crypto/rsa/rsa_ossl.c

   1 /*
   2  * Copyright 1995-2018 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 "internal/cryptlib.h"
  11 #include "internal/bn_int.h"
  12 #include "rsa_locl.h"
  13
  14 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
  15                                   unsigned char *to, RSA *rsa, int padding);
  16 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
  17                                    unsigned char *to, RSA *rsa, int padding);
  18 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
  19                                   unsigned char *to, RSA *rsa, int padding);
  20 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
  21                                    unsigned char *to, RSA *rsa, int padding);
  22 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
  23                            BN_CTX *ctx);
  24 static int rsa_ossl_init(RSA *rsa);
  25 static int rsa_ossl_finish(RSA *rsa);
  26 static RSA_METHOD rsa_pkcs1_ossl_meth = {
  27     "OpenSSL PKCS#1 RSA",
  28     rsa_ossl_public_encrypt,
  29     rsa_ossl_public_decrypt,     /* signature verification */
  30     rsa_ossl_private_encrypt,    /* signing */
  31     rsa_ossl_private_decrypt,
  32     rsa_ossl_mod_exp,
  33     BN_mod_exp_mont,            /* XXX probably we should not use Montgomery
  34                                  * if e == 3 */
  35     rsa_ossl_init,
  36     rsa_ossl_finish,
  37     RSA_FLAG_FIPS_METHOD,       /* flags */
  38     NULL,
  39     0,                          /* rsa_sign */
  40     0,                          /* rsa_verify */
  41     NULL,                       /* rsa_keygen */
  42     NULL                        /* rsa_multi_prime_keygen */
  43 };
  44
  45 static const RSA_METHOD *default_RSA_meth = &rsa_pkcs1_ossl_meth;
  46
  47 void RSA_set_default_method(const RSA_METHOD *meth)
  48 {
  49     default_RSA_meth = meth;
  50 }
  51
  52 const RSA_METHOD *RSA_get_default_method(void)
  53 {
  54     return default_RSA_meth;
  55 }
  56
  57 const RSA_METHOD *RSA_PKCS1_OpenSSL(void)
  58 {
  59     return &rsa_pkcs1_ossl_meth;
  60 }
  61
  62 const RSA_METHOD *RSA_null_method(void)
  63 {
  64     return NULL;
  65 }
  66
  67 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
  68                                   unsigned char *to, RSA *rsa, int padding)
  69 {
  70     BIGNUM *f, *ret;
  71     int i, num = 0, r = -1;
  72     unsigned char *buf = NULL;
  73     BN_CTX *ctx = NULL;
  74
  75     if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
  76         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_MODULUS_TOO_LARGE);
  77         return -1;
  78     }
  79
  80     if (BN_ucmp(rsa->n, rsa->e) <= 0) {
  81         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
  82         return -1;
  83     }
  84
  85     /* for large moduli, enforce exponent limit */
  86     if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
  87         if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
  88             RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
  89             return -1;
  90         }
  91     }
  92
  93     if ((ctx = BN_CTX_new()) == NULL)
  94         goto err;
  95     BN_CTX_start(ctx);
  96     f = BN_CTX_get(ctx);
  97     ret = BN_CTX_get(ctx);
  98     num = BN_num_bytes(rsa->n);
  99     buf = OPENSSL_malloc(num);
 100     if (ret == NULL || buf == NULL) {
 101         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, ERR_R_MALLOC_FAILURE);
 102         goto err;
 103     }
 104
 105     switch (padding) {
 106     case RSA_PKCS1_PADDING:
 107         i = RSA_padding_add_PKCS1_type_2(buf, num, from, flen);
 108         break;
 109     case RSA_PKCS1_OAEP_PADDING:
 110         i = RSA_padding_add_PKCS1_OAEP(buf, num, from, flen, NULL, 0);
 111         break;
 112     case RSA_SSLV23_PADDING:
 113         i = RSA_padding_add_SSLv23(buf, num, from, flen);
 114         break;
 115     case RSA_NO_PADDING:
 116         i = RSA_padding_add_none(buf, num, from, flen);
 117         break;
 118     default:
 119         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 120         goto err;
 121     }
 122     if (i <= 0)
 123         goto err;
 124
 125     if (BN_bin2bn(buf, num, f) == NULL)
 126         goto err;
 127
 128     if (BN_ucmp(f, rsa->n) >= 0) {
 129         /* usually the padding functions would catch this */
 130         RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT,
 131                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 132         goto err;
 133     }
 134
 135     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 136         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 137                                     rsa->n, ctx))
 138             goto err;
 139
 140     if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
 141                                rsa->_method_mod_n))
 142         goto err;
 143
 144     /*
 145      * BN_bn2binpad puts in leading 0 bytes if the number is less than
 146      * the length of the modulus.
