crypto/ec/ecdsa_ossl.c

   1 /*
   2  * Copyright 2002-2021 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (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 /*
  11  * ECDSA low level APIs are deprecated for public use, but still ok for
  12  * internal use.
  13  */
  14 #include "internal/deprecated.h"
  15
  16 #include <string.h>
  17 #include <openssl/err.h>
  18 #include <openssl/obj_mac.h>
  19 #include <openssl/rand.h>
  20 #include "crypto/bn.h"
  21 #include "ec_local.h"
  22 #include "internal/deterministic_nonce.h"
  23
  24 #define MIN_ECDSA_SIGN_ORDERBITS 64
  25 /*
  26  * It is highly unlikely that a retry will happen,
  27  * Multiple retries would indicate that something is wrong
  28  * with the group parameters (which would normally only happen
  29  * with a bad custom group).
  30  */
  31 #define MAX_ECDSA_SIGN_RETRIES 8
  32
  33 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
  34                             BIGNUM **kinvp, BIGNUM **rp,
  35                             const unsigned char *dgst, int dlen,
  36                             unsigned int nonce_type, const char *digestname,
  37                             OSSL_LIB_CTX *libctx, const char *propq);
  38
  39 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
  40                           BIGNUM **rp)
  41 {
  42     if (eckey->group->meth->ecdsa_sign_setup == NULL) {
  43         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);
  44         return 0;
  45     }
  46
  47     return eckey->group->meth->ecdsa_sign_setup(eckey, ctx_in, kinvp, rp);
  48 }
  49
  50 ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
  51                                const BIGNUM *in_kinv, const BIGNUM *in_r,
  52                                EC_KEY *eckey)
  53 {
  54     if (eckey->group->meth->ecdsa_sign_sig == NULL) {
  55         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);
  56         return NULL;
  57     }
  58
  59     return eckey->group->meth->ecdsa_sign_sig(dgst, dgst_len,
  60                                               in_kinv, in_r, eckey);
  61 }
  62
  63 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
  64                           const ECDSA_SIG *sig, EC_KEY *eckey)
  65 {
  66     if (eckey->group->meth->ecdsa_verify_sig == NULL) {
  67         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);
  68         return 0;
  69     }
  70
  71     return eckey->group->meth->ecdsa_verify_sig(dgst, dgst_len, sig, eckey);
  72 }
  73
  74 int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
  75                     unsigned char *sig, unsigned int *siglen,
  76                     const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
  77 {
  78     ECDSA_SIG *s;
  79
  80     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
  81     if (s == NULL) {
  82         *siglen = 0;
  83         return 0;
  84     }
  85     *siglen = i2d_ECDSA_SIG(s, &sig);
  86     ECDSA_SIG_free(s);
  87     return 1;
  88 }
  89
  90 int ossl_ecdsa_deterministic_sign(const unsigned char *dgst, int dlen,
  91                                   unsigned char *sig, unsigned int *siglen,
  92                                   EC_KEY *eckey, unsigned int nonce_type,
  93                                   const char *digestname,
  94                                   OSSL_LIB_CTX *libctx, const char *propq)
  95 {
  96     ECDSA_SIG *s;
  97     BIGNUM *kinv = NULL, *r = NULL;
  98     int ret = 0;
  99
 100     *siglen = 0;
 101     if (!ecdsa_sign_setup(eckey, NULL, &kinv, &r, dgst, dlen,
 102                           nonce_type, digestname, libctx, propq))
 103         return 0;
 104
 105     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
 106     if (s == NULL)
 107         goto end;
 108
 109     *siglen = i2d_ECDSA_SIG(s, &sig);
 110     ECDSA_SIG_free(s);
 111     ret = 1;
 112 end:
 113     BN_clear_free(kinv);
 114     BN_clear_free(r);
 115     return ret;
 116 }
 117
 118 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
 119                             BIGNUM **kinvp, BIGNUM **rp,
 120                             const unsigned char *dgst, int dlen,
 121                             unsigned int nonce_type, const char *digestname,
