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openssl/crypto/rsa/rsa_ossl.c
Andy Polyakov a9e4192e71 rsa/rsa_ossl.c: fix and extend commentary [skip ci]. 
Reviewed-by: Richard Levitte <levitte@openssl.org>
Reviewed-by: Nicola Tuveri <nic.tuv@gmail.com>
(Merged from https://github.com/openssl/openssl/pull/7123)

(cherry picked from commit d1c008f66b)
2018-10-12 22:28:52 +02:00

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/*
* Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "internal/cryptlib.h"
#include "internal/bn_int.h"
#include "rsa_locl.h"
static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding);
static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
BN_CTX *ctx);
static int rsa_ossl_init(RSA *rsa);
static int rsa_ossl_finish(RSA *rsa);
static RSA_METHOD rsa_pkcs1_ossl_meth = {
"OpenSSL PKCS#1 RSA",
rsa_ossl_public_encrypt,
rsa_ossl_public_decrypt, /* signature verification */
rsa_ossl_private_encrypt, /* signing */
rsa_ossl_private_decrypt,
rsa_ossl_mod_exp,
BN_mod_exp_mont, /* XXX probably we should not use Montgomery
* if e == 3 */
rsa_ossl_init,
rsa_ossl_finish,
RSA_FLAG_FIPS_METHOD, /* flags */
NULL,
0, /* rsa_sign */
0, /* rsa_verify */
NULL, /* rsa_keygen */
NULL /* rsa_multi_prime_keygen */
};
static const RSA_METHOD *default_RSA_meth = &rsa_pkcs1_ossl_meth;
void RSA_set_default_method(const RSA_METHOD *meth)
{
default_RSA_meth = meth;
}
const RSA_METHOD *RSA_get_default_method(void)
{
return default_RSA_meth;
}
const RSA_METHOD *RSA_PKCS1_OpenSSL(void)
{
return &rsa_pkcs1_ossl_meth;
}
const RSA_METHOD *RSA_null_method(void)
{
return NULL;
}
static int rsa_ossl_public_encrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding)
{
BIGNUM *f, *ret;
int i, num = 0, r = -1;
unsigned char *buf = NULL;
BN_CTX *ctx = NULL;
if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_MODULUS_TOO_LARGE);
return -1;
}
if (BN_ucmp(rsa->n, rsa->e) <= 0) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
return -1;
}
/* for large moduli, enforce exponent limit */
if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_BAD_E_VALUE);
return -1;
}
}
if ((ctx = BN_CTX_new()) == NULL)
goto err;
BN_CTX_start(ctx);
f = BN_CTX_get(ctx);
ret = BN_CTX_get(ctx);
num = BN_num_bytes(rsa->n);
buf = OPENSSL_malloc(num);
if (ret == NULL || buf == NULL) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
switch (padding) {
case RSA_PKCS1_PADDING:
i = RSA_padding_add_PKCS1_type_2(buf, num, from, flen);
break;
case RSA_PKCS1_OAEP_PADDING:
i = RSA_padding_add_PKCS1_OAEP(buf, num, from, flen, NULL, 0);
break;
case RSA_SSLV23_PADDING:
i = RSA_padding_add_SSLv23(buf, num, from, flen);
break;
case RSA_NO_PADDING:
i = RSA_padding_add_none(buf, num, from, flen);
break;
default:
RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
goto err;
}
if (i <= 0)
goto err;
if (BN_bin2bn(buf, num, f) == NULL)
goto err;
if (BN_ucmp(f, rsa->n) >= 0) {
/* usually the padding functions would catch this */
RSAerr(RSA_F_RSA_OSSL_PUBLIC_ENCRYPT,
RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
goto err;
}
if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
rsa->n, ctx))
goto err;
if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
rsa->_method_mod_n))
goto err;
/*
* BN_bn2binpad puts in leading 0 bytes if the number is less than
* the length of the modulus.
