359 lines
11 KiB
C
Executable File
359 lines
11 KiB
C
Executable File
/* $OpenBSD: rsa_oaep.c,v 1.35 2022/02/20 19:16:34 tb Exp $ */
|
|
/*
|
|
* Copyright 1999-2018 The OpenSSL Project Authors. All Rights Reserved.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions
|
|
* are met:
|
|
*
|
|
* 1. Redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer.
|
|
*
|
|
* 2. Redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in
|
|
* the documentation and/or other materials provided with the
|
|
* distribution.
|
|
*
|
|
* 3. All advertising materials mentioning features or use of this
|
|
* software must display the following acknowledgment:
|
|
* "This product includes software developed by the OpenSSL Project
|
|
* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
|
|
*
|
|
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
|
|
* endorse or promote products derived from this software without
|
|
* prior written permission. For written permission, please contact
|
|
* openssl-core@openssl.org.
|
|
*
|
|
* 5. Products derived from this software may not be called "OpenSSL"
|
|
* nor may "OpenSSL" appear in their names without prior written
|
|
* permission of the OpenSSL Project.
|
|
*
|
|
* 6. Redistributions of any form whatsoever must retain the following
|
|
* acknowledgment:
|
|
* "This product includes software developed by the OpenSSL Project
|
|
* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
|
|
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
|
|
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
|
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
|
|
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
|
|
* OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
* ====================================================================
|
|
*
|
|
* This product includes cryptographic software written by Eric Young
|
|
* (eay@cryptsoft.com). This product includes software written by Tim
|
|
* Hudson (tjh@cryptsoft.com).
|
|
*
|
|
*/
|
|
|
|
/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
|
|
|
|
/* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
|
|
* <URL: http://www.shoup.net/papers/oaep.ps.Z>
|
|
* for problems with the security proof for the
|
|
* original OAEP scheme, which EME-OAEP is based on.
|
|
*
|
|
* A new proof can be found in E. Fujisaki, T. Okamoto,
|
|
* D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
|
|
* Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
|
|
* The new proof has stronger requirements for the
|
|
* underlying permutation: "partial-one-wayness" instead
|
|
* of one-wayness. For the RSA function, this is
|
|
* an equivalent notion.
|
|
*/
|
|
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
|
|
#include <openssl/bn.h>
|
|
#include <openssl/err.h>
|
|
#include <openssl/evp.h>
|
|
#include <openssl/rsa.h>
|
|
#include <openssl/sha.h>
|
|
|
|
#include "constant_time_locl.h"
|
|
#include "evp_locl.h"
|
|
#include "rsa_locl.h"
|
|
|
|
int
|
|
RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
|
|
const unsigned char *from, int flen, const unsigned char *param, int plen)
|
|
{
|
|
return RSA_padding_add_PKCS1_OAEP_mgf1(to, tlen, from, flen, param,
|
|
plen, NULL, NULL);
|
|
}
|
|
|
|
int
|
|
RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
|
|
const unsigned char *from, int flen, const unsigned char *param, int plen,
|
|
const EVP_MD *md, const EVP_MD *mgf1md)
|
|
{
|
|
int i, emlen = tlen - 1;
|
|
unsigned char *db, *seed;
|
|
unsigned char *dbmask = NULL;
|
|
unsigned char seedmask[EVP_MAX_MD_SIZE];
|
|
int mdlen, dbmask_len = 0;
|
|
int rv = 0;
|
|
|
|
if (md == NULL)
|
|
md = EVP_sha1();
|
|
if (mgf1md == NULL)
|
|
mgf1md = md;
|
|
|
|
if ((mdlen = EVP_MD_size(md)) <= 0)
|
|
goto err;
|
|
|
|
if (flen > emlen - 2 * mdlen - 1) {
|
|
RSAerror(RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
|
|
goto err;
|
|
}
|
|
|
|
if (emlen < 2 * mdlen + 1) {
|
|
RSAerror(RSA_R_KEY_SIZE_TOO_SMALL);
|
|
goto err;
|
|
}