 147      */
 148     r = BN_bn2binpad(ret, to, num);
 149  err:
 150     if (ctx != NULL)
 151         BN_CTX_end(ctx);
 152     BN_CTX_free(ctx);
 153     OPENSSL_clear_free(buf, num);
 154     return r;
 155 }
 156
 157 static BN_BLINDING *rsa_get_blinding(RSA *rsa, int *local, BN_CTX *ctx)
 158 {
 159     BN_BLINDING *ret;
 160
 161     CRYPTO_THREAD_write_lock(rsa->lock);
 162
 163     if (rsa->blinding == NULL) {
 164         rsa->blinding = RSA_setup_blinding(rsa, ctx);
 165     }
 166
 167     ret = rsa->blinding;
 168     if (ret == NULL)
 169         goto err;
 170
 171     if (BN_BLINDING_is_current_thread(ret)) {
 172         /* rsa->blinding is ours! */
 173
 174         *local = 1;
 175     } else {
 176         /* resort to rsa->mt_blinding instead */
 177
 178         /*
 179          * instructs rsa_blinding_convert(), rsa_blinding_invert() that the
 180          * BN_BLINDING is shared, meaning that accesses require locks, and
 181          * that the blinding factor must be stored outside the BN_BLINDING
 182          */
 183         *local = 0;
 184
 185         if (rsa->mt_blinding == NULL) {
 186             rsa->mt_blinding = RSA_setup_blinding(rsa, ctx);
 187         }
 188         ret = rsa->mt_blinding;
 189     }
 190
 191  err:
 192     CRYPTO_THREAD_unlock(rsa->lock);
 193     return ret;
 194 }
 195
 196 static int rsa_blinding_convert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
 197                                 BN_CTX *ctx)
 198 {
 199     if (unblind == NULL) {
 200         /*
 201          * Local blinding: store the unblinding factor in BN_BLINDING.
 202          */
 203         return BN_BLINDING_convert_ex(f, NULL, b, ctx);
 204     } else {
 205         /*
 206          * Shared blinding: store the unblinding factor outside BN_BLINDING.
 207          */
 208         int ret;
 209
 210         BN_BLINDING_lock(b);
 211         ret = BN_BLINDING_convert_ex(f, unblind, b, ctx);
 212         BN_BLINDING_unlock(b);
 213
 214         return ret;
 215     }
 216 }
 217
 218 static int rsa_blinding_invert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
 219                                BN_CTX *ctx)
 220 {
 221     /*
 222      * For local blinding, unblind is set to NULL, and BN_BLINDING_invert_ex
 223      * will use the unblinding factor stored in BN_BLINDING. If BN_BLINDING
 224      * is shared between threads, unblind must be non-null:
 225      * BN_BLINDING_invert_ex will then use the local unblinding factor, and
 226      * will only read the modulus from BN_BLINDING. In both cases it's safe
 227      * to access the blinding without a lock.
 228      */
 229     return BN_BLINDING_invert_ex(f, unblind, b, ctx);
 230 }
 231
 232 /* signing */
 233 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
 234                                    unsigned char *to, RSA *rsa, int padding)
 235 {
 236     BIGNUM *f, *ret, *res;
 237     int i, num = 0, r = -1;
 238     unsigned char *buf = NULL;
 239     BN_CTX *ctx = NULL;
 240     int local_blinding = 0;
 241     /*
 242      * Used only if the blinding structure is shared. A non-NULL unblind
 243      * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
 244      * the unblinding factor outside the blinding structure.
