// Copyright 2017 The go-ethereum Authors // This file is part of the go-ethereum library. // // The go-ethereum library is free software: you can redistribute it and/or modify // it under the terms of the GNU Lesser General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // // The go-ethereum library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU Lesser General Public License for more details. // // You should have received a copy of the GNU Lesser General Public License // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>. package ethash import ( "bytes" "errors" "fmt" "math/big" "runtime" "time" "github.com/ava-labs/coreth/consensus" "github.com/ava-labs/coreth/consensus/misc" "github.com/ava-labs/coreth/core/state" "github.com/ava-labs/coreth/core/types" "github.com/ava-labs/coreth/params" "github.com/ava-labs/go-ethereum/common" "github.com/ava-labs/go-ethereum/common/math" "github.com/ava-labs/go-ethereum/rlp" mapset "github.com/deckarep/golang-set" "golang.org/x/crypto/sha3" ) // Ethash proof-of-work protocol constants. var ( FrontierBlockReward = big.NewInt(5e+18) // Block reward in wei for successfully mining a block ByzantiumBlockReward = big.NewInt(3e+18) // Block reward in wei for successfully mining a block upward from Byzantium ConstantinopleBlockReward = big.NewInt(2e+18) // Block reward in wei for successfully mining a block upward from Constantinople maxUncles = 2 // Maximum number of uncles allowed in a single block allowedFutureBlockTime = 15 * time.Second // Max time from current time allowed for blocks, before they're considered future blocks // calcDifficultyConstantinople is the difficulty adjustment algorithm for Constantinople. // It returns the difficulty that a new block should have when created at time given the // parent block's time and difficulty. The calculation uses the Byzantium rules, but with // bomb offset 5M. // Specification EIP-1234: https://eips.ethereum.org/EIPS/eip-1234 calcDifficultyConstantinople = makeDifficultyCalculator(big.NewInt(5000000)) // calcDifficultyByzantium is the difficulty adjustment algorithm. It returns // the difficulty that a new block should have when created at time given the // parent block's time and difficulty. The calculation uses the Byzantium rules. // Specification EIP-649: https://eips.ethereum.org/EIPS/eip-649 calcDifficultyByzantium = makeDifficultyCalculator(big.NewInt(3000000)) ) // Various error messages to mark blocks invalid. These should be private to // prevent engine specific errors from being referenced in the remainder of the // codebase, inherently breaking if the engine is swapped out. Please put common // error types into the consensus package. var ( errZeroBlockTime = errors.New("timestamp equals parent's") errTooManyUncles = errors.New("too many uncles") errDuplicateUncle = errors.New("duplicate uncle") errUncleIsAncestor = errors.New("uncle is ancestor") errDanglingUncle = errors.New("uncle's parent is not ancestor") errInvalidDifficulty = errors.New("non-positive difficulty") errInvalidMixDigest = errors.New("invalid mix digest") errInvalidPoW = errors.New("invalid proof-of-work") ) // Author implements consensus.Engine, returning the header's coinbase as the // proof-of-work verified author of the block. func (ethash *Ethash) Author(header *types.Header) (common.Address, error) { return header.Coinbase, nil } // VerifyHeader checks whether a header conforms to the consensus rules of the // stock Ethereum ethash engine. func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error { // If we're running a full engine faking, accept any input as valid if ethash.config.PowMode == ModeFullFake { return nil } // Short circuit if the header is known, or it's parent not number := header.Number.Uint64() if chain.GetHeader(header.Hash(), number) != nil { return nil } parent := chain.GetHeader(header.ParentHash, number-1) if parent == nil { return consensus.ErrUnknownAncestor } // Sanity checks passed, do a proper verification return ethash.verifyHeader(chain, header, parent, false, seal) } // VerifyHeaders is similar to VerifyHeader, but verifies a batch of headers // concurrently. The method returns a quit channel to abort the operations and // a results channel to retrieve the async verifications. func (ethash *Ethash) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) { // If