2 * Copyright 1995-2022 The OpenSSL Project Authors. All Rights Reserved.
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
11 * RSA low level APIs are deprecated for public use, but still ok for
14 #include "internal/deprecated.h"
16 #include "internal/cryptlib.h"
17 #include "crypto/bn.h"
18 #include "rsa_local.h"
19 #include "internal/constant_time.h"
20 #include <openssl/evp.h>
21 #include <openssl/sha.h>
22 #include <openssl/hmac.h>
24 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
25 unsigned char *to, RSA *rsa, int padding);
26 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
27 unsigned char *to, RSA *rsa, int padding);
28 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
29 unsigned char *to, RSA *rsa, int padding);
30 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
31 unsigned char *to, RSA *rsa, int padding);
32 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
34 static int rsa_ossl_init(RSA *rsa);
35 static int rsa_ossl_finish(RSA *rsa);
37 static int rsa_ossl_s390x_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
39 static RSA_METHOD rsa_pkcs1_ossl_meth = {
41 rsa_ossl_public_encrypt,
42 rsa_ossl_public_decrypt, /* signature verification */
43 rsa_ossl_private_encrypt, /* signing */
44 rsa_ossl_private_decrypt,
45 rsa_ossl_s390x_mod_exp,
49 RSA_FLAG_FIPS_METHOD, /* flags */
53 NULL, /* rsa_keygen */
54 NULL /* rsa_multi_prime_keygen */
57 static RSA_METHOD rsa_pkcs1_ossl_meth = {
59 rsa_ossl_public_encrypt,
60 rsa_ossl_public_decrypt, /* signature verification */
61 rsa_ossl_private_encrypt, /* signing */
62 rsa_ossl_private_decrypt,
64 BN_mod_exp_mont, /* XXX probably we should not use Montgomery
68 RSA_FLAG_FIPS_METHOD, /* flags */
72 NULL, /* rsa_keygen */
73 NULL /* rsa_multi_prime_keygen */
77 static const RSA_METHOD *default_RSA_meth = &rsa_pkcs1_ossl_meth;
79 void RSA_set_default_method(const RSA_METHOD *meth)
81 default_RSA_meth = meth;
84 const RSA_METHOD *RSA_get_default_method(void)
86 return default_RSA_meth;
89 const RSA_METHOD *RSA_PKCS1_OpenSSL(void)
91 return &rsa_pkcs1_ossl_meth;
94 const RSA_METHOD *RSA_null_method(void)
99 static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
100 unsigned char *to, RSA *rsa, int padding)
103 int i, num = 0, r = -1;
104 unsigned char *buf = NULL;
107 if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
108 ERR_raise(ERR_LIB_RSA, RSA_R_MODULUS_TOO_LARGE);
112 if (BN_ucmp(rsa->n, rsa->e) <= 0) {
113 ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
117 /* for large moduli, enforce exponent limit */
118 if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
119 if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
120 ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
125 if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
129 ret = BN_CTX_get(ctx);
130 num = BN_num_bytes(rsa->n);
131 buf = OPENSSL_malloc(num);
132 if (ret == NULL || buf == NULL)
136 case RSA_PKCS1_PADDING:
137 i = ossl_rsa_padding_add_PKCS1_type_2_ex(rsa->libctx, buf, num,
140 case RSA_PKCS1_OAEP_PADDING:
141 i = ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(rsa->libctx, buf, num,
146 i = RSA_padding_add_none(buf, num, from, flen);
149 ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
155 if (BN_bin2bn(buf, num, f) == NULL)
158 if (BN_ucmp(f, rsa->n) >= 0) {
159 /* usually the padding functions would catch this */
160 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
164 if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
165 if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
169 if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
174 * BN_bn2binpad puts in leading 0 bytes if the number is less than
175 * the length of the modulus.
