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openssl/crypto/rsa/rsa_ossl.c
Juergen Christ 79040cf29e S390x: Support ME and CRT offloading 
S390x has to ability to offload modular exponentiation and CRT operations to
Crypto Express Adapters.  This possible performance optimization was not yet
used by OpenSSL.  Add support for offloading and implement an optimized
version of RSA and DH with it.

The environment variable OPENSSL_s390xcap now recognizes the token "nocex" to
prevent offloading.

Signed-off-by: Juergen Christ <jchrist@linux.ibm.com>

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20113)
2023-02-08 16:53:12 +01:00

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/*
* Copyright 1995-2022 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (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
*/
/*
* RSA low level APIs are deprecated for public use, but still ok for
* internal use.
*/
#include "internal/deprecated.h"
#include "internal/cryptlib.h"
#include "crypto/bn.h"
#include "rsa_local.h"
#include "internal/constant_time.h"
#include <openssl/evp.h>
#include <openssl/sha.h>
#include <openssl/hmac.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);
#ifdef S390X_MOD_EXP
static int rsa_ossl_s390x_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
BN_CTX *ctx);
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_s390x_mod_exp,
s390x_mod_exp,
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 */
};
#else
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 */
};
#endif
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) {
ERR_raise(ERR_LIB_RSA, RSA_R_MODULUS_TOO_LARGE);
return -1;
}
if (BN_ucmp(rsa->n, rsa->e) <= 0) {
ERR_raise(ERR_LIB_RSA, 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) {
ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
return -1;
}
}
if ((ctx = BN_CTX_new_ex(rsa->libctx)) == 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)
goto err;
switch (padding) {
case RSA_PKCS1_PADDING:
i = ossl_rsa_padding_add_PKCS1_type_2_ex(rsa->libctx, buf, num,
from, flen);
break;
case RSA_PKCS1_OAEP_PADDING:
i = ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(rsa->libctx, buf, num,
from, flen, NULL, 0,
NULL, NULL);
break;
case RSA_NO_PADDING:
i = RSA_padding_add_none(buf, num, from, flen);
break;
default:
ERR_raise(ERR_LIB_RSA, 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 */
ERR_raise(ERR_LIB_RSA, 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:
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;
if (!CRYPTO_THREAD_write_lock(rsa->lock))
return NULL;
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;
if (!BN_BLINDING_lock(b))
return 0;
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_ex(rsa->libctx)) == 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)
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;
default:
ERR_raise(ERR_LIB_RSA, 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 */
ERR_raise(ERR_LIB_RSA, 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->flags & RSA_FLAG_NO_BLINDING)) {
blinding = rsa_get_blinding(rsa, &local_blinding, ctx);
if (blinding == NULL) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (blinding != NULL) {
if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
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) {
ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
goto err;
}
if (rsa->d == NULL) {
ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
BN_free(d);
goto err;
}
BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
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:
BN_CTX_end(ctx);
BN_CTX_free(ctx);
OPENSSL_clear_free(buf, num);
return r;
}
static int derive_kdk(int flen, const unsigned char *from, RSA *rsa,
unsigned char *buf, int num, unsigned char *kdk)
{
int ret = 0;
HMAC_CTX *hmac = NULL;
EVP_MD *md = NULL;
unsigned int md_len = SHA256_DIGEST_LENGTH;
unsigned char d_hash[SHA256_DIGEST_LENGTH] = {0};
/*
* because we use d as a handle to rsa->d we need to keep it local and
* free before any further use of rsa->d
*/
BIGNUM *d = BN_new();
if (d == NULL) {
ERR_raise(ERR_LIB_RSA, ERR_R_CRYPTO_LIB);
goto err;
}
if (rsa->d == NULL) {
ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
BN_free(d);
goto err;
}
BN_with_flags(d, rsa->d, BN_FLG_CONSTTIME);
if (BN_bn2binpad(d, buf, num) < 0) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
BN_free(d);
goto err;
}
BN_free(d);
/*
* we use hardcoded hash so that migrating between versions that use
* different hash doesn't provide a Bleichenbacher oracle:
* if the attacker can see that different versions return different
* messages for the same ciphertext, they'll know that the message is
* syntethically generated, which means that the padding check failed
*/
md = EVP_MD_fetch(rsa->libctx, "sha256", NULL);
if (md == NULL) {
ERR_raise(ERR_LIB_RSA, ERR_R_FETCH_FAILED);
goto err;
}
if (EVP_Digest(buf, num, d_hash, NULL, md, NULL) <= 0) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
goto err;
}
hmac = HMAC_CTX_new();
if (hmac == NULL) {
ERR_raise(ERR_LIB_RSA, ERR_R_CRYPTO_LIB);
goto err;
}
if (HMAC_Init_ex(hmac, d_hash, sizeof(d_hash), md, NULL) <= 0) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
goto err;
}
if (flen < num) {
memset(buf, 0, num - flen);
if (HMAC_Update(hmac, buf, num - flen) <= 0) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (HMAC_Update(hmac, from, flen) <= 0) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
goto err;
}
md_len = SHA256_DIGEST_LENGTH;
if (HMAC_Final(hmac, kdk, &md_len) <= 0) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
goto err;
}
ret = 1;
err:
HMAC_CTX_free(hmac);
EVP_MD_free(md);
return ret;
}
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;
unsigned char kdk[SHA256_DIGEST_LENGTH] = {0};
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;
/*
* we need the value of the private exponent to perform implicit rejection
*/
if ((rsa->flags & RSA_FLAG_EXT_PKEY) && (padding == RSA_PKCS1_PADDING))
padding = RSA_PKCS1_NO_IMPLICIT_REJECT_PADDING;
if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
goto err;
BN_CTX_start(ctx);
f = BN_CTX_get(ctx);
ret = BN_CTX_get(ctx);
if (ret == NULL) {
ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
goto err;
}
num = BN_num_bytes(rsa->n);
buf = OPENSSL_malloc(num);
if (buf == NULL)
goto err;
/*
* This check was for equality but PGP does evil things and chops off the
* top '0' bytes
*/
if (flen > num) {
ERR_raise(ERR_LIB_RSA, RSA_R_DATA_GREATER_THAN_MOD_LEN);
goto err;
}
if (flen < 1) {
ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_SMALL);
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) {
ERR_raise(ERR_LIB_RSA, 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) {
ERR_raise(ERR_LIB_RSA, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (blinding != NULL) {
if (!local_blinding && ((unblind = BN_CTX_get(ctx)) == NULL)) {
ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
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) {
ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
goto err;
}
if (rsa->d == NULL) {
ERR_raise(ERR_LIB_RSA, RSA_R_MISSING_PRIVATE_KEY);
BN_free(d);
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);
}
/*
* derive the Key Derivation Key from private exponent and public
* ciphertext
*/
if (padding == RSA_PKCS1_PADDING) {
if (derive_kdk(flen, from, rsa, buf, num, kdk) == 0)
goto err;
}
if (blinding) {
/*
* ossl_bn_rsa_do_unblind() combines blinding inversion and
* 0-padded BN BE serialization
*/
j = ossl_bn_rsa_do_unblind(ret, blinding, unblind, rsa->n, ctx,
buf, num);
if (j == 0)
goto err;
} else {
j = BN_bn2binpad(ret, buf, num);
if (j < 0)
goto err;
}
switch (padding) {
case RSA_PKCS1_NO_IMPLICIT_REJECT_PADDING:
r = RSA_padding_check_PKCS1_type_2(to, num, buf, j, num);
break;
case RSA_PKCS1_PADDING:
r = ossl_rsa_padding_check_PKCS1_type_2(rsa->libctx, to, num, buf, j, num, kdk);
break;
case RSA_PKCS1_OAEP_PADDING:
r = RSA_padding_check_PKCS1_OAEP(to, num, buf, j, num, NULL, 0);
break;
case RSA_NO_PADDING:
memcpy(to, buf, (r = j));
break;
default:
ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
goto err;
}
#ifndef FIPS_MODULE
/*
* This trick doesn't work in the FIPS provider because libcrypto manages
* the error stack. Instead we opt not to put an error on the stack at all
* in case of padding failure in the FIPS provider.
