crypto/rsa/rsa_ossl.c

   1 /*
   2  * Copyright 1995-2024 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 /*
  11  * RSA low level APIs are deprecated for public use, but still ok for
  12  * internal use.
  13  */
  14 #include "internal/deprecated.h"
  15
  16 #include "internal/cryptlib.h"
  17 #include "crypto/bn.h"
  18 #include "crypto/sparse_array.h"
  19 #include "rsa_local.h"
  20 #include "internal/constant_time.h"
  21 #include <openssl/evp.h>
  22 #include <openssl/sha.h>
  23 #include <openssl/hmac.h>
  24
  25 DEFINE_SPARSE_ARRAY_OF(BN_BLINDING);
  26
  27 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
  28                                   unsigned char *to, RSA *rsa, int padding);
  29 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
  30                                    unsigned char *to, RSA *rsa, int padding);
  31 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
  32                                   unsigned char *to, RSA *rsa, int padding);
  33 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
  34                                    unsigned char *to, RSA *rsa, int padding);
  35 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
  36                            BN_CTX *ctx);
  37 static int rsa_ossl_init(RSA *rsa);
  38 static int rsa_ossl_finish(RSA *rsa);
  39 #ifdef S390X_MOD_EXP
  40 static int rsa_ossl_s390x_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
  41                                 BN_CTX *ctx);
  42 static RSA_METHOD rsa_pkcs1_ossl_meth = {
  43     "OpenSSL PKCS#1 RSA",
  44     rsa_ossl_public_encrypt,
  45     rsa_ossl_public_decrypt,     /* signature verification */
  46     rsa_ossl_private_encrypt,    /* signing */
  47     rsa_ossl_private_decrypt,
  48     rsa_ossl_s390x_mod_exp,
  49     s390x_mod_exp,
  50     rsa_ossl_init,
  51     rsa_ossl_finish,
  52     RSA_FLAG_FIPS_METHOD,       /* flags */
  53     NULL,
  54     0,                          /* rsa_sign */
  55     0,                          /* rsa_verify */
  56     NULL,                       /* rsa_keygen */
  57     NULL                        /* rsa_multi_prime_keygen */
  58 };
  59 #else
  60 static RSA_METHOD rsa_pkcs1_ossl_meth = {
  61     "OpenSSL PKCS#1 RSA",
  62     rsa_ossl_public_encrypt,
  63     rsa_ossl_public_decrypt,     /* signature verification */
  64     rsa_ossl_private_encrypt,    /* signing */
  65     rsa_ossl_private_decrypt,
  66     rsa_ossl_mod_exp,
  67     BN_mod_exp_mont,            /* XXX probably we should not use Montgomery
  68                                  * if e == 3 */
  69     rsa_ossl_init,
  70     rsa_ossl_finish,
  71     RSA_FLAG_FIPS_METHOD,       /* flags */
  72     NULL,
  73     0,                          /* rsa_sign */
  74     0,                          /* rsa_verify */
  75     NULL,                       /* rsa_keygen */
  76     NULL                        /* rsa_multi_prime_keygen */
  77 };
  78 #endif
  79
  80 static const RSA_METHOD *default_RSA_meth = &rsa_pkcs1_ossl_meth;
  81
  82 void RSA_set_default_method(const RSA_METHOD *meth)
  83 {
  84     default_RSA_meth = meth;
  85 }
  86
  87 const RSA_METHOD *RSA_get_default_method(void)
  88 {
  89     return default_RSA_meth;
  90 }
  91
  92 const RSA_METHOD *RSA_PKCS1_OpenSSL(void)
  93 {
  94     return &rsa_pkcs1_ossl_meth;
  95 }
  96
  97 const RSA_METHOD *RSA_null_method(void)
  98 {
  99     return NULL;
 100 }
 101
 102 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
 103                                   unsigned char *to, RSA *rsa, int padding)
 104 {
 105     BIGNUM *f, *ret;
 106     int i, num = 0, r = -1;
 107     unsigned char *buf = NULL;
 108     BN_CTX *ctx = NULL;
 109
 110     if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
 111         ERR_raise(ERR_LIB_RSA, RSA_R_MODULUS_TOO_LARGE);
 112         return -1;
 113     }
 114
 115     if (BN_ucmp(rsa->n, rsa->e) <= 0) {
 116         ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
 117         return -1;
 118     }
 119
 120     /* for large moduli, enforce exponent limit */
 121     if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
 122         if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
 123             ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
 124             return -1;
 125         }
 126     }
 127
 128     if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
 129         goto err;
 130     BN_CTX_start(ctx);
 131     f = BN_CTX_get(ctx);
 132     ret = BN_CTX_get(ctx);
 133     num = BN_num_bytes(rsa->n);
 134     buf = OPENSSL_malloc(num);
 135     if (ret == NULL || buf == NULL)
 136         goto err;
 137
 138     switch (padding) {
 139     case RSA_PKCS1_PADDING:
 140         i = ossl_rsa_padding_add_PKCS1_type_2_ex(rsa->libctx, buf, num,
 141                                                  from, flen);
 142         break;
 143     case RSA_PKCS1_OAEP_PADDING:
 144         i = ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(rsa->libctx, buf, num,
 145                                                     from, flen, NULL, 0,
 146                                                     NULL, NULL);
 147         break;
 148     case RSA_NO_PADDING:
 149         i = RSA_padding_add_none(buf, num, from, flen);
 150         break;
 151     default:
 152         ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
 153         goto err;
 154     }
 155     if (i <= 0)
 156         goto err;
 157
 158     if (BN_bin2bn(buf, num, f) == NULL)
 159         goto err;
 160
 161 #ifdef FIPS_MODULE
 162     /*
 163      * See SP800-56Br2, section 7.1.1.1
 164      * RSAEP: 1 < f < (n – 1).
