go-ethereum/core/block_validator.go

// Copyright 2014 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"
)

// BlockValidator is responsible for validating block headers, uncles and
// processed state.
//
// BlockValidator implements Validator.
type BlockValidator struct {
	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(blockchain *BlockChain, pow pow.PoW) *BlockValidator {
	validator := &BlockValidator{
		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
// seperately so we can process them in paralel.
//
// 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 form 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())
	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.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 succes
// 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", 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(); 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 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.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 missing
	if v.bc.HasHeader(header.Hash()) {
		return nil
	}
	return ValidateHeader(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(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(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()}
		}
	}
	return nil
}