*/
ERR_raise(ERR_LIB_RSA, RSA_R_PADDING_CHECK_FAILED);
err_clear_last_constant_time(1 & ~constant_time_msb(r));
#endif
err:
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) {
ERR_raise(ERR_LIB_RSA, RSA_R_MODULUS_TOO_LARGE);
return -1;
}
if (BN_ucmp(rsa->n, rsa->e) <= 0) {
ERR_raise(ERR_LIB_RSA, 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) {
ERR_raise(ERR_LIB_RSA, RSA_R_BAD_E_VALUE);
return -1;
}
}
if ((ctx = BN_CTX_new_ex(rsa->libctx)) == NULL)
goto err;
BN_CTX_start(ctx);
f = BN_CTX_get(ctx);
ret = BN_CTX_get(ctx);
if (ret == NULL) {
ERR_raise(ERR_LIB_RSA, ERR_R_BN_LIB);
goto err;
}
num = BN_num_bytes(rsa->n);
buf = OPENSSL_malloc(num);
if (buf == NULL)
goto err;
/*
* This check was for equality but PGP does evil things and chops off the
* top '0' bytes
*/
if (flen > num) {
ERR_raise(ERR_LIB_RSA, 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) {
ERR_raise(ERR_LIB_RSA, 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);
if (i < 0)
goto err;
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:
ERR_raise(ERR_LIB_RSA, RSA_R_UNKNOWN_PADDING_TYPE);
goto err;
}
if (r < 0)
ERR_raise(ERR_LIB_RSA, RSA_R_PADDING_CHECK_FAILED);
err:
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;
int ret = 0, smooth = 0;
#ifndef FIPS_MODULE
BIGNUM *r2, *m[RSA_MAX_PRIME_NUM - 2];
int i, ex_primes = 0;
RSA_PRIME_INFO *pinfo;
#endif
BN_CTX_start(ctx);
r1 = BN_CTX_get(ctx);
#ifndef FIPS_MODULE
r2 = BN_CTX_get(ctx);
#endif
m1 = BN_CTX_get(ctx);
vrfy = BN_CTX_get(ctx);
if (vrfy == NULL)
goto err;
#ifndef FIPS_MODULE
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;
#endif
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;
}
#ifndef FIPS_MODULE
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;
}
}
#endif
/*
* We MUST free |factor| before any further use of the prime factors
*/
BN_free(factor);
smooth = (rsa->meth->bn_mod_exp == BN_mod_exp_mont)
#ifndef FIPS_MODULE
&& (ex_primes == 0)
#endif
&& (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)
/* 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)
/*
* Use parallel exponentiations optimization if possible,
* otherwise fallback to two sequential exponentiations:
* m1 = m1^dmq1 mod q
* r1 = r1^dmp1 mod p
*/
|| !BN_mod_exp_mont_consttime_x2(m1, m1, rsa->dmq1, rsa->q,
rsa->_method_mod_q,
r1, r1, rsa->dmp1, rsa->p,
rsa->_method_mod_p,
ctx)
/* 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);
}
#ifndef FIPS_MODULE
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);
}
#endif
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;
#ifndef FIPS_MODULE
/* 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);
}
#endif
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)
{
#ifndef FIPS_MODULE
int i;
RSA_PRIME_INFO *pinfo;
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);
}
#endif
BN_MONT_CTX_free(rsa->_method_mod_n);
BN_MONT_CTX_free(rsa->_method_mod_p);
BN_MONT_CTX_free(rsa->_method_mod_q);
return 1;
}
#ifdef S390X_MOD_EXP
static int rsa_ossl_s390x_mod_exp(BIGNUM *r0, const BIGNUM *i, RSA *rsa,
BN_CTX *ctx)
{
if (rsa->version != RSA_ASN1_VERSION_MULTI) {
if (s390x_crt(r0, i, rsa->p, rsa->q, rsa->dmp1, rsa->dmq1, rsa->iqmp) == 1)
return 1;
}
return rsa_ossl_mod_exp(r0, i, rsa, ctx);
}
#endif
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