 165      * (where f is the plaintext).
 166      */
 167     if (padding == RSA_NO_PADDING) {
 168         BIGNUM *nminus1 = BN_CTX_get(ctx);
 169
 170         if (BN_ucmp(f, BN_value_one()) <= 0) {
 171             ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_SMALL);
 172             goto err;
 173         }
 174         if (nminus1 == NULL
 175                 || BN_copy(nminus1, rsa->n) == NULL
 176                 || !BN_sub_word(nminus1, 1))
 177             goto err;
 178         if (BN_ucmp(f, nminus1) >= 0) {
 179             ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 180             goto err;
 181         }
 182     } else
 183 #endif
 184     {
 185         if (BN_ucmp(f, rsa->n) >= 0) {
 186             /* usually the padding functions would catch this */
 187             ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 188             goto err;
 189         }
 190     }
 191
 192     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 193         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 194                                     rsa->n, ctx))
 195             goto err;
 196
 197     if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
 198                                rsa->_method_mod_n))
 199         goto err;
 200
 201     /*
 202      * BN_bn2binpad puts in leading 0 bytes if the number is less than
 203      * the length of the modulus.
 204      */
 205     r = BN_bn2binpad(ret, to, num);
 206  err:
 207     BN_CTX_end(ctx);
 208     BN_CTX_free(ctx);
 209     OPENSSL_clear_free(buf, num);
 210     return r;
 211 }
 212
 213 static void free_bn_blinding(ossl_uintmax_t idx, BN_BLINDING *b, void *arg)
 214 {
 215     BN_BLINDING_free(b);
 216 }
 217
 218 void ossl_rsa_free_blinding(RSA *rsa)
 219 {
 220     SPARSE_ARRAY_OF(BN_BLINDING) *blindings = rsa->blindings_sa;
 221
 222     ossl_sa_BN_BLINDING_doall_arg(blindings, free_bn_blinding, NULL);
 223     ossl_sa_BN_BLINDING_free(blindings);
 224 }
 225
 226 void *ossl_rsa_alloc_blinding(void)
 227 {
 228     return ossl_sa_BN_BLINDING_new();
 229 }
 230
 231 static BN_BLINDING *ossl_rsa_get_thread_bn_blinding(RSA *rsa)
 232 {
 233     SPARSE_ARRAY_OF(BN_BLINDING) *blindings = rsa->blindings_sa;
 234     uintptr_t tid = (uintptr_t)CRYPTO_THREAD_get_current_id();
 235
 236     return ossl_sa_BN_BLINDING_get(blindings, tid);
 237 }
 238
 239 static int ossl_rsa_set_thread_bn_blinding(RSA *rsa, BN_BLINDING *b)
 240 {
 241     SPARSE_ARRAY_OF(BN_BLINDING) *blindings = rsa->blindings_sa;
 242     uintptr_t tid = (uintptr_t)CRYPTO_THREAD_get_current_id();
 243
 244     return ossl_sa_BN_BLINDING_set(blindings, tid, b);
 245 }
 246
 247 static BN_BLINDING *rsa_get_blinding(RSA *rsa, BN_CTX *ctx)
 248 {
 249     BN_BLINDING *ret;
 250
 251     if (!CRYPTO_THREAD_read_lock(rsa->lock))
 252         return NULL;
 253
 254     ret = ossl_rsa_get_thread_bn_blinding(rsa);
 255     CRYPTO_THREAD_unlock(rsa->lock);
 256
 257     if (ret == NULL) {
 258         ret = RSA_setup_blinding(rsa, ctx);
 259         if (!CRYPTO_THREAD_write_lock(rsa->lock)) {
 260             BN_BLINDING_free(ret);
 261             ret = NULL;
 262         } else {
 263             if (!ossl_rsa_set_thread_bn_blinding(rsa, ret)) {
 264                 BN_BLINDING_free(ret);
 265                 ret = NULL;
 266             }
 267         }
 268         CRYPTO_THREAD_unlock(rsa->lock);
 269     }
 270
 271     return ret;
 272 }
 273
 274 static int rsa_blinding_convert(BN_BLINDING *b, BIGNUM *f, BN_CTX *ctx)
 275 {
 276     /*
 277      * Local blinding: store the unblinding factor in BN_BLINDING.
 278      */
 279     return BN_BLINDING_convert_ex(f, NULL, b, ctx);
 280 }
 281
 282 static int rsa_blinding_invert(BN_BLINDING *b, BIGNUM *f, BN_CTX *ctx)
 283 {
 284     /*
 285      * For local blinding, unblind is set to NULL, and BN_BLINDING_invert_ex
 286      * will use the unblinding factor stored in BN_BLINDING. If BN_BLINDING
 287      * is shared between threads, unblind must be non-null:
 288      * BN_BLINDING_invert_ex will then use the local unblinding factor, and
 289      * will only read the modulus from BN_BLINDING. In both cases it's safe
 290      * to access the blinding without a lock.