 245      */
 246     BIGNUM *unblind = NULL;
 247     BN_BLINDING *blinding = NULL;
 248
 249     if ((ctx = BN_CTX_new()) == NULL)
 250         goto err;
 251     BN_CTX_start(ctx);
 252     f = BN_CTX_get(ctx);
 253     ret = BN_CTX_get(ctx);
 254     num = BN_num_bytes(rsa->n);
 255     buf = OPENSSL_malloc(num);
 256     if (ret == NULL || buf == NULL) {
 257         RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 258         goto err;
 259     }
 260
 261     switch (padding) {
 262     case RSA_PKCS1_PADDING:
 263         i = RSA_padding_add_PKCS1_type_1(buf, num, from, flen);
 264         break;
 265     case RSA_X931_PADDING:
 266         i = RSA_padding_add_X931(buf, num, from, flen);
 267         break;
 268     case RSA_NO_PADDING:
 269         i = RSA_padding_add_none(buf, num, from, flen);
 270         break;
 271     case RSA_SSLV23_PADDING:
 272     default:
 273         RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 274         goto err;
 275     }
 276     if (i <= 0)
 277         goto err;
 278
 279     if (BN_bin2bn(buf, num, f) == NULL)
 280         goto err;
 281
 282     if (BN_ucmp(f, rsa->n) >= 0) {
 283         /* usually the padding functions would catch this */
 284         RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT,
 285                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 286         goto err;
 287     }
 288
 289     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 290         blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
 291         if (blinding == NULL) {
 292             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_INTERNAL_ERROR);
 293             goto err;
 294         }
 295     }
 296
 297     if (blinding != NULL) {
 298         if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
 299             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 300             goto err;
 301         }
 302         if (!rsa_blinding_convert(blinding, f, unblind, ctx))
 303             goto err;
 304     }
 305
 306     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 307         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 308         ((rsa->p != NULL) &&
 309          (rsa->q != NULL) &&
 310          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 311         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 312             goto err;
 313     } else {
 314         BIGNUM *d = BN_new();
 315         if (d == NULL) {
 316             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 317             goto err;
 318         }
 319         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 320
 321         if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 322             if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 323                                         rsa->n, ctx)) {
 324                 BN_free(d);
 325                 goto err;
 326             }
 327
 328         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 329                                    rsa->_method_mod_n)) {
 330             BN_free(d);
 331             goto err;
 332         }
 333         /* We MUST free d before any further use of rsa->d */
 334         BN_free(d);
 335     }
 336
 337     if (blinding)
 338         if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
 339             goto err;
 340
 341     if (padding == RSA_X931_PADDING) {
 342         if (!BN_sub(f, rsa->n, ret))
 343             goto err;
 344         if (BN_cmp(ret, f) > 0)
 345             res = f;
 346         else
 347             res = ret;
 348     } else {
 349         res = ret;
 350     }
 351
 352     /*
 353      * BN_bn2binpad puts in leading 0 bytes if the number is less than
 354      * the length of the modulus.
 355      */
 356     r = BN_bn2binpad(res, to, num);
 357  err:
 358     if (ctx != NULL)
 359         BN_CTX_end(ctx);
 360     BN_CTX_free(ctx);
 361     OPENSSL_clear_free(buf, num);
 362     return r;
 363 }
 364
 365 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
 366                                    unsigned char *to, RSA *rsa, int padding)
 367 {
 368     BIGNUM *f, *ret;
 369     int j, num = 0, r = -1;
 370     unsigned char *buf = NULL;
 371     BN_CTX *ctx = NULL;
 372     int local_blinding = 0;
 373     /*
 374      * Used only if the blinding structure is shared. A non-NULL unblind
 375      * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
 376      * the unblinding factor outside the blinding structure.
 377      */
 378     BIGNUM *unblind = NULL;
 379     BN_BLINDING *blinding = NULL;
 380
 381     if ((ctx = BN_CTX_new()) == NULL)
 382         goto err;
 383     BN_CTX_start(ctx);
 384     f = BN_CTX_get(ctx);
 385     ret = BN_CTX_get(ctx);
 386     num = BN_num_bytes(rsa->n);
 387     buf = OPENSSL_malloc(num);
 388     if (ret == NULL || buf == NULL) {
 389         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 390         goto err;
 391     }
 392
 393     /*
 394      * This check was for equality but PGP does evil things and chops off the
 395      * top '0' bytes
 396      */
 397     if (flen > num) {
 398         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
 399                RSA_R_DATA_GREATER_THAN_MOD_LEN);
 400         goto err;
 401     }
 402
 403     /* make data into a big number */