 122                             OSSL_LIB_CTX *libctx, const char *propq)
 123 {
 124     BN_CTX *ctx = NULL;
 125     BIGNUM *k = NULL, *r = NULL, *X = NULL;
 126     const BIGNUM *order;
 127     EC_POINT *tmp_point = NULL;
 128     const EC_GROUP *group;
 129     int ret = 0;
 130     int order_bits;
 131     const BIGNUM *priv_key;
 132
 133     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
 134         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
 135         return 0;
 136     }
 137     if ((priv_key = EC_KEY_get0_private_key(eckey)) == NULL) {
 138         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
 139         return 0;
 140     }
 141
 142     if (!EC_KEY_can_sign(eckey)) {
 143         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 144         return 0;
 145     }
 146
 147     if ((ctx = ctx_in) == NULL) {
 148         if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL) {
 149             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 150             return 0;
 151         }
 152     }
 153
 154     k = BN_secure_new();        /* this value is later returned in *kinvp */
 155     r = BN_new();               /* this value is later returned in *rp */
 156     X = BN_new();
 157     if (k == NULL || r == NULL || X == NULL) {
 158         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 159         goto err;
 160     }
 161     if ((tmp_point = EC_POINT_new(group)) == NULL) {
 162         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 163         goto err;
 164     }
 165     order = EC_GROUP_get0_order(group);
 166
 167     /* Preallocate space */
 168     order_bits = BN_num_bits(order);
 169     /* Check the number of bits here so that an infinite loop is not possible */
 170     if (order_bits < MIN_ECDSA_SIGN_ORDERBITS
 171         || !BN_set_bit(k, order_bits)
 172         || !BN_set_bit(r, order_bits)
 173         || !BN_set_bit(X, order_bits))
 174         goto err;
 175
 176     do {
 177         /* get random or deterministic value of k */
 178         do {
 179             int res = 0;
 180
 181             if (dgst != NULL) {
 182                 if (nonce_type == 1) {
 183 #ifndef FIPS_MODULE
 184                     res = ossl_gen_deterministic_nonce_rfc6979(k, order,
 185                                                                priv_key,
 186                                                                dgst, dlen,
 187                                                                digestname,
 188                                                                libctx, propq);
 189 #endif
 190                 } else {
 191                     res = BN_generate_dsa_nonce(k, order, priv_key, dgst, dlen,
 192                                                 ctx);
 193                 }
 194             } else {
 195                 res = BN_priv_rand_range_ex(k, order, 0, ctx);
 196             }
 197             if (!res) {
 198                 ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
 199                 goto err;
 200             }
 201         } while (BN_is_zero(k));
 202
 203         /* compute r the x-coordinate of generator * k */
 204         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
 205             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 206             goto err;
 207         }
 208
 209         if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {
 210             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 211             goto err;
 212         }
 213
 214         if (!BN_nnmod(r, X, order, ctx)) {
 215             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 216             goto err;
 217         }
 218     } while (BN_is_zero(r));
 219
 220     /* compute the inverse of k */
 221     if (!ossl_ec_group_do_inverse_ord(group, k, k, ctx)) {
 222         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 223         goto err;
 224     }
 225
 226     /* clear old values if necessary */
 227     BN_clear_free(*rp);
 228     BN_clear_free(*kinvp);
 229     /* save the pre-computed values  */
 230     *rp = r;
 231     *kinvp = k;
 232     ret = 1;
 233  err:
 234     if (!ret) {
 235         BN_clear_free(k);
 236         BN_clear_free(r);
 237     }
 238     if (ctx != ctx_in)
