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Refactored ConnectInputs, so valid-transaction-checks are done before ECDSA-verifying signatures.

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This commit is contained in:
Gavin Andresen
2012-01-10 20:18:00 -05:00
parent 922e8e2929
commit 8d7849b6db
3 changed files with 256 additions and 65 deletions
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167
src/main.cpp
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@@ -275,26 +275,22 @@ bool CTransaction::IsStandard() const
// expensive-to-check-upon-redemption script like:
// DUP CHECKSIG DROP ... repeated 100 times... OP_1
//
bool CTransaction::AreInputsStandard(const std::map<uint256, std::pair<CTxIndex, CTransaction> >& mapInputs) const
bool CTransaction::AreInputsStandard(const MapPrevTx& mapInputs) const
{
if (fTestNet)
return true; // Allow non-standard on testnet
if (IsCoinBase())
return true; // Coinbases are allowed to have any input
for (int i = 0; i < vin.size(); i++)
{
COutPoint prevout = vin[i].prevout;
std::map<uint256, std::pair<CTxIndex, CTransaction> >::const_iterator mi = mapInputs.find(prevout.hash);
if (mi == mapInputs.end())
return false;
const CTransaction& txPrev = (mi->second).second;
assert(prevout.n < txPrev.vout.size());
const CTxOut& prev = GetOutputFor(vin[i], mapInputs);
vector<vector<unsigned char> > vSolutions;
txnouttype whichType;
// get the scriptPubKey corresponding to this input:
const CScript& prevScript = txPrev.vout[prevout.n].scriptPubKey;
const CScript& prevScript = prev.scriptPubKey;
if (!Solver(prevScript, whichType, vSolutions))
return false;
if (whichType == TX_SCRIPTHASH)
@@ -494,7 +490,7 @@ bool CTransaction::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs, bool* pfMi
if (fCheckInputs)
{
map<uint256, pair<CTxIndex, CTransaction> > mapInputs;
MapPrevTx mapInputs;
map<uint256, CTxIndex> mapUnused;
if (!FetchInputs(txdb, mapUnused, false, false, mapInputs))
{
@@ -507,27 +503,20 @@ bool CTransaction::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs, bool* pfMi
if (!AreInputsStandard(mapInputs))
return error("AcceptToMemoryPool() : nonstandard transaction input");
// Check against previous transactions
int64 nFees = 0;
int nSigOps = 0;
if (!ConnectInputs(mapInputs, mapUnused, CDiskTxPos(1,1,1), pindexBest, nFees, false, false, nSigOps))
{
if (pfMissingInputs)
*pfMissingInputs = true;
return error("AcceptToMemoryPool() : ConnectInputs failed %s", hash.ToString().substr(0,10).c_str());
}
// Checking ECDSA signatures is a CPU bottleneck, so to avoid denial-of-service
// attacks disallow transactions with more than one SigOp per 65 bytes.
// 65 bytes because that is the minimum size of an ECDSA signature
int64 nFees = GetValueIn(mapInputs)-GetValueOut();
int nSigOps = GetSigOpCount(mapInputs);
unsigned int nSize = ::GetSerializeSize(*this, SER_NETWORK);
if (nSigOps > nSize / 65 || nSize < 100)
return error("AcceptToMemoryPool() : transaction with out-of-bounds SigOpCount");
// Don't accept it if it can't get into a block
if (nFees < GetMinFee(1000, true, GMF_RELAY))
return error("AcceptToMemoryPool() : not enough fees");
// Checking ECDSA signatures is a CPU bottleneck, so to avoid denial-of-service
// attacks disallow transactions with more than one SigOp per 65 bytes.
// 65 bytes because that is the minimum size of an ECDSA signature
if (nSigOps > nSize / 65 || nSize < 100)
return error("AcceptToMemoryPool() : transaction with out-of-bounds SigOpCount");
// Continuously rate-limit free transactions
// This mitigates 'penny-flooding' -- sending thousands of free transactions just to
// be annoying or make other's transactions take longer to confirm.
@@ -552,6 +541,15 @@ bool CTransaction::AcceptToMemoryPool(CTxDB& txdb, bool fCheckInputs, bool* pfMi
dFreeCount += nSize;
}
}
// Check against previous transactions
// This is done last to help prevent CPU exhaustion denial-of-service attacks.
if (!ConnectInputs(mapInputs, mapUnused, CDiskTxPos(1,1,1), pindexBest, false, false))
{
if (pfMissingInputs)
*pfMissingInputs = true;
return error("AcceptToMemoryPool() : ConnectInputs failed %s", hash.ToString().substr(0,10).c_str());
}
}
// Store transaction in memory
@@ -925,7 +923,7 @@ bool CTransaction::DisconnectInputs(CTxDB& txdb)
bool CTransaction::FetchInputs(CTxDB& txdb, const map<uint256, CTxIndex>& mapTestPool,
bool fBlock, bool fMiner, map<uint256, pair<CTxIndex, CTransaction> >& inputsRet)
bool fBlock, bool fMiner, MapPrevTx& inputsRet)
{
if (IsCoinBase())
return true; // Coinbase transactions have no inputs to fetch.
