// Copyright 2015 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 core
import (
"fmt"
"math/big"
"time"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/state"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/logger/glog"
"github.com/ethereum/go-ethereum/params"
"github.com/ethereum/go-ethereum/pow"
"gopkg.in/fatih/set.v0"
)
var (
ExpDiffPeriod = big.NewInt(100000)
big10 = big.NewInt(10)
bigMinus99 = big.NewInt(-99)
)
// BlockValidator is responsible for validating block headers, uncles and
// processed state.
//
// BlockValidator implements Validator.
type BlockValidator struct {
config *params.ChainConfig // Chain configuration options
bc *BlockChain // Canonical block chain
Pow pow.PoW // Proof of work used for validating
}
// NewBlockValidator returns a new block validator which is safe for re-use
func NewBlockValidator(config *params.ChainConfig, blockchain *BlockChain, pow pow.PoW) *BlockValidator {
validator := &BlockValidator{
config: config,
Pow: pow,
bc: blockchain,
}
return validator
}
// ValidateBlock validates the given block's header and uncles and verifies the
// the block header's transaction and uncle roots.
//
// ValidateBlock does not validate the header's pow. The pow work validated
// separately so we can process them in parallel.
//
// ValidateBlock also validates and makes sure that any previous state (or present)
// state that might or might not be present is checked to make sure that fast
// sync has done it's job proper. This prevents the block validator from accepting
// false positives where a header is present but the state is not.
func (v *BlockValidator) ValidateBlock(block *types.Block) error {
if v.bc.HasBlock(block.Hash()) {
if _, err := state.New(block.Root(), v.bc.chainDb); err == nil {
return &KnownBlockError{block.Number(), block.Hash()}
}
}
parent := v.bc.GetBlock(block.ParentHash(), block.NumberU64()-1)
if parent == nil {
return ParentError(block.ParentHash())
}
if _, err := state.New(parent.Root(), v.bc.chainDb); err != nil {
return ParentError(block.ParentHash())
}
header := block.Header()
// validate the block header
if err := ValidateHeader(v.config, v.Pow, header, parent.Header(), false, false); err != nil {
return err
}
// verify the uncles are correctly rewarded
if err := v.VerifyUncles(block, parent); err != nil {
return err
}
// Verify UncleHash before running other uncle validations
unclesSha := types.CalcUncleHash(block.Uncles())
if unclesSha != header.UncleHash {
return fmt.Errorf("invalid uncles root hash. received=%x calculated=%x", header.UncleHash, unclesSha)
}
// The transactions Trie's root (R = (Tr [[i, RLP(T1)], [i, RLP(T2)], ... [n, RLP(Tn)]]))
// can be used by light clients to make sure they've received the correct Txs
txSha := types.DeriveSha(block.Transactions())
if txSha != header.TxHash {
return fmt.Errorf("invalid transaction root hash. received=%x calculated=%x", header.TxHash, txSha)
}
return nil
}
// ValidateState validates the various changes that happen after a state
// transition, such as amount of used gas, the receipt roots and the state root
// itself. ValidateState returns a database batch if the validation was a success
// otherwise nil and an error is returned.
func (v *BlockValidator) ValidateState(block, parent *types.Block, statedb *state.StateDB, receipts types.Receipts, usedGas *big.Int) (err error) {
header := block.Header()
if block.GasUsed().Cmp(usedGas) != 0 {
return ValidationError(fmt.Sprintf("gas used error (%v / %v)", block.GasUsed(), usedGas))
}
// Validate the received block's bloom with the one derived from the generated receipts.
// For valid blocks this should always validate to true.
rbloom := types.CreateBloom(receipts)
if rbloom != header.Bloom {
return fmt.Errorf("unable to replicate block's bloom=%x vs calculated bloom=%x", header.Bloom, rbloom)
}
// Tre receipt Trie's root (R = (Tr [[H1, R1], ... [Hn, R1]]))
receiptSha := types.DeriveSha(receipts)
if receiptSha != header.ReceiptHash {
return fmt.Errorf("invalid receipt root hash. received=%x calculated=%x", header.ReceiptHash, receiptSha)
}
// Validate the state root against the received state root and throw
// an error if they don't match.
if root := statedb.IntermediateRoot(v.config.IsEIP158(header.Number)); header.Root != root {
return fmt.Errorf("invalid merkle root: header=%x computed=%x", header.Root, root)
}
return nil
}
// VerifyUncles verifies the given block's uncles and applies the Ethereum
// consensus rules to the various block headers included; it will return an
// error if any of the included uncle headers were invalid. It returns an error
// if the validation failed.