 239         BN_CTX_free(ctx);
 240     EC_POINT_free(tmp_point);
 241     BN_clear_free(X);
 242     return ret;
 243 }
 244
 245 int ossl_ecdsa_simple_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 246                                  BIGNUM **rp)
 247 {
 248     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0,
 249                             0, NULL, NULL, NULL);
 250 }
 251
 252 ECDSA_SIG *ossl_ecdsa_simple_sign_sig(const unsigned char *dgst, int dgst_len,
 253                                       const BIGNUM *in_kinv, const BIGNUM *in_r,
 254                                       EC_KEY *eckey)
 255 {
 256     int ok = 0, i;
 257     int retries = 0;
 258     BIGNUM *kinv = NULL, *s, *m = NULL;
 259     const BIGNUM *order, *ckinv;
 260     BN_CTX *ctx = NULL;
 261     const EC_GROUP *group;
 262     ECDSA_SIG *ret;
 263     const BIGNUM *priv_key;
 264
 265     group = EC_KEY_get0_group(eckey);
 266     priv_key = EC_KEY_get0_private_key(eckey);
 267
 268     if (group == NULL) {
 269         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
 270         return NULL;
 271     }
 272     if (priv_key == NULL) {
 273         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
 274         return NULL;
 275     }
 276
 277     if (!EC_KEY_can_sign(eckey)) {
 278         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 279         return NULL;
 280     }
 281
 282     ret = ECDSA_SIG_new();
 283     if (ret == NULL) {
 284         ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);
 285         return NULL;
 286     }
 287     ret->r = BN_new();
 288     ret->s = BN_new();
 289     if (ret->r == NULL || ret->s == NULL) {
 290         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 291         goto err;
 292     }
 293     s = ret->s;
 294
 295     if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL
 296         || (m = BN_new()) == NULL) {
 297         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 298         goto err;
 299     }
 300
 301     order = EC_GROUP_get0_order(group);
 302     i = BN_num_bits(order);
 303     /*
 304      * Need to truncate digest if it is too long: first truncate whole bytes.
 305      */
 306     if (8 * dgst_len > i)
 307         dgst_len = (i + 7) / 8;
 308     if (!BN_bin2bn(dgst, dgst_len, m)) {
 309         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 310         goto err;
 311     }
 312     /* If still too long, truncate remaining bits with a shift */
 313     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 314         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 315         goto err;
 316     }
 317     do {
 318         if (in_kinv == NULL || in_r == NULL) {
 319             if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len,
 320                                   0, NULL, NULL, NULL)) {
 321                 ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);
 322                 goto err;
 323             }
 324             ckinv = kinv;
 325         } else {
 326             ckinv = in_kinv;
 327             if (BN_copy(ret->r, in_r) == NULL) {
 328                 ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 329                 goto err;
 330             }
 331         }
 332
 333         /*
 334          * With only one multiplicant being in Montgomery domain
 335          * multiplication yields real result without post-conversion.
 336          * Also note that all operations but last are performed with
 337          * zero-padded vectors. Last operation, BN_mod_mul_montgomery
 338          * below, returns user-visible value with removed zero padding.
 339          */
 340         if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
 341             || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
 342             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 343             goto err;
 344         }
 345         if (!bn_mod_add_fixed_top(s, s, m, order)) {
 346             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 347             goto err;
 348         }
 349         /*
 350          * |s| can still be larger than modulus, because |m| can be. In
 351          * such case we count on Montgomery reduction to tie it up.
