221 lines
8.3 KiB
C
221 lines
8.3 KiB
C
/* crypto/rsa/rsa_ssl.c */
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.]
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*/
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#include <stdio.h>
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#include "cryptlib.h"
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#include <openssl/bn.h>
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#include <openssl/rsa.h>
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#include <openssl/rand.h>
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#include "constant_time_locl.h"
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int RSA_padding_add_SSLv23(unsigned char *to, int tlen,
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const unsigned char *from, int flen)
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{
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int i, j;
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unsigned char *p;
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if (flen > (tlen - 11)) {
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RSAerr(RSA_F_RSA_PADDING_ADD_SSLV23,
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RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
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return (0);
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}
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p = (unsigned char *)to;
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*(p++) = 0;
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*(p++) = 2; /* Public Key BT (Block Type) */
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/* pad out with non-zero random data */
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j = tlen - 3 - 8 - flen;
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if (RAND_bytes(p, j) <= 0)
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return (0);
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for (i = 0; i < j; i++) {
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if (*p == '\0')
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do {
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if (RAND_bytes(p, 1) <= 0)
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return (0);
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} while (*p == '\0');
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p++;
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}
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memset(p, 3, 8);
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p += 8;
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*(p++) = '\0';
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memcpy(p, from, (unsigned int)flen);
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return (1);
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}
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/*
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* Copy of RSA_padding_check_PKCS1_type_2 with a twist that rejects padding
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* if nul delimiter is not preceded by 8 consecutive 0x03 bytes. It also
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* preserves error code reporting for backward compatibility.
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*/
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int RSA_padding_check_SSLv23(unsigned char *to, int tlen,
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const unsigned char *from, int flen, int num)
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{
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int i;
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/* |em| is the encoded message, zero-padded to exactly |num| bytes */
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unsigned char *em = NULL;
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unsigned int good, found_zero_byte, mask, threes_in_row;
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int zero_index = 0, msg_index, mlen = -1, err;
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if (tlen <= 0 || flen <= 0)
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return -1;
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if (flen > num || num < 11) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, RSA_R_DATA_TOO_SMALL);
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return (-1);
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}
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em = OPENSSL_malloc(num);
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if (em == NULL) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, ERR_R_MALLOC_FAILURE);
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return -1;
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}
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/*
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* Caller is encouraged to pass zero-padded message created with
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* BN_bn2binpad. Trouble is that since we can't read out of |from|'s
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* bounds, it's impossible to have an invariant memory access pattern
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* in case |from| was not zero-padded in advance.
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*/
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for (from += flen, em += num, i = 0; i < num; i++) {
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mask = ~constant_time_is_zero(flen);
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flen -= 1 & mask;
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from -= 1 & mask;
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*--em = *from & mask;
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}
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good = constant_time_is_zero(em[0]);
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good &= constant_time_eq(em[1], 2);
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err = constant_time_select_int(good, 0, RSA_R_BLOCK_TYPE_IS_NOT_02);
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mask = ~good;
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/* scan over padding data */
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found_zero_byte = 0;
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threes_in_row = 0;
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for (i = 2; i < num; i++) {
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unsigned int equals0 = constant_time_is_zero(em[i]);
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zero_index = constant_time_select_int(~found_zero_byte & equals0,
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i, zero_index);
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found_zero_byte |= equals0;
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threes_in_row += 1 & ~found_zero_byte;
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threes_in_row &= found_zero_byte | constant_time_eq(em[i], 3);
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}
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/*
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* PS must be at least 8 bytes long, and it starts two bytes into |em|.
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* If we never found a 0-byte, then |zero_index| is 0 and the check
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* also fails.
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*/
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good &= constant_time_ge(zero_index, 2 + 8);
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err = constant_time_select_int(mask | good, err,
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RSA_R_NULL_BEFORE_BLOCK_MISSING);
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mask = ~good;
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good &= constant_time_ge(threes_in_row, 8);
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err = constant_time_select_int(mask | good, err,
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RSA_R_SSLV3_ROLLBACK_ATTACK);
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mask = ~good;
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/*
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* Skip the zero byte. This is incorrect if we never found a zero-byte
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* but in this case we also do not copy the message out.
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*/
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msg_index = zero_index + 1;
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mlen = num - msg_index;
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/*
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* For good measure, do this check in constant time as well.
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*/
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good &= constant_time_ge(tlen, mlen);
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err = constant_time_select_int(mask | good, err, RSA_R_DATA_TOO_LARGE);
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/*
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* Move the result in-place by |num|-11-|mlen| bytes to the left.
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* Then if |good| move |mlen| bytes from |em|+11 to |to|.
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* Otherwise leave |to| unchanged.
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* Copy the memory back in a way that does not reveal the size of
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* the data being copied via a timing side channel. This requires copying
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* parts of the buffer multiple times based on the bits set in the real
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* length. Clear bits do a non-copy with identical access pattern.
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* The loop below has overall complexity of O(N*log(N)).
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*/
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tlen = constant_time_select_int(constant_time_lt(num - 11, tlen),
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num - 11, tlen);
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for (msg_index = 1; msg_index < num - 11; msg_index <<= 1) {
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mask = ~constant_time_eq(msg_index & (num - 11 - mlen), 0);
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for (i = 11; i < num - msg_index; i++)
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em[i] = constant_time_select_8(mask, em[i + msg_index], em[i]);
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}
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for (i = 0; i < tlen; i++) {
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mask = good & constant_time_lt(i, mlen);
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to[i] = constant_time_select_8(mask, em[i + 11], to[i]);
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}
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OPENSSL_cleanse(em, num);
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OPENSSL_free(em);
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RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, err);
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err_clear_last_constant_time(1 & good);
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return constant_time_select_int(good, mlen, -1);
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}
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