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 "crypto/bn.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     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_CACHE_PUBLIC)
 290         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 291                                     rsa->n, ctx))
 292             goto err;
 293
 294     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 295         blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
 296         if (blinding == NULL) {
 297             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_INTERNAL_ERROR);
 298             goto err;
 299         }
 300     }
 301
 302     if (blinding != NULL) {
 303         if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
 304             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 305             goto err;
 306         }
 307         if (!rsa_blinding_convert(blinding, f, unblind, ctx))
 308             goto err;
 309     }
 310
 311     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 312         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 313         ((rsa->p != NULL) &&
 314          (rsa->q != NULL) &&
 315          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 316         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 317             goto err;
 318     } else {
 319         BIGNUM *d = BN_new();
 320         if (d == NULL) {
 321             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
 322             goto err;
 323         }
 324         if (rsa->d == NULL) {
 325             RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, RSA_R_MISSING_PRIVATE_KEY);
 326             BN_free(d);
 327             goto err;
 328         }
 329         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 330
 331         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 332                                    rsa->_method_mod_n)) {
 333             BN_free(d);
 334             goto err;
 335         }
 336         /* We MUST free d before any further use of rsa->d */
 337         BN_free(d);
 338     }
 339
 340     if (blinding)
 341         if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
 342             goto err;
 343
 344     if (padding == RSA_X931_PADDING) {
 345         if (!BN_sub(f, rsa->n, ret))
 346             goto err;
 347         if (BN_cmp(ret, f) > 0)
 348             res = f;
 349         else
 350             res = ret;
 351     } else {
 352         res = ret;
 353     }
 354
 355     /*
 356      * BN_bn2binpad puts in leading 0 bytes if the number is less than
 357      * the length of the modulus.
 358      */
 359     r = BN_bn2binpad(res, to, num);
 360  err:
 361     BN_CTX_end(ctx);
 362     BN_CTX_free(ctx);
 363     OPENSSL_clear_free(buf, num);
 364     return r;
 365 }
 366
 367 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
 368                                    unsigned char *to, RSA *rsa, int padding)
 369 {
 370     BIGNUM *f, *ret;
 371     int j, num = 0, r = -1;
 372     unsigned char *buf = NULL;
 373     BN_CTX *ctx = NULL;
 374     int local_blinding = 0;
 375     /*
 376      * Used only if the blinding structure is shared. A non-NULL unblind
 377      * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
 378      * the unblinding factor outside the blinding structure.
 379      */
 380     BIGNUM *unblind = NULL;
 381     BN_BLINDING *blinding = NULL;
 382
 383     if ((ctx = BN_CTX_new()) == NULL)
 384         goto err;
 385     BN_CTX_start(ctx);
 386     f = BN_CTX_get(ctx);
 387     ret = BN_CTX_get(ctx);
 388     num = BN_num_bytes(rsa->n);
 389     buf = OPENSSL_malloc(num);
 390     if (ret == NULL || buf == NULL) {
 391         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 392         goto err;
 393     }
 394
 395     /*
 396      * This check was for equality but PGP does evil things and chops off the
 397      * top '0' bytes
 398      */
 399     if (flen > num) {
 400         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
 401                RSA_R_DATA_GREATER_THAN_MOD_LEN);
 402         goto err;
 403     }
 404
 405     /* make data into a big number */
 406     if (BN_bin2bn(from, (int)flen, f) == NULL)
 407         goto err;
 408
 409     if (BN_ucmp(f, rsa->n) >= 0) {
 410         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
 411                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 412         goto err;
 413     }
 414
 415     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 416         blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