we're running a full engine faking, accept any input as valid if ethash.config.PowMode == ModeFullFake || len(headers) == 0 { abort, results := make(chan struct{}), make(chan error, len(headers)) for i := 0; i < len(headers); i++ { results <- nil } return abort, results } // Spawn as many workers as allowed threads workers := runtime.GOMAXPROCS(0) if len(headers) < workers { workers = len(headers) } // Create a task channel and spawn the verifiers var ( inputs = make(chan int) done = make(chan int, workers) errors = make([]error, len(headers)) abort = make(chan struct{}) ) for i := 0; i < workers; i++ { go func() { for index := range inputs { errors[index] = ethash.verifyHeaderWorker(chain, headers, seals, index) done <- index } }() } errorsOut := make(chan error, len(headers)) go func() { defer close(inputs) var ( in, out = 0, 0 checked = make([]bool, len(headers)) inputs = inputs ) for { select { case inputs <- in: if in++; in == len(headers) { // Reached end of headers. Stop sending to workers. inputs = nil } case index := <-done: for checked[index] = true; checked[out]; out++ { errorsOut <- errors[out] if out == len(headers)-1 { return } } case <-abort: return } } }() return abort, errorsOut } func (ethash *Ethash) verifyHeaderWorker(chain consensus.ChainReader, headers []*types.Header, seals []bool, index int) error { var parent *types.Header if index == 0 { parent = chain.GetHeader(headers[0].ParentHash, headers[0].Number.Uint64()-1) } else if headers[index-1].Hash() == headers[index].ParentHash { parent = headers[index-1] } if parent == nil { return consensus.ErrUnknownAncestor } if chain.GetHeader(headers[index].Hash(), headers[index].Number.Uint64()) != nil { return nil // known block } return ethash.verifyHeader(chain, headers[index], parent, false, seals[index]) } // VerifyUncles verifies that the given block's uncles conform to the consensus // rules of the stock Ethereum ethash engine. func (ethash *Ethash) VerifyUncles(chain consensus.ChainReader, block *types.Block) error { // If we're running a full engine faking, accept any input as valid if ethash.config.PowMode == ModeFullFake { return nil } // Verify that there are at most 2 uncles included in this block if len(block.Uncles()) > maxUncles { return errTooManyUncles } if len(block.Uncles()) == 0 { return nil } // Gather the set of past uncles and ancestors uncles, ancestors := mapset.NewSet(), make(map[common.Hash]*types.Header) number, parent := block.NumberU64()-1, block.ParentHash() for i := 0; i < 7; i++ { ancestor := chain.GetBlock(parent, number) if ancestor == nil { break } ancestors[ancestor.Hash()] = ancestor.Header() for _, uncle := range ancestor.Uncles() { uncles.Add(uncle.Hash()) } parent, number = ancestor.ParentHash(), number-1 } ancestors[block.Hash()] = block.Header() uncles.Add(block.Hash()) // Verify each of the uncles that it's recent, but not an ancestor for _, uncle := range block.Uncles() { // Make sure every uncle is rewarded only once hash := uncle.Hash() if uncles.Contains(hash) { return errDuplicateUncle } uncles.Add(hash) // Make sure the uncle has a valid ancestry if ancestors[hash] != nil { return errUncleIsAncestor } if ancestors[uncle.ParentHash] == nil || uncle.ParentHash == block.ParentHash() { return errDanglingUncle } if err := ethash.verifyHeader(chain, uncle, ancestors[uncle.ParentHash], true, true); err != nil { return err } } return nil } // verifyHeader checks whether a header conforms to the consensus rules of the // stock Ethereum ethash engine. // See YP section 4.3.4. "Block Header Validity" func (ethash *Ethash) verifyHeader(chain consensus.ChainReader, header, parent *types.Header, uncle bool, seal bool) error { // Ensure that the header's extra-data section is of a reasonable size if uint64(len(header.Extra)) > params.MaximumExtraDataSize { return fmt.Errorf("extra-data too long: %d > %d", len(header.Extra), params.MaximumExtraDataSize) } // Verify the header's timestamp if !uncle { if header.Time > uint64(time.Now().Add(allowedFutureBlockTime).Unix()) { return consensus.ErrFutureBlock } } if header.Time <= parent.Time { return errZeroBlockTime } // Verify the block's difficulty based in it's timestamp and parent's difficulty expected := ethash.CalcDifficulty(chain, header.Time, parent) if expected.Cmp(header.Difficulty) != 