crypto/ec/ecdsa_ossl.c

   1 /*
   2  * Copyright 2002-2023 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     if (sig == NULL && (kinv == NULL || r == NULL)) {
  81         *siglen = ECDSA_size(eckey);
  82         return 1;
  83     }
  84
  85     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
  86     if (s == NULL) {
  87         *siglen = 0;
  88         return 0;
  89     }
  90     *siglen = i2d_ECDSA_SIG(s, sig != NULL ? &sig : NULL);
  91     ECDSA_SIG_free(s);
  92     return 1;
  93 }
  94
  95 int ossl_ecdsa_deterministic_sign(const unsigned char *dgst, int dlen,
  96                                   unsigned char *sig, unsigned int *siglen,
  97                                   EC_KEY *eckey, unsigned int nonce_type,
  98                                   const char *digestname,
  99                                   OSSL_LIB_CTX *libctx, const char *propq)
 100 {
 101     ECDSA_SIG *s;
 102     BIGNUM *kinv = NULL, *r = NULL;
 103     int ret = 0;
 104
 105     if (sig == NULL) {
 106         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
 107         return 0;
 108     }
 109
 110     *siglen = 0;
 111     if (!ecdsa_sign_setup(eckey, NULL, &kinv, &r, dgst, dlen,
 112                           nonce_type, digestname, libctx, propq))
 113         return 0;
 114
 115     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
 116     if (s == NULL)
 117         goto end;
 118
 119     *siglen = i2d_ECDSA_SIG(s, &sig);
 120     ECDSA_SIG_free(s);
 121     ret = 1;
 122 end:
 123     BN_clear_free(kinv);
 124     BN_clear_free(r);
 125     return ret;
 126 }
 127
 128 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
 129                             BIGNUM **kinvp, BIGNUM **rp,
 130                             const unsigned char *dgst, int dlen,
 131                             unsigned int nonce_type, const char *digestname,
 132                             OSSL_LIB_CTX *libctx, const char *propq)
 133 {
 134     BN_CTX *ctx = NULL;
 135     BIGNUM *k = NULL, *r = NULL, *X = NULL;
 136     const BIGNUM *order;
 137     EC_POINT *tmp_point = NULL;
 138     const EC_GROUP *group;
 139     int ret = 0;
 140     int order_bits;
 141     const BIGNUM *priv_key;
 142
 143     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
 144         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
 145         return 0;
 146     }
 147     if ((priv_key = EC_KEY_get0_private_key(eckey)) == NULL) {
 148         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
 149         return 0;
 150     }
 151
 152     if (!EC_KEY_can_sign(eckey)) {
 153         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 154         return 0;
 155     }
 156
 157     if ((ctx = ctx_in) == NULL) {
 158         if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL) {
 159             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 160             return 0;
 161         }
 162     }
 163
 164     k = BN_secure_new();        /* this value is later returned in *kinvp */
 165     r = BN_new();               /* this value is later returned in *rp */
 166     X = BN_new();
 167     if (k == NULL || r == NULL || X == NULL) {
 168         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 169         goto err;
 170     }
 171     if ((tmp_point = EC_POINT_new(group)) == NULL) {
 172         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 173         goto err;
 174     }
 175     order = EC_GROUP_get0_order(group);
 176
 177     /* Preallocate space */
 178     order_bits = BN_num_bits(order);
 179     /* Check the number of bits here so that an infinite loop is not possible */
 180     if (order_bits < MIN_ECDSA_SIGN_ORDERBITS
 181         || !BN_set_bit(k, order_bits)
 182         || !BN_set_bit(r, order_bits)
 183         || !BN_set_bit(X, order_bits))
 184         goto err;
 185
 186     do {
 187         /* get random or deterministic value of k */
 188         do {
 189             int res = 0;
 190
 191             if (dgst != NULL) {
 192                 if (nonce_type == 1) {
 193 #ifndef FIPS_MODULE
 194                     res = ossl_gen_deterministic_nonce_rfc6979(k, order,
 195                                                                priv_key,
 196                                                                dgst, dlen,
 197                                                                digestname,
 198                                                                libctx, propq);
 199 #endif
 200                 } else {
 201                     res = ossl_bn_gen_dsa_nonce_fixed_top(k, order, priv_key,
 202                                                           dgst, dlen, ctx);
 203                 }
 204             } else {
 205                 res = ossl_bn_priv_rand_range_fixed_top(k, order, 0, ctx);
 206             }
 207             if (!res) {
 208                 ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
 209                 goto err;
 210             }
 211         } while (ossl_bn_is_word_fixed_top(k, 0));
 212
 213         /* compute r the x-coordinate of generator * k */
 214         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
 215             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 216             goto err;