177 r = BN_bn2binpad(ret, to, num);
181 OPENSSL_clear_free(buf, num);
185 static BN_BLINDING *rsa_get_blinding(RSA *rsa, int *local, BN_CTX *ctx)
189 if (!CRYPTO_THREAD_write_lock(rsa->lock))
192 if (rsa->blinding == NULL) {
193 rsa->blinding = RSA_setup_blinding(rsa, ctx);
200 if (BN_BLINDING_is_current_thread(ret)) {
201 /* rsa->blinding is ours! */
205 /* resort to rsa->mt_blinding instead */
208 * instructs rsa_blinding_convert(), rsa_blinding_invert() that the
209 * BN_BLINDING is shared, meaning that accesses require locks, and
210 * that the blinding factor must be stored outside the BN_BLINDING
214 if (rsa->mt_blinding == NULL) {
215 rsa->mt_blinding = RSA_setup_blinding(rsa, ctx);
217 ret = rsa->mt_blinding;
221 CRYPTO_THREAD_unlock(rsa->lock);
225 static int rsa_blinding_convert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
228 if (unblind == NULL) {
230 * Local blinding: store the unblinding factor in BN_BLINDING.
232 return BN_BLINDING_convert_ex(f, NULL, b, ctx);
235 * Shared blinding: store the unblinding factor outside BN_BLINDING.
239 if (!BN_BLINDING_lock(b))
242 ret = BN_BLINDING_convert_ex(f, unblind, b, ctx);
243 BN_BLINDING_unlock(b);
249 static int rsa_blinding_invert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
253 * For local blinding, unblind is set to NULL, and BN_BLINDING_invert_ex
254 * will use the unblinding factor stored in BN_BLINDING. If BN_BLINDING
255 * is shared between threads, unblind must be non-null:
256 * BN_BLINDING_invert_ex will then use the local unblinding factor, and
257 * will only read the modulus from BN_BLINDING. In both cases it's safe
258 * to access the blinding without a lock.
260 BN_set_flags(f, BN_FLG_CONSTTIME);
261 return BN_BLINDING_invert_ex(f, unblind, b, ctx);
265 static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
266 unsigned char *to, RSA *rsa, int padding)
268 BIGNUM *f, *ret, *res;
269 int i, num = 0, r = -1;
270 unsigned char *buf = NULL;
272 int local_blinding = 0;
274 * Used only if the blinding structure is shared. A non-NULL unblind
275 * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
276 * the unblinding factor outside the blinding structure.
278 BIGNUM *unblind = NULL;
279 BN_BLINDING *blinding = NULL;
281 if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
285 ret = BN_CTX_get(ctx);
286 num = BN_num_bytes(rsa->n);
287 buf = OPENSSL_malloc(num);
288 if (ret == NULL || buf == NULL)
292 case RSA_PKCS1_PADDING:
293 i = RSA_padding_add_PKCS1_type_1(buf, num, from, flen);
295 case RSA_X931_PADDING:
296 i = RSA_padding_add_X931(buf, num, from, flen);
299 i = RSA_padding_add_none(buf, num, from, flen);
302 ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
308 if (BN_bin2bn(buf, num, f) == NULL)
311 if (BN_ucmp(f, rsa->n) >= 0) {
312 /* usually the padding functions would catch this */
313 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
317 if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
318 if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
322 if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
323 blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
324 if (blinding == NULL) {
325 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
330 if (blinding != NULL) {
331 if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
332 ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
335 if (!rsa_blinding_convert(blinding, f, unblind, ctx))
339 if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
340 (rsa->version == RSA_ASN1_VERSION_MULTI) ||
343 (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
344 if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
347 BIGNUM *d = BN_new();
349 ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
352 if (rsa->d == NULL) {
353 ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
357 BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
359 if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
360 rsa->_method_mod_n)) {
364 /* We MUST free d before any further use of rsa->d */
369 if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
372 if (padding == RSA_X931_PADDING) {
373 if (!BN_sub(f, rsa->n, ret))
375 if (BN_cmp(ret, f) > 0)
384 * BN_bn2binpad puts in leading 0 bytes if the number is less than
385 * the length of the modulus.
