2016-05-17 18:51:34 +00:00
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/*
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2018-09-11 12:22:14 +00:00
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* Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
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1998-12-21 10:56:39 +00:00
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*
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2016-05-17 18:51:34 +00:00
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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1998-12-21 10:56:39 +00:00
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*/
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#include <stdio.h>
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2015-05-14 14:56:48 +00:00
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#include "internal/cryptlib.h"
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1999-04-23 22:13:45 +00:00
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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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2018-09-14 15:24:13 +00:00
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#include "internal/constant_time_locl.h"
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1998-12-21 10:56:39 +00:00
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2000-11-06 22:34:17 +00:00
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int RSA_padding_add_SSLv23(unsigned char *to, int tlen,
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2015-01-22 03:40:55 +00:00
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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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2017-08-22 17:25:23 +00:00
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return 0;
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2015-01-22 03:40:55 +00:00
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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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2017-08-22 17:25:23 +00:00
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return 0;
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2015-01-22 03:40:55 +00:00
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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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2017-08-22 17:25:23 +00:00
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return 0;
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2015-01-22 03:40:55 +00:00
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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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2017-08-22 17:25:23 +00:00
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return 1;
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2015-01-22 03:40:55 +00:00
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}
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1998-12-21 10:56:39 +00:00
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2018-09-14 15:24:13 +00:00
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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 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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2000-11-06 22:34:17 +00:00
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int RSA_padding_check_SSLv23(unsigned char *to, int tlen,
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2015-01-22 03:40:55 +00:00
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const unsigned char *from, int flen, int num)
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{
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2018-09-14 15:24:13 +00:00
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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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2015-01-22 03:40:55 +00:00
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if (flen < 10) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, RSA_R_DATA_TOO_SMALL);
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2017-08-22 17:25:23 +00:00
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return -1;
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2015-01-22 03:40:55 +00:00
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}
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2018-09-14 15:24:13 +00:00
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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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2017-08-22 17:25:23 +00:00
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return -1;
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2015-01-22 03:40:55 +00:00
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}
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2018-09-14 15:24:13 +00:00
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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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2015-01-22 03:40:55 +00:00
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}
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2018-09-14 15:24:13 +00:00
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from = em;
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good = constant_time_is_zero(from[0]);
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good &= constant_time_eq(from[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(from[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(from[i], 3);
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2015-01-22 03:40:55 +00:00
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}
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2018-09-14 15:24:13 +00:00
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/*
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* PS must be at least 8 bytes long, and it starts two bytes into |from|.
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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_lt(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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* Even though we can't fake result's length, we can pretend copying
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* |tlen| bytes where |mlen| bytes would be real. Last |tlen| of |num|
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* bytes are viewed as circular buffer with start at |tlen|-|mlen'|,
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* where |mlen'| is "saturated" |mlen| value. Deducing information
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* about failure or |mlen| would take attacker's ability to observe
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* memory access pattern with byte granularity *as it occurs*. It
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* should be noted that failure is indistinguishable from normal
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* operation if |tlen| is fixed by protocol.
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*/
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tlen = constant_time_select_int(constant_time_lt(num, tlen), num, tlen);
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msg_index = constant_time_select_int(good, msg_index, num - tlen);
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mlen = num - msg_index;
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for (from += msg_index, mask = good, i = 0; i < tlen; i++) {
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unsigned int equals = constant_time_eq(i, mlen);
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from -= tlen & equals; /* if (i == mlen) rewind */
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mask &= mask ^ equals; /* if (i == mlen) mask = 0 */
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to[i] = constant_time_select_8(mask, from[i], to[i]);
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2015-01-22 03:40:55 +00:00
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}
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2018-09-14 15:24:13 +00:00
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OPENSSL_clear_free(em, num);
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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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2015-01-22 03:40:55 +00:00
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}
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