 217         }
 218
 219         if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {
 220             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 221             goto err;
 222         }
 223
 224         if (!BN_nnmod(r, X, order, ctx)) {
 225             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 226             goto err;
 227         }
 228     } while (BN_is_zero(r));
 229
 230     /* compute the inverse of k */
 231     if (!ossl_ec_group_do_inverse_ord(group, k, k, ctx)) {
 232         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 233         goto err;
 234     }
 235
 236     /* clear old values if necessary */
 237     BN_clear_free(*rp);
 238     BN_clear_free(*kinvp);
 239     /* save the pre-computed values  */
 240     *rp = r;
 241     *kinvp = k;
 242     ret = 1;
 243  err:
 244     if (!ret) {
 245         BN_clear_free(k);
 246         BN_clear_free(r);
 247     }
 248     if (ctx != ctx_in)
 249         BN_CTX_free(ctx);
 250     EC_POINT_free(tmp_point);
 251     BN_clear_free(X);
 252     return ret;
 253 }
 254
 255 int ossl_ecdsa_simple_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 256                                  BIGNUM **rp)
 257 {
 258     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0,
 259                             0, NULL, NULL, NULL);
 260 }
 261
 262 ECDSA_SIG *ossl_ecdsa_simple_sign_sig(const unsigned char *dgst, int dgst_len,
 263                                       const BIGNUM *in_kinv, const BIGNUM *in_r,
 264                                       EC_KEY *eckey)
 265 {
 266     int ok = 0, i;
 267     int retries = 0;
 268     BIGNUM *kinv = NULL, *s, *m = NULL;
 269     const BIGNUM *order, *ckinv;
 270     BN_CTX *ctx = NULL;
 271     const EC_GROUP *group;
 272     ECDSA_SIG *ret;
 273     const BIGNUM *priv_key;
 274
 275     group = EC_KEY_get0_group(eckey);
 276     priv_key = EC_KEY_get0_private_key(eckey);
 277
 278     if (group == NULL) {
 279         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
 280         return NULL;
 281     }
 282     if (priv_key == NULL) {
 283         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
 284         return NULL;
 285     }
 286
 287     if (!EC_KEY_can_sign(eckey)) {
 288         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 289         return NULL;
 290     }
 291
 292     ret = ECDSA_SIG_new();
 293     if (ret == NULL) {
 294         ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);
 295         return NULL;
 296     }
 297     ret->r = BN_new();
 298     ret->s = BN_new();
 299     if (ret->r == NULL || ret->s == NULL) {
 300         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 301         goto err;
 302     }
 303     s = ret->s;
 304
 305     if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL
 306         || (m = BN_new()) == NULL) {
 307         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 308         goto err;
 309     }
 310
 311     order = EC_GROUP_get0_order(group);
 312     i = BN_num_bits(order);
 313     /*
 314      * Need to truncate digest if it is too long: first truncate whole bytes.
 315      */
 316     if (8 * dgst_len > i)
 317         dgst_len = (i + 7) / 8;
 318     if (!BN_bin2bn(dgst, dgst_len, m)) {
 319         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 320         goto err;
 321     }
 322     /* If still too long, truncate remaining bits with a shift */
 323     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 324         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 325         goto err;
 326     }
 327     do {
 328         if (in_kinv == NULL || in_r == NULL) {
 329             if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len,
 330                                   0, NULL, NULL, NULL)) {
 331                 ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);
 332                 goto err;
 333             }
 334             ckinv = kinv;
 335         } else {
 336             ckinv = in_kinv;
 337             if (BN_copy(ret->r, in_r) == NULL) {
 338                 ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 339                 goto err;
 340             }
 341         }
 342
 343         /*
 344          * With only one multiplicant being in Montgomery domain
 345          * multiplication yields real result without post-conversion.
 346          * Also note that all operations but last are performed with
 347          * zero-padded vectors. Last operation, BN_mod_mul_montgomery
 348          * below, returns user-visible value with removed zero padding.
 349          */
 350         if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
 351             || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
 352             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 353             goto err;
 354         }
 355         if (!bn_mod_add_fixed_top(s, s, m, order)) {
 356             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 357             goto err;
 358         }
 359         /*
 360          * |s| can still be larger than modulus, because |m| can be. In
 361          * such case we count on Montgomery reduction to tie it up.