387 r = BN_bn2binpad(res, to, num);
391 OPENSSL_clear_free(buf, num);
395 static int derive_kdk(int flen, const unsigned char *from, RSA *rsa,
396 unsigned char *buf, int num, unsigned char *kdk)
399 HMAC_CTX *hmac = NULL;
401 unsigned int md_len = SHA256_DIGEST_LENGTH;
402 unsigned char d_hash[SHA256_DIGEST_LENGTH] = {0};
404 * because we use d as a handle to rsa->d we need to keep it local and
405 * free before any further use of rsa->d
407 BIGNUM *d = BN_new();
410 ERR_raise(ERR_LIB_RSA, ERR_R_CRYPTO_LIB);
413 if (rsa->d == NULL) {
414 ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
418 BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
419 if (BN_bn2binpad(d, buf, num) < 0) {
420 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
427 * we use hardcoded hash so that migrating between versions that use
428 * different hash doesn't provide a Bleichenbacher oracle:
429 * if the attacker can see that different versions return different
430 * messages for the same ciphertext, they'll know that the message is
431 * syntethically generated, which means that the padding check failed
433 md = EVP_MD_fetch(rsa->libctx, "sha256", NULL);
435 ERR_raise(ERR_LIB_RSA, ERR_R_FETCH_FAILED);
439 if (EVP_Digest(buf, num, d_hash, NULL, md, NULL) <= 0) {
440 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
444 hmac = HMAC_CTX_new();
446 ERR_raise(ERR_LIB_RSA, ERR_R_CRYPTO_LIB);
450 if (HMAC_Init_ex(hmac, d_hash, sizeof(d_hash), md, NULL) <= 0) {
451 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
456 memset(buf, 0, num - flen);
457 if (HMAC_Update(hmac, buf, num - flen) <= 0) {
458 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
462 if (HMAC_Update(hmac, from, flen) <= 0) {
463 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
467 md_len = SHA256_DIGEST_LENGTH;
468 if (HMAC_Final(hmac, kdk, &md_len) <= 0) {
469 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
480 static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
481 unsigned char *to, RSA *rsa, int padding)
484 int j, num = 0, r = -1;
485 unsigned char *buf = NULL;
486 unsigned char kdk[SHA256_DIGEST_LENGTH] = {0};
488 int local_blinding = 0;
490 * Used only if the blinding structure is shared. A non-NULL unblind
491 * instructs rsa_blinding_convert() and rsa_blinding_invert() to store
492 * the unblinding factor outside the blinding structure.
494 BIGNUM *unblind = NULL;
495 BN_BLINDING *blinding = NULL;
498 * we need the value of the private exponent to perform implicit rejection
500 if ((rsa->flags & RSA_FLAG_EXT_PKEY) && (padding == RSA_PKCS1_PADDING))
501 padding = RSA_PKCS1_NO_IMPLICIT_REJECT_PADDING;
503 if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
507 ret = BN_CTX_get(ctx);
509 ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
512 num = BN_num_bytes(rsa->n);
513 buf = OPENSSL_malloc(num);
518 * This check was for equality but PGP does evil things and chops off the
522 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_GREATER_THAN_MOD_LEN);
527 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_SMALL);
531 /* make data into a big number */
532 if (BN_bin2bn(from, (int)flen, f) == NULL)
535 if (BN_ucmp(f, rsa->n) >= 0) {
536 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
540 if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
541 if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
545 if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
546 blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
547 if (blinding == NULL) {
548 ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
553 if (blinding != NULL) {
554 if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
555 ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
558 if (!rsa_blinding_convert(blinding, f, unblind, ctx))
563 if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
564 (rsa->version == RSA_ASN1_VERSION_MULTI) ||
567 (rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
568 if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
571 BIGNUM *d = BN_new();
573 ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
576 if (rsa->d == NULL) {
577 ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
581 BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
582 if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
583 rsa->_method_mod_n)) {
587 /* We MUST free d before any further use of rsa->d */
592 if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
596 * derive the Key Derivation Key from private exponent and public
599 if (padding == RSA_PKCS1_PADDING) {
600 if (derive_kdk(flen, from, rsa, buf, num, kdk) == 0)
604 j = BN_bn2binpad(ret, buf, num);
609 case RSA_PKCS1_NO_IMPLICIT_REJECT_PADDING:
610 r = RSA_padding_check_PKCS1_type_2(to, num, buf, j, num);
612 case RSA_PKCS1_PADDING:
613 r = ossl_rsa_padding_check_PKCS1_type_2(rsa->libctx, to, num, buf, j, num, kdk);
615 case RSA_PKCS1_OAEP_PADDING:
616 r = RSA_padding_check_PKCS1_OAEP(to, num, buf, j, num, NULL, 0);
619 memcpy(to, buf, (r = j));
622 ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
627 * This trick doesn't work in the FIPS provider because libcrypto manages
628 * the error stack. Instead we opt not to put an error on the stack at all
629 * in case of padding failure in the FIPS provider.