 417         if (blinding == NULL) {
 418             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_INTERNAL_ERROR);
 419             goto err;
 420         }
 421     }
 422
 423     if (blinding != NULL) {
 424         if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
 425             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 426             goto err;
 427         }
 428         if (!rsa_blinding_convert(blinding, f, unblind, ctx))
 429             goto err;
 430     }
 431
 432     /* do the decrypt */
 433     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 434         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 435         ((rsa->p != NULL) &&
 436          (rsa->q != NULL) &&
 437          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 438         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 439             goto err;
 440     } else {
 441         BIGNUM *d = BN_new();
 442         if (d == NULL) {
 443             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
 444             goto err;
 445         }
 446         if (rsa->d == NULL) {
 447             RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_MISSING_PRIVATE_KEY);
 448             BN_free(d);
 449             goto err;
 450         }
 451         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 452
 453         if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 454             if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 455                                         rsa->n, ctx)) {
 456                 BN_free(d);
 457                 goto err;
 458             }
 459         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 460                                    rsa->_method_mod_n)) {
 461             BN_free(d);
 462             goto err;
 463         }
 464         /* We MUST free d before any further use of rsa->d */
 465         BN_free(d);
 466     }
 467
 468     if (blinding)
 469         if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
 470             goto err;
 471
 472     j = BN_bn2binpad(ret, buf, num);
 473     if (j < 0)
 474         goto err;
 475
 476     switch (padding) {
 477     case RSA_PKCS1_PADDING:
 478         r = RSA_padding_check_PKCS1_type_2(to, num, buf, j, num);
 479         break;
 480     case RSA_PKCS1_OAEP_PADDING:
 481         r = RSA_padding_check_PKCS1_OAEP(to, num, buf, j, num, NULL, 0);
 482         break;
 483     case RSA_SSLV23_PADDING:
 484         r = RSA_padding_check_SSLv23(to, num, buf, j, num);
 485         break;
 486     case RSA_NO_PADDING:
 487         memcpy(to, buf, (r = j));
 488         break;
 489     default:
 490         RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 491         goto err;
 492     }
 493     RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
 494     err_clear_last_constant_time(1 & ~constant_time_msb(r));
 495
 496  err:
 497     BN_CTX_end(ctx);
 498     BN_CTX_free(ctx);
 499     OPENSSL_clear_free(buf, num);
 500     return r;
 501 }
 502
 503 /* signature verification */
 504 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
 505                                   unsigned char *to, RSA *rsa, int padding)
 506 {
 507     BIGNUM *f, *ret;
 508     int i, num = 0, r = -1;
 509     unsigned char *buf = NULL;
 510     BN_CTX *ctx = NULL;
 511
 512     if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
 513         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_MODULUS_TOO_LARGE);
 514         return -1;
 515     }
 516
 517     if (BN_ucmp(rsa->n, rsa->e) <= 0) {
 518         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
 519         return -1;
 520     }
 521
 522     /* for large moduli, enforce exponent limit */
 523     if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
 524         if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
 525             RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
 526             return -1;
 527         }
 528     }
 529
 530     if ((ctx = BN_CTX_new()) == NULL)
 531         goto err;
 532     BN_CTX_start(ctx);
 533     f = BN_CTX_get(ctx);
 534     ret = BN_CTX_get(ctx);
 535     num = BN_num_bytes(rsa->n);
 536     buf = OPENSSL_malloc(num);
 537     if (ret == NULL || buf == NULL) {
 538         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, ERR_R_MALLOC_FAILURE);
 539         goto err;
 540     }
 541
 542     /*
 543      * This check was for equality but PGP does evil things and chops off the
 544      * top '0' bytes
 545      */
