crypto/rsa/rsa_ossl.c

   1 /*
   2  * Copyright 1995-2018 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 #include "internal/cryptlib.h"
  11 #include "internal/bn_int.h"
  12 #include "rsa_locl.h"
  13 #include "internal/constant_time_locl.h"
  14
  15 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
  16                                   unsigned char *to, RSA *rsa, int padding);
  17 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
  18                                    unsigned char *to, RSA *rsa, int padding);
  19 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
  20                                   unsigned char *to, RSA *rsa, int padding);
  21 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
  22                                    unsigned char *to, RSA *rsa, int padding);
  23 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
  24                            BN_CTX *ctx);
  25 static int rsa_ossl_init(RSA *rsa);
  26 static int rsa_ossl_finish(RSA *rsa);
  27 static RSA_METHOD rsa_pkcs1_ossl_meth = {
  28     "OpenSSL PKCS#1 RSA",
  29     rsa_ossl_public_encrypt,
  30     rsa_ossl_public_decrypt,     /* signature verification */
  31     rsa_ossl_private_encrypt,    /* signing */
  32     rsa_ossl_private_decrypt,
  33     rsa_ossl_mod_exp,
  34     BN_mod_exp_mont,            /* XXX probably we should not use Montgomery
  35                                  * if e == 3 */
  36     rsa_ossl_init,
  37     rsa_ossl_finish,
  38     RSA_FLAG_FIPS_METHOD,       /* flags */
  39     NULL,
  40     0,                          /* rsa_sign */
  41     0,                          /* rsa_verify */
  42     NULL,                       /* rsa_keygen */
  43     NULL                        /* rsa_multi_prime_keygen */
  44 };
  45
  46 static const RSA_METHOD *default_RSA_meth = &rsa_pkcs1_ossl_meth;
  47
  48 void RSA_set_default_method(const RSA_METHOD *meth)
  49 {
  50     default_RSA_meth = meth;
  51 }
  52
  53 const RSA_METHOD *RSA_get_default_method(void)
  54 {
  55     return default_RSA_meth;
  56 }
  57
  58 const RSA_METHOD *RSA_PKCS1_OpenSSL(void)
  59 {
  60     return &rsa_pkcs1_ossl_meth;
  61 }
  62
  63 const RSA_METHOD *RSA_null_method(void)
  64 {
  65     return NULL;
  66 }
  67
  68 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
  69                                   unsigned char *to, RSA *rsa, int padding)
  70 {
  71     BIGNUM *f, *ret;
  72     int i, num = 0, r = -1;
  73     unsigned char *buf = NULL;
  74     BN_CTX *ctx = NULL;
  75
  76     if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
  77         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_MODULUS_TOO_LARGE);
  78         return -1;
  79     }
  80
  81     if (BN_ucmp(rsa->n, rsa->e) <= 0) {
  82         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
  83         return -1;
  84     }
  85
  86     /* for large moduli, enforce exponent limit */
  87     if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
  88         if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
  89             RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
  90             return -1;
  91         }
  92     }
  93
  94     if ((ctx = BN_CTX_new()) == NULL)
  95         goto err;
  96     BN_CTX_start(ctx);
  97     f = BN_CTX_get(ctx);
  98     ret = BN_CTX_get(ctx);
  99     num = BN_num_bytes(rsa->n);
 100     buf = OPENSSL_malloc(num);
 101     if (ret == NULL || buf == NULL) {
 102         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, ERR_R_MALLOC_FAILURE);
 103         goto err;
 104     }
 105
 106     switch (padding) {
 107     case RSA_PKCS1_PADDING:
 108         i = RSA_padding_add_PKCS1_type_2(buf, num, from, flen);
 109         break;
 110     case RSA_PKCS1_OAEP_PADDING:
 111         i = RSA_padding_add_PKCS1_OAEP(buf, num, from, flen, NULL, 0);
 112         break;
 113     case RSA_SSLV23_PADDING:
 114         i = RSA_padding_add_SSLv23(buf, num, from, flen);
 115         break;
 116     case RSA_NO_PADDING:
 117         i = RSA_padding_add_none(buf, num, from, flen);
 118         break;
 119     default:
 120         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 121         goto err;
 122     }
 123     if (i <= 0)
 124         goto err;
 125
 126     if (BN_bin2bn(buf, num, f) == NULL)
 127         goto err;
 128
 129     if (BN_ucmp(f, rsa->n) >= 0) {
 130         /* usually the padding functions would catch this */
 131         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT,
 132                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 133         goto err;
 134     }
 135
 136     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 137         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 138                                     rsa->n, ctx))
 139             goto err;
 140
 141     if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
 142                                rsa->_method_mod_n))
 143         goto err;
 144
 145     /*
 146      * BN_bn2binpad puts in leading 0 bytes if the number is less than
 147      * the length of the modulus.