 404     if (BN_bin2bn(from, (int)flen, f) == NULL)
 405         goto err;
 406
 407     if (BN_ucmp(f, rsa->n) >= 0) {
 408         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
 409                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 410         goto err;
 411     }
 412
 413     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 414         blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
 415         if (blinding == NULL) {
 416             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_INTERNAL_ERROR);
 417             goto err;
 418         }
 419     }
 420
 421     if (blinding != NULL) {
 422         if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
 423             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 424             goto err;
 425         }
 426         if (!rsa_blinding_convert(blinding, f, unblind, ctx))
 427             goto err;
 428     }
 429
 430     /* do the decrypt */
 431     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 432         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 433         ((rsa->p != NULL) &&
 434          (rsa->q != NULL) &&
 435          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 436         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 437             goto err;
 438     } else {
 439         BIGNUM *d = BN_new();
 440         if (d == NULL) {
 441             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 442             goto err;
 443         }
 444         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 445
 446         if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 447             if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 448                                         rsa->n, ctx)) {
 449                 BN_free(d);
 450                 goto err;
 451             }
 452         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 453                                    rsa->_method_mod_n)) {
 454             BN_free(d);
 455             goto err;
 456         }
 457         /* We MUST free d before any further use of rsa->d */
 458         BN_free(d);
 459     }
 460
 461     if (blinding)
 462         if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
 463             goto err;
 464
 465     j = BN_bn2binpad(ret, buf, num);
 466
 467     switch (padding) {
 468     case RSA_PKCS1_PADDING:
 469         r = RSA_padding_check_PKCS1_type_2(to, num, buf, j, num);
 470         break;
 471     case RSA_PKCS1_OAEP_PADDING:
 472         r = RSA_padding_check_PKCS1_OAEP(to, num, buf, j, num, NULL, 0);
 473         break;
 474     case RSA_SSLV23_PADDING:
 475         r = RSA_padding_check_SSLv23(to, num, buf, j, num);
 476         break;
 477     case RSA_NO_PADDING:
 478         memcpy(to, buf, (r = j));
 479         break;
 480     default:
 481         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 482         goto err;
 483     }
 484     if (r < 0)
 485         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
 486
 487  err:
 488     if (ctx != NULL)
 489         BN_CTX_end(ctx);
 490     BN_CTX_free(ctx);
 491     OPENSSL_clear_free(buf, num);
 492     return r;
 493 }
 494
 495 /* signature verification */
 496 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
 497                                   unsigned char *to, RSA *rsa, int padding)
 498 {
 499     BIGNUM *f, *ret;
 500     int i, num = 0, r = -1;
 501     unsigned char *buf = NULL;
 502     BN_CTX *ctx = NULL;
 503
 504     if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
 505         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_MODULUS_TOO_LARGE);
 506         return -1;
 507     }
 508
 509     if (BN_ucmp(rsa->n, rsa->e) <= 0) {
 510         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
 511         return -1;
 512     }
 513
 514     /* for large moduli, enforce exponent limit */
 515     if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
 516         if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
 517             RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
 518             return -1;
 519         }
 520     }
 521
 522     if ((ctx = BN_CTX_new()) == NULL)
 523         goto err;
 524     BN_CTX_start(ctx);
 525     f = BN_CTX_get(ctx);
 526     ret = BN_CTX_get(ctx);
 527     num = BN_num_bytes(rsa->n);
 528     buf = OPENSSL_malloc(num);
 529     if (ret == NULL || buf == NULL) {
 530         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, ERR_R_MALLOC_FAILURE);
 531         goto err;
 532     }
 533
 534     /*
 535      * This check was for equality but PGP does evil things and chops off the
 536      * top '0' bytes
 537      */
 538     if (flen > num) {
 539         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_DATA_GREATER_THAN_MOD_LEN);
 540         goto err;
 541     }
 542
 543     if (BN_bin2bn(from, flen, f) == NULL)
 544         goto err;
 545
 546     if (BN_ucmp(f, rsa->n) >= 0) {
 547         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT,
 548                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 549         goto err;
 550     }
 551
 552     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 553         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 554                                     rsa->n, ctx))
 555             goto err;
 556