 546     if (flen > num) {
 547         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_DATA_GREATER_THAN_MOD_LEN);
 548         goto err;
 549     }
 550
 551     if (BN_bin2bn(from, flen, f) == NULL)
 552         goto err;
 553
 554     if (BN_ucmp(f, rsa->n) >= 0) {
 555         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT,
 556                RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 557         goto err;
 558     }
 559
 560     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 561         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 562                                     rsa->n, ctx))
 563             goto err;
 564
 565     if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
 566                                rsa->_method_mod_n))
 567         goto err;
 568
 569     if ((padding == RSA_X931_PADDING) && ((bn_get_words(ret)[0] & 0xf) != 12))
 570         if (!BN_sub(ret, rsa->n, ret))
 571             goto err;
 572
 573     i = BN_bn2binpad(ret, buf, num);
 574     if (i < 0)
 575         goto err;
 576
 577     switch (padding) {
 578     case RSA_PKCS1_PADDING:
 579         r = RSA_padding_check_PKCS1_type_1(to, num, buf, i, num);
 580         break;
 581     case RSA_X931_PADDING:
 582         r = RSA_padding_check_X931(to, num, buf, i, num);
 583         break;
 584     case RSA_NO_PADDING:
 585         memcpy(to, buf, (r = i));
 586         break;
 587     default:
 588         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
 589         goto err;
 590     }
 591     if (r < 0)
 592         RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
 593
 594  err:
 595     BN_CTX_end(ctx);
 596     BN_CTX_free(ctx);
 597     OPENSSL_clear_free(buf, num);
 598     return r;
 599 }
 600
 601 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 602 {
 603     BIGNUM *r1, *m1, *vrfy, *r2, *m[RSA_MAX_PRIME_NUM - 2];
 604     int ret = 0, i, ex_primes = 0, smooth = 0;
 605     RSA_PRIME_INFO *pinfo;
 606
 607     BN_CTX_start(ctx);
 608
 609     r1 = BN_CTX_get(ctx);
 610     r2 = BN_CTX_get(ctx);
 611     m1 = BN_CTX_get(ctx);
 612     vrfy = BN_CTX_get(ctx);
 613     if (vrfy == NULL)
 614         goto err;
 615
 616     if (rsa->version == RSA_ASN1_VERSION_MULTI
 617         && ((ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0
 618              || ex_primes > RSA_MAX_PRIME_NUM - 2))
 619         goto err;
 620
 621     if (rsa->flags & RSA_FLAG_CACHE_PRIVATE) {
 622         BIGNUM *factor = BN_new();
 623
 624         if (factor == NULL)
 625             goto err;
 626
 627         /*
 628          * Make sure BN_mod_inverse in Montgomery initialization uses the
 629          * BN_FLG_CONSTTIME flag
 630          */
 631         if (!(BN_with_flags(factor, rsa->p, BN_FLG_CONSTTIME),
 632               BN_MONT_CTX_set_locked(&rsa->_method_mod_p, rsa->lock,
 633                                      factor, ctx))
 634             || !(BN_with_flags(factor, rsa->q, BN_FLG_CONSTTIME),
 635                  BN_MONT_CTX_set_locked(&rsa->_method_mod_q, rsa->lock,
 636                                         factor, ctx))) {
 637             BN_free(factor);
 638             goto err;
 639         }
 640         for (i = 0; i < ex_primes; i++) {
 641             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 642             BN_with_flags(factor, pinfo->r, BN_FLG_CONSTTIME);
 643             if (!BN_MONT_CTX_set_locked(&pinfo->m, rsa->lock, factor, ctx)) {
 644                 BN_free(factor);
 645                 goto err;
 646             }
 647         }
 648         /*
 649          * We MUST free |factor| before any further use of the prime factors
 650          */
 651         BN_free(factor);
 652
 653         smooth = (ex_primes == 0)
 654                  && (rsa->meth->bn_mod_exp == BN_mod_exp_mont)
 655                  && (BN_num_bits(rsa->q) == BN_num_bits(rsa->p));
 656     }
 657
 658     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 659         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 660                                     rsa->n, ctx))
 661             goto err;
 662
 663     if (smooth) {
 664         /*
 665          * Conversion from Montgomery domain, a.k.a. Montgomery reduction,
 666          * accepts values in [0-m*2^w) range. w is m's bit width rounded up
 667          * to limb width. So that at the very least if |I| is fully reduced,
 668          * i.e. less than p*q, we can count on from-to round to perform
 669          * below modulo operations on |I|. Unlike BN_mod it's constant time.