func (v *BlockValidator) VerifyUncles(block, parent *types.Block) error {
// validate that there are at most 2 uncles included in this block
if len(block.Uncles()) > 2 {
return ValidationError("Block can only contain maximum 2 uncles (contained %v)", len(block.Uncles()))
}
uncles := set.New()
ancestors := make(map[common.Hash]*types.Block)
for _, ancestor := range v.bc.GetBlocksFromHash(block.ParentHash(), 7) {
ancestors[ancestor.Hash()] = ancestor
// Include ancestors uncles in the uncle set. Uncles must be unique.
for _, uncle := range ancestor.Uncles() {
uncles.Add(uncle.Hash())
}
}
ancestors[block.Hash()] = block
uncles.Add(block.Hash())
for i, uncle := range block.Uncles() {
hash := uncle.Hash()
if uncles.Has(hash) {
// Error not unique
return UncleError("uncle[%d](%x) not unique", i, hash[:4])
}
uncles.Add(hash)
if ancestors[hash] != nil {
branch := fmt.Sprintf(" O - %x\n |\n", block.Hash())
for h := range ancestors {
branch += fmt.Sprintf(" O - %x\n |\n", h)
}
glog.Infoln(branch)
return UncleError("uncle[%d](%x) is ancestor", i, hash[:4])
}
if ancestors[uncle.ParentHash] == nil || uncle.ParentHash == parent.Hash() {
return UncleError("uncle[%d](%x)'s parent is not ancestor (%x)", i, hash[:4], uncle.ParentHash[0:4])
}
if err := ValidateHeader(v.config, v.Pow, uncle, ancestors[uncle.ParentHash].Header(), true, true); err != nil {
return ValidationError(fmt.Sprintf("uncle[%d](%x) header invalid: %v", i, hash[:4], err))
}
}
return nil
}
// ValidateHeader validates the given header and, depending on the pow arg,
// checks the proof of work of the given header. Returns an error if the
// validation failed.
func (v *BlockValidator) ValidateHeader(header, parent *types.Header, checkPow bool) error {
// Short circuit if the parent is missing.
if parent == nil {
return ParentError(header.ParentHash)
}
// Short circuit if the header's already known or its parent is missing
if v.bc.HasHeader(header.Hash()) {
return nil
}
return ValidateHeader(v.config, v.Pow, header, parent, checkPow, false)
}
// Validates a header. Returns an error if the header is invalid.
//
// See YP section 4.3.4. "Block Header Validity"
func ValidateHeader(config *params.ChainConfig, pow pow.PoW, header *types.Header, parent *types.Header, checkPow, uncle bool) error {
if big.NewInt(int64(len(header.Extra))).Cmp(params.MaximumExtraDataSize) == 1 {
return fmt.Errorf("Header extra data too long (%d)", len(header.Extra))
}
if uncle {
if header.Time.Cmp(common.MaxBig) == 1 {
return BlockTSTooBigErr
}
} else {
if header.Time.Cmp(big.NewInt(time.Now().Unix())) == 1 {
return BlockFutureErr
}
}
if header.Time.Cmp(parent.Time) != 1 {
return BlockEqualTSErr
}
expd := CalcDifficulty(config, header.Time.Uint64(), parent.Time.Uint64(), parent.Number, parent.Difficulty)
if expd.Cmp(header.Difficulty) != 0 {
return fmt.Errorf("Difficulty check failed for header %v, %v", header.Difficulty, expd)
}
a := new(big.Int).Set(parent.GasLimit)
a = a.Sub(a, header.GasLimit)
a.Abs(a)
b := new(big.Int).Set(parent.GasLimit)
b = b.Div(b, params.GasLimitBoundDivisor)
if !(a.Cmp(b) < 0) || (header.GasLimit.Cmp(params.MinGasLimit) == -1) {
return fmt.Errorf("GasLimit check failed for header %v (%v > %v)", header.GasLimit, a, b)
}
num := new(big.Int).Set(parent.Number)
num.Sub(header.Number, num)
if num.Cmp(big.NewInt(1)) != 0 {
return BlockNumberErr
}
if checkPow {
// Verify the nonce of the header. Return an error if it's not valid
if !pow.Verify(types.NewBlockWithHeader(header)) {
return &BlockNonceErr{header.Number, header.Hash(), header.Nonce.Uint64()}
}
}
// If all checks passed, validate the extra-data field for hard forks
