crypto/ec/ecdsa_ossl.c

   1 /*
   2  * Copyright 2002-2018 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/rand.h>
  14 #include "internal/bn_int.h"
  15 #include "ec_lcl.h"
  16
  17 int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
  18                     unsigned char *sig, unsigned int *siglen,
  19                     const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
  20 {
  21     ECDSA_SIG *s;
  22
  23     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
  24     if (s == NULL) {
  25         *siglen = 0;
  26         return 0;
  27     }
  28     *siglen = i2d_ECDSA_SIG(s, &sig);
  29     ECDSA_SIG_free(s);
  30     return 1;
  31 }
  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 {
  37     BN_CTX *ctx = NULL;
  38     BIGNUM *k = NULL, *r = NULL, *X = NULL;
  39     const BIGNUM *order;
  40     EC_POINT *tmp_point = NULL;
  41     const EC_GROUP *group;
  42     int ret = 0;
  43     int order_bits;
  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 = 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     }
  61
  62     k = BN_new();               /* this value is later returned in *kinvp */
  63     r = BN_new();               /* this value is later returned in *rp */
  64     X = BN_new();
  65     if (k == NULL || r == NULL || X == NULL) {
  66         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
  67         goto err;
  68     }
  69     if ((tmp_point = EC_POINT_new(group)) == NULL) {
  70         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
  71         goto err;
  72     }
  73     order = EC_GROUP_get0_order(group);
  74
  75     /* Preallocate space */
  76     order_bits = BN_num_bits(order);
  77     if (!BN_set_bit(k, order_bits)
  78         || !BN_set_bit(r, order_bits)
  79         || !BN_set_bit(X, order_bits))
  80         goto err;
  81
  82     do {
  83         /* get random k */
  84         do {
  85             if (dgst != NULL) {
  86                 if (!BN_generate_dsa_nonce(k, order,
  87                                            EC_KEY_get0_private_key(eckey),
  88                                            dgst, dlen, ctx)) {
  89                     ECerr(EC_F_ECDSA_SIGN_SETUP,
  90                           EC_R_RANDOM_NUMBER_GENERATION_FAILED);
  91                     goto err;
  92                 }
  93             } else {
  94                 if (!BN_priv_rand_range(k, order)) {
  95                     ECerr(EC_F_ECDSA_SIGN_SETUP,
  96                           EC_R_RANDOM_NUMBER_GENERATION_FAILED);
  97                     goto err;
  98                 }
  99             }
 100         } while (BN_is_zero(k));
 101
 102         /* compute r the x-coordinate of generator * k */
 103         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
 104             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 105             goto err;
 106         }
 107
 108         if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {
 109             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
 110             goto err;
 111         }
 112
 113         if (!BN_nnmod(r, X, order, ctx)) {
 114             ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 115             goto err;
 116         }
 117     } while (BN_is_zero(r));
 118
 119     /* compute the inverse of k */
 120     if (!ec_group_do_inverse_ord(group, k, k, ctx)) {
 121         ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
 122         goto err;
 123     }
 124
 125     /* clear old values if necessary */
 126     BN_clear_free(*rp);
 127     BN_clear_free(*kinvp);
 128     /* save the pre-computed values  */
 129     *rp = r;
 130     *kinvp = k;
 131     ret = 1;
 132  err:
 133     if (!ret) {
 134         BN_clear_free(k);
 135         BN_clear_free(r);
 136     }
 137     if (ctx != ctx_in)
 138         BN_CTX_free(ctx);
 139     EC_POINT_free(tmp_point);
 140     BN_clear_free(X);
 141     return ret;
 142 }
 143
 144 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
 145                           BIGNUM **rp)
 146 {
 147     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
 148 }
 149
 150 ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
 151                                const BIGNUM *in_kinv, const BIGNUM *in_r,
 152                                EC_KEY *eckey)
 153 {
 154     int ok = 0, i;
 155     BIGNUM *kinv = NULL, *s, *m = NULL;
 156     const BIGNUM *order, *ckinv;
 157     BN_CTX *ctx = NULL;
 158     const EC_GROUP *group;
 159     ECDSA_SIG *ret;
 160     const BIGNUM *priv_key;
 161
 162     group = EC_KEY_get0_group(eckey);
 163     priv_key = EC_KEY_get0_private_key(eckey);
 164
 165     if (group == NULL || priv_key == NULL) {
 166         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
 167         return NULL;
 168     }
 169
 170     if (!EC_KEY_can_sign(eckey)) {
 171         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 172         return NULL;
 173     }
 174
 175     ret = ECDSA_SIG_new();
 176     if (ret == NULL) {
 177         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 178         return NULL;
 179     }
 180     ret->r = BN_new();
 181     ret->s = BN_new();
 182     if (ret->r == NULL || ret->s == NULL) {
 183         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 184         goto err;
 185     }
 186     s = ret->s;
 187
 188     if ((ctx = BN_CTX_new()) == NULL
 189         || (m = BN_new()) == NULL) {
 190         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 191         goto err;
 192     }
 193
 194     order = EC_GROUP_get0_order(group);
 195     i = BN_num_bits(order);
 196     /*
 197      * Need to truncate digest if it is too long: first truncate whole bytes.