@@ -978,6 +976,7 @@ bool CTransaction::FetchInputs(CTxDB& txdb, const map<uint256, CTxIndex>& mapTes
for (int i = 0; i < vin.size(); i++)
{
const COutPoint prevout = vin[i].prevout;
assert(inputsRet.count(prevout.hash) != 0);
const CTxIndex& txindex = inputsRet[prevout.hash].first;
const CTransaction& txPrev = inputsRet[prevout.hash].second;
if (prevout.n >= txPrev.vout.size() || prevout.n >= txindex.vSpent.size())
@@ -987,9 +986,49 @@ bool CTransaction::FetchInputs(CTxDB& txdb, const map<uint256, CTxIndex>& mapTes
return true;
}
bool CTransaction::ConnectInputs(map<uint256, pair<CTxIndex, CTransaction> > inputs,
const CTxOut& CTransaction::GetOutputFor(const CTxIn& input, const MapPrevTx& inputs) const
{
MapPrevTx::const_iterator mi = inputs.find(input.prevout.hash);
if (mi == inputs.end())
throw std::runtime_error("CTransaction::GetOutputFor() : prevout.hash not found");
const CTransaction& txPrev = (mi->second).second;
if (input.prevout.n >= txPrev.vout.size())
throw std::runtime_error("CTransaction::GetOutputFor() : prevout.n out of range");
return txPrev.vout[input.prevout.n];
}
int64 CTransaction::GetValueIn(const MapPrevTx& inputs) const
{
if (IsCoinBase())
return 0;
int64 nResult = 0;
for (int i = 0; i < vin.size(); i++)
{
nResult += GetOutputFor(vin[i], inputs).nValue;
}
return nResult;
}
int CTransaction::GetSigOpCount(const MapPrevTx& inputs) const
{
if (IsCoinBase())
return 0;
int nSigOps = 0;
for (int i = 0; i < vin.size(); i++)
{
nSigOps += GetOutputFor(vin[i], inputs).scriptPubKey.GetSigOpCount(vin[i].scriptSig);
}
return nSigOps;
}
bool CTransaction::ConnectInputs(MapPrevTx inputs,
map<uint256, CTxIndex>& mapTestPool, const CDiskTxPos& posThisTx,
const CBlockIndex* pindexBlock, int64& nFees, bool fBlock, bool fMiner, int& nSigOpsRet, int64 nMinFee)
const CBlockIndex* pindexBlock, bool fBlock, bool fMiner)
{
// Take over previous transactions' spent pointers
// fBlock is true when this is called from AcceptBlock when a new best-block is added to the blockchain
@@ -998,6 +1037,7 @@ bool CTransaction::ConnectInputs(map<uint256, pair<CTxIndex, CTransaction> > inp
if (!IsCoinBase())
{
int64 nValueIn = 0;
int64 nFees = 0;
for (int i = 0; i < vin.size(); i++)
{
COutPoint prevout = vin[i].prevout;
@@ -1014,6 +1054,17 @@ bool CTransaction::ConnectInputs(map<uint256, pair<CTxIndex, CTransaction> > inp
if (pindex->nBlockPos == txindex.pos.nBlockPos && pindex->nFile == txindex.pos.nFile)
return error("ConnectInputs() : tried to spend coinbase at depth %d", pindexBlock->nHeight - pindex->nHeight);
// Check for conflicts (double-spend)
// This doesn't trigger the DoS code on purpose; if it did, it would make it easier
// for an attacker to attempt to split the network.
if (!txindex.vSpent[prevout.n].IsNull())
return fMiner ? false : error("ConnectInputs() : %s prev tx already used at %s", GetHash().ToString().substr(0,10).c_str(), txindex.vSpent[prevout.n].ToString().c_str());
// Check for negative or overflow input values
nValueIn += txPrev.vout[prevout.n].nValue;
if (!MoneyRange(txPrev.vout[prevout.n].nValue) || !MoneyRange(nValueIn))
return DoS(100, error("ConnectInputs() : txin values out of range"));
bool fStrictPayToScriptHash = true;
if (fBlock)
{
@@ -1038,20 +1089,6 @@ bool CTransaction::ConnectInputs(map<uint256, pair<CTxIndex, CTransaction> > inp
return DoS(100,error("ConnectInputs() : %s VerifySignature failed", GetHash().ToString().substr(0,10).c_str()));
}
// Check for conflicts (double-spend)
// This doesn't trigger the DoS code on purpose; if it did, it would make it easier
// for an attacker to attempt to split the network.