 291      */
 292     BN_set_flags(f, BN_FLG_CONSTTIME);
 293     return BN_BLINDING_invert_ex(f, NULL, b, ctx);
 294 }
 295
 296 /* signing */
 297 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
 298                                    unsigned char *to, RSA *rsa, int padding)
 299 {
 300     BIGNUM *f, *ret, *res;
 301     int i, num = 0, r = -1;
 302     unsigned char *buf = NULL;
 303     BN_CTX *ctx = NULL;
 304     BN_BLINDING *blinding = NULL;
 305
 306     if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
 307         goto err;
 308     BN_CTX_start(ctx);
 309     f = BN_CTX_get(ctx);
 310     ret = BN_CTX_get(ctx);
 311     num = BN_num_bytes(rsa->n);
 312     buf = OPENSSL_malloc(num);
 313     if (ret == NULL || buf == NULL)
 314         goto err;
 315
 316     switch (padding) {
 317     case RSA_PKCS1_PADDING:
 318         i = RSA_padding_add_PKCS1_type_1(buf, num, from, flen);
 319         break;
 320     case RSA_X931_PADDING:
 321         i = RSA_padding_add_X931(buf, num, from, flen);
 322         break;
 323     case RSA_NO_PADDING:
 324         i = RSA_padding_add_none(buf, num, from, flen);
 325         break;
 326     default:
 327         ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
 328         goto err;
 329     }
 330     if (i <= 0)
 331         goto err;
 332
 333     if (BN_bin2bn(buf, num, f) == NULL)
 334         goto err;
 335
 336     if (BN_ucmp(f, rsa->n) >= 0) {
 337         /* usually the padding functions would catch this */
 338         ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 339         goto err;
 340     }
 341
 342     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 343         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 344                                     rsa->n, ctx))
 345             goto err;
 346
 347     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 348         blinding = rsa_get_blinding(rsa, ctx);
 349         if (blinding == NULL) {
 350             ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 351             goto err;
 352         }
 353
 354         if (!rsa_blinding_convert(blinding, f, ctx))
 355             goto err;
 356     }
 357
 358     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 359         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 360         ((rsa->p != NULL) &&
 361          (rsa->q != NULL) &&
 362          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 363         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 364             goto err;
 365     } else {
 366         BIGNUM *d = BN_new();
 367         if (d == NULL) {
 368             ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
 369             goto err;
 370         }
 371         if (rsa->d == NULL) {
 372             ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
 373             BN_free(d);
 374             goto err;
 375         }
 376         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 377
 378         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 379                                    rsa->_method_mod_n)) {
 380             BN_free(d);
 381             goto err;
 382         }
 383         /* We MUST free d before any further use of rsa->d */
 384         BN_free(d);
 385     }
 386
 387     if (blinding)
 388         if (!rsa_blinding_invert(blinding, ret, ctx))
 389             goto err;
 390
 391     if (padding == RSA_X931_PADDING) {
 392         if (!BN_sub(f, rsa->n, ret))
 393             goto err;
 394         if (BN_cmp(ret, f) > 0)
 395             res = f;
 396         else
 397             res = ret;
 398     } else {
 399         res = ret;
 400     }
 401
 402     /*
 403      * BN_bn2binpad puts in leading 0 bytes if the number is less than
 404      * the length of the modulus.
 405      */
 406     r = BN_bn2binpad(res, to, num);
 407  err:
 408     BN_CTX_end(ctx);
 409     BN_CTX_free(ctx);
 410     OPENSSL_clear_free(buf, num);
 411     return r;
 412 }
 413
 414 static int derive_kdk(int flen, const unsigned char *from, RSA *rsa,
 415                       unsigned char *buf, int num, unsigned char *kdk)
 416 {
 417     int ret = 0;
 418     HMAC_CTX *hmac = NULL;
 419     EVP_MD *md = NULL;
 420     unsigned int md_len = SHA256_DIGEST_LENGTH;
 421     unsigned char d_hash[SHA256_DIGEST_LENGTH] = {0};
 422     /*
 423      * because we use d as a handle to rsa->d we need to keep it local and
 424      * free before any further use of rsa->d
 425      */
 426     BIGNUM *d = BN_new();
 427
 428     if (d == NULL) {
 429         ERR_raise(ERR_LIB_RSA, ERR_R_CRYPTO_LIB);
 430         goto err;
 431     }
 432     if (rsa->d == NULL) {
 433         ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
 434         BN_free(d);
 435         goto err;
 436     }
 437     BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 438     if (BN_bn2binpad(d, buf, num) < 0) {
 439         ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 440         BN_free(d);
 441         goto err;
 442     }
 443     BN_free(d);
 444
 445     /*
