// 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 . package backend import ( "bytes" "errors" "math/big" "math/rand" "time" "github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/common/hexutil" "github.com/ethereum/go-ethereum/consensus" "github.com/ethereum/go-ethereum/consensus/istanbul" istanbulCore "github.com/ethereum/go-ethereum/consensus/istanbul/core" "github.com/ethereum/go-ethereum/consensus/istanbul/validator" "github.com/ethereum/go-ethereum/core/state" "github.com/ethereum/go-ethereum/core/types" "github.com/ethereum/go-ethereum/log" "github.com/ethereum/go-ethereum/rlp" "github.com/ethereum/go-ethereum/rpc" lru "github.com/hashicorp/golang-lru" "golang.org/x/crypto/sha3" ) const ( checkpointInterval = 1024 // Number of blocks after which to save the vote snapshot to the database inmemorySnapshots = 128 // Number of recent vote snapshots to keep in memory inmemoryPeers = 40 inmemoryMessages = 1024 ) var ( // errInvalidProposal is returned when a prposal is malformed. errInvalidProposal = errors.New("invalid proposal") // errInvalidSignature is returned when given signature is not signed by given // address. errInvalidSignature = errors.New("invalid signature") // errUnknownBlock is returned when the list of validators is requested for a block // that is not part of the local blockchain. errUnknownBlock = errors.New("unknown block") // errUnauthorized is returned if a header is signed by a non authorized entity. errUnauthorized = errors.New("unauthorized") // errInvalidDifficulty is returned if the difficulty of a block is not 1 errInvalidDifficulty = errors.New("invalid difficulty") // errInvalidExtraDataFormat is returned when the extra data format is incorrect errInvalidExtraDataFormat = errors.New("invalid extra data format") // errInvalidMixDigest is returned if a block's mix digest is not Istanbul digest. errInvalidMixDigest = errors.New("invalid Istanbul mix digest") // errInvalidNonce is returned if a block's nonce is invalid errInvalidNonce = errors.New("invalid nonce") // errInvalidUncleHash is returned if a block contains an non-empty uncle list. errInvalidUncleHash = errors.New("non empty uncle hash") // errInconsistentValidatorSet is returned if the validator set is inconsistent // errInconsistentValidatorSet = errors.New("non empty uncle hash") // errInvalidTimestamp is returned if the timestamp of a block is lower than the previous block's timestamp + the minimum block period. errInvalidTimestamp = errors.New("invalid timestamp") // errInvalidVotingChain is returned if an authorization list is attempted to // be modified via out-of-range or non-contiguous headers. errInvalidVotingChain = errors.New("invalid voting chain") // errInvalidVote is returned if a nonce value is something else that the two // allowed constants of 0x00..0 or 0xff..f. errInvalidVote = errors.New("vote nonce not 0x00..0 or 0xff..f") // errInvalidCommittedSeals is returned if the committed seal is not signed by any of parent validators. errInvalidCommittedSeals = errors.New("invalid committed seals") // errEmptyCommittedSeals is returned if the field of committed seals is zero. errEmptyCommittedSeals = errors.New("zero committed seals") // errMismatchTxhashes is returned if the TxHash in header is mismatch. errMismatchTxhashes = errors.New("mismatch transactions hashes") ) var ( defaultDifficulty = big.NewInt(1) nilUncleHash = types.CalcUncleHash(nil) // Always Keccak256(RLP([])) as uncles are meaningless outside of PoW. emptyNonce = types.BlockNonce{} now = time.Now nonceAuthVote = hexutil.MustDecode("0xffffffffffffffff") // Magic nonce number to vote on adding a new validator nonceDropVote = hexutil.MustDecode("0x0000000000000000") // Magic nonce number to vote on removing a validator. inmemoryAddresses = 20 // Number of recent addresses from ecrecover recentAddresses, _ = lru.NewARC(inmemoryAddresses) ) // Author retrieves the Ethereum address of the account that minted the given // block, which may be different from the header's coinbase if a consensus // engine is based on signatures. func (sb *backend) Author(header *types.Header) (common.Address, error) { return ecrecover(header) } // Signers extracts all the addresses who have signed the given header // It will extract for each seal who signed it, regardless of if the seal is // repeated func (sb *backend) Signers(header *types.Header) ([]common.Address, error) { extra, err := types.ExtractIstanbulExtra(header) if err != nil { return []common.Address{}, err } var addrs []common.Address proposalSeal := istanbulCore.PrepareCommittedSeal(header.Hash()) // 1. Get committed seals from current header for _, seal := range extra.CommittedSeal { // 2. Get the original address by seal and parent block hash addr, err := istanbul.GetSignatureAddress(proposalSeal, seal) if err != nil { sb.logger.Error("not a valid address", "err", err) return nil, errInvalidSignature } addrs = append(addrs, addr) } return addrs, nil } // VerifyHeader checks whether a header conforms to the consensus rules of a // given engine. Verifying the seal may be done optionally here, or explicitly // via the VerifySeal method. func (sb *backend) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error { return sb.verifyHeader(chain, header, nil) } // verifyHeader checks whether a header conforms to the consensus rules.The // caller may optionally pass in a batch of parents (ascending order) to avoid // looking those up from the database. This is useful for concurrently verifying // a batch of new headers. func (sb *backend) verifyHeader(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error { if header.Number == nil { return errUnknownBlock } // Don't waste time checking blocks from the future (adjusting for allowed threshold) adjustedTimeNow := now().Add(time.Duration(sb.config.AllowedFutureBlockTime) * time.Second).Unix() if header.Time > uint64(adjustedTimeNow) { return consensus.ErrFutureBlock } // Ensure that the extra data format is satisfied if _, err := types.ExtractIstanbulExtra(header); err != nil { return errInvalidExtraDataFormat } // Ensure that the coinbase is valid if header.Nonce != (emptyNonce) && !bytes.Equal(header.Nonce[:], nonceAuthVote) && !bytes.Equal(header.Nonce[:], nonceDropVote) { return errInvalidNonce } // Ensure that the mix digest is zero as we don't have fork protection currently if header.MixDigest != types.IstanbulDigest { return errInvalidMixDigest } // Ensure that the block doesn't contain any uncles which are meaningless in Istanbul if header.UncleHash != nilUncleHash { return errInvalidUncleHash } // Ensure that the block's difficulty is meaningful (may not be correct at this point) if header.Difficulty == nil || header.Difficulty.Cmp(defaultDifficulty) != 0 { return errInvalidDifficulty } return sb.verifyCascadingFields(chain, header, parents) } // verifyCascadingFields verifies all the header fields that are not standalone, // rather depend on a batch of previous headers. The caller may optionally pass // in a batch of parents (ascending order) to avoid looking those up from the // database. This is useful for concurrently verifying a batch of new headers. func (sb *backend) verifyCascadingFields(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error { // The genesis block is the always valid dead-end number := header.Number.Uint64() if number == 0 { return nil } // Ensure that the block's timestamp isn't too close to it's parent var parent *types.Header if len(parents) > 0 { parent = parents[len(parents)-1] } else { parent = chain.GetHeader(header.ParentHash, number-1) } if parent == nil || parent.Number.Uint64() != number-1 || parent.Hash() != header.ParentHash { return consensus.ErrUnknownAncestor } if parent.Time+sb.config.BlockPeriod > header.Time { return errInvalidTimestamp } // Verify validators in extraData. Validators in snapshot and extraData should be the same. snap, err := sb.snapshot(chain, number-1, header.ParentHash, parents) if err != nil { return err } validators := make([]byte, len(snap.validators())*common.AddressLength) for i, validator := range snap.validators() { copy(validators[i*common.AddressLength:], validator[:]) } if err := sb.verifySigner(chain, header, parents); err != nil { return err } return sb.verifyCommittedSeals(chain, header, parents) } // 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 (the order is that of // the input slice). func (sb *backend) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) { abort := make(chan struct{}) results := make(chan error, len(headers)) go func() { for i, header := range headers { err := sb.verifyHeader(chain, header, headers[:i]) select { case <-abort: return case results <- err: } } }() return abort, results } // VerifyUncles verifies that the given block's uncles conform to the consensus // rules of a given engine. func (sb *backend) VerifyUncles(chain consensus.ChainReader, block *types.Block) error { if len(block.Uncles()) > 0 { return errInvalidUncleHash } return nil } // verifySigner checks whether the signer is in parent's validator set func (sb *backend) verifySigner(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error { // Verifying the genesis block is not supported number := header.Number.Uint64() if number == 0 { return errUnknownBlock } // Retrieve the