*/
r = BN_bn2binpad(ret, to, num);
err:
if (ctx != NULL)
BN_CTX_end(ctx);
BN_CTX_free(ctx);
OPENSSL_clear_free(buf, num);
return r;
}
static BN_BLINDING *rsa_get_blinding(RSA *rsa, int *local, BN_CTX *ctx)
{
BN_BLINDING *ret;
CRYPTO_THREAD_write_lock(rsa->lock);
if (rsa->blinding == NULL) {
rsa->blinding = RSA_setup_blinding(rsa, ctx);
}
ret = rsa->blinding;
if (ret == NULL)
goto err;
if (BN_BLINDING_is_current_thread(ret)) {
/* rsa->blinding is ours! */
*local = 1;
} else {
/* resort to rsa->mt_blinding instead */
/*
* instructs rsa_blinding_convert(), rsa_blinding_invert() that the
* BN_BLINDING is shared, meaning that accesses require locks, and
* that the blinding factor must be stored outside the BN_BLINDING
*/
*local = 0;
if (rsa->mt_blinding == NULL) {
rsa->mt_blinding = RSA_setup_blinding(rsa, ctx);
}
ret = rsa->mt_blinding;
}
err:
CRYPTO_THREAD_unlock(rsa->lock);
return ret;
}
static int rsa_blinding_convert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
BN_CTX *ctx)
{
if (unblind == NULL) {
/*
* Local blinding: store the unblinding factor in BN_BLINDING.
*/
return BN_BLINDING_convert_ex(f, NULL, b, ctx);
} else {
/*
* Shared blinding: store the unblinding factor outside BN_BLINDING.
*/
int ret;
BN_BLINDING_lock(b);
ret = BN_BLINDING_convert_ex(f, unblind, b, ctx);
BN_BLINDING_unlock(b);
return ret;
}
}
static int rsa_blinding_invert(BN_BLINDING *b, BIGNUM *f, BIGNUM *unblind,
BN_CTX *ctx)
{
/*
* For local blinding, unblind is set to NULL, and BN_BLINDING_invert_ex
* will use the unblinding factor stored in BN_BLINDING. If BN_BLINDING
* is shared between threads, unblind must be non-null:
* BN_BLINDING_invert_ex will then use the local unblinding factor, and
* will only read the modulus from BN_BLINDING. In both cases it's safe
* to access the blinding without a lock.
*/
return BN_BLINDING_invert_ex(f, unblind, b, ctx);
}
/* signing */
static int rsa_ossl_private_encrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding)
{
BIGNUM *f, *ret, *res;
int i, num = 0, r = -1;
unsigned char *buf = NULL;
BN_CTX *ctx = NULL;
int local_blinding = 0;
/*
* Used only if the blinding structure is shared. A non-NULL unblind
* instructs rsa_blinding_convert() and rsa_blinding_invert() to store
* the unblinding factor outside the blinding structure.
*/
BIGNUM *unblind = NULL;
BN_BLINDING *blinding = NULL;
if ((ctx = BN_CTX_new()) == NULL)
goto err;
BN_CTX_start(ctx);
f = BN_CTX_get(ctx);
ret = BN_CTX_get(ctx);
num = BN_num_bytes(rsa->n);
buf = OPENSSL_malloc(num);
if (ret == NULL || buf == NULL) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
switch (padding) {
case RSA_PKCS1_PADDING:
i = RSA_padding_add_PKCS1_type_1(buf, num, from, flen);
break;
case RSA_X931_PADDING:
i = RSA_padding_add_X931(buf, num, from, flen);
break;
case RSA_NO_PADDING:
i = RSA_padding_add_none(buf, num, from, flen);
break;
case RSA_SSLV23_PADDING:
default:
RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
goto err;
}
if (i <= 0)
goto err;
if (BN_bin2bn(buf, num, f) == NULL)
goto err;
if (BN_ucmp(f, rsa->n) >= 0) {
/* usually the padding functions would catch this */
RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT,
RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
goto err;
}
if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
if (blinding == NULL) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (blinding != NULL) {
if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
if (!rsa_blinding_convert(blinding, f, unblind, ctx))
goto err;
}
if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
(rsa->version == RSA_ASN1_VERSION_MULTI) ||
((rsa->p != NULL) &&
(rsa->q != NULL) &&
(rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
goto err;
} else {
BIGNUM *d = BN_new();
if (d == NULL) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_ENCRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
rsa->n, ctx)) {
BN_free(d);
goto err;
}
if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
rsa->_method_mod_n)) {
BN_free(d);
goto err;
}
/* We MUST free d before any further use of rsa->d */
BN_free(d);
}
if (blinding)
if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
goto err;
if (padding == RSA_X931_PADDING) {
if (!BN_sub(f, rsa->n, ret))
goto err;
if (BN_cmp(ret, f) > 0)
res = f;
else
res = ret;
} else {
res = ret;
}
/*
* BN_bn2binpad puts in leading 0 bytes if the number is less than
* the length of the modulus.