 557     if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
 558                                rsa->_method_mod_n))
 559         goto err;
 560
 561     if ((padding == RSA_X931_PADDING) && ((bn_get_words(ret)[0] & 0xf) != 12))
 562         if (!BN_sub(ret, rsa->n, ret))
 563             goto err;
 564
 565     i = BN_bn2binpad(ret, buf, num);
 566
 567     switch (padding) {
 568     case RSA_PKCS1_PADDING:
 569         r = RSA_padding_check_PKCS1_type_1(to, num, buf, i, num);
 570         break;
 571     case RSA_X931_PADDING:
 572         r = RSA_padding_check_X931(to, num, buf, i, num);
 573         break;
 574     case RSA_NO_PADDING:
 575         memcpy(to, buf, (r = i));
 576         break;
 577     default:
 578         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 579         goto err;
 580     }
 581     if (r < 0)
 582         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
 583
 584  err:
 585     if (ctx != NULL)
 586         BN_CTX_end(ctx);
 587     BN_CTX_free(ctx);
 588     OPENSSL_clear_free(buf, num);
 589     return r;
 590 }
 591
 592 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 593 {
 594     BIGNUM *r1, *m1, *vrfy, *r2, *m[RSA_MAX_PRIME_NUM - 2];
 595     int ret = 0, i, ex_primes = 0, smooth = 0;
 596     RSA_PRIME_INFO *pinfo;
 597
 598     BN_CTX_start(ctx);
 599
 600     r1 = BN_CTX_get(ctx);
 601     r2 = BN_CTX_get(ctx);
 602     m1 = BN_CTX_get(ctx);
 603     vrfy = BN_CTX_get(ctx);
 604     if (vrfy == NULL)
 605         goto err;
 606
 607     if (rsa->version == RSA_ASN1_VERSION_MULTI
 608         && ((ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0
 609              || ex_primes > RSA_MAX_PRIME_NUM - 2))
 610         goto err;
 611
 612     if (rsa->flags & RSA_FLAG_CACHE_PRIVATE) {
 613         BIGNUM *factor = BN_new();
 614
 615         if (factor == NULL)
 616             goto err;
 617
 618         /*
 619          * Make sure BN_mod_inverse in Montgomery initialization uses the
 620          * BN_FLG_CONSTTIME flag
 621          */
 622         if (!(BN_with_flags(factor, rsa->p, BN_FLG_CONSTTIME),
 623               BN_MONT_CTX_set_locked(&rsa->_method_mod_p, rsa->lock,
 624                                      factor, ctx))
 625             || !(BN_with_flags(factor, rsa->q, BN_FLG_CONSTTIME),
 626                  BN_MONT_CTX_set_locked(&rsa->_method_mod_q, rsa->lock,
 627                                         factor, ctx))) {
 628             BN_free(factor);
 629             goto err;
 630         }
 631         for (i = 0; i < ex_primes; i++) {
 632             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 633             BN_with_flags(factor, pinfo->r, BN_FLG_CONSTTIME);
 634             if (!BN_MONT_CTX_set_locked(&pinfo->m, rsa->lock, factor, ctx)) {
 635                 BN_free(factor);
 636                 goto err;
 637             }
 638         }
 639         /*
 640          * We MUST free |factor| before any further use of the prime factors
 641          */
 642         BN_free(factor);
 643
 644         smooth = (ex_primes == 0)
 645                  && (rsa->meth->bn_mod_exp == BN_mod_exp_mont)
 646                  && (BN_num_bits(rsa->q) == BN_num_bits(rsa->p));
 647     }
 648
 649     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 650         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 651                                     rsa->n, ctx))
 652             goto err;
 653
 654     if (smooth) {
 655         /*
 656          * Conversion from Montgomery domain, a.k.a. Montgomery reduction,
 657          * accepts values in [0-m*2^w) range. w is m's bit width rounded up
 658          * to limb width. So that at the very least if |I| is fully reduced,
 659          * i.e. less than p*q, we can count on from-to round to perform
 660          * below modulo operations on |I|. Unlike BN_mod it's constant time.
 661          */
 662         if (/* m1 = I moq q */
 663             !bn_from_mont_fixed_top(m1, I, rsa->_method_mod_q, ctx)
 664             || !bn_to_mont_fixed_top(m1, m1, rsa->_method_mod_q, ctx)
 665             /* m1 = m1^dmq1 mod q */
 666             || !BN_mod_exp_mont_consttime(m1, m1, rsa->dmq1, rsa->q, ctx,
 667                                           rsa->_method_mod_q)
 668             /* r1 = I mod p */
 669             || !bn_from_mont_fixed_top(r1, I, rsa->_method_mod_p, ctx)
 670             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 671             /* r1 = r1^dmp1 mod p */
 672             || !BN_mod_exp_mont_consttime(r1, r1, rsa->dmp1, rsa->p, ctx,
 673                                           rsa->_method_mod_p)
 674             /* r1 = (r1 - m1) mod p */
 675             /*
 676              * bn_mod_sub_fixed_top is not regular modular subtraction,
 677              * it can tolerate subtrahend to be larger than modulus, but
 678              * not bit-wise wider. This makes up for uncommon q>p case,
 679              * when |m1| can be larger than |rsa->p|.
 680              */
 681             || !bn_mod_sub_fixed_top(r1, r1, m1, rsa->p)
 682
 683             /* r0 = r0 * iqmp mod p */
 684             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 685             || !bn_mul_mont_fixed_top(r1, r1, rsa->iqmp, rsa->_method_mod_p,
 686                                       ctx)
 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 }