rsa_ssl.c
/* crypto/rsa/rsa_ssl.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* 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 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 acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS 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 AUTHOR OR 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.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/rand.h>
#include "constant_time_locl.h"
int RSA_padding_add_SSLv23(unsigned char *to, int tlen,
const unsigned char *from, int flen)
{
int i, j;
unsigned char *p;
if (flen > (tlen - 11)) {
RSAerr(RSA_F_RSA_PADDING_ADD_SSLV23,
RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
return (0);
}
p = (unsigned char *)to;
*(p++) = 0;
*(p++) = 2; /* Public Key BT (Block Type) */
/* pad out with non-zero random data */
j = tlen - 3 - 8 - flen;
if (RAND_bytes(p, j) <= 0)
return (0);
for (i = 0; i < j; i++) {
if (*p == '\0')
do {
if (RAND_bytes(p, 1) <= 0)
return (0);
} while (*p == '\0');
p++;
}
memset(p, 3, 8);
p += 8;
*(p++) = '\0';
memcpy(p, from, (unsigned int)flen);
return (1);
}
/*
* Copy of RSA_padding_check_PKCS1_type_2 with a twist that rejects padding
* if nul delimiter is not preceded by 8 consecutive 0x03 bytes. It also
* preserves error code reporting for backward compatibility.
*/
int RSA_padding_check_SSLv23(unsigned char *to, int tlen,
const unsigned char *from, int flen, int num)
{
int i;
/* |em| is the encoded message, zero-padded to exactly |num| bytes */
unsigned char *em = NULL;
unsigned int good, found_zero_byte, mask, threes_in_row;
int zero_index = 0, msg_index, mlen = -1, err;
if (tlen <= 0 || flen <= 0)
return -1;
if (flen > num || num < 11) {
RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, RSA_R_DATA_TOO_SMALL);
return (-1);
}
em = OPENSSL_malloc(num);
if (em == NULL) {
RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, ERR_R_MALLOC_FAILURE);
return -1;
}
/*
* 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;
}
good = constant_time_is_zero(em[0]);
good &= constant_time_eq(em[1], 2);
err = constant_time_select_int(good, 0, RSA_R_BLOCK_TYPE_IS_NOT_02);
mask = ~good;
/* scan over padding data */
found_zero_byte = 0;
threes_in_row = 0;
for (i = 2; i < num; i++) {
unsigned int equals0 = constant_time_is_zero(em[i]);
zero_index = constant_time_select_int(~found_zero_byte & equals0,
i, zero_index);
found_zero_byte |= equals0;
threes_in_row += 1 & ~found_zero_byte;
threes_in_row &= found_zero_byte | constant_time_eq(em[i], 3);
}
/*
* PS must be at least 8 bytes long, and it starts two bytes into |em|.
* If we never found a 0-byte, then |zero_index| is 0 and the check
* also fails.
*/
good &= constant_time_ge(zero_index, 2 + 8);
err = constant_time_select_int(mask | good, err,
RSA_R_NULL_BEFORE_BLOCK_MISSING);
mask = ~good;
good &= constant_time_ge(threes_in_row, 8);
err = constant_time_select_int(mask | good, err,
RSA_R_SSLV3_ROLLBACK_ATTACK);
mask = ~good;
/*
* Skip the zero byte. This is incorrect if we never found a zero-byte
* but in this case we also do not copy the message out.
*/
msg_index = zero_index + 1;
mlen = num - msg_index;
/*
* For good measure, do this check in constant time as well.
*/
good &= constant_time_ge(tlen, mlen);
err = constant_time_select_int(mask | good, err, RSA_R_DATA_TOO_LARGE);
/*
* Move the result in-place by |num|-11-|mlen| bytes to the left.
* Then if |good| move |mlen| bytes from |em|+11 to |to|.
* Otherwise leave |to| unchanged.
* Copy the memory back in a way that does not reveal the size of
* the data being copied via a timing side channel. This requires copying
* parts of the buffer multiple times based on the bits set in the real
* length. Clear bits do a non-copy with identical access pattern.
* The loop below has overall complexity of O(N*log(N)).
*/
tlen = constant_time_select_int(constant_time_lt(num - 11, tlen),
num - 11, tlen);
for (msg_index = 1; msg_index < num - 11; msg_index <<= 1) {
mask = ~constant_time_eq(msg_index & (num - 11 - mlen), 0);
for (i = 11; i < num - msg_index; i++)
em[i] = constant_time_select_8(mask, em[i + msg_index], em[i]);
}
for (i = 0; i < tlen; i++) {
mask = good & constant_time_lt(i, mlen);
to[i] = constant_time_select_8(mask, em[i + 11], to[i]);
}
OPENSSL_cleanse(em, num);
OPENSSL_free(em);
RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, err);
err_clear_last_constant_time(1 & good);
return constant_time_select_int(good, mlen, -1);
}
