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BIP141: Commitment structure and deployment

Includes a fix by Suhas Daftuar and LongShao007
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sipa committed Nov 6, 2015
1 parent 449f9b8 commit 8b49040854be2e26b66366aeae1cba4716f93d93
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@@ -92,6 +92,11 @@ class CMainParams : public CChainParams {
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 1462060800; // May 1st, 2016
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 1493596800; // May 1st, 2017
// Deployment of SegWit (BIP141 and BIP143)
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].bit = 1;
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = 0;
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = 0; // Never / undefined
/**
* The message start string is designed to be unlikely to occur in normal data.
* The characters are rarely used upper ASCII, not valid as UTF-8, and produce
@@ -183,6 +188,11 @@ class CTestNetParams : public CChainParams {
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 1456790400; // March 1st, 2016
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 1493596800; // May 1st, 2017
// Deployment of SegWit (BIP141 and BIP143)
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].bit = 1;
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = 2000000000; // Far in the future
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = 2100000000;
pchMessageStart[0] = 0x0b;
pchMessageStart[1] = 0x11;
pchMessageStart[2] = 0x09;
@@ -255,6 +265,9 @@ class CRegTestParams : public CChainParams {
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].bit = 0;
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nStartTime = 0;
consensus.vDeployments[Consensus::DEPLOYMENT_CSV].nTimeout = 999999999999ULL;
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].bit = 1;
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nStartTime = 0;
consensus.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout = 999999999999ULL;
pchMessageStart[0] = 0xfa;
pchMessageStart[1] = 0xbf;
@@ -317,3 +330,4 @@ void SelectParams(const std::string& network)
SelectBaseParams(network);
pCurrentParams = &Params(network);
}
View
@@ -165,6 +165,17 @@ uint256 BlockMerkleRoot(const CBlock& block, bool* mutated)
return ComputeMerkleRoot(leaves, mutated);
}
uint256 BlockWitnessMerkleRoot(const CBlock& block, bool* mutated)
{
std::vector<uint256> leaves;
leaves.resize(block.vtx.size());
leaves[0].SetNull(); // The witness hash of the coinbase is 0.
for (size_t s = 1; s < block.vtx.size(); s++) {
leaves[s] = block.vtx[s].GetWitnessHash();
}
return ComputeMerkleRoot(leaves, mutated);
}
std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position)
{
std::vector<uint256> leaves;
View
@@ -22,6 +22,12 @@ uint256 ComputeMerkleRootFromBranch(const uint256& leaf, const std::vector<uint2
*/
uint256 BlockMerkleRoot(const CBlock& block, bool* mutated = NULL);
/*
* Compute the Merkle root of the witness transactions in a block.
* *mutated is set to true if a duplicated subtree was found.
*/
uint256 BlockWitnessMerkleRoot(const CBlock& block, bool* mutated = NULL);
/*
* Compute the Merkle branch for the tree of transactions in a block, for a
* given position.
View
@@ -16,6 +16,7 @@ enum DeploymentPos
{
DEPLOYMENT_TESTDUMMY,
DEPLOYMENT_CSV, // Deployment of BIP68, BIP112, and BIP113.
DEPLOYMENT_SEGWIT, // Deployment of BIP141 and BIP143
// NOTE: Also add new deployments to VersionBitsDeploymentInfo in versionbits.cpp
MAX_VERSION_BITS_DEPLOYMENTS
};
@@ -77,6 +77,9 @@ class CValidationState {
bool CorruptionPossible() const {
return corruptionPossible;
}
void SetCorruptionPossible() {
corruptionPossible = true;
}
unsigned int GetRejectCode() const { return chRejectCode; }
std::string GetRejectReason() const { return strRejectReason; }
std::string GetDebugMessage() const { return strDebugMessage; }
View
@@ -293,6 +293,8 @@ struct CNodeState {
bool fPreferHeaderAndIDs;
//! Whether this peer will send us cmpctblocks if we request them
bool fProvidesHeaderAndIDs;
//! Whether this peer can give us witnesses
bool fHaveWitness;
CNodeState() {
fCurrentlyConnected = false;
@@ -1119,6 +1121,11 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
return state.DoS(0, false, REJECT_NONSTANDARD, "premature-version2-tx");
}
// Don't accept witness transactions before the final threshold passes
if (!tx.wit.IsNull() && !IsWitnessEnabled(chainActive.Tip(), Params().GetConsensus())) {
return state.DoS(0, false, REJECT_NONSTANDARD, "no-witness-yet", true);
}
// Only accept nLockTime-using transactions that can be mined in the next
// block; we don't want our mempool filled up with transactions that can't
// be mined yet.