 670          */
 671         if (/* m1 = I moq q */
 672             !bn_from_mont_fixed_top(m1, I, rsa->_method_mod_q, ctx)
 673             || !bn_to_mont_fixed_top(m1, m1, rsa->_method_mod_q, ctx)
 674             /* m1 = m1^dmq1 mod q */
 675             || !BN_mod_exp_mont_consttime(m1, m1, rsa->dmq1, rsa->q, ctx,
 676                                           rsa->_method_mod_q)
 677             /* r1 = I mod p */
 678             || !bn_from_mont_fixed_top(r1, I, rsa->_method_mod_p, ctx)
 679             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 680             /* r1 = r1^dmp1 mod p */
 681             || !BN_mod_exp_mont_consttime(r1, r1, rsa->dmp1, rsa->p, ctx,
 682                                           rsa->_method_mod_p)
 683             /* r1 = (r1 - m1) mod p */
 684             /*
 685              * bn_mod_sub_fixed_top is not regular modular subtraction,
 686              * it can tolerate subtrahend to be larger than modulus, but
 687              * not bit-wise wider. This makes up for uncommon q>p case,
 688              * when |m1| can be larger than |rsa->p|.
 689              */
 690             || !bn_mod_sub_fixed_top(r1, r1, m1, rsa->p)
 691
 692             /* r1 = r1 * iqmp mod p */
 693             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 694             || !bn_mul_mont_fixed_top(r1, r1, rsa->iqmp, rsa->_method_mod_p,
 695                                       ctx)
 696             /* r0 = r1 * q + m1 */
 697             || !bn_mul_fixed_top(r0, r1, rsa->q, ctx)
 698             || !bn_mod_add_fixed_top(r0, r0, m1, rsa->n))
 699             goto err;
 700
 701         goto tail;
 702     }
 703
 704     /* compute I mod q */
 705     {
 706         BIGNUM *c = BN_new();
 707         if (c == NULL)
 708             goto err;
 709         BN_with_flags(c, I, BN_FLG_CONSTTIME);
 710
 711         if (!BN_mod(r1, c, rsa->q, ctx)) {
 712             BN_free(c);
 713             goto err;
 714         }
 715
 716         {
 717             BIGNUM *dmq1 = BN_new();
 718             if (dmq1 == NULL) {
 719                 BN_free(c);
 720                 goto err;
 721             }
 722             BN_with_flags(dmq1, rsa->dmq1, BN_FLG_CONSTTIME);
 723
 724             /* compute r1^dmq1 mod q */
 725             if (!rsa->meth->bn_mod_exp(m1, r1, dmq1, rsa->q, ctx,
 726                                        rsa->_method_mod_q)) {
 727                 BN_free(c);
 728                 BN_free(dmq1);
 729                 goto err;
 730             }
 731             /* We MUST free dmq1 before any further use of rsa->dmq1 */
 732             BN_free(dmq1);
 733         }
 734
 735         /* compute I mod p */
 736         if (!BN_mod(r1, c, rsa->p, ctx)) {
 737             BN_free(c);
 738             goto err;
 739         }
 740         /* We MUST free c before any further use of I */
 741         BN_free(c);
 742     }
 743
 744     {
 745         BIGNUM *dmp1 = BN_new();
 746         if (dmp1 == NULL)
 747             goto err;
 748         BN_with_flags(dmp1, rsa->dmp1, BN_FLG_CONSTTIME);
 749
 750         /* compute r1^dmp1 mod p */
 751         if (!rsa->meth->bn_mod_exp(r0, r1, dmp1, rsa->p, ctx,
 752                                    rsa->_method_mod_p)) {
 753             BN_free(dmp1);
 754             goto err;
 755         }
 756         /* We MUST free dmp1 before any further use of rsa->dmp1 */
 757         BN_free(dmp1);
 758     }
 759
 760     /*
 761      * calculate m_i in multi-prime case
 762      *
 763      * TODO:
 764      * 1. squash the following two loops and calculate |m_i| there.
 765      * 2. remove cc and reuse |c|.