631 ERR_raise(ERR_LIB_RSA, RSA_R_PADDING_CHECK_FAILED);
632 err_clear_last_constant_time(1 & ~constant_time_msb(r));
638 OPENSSL_clear_free(buf, num);
642 /* signature verification */
643 static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
644 unsigned char *to, RSA *rsa, int padding)
647 int i, num = 0, r = -1;
648 unsigned char *buf = NULL;
651 if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
652 ERR_raise(ERR_LIB_RSA, RSA_R_MODULUS_TOO_LARGE);
656 if (BN_ucmp(rsa->n, rsa->e) <= 0) {
657 ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
661 /* for large moduli, enforce exponent limit */
662 if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
663 if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
664 ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
669 if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
673 ret = BN_CTX_get(ctx);
675 ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
678 num = BN_num_bytes(rsa->n);
679 buf = OPENSSL_malloc(num);
684 * This check was for equality but PGP does evil things and chops off the
688 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_GREATER_THAN_MOD_LEN);
692 if (BN_bin2bn(from, flen, f) == NULL)
695 if (BN_ucmp(f, rsa->n) >= 0) {
696 ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
700 if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
701 if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
705 if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
709 if ((padding == RSA_X931_PADDING) && ((bn_get_words(ret)[0] & 0xf) != 12))
710 if (!BN_sub(ret, rsa->n, ret))
713 i = BN_bn2binpad(ret, buf, num);
718 case RSA_PKCS1_PADDING:
719 r = RSA_padding_check_PKCS1_type_1(to, num, buf, i, num);
721 case RSA_X931_PADDING:
722 r = RSA_padding_check_X931(to, num, buf, i, num);
725 memcpy(to, buf, (r = i));
728 ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
732 ERR_raise(ERR_LIB_RSA, RSA_R_PADDING_CHECK_FAILED);
737 OPENSSL_clear_free(buf, num);
741 static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
743 BIGNUM *r1, *m1, *vrfy;
744 int ret = 0, smooth = 0;
746 BIGNUM *r2, *m[RSA_MAX_PRIME_NUM - 2];
747 int i, ex_primes = 0;
748 RSA_PRIME_INFO *pinfo;
753 r1 = BN_CTX_get(ctx);
755 r2 = BN_CTX_get(ctx);
757 m1 = BN_CTX_get(ctx);
758 vrfy = BN_CTX_get(ctx);
763 if (rsa->version == RSA_ASN1_VERSION_MULTI
764 && ((ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0
765 || ex_primes > RSA_MAX_PRIME_NUM - 2))
769 if (rsa->flags & RSA_FLAG_CACHE_PRIVATE) {
770 BIGNUM *factor = BN_new();
776 * Make sure BN_mod_inverse in Montgomery initialization uses the
777 * BN_FLG_CONSTTIME flag
779 if (!(BN_with_flags(factor, rsa->p, BN_FLG_CONSTTIME),
780 BN_MONT_CTX_set_locked(&rsa->_method_mod_p, rsa->lock,
782 || !(BN_with_flags(factor, rsa->q, BN_FLG_CONSTTIME),
783 BN_MONT_CTX_set_locked(&rsa->_method_mod_q, rsa->lock,
789 for (i = 0; i < ex_primes; i++) {
790 pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
791 BN_with_flags(factor, pinfo->r, BN_FLG_CONSTTIME);
792 if (!BN_MONT_CTX_set_locked(&pinfo->m, rsa->lock, factor, ctx)) {
799 * We MUST free |factor| before any further use of the prime factors
803 smooth = (rsa->meth->bn_mod_exp == BN_mod_exp_mont)
807 && (BN_num_bits(rsa->q) == BN_num_bits(rsa->p));
810 if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
811 if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
817 * Conversion from Montgomery domain, a.k.a. Montgomery reduction,
818 * accepts values in [0-m*2^w) range. w is m's bit width rounded up
819 * to limb width. So that at the very least if |I| is fully reduced,
820 * i.e. less than p*q, we can count on from-to round to perform
821 * below modulo operations on |I|. Unlike BN_mod it's constant time.
