diff options
| -rw-r--r-- | src/core.cpp | 16 | ||||
| -rw-r--r-- | src/core.h | 3 | ||||
| -rw-r--r-- | src/init.cpp | 1 | ||||
| -rw-r--r-- | src/main.cpp | 100 | ||||
| -rw-r--r-- | src/main.h | 3 | ||||
| -rw-r--r-- | src/txmempool.cpp | 1 |
6 files changed, 109 insertions, 15 deletions
diff --git a/src/core.cpp b/src/core.cpp index 6c5ee1c0f8..ca28624529 100644 --- a/src/core.cpp +++ b/src/core.cpp @@ -119,6 +119,22 @@ CTransaction& CTransaction::operator=(const CTransaction &tx) { return *this; } +bool CTransaction::IsEquivalentTo(const CTransaction& tx) const +{ + if (nVersion != tx.nVersion || + nLockTime != tx.nLockTime || + vin.size() != tx.vin.size() || + vout != tx.vout) + return false; + for (unsigned int i = 0; i < vin.size(); i++) + { + if (vin[i].nSequence != tx.vin[i].nSequence || + vin[i].prevout != tx.vin[i].prevout) + return false; + } + return true; +} + int64_t CTransaction::GetValueOut() const { int64_t nValueOut = 0; diff --git a/src/core.h b/src/core.h index 27fda95552..8606831575 100644 --- a/src/core.h +++ b/src/core.h @@ -256,6 +256,9 @@ public: return hash; } + // True if only scriptSigs are different + bool IsEquivalentTo(const CTransaction& tx) const; + // Return sum of txouts. int64_t GetValueOut() const; // GetValueIn() is a method on CCoinsViewCache, because diff --git a/src/init.cpp b/src/init.cpp index c7170b0f2d..bd732753e4 100644 --- a/src/init.cpp +++ b/src/init.cpp @@ -1175,6 +1175,7 @@ bool AppInit2(boost::thread_group& threadGroup) LogPrintf("mapAddressBook.size() = %u\n", pwalletMain ? pwalletMain->mapAddressBook.size() : 0); #endif + RegisterInternalSignals(); StartNode(threadGroup); if (fServer) StartRPCThreads(); diff --git a/src/main.cpp b/src/main.cpp index d86fd3a24d..48237c1b54 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -7,6 +7,7 @@ #include "addrman.h" #include "alert.h" +#include "bloom.h" #include "chainparams.h" #include "checkpoints.h" #include "checkqueue.h" @@ -122,6 +123,10 @@ namespace { map<uint256, pair<NodeId, list<uint256>::iterator> > mapBlocksToDownload; } +// Forward reference functions defined here: +static const unsigned int MAX_DOUBLESPEND_BLOOM = 1000; +static void RelayDoubleSpend(const COutPoint& outPoint, const CTransaction& doubleSpend, bool fInBlock, CBloomFilter& filter); + ////////////////////////////////////////////////////////////////////////////// // // dispatching functions @@ -143,9 +148,24 @@ struct CMainSignals { boost::signals2::signal<void (const uint256 &)> Inventory; // Tells listeners to broadcast their data. boost::signals2::signal<void ()> Broadcast; + // Notifies listeners of detection of a double-spent transaction. Arguments are outpoint that is + // double-spent, first transaction seen, double-spend transaction, and whether the second double-spend + // transaction was first seen in a block. + // Note: only notifies if the previous transaction is in the memory pool; if previous transction was in a block, + // then the double-spend simply fails when we try to lookup the inputs in the current UTXO set. + boost::signals2::signal<void (const COutPoint&, const CTransaction&, bool)> DetectedDoubleSpend; } g_signals; } +void RegisterInternalSignals() { + static CBloomFilter doubleSpendFilter; + seed_insecure_rand(); + doubleSpendFilter = CBloomFilter(MAX_DOUBLESPEND_BLOOM, 0.01, insecure_rand(), BLOOM_UPDATE_NONE); + + g_signals.DetectedDoubleSpend.connect(boost::bind(RelayDoubleSpend, _1, _2, _3, doubleSpendFilter)); +} + + void RegisterWallet(CWalletInterface* pwalletIn) { g_signals.SyncTransaction.connect(boost::bind(&CWalletInterface::SyncTransaction, pwalletIn, _1, _2)); g_signals.EraseTransaction.connect(boost::bind(&CWalletInterface::EraseFromWallet, pwalletIn, _1)); @@ -824,6 +844,22 @@ int64_t GetMinFee(const CTransaction& tx, unsigned int nBytes, bool fAllowFree, return nMinFee; } +// Exponentially limit the rate of nSize flow to nLimit. nLimit unit is thousands-per-minute. +bool RateLimitExceeded(double& dCount, int64_t& nLastTime, int64_t nLimit, unsigned int nSize) +{ + static CCriticalSection csLimiter; + int64_t nNow = GetTime(); + + LOCK(csLimiter); + + // Use an exponentially decaying ~10-minute window: + dCount *= pow(1.0 - 1.0/600.0, (double)(nNow - nLastTime)); + nLastTime = nNow; + if (dCount >= nLimit*10*1000) + return true; + dCount += nSize; + return false; +} bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree, bool* pfMissingInputs, bool fRejectInsaneFee) @@ -858,9 +894,10 