// Copyright (c) 2014, The Monero Project
//
// All rights reserved.
//
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// permitted provided that the following conditions are met:
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// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
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// 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.
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// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
#include <alloca.h>
#include <assert.h>
#include <stddef.h>
#include <string.h>
#include "hash-ops.h"
/// Quick check if this is power of two (use on unsigned types; in this case for size_t only)
bool ispowerof2_size_t(size_t x) {
return x && !(x & (x - 1));
}
/***
* Round to power of two, for count>=3 and for count being not too large (as reasonable for tree hash calculations)
*/
size_t tree_hash_cnt(size_t count) {
assert( count >= 3); // cases for 0,1,2 are handled elsewhere
// Round down the count size: fun(2**n)= 2**(n-1) to round down to power of two
size_t tmp = count - 1;
size_t jj = 1;
for (jj=1 ; tmp != 0 ; ++jj) {
tmp /= 2; // dividing by 2 until to get how many powers of 2 fits size_to tmp
}
size_t cnt = 1 << (jj-2); // cnt is the count, but rounded down to power of two
// printf("count=%zu cnt=%zu jj=%zu tmp=%zu \n" , count,cnt,jj,tmp);
assert( cnt > 0 ); assert( cnt >= count/2 ); assert( cnt <= count );
assert( ispowerof2_size_t( cnt ));
return cnt;
}
void tree_hash(const char (*hashes)[HASH_SIZE], size_t count, char *root_hash) {
// The blockchain block at height 202612 http://monerochain.info/block/bbd604d2ba11ba27935e006ed39c9bfdd99b76bf4a50654bc1e1e61217962698
// contained 514 transactions, that triggered bad calculation of variable "cnt" in the original version of this function
// as from CryptoNote code.
//
// This bug applies to all CN altcoins.
//
// Mathematical bug here was first published on 14:45:34 (GMT+2) 2014-09-04 by Rafal Freeman <rfree>
// https://github.com/rfree2monero/bitmonero/commit/b417abfb7a297d09f1bbb6de29030f8de9952ac8
// and soon also applied to CryptoNote (15:10 GMT+2), and BoolBerry used not fully correct work around:
// the work around of sizeof(size_t)*8 or <<3 as used before in 2 coins and in BBL later was blocking
// exploitation on normal platforms, how ever we strongly recommend the following fix because it removes
// mistake in mathematical formula.
assert(count > 0);
if (count == 1) {
memcpy(root_hash, hashes, HASH_SIZE);
} else if (count == 2) {
cn_fast_hash(hashes, 2 * HASH_SIZE, root_hash);
} else {
size_t i, j;
size_t cnt = tree_hash_cnt( count );
size_t max_size_t = (size_t) -1; // max allowed value of size_t
assert( cnt < max_size_t/2 ); // reasonable size to avoid any overflows. /2 is extra; Anyway should be limited much stronger by logical code
// as we have sane limits on transactions counts in blockchain rules
char (*ints)[HASH_SIZE];
size_t ints_size = cnt * HASH_SIZE;
ints = alloca(ints_size); memset( ints , 0 , ints_size); // allocate, and zero out as extra protection for using uninitialized mem
memcpy(ints, hashes, (2 * cnt - count) * HASH_SIZE);
for (i = 2 * cnt - count, j = 2 * cnt - count; j < cnt; i += 2, ++j) {
cn_fast_hash(hashes[i], 64, ints[j]);
}
assert(i == count);
while (cnt > 2) {
cnt >>= 1;
for (i = 0, j = 0; j < cnt; i += 2, ++j) {
cn_fast_hash(ints[i], 64, ints[j]);
}
}
cn_fast_hash(ints[0], 64, root_hash);
}
}