823 if (/* m1 = I moq q */
824 !bn_from_mont_fixed_top(m1, I, rsa->_method_mod_q, ctx)
825 || !bn_to_mont_fixed_top(m1, m1, rsa->_method_mod_q, ctx)
827 || !bn_from_mont_fixed_top(r1, I, rsa->_method_mod_p, ctx)
828 || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
830 * Use parallel exponentiations optimization if possible,
831 * otherwise fallback to two sequential exponentiations:
835 || !BN_mod_exp_mont_consttime_x2(m1, m1, rsa->dmq1, rsa->q,
837 r1, r1, rsa->dmp1, rsa->p,
840 /* r1 = (r1 - m1) mod p */
842 * bn_mod_sub_fixed_top is not regular modular subtraction,
843 * it can tolerate subtrahend to be larger than modulus, but
844 * not bit-wise wider. This makes up for uncommon q>p case,
845 * when |m1| can be larger than |rsa->p|.
847 || !bn_mod_sub_fixed_top(r1, r1, m1, rsa->p)
849 /* r1 = r1 * iqmp mod p */
850 || !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
851 || !bn_mul_mont_fixed_top(r1, r1, rsa->iqmp, rsa->_method_mod_p,
853 /* r0 = r1 * q + m1 */
854 || !bn_mul_fixed_top(r0, r1, rsa->q, ctx)
855 || !bn_mod_add_fixed_top(r0, r0, m1, rsa->n))
861 /* compute I mod q */
863 BIGNUM *c = BN_new();
866 BN_with_flags(c, I, BN_FLG_CONSTTIME);
868 if (!BN_mod(r1, c, rsa->q, ctx)) {
874 BIGNUM *dmq1 = BN_new();
879 BN_with_flags(dmq1, rsa->dmq1, BN_FLG_CONSTTIME);
881 /* compute r1^dmq1 mod q */
882 if (!rsa->meth->bn_mod_exp(m1, r1, dmq1, rsa->q, ctx,
883 rsa->_method_mod_q)) {
888 /* We MUST free dmq1 before any further use of rsa->dmq1 */
892 /* compute I mod p */
893 if (!BN_mod(r1, c, rsa->p, ctx)) {
897 /* We MUST free c before any further use of I */
902 BIGNUM *dmp1 = BN_new();
905 BN_with_flags(dmp1, rsa->dmp1, BN_FLG_CONSTTIME);
907 /* compute r1^dmp1 mod p */
908 if (!rsa->meth->bn_mod_exp(r0, r1, dmp1, rsa->p, ctx,
909 rsa->_method_mod_p)) {
913 /* We MUST free dmp1 before any further use of rsa->dmp1 */
919 BIGNUM *di = BN_new(), *cc = BN_new();
921 if (cc == NULL || di == NULL) {
927 for (i = 0; i < ex_primes; i++) {
929 if ((m[i] = BN_CTX_get(ctx)) == NULL) {
935 pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
937 /* prepare c and d_i */
938 BN_with_flags(cc, I, BN_FLG_CONSTTIME);
939 BN_with_flags(di, pinfo->d, BN_FLG_CONSTTIME);
941 if (!BN_mod(r1, cc, pinfo->r, ctx)) {
946 /* compute r1 ^ d_i mod r_i */
947 if (!rsa->meth->bn_mod_exp(m[i], r1, di, pinfo->r, ctx, pinfo->m)) {
959 if (!BN_sub(r0, r0, m1))
962 * This will help stop the size of r0 increasing, which does affect the
963 * multiply if it optimised for a power of 2 size
965 if (BN_is_negative(r0))
966 if (!BN_add(r0, r0, rsa->p))
969 if (!BN_mul(r1, r0, rsa->iqmp, ctx))
973 BIGNUM *pr1 = BN_new();
976 BN_with_flags(pr1, r1, BN_FLG_CONSTTIME);
978 if (!BN_mod(r0, pr1, rsa->p, ctx)) {
982 /* We MUST free pr1 before any further use of r1 */
987 * If p < q it is occasionally possible for the correction of adding 'p'
988 * if r0 is negative above to leave the result still negative. This can
989 * break the private key operations: the following second correction
990 * should *always* correct this rare occurrence. This will *never* happen