*/
r = BN_bn2binpad(res, to, num);
err:
if (ctx != NULL)
BN_CTX_end(ctx);
BN_CTX_free(ctx);
OPENSSL_clear_free(buf, num);
return r;
}
static int rsa_ossl_private_decrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding)
{
BIGNUM *f, *ret;
int j, num = 0, r = -1;
unsigned char *buf = NULL;
BN_CTX *ctx = NULL;
int local_blinding = 0;
/*
* Used only if the blinding structure is shared. A non-NULL unblind
* instructs rsa_blinding_convert() and rsa_blinding_invert() to store
* the unblinding factor outside the blinding structure.
*/
BIGNUM *unblind = NULL;
BN_BLINDING *blinding = NULL;
if ((ctx = BN_CTX_new()) == NULL)
goto err;
BN_CTX_start(ctx);
f = BN_CTX_get(ctx);
ret = BN_CTX_get(ctx);
num = BN_num_bytes(rsa->n);
buf = OPENSSL_malloc(num);
if (ret == NULL || buf == NULL) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
/*
* This check was for equality but PGP does evil things and chops off the
* top '0' bytes
*/
if (flen > num) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
RSA_R_DATA_GREATER_THAN_MOD_LEN);
goto err;
}
/* make data into a big number */
if (BN_bin2bn(from, (int)flen, f) == NULL)
goto err;
if (BN_ucmp(f, rsa->n) >= 0) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT,
RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
goto err;
}
if (!(rsa->flags & RSA_FLAG_NO_BLINDING)) {
blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
if (blinding == NULL) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (blinding != NULL) {
if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
if (!rsa_blinding_convert(blinding, f, unblind, ctx))
goto err;
}
/* do the decrypt */
if ((rsa->flags & RSA_FLAG_EXT_PKEY) ||
(rsa->version == RSA_ASN1_VERSION_MULTI) ||
((rsa->p != NULL) &&
(rsa->q != NULL) &&
(rsa->dmp1 != NULL) && (rsa->dmq1 != NULL) && (rsa->iqmp != NULL))) {
if (!rsa->meth->rsa_mod_exp(ret, f, rsa, ctx))
goto err;
} else {
BIGNUM *d = BN_new();
if (d == NULL) {
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
rsa->n, ctx)) {
BN_free(d);
goto err;
}
if (!rsa->meth->bn_mod_exp(ret, f, d, rsa->n, ctx,
rsa->_method_mod_n)) {
BN_free(d);
goto err;
}
/* We MUST free d before any further use of rsa->d */
BN_free(d);
}
if (blinding)
if (!rsa_blinding_invert(blinding, ret, unblind, ctx))
goto err;
j = BN_bn2binpad(ret, buf, num);
switch (padding) {
case RSA_PKCS1_PADDING:
r = RSA_padding_check_PKCS1_type_2(to, num, buf, j, num);
break;
case RSA_PKCS1_OAEP_PADDING:
r = RSA_padding_check_PKCS1_OAEP(to, num, buf, j, num, NULL, 0);
break;
case RSA_SSLV23_PADDING:
r = RSA_padding_check_SSLv23(to, num, buf, j, num);
break;