 766      * 3. remove |dmq1| and |dmp1| in previous block and use |di|.
 767      *
 768      * If these things are done, the code will be more readable.
 769      */
 770     if (ex_primes > 0) {
 771         BIGNUM *di = BN_new(), *cc = BN_new();
 772
 773         if (cc == NULL || di == NULL) {
 774             BN_free(cc);
 775             BN_free(di);
 776             goto err;
 777         }
 778
 779         for (i = 0; i < ex_primes; i++) {
 780             /* prepare m_i */
 781             if ((m[i] = BN_CTX_get(ctx)) == NULL) {
 782                 BN_free(cc);
 783                 BN_free(di);
 784                 goto err;
 785             }
 786
 787             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 788
 789             /* prepare c and d_i */
 790             BN_with_flags(cc, I, BN_FLG_CONSTTIME);
 791             BN_with_flags(di, pinfo->d, BN_FLG_CONSTTIME);
 792
 793             if (!BN_mod(r1, cc, pinfo->r, ctx)) {
 794                 BN_free(cc);
 795                 BN_free(di);
 796                 goto err;
 797             }
 798             /* compute r1 ^ d_i mod r_i */
 799             if (!rsa->meth->bn_mod_exp(m[i], r1, di, pinfo->r, ctx, pinfo->m)) {
 800                 BN_free(cc);
 801                 BN_free(di);
 802                 goto err;
 803             }
 804         }
 805
 806         BN_free(cc);
 807         BN_free(di);
 808     }
 809
 810     if (!BN_sub(r0, r0, m1))
 811         goto err;
 812     /*
 813      * This will help stop the size of r0 increasing, which does affect the
 814      * multiply if it optimised for a power of 2 size
 815      */
 816     if (BN_is_negative(r0))
 817         if (!BN_add(r0, r0, rsa->p))
 818             goto err;
 819
 820     if (!BN_mul(r1, r0, rsa->iqmp, ctx))
 821         goto err;
 822
 823     {
 824         BIGNUM *pr1 = BN_new();
 825         if (pr1 == NULL)
 826             goto err;
 827         BN_with_flags(pr1, r1, BN_FLG_CONSTTIME);
 828
 829         if (!BN_mod(r0, pr1, rsa->p, ctx)) {
 830             BN_free(pr1);
 831             goto err;
 832         }
 833         /* We MUST free pr1 before any further use of r1 */
 834         BN_free(pr1);
 835     }
 836
 837     /*
 838      * If p < q it is occasionally possible for the correction of adding 'p'
 839      * if r0 is negative above to leave the result still negative. This can
 840      * break the private key operations: the following second correction
 841      * should *always* correct this rare occurrence. This will *never* happen
 842      * with OpenSSL generated keys because they ensure p > q [steve]
 843      */
 844     if (BN_is_negative(r0))
 845         if (!BN_add(r0, r0, rsa->p))
 846             goto err;
 847     if (!BN_mul(r1, r0, rsa->q, ctx))
 848         goto err;
 849     if (!BN_add(r0, r1, m1))
 850         goto err;
 851
 852     /* add m_i to m in multi-prime case */
 853     if (ex_primes > 0) {
 854         BIGNUM *pr2 = BN_new();
 855
 856         if (pr2 == NULL)
 857             goto err;
 858
 859         for (i = 0; i < ex_primes; i++) {
 860             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 861             if (!BN_sub(r1, m[i], r0)) {
 862                 BN_free(pr2);
 863                 goto err;
 864             }
 865
 866             if (!BN_mul(r2, r1, pinfo->t, ctx)) {
 867                 BN_free(pr2);
 868                 goto err;
 869             }
 870
 871             BN_with_flags(pr2, r2, BN_FLG_CONSTTIME);
 872
 873             if (!BN_mod(r1, pr2, pinfo->r, ctx)) {
 874                 BN_free(pr2);
 875                 goto err;
 876             }
 877
 878             if (BN_is_negative(r1))
 879                 if (!BN_add(r1, r1, pinfo->r)) {