 446      * we use hardcoded hash so that migrating between versions that use
 447      * different hash doesn't provide a Bleichenbacher oracle:
 448      * if the attacker can see that different versions return different
 449      * messages for the same ciphertext, they'll know that the message is
 450      * synthetically generated, which means that the padding check failed
 451      */
 452     md = EVP_MD_fetch(rsa->libctx, "sha256", NULL);
 453     if (md == NULL) {
 454         ERR_raise(ERR_LIB_RSA, ERR_R_FETCH_FAILED);
 455         goto err;
 456     }
 457
 458     if (EVP_Digest(buf, num, d_hash, NULL, md, NULL) <= 0) {
 459         ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 460         goto err;
 461     }
 462
 463     hmac = HMAC_CTX_new();
 464     if (hmac == NULL) {
 465         ERR_raise(ERR_LIB_RSA, ERR_R_CRYPTO_LIB);
 466         goto err;
 467     }
 468
 469     if (HMAC_Init_ex(hmac, d_hash, sizeof(d_hash), md, NULL) <= 0) {
 470         ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 471         goto err;
 472     }
 473
 474     if (flen < num) {
 475         memset(buf, 0, num - flen);
 476         if (HMAC_Update(hmac, buf, num - flen) <= 0) {
 477             ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 478             goto err;
 479         }
 480     }
 481     if (HMAC_Update(hmac, from, flen) <= 0) {
 482         ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 483         goto err;
 484     }
 485
 486     md_len = SHA256_DIGEST_LENGTH;
 487     if (HMAC_Final(hmac, kdk, &md_len) <= 0) {
 488         ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 489         goto err;
 490     }
 491     ret = 1;
 492
 493  err:
 494     HMAC_CTX_free(hmac);
 495     EVP_MD_free(md);
 496     return ret;
 497 }
 498
 499 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
 500                                    unsigned char *to, RSA *rsa, int padding)
 501 {
 502     BIGNUM *f, *ret;
 503     int j, num = 0, r = -1;
 504     unsigned char *buf = NULL;
 505     unsigned char kdk[SHA256_DIGEST_LENGTH] = {0};
 506     BN_CTX *ctx = NULL;
 507     BN_BLINDING *blinding = NULL;
 508
 509     /*
 510      * we need the value of the private exponent to perform implicit rejection
 511      */
 512     if ((rsa->flags & RSA_FLAG_EXT_PKEY) && (padding == RSA_PKCS1_PADDING))
 513         padding = RSA_PKCS1_NO_IMPLICIT_REJECT_PADDING;
 514
 515     if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
 516         goto err;
 517     BN_CTX_start(ctx);
 518     f = BN_CTX_get(ctx);
 519     ret = BN_CTX_get(ctx);
 520     if (ret == NULL) {
 521         ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
 522         goto err;
 523     }
 524     num = BN_num_bytes(rsa->n);
 525     buf = OPENSSL_malloc(num);
 526     if (buf == NULL)
 527         goto err;
 528
 529     /*
 530      * This check was for equality but PGP does evil things and chops off the
 531      * top '0' bytes
 532      */
 533     if (flen > num) {
 534         ERR_raise(ERR_LIB_RSA, RSA_R_DATA_GREATER_THAN_MOD_LEN);
 535         goto err;
 536     }
 537
 538     if (flen < 1) {
 539         ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_SMALL);
 540         goto err;
 541     }
 542
 543     /* make data into a big number */
 544     if (BN_bin2bn(from, (int)flen, f) == NULL)
 545         goto err;
 546
 547 #ifdef FIPS_MODULE
 548     /*
 549      * See SP800-56Br2, section 7.1.2.1
 550      * RSADP: 1 < f < (n – 1)
 551      * (where f is the ciphertext).
 552      */
 553     if (padding == RSA_NO_PADDING) {
 554         BIGNUM *nminus1 = BN_CTX_get(ctx);
 555
 556         if (BN_ucmp(f, BN_value_one()) <= 0) {
 557             ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_SMALL);
 558             goto err;
 559         }
 560         if (nminus1 == NULL
 561                 || BN_copy(nminus1, rsa->n) == NULL
 562                 || !BN_sub_word(nminus1, 1))
 563             goto err;
 564         if (BN_ucmp(f, nminus1) >= 0) {
 565             ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 566             goto err;
 567         }
 568     } else
 569 #endif
 570     {
 571         if (BN_ucmp(f, rsa->n) >= 0) {
 572             ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 573             goto err;
 574         }
 575     }
 576     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 577         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 578                                     rsa->n, ctx))
 579             goto err;
 580
 581     if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
 582         blinding = rsa_get_blinding(rsa, ctx);
 583         if (blinding == NULL) {
 584             ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
 585             goto err;
 586         }
 587
 588         if (!rsa_blinding_convert(blinding, f, ctx))
 589             goto err;
 590     }
 591
 592     /* do the decrypt */
 593     if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
 594         (rsa->version == RSA_ASN1_VERSION_MULTI) ||
 595         ((rsa->p != NULL) &&
 596          (rsa->q != NULL) &&
