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9c0cf214e7
constant time with a memory access pattern that does not depend on secret information. [extended tests] Reviewed-by: Paul Dale <paul.dale@oracle.com> (Merged from https://github.com/openssl/openssl/pull/8543)
256 lines
7.3 KiB
C
256 lines
7.3 KiB
C
/*
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* Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (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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*/
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#include "internal/constant_time_locl.h"
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#include <stdio.h>
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#include "internal/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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int RSA_padding_add_PKCS1_type_1(unsigned char *to, int tlen,
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const unsigned char *from, int flen)
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{
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int j;
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unsigned char *p;
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if (flen > (tlen - RSA_PKCS1_PADDING_SIZE)) {
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RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_TYPE_1,
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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++) = 1; /* Private Key BT (Block Type) */
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/* pad out with 0xff data */
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j = tlen - 3 - flen;
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memset(p, 0xff, j);
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p += j;
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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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int RSA_padding_check_PKCS1_type_1(unsigned char *to, int tlen,
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const unsigned char *from, int flen,
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int num)
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{
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int i, j;
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const unsigned char *p;
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p = from;
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/*
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* The format is
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* 00 || 01 || PS || 00 || D
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* PS - padding string, at least 8 bytes of FF
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* D - data.
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*/
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if (num < 11)
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return -1;
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/* Accept inputs with and without the leading 0-byte. */
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if (num == flen) {
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if ((*p++) != 0x00) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
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RSA_R_INVALID_PADDING);
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return -1;
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}
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flen--;
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}
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if ((num != (flen + 1)) || (*(p++) != 0x01)) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
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RSA_R_BLOCK_TYPE_IS_NOT_01);
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return -1;
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}
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/* scan over padding data */
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j = flen - 1; /* one for type. */
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for (i = 0; i < j; i++) {
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if (*p != 0xff) { /* should decrypt to 0xff */
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if (*p == 0) {
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p++;
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break;
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} else {
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
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RSA_R_BAD_FIXED_HEADER_DECRYPT);
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return -1;
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}
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}
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p++;
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}
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if (i == j) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
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RSA_R_NULL_BEFORE_BLOCK_MISSING);
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return -1;
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}
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if (i < 8) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
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RSA_R_BAD_PAD_BYTE_COUNT);
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return -1;
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}
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i++; /* Skip over the '\0' */
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j -= i;
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if (j > tlen) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1, RSA_R_DATA_TOO_LARGE);
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return -1;
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}
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memcpy(to, p, (unsigned int)j);
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return j;
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}
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int RSA_padding_add_PKCS1_type_2(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_PKCS1_TYPE_2,
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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 - 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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*(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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int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
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const unsigned char *from, int flen,
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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;
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int zero_index = 0, msg_index, mlen = -1;
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if (tlen <= 0 || flen <= 0)
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return -1;
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/*
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* PKCS#1 v1.5 decryption. See "PKCS #1 v2.2: RSA Cryptography Standard",
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* section 7.2.2.
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*/
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if (flen > num || num < 11) {
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
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RSA_R_PKCS_DECODING_ERROR);
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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_PKCS1_TYPE_2, 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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/* scan over padding data */
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found_zero_byte = 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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}
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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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/*
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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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/*
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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_clear_free(em, num);
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RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, RSA_R_PKCS_DECODING_ERROR);
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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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