 148      */
 149     r = BN_bn2binpad(ret, to, num);
 150  err:
 151     if (ctx != NULL)
 152         BN_CTX_end(ctx);
 153     BN_CTX_free(ctx);
 154     OPENSSL_clear_free(buf, num);
 155     return r;
 156 }
 157
 158 static BN_BLINDING *rsa_get_blinding(RSA *rsa, int *local, BN_CTX *ctx)
 159 {
 160     BN_BLINDING *ret;
 161
 162     CRYPTO_THREAD_write_lock(rsa->lock);
 163
 164     if (rsa->blinding == NULL) {
 165         rsa->blinding = RSA_setup_blinding(rsa, ctx);
 166     }
 167
 168     ret = rsa->blinding;
 169     if (ret == NULL)
 170         goto err;
 171
 172     if (BN_BLINDING_is_current_thread(ret)) {
 173         /* rsa->blinding is ours! */
 174
 175         *local = 1;
 176     } else {
 177         /* resort to rsa->mt_blinding instead */
 178
 179         /*
 180          * instructs rsa_blinding_convert(), rsa_blinding_invert() that the
 181          * BN_BLINDING is shared, meaning that accesses require locks, and
 182          * that the blinding factor must be stored outside the BN_BLINDING
 183          */
 184         *local = 0;
 185
 186         if (rsa->mt_blinding == NULL) {
 187             rsa->mt_blinding = RSA_setup_blinding(rsa, ctx);
 188         }
 189         ret = rsa->mt_blinding;
 190     }
 191
 192  err:
 193     CRYPTO_THREAD_unlock(rsa->lock);
 194     return ret;
 195 }
 196
 197 static int rsa_blinding_convert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
 198                                 BN_CTX *ctx)
 199 {
 200     if (unblind == NULL) {
 201         /*
 202          * Local blinding: store the unblinding factor in BN_BLINDING.
 203          */
 204         return BN_BLINDING_convert_ex(f, NULL, b, ctx);
 205     } else {
 206         /*
 207          * Shared blinding: store the unblinding factor outside BN_BLINDING.
 208          */
 209         int ret;
 210
 211         BN_BLINDING_lock(b);
 212         ret = BN_BLINDING_convert_ex(f, unblind, b, ctx);
 213         BN_BLINDING_unlock(b);
 214
 215         return ret;
 216     }
 217 }
 218
 219 static int rsa_blinding_invert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
 220                                BN_CTX *ctx)
 221 {
 222     /*
 223      * For local blinding, unblind is set to NULL, and BN_BLINDING_invert_ex
 224      * will use the unblinding factor stored in BN_BLINDING. If BN_BLINDING
 225      * is shared between threads, unblind must be non-null:
 226      * BN_BLINDING_invert_ex will then use the local unblinding factor, and
 227      * will only read the modulus from BN_BLINDING. In both cases it's safe
 228      * to access the blinding without a lock.
 229      */
 230     return BN_BLINDING_invert_ex(f, unblind, b, ctx);
 231 }
 232
 233 /* signing */
 234 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
 235                                    unsigned char *to, RSA *rsa, int padding)
 236 {
 237     BIGNUM *f, *ret, *res;
 238     int i, num = 0, r = -1;
 239     unsigned char *buf = NULL;
 240     BN_CTX *ctx = NULL;
 241     int local_blinding = 0;
 242     /*
 243      * Used only if the blinding structure is shared. A non-NULL unblind
 244      * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
 245      * the unblinding factor outside the blinding structure.