 597          (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
 598         if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
 599             goto err;
 600     } else {
 601         BIGNUM *d = BN_new();
 602         if (d == NULL) {
 603             ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
 604             goto err;
 605         }
 606         if (rsa->d == NULL) {
 607             ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
 608             BN_free(d);
 609             goto err;
 610         }
 611         BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
 612         if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
 613                                    rsa->_method_mod_n)) {
 614             BN_free(d);
 615             goto err;
 616         }
 617         /* We MUST free d before any further use of rsa->d */
 618         BN_free(d);
 619     }
 620
 621     if (blinding)
 622         if (!rsa_blinding_invert(blinding, ret, ctx))
 623             goto err;
 624
 625     /*
 626      * derive the Key Derivation Key from private exponent and public
 627      * ciphertext
 628      */
 629     if (padding == RSA_PKCS1_PADDING) {
 630         if (derive_kdk(flen, from, rsa, buf, num, kdk) == 0)
 631             goto err;
 632     }
 633
 634     j = BN_bn2binpad(ret, buf, num);
 635     if (j < 0)
 636         goto err;
 637
 638     switch (padding) {
 639     case RSA_PKCS1_NO_IMPLICIT_REJECT_PADDING:
 640         r = RSA_padding_check_PKCS1_type_2(to, num, buf, j, num);
 641         break;
 642     case RSA_PKCS1_PADDING:
 643         r = ossl_rsa_padding_check_PKCS1_type_2(rsa->libctx, to, num, buf, j, num, kdk);
 644         break;
 645     case RSA_PKCS1_OAEP_PADDING:
 646         r = RSA_padding_check_PKCS1_OAEP(to, num, buf, j, num, NULL, 0);
 647         break;
 648     case RSA_NO_PADDING:
 649         memcpy(to, buf, (r = j));
 650         break;
 651     default:
 652         ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
 653         goto err;
 654     }
 655 #ifndef FIPS_MODULE
 656     /*
 657      * This trick doesn't work in the FIPS provider because libcrypto manages
 658      * the error stack. Instead we opt not to put an error on the stack at all
 659      * in case of padding failure in the FIPS provider.
 660      */
 661     ERR_raise(ERR_LIB_RSA, RSA_R_PADDING_CHECK_FAILED);
 662     err_clear_last_constant_time(1 & ~constant_time_msb(r));
 663 #endif
 664
 665  err:
 666     BN_CTX_end(ctx);
 667     BN_CTX_free(ctx);
 668     OPENSSL_clear_free(buf, num);
 669     return r;
 670 }
 671
 672 /* signature verification */
 673 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
 674                                   unsigned char *to, RSA *rsa, int padding)
 675 {
 676     BIGNUM *f, *ret;
 677     int i, num = 0, r = -1;
 678     unsigned char *buf = NULL;
 679     BN_CTX *ctx = NULL;
 680
 681     if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
 682         ERR_raise(ERR_LIB_RSA, RSA_R_MODULUS_TOO_LARGE);
 683         return -1;
 684     }
 685
 686     if (BN_ucmp(rsa->n, rsa->e) <= 0) {
 687         ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
 688         return -1;
 689     }
 690
 691     /* for large moduli, enforce exponent limit */
 692     if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
 693         if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
 694             ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
 695             return -1;
 696         }
 697     }
 698
 699     if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
 700         goto err;
 701     BN_CTX_start(ctx);
 702     f = BN_CTX_get(ctx);
 703     ret = BN_CTX_get(ctx);
 704     if (ret == NULL) {
 705         ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
 706         goto err;
 707     }
 708     num = BN_num_bytes(rsa->n);
 709     buf = OPENSSL_malloc(num);
 710     if (buf == NULL)
 711         goto err;
 712
 713     /*
 714      * This check was for equality but PGP does evil things and chops off the
 715      * top '0' bytes
 716      */
 717     if (flen > num) {
 718         ERR_raise(ERR_LIB_RSA, RSA_R_DATA_GREATER_THAN_MOD_LEN);
 719         goto err;
 720     }
 721
 722     if (BN_bin2bn(from, flen, f) == NULL)
 723         goto err;
 724
 725     if (BN_ucmp(f, rsa->n) >= 0) {
 726         ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
 727         goto err;
 728     }
 729
 730     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 731         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 732                                     rsa->n, ctx))
 733             goto err;
 734
 735     if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
 736                                rsa->_method_mod_n))
 737         goto err;
 738
 739     /* For X9.31: Assuming e is odd it does a 12 mod 16 test */
 740     if ((padding == RSA_X931_PADDING) && ((bn_get_words(ret)[0] & 0xf) != 12))
 741         if (!BN_sub(ret, rsa->n, ret))
 742             goto err;
 743
 744     i = BN_bn2binpad(ret, buf, num);