 352          */
 353         if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
 354             || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
 355             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 356             goto err;
 357         }
 358
 359         if (BN_is_zero(s)) {
 360             /*
 361              * if kinv and r have been supplied by the caller, don't
 362              * generate new kinv and r values
 363              */
 364             if (in_kinv != NULL && in_r != NULL) {
 365                 ERR_raise(ERR_LIB_EC, EC_R_NEED_NEW_SETUP_VALUES);
 366                 goto err;
 367             }
 368             /* Avoid infinite loops cause by invalid group parameters */
 369             if (retries++ > MAX_ECDSA_SIGN_RETRIES) {
 370                 ERR_raise(ERR_LIB_EC, EC_R_TOO_MANY_RETRIES);
 371                 goto err;
 372             }
 373         } else {
 374             /* s != 0 => we have a valid signature */
 375             break;
 376         }
 377     } while (1);
 378
 379     ok = 1;
 380  err:
 381     if (!ok) {
 382         ECDSA_SIG_free(ret);
 383         ret = NULL;
 384     }
 385     BN_CTX_free(ctx);
 386     BN_clear_free(m);
 387     BN_clear_free(kinv);
 388     return ret;
 389 }
 390
 391 /*-
 392  * returns
 393  *      1: correct signature
 394  *      0: incorrect signature
 395  *     -1: error
 396  */
 397 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
 398                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
 399 {
 400     ECDSA_SIG *s;
 401     const unsigned char *p = sigbuf;
 402     unsigned char *der = NULL;
 403     int derlen = -1;
 404     int ret = -1;
 405
 406     s = ECDSA_SIG_new();
 407     if (s == NULL)
 408         return ret;
 409     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
 410         goto err;
 411     /* Ensure signature uses DER and doesn't have trailing garbage */
 412     derlen = i2d_ECDSA_SIG(s, &der);
 413     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
 414         goto err;
 415     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
 416  err:
 417     OPENSSL_free(der);
 418     ECDSA_SIG_free(s);
 419     return ret;
 420 }
 421
 422 int ossl_ecdsa_simple_verify_sig(const unsigned char *dgst, int dgst_len,
 423                                  const ECDSA_SIG *sig, EC_KEY *eckey)
 424 {
 425     int ret = -1, i;
 426     BN_CTX *ctx;
 427     const BIGNUM *order;
 428     BIGNUM *u1, *u2, *m, *X;
 429     EC_POINT *point = NULL;
 430     const EC_GROUP *group;
 431     const EC_POINT *pub_key;
 432
 433     /* check input values */
 434     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
 435         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
 436         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PARAMETERS);
 437         return -1;
 438     }
 439
 440     if (!EC_KEY_can_sign(eckey)) {
 441         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 442         return -1;
 443     }
 444
 445     ctx = BN_CTX_new_ex(eckey->libctx);
 446     if (ctx == NULL) {
 447         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 448         return -1;
 449     }
 450     BN_CTX_start(ctx);
 451     u1 = BN_CTX_get(ctx);
 452     u2 = BN_CTX_get(ctx);
 453     m = BN_CTX_get(ctx);
 454     X = BN_CTX_get(ctx);
 455     if (X == NULL) {
 456         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 457         goto err;
 458     }
 459
 460     order = EC_GROUP_get0_order(group);
 461     if (order == NULL) {
 462         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 463         goto err;
 464     }
 465
 466     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 467         BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
 468         BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
 469         ERR_raise(ERR_LIB_EC, EC_R_BAD_SIGNATURE);
 470         ret = 0;                /* signature is invalid */
 471         goto err;
 472     }
 473     /* calculate tmp1 = inv(S) mod order */
 474     if (!ossl_ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {
 475         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 476         goto err;
 477     }
 478     /* digest -> m */
 479     i = BN_num_bits(order);
 480     /*
 481      * Need to truncate digest if it is too long: first truncate whole bytes.
 482      */
 483     if (8 * dgst_len > i)
 484         dgst_len = (i + 7) / 8;
 485     if (!BN_bin2bn(dgst, dgst_len, m)) {
 486         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 487         goto err;
 488     }
 489     /* If still too long truncate remaining bits with a shift */
 490     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 491         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 492         goto err;
 493     }
 494     /* u1 = m * tmp mod order */
 495     if (!BN_mod_mul(u1, m, u2, order, ctx)) {
 496         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 497         goto err;
 498     }
 499     /* u2 = r * w mod q */
 500     if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
 501         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 502         goto err;
 503     }
 504
 505     if ((point = EC_POINT_new(group)) == NULL) {
 506         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 507         goto err;
 508     }
 509     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
 510         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 511         goto err;
 512     }
 513
 514     if (!EC_POINT_get_affine_coordinates(group, point, X, NULL, ctx)) {
 515         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 516         goto err;
 517     }
 518
 519     if (!BN_nnmod(u1, X, order, ctx)) {
 520         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 521         goto err;
 522     }
 523     /*  if the signature is correct u1 is equal to sig->r */
 524     ret = (BN_ucmp(u1, sig->r) == 0);
 525  err:
 526     BN_CTX_end(ctx);
 527     BN_CTX_free(ctx);
 528     EC_POINT_free(point);
 529     return ret;
 530 }