 246      */
 247     BIGNUM *unblind = NULL;
 248     BN_BLINDING *blinding = NULL;
 249
 250     if ((ctx = BN_CTX_new()) == NULL)
 251         goto err;
 252     BN_CTX_start(ctx);
 253     f = BN_CTX_get(ctx);
 254     ret = BN_CTX_get(ctx);
 255     num = BN_num_bytes(rsa->n);
 256     buf = OPENSSL_malloc(num);
 257     if (ret == NULL || buf == NULL) {
 258         RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 259         goto err;
 260     }
 261
 262     switch (padding) {
 263     case RSA_PKCS1_PADDING:
 264         i = RSA_padding_add_PKCS1_type_1(buf, num, from, flen);
 265         break;
 266     case RSA_X931_PADDING:
 267         i = RSA_padding_add_X931(buf, num, from, flen);
 268         break;
 269     case RSA_NO_PADDING:
 270         i = RSA_padding_add_none(buf, num, from, flen);
 271         break;
 272     case RSA_SSLV23_PADDING:
 273     default:
 274         RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 275         goto err;
 276     }
 277     if (i <= 0)
 278         goto err;
 279
 280     if (BN_bin2bn(buf, num, f) == NULL)
 281         goto err;
 282
 283     if (BN_ucmp(f, rsa->n) >= 0) {
 284         /* usually the padding functions would catch this */
 285         RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT,
 286                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 287         goto err;
 288     }
 289
 290     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 291         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 292                                     rsa->n, ctx))
 293             goto err;
 294
 295     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 296         blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
 297         if (blinding == NULL) {
 298             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_INTERNAL_ERROR);
 299             goto err;
 300         }
 301     }
 302
 303     if (blinding != NULL) {
 304         if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
 305             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 306             goto err;
 307         }
 308         if (!rsa_blinding_convert(blinding, f, unblind, ctx))
 309             goto err;
 310     }
 311
 312     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 313         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 314         ((rsa->p != NULL) &&
 315          (rsa->q != NULL) &&
 316          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 317         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 318             goto err;
 319     } else {
 320         BIGNUM *d = BN_new();
 321         if (d == NULL) {
 322             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 323             goto err;
 324         }
 325         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 326
 327         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 328                                    rsa->_method_mod_n)) {
 329             BN_free(d);
 330             goto err;
 331         }
 332         /* We MUST free d before any further use of rsa->d */
 333         BN_free(d);
 334     }
 335
 336     if (blinding)
 337         if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
 338             goto err;
 339
 340     if (padding == RSA_X931_PADDING) {
 341         if (!BN_sub(f, rsa->n, ret))
 342             goto err;
 343         if (BN_cmp(ret, f) > 0)
 344             res = f;
 345         else
 346             res = ret;
 347     } else {
 348         res = ret;
 349     }
 350
 351     /*
 352      * BN_bn2binpad puts in leading 0 bytes if the number is less than
 353      * the length of the modulus.
 354      */
 355     r = BN_bn2binpad(res, to, num);
 356  err:
 357     if (ctx != NULL)
 358         BN_CTX_end(ctx);
 359     BN_CTX_free(ctx);
 360     OPENSSL_clear_free(buf, num);
 361     return r;
 362 }
 363
 364 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
 365                                    unsigned char *to, RSA *rsa, int padding)
 366 {
 367     BIGNUM *f, *ret;
 368     int j, num = 0, r = -1;
 369     unsigned char *buf = NULL;
 370     BN_CTX *ctx = NULL;
 371     int local_blinding = 0;
 372     /*
 373      * Used only if the blinding structure is shared. A non-NULL unblind
 374      * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
 375      * the unblinding factor outside the blinding structure.