snapshot needed to verify this header and cache it snap, err := sb.snapshot(chain, number-1, header.ParentHash, parents) if err != nil { return err } // resolve the authorization key and check against signers signer, err := ecrecover(header) if err != nil { return err } // Signer should be in the validator set of previous block's extraData. if _, v := snap.ValSet.GetByAddress(signer); v == nil { return errUnauthorized } return nil } // verifyCommittedSeals checks whether every committed seal is signed by one of the parent's validators func (sb *backend) verifyCommittedSeals(chain consensus.ChainReader, header *types.Header, parents []*types.Header) error { number := header.Number.Uint64() // We don't need to verify committed seals in the genesis block if number == 0 { return nil } // Retrieve the snapshot needed to verify this header and cache it snap, err := sb.snapshot(chain, number-1, header.ParentHash, parents) if err != nil { return err } extra, err := types.ExtractIstanbulExtra(header) if err != nil { return err } // The length of Committed seals should be larger than 0 if len(extra.CommittedSeal) == 0 { return errEmptyCommittedSeals } validators := snap.ValSet.Copy() // Check whether the committed seals are generated by parent's validators validSeal := 0 committers, err := sb.Signers(header) if err != nil { return err } for _, addr := range committers { if validators.RemoveValidator(addr) { validSeal++ continue } return errInvalidCommittedSeals } // The length of validSeal should be larger than number of faulty node + 1 if validSeal <= snap.ValSet.F() { return errInvalidCommittedSeals } return nil } // VerifySeal checks whether the crypto seal on a header is valid according to // the consensus rules of the given engine. func (sb *backend) VerifySeal(chain consensus.ChainReader, header *types.Header) error { // get parent header and ensure the signer is in parent's validator set number := header.Number.Uint64() if number == 0 { return errUnknownBlock } // ensure that the difficulty equals to defaultDifficulty if header.Difficulty.Cmp(defaultDifficulty) != 0 { return errInvalidDifficulty } return sb.verifySigner(chain, header, nil) } // Prepare initializes the consensus fields of a block header according to the // rules of a particular engine. The changes are executed inline. func (sb *backend) Prepare(chain consensus.ChainReader, header *types.Header) error { // unused fields, force to set to empty header.Coinbase = common.Address{} header.Nonce = emptyNonce header.MixDigest = types.IstanbulDigest // copy the parent extra data as the header extra data number := header.Number.Uint64() parent := chain.GetHeader(header.ParentHash, number-1) if parent == nil { return consensus.ErrUnknownAncestor } // use the same difficulty for all blocks header.Difficulty = defaultDifficulty // Assemble the voting snapshot snap, err := sb.snapshot(chain, number-1, header.ParentHash, nil) if err != nil { return err } // get valid candidate list sb.candidatesLock.RLock() var addresses []common.Address var authorizes []bool for address, authorize := range sb.candidates { if snap.checkVote(address, authorize) { addresses = append(addresses, address) authorizes = append(authorizes, authorize) } } sb.candidatesLock.RUnlock() // pick one of the candidates randomly if len(addresses) > 0 { index := rand.Intn(len(addresses)) // add validator voting in coinbase header.Coinbase = addresses[index] if authorizes[index] { copy(header.Nonce[:], nonceAuthVote) } else { copy(header.Nonce[:], nonceDropVote) } } // add validators in snapshot to extraData's validators section extra, err := prepareExtra(header, snap.validators()) if err != nil { return err } header.Extra = extra // set header's timestamp header.Time = parent.Time + sb.config.BlockPeriod if header.Time < uint64(time.Now().Unix()) { header.Time = uint64(time.Now().Unix()) } return nil } // Finalize runs any post-transaction state modifications (e.g. block rewards) // and assembles the final block. // // Note, the block header and state database might be updated to reflect any // consensus rules that happen at finalization (e.g. block rewards). func (sb *backend) Finalize(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header) { // No block rewards in Istanbul, so the state remains as is and uncles are dropped header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number)) header.UncleHash = nilUncleHash } // FinalizeAndAssemble implements consensus.Engine, ensuring no uncles are set, // nor block rewards given, and returns the final block. func (sb *backend) FinalizeAndAssemble(chain consensus.ChainReader, header *types.Header, state *state.StateDB, txs []*types.Transaction, uncles []*types.Header, receipts []*types.Receipt) (*types.Block, error) { /// No block rewards in Istanbul, so the state remains as is and uncles are dropped header.Root = state.IntermediateRoot(chain.Config().IsEIP158(header.Number)) header.UncleHash = nilUncleHash // Assemble and return the final block for sealing return types.NewBlock(header, txs, nil, receipts), nil } // Seal generates a new block for the given input block with the local miner's // seal place on top. func (sb *backend) Seal(chain consensus.ChainReader, block *types.Block, results chan<- *types.Block, stop <-chan struct{}) error { // update the block header timestamp and signature and propose the block to core engine header := block.Header() number := header.Number.Uint64() // Bail out if we're unauthorized to sign a block snap, err := sb.snapshot(chain, number-1, header.ParentHash, nil) if err != nil { return err } if _, v := snap.ValSet.GetByAddress(sb.address); v == nil { return errUnauthorized } parent := chain.GetHeader(header.ParentHash, number-1) if parent == nil { return consensus.ErrUnknownAncestor } block, err = sb.updateBlock(parent, block) if err != nil { return err } delay := time.Unix(int64(block.Header().Time), 0).Sub(now()) go func() { // wait for the timestamp of header, use this to adjust the block period select { case <-time.After(delay): case <-stop: results <- nil return } // get the proposed block hash and clear it if the seal() is completed. sb.sealMu.Lock() sb.proposedBlockHash = block.Hash() defer func() { sb.proposedBlockHash = common.Hash{} sb.sealMu.Unlock() }() // post block into Istanbul engine go sb.EventMux().Post(istanbul.RequestEvent{ Proposal: block, }) for { select { case result := <-sb.commitCh: // if the block hash and the hash from channel are the same, // return the result. Otherwise, keep waiting the next hash. if result != nil && block.Hash() == result.Hash() { results <- result return } case <-stop: results <- nil return } } }() return nil } // update timestamp and signature of the block based on its number of transactions func (sb *backend) updateBlock(parent *types.Header, block *types.Block) (*types.Block, error) { header := block.Header() // sign the hash seal, err := sb.Sign(sigHash(header).Bytes()) if err != nil { return nil, err } err = writeSeal(header, seal) if err != nil { return nil, err } return block.WithSeal(header), nil } // APIs returns the RPC APIs this consensus engine provides. func (sb *backend) APIs(chain consensus.ChainReader) []rpc.API { return []rpc.API{{ Namespace: "istanbul", Version: "1.0", Service: &API{chain: chain, istanbul: sb}, Public: true, }} } // Start implements consensus.Istanbul.Start func (sb *backend) Start(chain consensus.ChainReader, currentBlock func() *types.Block, hasBadBlock func(hash common.Hash) bool) error { sb.coreMu.Lock() defer sb.coreMu.Unlock() if sb.coreStarted { return istanbul.ErrStartedEngine } // clear previous data sb.proposedBlockHash = common.Hash{} if sb.commitCh != nil { close(sb.commitCh) } sb.commitCh = make(chan *types.Block, 1) sb.chain = chain sb.currentBlock = currentBlock sb.hasBadBlock = hasBadBlock if err := sb.core.Start(); err != nil { return err } sb.coreStarted = true return nil } // Stop implements consensus.Istanbul.Stop func (sb *backend) Stop() error { sb.coreMu.Lock() defer sb.coreMu.Unlock() if !sb.coreStarted { return istanbul.ErrStoppedEngine } if err := sb.core.Stop(); err != nil { return err } sb.coreStarted = false return nil } // snapshot retrieves the authorization snapshot at a given point in time. func (sb *backend) snapshot(chain consensus.ChainReader, number uint64, hash common.Hash, parents []*types.Header) (*Snapshot, error) { // Search for a snapshot in memory or on disk for checkpoints var ( headers []*types.Header snap *Snapshot ) for snap == nil { // If an in-memory snapshot was found, use that if s, ok := sb.recents.Get(hash); ok { snap = s.