 880                     BN_free(pr2);
 881                     goto err;
 882                 }
 883             if (!BN_mul(r1, r1, pinfo->pp, ctx)) {
 884                 BN_free(pr2);
 885                 goto err;
 886             }
 887             if (!BN_add(r0, r0, r1)) {
 888                 BN_free(pr2);
 889                 goto err;
 890             }
 891         }
 892         BN_free(pr2);
 893     }
 894
 895  tail:
 896     if (rsa->e && rsa->n) {
 897         if (rsa->meth->bn_mod_exp == BN_mod_exp_mont) {
 898             if (!BN_mod_exp_mont(vrfy, r0, rsa->e, rsa->n, ctx,
 899                                  rsa->_method_mod_n))
 900                 goto err;
 901         } else {
 902             bn_correct_top(r0);
 903             if (!rsa->meth->bn_mod_exp(vrfy, r0, rsa->e, rsa->n, ctx,
 904                                        rsa->_method_mod_n))
 905                 goto err;
 906         }
 907         /*
 908          * If 'I' was greater than (or equal to) rsa->n, the operation will
 909          * be equivalent to using 'I mod n'. However, the result of the
 910          * verify will *always* be less than 'n' so we don't check for
 911          * absolute equality, just congruency.
 912          */
 913         if (!BN_sub(vrfy, vrfy, I))
 914             goto err;
 915         if (BN_is_zero(vrfy)) {
 916             bn_correct_top(r0);
 917             ret = 1;
 918             goto err;   /* not actually error */
 919         }
 920         if (!BN_mod(vrfy, vrfy, rsa->n, ctx))
 921             goto err;
 922         if (BN_is_negative(vrfy))
 923             if (!BN_add(vrfy, vrfy, rsa->n))
 924                 goto err;
 925         if (!BN_is_zero(vrfy)) {
 926             /*
 927              * 'I' and 'vrfy' aren't congruent mod n. Don't leak
 928              * miscalculated CRT output, just do a raw (slower) mod_exp and
 929              * return that instead.
 930              */
 931
 932             BIGNUM *d = BN_new();
 933             if (d == NULL)
 934                 goto err;
 935             BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 936
 937             if (!rsa->meth->bn_mod_exp(r0, I, d, rsa->n, ctx,
 938                                        rsa->_method_mod_n)) {
 939                 BN_free(d);
 940                 goto err;
 941             }
 942             /* We MUST free d before any further use of rsa->d */
 943             BN_free(d);
 944         }
 945     }
 946     /*
 947      * It's unfortunate that we have to bn_correct_top(r0). What hopefully
 948      * saves the day is that correction is highly unlike, and private key
 949      * operations are customarily performed on blinded message. Which means
 950      * that attacker won't observe correlation with chosen plaintext.
 951      * Secondly, remaining code would still handle it in same computational
 952      * time and even conceal memory access pattern around corrected top.
 953      */
 954     bn_correct_top(r0);
 955     ret = 1;
 956  err:
 957     BN_CTX_end(ctx);
 958     return ret;
 959 }
 960
 961 static int rsa_ossl_init(RSA *rsa)
 962 {
 963     rsa->flags |= RSA_FLAG_CACHE_PUBLIC | RSA_FLAG_CACHE_PRIVATE;
 964     return 1;
 965 }
 966
 967 static int rsa_ossl_finish(RSA *rsa)
 968 {
 969     int i;
 970     RSA_PRIME_INFO *pinfo;
 971
 972     BN_MONT_CTX_free(rsa->_method_mod_n);
 973     BN_MONT_CTX_free(rsa->_method_mod_p);
 974     BN_MONT_CTX_free(rsa->_method_mod_q);
 975     for (i = 0; i < sk_RSA_PRIME_INFO_num(rsa->prime_infos); i++) {
 976         pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 977         BN_MONT_CTX_free(pinfo->m);
 978     }
 979     return 1;
 980 }