crypto/ec/ecdsa_ossl.c

   1 /*
   2  * Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <string.h>
  11 #include <openssl/err.h>
  12 #include <openssl/obj_mac.h>
  13 #include <openssl/bn.h>
  14 #include <openssl/rand.h>
  15 #include <openssl/ec.h>
  16 #include "ec_lcl.h"
  17
  18 int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
  19                     unsigned char *sig, unsigned int *siglen,
  20                     const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
  21 {
  22     ECDSA_SIG *s;
  23     RAND_seed(dgst, dlen);
  24     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
  25     if (s == NULL) {
  26         *siglen = 0;
  27         return 0;
  28     }
  29     *siglen = i2d_ECDSA_SIG(s, &sig);
  30     ECDSA_SIG_free(s);
  31     return 1;
  32 }
  33
  34 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
  35                             BIGNUM **kinvp, BIGNUM **rp,
  36                             const unsigned char *dgst, int dlen)
  37 {
  38     BN_CTX *ctx = NULL;
  39     BIGNUM *k = NULL, *r = NULL, *X = NULL;
  40     const BIGNUM *order;
  41     EC_POINT *tmp_point = NULL;
  42     const EC_GROUP *group;
  43     int ret = 0;
  44
  45     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
  46         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
  47         return 0;
  48     }
  49
  50     if (!EC_KEY_can_sign(eckey)) {
  51         ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
  52         return 0;
  53     }
  54
  55     if (ctx_in == NULL) {
  56         if ((ctx = BN_CTX_new()) == NULL) {
  57             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
  58             return 0;
  59         }
  60     } else
  61         ctx = ctx_in;
  62
  63     k = BN_new();               /* this value is later returned in *kinvp */
  64     r = BN_new();               /* this value is later returned in *rp */
  65     X = BN_new();
  66     if (k == NULL || r == NULL || X == NULL) {
  67         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
  68         goto err;
  69     }
  70     if ((tmp_point = EC_POINT_new(group)) == NULL) {
  71         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
  72         goto err;
  73     }
  74     order = EC_GROUP_get0_order(group);
  75     if (order == NULL) {
  76         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
  77         goto err;
  78     }
  79
  80     do {
  81         /* get random k */
  82         do
  83             if (dgst != NULL) {
  84                 if (!BN_generate_dsa_nonce
  85                     (k, order, EC_KEY_get0_private_key(eckey), dgst, dlen,
  86                      ctx)) {
  87                     ECerr(EC_F_ECDSA_SIGN_SETUP,
  88                              EC_R_RANDOM_NUMBER_GENERATION_FAILED);
  89                     goto err;
  90                 }
  91             } else {
  92                 if (!BN_rand_range(k, order)) {
  93                     ECerr(EC_F_ECDSA_SIGN_SETUP,
  94                              EC_R_RANDOM_NUMBER_GENERATION_FAILED);
  95                     goto err;
  96                 }
  97             }
  98         while (BN_is_zero(k));
  99
 100         /*
 101          * We do not want timing information to leak the length of k, so we
 102          * compute G*k using an equivalent scalar of fixed bit-length.
 103          */
 104
 105         if (!BN_add(k, k, order))
 106             goto err;
 107         if (BN_num_bits(k) <= BN_num_bits(order))
 108             if (!BN_add(k, k, order))
 109                 goto err;
 110
 111         /* compute r the x-coordinate of generator * k */
 112         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
 113             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 114             goto err;
 115         }
 116         if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
 117             NID_X9_62_prime_field) {
 118             if (!EC_POINT_get_affine_coordinates_GFp
 119                 (group, tmp_point, X, NULL, ctx)) {
 120                 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 121                 goto err;
 122             }
 123         }
 124 #ifndef OPENSSL_NO_EC2M
 125         else {                  /* NID_X9_62_characteristic_two_field */
 126
 127             if (!EC_POINT_get_affine_coordinates_GF2m(group,
 128                                                       tmp_point, X, NULL,
 129                                                       ctx)) {
 130                 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 131                 goto err;
 132             }
 133         }
 134 #endif
 135         if (!BN_nnmod(r, X, order, ctx)) {
 136             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 137             goto err;
 138         }
 139     }
 140     while (BN_is_zero(r));
 141
 142     /* compute the inverse of k */
 143     if (EC_GROUP_get_mont_data(group) != NULL) {
 144         /*
 145          * We want inverse in constant time, therefore we utilize the fact
 146          * order must be prime and use Fermats Little Theorem instead.