 376      */
 377     BIGNUM *unblind = NULL;
 378     BN_BLINDING *blinding = NULL;
 379
 380     if ((ctx = BN_CTX_new()) == NULL)
 381         goto err;
 382     BN_CTX_start(ctx);
 383     f = BN_CTX_get(ctx);
 384     ret = BN_CTX_get(ctx);
 385     num = BN_num_bytes(rsa->n);
 386     buf = OPENSSL_malloc(num);
 387     if (ret == NULL || buf == NULL) {
 388         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 389         goto err;
 390     }
 391
 392     /*
 393      * This check was for equality but PGP does evil things and chops off the
 394      * top '0' bytes
 395      */
 396     if (flen > num) {
 397         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
 398                RSA_R_DATA_GREATER_THAN_MOD_LEN);
 399         goto err;
 400     }
 401
 402     /* make data into a big number */
 403     if (BN_bin2bn(from, (int)flen, f) == NULL)
 404         goto err;
 405
 406     if (BN_ucmp(f, rsa->n) >= 0) {
 407         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
 408                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 409         goto err;
 410     }
 411
 412     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 413         blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
 414         if (blinding == NULL) {
 415             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_INTERNAL_ERROR);
 416             goto err;
 417         }
 418     }
 419
 420     if (blinding != NULL) {
 421         if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
 422             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 423             goto err;
 424         }
 425         if (!rsa_blinding_convert(blinding, f, unblind, ctx))
 426             goto err;
 427     }
 428
 429     /* do the decrypt */
 430     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 431         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 432         ((rsa->p != NULL) &&
 433          (rsa->q != NULL) &&
 434          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 435         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 436             goto err;
 437     } else {
 438         BIGNUM *d = BN_new();
 439         if (d == NULL) {
 440             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 441             goto err;
 442         }
 443         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 444
 445         if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 446             if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 447                                         rsa->n, ctx)) {
 448                 BN_free(d);
 449                 goto err;
 450             }
 451         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 452                                    rsa->_method_mod_n)) {
 453             BN_free(d);
 454             goto err;
 455         }
 456         /* We MUST free d before any further use of rsa->d */
 457         BN_free(d);
 458     }
 459
 460     if (blinding)
 461         if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
 462             goto err;
 463
 464     j = BN_bn2binpad(ret, buf, num);
 465
 466     switch (padding) {
 467     case RSA_PKCS1_PADDING:
 468         r = RSA_padding_check_PKCS1_type_2(to, num, buf, j, num);
 469         break;
 470     case RSA_PKCS1_OAEP_PADDING:
 471         r = RSA_padding_check_PKCS1_OAEP(to, num, buf, j, num, NULL, 0);
 472         break;
 473     case RSA_SSLV23_PADDING:
 474         r = RSA_padding_check_SSLv23(to, num, buf, j, num);
 475         break;
 476     case RSA_NO_PADDING:
 477         memcpy(to, buf, (r = j));
 478         break;
 479     default:
 480         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 481         goto err;
 482     }
 483     RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
 484     err_clear_last_constant_time(r >= 0);
 485
 486  err:
 487     if (ctx != NULL)
 488         BN_CTX_end(ctx);
 489     BN_CTX_free(ctx);
 490     OPENSSL_clear_free(buf, num);
 491     return r;
 492 }
 493
 494 /* signature verification */
 495 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
 496                                   unsigned char *to, RSA *rsa, int padding)
 497 {
 498     BIGNUM *f, *ret;
 499     int i, num = 0, r = -1;
 500     unsigned char *buf = NULL;
 501     BN_CTX *ctx = NULL;
 502
 503     if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
 504         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_MODULUS_TOO_LARGE);
 505         return -1;
 506     }
 507
 508     if (BN_ucmp(rsa->n, rsa->e) <= 0) {
 509         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
 510         return -1;
 511     }
 512
 513     /* for large moduli, enforce exponent limit */
 514     if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
 515         if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
 516             RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
 517             return -1;
 518         }
 519     }
 520
 521     if ((ctx = BN_CTX_new()) == NULL)