 362          */
 363         if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
 364             || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
 365             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 366             goto err;
 367         }
 368
 369         if (BN_is_zero(s)) {
 370             /*
 371              * if kinv and r have been supplied by the caller, don't
 372              * generate new kinv and r values
 373              */
 374             if (in_kinv != NULL && in_r != NULL) {
 375                 ERR_raise(ERR_LIB_EC, EC_R_NEED_NEW_SETUP_VALUES);
 376                 goto err;
 377             }
 378             /* Avoid infinite loops cause by invalid group parameters */
 379             if (retries++ > MAX_ECDSA_SIGN_RETRIES) {
 380                 ERR_raise(ERR_LIB_EC, EC_R_TOO_MANY_RETRIES);
 381                 goto err;
 382             }
 383         } else {
 384             /* s != 0 => we have a valid signature */
 385             break;
 386         }
 387     } while (1);
 388
 389     ok = 1;
 390  err:
 391     if (!ok) {
 392         ECDSA_SIG_free(ret);
 393         ret = NULL;
 394     }
 395     BN_CTX_free(ctx);
 396     BN_clear_free(m);
 397     BN_clear_free(kinv);
 398     return ret;
 399 }
 400
 401 /*-
 402  * returns
 403  *      1: correct signature
 404  *      0: incorrect signature
 405  *     -1: error
 406  */
 407 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
 408                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
 409 {
 410     ECDSA_SIG *s;
 411     const unsigned char *p = sigbuf;
 412     unsigned char *der = NULL;
 413     int derlen = -1;
 414     int ret = -1;
 415
 416     s = ECDSA_SIG_new();
 417     if (s == NULL)
 418         return ret;
 419     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
 420         goto err;
 421     /* Ensure signature uses DER and doesn't have trailing garbage */
 422     derlen = i2d_ECDSA_SIG(s, &der);
 423     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
 424         goto err;
 425     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
 426  err:
 427     OPENSSL_free(der);
 428     ECDSA_SIG_free(s);
 429     return ret;
 430 }
 431
 432 int ossl_ecdsa_simple_verify_sig(const unsigned char *dgst, int dgst_len,
 433                                  const ECDSA_SIG *sig, EC_KEY *eckey)
 434 {
 435     int ret = -1, i;
 436     BN_CTX *ctx;
 437     const BIGNUM *order;
 438     BIGNUM *u1, *u2, *m, *X;
 439     EC_POINT *point = NULL;
 440     const EC_GROUP *group;
 441     const EC_POINT *pub_key;
 442
 443     /* check input values */
 444     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
 445         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
 446         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PARAMETERS);
 447         return -1;
 448     }
 449
 450     if (!EC_KEY_can_sign(eckey)) {
 451         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 452         return -1;
 453     }
 454
 455     ctx = BN_CTX_new_ex(eckey->libctx);
 456     if (ctx == NULL) {
 457         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 458         return -1;
 459     }
 460     BN_CTX_start(ctx);
 461     u1 = BN_CTX_get(ctx);
 462     u2 = BN_CTX_get(ctx);
 463     m = BN_CTX_get(ctx);
 464     X = BN_CTX_get(ctx);
 465     if (X == NULL) {
 466         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 467         goto err;
 468     }
 469
 470     order = EC_GROUP_get0_order(group);
 471     if (order == NULL) {
 472         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 473         goto err;
 474     }
 475
 476     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
 477         BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
 478         BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
 479         ERR_raise(ERR_LIB_EC, EC_R_BAD_SIGNATURE);
 480         ret = 0;                /* signature is invalid */
 481         goto err;
 482     }
 483     /* calculate tmp1 = inv(S) mod order */
 484     if (!ossl_ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {
 485         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 486         goto err;
 487     }
 488     /* digest -> m */
 489     i = BN_num_bits(order);
 490     /*
 491      * Need to truncate digest if it is too long: first truncate whole bytes.
 492      */
 493     if (8 * dgst_len > i)
 494         dgst_len = (i + 7) / 8;
 495     if (!BN_bin2bn(dgst, dgst_len, m)) {
 496         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 497         goto err;
 498     }
 499     /* If still too long truncate remaining bits with a shift */
 500     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 501         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 502         goto err;
 503     }
 504     /* u1 = m * tmp mod order */
 505     if (!BN_mod_mul(u1, m, u2, order, ctx)) {
 506         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 507         goto err;
 508     }
 509     /* u2 = r * w mod q */
 510     if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
 511         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 512         goto err;
 513     }
 514
 515     if ((point = EC_POINT_new(group)) == NULL) {
 516         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 517         goto err;
 518     }
 519     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
 520         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 521         goto err;
 522     }
 523
 524     if (!EC_POINT_get_affine_coordinates(group, point, X, NULL, ctx)) {
 525         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
 526         goto err;
 527     }
 528
 529     if (!BN_nnmod(u1, X, order, ctx)) {
 530         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
 531         goto err;
 532     }
 533     /*  if the signature is correct u1 is equal to sig->r */
 534     ret = (BN_ucmp(u1, sig->r) == 0);
 535  err:
 536     BN_CTX_end(ctx);
 537     BN_CTX_free(ctx);
 538     EC_POINT_free(point);
 539     return ret;
 540 }