 745     if (i < 0)
 746         goto err;
 747
 748     switch (padding) {
 749     case RSA_PKCS1_PADDING:
 750         r = RSA_padding_check_PKCS1_type_1(to, num, buf, i, num);
 751         break;
 752     case RSA_X931_PADDING:
 753         r = RSA_padding_check_X931(to, num, buf, i, num);
 754         break;
 755     case RSA_NO_PADDING:
 756         memcpy(to, buf, (r = i));
 757         break;
 758     default:
 759         ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
 760         goto err;
 761     }
 762     if (r < 0)
 763         ERR_raise(ERR_LIB_RSA, RSA_R_PADDING_CHECK_FAILED);
 764
 765  err:
 766     BN_CTX_end(ctx);
 767     BN_CTX_free(ctx);
 768     OPENSSL_clear_free(buf, num);
 769     return r;
 770 }
 771
 772 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
 773 {
 774     BIGNUM *r1, *m1, *vrfy;
 775     int ret = 0, smooth = 0;
 776 #ifndef FIPS_MODULE
 777     BIGNUM *r2, *m[RSA_MAX_PRIME_NUM - 2];
 778     int i, ex_primes = 0;
 779     RSA_PRIME_INFO *pinfo;
 780 #endif
 781
 782     BN_CTX_start(ctx);
 783
 784     r1 = BN_CTX_get(ctx);
 785 #ifndef FIPS_MODULE
 786     r2 = BN_CTX_get(ctx);
 787 #endif
 788     m1 = BN_CTX_get(ctx);
 789     vrfy = BN_CTX_get(ctx);
 790     if (vrfy == NULL)
 791         goto err;
 792
 793 #ifndef FIPS_MODULE
 794     if (rsa->version == RSA_ASN1_VERSION_MULTI
 795         && ((ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0
 796              || ex_primes > RSA_MAX_PRIME_NUM - 2))
 797         goto err;
 798 #endif
 799
 800     if (rsa->flags & RSA_FLAG_CACHE_PRIVATE) {
 801         BIGNUM *factor = BN_new();
 802
 803         if (factor == NULL)
 804             goto err;
 805
 806         /*
 807          * Make sure BN_mod_inverse in Montgomery initialization uses the
 808          * BN_FLG_CONSTTIME flag
 809          */
 810         if (!(BN_with_flags(factor, rsa->p, BN_FLG_CONSTTIME),
 811               BN_MONT_CTX_set_locked(&rsa->_method_mod_p, rsa->lock,
 812                                      factor, ctx))
 813             || !(BN_with_flags(factor, rsa->q, BN_FLG_CONSTTIME),
 814                  BN_MONT_CTX_set_locked(&rsa->_method_mod_q, rsa->lock,
 815                                         factor, ctx))) {
 816             BN_free(factor);
 817             goto err;
 818         }
 819 #ifndef FIPS_MODULE
 820         for (i = 0; i < ex_primes; i++) {
 821             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 822             BN_with_flags(factor, pinfo->r, BN_FLG_CONSTTIME);
 823             if (!BN_MONT_CTX_set_locked(&pinfo->m, rsa->lock, factor, ctx)) {
 824                 BN_free(factor);
 825                 goto err;
 826             }
 827         }
 828 #endif
 829         /*
 830          * We MUST free |factor| before any further use of the prime factors
 831          */
 832         BN_free(factor);
 833
 834         smooth = (rsa->meth->bn_mod_exp == BN_mod_exp_mont)
 835 #ifndef FIPS_MODULE
 836                  && (ex_primes == 0)
 837 #endif
 838                  && (BN_num_bits(rsa->q) == BN_num_bits(rsa->p));
 839     }
 840
 841     if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
 842         if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
 843                                     rsa->n, ctx))
 844             goto err;
 845
 846     if (smooth) {
 847         /*
 848          * Conversion from Montgomery domain, a.k.a. Montgomery reduction,
 849          * accepts values in [0-m*2^w) range. w is m's bit width rounded up
 850          * to limb width. So that at the very least if |I| is fully reduced,
 851          * i.e. less than p*q, we can count on from-to round to perform
 852          * below modulo operations on |I|. Unlike BN_mod it's constant time.
 853          */
 854         if (/* m1 = I moq q */
 855             !bn_from_mont_fixed_top(m1, I, rsa->_method_mod_q, ctx)
 856             || !bn_to_mont_fixed_top(m1, m1, rsa->_method_mod_q, ctx)
 857             /* r1 = I mod p */
 858             || !bn_from_mont_fixed_top(r1, I, rsa->_method_mod_p, ctx)
 859             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 860             /*
 861              * Use parallel exponentiations optimization if possible,
 862              * otherwise fallback to two sequential exponentiations:
 863              *    m1 = m1^dmq1 mod q
 864              *    r1 = r1^dmp1 mod p
 865              */
 866             || !BN_mod_exp_mont_consttime_x2(m1, m1, rsa->dmq1, rsa->q,
 867                                              rsa->_method_mod_q,
 868                                              r1, r1, rsa->dmp1, rsa->p,
 869                                              rsa->_method_mod_p,
 870                                              ctx)
 871             /* r1 = (r1 - m1) mod p */
 872             /*
 873              * bn_mod_sub_fixed_top is not regular modular subtraction,
 874              * it can tolerate subtrahend to be larger than modulus, but
 875              * not bit-wise wider. This makes up for uncommon q>p case,
 876              * when |m1| can be larger than |rsa->p|.
