89 lines
3 KiB
C++
89 lines
3 KiB
C++
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// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2013 The Bitcoin developers
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// Distributed under the MIT/X11 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 "sigcache.h"
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#include "key.h"
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#include "random.h"
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#include "uint256.h"
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#include "util.h"
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#include <boost/thread.hpp>
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#include <boost/tuple/tuple_comparison.hpp>
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namespace {
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// Valid signature cache, to avoid doing expensive ECDSA signature checking
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// twice for every transaction (once when accepted into memory pool, and
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// again when accepted into the block chain)
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class CSignatureCache
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{
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private:
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// sigdata_type is (signature hash, signature, public key):
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typedef boost::tuple<uint256, std::vector<unsigned char>, CPubKey> sigdata_type;
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std::set< sigdata_type> setValid;
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boost::shared_mutex cs_sigcache;
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public:
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bool
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Get(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
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{
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boost::shared_lock<boost::shared_mutex> lock(cs_sigcache);
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sigdata_type k(hash, vchSig, pubKey);
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std::set<sigdata_type>::iterator mi = setValid.find(k);
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if (mi != setValid.end())
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return true;
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return false;
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}
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void Set(const uint256 &hash, const std::vector<unsigned char>& vchSig, const CPubKey& pubKey)
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{
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// DoS prevention: limit cache size to less than 10MB
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// (~200 bytes per cache entry times 50,000 entries)
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// Since there are a maximum of 20,000 signature operations per block
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// 50,000 is a reasonable default.
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int64_t nMaxCacheSize = GetArg("-maxsigcachesize", 50000);
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if (nMaxCacheSize <= 0) return;
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boost::unique_lock<boost::shared_mutex> lock(cs_sigcache);
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while (static_cast<int64_t>(setValid.size()) > nMaxCacheSize)
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{
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// Evict a random entry. Random because that helps
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// foil would-be DoS attackers who might try to pre-generate
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// and re-use a set of valid signatures just-slightly-greater
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// than our cache size.
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uint256 randomHash = GetRandHash();
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std::vector<unsigned char> unused;
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std::set<sigdata_type>::iterator it =
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setValid.lower_bound(sigdata_type(randomHash, unused, unused));
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if (it == setValid.end())
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it = setValid.begin();
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setValid.erase(*it);
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}
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sigdata_type k(hash, vchSig, pubKey);
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setValid.insert(k);
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}
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};
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}
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bool CachingSignatureChecker::VerifySignature(const std::vector<unsigned char>& vchSig, const CPubKey& pubkey, const uint256& sighash, int flags) const
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{
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static CSignatureCache signatureCache;
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if (signatureCache.Get(sighash, vchSig, pubkey))
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return true;
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if (!SignatureChecker::VerifySignature(vchSig, pubkey, sighash, flags))
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return false;
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if (!(flags & SCRIPT_VERIFY_NOCACHE))
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signatureCache.Set(sighash, vchSig, pubkey);
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return true;
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}
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