@@ -1459,8 +1466,17 @@ bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState& state, const C
// Check against previous transactions
// This is done last to help prevent CPU exhaustion denial-of-service attacks.
if (!CheckInputs(tx, state, view, true, STANDARD_SCRIPT_VERIFY_FLAGS, true))
return false; // state filled in by CheckInputs
if (!CheckInputs(tx, state, view, true, STANDARD_SCRIPT_VERIFY_FLAGS, true)) {
// SCRIPT_VERIFY_CLEANSTACK requires SCRIPT_VERIFY_WITNESS, so we
// need to turn both off, and compare against just turning off CLEANSTACK
// to see if the failure is specifically due to witness validation.
if (CheckInputs(tx, state, view, true, STANDARD_SCRIPT_VERIFY_FLAGS & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true) &&
!CheckInputs(tx, state, view, true, STANDARD_SCRIPT_VERIFY_FLAGS & ~SCRIPT_VERIFY_CLEANSTACK, true)) {
// Only the witness is wrong, so the transaction itself may be fine.
state.SetCorruptionPossible();
}
return false;
}
// Check again against just the consensus-critical mandatory script
// verification flags, in case of bugs in the standard flags that cause
@@ -2406,6 +2422,11 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
nLockTimeFlags |= LOCKTIME_VERIFY_SEQUENCE;
}
// Start enforcing WITNESS rules using versionbits logic.
if (IsWitnessEnabled(pindex->pprev, chainparams.GetConsensus())) {
flags |= SCRIPT_VERIFY_WITNESS;
}
int64_t nTime2 = GetTimeMicros(); nTimeForks += nTime2 - nTime1;
LogPrint("bench", " - Fork checks: %.2fms [%.2fs]\n", 0.001 * (nTime2 - nTime1), nTimeForks * 0.000001);
@@ -3441,6 +3462,71 @@ static bool CheckIndexAgainstCheckpoint(const CBlockIndex* pindexPrev, CValidati
return true;
}
bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& params)
{
LOCK(cs_main);
return (VersionBitsState(pindexPrev, params, Consensus::DEPLOYMENT_SEGWIT, versionbitscache) == THRESHOLD_ACTIVE);
}
// Compute at which vout of the block's coinbase transaction the witness
// commitment occurs, or -1 if not found.
static int GetWitnessCommitmentIndex(const CBlock& block)
{
int commitpos = -1;
for (size_t o = 0; o < block.vtx[0].vout.size(); o++) {
if (block.vtx[0].vout[o].scriptPubKey.size() >= 38 && block.vtx[0].vout[o].scriptPubKey[0] == OP_RETURN && block.vtx[0].vout[o].scriptPubKey[1] == 0x24 && block.vtx[0].vout[o].scriptPubKey[2] == 0xaa && block.vtx[0].vout[o].scriptPubKey[3] == 0x21 && block.vtx[0].vout[o].scriptPubKey[4] == 0xa9 && block.vtx[0].vout[o].scriptPubKey[5] == 0xed) {
commitpos = o;
}
}
return commitpos;
}
void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams)
{
int commitpos = GetWitnessCommitmentIndex(block);
static const std::vector<unsigned char> nonce(32, 0x00);
if (commitpos != -1 && IsWitnessEnabled(pindexPrev, consensusParams) && block.vtx[0].wit.IsEmpty()) {
block.vtx[0].wit.vtxinwit.resize(1);
block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.resize(1);
block.vtx[0].wit.vtxinwit[0].scriptWitness.stack[0] = nonce;
}
}
std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams)
{
std::vector<unsigned char> commitment;
int commitpos = GetWitnessCommitmentIndex(block);
bool fHaveWitness = false;
for (size_t t = 1; t < block.vtx.size(); t++) {
if (!block.vtx[t].wit.IsNull()) {
fHaveWitness = true;
break;
}
}
std::vector<unsigned char> ret(32, 0x00);
if (fHaveWitness && IsWitnessEnabled(pindexPrev, consensusParams)) {
if (commitpos == -1) {
uint256 witnessroot = BlockWitnessMerkleRoot(block, NULL);
CHash256().Write(witnessroot.begin(), 32).Write(&ret[0], 32).Finalize(witnessroot.begin());
CTxOut out;
out.nValue = 0;
out.scriptPubKey.resize(38);
out.scriptPubKey[0] = OP_RETURN;
out.scriptPubKey[1] = 0x24;
out.scriptPubKey[2] = 0xaa;
out.scriptPubKey[3] = 0x21;
out.scriptPubKey[4] = 0xa9;
out.scriptPubKey[5] = 0xed;
memcpy(&out.scriptPubKey[6], witnessroot.begin(), 32);
commitment = std::vector<unsigned char>(out.scriptPubKey.begin(), out.scriptPubKey.end());
const_cast<std::vector<CTxOut>*>(&block.vtx[0].vout)->push_back(out);
block.vtx[0].UpdateHash();
}
}
UpdateUncommittedBlockStructures(block, pindexPrev, consensusParams);
return commitment;
}
bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& state, const Consensus::Params& consensusParams, CBlockIndex * const pindexPrev, int64_t nAdjustedTime)
{
// Check proof of work
@@ -3497,6 +3583,43 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, CBlockIn
}
}
// Validation for witness commitments.