if (!txindex.vSpent[prevout.n].IsNull())
return fMiner ? false : error("ConnectInputs() : %s prev tx already used at %s", GetHash().ToString().substr(0,10).c_str(), txindex.vSpent[prevout.n].ToString().c_str());
// Check for negative or overflow input values
nValueIn += txPrev.vout[prevout.n].nValue;
if (!MoneyRange(txPrev.vout[prevout.n].nValue) || !MoneyRange(nValueIn))
return DoS(100, error("ConnectInputs() : txin values out of range"));
// Calculate sigOps accurately:
nSigOpsRet += txPrev.vout[prevout.n].scriptPubKey.GetSigOpCount(vin[i].scriptSig);
// Mark outpoints as spent
txindex.vSpent[prevout.n] = posThisTx;
@@ -1069,8 +1106,6 @@ bool CTransaction::ConnectInputs(map<uint256, pair<CTxIndex, CTransaction> > inp
int64 nTxFee = nValueIn - GetValueOut();
if (nTxFee < 0)
return DoS(100, error("ConnectInputs() : %s nTxFee < 0", GetHash().ToString().substr(0,10).c_str()));
if (nTxFee < nMinFee)
return false;
nFees += nTxFee;
if (!MoneyRange(nFees))
return DoS(100, error("ConnectInputs() : nFees out of range"));
@@ -1176,20 +1211,27 @@ bool CBlock::ConnectBlock(CTxDB& txdb, CBlockIndex* pindex)
CDiskTxPos posThisTx(pindex->nFile, pindex->nBlockPos, nTxPos);
nTxPos += ::GetSerializeSize(tx, SER_DISK);
map<uint256, pair<CTxIndex, CTransaction> > mapInputs;
if (!tx.FetchInputs(txdb, mapQueuedChanges, true, false, mapInputs))
return false;
MapPrevTx mapInputs;
if (!tx.IsCoinBase())
{
if (!tx.FetchInputs(txdb, mapQueuedChanges, true, false, mapInputs))
return false;
int nTxOps = 0;
if (!tx.ConnectInputs(mapInputs, mapQueuedChanges, posThisTx, pindex, nFees, true, false, nTxOps))
return false;
int nTxOps = tx.GetSigOpCount(mapInputs);
nSigOps += nTxOps;
if (nSigOps > MAX_BLOCK_SIGOPS)
return DoS(100, error("ConnectBlock() : too many sigops"));
// There is a different MAX_BLOCK_SIGOPS check in AcceptBlock();
// a block must satisfy both to make it into the best-chain
// (AcceptBlock() is always called before ConnectBlock())
nSigOps += nTxOps;
if (nSigOps > MAX_BLOCK_SIGOPS)
return DoS(100, error("ConnectBlock() : too many sigops"));
// There is a different MAX_BLOCK_SIGOPS check in AcceptBlock();
// a block must satisfy both to make it into the best-chain
// (AcceptBlock() is always called before ConnectBlock())
nFees += tx.GetValueIn(mapInputs)-tx.GetValueOut();
}
// It seems wrong that ConnectInputs must be called on the coinbase transaction
// (which has no inputs) : TODO: refactor the code at the end of ConnectInputs out...
if (!tx.ConnectInputs(mapInputs, mapQueuedChanges, posThisTx, pindex, true, false))
return false;
}
// Write queued txindex changes
@@ -3031,15 +3073,20 @@ CBlock* CreateNewBlock(CReserveKey& reservekey)
// Connecting shouldn't fail due to dependency on other memory pool transactions
// because we're already processing them in order of dependency
map<uint256, CTxIndex> mapTestPoolTmp(mapTestPool);
map<uint256, pair<CTxIndex, CTransaction> > mapInputs;
MapPrevTx mapInputs;
if (!tx.FetchInputs(txdb, mapTestPoolTmp, false, true, mapInputs))
continue;
int nTxSigOps2 = 0;
if (!tx.ConnectInputs(mapInputs, mapTestPoolTmp, CDiskTxPos(1,1,1), pindexPrev, nFees, false, true, nTxSigOps2, nMinFee))
int64 nFees = tx.GetValueIn(mapInputs)-tx.GetValueOut();
if (nFees < nMinFee)
continue;
int nTxSigOps2 = tx.GetSigOpCount(mapInputs);
if (nBlockSigOps2 + nTxSigOps2 >= MAX_BLOCK_SIGOPS)
continue;
if (!tx.ConnectInputs(mapInputs, mapTestPoolTmp, CDiskTxPos(1,1,1), pindexPrev, false, true))
continue;
swap(mapTestPool, mapTestPoolTmp);
// Added