 877              */
 878             || !bn_mod_sub_fixed_top(r1, r1, m1, rsa->p)
 879
 880             /* r1 = r1 * iqmp mod p */
 881             || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
 882             || !bn_mul_mont_fixed_top(r1, r1, rsa->iqmp, rsa->_method_mod_p,
 883                                       ctx)
 884             /* r0 = r1 * q + m1 */
 885             || !bn_mul_fixed_top(r0, r1, rsa->q, ctx)
 886             || !bn_mod_add_fixed_top(r0, r0, m1, rsa->n))
 887             goto err;
 888
 889         goto tail;
 890     }
 891
 892     /* compute I mod q */
 893     {
 894         BIGNUM *c = BN_new();
 895         if (c == NULL)
 896             goto err;
 897         BN_with_flags(c, I, BN_FLG_CONSTTIME);
 898
 899         if (!BN_mod(r1, c, rsa->q, ctx)) {
 900             BN_free(c);
 901             goto err;
 902         }
 903
 904         {
 905             BIGNUM *dmq1 = BN_new();
 906             if (dmq1 == NULL) {
 907                 BN_free(c);
 908                 goto err;
 909             }
 910             BN_with_flags(dmq1, rsa->dmq1, BN_FLG_CONSTTIME);
 911
 912             /* compute r1^dmq1 mod q */
 913             if (!rsa->meth->bn_mod_exp(m1, r1, dmq1, rsa->q, ctx,
 914                                        rsa->_method_mod_q)) {
 915                 BN_free(c);
 916                 BN_free(dmq1);
 917                 goto err;
 918             }
 919             /* We MUST free dmq1 before any further use of rsa->dmq1 */
 920             BN_free(dmq1);
 921         }
 922
 923         /* compute I mod p */
 924         if (!BN_mod(r1, c, rsa->p, ctx)) {
 925             BN_free(c);
 926             goto err;
 927         }
 928         /* We MUST free c before any further use of I */
 929         BN_free(c);
 930     }
 931
 932     {
 933         BIGNUM *dmp1 = BN_new();
 934         if (dmp1 == NULL)
 935             goto err;
 936         BN_with_flags(dmp1, rsa->dmp1, BN_FLG_CONSTTIME);
 937
 938         /* compute r1^dmp1 mod p */
 939         if (!rsa->meth->bn_mod_exp(r0, r1, dmp1, rsa->p, ctx,
 940                                    rsa->_method_mod_p)) {
 941             BN_free(dmp1);
 942             goto err;
 943         }
 944         /* We MUST free dmp1 before any further use of rsa->dmp1 */
 945         BN_free(dmp1);
 946     }
 947
 948 #ifndef FIPS_MODULE
 949     if (ex_primes > 0) {
 950         BIGNUM *di = BN_new(), *cc = BN_new();
 951
 952         if (cc == NULL || di == NULL) {
 953             BN_free(cc);
 954             BN_free(di);
 955             goto err;
 956         }
 957
 958         for (i = 0; i < ex_primes; i++) {
 959             /* prepare m_i */
 960             if ((m[i] = BN_CTX_get(ctx)) == NULL) {
 961                 BN_free(cc);
 962                 BN_free(di);
 963                 goto err;
 964             }
 965
 966             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
 967
 968             /* prepare c and d_i */
 969             BN_with_flags(cc, I, BN_FLG_CONSTTIME);
 970             BN_with_flags(di, pinfo->d, BN_FLG_CONSTTIME);
 971
 972             if (!BN_mod(r1, cc, pinfo->r, ctx)) {
 973                 BN_free(cc);
 974                 BN_free(di);
 975                 goto err;
 976             }
 977             /* compute r1 ^ d_i mod r_i */
 978             if (!rsa->meth->bn_mod_exp(m[i], r1, di, pinfo->r, ctx, pinfo->m)) {
 979                 BN_free(cc);
 980                 BN_free(di);
 981                 goto err;
 982             }
 983         }
 984
 985         BN_free(cc);
 986         BN_free(di);
 987     }
 988 #endif
 989
 990     if (!BN_sub(r0, r0, m1))
 991         goto err;
 992     /*
 993      * This will help stop the size of r0 increasing, which does affect the
 994      * multiply if it optimised for a power of 2 size
 995      */
 996     if (BN_is_negative(r0))
 997         if (!BN_add(r0, r0, rsa->p))
 998             goto err;
 999
1000     if (!BN_mul(r1, r0, rsa->iqmp, ctx))
1001         goto err;
1002
1003     {
1004         BIGNUM *pr1 = BN_new();
1005         if (pr1 == NULL)
1006             goto err;
1007         BN_with_flags(pr1, r1, BN_FLG_CONSTTIME);
1008
1009         if (!BN_mod(r0, pr1, rsa->p, ctx)) {
1010             BN_free(pr1);
1011             goto err;
1012         }
1013         /* We MUST free pr1 before any further use of r1 */
1014         BN_free(pr1);
1015     }
1016
1017     /*
1018      * If p < q it is occasionally possible for the correction of adding 'p'
1019      * if r0 is negative above to leave the result still negative. This can
1020      * break the private key operations: the following second correction
1021      * should *always* correct this rare occurrence. This will *never* happen
1022      * with OpenSSL generated keys because they ensure p > q [steve]
1023      */
1024     if (BN_is_negative(r0))
1025         if (!BN_add(r0, r0, rsa->p))
1026             goto err;
1027     if (!BN_mul(r1, r0, rsa->q, ctx))
1028         goto err;
1029     if (!BN_add(r0, r1, m1))
1030         goto err;
1031