 522         goto err;
 523     BN_CTX_start(ctx);
 524     f = BN_CTX_get(ctx);
 525     ret = BN_CTX_get(ctx);
 526     num = BN_num_bytes(rsa->n);
 527     buf = OPENSSL_malloc(num);
 528     if (ret == NULL || buf == NULL) {
 529         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, ERR_R_MALLOC_FAILURE);
 530         goto err;
 531     }
 532
 533     /*
 534      * This check was for equality but PGP does evil things and chops off the
 535      * top '0' bytes
 536      */
 537     if (flen > num) {
 538         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_DATA_GREATER_THAN_MOD_LEN);
 539         goto err;
 540     }
 541
 542     if (BN_bin2bn(from, flen, f) == NULL)
 543         goto err;
 544
 545     if (BN_ucmp(f, rsa->n) >= 0) {
 546         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT,
 547                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 548         goto err;
 549     }
 550
 551     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 552         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 553                                     rsa->n, ctx))
 554             goto err;
 555
 556     if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
 557                                rsa->_method_mod_n))
 558         goto err;
 559
 560     if ((padding == RSA_X931_PADDING) && ((bn_get_words(ret)[0] & 0xf) != 12))
 561         if (!BN_sub(ret, rsa->n, ret))
 562             goto err;
 563
 564     i = BN_bn2binpad(ret, buf, num);
 565
 566     switch (padding) {
 567     case RSA_PKCS1_PADDING:
 568         r = RSA_padding_check_PKCS1_type_1(to, num, buf, i, num);
 569         break;
 570     case RSA_X931_PADDING:
 571         r = RSA_padding_check_X931(to, num, buf, i, num);
 572         break;
 573     case RSA_NO_PADDING:
 574         memcpy(to, buf, (r = i));
 575         break;
 576     default:
 577         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 578         goto err;
 579     }
 580     if (r < 0)
 581         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
 582
 583  err:
 584     if (ctx != NULL)
 585         BN_CTX_end(ctx);
 586     BN_CTX_free(ctx);
 587     OPENSSL_clear_free(buf, num);
 588     return r;
 589 }
 590
 591 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 592 {
 593     BIGNUM *r1, *m1, *vrfy, *r2, *m[RSA_MAX_PRIME_NUM - 2];
 594     int ret = 0, i, ex_primes = 0, smooth = 0;
 595     RSA_PRIME_INFO *pinfo;
 596
 597     BN_CTX_start(ctx);
 598
 599     r1 = BN_CTX_get(ctx);
 600     r2 = BN_CTX_get(ctx);
 601     m1 = BN_CTX_get(ctx);
 602     vrfy = BN_CTX_get(ctx);
 603     if (vrfy == NULL)
 604         goto err;
 605
 606     if (rsa->version == RSA_ASN1_VERSION_MULTI
 607         && ((ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0
 608              || ex_primes > RSA_MAX_PRIME_NUM - 2))
 609         goto err;
 610
 611     if (rsa->flags & RSA_FLAG_CACHE_PRIVATE) {
 612         BIGNUM *factor = BN_new();
 613
 614         if (factor == NULL)
 615             goto err;
 616
 617         /*
 618          * Make sure BN_mod_inverse in Montgomery initialization uses the
 619          * BN_FLG_CONSTTIME flag
 620          */
 621         if (!(BN_with_flags(factor, rsa->p, BN_FLG_CONSTTIME),
 622               BN_MONT_CTX_set_locked(&rsa->_method_mod_p, rsa->lock,
 623                                      factor, ctx))
 624             || !(BN_with_flags(factor, rsa->q, BN_FLG_CONSTTIME),
 625                  BN_MONT_CTX_set_locked(&rsa->_method_mod_q, rsa->lock,
 626                                         factor, ctx))) {
 627             BN_free(factor);
 628             goto err;
 629         }
 630         for (i = 0; i < ex_primes; i++) {
 631             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 632             BN_with_flags(factor, pinfo->r, BN_FLG_CONSTTIME);
 633             if (!BN_MONT_CTX_set_locked(&pinfo->m, rsa->lock, factor, ctx)) {
 634                 BN_free(factor);
 635                 goto err;
 636             }
 637         }
 638         /*
 639          * We MUST free |factor| before any further use of the prime factors
 640          */
 641         BN_free(factor);
 642
 643         smooth = (ex_primes == 0)
 644                  && (rsa->meth->bn_mod_exp == BN_mod_exp_mont)
 645                  && (BN_num_bits(rsa->q) == BN_num_bits(rsa->p));
 646     }
 647
 648     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 649         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 650                                     rsa->n, ctx))
 651             goto err;
 652
 653     if (smooth) {
 654         /*
 655          * Conversion from Montgomery domain, a.k.a. Montgomery reduction,
 656          * accepts values in [0-m*2^w) range. w is m's bit width rounded up
 657          * to limb width. So that at the very least if |I| is fully reduced,
 658          * i.e. less than p*q, we can count on from-to round to perform
 659          * below modulo operations on |I|. Unlike BN_mod it's constant time.