case RSA_NO_PADDING:
memcpy(to, buf, (r = j));
break;
default:
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
goto err;
}
if (r < 0)
RSAerr(RSA_F_RSA_OSSL_PRIVATE_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
err:
if (ctx != NULL)
BN_CTX_end(ctx);
BN_CTX_free(ctx);
OPENSSL_clear_free(buf, num);
return r;
}
/* signature verification */
static int rsa_ossl_public_decrypt(int flen, const unsigned char *from,
unsigned char *to, RSA *rsa, int padding)
{
BIGNUM *f, *ret;
int i, num = 0, r = -1;
unsigned char *buf = NULL;
BN_CTX *ctx = NULL;
if (BN_num_bits(rsa->n) > OPENSSL_RSA_MAX_MODULUS_BITS) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_MODULUS_TOO_LARGE);
return -1;
}
if (BN_ucmp(rsa->n, rsa->e) <= 0) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
return -1;
}
/* for large moduli, enforce exponent limit */
if (BN_num_bits(rsa->n) > OPENSSL_RSA_SMALL_MODULUS_BITS) {
if (BN_num_bits(rsa->e) > OPENSSL_RSA_MAX_PUBEXP_BITS) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_BAD_E_VALUE);
return -1;
}
}
if ((ctx = BN_CTX_new()) == NULL)
goto err;
BN_CTX_start(ctx);
f = BN_CTX_get(ctx);
ret = BN_CTX_get(ctx);
num = BN_num_bytes(rsa->n);
buf = OPENSSL_malloc(num);
if (ret == NULL || buf == NULL) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, ERR_R_MALLOC_FAILURE);
goto err;
}
/*
* This check was for equality but PGP does evil things and chops off the
* top '0' bytes
*/
if (flen > num) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_DATA_GREATER_THAN_MOD_LEN);
goto err;
}
if (BN_bin2bn(from, flen, f) == NULL)
goto err;
if (BN_ucmp(f, rsa->n) >= 0) {
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT,
RSA_R_DATA_TOO_LARGE_FOR_MODULUS);
goto err;
}
if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
rsa->n, ctx))
goto err;
if (!rsa->meth->bn_mod_exp(ret, f, rsa->e, rsa->n, ctx,
rsa->_method_mod_n))
goto err;
if ((padding == RSA_X931_PADDING) && ((bn_get_words(ret)[0] & 0xf) != 12))
if (!BN_sub(ret, rsa->n, ret))
goto err;
i = BN_bn2binpad(ret, buf, num);
switch (padding) {
case RSA_PKCS1_PADDING:
r = RSA_padding_check_PKCS1_type_1(to, num, buf, i, num);
break;
case RSA_X931_PADDING:
r = RSA_padding_check_X931(to, num, buf, i, num);
break;
case RSA_NO_PADDING:
memcpy(to, buf, (r = i));
break;
default:
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_UNKNOWN_PADDING_TYPE);
goto err;
}
if (r < 0)
RSAerr(RSA_F_RSA_OSSL_PUBLIC_DECRYPT, RSA_R_PADDING_CHECK_FAILED);
err:
if (ctx != NULL)
BN_CTX_end(ctx);
BN_CTX_free(ctx);
OPENSSL_clear_free(buf, num);
return r;
}
static int rsa_ossl_mod_exp(BIGNUM *r0, const BIGNUM *I, RSA *rsa, BN_CTX *ctx)
