diff options
Diffstat (limited to 'src/main.cpp')
| -rw-r--r-- | src/main.cpp | 98 |
1 files changed, 84 insertions, 14 deletions
diff --git a/src/main.cpp b/src/main.cpp index 41125cb577..04d9523e26 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" @@ -124,6 +125,10 @@ namespace { } // anon namespace +// 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 @@ -146,10 +151,25 @@ 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; } // anon namespace +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)); @@ -872,6 +892,21 @@ 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); + + 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) @@ -906,9 +941,10 @@ 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; } } @@ -980,23 +1016,15 @@ 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) @@ -1019,6 +1047,48 @@ 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 { |