 660          */
 661         if (/* m1 = I moq q */
 662             !bn_from_mont_fixed_top(m1, I, rsa->_method_mod_q, ctx)
 663             || !bn_to_mont_fixed_top(m1, m1, rsa->_method_mod_q, ctx)
 664             /* m1 = m1^dmq1 mod q */
 665             || !BN_mod_exp_mont_consttime(m1, m1, rsa->dmq1, rsa->q, ctx,
 666                                           rsa->_method_mod_q)
 667             /* r1 = I mod p */
 668             || !bn_from_mont_fixed_top(r1, I, rsa->_method_mod_p, ctx)
 669             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 670             /* r1 = r1^dmp1 mod p */
 671             || !BN_mod_exp_mont_consttime(r1, r1, rsa->dmp1, rsa->p, ctx,
 672                                           rsa->_method_mod_p)
 673             /* r1 = (r1 - m1) mod p */
 674             /*
 675              * bn_mod_sub_fixed_top is not regular modular subtraction,
 676              * it can tolerate subtrahend to be larger than modulus, but
 677              * not bit-wise wider. This makes up for uncommon q>p case,
 678              * when |m1| can be larger than |rsa->p|.
 679              */
 680             || !bn_mod_sub_fixed_top(r1, r1, m1, rsa->p)
 681
 682             /* r1 = r1 * iqmp mod p */
 683             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 684             || !bn_mul_mont_fixed_top(r1, r1, rsa->iqmp, rsa->_method_mod_p,
 685                                       ctx)
 686             /* r0 = r1 * q + m1 */
 687             || !bn_mul_fixed_top(r0, r1, rsa->q, ctx)
 688             || !bn_mod_add_fixed_top(r0, r0, m1, rsa->n))
 689             goto err;
 690
 691         goto tail;
 692     }
 693
 694     /* compute I mod q */
 695     {
 696         BIGNUM *c = BN_new();
 697         if (c == NULL)
 698             goto err;
 699         BN_with_flags(c, I, BN_FLG_CONSTTIME);
 700
 701         if (!BN_mod(r1, c, rsa->q, ctx)) {
 702             BN_free(c);
 703             goto err;
 704         }
 705
 706         {
 707             BIGNUM *dmq1 = BN_new();
 708             if (dmq1 == NULL) {
 709                 BN_free(c);
 710                 goto err;
 711             }
 712             BN_with_flags(dmq1, rsa->dmq1, BN_FLG_CONSTTIME);
 713
 714             /* compute r1^dmq1 mod q */
 715             if (!rsa->meth->bn_mod_exp(m1, r1, dmq1, rsa->q, ctx,
 716                                        rsa->_method_mod_q)) {
 717                 BN_free(c);
 718                 BN_free(dmq1);
 719                 goto err;
 720             }
 721             /* We MUST free dmq1 before any further use of rsa->dmq1 */
 722             BN_free(dmq1);
 723         }
 724
 725         /* compute I mod p */
 726         if (!BN_mod(r1, c, rsa->p, ctx)) {
 727             BN_free(c);
 728             goto err;
 729         }
 730         /* We MUST free c before any further use of I */
 731         BN_free(c);
 732     }
 733
 734     {
 735         BIGNUM *dmp1 = BN_new();
 736         if (dmp1 == NULL)
 737             goto err;
 738         BN_with_flags(dmp1, rsa->dmp1, BN_FLG_CONSTTIME);
 739
 740         /* compute r1^dmp1 mod p */
 741         if (!rsa->meth->bn_mod_exp(r0, r1, dmp1, rsa->p, ctx,
 742                                    rsa->_method_mod_p)) {
 743             BN_free(dmp1);
 744             goto err;
 745         }
 746         /* We MUST free dmp1 before any further use of rsa->dmp1 */
 747         BN_free(dmp1);
 748     }
 749
 750     /*
 751      * calculate m_i in multi-prime case
 752      *
 753      * TODO:
 754      * 1. squash the following two loops and calculate |m_i| there.
