fdda3c5085
The main and test networks are configured to use parameters that are currently low-memory but usable with the basic solver; they will be increased once the solver is optimised. The regtest network is configured to have extremely low memory usage for speed. Note that Bitcoin's double-hasher is used for the difficulty check. This does not match the paper, but is simpler than changing the block header serialization. Single hashing is kept for the EquiHash solver because there is no requirement on execution time there, only on memory usage.
132 lines
4.9 KiB
C++
132 lines
4.9 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2014 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include "primitives/block.h"
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#include "hash.h"
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#include "tinyformat.h"
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#include "utilstrencodings.h"
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#include "crypto/common.h"
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uint256 CBlockHeader::GetHash() const
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{
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return SerializeHash(*this);
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}
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uint256 CBlock::BuildMerkleTree(bool* fMutated) const
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{
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/* WARNING! If you're reading this because you're learning about crypto
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and/or designing a new system that will use merkle trees, keep in mind
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that the following merkle tree algorithm has a serious flaw related to
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duplicate txids, resulting in a vulnerability (CVE-2012-2459).
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The reason is that if the number of hashes in the list at a given time
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is odd, the last one is duplicated before computing the next level (which
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is unusual in Merkle trees). This results in certain sequences of
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transactions leading to the same merkle root. For example, these two
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trees:
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A A
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/ \ / \
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B C B C
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/ \ | / \ / \
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D E F D E F F
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/ \ / \ / \ / \ / \ / \ / \
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1 2 3 4 5 6 1 2 3 4 5 6 5 6
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for transaction lists [1,2,3,4,5,6] and [1,2,3,4,5,6,5,6] (where 5 and
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6 are repeated) result in the same root hash A (because the hash of both
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of (F) and (F,F) is C).
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The vulnerability results from being able to send a block with such a
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transaction list, with the same merkle root, and the same block hash as
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the original without duplication, resulting in failed validation. If the
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receiving node proceeds to mark that block as permanently invalid
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however, it will fail to accept further unmodified (and thus potentially
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valid) versions of the same block. We defend against this by detecting
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the case where we would hash two identical hashes at the end of the list
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together, and treating that identically to the block having an invalid
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merkle root. Assuming no double-SHA256 collisions, this will detect all
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known ways of changing the transactions without affecting the merkle
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root.
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*/
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vMerkleTree.clear();
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vMerkleTree.reserve(vtx.size() * 2 + 16); // Safe upper bound for the number of total nodes.
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for (std::vector<CTransaction>::const_iterator it(vtx.begin()); it != vtx.end(); ++it)
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vMerkleTree.push_back(it->GetHash());
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int j = 0;
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bool mutated = false;
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for (int nSize = vtx.size(); nSize > 1; nSize = (nSize + 1) / 2)
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{
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for (int i = 0; i < nSize; i += 2)
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{
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int i2 = std::min(i+1, nSize-1);
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if (i2 == i + 1 && i2 + 1 == nSize && vMerkleTree[j+i] == vMerkleTree[j+i2]) {
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// Two identical hashes at the end of the list at a particular level.
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mutated = true;
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}
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vMerkleTree.push_back(Hash(BEGIN(vMerkleTree[j+i]), END(vMerkleTree[j+i]),
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BEGIN(vMerkleTree[j+i2]), END(vMerkleTree[j+i2])));
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}
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j += nSize;
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}
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if (fMutated) {
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*fMutated = mutated;
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}
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return (vMerkleTree.empty() ? uint256() : vMerkleTree.back());
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}
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std::vector<uint256> CBlock::GetMerkleBranch(int nIndex) const
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{
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if (vMerkleTree.empty())
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BuildMerkleTree();
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std::vector<uint256> vMerkleBranch;
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int j = 0;
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for (int nSize = vtx.size(); nSize > 1; nSize = (nSize + 1) / 2)
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{
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int i = std::min(nIndex^1, nSize-1);
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vMerkleBranch.push_back(vMerkleTree[j+i]);
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nIndex >>= 1;
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j += nSize;
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}
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return vMerkleBranch;
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}
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uint256 CBlock::CheckMerkleBranch(uint256 hash, const std::vector<uint256>& vMerkleBranch, int nIndex)
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{
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if (nIndex == -1)
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return uint256();
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for (std::vector<uint256>::const_iterator it(vMerkleBranch.begin()); it != vMerkleBranch.end(); ++it)
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{
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if (nIndex & 1)
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hash = Hash(BEGIN(*it), END(*it), BEGIN(hash), END(hash));
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else
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hash = Hash(BEGIN(hash), END(hash), BEGIN(*it), END(*it));
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nIndex >>= 1;
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}
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return hash;
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}
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std::string CBlock::ToString() const
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{
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std::stringstream s;
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s << strprintf("CBlock(hash=%s, ver=%d, hashPrevBlock=%s, hashMerkleRoot=%s, nTime=%u, nBits=%08x, nNonce=%s, vtx=%u)\n",
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GetHash().ToString(),
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nVersion,
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hashPrevBlock.ToString(),
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hashMerkleRoot.ToString(),
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nTime, nBits, nNonce.ToString(),
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vtx.size());
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for (unsigned int i = 0; i < vtx.size(); i++)
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{
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s << " " << vtx[i].ToString() << "\n";
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}
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s << " vMerkleTree: ";
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for (unsigned int i = 0; i < vMerkleTree.size(); i++)
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s << " " << vMerkleTree[i].ToString();
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s << "\n";
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return s.str();
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}
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