{
BIGNUM *r1, *m1, *vrfy, *r2, *m[RSA_MAX_PRIME_NUM - 2];
int ret = 0, i, ex_primes = 0, smooth = 0;
RSA_PRIME_INFO *pinfo;
BN_CTX_start(ctx);
r1 = BN_CTX_get(ctx);
r2 = BN_CTX_get(ctx);
m1 = BN_CTX_get(ctx);
vrfy = BN_CTX_get(ctx);
if (vrfy == NULL)
goto err;
if (rsa->version == RSA_ASN1_VERSION_MULTI
&& ((ex_primes = sk_RSA_PRIME_INFO_num(rsa->prime_infos)) <= 0
|| ex_primes > RSA_MAX_PRIME_NUM - 2))
goto err;
if (rsa->flags & RSA_FLAG_CACHE_PRIVATE) {
BIGNUM *factor = BN_new();
if (factor == NULL)
goto err;
/*
* Make sure BN_mod_inverse in Montgomery initialization uses the
* BN_FLG_CONSTTIME flag
*/
if (!(BN_with_flags(factor, rsa->p, BN_FLG_CONSTTIME),
BN_MONT_CTX_set_locked(&rsa->_method_mod_p, rsa->lock,
factor, ctx))
|| !(BN_with_flags(factor, rsa->q, BN_FLG_CONSTTIME),
BN_MONT_CTX_set_locked(&rsa->_method_mod_q, rsa->lock,
factor, ctx))) {
BN_free(factor);
goto err;
}
for (i = 0; i < ex_primes; i++) {
pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
BN_with_flags(factor, pinfo->r, BN_FLG_CONSTTIME);
if (!BN_MONT_CTX_set_locked(&pinfo->m, rsa->lock, factor, ctx)) {
BN_free(factor);
goto err;
}
}
/*
* We MUST free |factor| before any further use of the prime factors
*/
BN_free(factor);
smooth = (ex_primes == 0)
&& (rsa->meth->bn_mod_exp == BN_mod_exp_mont)
&& (BN_num_bits(rsa->q) == BN_num_bits(rsa->p));
}
if (rsa->flags & RSA_FLAG_CACHE_PUBLIC)
if (!BN_MONT_CTX_set_locked(&rsa->_method_mod_n, rsa->lock,
rsa->n, ctx))
goto err;
if (smooth) {
/*
* Conversion from Montgomery domain, a.k.a. Montgomery reduction,
* accepts values in [0-m*2^w) range. w is m's bit width rounded up
* to limb width. So that at the very least if |I| is fully reduced,
* i.e. less than p*q, we can count on from-to round to perform
* below modulo operations on |I|. Unlike BN_mod it's constant time.
*/
if (/* m1 = I moq q */
!bn_from_mont_fixed_top(m1, I, rsa->_method_mod_q, ctx)
|| !bn_to_mont_fixed_top(m1, m1, rsa->_method_mod_q, ctx)
/* m1 = m1^dmq1 mod q */
|| !BN_mod_exp_mont_consttime(m1, m1, rsa->dmq1, rsa->q, ctx,
rsa->_method_mod_q)
/* r1 = I mod p */
|| !bn_from_mont_fixed_top(r1, I, rsa->_method_mod_p, ctx)
|| !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
/* r1 = r1^dmp1 mod p */
|| !BN_mod_exp_mont_consttime(r1, r1, rsa->dmp1, rsa->p, ctx,
rsa->_method_mod_p)
/* r1 = (r1 - m1) mod p */
/*
* bn_mod_sub_fixed_top is not regular modular subtraction,
* it can tolerate subtrahend to be larger than modulus, but
* not bit-wise wider. This makes up for uncommon q>p case,
* when |m1| can be larger than |rsa->p|.