(*Snapshot) break } // If an on-disk checkpoint snapshot can be found, use that if number%checkpointInterval == 0 { if s, err := loadSnapshot(sb.config.Epoch, sb.db, hash); err == nil { log.Trace("Loaded voting snapshot form disk", "number", number, "hash", hash) snap = s break } } // If we're at block zero, make a snapshot if number == 0 { genesis := chain.GetHeaderByNumber(0) if err := sb.VerifyHeader(chain, genesis, false); err != nil { return nil, err } istanbulExtra, err := types.ExtractIstanbulExtra(genesis) if err != nil { return nil, err } snap = newSnapshot(sb.config.Epoch, 0, genesis.Hash(), validator.NewSet(istanbulExtra.Validators, sb.config.ProposerPolicy)) if err := snap.store(sb.db); err != nil { return nil, err } log.Trace("Stored genesis voting snapshot to disk") break } // No snapshot for this header, gather the header and move backward var header *types.Header if len(parents) > 0 { // If we have explicit parents, pick from there (enforced) header = parents[len(parents)-1] if header.Hash() != hash || header.Number.Uint64() != number { return nil, consensus.ErrUnknownAncestor } parents = parents[:len(parents)-1] } else { // No explicit parents (or no more left), reach out to the database header = chain.GetHeader(hash, number) if header == nil { return nil, consensus.ErrUnknownAncestor } } headers = append(headers, header) number, hash = number-1, header.ParentHash } // Previous snapshot found, apply any pending headers on top of it for i := 0; i < len(headers)/2; i++ { headers[i], headers[len(headers)-1-i] = headers[len(headers)-1-i], headers[i] } snap, err := snap.apply(headers) if err != nil { return nil, err } sb.recents.Add(snap.Hash, snap) // If we've generated a new checkpoint snapshot, save to disk if snap.Number%checkpointInterval == 0 && len(headers) > 0 { if err = snap.store(sb.db); err != nil { return nil, err } log.Trace("Stored voting snapshot to disk", "number", snap.Number, "hash", snap.Hash) } return snap, err } // FIXME: Need to update this for Istanbul // sigHash returns the hash which is used as input for the Istanbul // signing. It is the hash of the entire header apart from the 65 byte signature // contained at the end of the extra data. // // Note, the method requires the extra data to be at least 65 bytes, otherwise it // panics. This is done to avoid accidentally using both forms (signature present // or not), which could be abused to produce different hashes for the same header. func sigHash(header *types.Header) (hash common.Hash) { hasher := sha3.NewLegacyKeccak256() // Clean seal is required for calculating proposer seal. rlp.Encode(hasher, types.IstanbulFilteredHeader(header, false)) hasher.Sum(hash[:0]) return hash } // SealHash returns the hash of a block prior to it being sealed. func (sb *backend) SealHash(header *types.Header) common.Hash { return sigHash(header) } // ecrecover extracts the Ethereum account address from a signed header. func ecrecover(header *types.Header) (common.Address, error) { hash := header.Hash() if addr, ok := recentAddresses.Get(hash); ok { return addr.(common.Address), nil } // Retrieve the signature from the header extra-data istanbulExtra, err := types.ExtractIstanbulExtra(header) if err != nil { return common.Address{}, err } addr, err := istanbul.GetSignatureAddress(sigHash(header).Bytes(), istanbulExtra.Seal) if err != nil { return addr, err } recentAddresses.Add(hash, addr) return addr, nil } // prepareExtra returns a extra-data of the given header and validators func prepareExtra(header *types.Header, vals []common.Address) ([]byte, error) { var buf bytes.Buffer // compensate the lack bytes if header.Extra is not enough IstanbulExtraVanity bytes. if len(header.Extra) < types.IstanbulExtraVanity { header.Extra = append(header.Extra, bytes.Repeat([]byte{0x00}, types.IstanbulExtraVanity-len(header.Extra))...) } buf.Write(header.Extra[:types.IstanbulExtraVanity]) ist := &types.IstanbulExtra{ Validators: vals, Seal: []byte{}, CommittedSeal: [][]byte{}, } payload, err := rlp.EncodeToBytes(&ist) if err != nil { return nil, err } return append(buf.Bytes(), payload...), nil } // writeSeal writes the extra-data field of the given header with the given seals. // suggest to rename to writeSeal. func writeSeal(h *types.Header, seal []byte) error { if len(seal)%types.IstanbulExtraSeal != 0 { return errInvalidSignature } istanbulExtra, err := types.ExtractIstanbulExtra(h) if err != nil { return err } istanbulExtra.Seal = seal payload, err := rlp.EncodeToBytes(&istanbulExtra) if err != nil { return err } h.Extra = append(h.Extra[:types.IstanbulExtraVanity], payload...) return nil } // writeCommittedSeals writes the extra-data field of a block header with given committed seals. func writeCommittedSeals(h *types.Header, committedSeals [][]byte) error { if len(committedSeals) == 0 { return errInvalidCommittedSeals } for _, seal := range committedSeals { if len(seal) != types.IstanbulExtraSeal { return errInvalidCommittedSeals } } istanbulExtra, err := types.ExtractIstanbulExtra(h) if err != nil { return err } istanbulExtra.CommittedSeal = make([][]byte, len(committedSeals)) copy(istanbulExtra.CommittedSeal, committedSeals) payload, err := rlp.EncodeToBytes(&istanbulExtra) if err != nil { return err } h.Extra = append(h.Extra[:types.IstanbulExtraVanity], payload...) return nil }