|
|
|
|
to[0] = 0;
|
|
seed = to + 1;
|
|
db = to + mdlen + 1;
|
|
|
|
if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL))
|
|
goto err;
|
|
|
|
memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1);
|
|
db[emlen - flen - mdlen - 1] = 0x01;
|
|
memcpy(db + emlen - flen - mdlen, from, flen);
|
|
arc4random_buf(seed, mdlen);
|
|
|
|
dbmask_len = emlen - mdlen;
|
|
if ((dbmask = malloc(dbmask_len)) == NULL) {
|
|
RSAerror(ERR_R_MALLOC_FAILURE);
|
|
goto err;
|
|
}
|
|
|
|
if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0)
|
|
goto err;
|
|
for (i = 0; i < dbmask_len; i++)
|
|
db[i] ^= dbmask[i];
|
|
if (PKCS1_MGF1(seedmask, mdlen, db, dbmask_len, mgf1md) < 0)
|
|
goto err;
|
|
for (i = 0; i < mdlen; i++)
|
|
seed[i] ^= seedmask[i];
|
|
|
|
rv = 1;
|
|
|
|
err:
|
|
explicit_bzero(seedmask, sizeof(seedmask));
|
|
freezero(dbmask, dbmask_len);
|
|
|
|
return rv;
|
|
}
|
|
|
|
int
|
|
RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
|
|
const unsigned char *from, int flen, int num, const unsigned char *param,
|
|
int plen)
|
|
{
|
|
return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from, flen, num,
|
|
param, plen, NULL, NULL);
|
|
}
|
|
|
|
int
|
|
RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
|
|
const unsigned char *from, int flen, int num, const unsigned char *param,
|
|
int plen, const EVP_MD *md, const EVP_MD *mgf1md)
|
|
{
|
|
int i, dblen = 0, mlen = -1, one_index = 0, msg_index;
|
|
unsigned int good = 0, found_one_byte, mask;
|
|
const unsigned char *maskedseed, *maskeddb;
|
|
unsigned char seed[EVP_MAX_MD_SIZE], phash[EVP_MAX_MD_SIZE];
|
|
unsigned char *db = NULL, *em = NULL;
|
|
int mdlen;
|
|
|
|
if (md == NULL)
|
|
md = EVP_sha1();
|
|
if (mgf1md == NULL)
|
|
mgf1md = md;
|
|
|
|
if ((mdlen = EVP_MD_size(md)) <= 0)
|
|
return -1;
|
|
|
|
if (tlen <= 0 || flen <= 0)
|
|
return -1;
|
|
|
|
/*
|
|
* |num| is the length of the modulus; |flen| is the length of the
|
|
* encoded message. Therefore, for any |from| that was obtained by
|
|
* decrypting a ciphertext, we must have |flen| <= |num|. Similarly,
|
|
* |num| >= 2 * |mdlen| + 2 must hold for the modulus irrespective
|
|
* of the ciphertext, see PKCS #1 v2.2, section 7.1.2.
|
|
* This does not leak any side-channel information.
|
|
*/
|
|
if (num < flen || num < 2 * mdlen + 2) {
|
|
RSAerror(RSA_R_OAEP_DECODING_ERROR);
|
|
return -1;
|
|
}
|
|
|
|
dblen = num - mdlen - 1;
|
|
if ((db = malloc(dblen)) == NULL) {
|
|
RSAerror(ERR_R_MALLOC_FAILURE);
|
|
goto cleanup;
|
|
}
|
|
if ((em = malloc(num)) == NULL) {
|
|
RSAerror(ERR_R_MALLOC_FAILURE);
|
|
goto cleanup;
|
|
}
|
|
|
|
/*
|
|
* Caller is encouraged to pass zero-padded message created with
|
|
* BN_bn2binpad. Trouble is that since we can't read out of |from|'s
|
|
* bounds, it's impossible to have an invariant memory access pattern
|
|
* in case |from| was not zero-padded in advance.
|
|
*/
|
|
for (from += flen, em += num, i = 0; i < num; i++) {
|
|
mask = ~constant_time_is_zero(flen);
|
|
flen -= 1 & mask;
|
|
from -= 1 & mask;
|
|
*--em = *from & mask;
|
|
}
|
|
|
|
/*
|
|
* The first byte must be zero, however we must not leak if this is
|
|
* true. See James H. Manger, "A Chosen Ciphertext Attack on RSA
|
|
* Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001).
|
|
*/
|
|
good = constant_time_is_zero(em[0]);
|
|
|
|
maskedseed = em + 1;
|
|
maskeddb = em + 1 + mdlen;
|
|
|
|
if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md))
|
|
goto cleanup;
|
|
for (i = 0; i < mdlen; i++)
|
|
seed[i] ^= maskedseed[i];
|
|
|
|
if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md))
|
|
goto cleanup;
|
|
for (i = 0; i < dblen; i++)
|
|
db[i] ^= maskeddb[i];
|
|
|
|
if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL))
|
|
goto cleanup;
|
|
|
|
good &= constant_time_is_zero(timingsafe_memcmp(db, phash, mdlen));
|
|
|
|
found_one_byte = 0;
|
|
for (i = mdlen; i < dblen; i++) {
|
|
/*
|
|
* Padding consists of a number of 0-bytes, followed by a 1.