if err := ValidateDAOHeaderExtraData(config, header); err != nil {
return err
}
if !uncle && config.EIP150Block != nil && config.EIP150Block.Cmp(header.Number) == 0 {
if config.EIP150Hash != (common.Hash{}) && config.EIP150Hash != header.Hash() {
return ValidationError("Homestead gas reprice fork hash mismatch: have 0x%x, want 0x%x", header.Hash(), config.EIP150Hash)
}
}
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 CalcDifficulty(config *params.ChainConfig, time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
if config.IsHomestead(new(big.Int).Add(parentNumber, common.Big1)) {
return calcDifficultyHomestead(time, parentTime, parentNumber, parentDiff)
} else {
return calcDifficultyFrontier(time, parentTime, parentNumber, parentDiff)
}
}
func calcDifficultyHomestead(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
// https://github.com/ethereum/EIPs/blob/master/EIPS/eip-2.mediawiki
// 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(parentTime)
// 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(common.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(parentDiff, params.DifficultyBoundDivisor)
x.Mul(y, x)
x.Add(parentDiff, 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(parentNumber, common.Big1)
periodCount.Div(periodCount, ExpDiffPeriod)
// the exponential factor, commonly referred to as "the bomb"
// diff = diff + 2^(periodCount - 2)
if periodCount.Cmp(common.Big1) > 0 {
y.Sub(periodCount, common.Big2)
y.Exp(common.Big2, y, nil)
x.Add(x, y)
}
return x
}
func calcDifficultyFrontier(time, parentTime uint64, parentNumber, parentDiff *big.Int) *big.Int {
diff := new(big.Int)
adjust := new(big.Int).Div(parentDiff, params.DifficultyBoundDivisor)
bigTime := new(big.Int)
bigParentTime := new(big.Int)
bigTime.SetUint64(time)
bigParentTime.SetUint64(parentTime)
if bigTime.Sub(bigTime, bigParentTime).Cmp(params.DurationLimit) < 0 {
diff.Add(parentDiff, adjust)
} else {
diff.Sub(parentDiff, adjust)
}
if diff.Cmp(params.MinimumDifficulty) < 0 {
diff.Set(params.MinimumDifficulty)
}
periodCount := new(big.Int).Add(parentNumber, common.Big1)
periodCount.Div(periodCount, ExpDiffPeriod)
if periodCount.Cmp(common.Big1) > 0 {
// diff = diff + 2^(periodCount - 2)
expDiff := periodCount.Sub(periodCount, common.Big2)
expDiff.Exp(common.Big2, expDiff, nil)
diff.Add(diff, expDiff)
diff = common.BigMax(diff, params.MinimumDifficulty)
}
return diff
}
// CalcGasLimit computes the gas limit of the next block after parent.
// The result may be modified by the caller.
// This is miner strategy, not consensus protocol.
func CalcGasLimit(parent *types.Block) *big.Int {
// contrib = (parentGasUsed * 3 / 2) / 1024
contrib := new(big.Int).Mul(parent.GasUsed(), big.NewInt(3))
contrib = contrib.Div(contrib, big.NewInt(2))
contrib = contrib.Div(contrib, params.GasLimitBoundDivisor)
// decay = parentGasLimit / 1024 -1
decay := new(big.Int).Div(parent.GasLimit(), params.GasLimitBoundDivisor)
decay.Sub(decay, big.NewInt(1))
/*
strategy: gasLimit of block-to-mine is set based on parent's
gasUsed value. if parentGasUsed > parentGasLimit * (2/3) then we
increase it, otherwise lower it (or leave it unchanged if it's right
at that usage) the amount increased/decreased depends on how far away
from parentGasLimit * (2/3) parentGasUsed is.
*/
gl := new(big.Int).Sub(parent.GasLimit(), decay)
gl = gl.Add(gl, contrib)
gl.Set(common.BigMax(gl, params.MinGasLimit))
// however, if we're now below the target (TargetGasLimit) we increase the
// limit as much as we can (parentGasLimit / 1024 -1)
if gl.Cmp(params.TargetGasLimit) < 0 {
gl.Add(parent.GasLimit(), decay)
gl.Set(common.BigMin(gl, params.TargetGasLimit))
}
return gl
}