// * We compute the witness hash (which is the hash including witnesses) of all the block's transactions, except the
// coinbase (where 0x0000....0000 is used instead).
// * The coinbase scriptWitness is a stack of a single 32-byte vector, containing a witness nonce (unconstrained).
// * We build a merkle tree with all those witness hashes as leaves (similar to the hashMerkleRoot in the block header).
// * There must be at least one output whose scriptPubKey is a single 36-byte push, the first 4 bytes of which are
// {0xaa, 0x21, 0xa9, 0xed}, and the following 32 bytes are SHA256^2(witness root, witness nonce). In case there are
// multiple, the last one is used.
bool fHaveWitness = false;
if (IsWitnessEnabled(pindexPrev, consensusParams)) {
int commitpos = GetWitnessCommitmentIndex(block);
if (commitpos != -1) {
bool malleated = false;
uint256 hashWitness = BlockWitnessMerkleRoot(block, &malleated);
// The malleation check is ignored; as the transaction tree itself
// already does not permit it, it is impossible to trigger in the
// witness tree.
if (block.vtx[0].wit.vtxinwit.size() != 1 || block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.size() != 1 || block.vtx[0].wit.vtxinwit[0].scriptWitness.stack[0].size() != 32) {
return state.DoS(100, error("%s : invalid witness nonce size", __func__), REJECT_INVALID, "bad-witness-nonce-size", true);
}
CHash256().Write(hashWitness.begin(), 32).Write(&block.vtx[0].wit.vtxinwit[0].scriptWitness.stack[0][0], 32).Finalize(hashWitness.begin());
if (memcmp(hashWitness.begin(), &block.vtx[0].vout[commitpos].scriptPubKey[6], 32)) {
return state.DoS(100, error("%s : witness merkle commitment mismatch", __func__), REJECT_INVALID, "bad-witness-merkle-match", true);
}
fHaveWitness = true;
}
}
// No witness data is allowed in blocks that don't commit to witness data, as this would otherwise leave room for spam
if (!fHaveWitness) {
for (size_t i = 0; i < block.vtx.size(); i++) {
if (!block.vtx[i].wit.IsNull()) {
return state.DoS(100, error("%s : unexpected witness data found", __func__), REJECT_INVALID, "unexpected-witness", true);
}
}
}
return true;
}
@@ -5278,7 +5401,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
else if (!fMissingInputs2)
{
int nDos = 0;
if (stateDummy.IsInvalid(nDos) && nDos > 0)
if (stateDummy.IsInvalid(nDos) && nDos > 0 && (!state.CorruptionPossible() || State(fromPeer)->fHaveWitness))
{
// Punish peer that gave us an invalid orphan tx
Misbehaving(fromPeer, nDos);
@@ -5289,8 +5412,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
// Probably non-standard or insufficient fee/priority
LogPrint("mempool", " removed orphan tx %s\n", orphanHash.ToString());
vEraseQueue.push_back(orphanHash);
assert(recentRejects);
recentRejects->insert(orphanHash);
if (!stateDummy.CorruptionPossible()) {
assert(recentRejects);
recentRejects->insert(orphanHash);
}
}
mempool.check(pcoinsTip);
}
@@ -5325,8 +5450,10 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
LogPrint("mempool", "not keeping orphan with rejected parents %s\n",tx.GetHash().ToString());
}
} else {
assert(recentRejects);
recentRejects->insert(tx.GetHash());
if (!state.CorruptionPossible()) {
assert(recentRejects);
recentRejects->insert(tx.GetHash());
}
if (pfrom->fWhitelisted && GetBoolArg("-whitelistforcerelay", DEFAULT_WHITELISTFORCERELAY)) {
// Always relay transactions received from whitelisted peers, even
@@ -5355,8 +5482,11 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
if (state.GetRejectCode() < REJECT_INTERNAL) // Never send AcceptToMemoryPool's internal codes over P2P
pfrom->PushMessage(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash);
if (nDoS > 0)
if (nDoS > 0 && (!state.CorruptionPossible() || State(pfrom->id)->fHaveWitness)) {
// When a non-witness-supporting peer gives us a transaction that would
// be accepted if witness validation was off, we can't blame them for it.