991 * with OpenSSL generated keys because they ensure p > q [steve]
993 if (BN_is_negative(r0))
994 if (!BN_add(r0, r0, rsa->p))
996 if (!BN_mul(r1, r0, rsa->q, ctx))
998 if (!BN_add(r0, r1, m1))
1002 /* add m_i to m in multi-prime case */
1003 if (ex_primes > 0) {
1004 BIGNUM *pr2 = BN_new();
1009 for (i = 0; i < ex_primes; i++) {
1010 pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
1011 if (!BN_sub(r1, m[i], r0)) {
1016 if (!BN_mul(r2, r1, pinfo->t, ctx)) {
1021 BN_with_flags(pr2, r2, BN_FLG_CONSTTIME);
1023 if (!BN_mod(r1, pr2, pinfo->r, ctx)) {
1028 if (BN_is_negative(r1))
1029 if (!BN_add(r1, r1, pinfo->r)) {
1033 if (!BN_mul(r1, r1, pinfo->pp, ctx)) {
1037 if (!BN_add(r0, r0, r1)) {
1047 if (rsa->e && rsa->n) {
1048 if (rsa->meth->bn_mod_exp == BN_mod_exp_mont) {
1049 if (!BN_mod_exp_mont(vrfy, r0, rsa->e, rsa->n, ctx,
1050 rsa->_method_mod_n))
1054 if (!rsa->meth->bn_mod_exp(vrfy, r0, rsa->e, rsa->n, ctx,
1055 rsa->_method_mod_n))
1059 * If 'I' was greater than (or equal to) rsa->n, the operation will
1060 * be equivalent to using 'I mod n'. However, the result of the
1061 * verify will *always* be less than 'n' so we don't check for
1062 * absolute equality, just congruency.
1064 if (!BN_sub(vrfy, vrfy, I))
1066 if (BN_is_zero(vrfy)) {
1069 goto err; /* not actually error */
1071 if (!BN_mod(vrfy, vrfy, rsa->n, ctx))
1073 if (BN_is_negative(vrfy))
1074 if (!BN_add(vrfy, vrfy, rsa->n))
1076 if (!BN_is_zero(vrfy)) {
1078 * 'I' and 'vrfy' aren't congruent mod n. Don't leak
1079 * miscalculated CRT output, just do a raw (slower) mod_exp and
1080 * return that instead.
1083 BIGNUM *d = BN_new();
1086 BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
1088 if (!rsa->meth->bn_mod_exp(r0, I, d, rsa->n, ctx,
1089 rsa->_method_mod_n)) {
1093 /* We MUST free d before any further use of rsa->d */
1098 * It's unfortunate that we have to bn_correct_top(r0). What hopefully
1099 * saves the day is that correction is highly unlike, and private key
1100 * operations are customarily performed on blinded message. Which means
1101 * that attacker won't observe correlation with chosen plaintext.
1102 * Secondly, remaining code would still handle it in same computational
1103 * time and even conceal memory access pattern around corrected top.
1112 static int rsa_ossl_init(RSA *rsa)
1114 rsa->flags |= RSA_FLAG_CACHE_PUBLIC | RSA_FLAG_CACHE_PRIVATE;
1118 static int rsa_ossl_finish(RSA *rsa)
1122 RSA_PRIME_INFO *pinfo;
1124 for (i = 0; i < sk_RSA_PRIME_INFO_num(rsa->prime_infos); i++) {
1125 pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
1126 BN_MONT_CTX_free(pinfo->m);
1130 BN_MONT_CTX_free(rsa->_method_mod_n);
1131 BN_MONT_CTX_free(rsa->_method_mod_p);
1132 BN_MONT_CTX_free(rsa->_method_mod_q);
1136 #ifdef S390X_MOD_EXP
1137 static int rsa_ossl_s390x_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
1140 if (rsa->version != RSA_ASN1_VERSION_MULTI) {
1141 if (s390x_crt(r0, i, rsa->p, rsa->q, rsa->dmp1, rsa->dmq1, rsa->iqmp) == 1)
1144 return rsa_ossl_mod_exp(r0, i, rsa, ctx);