-/* crypto/rsa/rsa_pk1.c */
-/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
- * All rights reserved.
+/*
+ * Copyright 1995-2019 The OpenSSL Project Authors. 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.]
+ * Licensed under the OpenSSL license (the "License"). You may not use
+ * this file except in compliance with the License. You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
*/
#include "internal/constant_time_locl.h"
const unsigned char *p;
p = from;
- if ((num != (flen + 1)) || (*(p++) != 01)) {
+
+ /*
+ * The format is
+ * 00 || 01 || PS || 00 || D
+ * PS - padding string, at least 8 bytes of FF
+ * D - data.
+ */
+
+ if (num < 11)
+ return -1;
+
+ /* Accept inputs with and without the leading 0-byte. */
+ if (num == flen) {
+ if ((*p++) != 0x00) {
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
+ RSA_R_INVALID_PADDING);
+ return -1;
+ }
+ flen--;
+ }
+
+ if ((num != (flen + 1)) || (*(p++) != 0x01)) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_1,
RSA_R_BLOCK_TYPE_IS_NOT_01);
return (-1);
int i;
/* |em| is the encoded message, zero-padded to exactly |num| bytes */
unsigned char *em = NULL;
- unsigned int good, found_zero_byte;
+ unsigned int good, found_zero_byte, mask;
int zero_index = 0, msg_index, mlen = -1;
if (tlen < 0 || flen < 0)
* section 7.2.2.
*/
- if (flen > num)
- goto err;
-
- if (num < 11)
- goto err;
+ if (flen > num || num < 11) {
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
+ RSA_R_PKCS_DECODING_ERROR);
+ return -1;
+ }
- em = OPENSSL_zalloc(num);
+ em = OPENSSL_malloc(num);
if (em == NULL) {
RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE);
return -1;
}
/*
- * Always do this zero-padding copy (even when num == flen) to avoid
- * leaking that information. The copy still leaks some side-channel
- * information, but it's impossible to have a fixed memory access
- * pattern since we can't read out of the bounds of |from|.
- *
- * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL.
+ * 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.
*/
- memcpy(em + num - flen, from, flen);
+ 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);
+ /* scan over padding data */
found_zero_byte = 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);
+
+ zero_index = constant_time_select_int(~found_zero_byte & equals0,
+ i, zero_index);
found_zero_byte |= equals0;
}
* If we never found a 0-byte, then |zero_index| is 0 and the check
* also fails.
*/
- good &= constant_time_ge((unsigned int)(zero_index), 2 + 8);
+ good &= constant_time_ge(zero_index, 2 + 8);
/*
* Skip the zero byte. This is incorrect if we never found a zero-byte
mlen = num - msg_index;
/*
- * For good measure, do this check in constant time as well; it could
- * leak something if |tlen| was assuming valid padding.
+ * For good measure, do this check in constant time as well.
*/
- good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen));
+ good &= constant_time_ge(tlen, mlen);
/*
- * We can't continue in constant-time because we need to copy the result
- * and we cannot fake its length. This unavoidably leaks timing
- * information at the API boundary.
- * TODO(emilia): this could be addressed at the call site,
- * see BoringSSL commit 0aa0767340baf925bda4804882aab0cb974b2d26.
+ * 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)).
*/
- if (!good) {
- mlen = -1;
- goto err;
+ 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]);
}
- memcpy(to, em + msg_index, mlen);
+ OPENSSL_clear_free(em, num);
+ RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, RSA_R_PKCS_DECODING_ERROR);
+ err_clear_last_constant_time(1 & good);
- err:
- OPENSSL_free(em);
- if (mlen == -1)
- RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
- RSA_R_PKCS_DECODING_ERROR);
- return mlen;
+ return constant_time_select_int(good, mlen, -1);
}
projects / openssl.git / blobdiff