 755      * 2. remove cc and reuse |c|.
 756      * 3. remove |dmq1| and |dmp1| in previous block and use |di|.
 757      *
 758      * If these things are done, the code will be more readable.
 759      */
 760     if (ex_primes > 0) {
 761         BIGNUM *di = BN_new(), *cc = BN_new();
 762
 763         if (cc == NULL || di == NULL) {
 764             BN_free(cc);
 765             BN_free(di);
 766             goto err;
 767         }
 768
 769         for (i = 0; i < ex_primes; i++) {
 770             /* prepare m_i */
 771             if ((m[i] = BN_CTX_get(ctx)) == NULL) {
 772                 BN_free(cc);
 773                 BN_free(di);
 774                 goto err;
 775             }
 776
 777             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 778
 779             /* prepare c and d_i */
 780             BN_with_flags(cc, I, BN_FLG_CONSTTIME);
 781             BN_with_flags(di, pinfo->d, BN_FLG_CONSTTIME);
 782
 783             if (!BN_mod(r1, cc, pinfo->r, ctx)) {
 784                 BN_free(cc);
 785                 BN_free(di);
 786                 goto err;
 787             }
 788             /* compute r1 ^ d_i mod r_i */
 789             if (!rsa->meth->bn_mod_exp(m[i], r1, di, pinfo->r, ctx, pinfo->m)) {
 790                 BN_free(cc);
 791                 BN_free(di);
 792                 goto err;
 793             }
 794         }
 795
 796         BN_free(cc);
 797         BN_free(di);
 798     }
 799
 800     if (!BN_sub(r0, r0, m1))
 801         goto err;
 802     /*
 803      * This will help stop the size of r0 increasing, which does affect the
 804      * multiply if it optimised for a power of 2 size
 805      */
 806     if (BN_is_negative(r0))
 807         if (!BN_add(r0, r0, rsa->p))
 808             goto err;
 809
 810     if (!BN_mul(r1, r0, rsa->iqmp, ctx))
 811         goto err;
 812
 813     {
 814         BIGNUM *pr1 = BN_new();
 815         if (pr1 == NULL)
 816             goto err;
 817         BN_with_flags(pr1, r1, BN_FLG_CONSTTIME);
 818
 819         if (!BN_mod(r0, pr1, rsa->p, ctx)) {
 820             BN_free(pr1);
 821             goto err;
 822         }
 823         /* We MUST free pr1 before any further use of r1 */
 824         BN_free(pr1);
 825     }
 826
 827     /*
 828      * If p < q it is occasionally possible for the correction of adding 'p'
 829      * if r0 is negative above to leave the result still negative. This can
 830      * break the private key operations: the following second correction
 831      * should *always* correct this rare occurrence. This will *never* happen
 832      * with OpenSSL generated keys because they ensure p > q [steve]
 833      */
 834     if (BN_is_negative(r0))
 835         if (!BN_add(r0, r0, rsa->p))
 836             goto err;
 837     if (!BN_mul(r1, r0, rsa->q, ctx))
 838         goto err;
 839     if (!BN_add(r0, r1, m1))
 840         goto err;
 841
 842     /* add m_i to m in multi-prime case */
 843     if (ex_primes > 0) {
 844         BIGNUM *pr2 = BN_new();
 845
 846         if (pr2 == NULL)
 847             goto err;
 848
 849         for (i = 0; i < ex_primes; i++) {
 850             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 851             if (!BN_sub(r1, m[i], r0)) {
 852                 BN_free(pr2);
 853                 goto err;
 854             }
 855
 856             if (!BN_mul(r2, r1, pinfo->t, ctx)) {
 857                 BN_free(pr2);
 858                 goto err;
 859             }
 860
 861             BN_with_flags(pr2, r2, BN_FLG_CONSTTIME);
 862
 863             if (!BN_mod(r1, pr2, pinfo->r, ctx)) {
 864                 BN_free(pr2);
 865                 goto err;
 866             }
 867
 868             if (BN_is_negative(r1))