|
|
*/
|
|
unsigned int equals1 = constant_time_eq(db[i], 1);
|
|
unsigned int equals0 = constant_time_is_zero(db[i]);
|
|
|
|
one_index = constant_time_select_int(~found_one_byte & equals1,
|
|
i, one_index);
|
|
found_one_byte |= equals1;
|
|
good &= (found_one_byte | equals0);
|
|
}
|
|
|
|
good &= found_one_byte;
|
|
|
|
/*
|
|
* At this point |good| is zero unless the plaintext was valid,
|
|
* so plaintext-awareness ensures timing side-channels are no longer a
|
|
* concern.
|
|
*/
|
|
msg_index = one_index + 1;
|
|
mlen = dblen - msg_index;
|
|
|
|
/*
|
|
* For good measure, do this check in constant time as well.
|
|
*/
|
|
good &= constant_time_ge(tlen, mlen);
|
|
|
|
/*
|
|
* Even though we can't fake result's length, we can pretend copying
|
|
* |tlen| bytes where |mlen| bytes would be real. The last |tlen| of
|
|
* |dblen| bytes are viewed as a circular buffer starting at |tlen|-|mlen'|,
|
|
* where |mlen'| is the "saturated" |mlen| value. Deducing information
|
|
* about failure or |mlen| would require an attacker to observe
|
|
* memory access patterns with byte granularity *as it occurs*. It
|
|
* should be noted that failure is indistinguishable from normal
|
|
* operation if |tlen| is fixed by protocol.
|
|
*/
|
|
tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen),
|
|
dblen - mdlen - 1, tlen);
|
|
msg_index = constant_time_select_int(good, msg_index, dblen - tlen);
|
|
mlen = dblen - msg_index;
|
|
for (mask = good, i = 0; i < tlen; i++) {
|
|
unsigned int equals = constant_time_eq(msg_index, dblen);
|
|
|
|
msg_index -= tlen & equals; /* rewind at EOF */
|
|
mask &= ~equals; /* mask = 0 at EOF */
|
|
to[i] = constant_time_select_8(mask, db[msg_index++], to[i]);
|
|
}
|
|
|
|
/*
|
|
* To avoid chosen ciphertext attacks, the error message should not
|
|
* reveal which kind of decoding error happened.
|
|
*/
|
|
RSAerror(RSA_R_OAEP_DECODING_ERROR);
|
|
err_clear_last_constant_time(1 & good);
|
|
|
|
cleanup:
|
|
explicit_bzero(seed, sizeof(seed));
|
|
freezero(db, dblen);
|
|
freezero(em, num);
|
|
|
|
return constant_time_select_int(good, mlen, -1);
|
|
}
|
|
|
|
int
|
|
PKCS1_MGF1(unsigned char *mask, long len, const unsigned char *seed,
|
|
long seedlen, const EVP_MD *dgst)
|
|
{
|
|
long i, outlen = 0;
|
|
unsigned char cnt[4];
|
|
EVP_MD_CTX c;
|
|
unsigned char md[EVP_MAX_MD_SIZE];
|
|
int mdlen;
|
|
int rv = -1;
|
|
|
|
EVP_MD_CTX_init(&c);
|
|
mdlen = EVP_MD_size(dgst);
|
|
if (mdlen < 0)
|
|
goto err;
|
|
for (i = 0; outlen < len; i++) {
|
|
cnt[0] = (unsigned char)((i >> 24) & 255);
|
|
cnt[1] = (unsigned char)((i >> 16) & 255);
|
|
cnt[2] = (unsigned char)((i >> 8)) & 255;
|
|
cnt[3] = (unsigned char)(i & 255);
|
|
if (!EVP_DigestInit_ex(&c, dgst, NULL) ||
|
|
!EVP_DigestUpdate(&c, seed, seedlen) ||
|
|
!EVP_DigestUpdate(&c, cnt, 4))
|
|
goto err;
|
|
if (outlen + mdlen <= len) {
|
|
if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
|
|
goto err;
|
|
outlen += mdlen;
|
|
} else {
|
|
if (!EVP_DigestFinal_ex(&c, md, NULL))
|
|
goto err;
|
|
memcpy(mask + outlen, md, len - outlen);
|
|
outlen = len;
|
|
}
|
|
}
|
|
rv = 0;
|
|
err:
|
|
EVP_MD_CTX_cleanup(&c);
|
|
return rv;
|
|
}
|