (!X) { 344 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 345 goto err; 346 } 347 348 if (!EC_GROUP_get_order(group, order, ctx)) { 349 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 350 goto err; 351 } 352 353 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) || 354 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) || 355 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) { 356 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE); 357 ret = 0; /* signature is invalid */ 358 goto err; 359 } 360 /* calculate tmp1 = inv(S) mod order */ 361 if (!BN_mod_inverse(u2, sig->s, order, ctx)) { 362 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 363 goto err; 364 } 365 /* digest -> m */ 366 i = BN_num_bits(order); 367 /* Need to truncate digest if it is too long: first truncate whole 368 * bytes. 369 */ 370 if (8 * dgst_len > i) 371 dgst_len = (i + 7)/8; 372 if (!BN_bin2bn(dgst, dgst_len, m)) { 373 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 374 goto err; 375 } 376 /* If still too long truncate remaining bits with a shift */ 377 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) { 378 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 379 goto err; 380 } 381 /* u1 = m * tmp mod order */ 382 if (!BN_mod_mul(u1, m, u2, order, ctx)) { 383 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 384 goto err; 385 } 386 /* u2 = r * w mod q */ 387 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) { 388 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 389 goto err; 390 } 391 392 if ((point = EC_POINT_new(group)) == NULL) { 393 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE); 394 goto err; 395 } 396 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) { 397 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 398 goto err; 399 } 400 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == 401 NID_X9_62_prime_field) { 402 if (!EC_POINT_get_affine_coordinates_GFp(group, 403 point, X, NULL, ctx)) { 404 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 405 goto err; 406 } 407 } 408 #ifndef OPENSSL_NO_EC2M 409 else /* NID_X9_62_characteristic_two_field */ 410 { 411 if (!EC_POINT_get_affine_coordinates_GF2m(group, 412 point, X, NULL, ctx)) { 413 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB); 414 goto err; 415 } 416 } 417 #endif 418 if (!BN_nnmod(u1, X, order, ctx)) { 419 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB); 420 goto err; 421 } 422 /* if the signature is correct u1 is equal to sig->r */ 423 ret = (BN_ucmp(u1, sig->r) == 0); 424 425 err: 426 BN_CTX_end(ctx); 427 BN_CTX_free(ctx); 428 EC_POINT_free(point); 429 return ret; 430 } 431