Misbehaving(pfrom->GetId(), nDoS);
}
}
FlushStateToDisk(state, FLUSH_STATE_PERIODIC);
}
View
@@ -453,6 +453,15 @@ bool DisconnectBlock(const CBlock& block, CValidationState& state, const CBlockI
/** Check a block is completely valid from start to finish (only works on top of our current best block, with cs_main held) */
bool TestBlockValidity(CValidationState& state, const CChainParams& chainparams, const CBlock& block, CBlockIndex* pindexPrev, bool fCheckPOW = true, bool fCheckMerkleRoot = true);
/** Check whether witness commitments are required for block. */
bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& params);
/** Update uncommitted block structures (currently: only the witness nonce). This is safe for submitted blocks. */
void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams);
/** Produce the necessary coinbase commitment for a block (modifies the hash, don't call for mined blocks). */
std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams);
/** RAII wrapper for VerifyDB: Verify consistency of the block and coin databases */
class CVerifyDB {
public:
View
@@ -93,6 +93,7 @@ void BlockAssembler::resetBlock()
// Reserve space for coinbase tx
nBlockSize = 1000;
nBlockSigOps = 100;
fIncludeWitness = false;
// These counters do not include coinbase tx
nBlockTx = 0;
@@ -134,6 +135,14 @@ CBlockTemplate* BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
? nMedianTimePast
: pblock->GetBlockTime();
// Decide whether to include witness transactions
// This is only needed in case the witness softfork activation is reverted
// (which would require a very deep reorganization) or when
// -promiscuousmempoolflags is used.
// TODO: replace this with a call to main to assess validity of a mempool
// transaction (which in most cases can be a no-op).
fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus());
addPriorityTxs();
addPackageTxs();
@@ -150,6 +159,7 @@ CBlockTemplate* BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
pblock->vtx[0] = coinbaseTx;
pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
pblocktemplate->vTxFees[0] = -nFees;
// Fill in header
@@ -299,6 +309,10 @@ void BlockAssembler::addScoreTxs()
continue;
}
// cannot accept witness transactions into a non-witness block
if (!fIncludeWitness && !iter->GetTx().wit.IsNull())
continue;
// If tx is dependent on other mempool txs which haven't yet been included
// then put it in the waitSet
if (isStillDependent(iter)) {
@@ -543,6 +557,10 @@ void BlockAssembler::addPriorityTxs()
continue;
}
// cannot accept witness transactions into a non-witness block
if (!fIncludeWitness && !iter->GetTx().wit.IsNull())
continue;
// If tx is dependent on other mempool txs which haven't yet been included
// then put it in the waitSet
if (isStillDependent(iter)) {
View
@@ -29,6 +29,7 @@ struct CBlockTemplate
CBlock block;
std::vector<CAmount> vTxFees;
std::vector<int64_t> vTxSigOps;
std::vector<unsigned char> vchCoinbaseCommitment;
};
// Container for tracking updates to ancestor feerate as we include (parent)
@@ -139,6 +140,7 @@ class BlockAssembler
CBlock* pblock;
// Configuration parameters for the block size
bool fIncludeWitness;
unsigned int nBlockMaxSize, nBlockMinSize;
// Information on the current status of the block
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