diff options
Diffstat (limited to 'src/validation.cpp')
| -rw-r--r-- | src/validation.cpp | 35 |
1 files changed, 26 insertions, 9 deletions
diff --git a/src/validation.cpp b/src/validation.cpp index 3faa1bf005..69aa018730 100644 --- a/src/validation.cpp +++ b/src/validation.cpp @@ -78,6 +78,7 @@ uint64_t nPruneTarget = 0; int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE; bool fEnableReplacement = DEFAULT_ENABLE_REPLACEMENT; +uint256 hashAssumeValid; CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE); CAmount maxTxFee = DEFAULT_TRANSACTION_MAXFEE; @@ -1389,11 +1390,10 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsVi // Only if ALL inputs pass do we perform expensive ECDSA signature checks. // Helps prevent CPU exhaustion attacks. - // Skip ECDSA signature verification when connecting blocks before the - // last block chain checkpoint. Assuming the checkpoints are valid this + // Skip script verification when connecting blocks under the + // assumedvalid block. Assuming the assumedvalid block is valid this // is safe because block merkle hashes are still computed and checked, - // and any change will be caught at the next checkpoint. Of course, if - // the checkpoint is for a chain that's invalid due to false scriptSigs + // Of course, if an assumed valid block is invalid due to false scriptSigs // this optimization would allow an invalid chain to be accepted. if (fScriptChecks) { for (unsigned int i = 0; i < tx.vin.size(); i++) { @@ -1721,11 +1721,28 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin } bool fScriptChecks = true; - if (fCheckpointsEnabled) { - CBlockIndex *pindexLastCheckpoint = Checkpoints::GetLastCheckpoint(chainparams.Checkpoints()); - if (pindexLastCheckpoint && pindexLastCheckpoint->GetAncestor(pindex->nHeight) == pindex) { - // This block is an ancestor of a checkpoint: disable script checks - fScriptChecks = false; + if (!hashAssumeValid.IsNull()) { + // We've been configured with the hash of a block which has been externally verified to have a valid history. + // A suitable default value is included with the software and updated from time to time. Because validity + // relative to a piece of software is an objective fact these defaults can be easily reviewed. + // This setting doesn't force the selection of any particular chain but makes validating some faster by + // effectively caching the result of part of the verification. + BlockMap::const_iterator it = mapBlockIndex.find(hashAssumeValid); + if (it != mapBlockIndex.end()) { + if (it->second->GetAncestor(pindex->nHeight) == pindex && + pindexBestHeader->GetAncestor(pindex->nHeight) == pindex && + pindexBestHeader->nChainWork >= UintToArith256(chainparams.GetConsensus().nMinimumChainWork)) { + // This block is a member of the assumed verified chain and an ancestor of the best header. + // The equivalent time check discourages hashpower from extorting the network via DOS attack + // into accepting an invalid block through telling users they must manually set assumevalid. + // Requiring a software change or burying the invalid block, regardless of the setting, makes + // it hard to hide the implication of the demand. This also avoids having release candidates + // that are hardly doing any signature verification at all in testing without having to + // artificially set the default assumed verified block further back. + // The test against nMinimumChainWork prevents the skipping when denied access to any chain at + // least as good as the expected chain. + fScriptChecks = (GetBlockProofEquivalentTime(*pindexBestHeader, *pindex, *pindexBestHeader, chainparams.GetConsensus()) <= 60 * 60 * 24 * 7 * 2); + } } } |