*/
|| !bn_mod_sub_fixed_top(r1, r1, m1, rsa->p)
/* r1 = r1 * iqmp mod p */
|| !bn_to_mont_fixed_top(r1, r1, rsa->_method_mod_p, ctx)
|| !bn_mul_mont_fixed_top(r1, r1, rsa->iqmp, rsa->_method_mod_p,
ctx)
/* r0 = r1 * q + m1 */
|| !bn_mul_fixed_top(r0, r1, rsa->q, ctx)
|| !bn_mod_add_fixed_top(r0, r0, m1, rsa->n))
goto err;
goto tail;
}
/* compute I mod q */
{
BIGNUM *c = BN_new();
if (c == NULL)
goto err;
BN_with_flags(c, I, BN_FLG_CONSTTIME);
if (!BN_mod(r1, c, rsa->q, ctx)) {
BN_free(c);
goto err;
}
{
BIGNUM *dmq1 = BN_new();
if (dmq1 == NULL) {
BN_free(c);
goto err;
}
BN_with_flags(dmq1, rsa->dmq1, BN_FLG_CONSTTIME);
/* compute r1^dmq1 mod q */
if (!rsa->meth->bn_mod_exp(m1, r1, dmq1, rsa->q, ctx,
rsa->_method_mod_q)) {
BN_free(c);
BN_free(dmq1);
goto err;
}
/* We MUST free dmq1 before any further use of rsa->dmq1 */
BN_free(dmq1);
}
/* compute I mod p */
if (!BN_mod(r1, c, rsa->p, ctx)) {
BN_free(c);
goto err;
}
/* We MUST free c before any further use of I */
BN_free(c);
}
{
BIGNUM *dmp1 = BN_new();
if (dmp1 == NULL)
goto err;
BN_with_flags(dmp1, rsa->dmp1, BN_FLG_CONSTTIME);
/* compute r1^dmp1 mod p */
if (!rsa->meth->bn_mod_exp(r0, r1, dmp1, rsa->p, ctx,
rsa->_method_mod_p)) {
BN_free(dmp1);
goto err;
}
/* We MUST free dmp1 before any further use of rsa->dmp1 */
BN_free(dmp1);
}
/*
* calculate m_i in multi-prime case
*
* TODO:
* 1. squash the following two loops and calculate |m_i| there.
* 2. remove cc and reuse |c|.
* 3. remove |dmq1| and |dmp1| in previous block and use |di|.
*
* If these things are done, the code will be more readable.
*/
if (ex_primes > 0) {
BIGNUM *di = BN_new(), *cc = BN_new();
if (cc == NULL || di == NULL) {
BN_free(cc);
BN_free(di);
goto err;
}
for (i = 0; i < ex_primes; i++) {
/* prepare m_i */
if ((m[i] = BN_CTX_get(ctx)) == NULL) {
BN_free(cc);
BN_free(di);
goto err;
}
pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
/* prepare c and d_i */
BN_with_flags(cc, I, BN_FLG_CONSTTIME);
BN_with_flags(di, pinfo->d, BN_FLG_CONSTTIME);
if (!BN_mod(r1, cc, pinfo->r, ctx)) {
BN_free(cc);
BN_free(di);
goto err;
}
/* compute r1 ^ d_i mod r_i */
if (!rsa->meth->bn_mod_exp(m[i], r1, di, pinfo->r, ctx, pinfo->m)) {
BN_free(cc);
BN_free(di);
goto err;
}
}
BN_free(cc);
BN_free(di);
}
if (!BN_sub(r0, r0, m1))
goto err;
/*
* This will help stop the size of r0 increasing, which does affect the
* multiply if it optimised for a power of 2 size
*/
if (BN_is_negative(r0))
if (!BN_add(r0, r0, rsa->p))
goto err;
if (!BN_mul(r1, r0, rsa->iqmp, ctx))
goto err;
{
BIGNUM *pr1 = BN_new();
if (pr1 == NULL)
goto err;
BN_with_flags(pr1, r1, BN_FLG_CONSTTIME);
if (!BN_mod(r0, pr1, rsa->p, ctx)) {
BN_free(pr1);
goto err;
}
/* We MUST free pr1 before any further use of r1 */
BN_free(pr1);
}
/*
* If p < q it is occasionally possible for the correction of adding 'p'
* if r0 is negative above to leave the result still negative. This can
* break the private key operations: the following second correction
* should *always* correct this rare occurrence. This will *never* happen