 869                 if (!BN_add(r1, r1, pinfo->r)) {
 870                     BN_free(pr2);
 871                     goto err;
 872                 }
 873             if (!BN_mul(r1, r1, pinfo->pp, ctx)) {
 874                 BN_free(pr2);
 875                 goto err;
 876             }
 877             if (!BN_add(r0, r0, r1)) {
 878                 BN_free(pr2);
 879                 goto err;
 880             }
 881         }
 882         BN_free(pr2);
 883     }
 884
 885  tail:
 886     if (rsa->e && rsa->n) {
 887         if (rsa->meth->bn_mod_exp == BN_mod_exp_mont) {
 888             if (!BN_mod_exp_mont(vrfy, r0, rsa->e, rsa->n, ctx,
 889                                  rsa->_method_mod_n))
 890                 goto err;
 891         } else {
 892             bn_correct_top(r0);
 893             if (!rsa->meth->bn_mod_exp(vrfy, r0, rsa->e, rsa->n, ctx,
 894                                        rsa->_method_mod_n))
 895                 goto err;
 896         }
 897         /*
 898          * If 'I' was greater than (or equal to) rsa->n, the operation will
 899          * be equivalent to using 'I mod n'. However, the result of the
 900          * verify will *always* be less than 'n' so we don't check for
 901          * absolute equality, just congruency.
 902          */
 903         if (!BN_sub(vrfy, vrfy, I))
 904             goto err;
 905         if (BN_is_zero(vrfy)) {
 906             bn_correct_top(r0);
 907             ret = 1;
 908             goto err;   /* not actually error */
 909         }
 910         if (!BN_mod(vrfy, vrfy, rsa->n, ctx))
 911             goto err;
 912         if (BN_is_negative(vrfy))
 913             if (!BN_add(vrfy, vrfy, rsa->n))
 914                 goto err;
 915         if (!BN_is_zero(vrfy)) {
 916             /*
 917              * 'I' and 'vrfy' aren't congruent mod n. Don't leak
 918              * miscalculated CRT output, just do a raw (slower) mod_exp and
 919              * return that instead.
 920              */
 921
 922             BIGNUM *d = BN_new();
 923             if (d == NULL)
 924                 goto err;
 925             BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 926
 927             if (!rsa->meth->bn_mod_exp(r0, I, d, rsa->n, ctx,
 928                                        rsa->_method_mod_n)) {
 929                 BN_free(d);
 930                 goto err;
 931             }
 932             /* We MUST free d before any further use of rsa->d */
 933             BN_free(d);
 934         }
 935     }
 936     /*
 937      * It's unfortunate that we have to bn_correct_top(r0). What hopefully
 938      * saves the day is that correction is highly unlike, and private key
 939      * operations are customarily performed on blinded message. Which means
 940      * that attacker won't observe correlation with chosen plaintext.
 941      * Secondly, remaining code would still handle it in same computational
 942      * time and even conceal memory access pattern around corrected top.
 943      */
 944     bn_correct_top(r0);
 945     ret = 1;
 946  err:
 947     BN_CTX_end(ctx);
 948     return ret;
 949 }
 950
 951 static int rsa_ossl_init(RSA *rsa)
 952 {
 953     rsa->flags |= RSA_FLAG_CACHE_PUBLIC | RSA_FLAG_CACHE_PRIVATE;
 954     return 1;
 955 }
 956
 957 static int rsa_ossl_finish(RSA *rsa)
 958 {
 959     int i;
 960     RSA_PRIME_INFO *pinfo;
 961
 962     BN_MONT_CTX_free(rsa->_method_mod_n);
 963     BN_MONT_CTX_free(rsa->_method_mod_p);
 964     BN_MONT_CTX_free(rsa->_method_mod_q);
 965     for (i = 0; i < sk_RSA_PRIME_INFO_num(rsa->prime_infos); i++) {
 966         pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 967         BN_MONT_CTX_free(pinfo->m);
 968     }
 969     return 1;
 970 }