 198      */
 199     if (8 * dgst_len > i)
 200         dgst_len = (i + 7) / 8;
 201     if (!BN_bin2bn(dgst, dgst_len, m)) {
 202         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 203         goto err;
 204     }
 205     /* If still too long, truncate remaining bits with a shift */
 206     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
 207         ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 208         goto err;
 209     }
 210     do {
 211         if (in_kinv == NULL || in_r == NULL) {
 212             if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
 213                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
 214                 goto err;
 215             }
 216             ckinv = kinv;
 217         } else {
 218             ckinv = in_kinv;
 219             if (BN_copy(ret->r, in_r) == NULL) {
 220                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
 221                 goto err;
 222             }
 223         }
 224
 225         /*
 226          * With only one multiplicant being in Montgomery domain
 227          * multiplication yields real result without post-conversion.
 228          * Also note that all operations but last are performed with
 229          * zero-padded vectors. Last operation, BN_mod_mul_montgomery
 230          * below, returns user-visible value with removed zero padding.
 231          */
 232         if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
 233             || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
 234             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 235             goto err;
 236         }
 237         if (!bn_mod_add_fixed_top(s, s, m, order)) {
 238             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 239             goto err;
 240         }
 241         /*
 242          * |s| can still be larger than modulus, because |m| can be. In
 243          * such case we count on Montgomery reduction to tie it up.
 244          */
 245         if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
 246             || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
 247             ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
 248             goto err;
 249         }
 250
 251         if (BN_is_zero(s)) {
 252             /*
 253              * if kinv and r have been supplied by the caller, don't
 254              * generate new kinv and r values
 255              */
 256             if (in_kinv != NULL && in_r != NULL) {
 257                 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
 258                 goto err;
 259             }
 260         } else {
 261             /* s != 0 => we have a valid signature */
 262             break;
 263         }
 264     } while (1);
 265
 266     ok = 1;
 267  err:
 268     if (!ok) {
 269         ECDSA_SIG_free(ret);
 270         ret = NULL;
 271     }
 272     BN_CTX_free(ctx);
 273     BN_clear_free(m);
 274     BN_clear_free(kinv);
 275     return ret;
 276 }
 277
 278 /*-
 279  * returns
 280  *      1: correct signature
 281  *      0: incorrect signature
 282  *     -1: error
 283  */
 284 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
 285                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
 286 {
 287     ECDSA_SIG *s;
 288     const unsigned char *p = sigbuf;
 289     unsigned char *der = NULL;
 290     int derlen = -1;
 291     int ret = -1;
 292
 293     s = ECDSA_SIG_new();
 294     if (s == NULL)
 295         return ret;
 296     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
 297         goto err;
 298     /* Ensure signature uses DER and doesn't have trailing garbage */
 299     derlen = i2d_ECDSA_SIG(s, &der);
 300     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
 301         goto err;
 302     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
 303  err:
 304     OPENSSL_clear_free(der, derlen);
 305     ECDSA_SIG_free(s);
 306     return ret;
 307 }
 308
 309 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
 310                           const ECDSA_SIG *sig, EC_KEY *eckey)
 311 {
 312     int ret = -1, i;
 313     BN_CTX *ctx;
 314     const BIGNUM *order;
 315     BIGNUM *u1, *u2, *m, *X;
 316     EC_POINT *point = NULL;
 317     const EC_GROUP *group;
 318     const EC_POINT *pub_key;
 319
 320     /* check input values */
 321     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
 322         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
 323         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
 324         return -1;
 325     }
 326
 327     if (!EC_KEY_can_sign(eckey)) {
 328         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
 329         return -1;
 330     }
 331
 332     ctx = BN_CTX_new();
 333     if (ctx == NULL) {
 334         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
 335         return -1;
 336     }
 337     BN_CTX_start(ctx);
 338     u1 = BN_CTX_get(ctx);
 339     u2 = BN_CTX_get(ctx);
 340     m = BN_CTX_get(ctx);
 341     X = BN_CTX_get(ctx);
 342     if (X == NULL) {
 343         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 344         goto err;
 345     }
 346
 347     order = EC_GROUP_get0_order(group);
 348     if (order == NULL) {
 349         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, 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         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
 357         ret = 0;                /* signature is invalid */
 358         goto err;
 359     }
 360     /* calculate tmp1 = inv(S) mod order */
 361     if (!ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {
 362         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 363         goto err;
 364     }
 365     /* digest -> m */
 366     i = BN_num_bits(order);
 367     /*
 368      * Need to truncate digest if it is too long: first truncate whole bytes.
 369      */
 370     if (8 * dgst_len > i)
 371         dgst_len = (i + 7) / 8;
 372     if (!BN_bin2bn(dgst, dgst_len, m)) {
 373         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, 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         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, 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         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, 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         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 389         goto err;
 390     }
 391
 392     if ((point = EC_POINT_new(group)) == NULL) {
 393         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
 394         goto err;
 395     }
 396     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
 397         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 398         goto err;
 399     }
 400
 401     if (!EC_POINT_get_affine_coordinates(group, point, X, NULL, ctx)) {
 402         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
 403         goto err;
 404     }
 405
 406     if (!BN_nnmod(u1, X, order, ctx)) {
 407         ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
 408         goto err;
 409     }
 410     /*  if the signature is correct u1 is equal to sig->r */
 411     ret = (BN_ucmp(u1, sig->r) == 0);
 412  err:
 413     BN_CTX_end(ctx);
 414     BN_CTX_free(ctx);
 415     EC_POINT_free(point);
 416     return ret;
 417 }