0 { return fmt.Errorf("invalid difficulty: have %v, want %v", header.Difficulty, expected) } // Verify that the gas limit is <= 2^63-1 cap := uint64(0x7fffffffffffffff) if header.GasLimit > cap { return fmt.Errorf("invalid gasLimit: have %v, max %v", header.GasLimit, cap) } // Verify that the gasUsed is <= gasLimit if header.GasUsed > header.GasLimit { return fmt.Errorf("invalid gasUsed: have %d, gasLimit %d", header.GasUsed, header.GasLimit) } // Verify that the gas limit remains within allowed bounds diff := int64(parent.GasLimit) - int64(header.GasLimit) if diff < 0 { diff *= -1 } limit := parent.GasLimit / params.GasLimitBoundDivisor if uint64(diff) >= limit || header.GasLimit < params.MinGasLimit { return fmt.Errorf("invalid gas limit: have %d, want %d += %d", header.GasLimit, parent.GasLimit, limit) } // Verify that the block number is parent's +1 if diff := new(big.Int).Sub(header.Number, parent.Number); diff.Cmp(big.NewInt(1)) != 0 { return consensus.ErrInvalidNumber } // Verify the engine specific seal securing the block if seal { if err := ethash.VerifySeal(chain, header); err != nil { return err } } // If all checks passed, validate any special fields for hard forks if err := misc.VerifyDAOHeaderExtraData(chain.Config(), header); err != nil { return err } if err := misc.VerifyForkHashes(chain.Config(), header, uncle); err != nil { return err } return nil } // CalcDifficulty is the difficulty adjustment algorithm. It returns // the difficulty that a new block should have when created at time // given the parent block's time and difficulty. func (ethash *Ethash) CalcDifficulty(chain consensus.ChainReader, time uint64, parent *types.Header) *big.Int { return CalcDifficulty(chain.Config(), time, parent) } // CalcDifficulty is the difficulty adjustment algorithm. It returns // the difficulty that a new block should have when created at time // given the parent block's time and difficulty. func CalcDifficulty(config *params.ChainConfig, time uint64, parent *types.Header) *big.Int { next := new(big.Int).Add(parent.Number, big1) switch { case config.IsConstantinople(next): return calcDifficultyConstantinople(time, parent) case config.IsByzantium(next): return calcDifficultyByzantium(time, parent) case config.IsHomestead(next): return calcDifficultyHomestead(time, parent) default: return calcDifficultyFrontier(time, parent) } } // Some weird constants to avoid constant memory allocs for them. var ( expDiffPeriod = big.NewInt(100000) big1 = big.NewInt(1) big2 = big.NewInt(2) big9 = big.NewInt(9) big10 = big.NewInt(10) bigMinus99 = big.NewInt(-99) ) // makeDifficultyCalculator creates a difficultyCalculator with the given bomb-delay. // the difficulty is calculated with Byzantium rules, which differs from Homestead in // how uncles affect the calculation func makeDifficultyCalculator(bombDelay *big.Int) func(time uint64, parent *types.Header) *big.Int { // Note, the calculations below looks at the parent number, which is 1 below // the block number. Thus we remove one from the delay given bombDelayFromParent := new(big.Int).Sub(bombDelay, big1) return func(time uint64, parent *types.Header) *big.Int { // https://github.com/ethereum/EIPs/issues/100. // algorithm: // diff = (parent_diff + // (parent_diff / 2048 * max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99)) // ) + 2^(periodCount - 2) bigTime := new(big.Int).SetUint64(time) bigParentTime := new(big.Int).SetUint64(parent.Time) // holds intermediate values to make the algo easier to read & audit x := new(big.Int) y := new(big.Int) // (2 if len(parent_uncles) else 1) - (block_timestamp - parent_timestamp) // 9 x.Sub(bigTime, bigParentTime) x.Div(x, big9) if parent.UncleHash == types.EmptyUncleHash { x.Sub(big1, x) } else { x.Sub(big2, x) } // max((2 if len(parent_uncles) else 1) - (block_timestamp - parent_timestamp) // 9, -99) if x.Cmp(bigMinus99) < 0 { x.Set(bigMinus99) } // parent_diff + (parent_diff / 2048 * max((2 if len(parent.uncles) else 1) - ((timestamp - parent.timestamp) // 9), -99)) y.Div(parent.Difficulty, params.DifficultyBoundDivisor) x.Mul(y, x) x.Add(parent.Difficulty, x) // minimum difficulty can ever be (before exponential factor) if x.Cmp(params.MinimumDifficulty) < 0 { x.Set(params.MinimumDifficulty) } // calculate a fake block number for the ice-age delay // Specification: https://eips.ethereum.org/EIPS/eip-1234 fakeBlockNumber := new(big.Int) if parent.Number.Cmp(bombDelayFromParent) >= 0 { fakeBlockNumber = fakeBlockNumber.Sub(parent.Number, bombDelayFromParent) } // for the exponential factor periodCount := fakeBlockNumber periodCount.Div(periodCount, expDiffPeriod) // the exponential factor, commonly referred to as "the bomb" // diff = diff + 2^(periodCount - 2) if periodCount.Cmp(big1) > 0 { y.Sub(periodCount, big2) y.Exp(big2, y, nil) x.Add(x, y) } return x } } // calcDifficultyHomestead is the difficulty adjustment algorithm. It returns // the difficulty that a new block should have when created at time given the // parent block's time and difficulty. The calculation uses the Homestead rules. func calcDifficultyHomestead(time uint64, parent *types.Header) *big.Int { // https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.md // algorithm: // diff = (parent_diff + // (parent_diff / 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99)) // ) + 2^(periodCount - 2) bigTime := new(big.Int).SetUint64(time) bigParentTime := new(big.Int).SetUint64(parent.Time) // holds intermediate values to make the algo easier to read & audit x := new(big.Int) y := new(big.Int) // 1 - (block_timestamp - parent_timestamp) // 10 x.Sub(bigTime, bigParentTime) x.Div(x, big10) x.Sub(big1, x) // max(1 - (block_timestamp - parent_timestamp) // 10, -99) if x.Cmp(bigMinus99) < 0 { x.Set(bigMinus99) } // (parent_diff + parent_diff // 2048 * max(1 - (block_timestamp - parent_timestamp) // 10, -99)) y.Div(parent.Difficulty, params.DifficultyBoundDivisor) x.Mul(y, x) x.Add(parent.Difficulty, x) // minimum difficulty can ever be (before exponential factor) if x.Cmp(params.MinimumDifficulty) < 0 { x.Set(params.MinimumDifficulty) } // for the exponential factor periodCount := new(big.Int).Add(parent.Number, big1) periodCount.Div(periodCount, expDiffPeriod) // the exponential factor, commonly referred to as "the bomb" // diff = diff + 2^(periodCount - 2) if periodCount.Cmp(big1) > 0 { y.Sub(periodCount, big2) y.Exp(big2, y, nil) x.Add(x, y) } return x } // calcDifficultyFrontier is the difficulty adjustment algorithm. It returns the // difficulty that a new block should have when created at time given the parent // block's time and difficulty. The calculation uses the Frontier rules. func calcDifficultyFrontier(time uint64, parent *types.Header) *big.Int { diff := new(big.Int) adjust := new(big.Int).Div(parent.Difficulty, params.DifficultyBoundDivisor) bigTime := new(big.Int) bigParentTime := new(big.Int) bigTime.SetUint64(time) bigParentTime.SetUint64(parent.Time) if bigTime.Sub(bigTime, bigParentTime).Cmp(params.DurationLimit) < 0 { diff.Add(parent.Difficulty, adjust) } else { diff.Sub(parent.Difficulty, adjust) } if diff.Cmp(params.MinimumDifficulty) < 0 { diff.Set(params.MinimumDifficulty) } periodCount := new(big.Int).Add(parent.Number, big1) periodCount.Div(periodCount, expDiffPeriod) if periodCount.Cmp(big1) > 0 { // diff = diff + 2^(periodCount - 2) expDiff := periodCount.Sub(periodCount, big2) expDiff.Exp(big2, expDiff, nil) diff.Add(diff, expDiff) diff = math.BigMax(diff, params.MinimumDifficulty) } return diff } // VerifySeal implements consensus.Engine, checking whether the given block satisfies // the PoW difficulty requirements. func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Header) error { return ethash.verifySeal(chain, header, false) } // verifySeal checks whether a block satisfies the PoW difficulty requirements, // either using the usual ethash cache for it, or alternatively using a full DAG // to make remote mining fast. func (ethash *Ethash) verifySeal(chain consensus.ChainReader, header *types.Header, fulldag bool) error { // If we're running a fake PoW, accept any seal as valid if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake { time.Sleep(ethash.fakeDelay) if ethash.fakeFail == header.Number.Uint64() { return errInvalidPoW } return nil } // If we're running a shared PoW, delegate verification to it if ethash.shared != nil { return ethash.shared.verifySeal(chain, header, fulldag) } // Ensure that we have a valid difficulty for the block if header.Difficulty.Sign() <= 0 { return errInvalidDifficulty } // Recompute the digest and PoW values number := header.Number.Uint64() var ( digest []byte result []byte ) // If fast-but-heavy PoW verification was requested, use an ethash dataset if fulldag { dataset := ethash.dataset(number, true) if dataset.generated() { digest, result = hashimotoFull(dataset.dataset, ethash.SealHash(header).Bytes(), header.Nonce.Uint64()) // Datasets are unmapped in a finalizer. Ensure that the dataset stays alive // until after the call to hashimotoFull so it's not unmapped while being used. runtime.KeepAlive(dataset) } else { // Dataset not yet generated, don't hang, use a cache instead fulldag = false } } // If slow-but-light PoW verification was requested (or DAG not yet ready), use an ethash cache if !fulldag { cache := ethash.cache(number) size := datasetSize(number) if ethash.config.PowMode == ModeTest { size = 32 * 1024 } digest, result = hashimotoLight(size, cache.cache, ethash.SealHash(header).Bytes(), header.Nonce.Uint64()) // Caches are unmapped in a finalizer. Ensure that the cache stays alive // until after the call to hashimotoLight so it's not unmapped while being used. runtime.KeepAlive(cache) } // Verify the calculated values against the ones provided in the header if !bytes.Equal(header.MixDigest[:], digest) { return errInvalidMixDigest } target := new(big.Int).Div(two256, header.Difficulty) if new(big.Int).SetBytes(result).Cmp(target) > 0 { return errInvalidPoW } return nil } // Prepare implements consensus.Engine, initializing the difficulty field of a // header to conform to the ethash protocol. The changes are done inline. func (ethash *Ethash) Prepare(chain consensus.ChainReader, header *types.Header) error { parent := chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) if parent == nil { return consensus.ErrUnknownAncestor } header.Difficulty = ethash.CalcDifficulty(chain, header.Time, parent) return nil } // Finalize implements consensus.Engine, accumulating the block and uncle rewards, // setting the final state on the header func (ethash *Ethash) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header) { // Accumulate any block and uncle rewards and commit the final state root accumulateRewards(chain.Config(), state, header, uncles) header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number)) } // FinalizeAndAssemble implements consensus.Engine, accumulating the block and // uncle rewards, setting the final state and assembling the block. func (ethash *Ethash) FinalizeAndAssemble(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) { // Accumulate any block and uncle rewards and commit the final state root accumulateRewards(chain.Config(), state, header, uncles) header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number)) // Header seems complete, assemble into a block and return return types.NewBlock(header, txs, uncles, receipts), nil } // SealHash returns the hash of a block prior to it being sealed. func (ethash *Ethash) SealHash(header *types.Header) (hash common.Hash) { hasher := sha3.NewLegacyKeccak256() rlp.Encode(hasher, []interface{}{ header.ParentHash, header.UncleHash, header.Coinbase, header.Root, header.TxHash, header.ReceiptHash, header.Bloom, header.Difficulty, header.Number, header.GasLimit, header.GasUsed, header.Time, header.Extra, }) hasher.Sum(hash[:0]) return hash } // Some weird constants to avoid constant memory allocs for them. var ( big8 = big.NewInt(8) big32 = big.NewInt(32) ) // AccumulateRewards credits the coinbase of the given block with the mining // reward. The total reward consists of the static block reward and rewards for // included uncles. The coinbase of each uncle block is also rewarded. func accumulateRewards(config *params.ChainConfig, state *state.StateDB, header *types.Header, uncles []*types.Header) { // Select the correct block reward based on chain progression blockReward := FrontierBlockReward if config.IsByzantium(header.Number) { blockReward = ByzantiumBlockReward } if config.IsConstantinople(header.Number) { blockReward = ConstantinopleBlockReward } // Accumulate the rewards for the miner and any included uncles reward := new(big.Int).Set(blockReward) r := new(big.Int) for _, uncle := range uncles { r.Add(uncle.Number, big8) r.Sub(r, header.Number) r.Mul(r, blockReward) r.Div(r, big8) state.AddBalance(uncle.Coinbase, r) r.Div(blockReward, big32) reward.Add(reward, r) } state.AddBalance(header.Coinbase, reward) }