From 8b49040854be2e26b66366aeae1cba4716f93d93 Mon Sep 17 00:00:00 2001 From: Pieter Wuille Date: Fri, 6 Nov 2015 01:42:38 +0100 Subject: BIP141: Commitment structure and deployment Includes a fix by Suhas Daftuar and LongShao007 --- src/main.cpp | 146 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 138 insertions(+), 8 deletions(-) (limited to 'src/main.cpp') diff --git a/src/main.cpp b/src/main.cpp index d1945a5094..8d91d6d625 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -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 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 GenerateCoinbaseCommitment(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams) +{ + std::vector 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 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(out.scriptPubKey.begin(), out.scriptPubKey.end()); + const_cast*>(&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); } -- cgit v1.2.3