crypto/ec/ecdsa_ossl.c

   1 /*
   2  * Written by Nils Larsch for the OpenSSL project
   3  */
   4 /* ====================================================================
   5  * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  *
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in
  16  *    the documentation and/or other materials provided with the
  17  *    distribution.
  18  *
  19  * 3. All advertising materials mentioning features or use of this
  20  *    software must display the following acknowledgment:
  21  *    "This product includes software developed by the OpenSSL Project
  22  *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
  23  *
  24  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  25  *    endorse or promote products derived from this software without
  26  *    prior written permission. For written permission, please contact
  27  *    openssl-core@OpenSSL.org.
  28  *
  29  * 5. Products derived from this software may not be called "OpenSSL"
  30  *    nor may "OpenSSL" appear in their names without prior written
  31  *    permission of the OpenSSL Project.
  32  *
  33  * 6. Redistributions of any form whatsoever must retain the following
  34  *    acknowledgment:
  35  *    "This product includes software developed by the OpenSSL Project
  36  *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
  37  *
  38  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  39  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  40  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  41  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  42  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  43  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  44  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  45  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  46  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  47  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  48  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  49  * OF THE POSSIBILITY OF SUCH DAMAGE.
  50  * ====================================================================
  51  *
  52  * This product includes cryptographic software written by Eric Young
  53  * (eay@cryptsoft.com).  This product includes software written by Tim
  54  * Hudson (tjh@cryptsoft.com).
  55  *
  56  */
  57
  58 #include <string.h>
  59 #include <openssl/err.h>
  60 #include <openssl/obj_mac.h>
  61 #include <openssl/bn.h>
  62 #include <openssl/rand.h>
  63 #include <openssl/ec.h>
  64 #include "ec_lcl.h"
  65
  66 int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
  67                     unsigned char *sig, unsigned int *siglen,
  68                     const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
  69 {
  70     ECDSA_SIG *s;
  71     RAND_seed(dgst, dlen);
  72     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
  73     if (s == NULL) {
  74         *siglen = 0;
  75         return 0;
  76     }
  77     *siglen = i2d_ECDSA_SIG(s, &sig);
  78     ECDSA_SIG_free(s);
  79     return 1;
  80 }
  81
  82 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
  83                             BIGNUM **kinvp, BIGNUM **rp,
  84                             const unsigned char *dgst, int dlen)
  85 {
  86     BN_CTX *ctx = NULL;
  87     BIGNUM *k = NULL, *r = NULL, *order = NULL, *X = NULL;
  88     EC_POINT *tmp_point = NULL;
  89     const EC_GROUP *group;
  90     int ret = 0;
  91
  92     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
  93         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
  94         return 0;
  95     }
  96
  97     if (ctx_in == NULL) {
  98         if ((ctx = BN_CTX_new()) == NULL) {
  99             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
 100             return 0;
 101         }
 102     } else
 103         ctx = ctx_in;
 104
 105     k = BN_new();               /* this value is later returned in *kinvp */
 106     r = BN_new();               /* this value is later returned in *rp */
 107     order = BN_new();
 108     X = BN_new();
 109     if (k == NULL || r == NULL || order == NULL || X == NULL) {
 110         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
 111         goto err;
 112     }
 113     if ((tmp_point = EC_POINT_new(group)) == NULL) {
 114         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 115         goto err;
 116     }
 117     if (!EC_GROUP_get_order(group, order, ctx)) {
 118         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 119         goto err;
 120     }
 121
 122     do {
 123         /* get random k */
 124         do
 125             if (dgst != NULL) {
 126                 if (!BN_generate_dsa_nonce
 127                     (k, order, EC_KEY_get0_private_key(eckey), dgst, dlen,
 128                      ctx)) {
 129                     ECerr(EC_F_ECDSA_SIGN_SETUP,
 130                              EC_R_RANDOM_NUMBER_GENERATION_FAILED);
 131                     goto err;
 132                 }
 133             } else {
 134                 if (!BN_rand_range(k, order)) {
 135                     ECerr(EC_F_ECDSA_SIGN_SETUP,
 136                              EC_R_RANDOM_NUMBER_GENERATION_FAILED);
 137                     goto err;
 138                 }
 139             }
 140         while (BN_is_zero(k));
 141
 142         /*
 143          * We do not want timing information to leak the length of k, so we
 144          * compute G*k using an equivalent scalar of fixed bit-length.