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa for (unsigned int i = 0; i < tx.vin.size(); i++) { COutPoint outpoint = tx.vin[i].prevout; - if (pool.mapNextTx.count(outpoint)) + // Does tx conflict with a member of the pool, and is it not equivalent to that member? + if (pool.mapNextTx.count(outpoint) && !tx.IsEquivalentTo(*pool.mapNextTx[outpoint].ptx)) { - // Disable replacement feature for now + g_signals.DetectedDoubleSpend(outpoint, tx, false); return false; } } @@ -932,23 +969,15 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa // be annoying or make others' transactions take longer to confirm. if (fLimitFree && nFees < CTransaction::minRelayTxFee.GetFee(nSize)) { - static CCriticalSection csFreeLimiter; static double dFreeCount; - static int64_t nLastTime; - int64_t nNow = GetTime(); - - LOCK(csFreeLimiter); + static int64_t nLastFreeTime; + static int64_t nFreeLimit = GetArg("-limitfreerelay", 15); - // Use an exponentially decaying ~10-minute window: - dFreeCount *= pow(1.0 - 1.0/600.0, (double)(nNow - nLastTime)); - nLastTime = nNow; - // -limitfreerelay unit is thousand-bytes-per-minute - // At default rate it would take over a month to fill 1GB - if (dFreeCount >= GetArg("-limitfreerelay", 15)*10*1000) + if (RateLimitExceeded(dFreeCount, nLastFreeTime, nFreeLimit, nSize)) return state.DoS(0, error("AcceptToMemoryPool : free transaction rejected by rate limiter"), REJECT_INSUFFICIENTFEE, "insufficient priority"); + LogPrint("mempool", "Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize); - dFreeCount += nSize; } if (fRejectInsaneFee && nFees > CTransaction::minRelayTxFee.GetFee(nSize) * 10000) @@ -971,6 +1000,49 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa return true; } +static void +RelayDoubleSpend(const COutPoint& outPoint, const CTransaction& doubleSpend, bool fInBlock, CBloomFilter& filter) +{ + // Relaying double-spend attempts to our peers lets them detect when + // somebody might be trying to cheat them. However, blindly relaying + // every double-spend across the entire network gives attackers + // a denial-of-service attack: just generate a stream of double-spends + // re-spending the same (limited) set of outpoints owned by the attacker. + // So, we use a bloom filter and only relay (at most) the first double + // spend for each outpoint. False-positives ("we have already relayed") + // are OK, because if the peer doesn't hear about the double-spend + // from us they are very likely to hear about it from another peer, since + // each peer uses a different, randomized bloom filter. + + if (fInBlock || filter.contains(outPoint)) return; + + // Apply an independent rate limit to double-spend relays + static double dRespendCount; + static int64_t nLastRespendTime; + static int64_t nRespendLimit = GetArg("-limitrespendrelay", 100); + unsigned int nSize = ::GetSerializeSize(doubleSpend, SER_NETWORK, PROTOCOL_VERSION); + + if (RateLimitExceeded(dRespendCount, nLastRespendTime, nRespendLimit, nSize)) + { + LogPrint("mempool", "Double-spend relay rejected by rate limiter\n"); + return; + } + + LogPrint("mempool", "Rate limit dRespendCount: %g => %g\n", dRespendCount, dRespendCount+nSize); + + // Clear the filter on average every MAX_DOUBLE_SPEND_BLOOM + // insertions + if (insecure_rand()%MAX_DOUBLESPEND_BLOOM == 0) + filter.clear(); + + filter.insert(outPoint); + + RelayTransaction(doubleSpend); + + // Share conflict with wallet + g_signals.SyncTransaction(doubleSpend, NULL); +} + int CMerkleTx::GetDepthInMainChainINTERNAL(CBlockIndex* &pindexRet) const { diff --git a/src/main.h b/src/main.h index 0332db2163..c7f3dc4388 100644 --- a/src/main.h +++ b/src/main.h @@ -108,6 +108,9 @@ struct CNodeStateStats; struct CBlockTemplate; +/** Set up internal signal handlers **/ +void RegisterInternalSignals(); + /** Register a wallet to receive updates from core */ void RegisterWallet(CWalletInterface* pwalletIn); /** Unregister a wallet from core */ diff --git a/src/txmempool.cpp b/src/txmempool.cpp index 52f82ef040..97a426dd35 100644 --- a/src/txmempool.cpp +++ b/src/txmempool.cpp @@ -415,7 +415,6 @@ void CTxMemPool::remove(const CTransaction &tx, std::list<CTransaction>& removed void CTxMemPool::removeConflicts(const CTransaction &tx, std::list<CTransaction>& removed) { // Remove transactions which depend on inputs of tx, recursively - list<CTransaction> result; LOCK(cs); BOOST_FOREACH(const CTxIn &txin, tx.vin) { std::map<COutPoint, CInPoint>::iterator it = mapNextTx.find(txin.prevout); |