1032 #ifndef FIPS_MODULE
1033     /* add m_i to m in multi-prime case */
1034     if (ex_primes > 0) {
1035         BIGNUM *pr2 = BN_new();
1036
1037         if (pr2 == NULL)
1038             goto err;
1039
1040         for (i = 0; i < ex_primes; i++) {
1041             pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
1042             if (!BN_sub(r1, m[i], r0)) {
1043                 BN_free(pr2);
1044                 goto err;
1045             }
1046
1047             if (!BN_mul(r2, r1, pinfo->t, ctx)) {
1048                 BN_free(pr2);
1049                 goto err;
1050             }
1051
1052             BN_with_flags(pr2, r2, BN_FLG_CONSTTIME);
1053
1054             if (!BN_mod(r1, pr2, pinfo->r, ctx)) {
1055                 BN_free(pr2);
1056                 goto err;
1057             }
1058
1059             if (BN_is_negative(r1))
1060                 if (!BN_add(r1, r1, pinfo->r)) {
1061                     BN_free(pr2);
1062                     goto err;
1063                 }
1064             if (!BN_mul(r1, r1, pinfo->pp, ctx)) {
1065                 BN_free(pr2);
1066                 goto err;
1067             }
1068             if (!BN_add(r0, r0, r1)) {
1069                 BN_free(pr2);
1070                 goto err;
1071             }
1072         }
1073         BN_free(pr2);
1074     }
1075 #endif
1076
1077  tail:
1078     if (rsa->e && rsa->n) {
1079         if (rsa->meth->bn_mod_exp == BN_mod_exp_mont) {
1080             if (!BN_mod_exp_mont(vrfy, r0, rsa->e, rsa->n, ctx,
1081                                  rsa->_method_mod_n))
1082                 goto err;
1083         } else {
1084             bn_correct_top(r0);
1085             if (!rsa->meth->bn_mod_exp(vrfy, r0, rsa->e, rsa->n, ctx,
1086                                        rsa->_method_mod_n))
1087                 goto err;
1088         }
1089         /*
1090          * If 'I' was greater than (or equal to) rsa->n, the operation will
1091          * be equivalent to using 'I mod n'. However, the result of the
1092          * verify will *always* be less than 'n' so we don't check for
1093          * absolute equality, just congruency.
1094          */
1095         if (!BN_sub(vrfy, vrfy, I))
1096             goto err;
1097         if (BN_is_zero(vrfy)) {
1098             bn_correct_top(r0);
1099             ret = 1;
1100             goto err;   /* not actually error */
1101         }
1102         if (!BN_mod(vrfy, vrfy, rsa->n, ctx))
1103             goto err;
1104         if (BN_is_negative(vrfy))
1105             if (!BN_add(vrfy, vrfy, rsa->n))
1106                 goto err;
1107         if (!BN_is_zero(vrfy)) {
1108             /*
1109              * 'I' and 'vrfy' aren't congruent mod n. Don't leak
1110              * miscalculated CRT output, just do a raw (slower) mod_exp and
1111              * return that instead.
1112              */
1113
1114             BIGNUM *d = BN_new();
1115             if (d == NULL)
1116                 goto err;
1117             BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
1118
1119             if (!rsa->meth->bn_mod_exp(r0, I, d, rsa->n, ctx,
1120                                        rsa->_method_mod_n)) {
1121                 BN_free(d);
1122                 goto err;
1123             }
1124             /* We MUST free d before any further use of rsa->d */
1125             BN_free(d);
1126         }
1127     }
1128     /*
1129      * It's unfortunate that we have to bn_correct_top(r0). What hopefully
1130      * saves the day is that correction is highly unlike, and private key
1131      * operations are customarily performed on blinded message. Which means
1132      * that attacker won't observe correlation with chosen plaintext.
1133      * Secondly, remaining code would still handle it in same computational
1134      * time and even conceal memory access pattern around corrected top.
1135      */
1136     bn_correct_top(r0);
1137     ret = 1;
1138  err:
1139     BN_CTX_end(ctx);
1140     return ret;
1141 }
1142
1143 static int rsa_ossl_init(RSA *rsa)
1144 {
1145     rsa->flags |= RSA_FLAG_CACHE_PUBLIC | RSA_FLAG_CACHE_PRIVATE;
1146     return 1;
1147 }
1148
1149 static int rsa_ossl_finish(RSA *rsa)
1150 {
1151 #ifndef FIPS_MODULE
1152     int i;
1153     RSA_PRIME_INFO *pinfo;
1154
1155     for (i = 0; i < sk_RSA_PRIME_INFO_num(rsa->prime_infos); i++) {
1156         pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
1157         BN_MONT_CTX_free(pinfo->m);
1158     }
1159 #endif
1160
1161     BN_MONT_CTX_free(rsa->_method_mod_n);
1162     BN_MONT_CTX_free(rsa->_method_mod_p);
1163     BN_MONT_CTX_free(rsa->_method_mod_q);
1164     return 1;
1165 }
1166
1167 #ifdef S390X_MOD_EXP
1168 static int rsa_ossl_s390x_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
1169                                 BN_CTX *ctx)
1170 {
1171     if (rsa->version != RSA_ASN1_VERSION_MULTI) {
1172         if (s390x_crt(r0, i, rsa->p, rsa->q, rsa->dmp1, rsa->dmq1, rsa->iqmp) == 1)
1173             return 1;
1174     }
1175     return rsa_ossl_mod_exp(r0, i, rsa, ctx);
1176 }
1177
1178 #endif