 147          */
 148         if (!BN_set_word(X, 2)) {
 149             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 150             goto err;
 151         }
 152         if (!BN_mod_sub(X, order, X, order, ctx)) {
 153             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 154             goto err;
 155         }
 156         BN_set_flags(X, BN_FLG_CONSTTIME);
 157         if (!BN_mod_exp_mont_consttime
 158             (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
 159             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 160             goto err;
 161         }
 162     } else {
 163         if (!BN_mod_inverse(k, k, order, ctx)) {
 164             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 165             goto err;
 166         }
 167     }
 168
 169     /* clear old values if necessary */
 170     BN_clear_free(*rp);
 171     BN_clear_free(*kinvp);
 172     /* save the pre-computed values  */
 173     *rp = r;
 174     *kinvp = k;
 175     ret = 1;
 176  err:
 177     if (!ret) {
 178         BN_clear_free(k);
 179         BN_clear_free(r);
 180     }
 181     if (ctx != ctx_in)
 182         BN_CTX_free(ctx);
 183     EC_POINT_free(tmp_point);
 184     BN_clear_free(X);
 185     return (ret);
 186 }
 187
 188 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 189                           BIGNUM **rp)
 190 {
 191     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
 192 }
 193
 194 ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
 195                                const BIGNUM *in_kinv, const BIGNUM *in_r,
 196                                EC_KEY *eckey)
 197 {
 198     int ok = 0, i;
 199     BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL;
 200     const BIGNUM *order, *ckinv;
 201     BN_CTX *ctx = NULL;
 202     const EC_GROUP *group;
 203     ECDSA_SIG *ret;
 204     const BIGNUM *priv_key;
 205
 206     group = EC_KEY_get0_group(eckey);
 207     priv_key = EC_KEY_get0_private_key(eckey);
 208
 209     if (group == NULL || priv_key == NULL) {
 210         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
 211         return NULL;
 212     }
 213
 214     if (!EC_KEY_can_sign(eckey)) {
 215         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 216         return NULL;
 217     }
 218
 219     ret = ECDSA_SIG_new();
 220     if (ret == NULL) {
 221         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 222         return NULL;
 223     }
 224     s = ret->s;
 225
 226     if ((ctx = BN_CTX_new()) == NULL ||
 227         (tmp = BN_new()) == NULL || (m = BN_new()) == NULL) {
 228         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 229         goto err;
 230     }
 231
 232     order = EC_GROUP_get0_order(group);
 233     if (order == NULL) {
 234         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_EC_LIB);
 235         goto err;
 236     }
 237     i = BN_num_bits(order);
 238     /*
 239      * Need to truncate digest if it is too long: first truncate whole bytes.
 240      */
 241     if (8 * dgst_len > i)
 242         dgst_len = (i + 7) / 8;
 243     if (!BN_bin2bn(dgst, dgst_len, m)) {
 244         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 245         goto err;
 246     }
 247     /* If still too long truncate remaining bits with a shift */
 248     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 249         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 250         goto err;
 251     }
 252     do {
 253         if (in_kinv == NULL || in_r == NULL) {
 254             if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
 255                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
 256                 goto err;
 257             }
 258             ckinv = kinv;
 259         } else {
 260             ckinv = in_kinv;
 261             if (BN_copy(ret->r, in_r) == NULL) {
 262                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 263                 goto err;
 264             }
 265         }
 266
 267         if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx)) {
 268             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 269             goto err;
 270         }
 271         if (!BN_mod_add_quick(s, tmp, m, order)) {
 272             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 273             goto err;
 274         }
 275         if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
 276             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 277             goto err;
 278         }
 279         if (BN_is_zero(s)) {
 280             /*
 281              * if kinv and r have been supplied by the caller don't to
 282              * generate new kinv and r values
 283              */
 284             if (in_kinv != NULL && in_r != NULL) {
 285                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
 286                 goto err;
 287             }
 288         } else
 289             /* s != 0 => we have a valid signature */
 290             break;
 291     }
 292     while (1);
 293
 294     ok = 1;
 295  err:
 296     if (!ok) {
 297         ECDSA_SIG_free(ret);
 298         ret = NULL;
 299     }
 300     BN_CTX_free(ctx);
 301     BN_clear_free(m);
 302     BN_clear_free(tmp);