 145          */
 146
 147         if (!BN_add(k, k, order))
 148             goto err;
 149         if (BN_num_bits(k) <= BN_num_bits(order))
 150             if (!BN_add(k, k, order))
 151                 goto err;
 152
 153         /* compute r the x-coordinate of generator * k */
 154         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
 155             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 156             goto err;
 157         }
 158         if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
 159             NID_X9_62_prime_field) {
 160             if (!EC_POINT_get_affine_coordinates_GFp
 161                 (group, tmp_point, X, NULL, ctx)) {
 162                 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 163                 goto err;
 164             }
 165         }
 166 #ifndef OPENSSL_NO_EC2M
 167         else {                  /* NID_X9_62_characteristic_two_field */
 168
 169             if (!EC_POINT_get_affine_coordinates_GF2m(group,
 170                                                       tmp_point, X, NULL,
 171                                                       ctx)) {
 172                 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 173                 goto err;
 174             }
 175         }
 176 #endif
 177         if (!BN_nnmod(r, X, order, ctx)) {
 178             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 179             goto err;
 180         }
 181     }
 182     while (BN_is_zero(r));
 183
 184     /* compute the inverse of k */
 185     if (EC_GROUP_get_mont_data(group) != NULL) {
 186         /*
 187          * We want inverse in constant time, therefore we utilize the fact
 188          * order must be prime and use Fermats Little Theorem instead.
 189          */
 190         if (!BN_set_word(X, 2)) {
 191             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 192             goto err;
 193         }
 194         if (!BN_mod_sub(X, order, X, order, ctx)) {
 195             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 196             goto err;
 197         }
 198         BN_set_flags(X, BN_FLG_CONSTTIME);
 199         if (!BN_mod_exp_mont_consttime
 200             (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
 201             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 202             goto err;
 203         }
 204     } else {
 205         if (!BN_mod_inverse(k, k, order, ctx)) {
 206             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 207             goto err;
 208         }
 209     }
 210
 211     /* clear old values if necessary */
 212     BN_clear_free(*rp);
 213     BN_clear_free(*kinvp);
 214     /* save the pre-computed values  */
 215     *rp = r;
 216     *kinvp = k;
 217     ret = 1;
 218  err:
 219     if (!ret) {
 220         BN_clear_free(k);
 221         BN_clear_free(r);
 222     }
 223     if (ctx != ctx_in)
 224         BN_CTX_free(ctx);
 225     BN_free(order);
 226     EC_POINT_free(tmp_point);
 227     BN_clear_free(X);
 228     return (ret);
 229 }
 230
 231 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 232                           BIGNUM **rp)
 233 {
 234     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
 235 }
 236
 237 ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
 238                                const BIGNUM *in_kinv, const BIGNUM *in_r,
 239                                EC_KEY *eckey)
 240 {
 241     int ok = 0, i;
 242     BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;
 243     const BIGNUM *ckinv;
 244     BN_CTX *ctx = NULL;
 245     const EC_GROUP *group;
 246     ECDSA_SIG *ret;
 247     const BIGNUM *priv_key;
 248
 249     group = EC_KEY_get0_group(eckey);
 250     priv_key = EC_KEY_get0_private_key(eckey);
 251
 252     if (group == NULL || priv_key == NULL) {
 253         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
 254         return NULL;
 255     }
 256
 257     ret = ECDSA_SIG_new();
 258     if (ret == NULL) {
 259         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, 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         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 267         goto err;
 268     }
 269
 270     if (!EC_GROUP_get_order(group, order, ctx)) {
 271         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, 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         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, 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         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, 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, dgst, dgst_len)) {
 292                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, 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                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 300                 goto err;
 301             }
 302         }
 303
 304         if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
 305             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 306             goto err;
 307         }
 308         if (!BN_mod_add_quick(s, tmp, m, order)) {
 309             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 310             goto err;
 311         }
 312         if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
 313             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, 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                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