* with OpenSSL generated keys because they ensure p > q [steve]
*/
if (BN_is_negative(r0))
if (!BN_add(r0, r0, rsa->p))
goto err;
if (!BN_mul(r1, r0, rsa->q, ctx))
goto err;
if (!BN_add(r0, r1, m1))
goto err;
/* add m_i to m in multi-prime case */
if (ex_primes > 0) {
BIGNUM *pr2 = BN_new();
if (pr2 == NULL)
goto err;
for (i = 0; i < ex_primes; i++) {
pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
if (!BN_sub(r1, m[i], r0)) {
BN_free(pr2);
goto err;
}
if (!BN_mul(r2, r1, pinfo->t, ctx)) {
BN_free(pr2);
goto err;
}
BN_with_flags(pr2, r2, BN_FLG_CONSTTIME);
if (!BN_mod(r1, pr2, pinfo->r, ctx)) {
BN_free(pr2);
goto err;
}
if (BN_is_negative(r1))
if (!BN_add(r1, r1, pinfo->r)) {
BN_free(pr2);
goto err;
}
if (!BN_mul(r1, r1, pinfo->pp, ctx)) {
BN_free(pr2);
goto err;
}
if (!BN_add(r0, r0, r1)) {
BN_free(pr2);
goto err;
}
}
BN_free(pr2);
}
tail:
if (rsa->e && rsa->n) {
if (rsa->meth->bn_mod_exp == BN_mod_exp_mont) {
if (!BN_mod_exp_mont(vrfy, r0, rsa->e, rsa->n, ctx,
rsa->_method_mod_n))
goto err;
} else {
bn_correct_top(r0);
if (!rsa->meth->bn_mod_exp(vrfy, r0, rsa->e, rsa->n, ctx,
rsa->_method_mod_n))
goto err;
}
/*
* If 'I' was greater than (or equal to) rsa->n, the operation will
* be equivalent to using 'I mod n'. However, the result of the
* verify will *always* be less than 'n' so we don't check for
* absolute equality, just congruency.
*/
if (!BN_sub(vrfy, vrfy, I))
goto err;
if (BN_is_zero(vrfy)) {
bn_correct_top(r0);
ret = 1;
goto err; /* not actually error */
}
if (!BN_mod(vrfy, vrfy, rsa->n, ctx))
goto err;
if (BN_is_negative(vrfy))
if (!BN_add(vrfy, vrfy, rsa->n))
goto err;
if (!BN_is_zero(vrfy)) {
/*
* 'I' and 'vrfy' aren't congruent mod n. Don't leak
* miscalculated CRT output, just do a raw (slower) mod_exp and
* return that instead.
*/
BIGNUM *d = BN_new();
if (d == NULL)
goto err;
BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
if (!rsa->meth->bn_mod_exp(r0, I, d, rsa->n, ctx,
rsa->_method_mod_n)) {
BN_free(d);
goto err;
}
/* We MUST free d before any further use of rsa->d */
BN_free(d);
}
}
/*
* It's unfortunate that we have to bn_correct_top(r0). What hopefully
* saves the day is that correction is highly unlike, and private key
* operations are customarily performed on blinded message. Which means
* that attacker won't observe correlation with chosen plaintext.
* Secondly, remaining code would still handle it in same computational
* time and even conceal memory access pattern around corrected top.
*/
bn_correct_top(r0);
ret = 1;
err:
BN_CTX_end(ctx);
return ret;
}
static int rsa_ossl_init(RSA *rsa)
{
rsa->flags |= RSA_FLAG_CACHE_PUBLIC | RSA_FLAG_CACHE_PRIVATE;
return 1;
}
static int rsa_ossl_finish(RSA *rsa)
{
int i;
RSA_PRIME_INFO *pinfo;
BN_MONT_CTX_free(rsa->_method_mod_n);
BN_MONT_CTX_free(rsa->_method_mod_p);
BN_MONT_CTX_free(rsa->_method_mod_q);
for (i = 0; i < sk_RSA_PRIME_INFO_num(rsa->prime_infos); i++) {
pinfo = sk_RSA_PRIME_INFO_value(rsa->prime_infos, i);
BN_MONT_CTX_free(pinfo->m);
}
return 1;
}
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