 303     BN_clear_free(kinv);
 304     return ret;
 305 }
 306
 307 /*-
 308  * returns
 309  *      1: correct signature
 310  *      0: incorrect signature
 311  *     -1: error
 312  */
 313 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
 314                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
 315 {
 316     ECDSA_SIG *s;
 317     const unsigned char *p = sigbuf;
 318     unsigned char *der = NULL;
 319     int derlen = -1;
 320     int ret = -1;
 321
 322     s = ECDSA_SIG_new();
 323     if (s == NULL)
 324         return (ret);
 325     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
 326         goto err;
 327     /* Ensure signature uses DER and doesn't have trailing garbage */
 328     derlen = i2d_ECDSA_SIG(s, &der);
 329     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
 330         goto err;
 331     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
 332  err:
 333     OPENSSL_clear_free(der, derlen);
 334     ECDSA_SIG_free(s);
 335     return (ret);
 336 }
 337
 338 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
 339                           const ECDSA_SIG *sig, EC_KEY *eckey)
 340 {
 341     int ret = -1, i;
 342     BN_CTX *ctx;
 343     const BIGNUM *order;
 344     BIGNUM *u1, *u2, *m, *X;
 345     EC_POINT *point = NULL;
 346     const EC_GROUP *group;
 347     const EC_POINT *pub_key;
 348
 349     /* check input values */
 350     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
 351         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
 352         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
 353         return -1;
 354     }
 355
 356     if (!EC_KEY_can_sign(eckey)) {
 357         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 358         return -1;
 359     }
 360
 361     ctx = BN_CTX_new();
 362     if (ctx == NULL) {
 363         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
 364         return -1;
 365     }
 366     BN_CTX_start(ctx);
 367     u1 = BN_CTX_get(ctx);
 368     u2 = BN_CTX_get(ctx);
 369     m = BN_CTX_get(ctx);
 370     X = BN_CTX_get(ctx);
 371     if (X == NULL) {
 372         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 373         goto err;
 374     }
 375
 376     order = EC_GROUP_get0_order(group);
 377     if (order == NULL) {
 378         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 379         goto err;
 380     }
 381
 382     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 383         BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
 384         BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
 385         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
 386         ret = 0;                /* signature is invalid */
 387         goto err;
 388     }
 389     /* calculate tmp1 = inv(S) mod order */
 390     if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
 391         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 392         goto err;
 393     }
 394     /* digest -> m */
 395     i = BN_num_bits(order);
 396     /*
 397      * Need to truncate digest if it is too long: first truncate whole bytes.
 398      */
 399     if (8 * dgst_len > i)
 400         dgst_len = (i + 7) / 8;
 401     if (!BN_bin2bn(dgst, dgst_len, m)) {
 402         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 403         goto err;
 404     }
 405     /* If still too long truncate remaining bits with a shift */
 406     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 407         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 408         goto err;
 409     }
 410     /* u1 = m * tmp mod order */
 411     if (!BN_mod_mul(u1, m, u2, order, ctx)) {
 412         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 413         goto err;
 414     }
 415     /* u2 = r * w mod q */
 416     if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
 417         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 418         goto err;
 419     }
 420
 421     if ((point = EC_POINT_new(group)) == NULL) {
 422         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
 423         goto err;
 424     }
 425     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
 426         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 427         goto err;
 428     }
 429     if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
 430         NID_X9_62_prime_field) {
 431         if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
 432             ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 433             goto err;
 434         }
 435     }
 436 #ifndef OPENSSL_NO_EC2M
 437     else {                      /* NID_X9_62_characteristic_two_field */
 438
 439         if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
 440             ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 441             goto err;
 442         }
 443     }
 444 #endif
 445     if (!BN_nnmod(u1, X, order, ctx)) {
 446         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 447         goto err;
 448     }
 449     /*  if the signature is correct u1 is equal to sig->r */
 450     ret = (BN_ucmp(u1, sig->r) == 0);
 451  err:
 452     BN_CTX_end(ctx);
 453     BN_CTX_free(ctx);
 454     EC_POINT_free(point);
 455     return ret;
 456 }