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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2022 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef BITCOIN_SCRIPT_SIGCACHE_H
#define BITCOIN_SCRIPT_SIGCACHE_H
#include <consensus/amount.h>
#include <crypto/sha256.h>
#include <cuckoocache.h>
#include <script/interpreter.h>
#include <span.h>
#include <uint256.h>
#include <util/hasher.h>
#include <cstddef>
#include <shared_mutex>
#include <vector>
class CPubKey;
class CTransaction;
class XOnlyPubKey;
// DoS prevention: limit cache size to 32MiB (over 1000000 entries on 64-bit
// systems). Due to how we count cache size, actual memory usage is slightly
// more (~32.25 MiB)
static constexpr size_t DEFAULT_VALIDATION_CACHE_BYTES{32 << 20};
static constexpr size_t DEFAULT_SIGNATURE_CACHE_BYTES{DEFAULT_VALIDATION_CACHE_BYTES / 2};
static constexpr size_t DEFAULT_SCRIPT_EXECUTION_CACHE_BYTES{DEFAULT_VALIDATION_CACHE_BYTES / 2};
static_assert(DEFAULT_VALIDATION_CACHE_BYTES == DEFAULT_SIGNATURE_CACHE_BYTES + DEFAULT_SCRIPT_EXECUTION_CACHE_BYTES);
/**
* Valid signature cache, to avoid doing expensive ECDSA signature checking
* twice for every transaction (once when accepted into memory pool, and
* again when accepted into the block chain)
*/
class SignatureCache
{
private:
//! Entries are SHA256(nonce || 'E' or 'S' || 31 zero bytes || signature hash || public key || signature):
CSHA256 m_salted_hasher_ecdsa;
CSHA256 m_salted_hasher_schnorr;
typedef CuckooCache::cache<uint256, SignatureCacheHasher> map_type;
map_type setValid;
std::shared_mutex cs_sigcache;
public:
SignatureCache(size_t max_size_bytes);
SignatureCache(const SignatureCache&) = delete;
SignatureCache& operator=(const SignatureCache&) = delete;
void ComputeEntryECDSA(uint256& entry, const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubkey) const;
void ComputeEntrySchnorr(uint256& entry, const uint256 &hash, Span<const unsigned char> sig, const XOnlyPubKey& pubkey) const;
bool Get(const uint256& entry, const bool erase);
void Set(const uint256& entry);
};
class CachingTransactionSignatureChecker : public TransactionSignatureChecker
{
private:
bool store;
SignatureCache& m_signature_cache;
public:
CachingTransactionSignatureChecker(const CTransaction* txToIn, unsigned int nInIn, const CAmount& amountIn, bool storeIn, SignatureCache& signature_cache, PrecomputedTransactionData& txdataIn) : TransactionSignatureChecker(txToIn, nInIn, amountIn, txdataIn, MissingDataBehavior::ASSERT_FAIL), store(storeIn), m_signature_cache(signature_cache) {}
bool VerifyECDSASignature(const std::vector<unsigned char>& vchSig, const CPubKey& vchPubKey, const uint256& sighash) const override;
bool VerifySchnorrSignature(Span<const unsigned char> sig, const XOnlyPubKey& pubkey, const uint256& sighash) const override;
};
#endif // BITCOIN_SCRIPT_SIGCACHE_H
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