 323                 goto err;
 324             }
 325         } else
 326             /* s != 0 => we have a valid signature */
 327             break;
 328     }
 329     while (1);
 330
 331     ok = 1;
 332  err:
 333     if (!ok) {
 334         ECDSA_SIG_free(ret);
 335         ret = NULL;
 336     }
 337     BN_CTX_free(ctx);
 338     BN_clear_free(m);
 339     BN_clear_free(tmp);
 340     BN_free(order);
 341     BN_clear_free(kinv);
 342     return ret;
 343 }
 344
 345 /*-
 346  * returns
 347  *      1: correct signature
 348  *      0: incorrect signature
 349  *     -1: error
 350  */
 351 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
 352                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
 353 {
 354     ECDSA_SIG *s;
 355     const unsigned char *p = sigbuf;
 356     unsigned char *der = NULL;
 357     int derlen = -1;
 358     int ret = -1;
 359
 360     s = ECDSA_SIG_new();
 361     if (s == NULL)
 362         return (ret);
 363     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
 364         goto err;
 365     /* Ensure signature uses DER and doesn't have trailing garbage */
 366     derlen = i2d_ECDSA_SIG(s, &der);
 367     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
 368         goto err;
 369     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
 370  err:
 371     OPENSSL_clear_free(der, derlen);
 372     ECDSA_SIG_free(s);
 373     return (ret);
 374 }
 375
 376 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
 377                           const ECDSA_SIG *sig, EC_KEY *eckey)
 378 {
 379     int ret = -1, i;
 380     BN_CTX *ctx;
 381     BIGNUM *order, *u1, *u2, *m, *X;
 382     EC_POINT *point = NULL;
 383     const EC_GROUP *group;
 384     const EC_POINT *pub_key;
 385
 386     /* check input values */
 387     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
 388         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
 389         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
 390         return -1;
 391     }
 392
 393     ctx = BN_CTX_new();
 394     if (ctx == NULL) {
 395         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
 396         return -1;
 397     }
 398     BN_CTX_start(ctx);
 399     order = BN_CTX_get(ctx);
 400     u1 = BN_CTX_get(ctx);
 401     u2 = BN_CTX_get(ctx);
 402     m = BN_CTX_get(ctx);
 403     X = BN_CTX_get(ctx);
 404     if (X == NULL) {
 405         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 406         goto err;
 407     }
 408
 409     if (!EC_GROUP_get_order(group, order, ctx)) {
 410         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 411         goto err;
 412     }
 413
 414     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 415         BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
 416         BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
 417         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
 418         ret = 0;                /* signature is invalid */
 419         goto err;
 420     }
 421     /* calculate tmp1 = inv(S) mod order */
 422     if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
 423         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 424         goto err;
 425     }
 426     /* digest -> m */
 427     i = BN_num_bits(order);
 428     /*
 429      * Need to truncate digest if it is too long: first truncate whole bytes.
 430      */
 431     if (8 * dgst_len > i)
 432         dgst_len = (i + 7) / 8;
 433     if (!BN_bin2bn(dgst, dgst_len, m)) {
 434         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 435         goto err;
 436     }
 437     /* If still too long truncate remaining bits with a shift */
 438     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 439         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 440         goto err;
 441     }
 442     /* u1 = m * tmp mod order */
 443     if (!BN_mod_mul(u1, m, u2, order, ctx)) {
 444         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 445         goto err;
 446     }
 447     /* u2 = r * w mod q */
 448     if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
 449         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 450         goto err;
 451     }
 452
 453     if ((point = EC_POINT_new(group)) == NULL) {
 454         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
 455         goto err;
 456     }
 457     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
 458         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 459         goto err;
 460     }
 461     if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
 462         NID_X9_62_prime_field) {
 463         if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
 464             ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 465             goto err;
 466         }
 467     }
 468 #ifndef OPENSSL_NO_EC2M
 469     else {                      /* NID_X9_62_characteristic_two_field */
 470
 471         if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
 472             ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 473             goto err;
 474         }
 475     }
 476 #endif
 477     if (!BN_nnmod(u1, X, order, ctx)) {
 478         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 479         goto err;
 480     }
 481     /*  if the signature is correct u1 is equal to sig->r */
 482     ret = (BN_ucmp(u1, sig->r) == 0);
 483  err:
 484     BN_CTX_end(ctx);
 485     BN_CTX_free(ctx);
 486     EC_POINT_free(point);
 487     return ret;
 488 }