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state_transition.go
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state_transition.go
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// 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"
"math/big"
"github.com/ethereum/go-ethereum/common"
cmath "github.com/ethereum/go-ethereum/common/math"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/core/vm"
"github.com/ethereum/go-ethereum/crypto"
"github.com/ethereum/go-ethereum/params"
)
var emptyCodeHash = crypto.Keccak256Hash(nil)
// StateTransition represents a state transition.
//
// == The State Transitioning Model
//
// A state transition is a change made when a transaction is applied to the current world
// state. The state transitioning model does all the necessary work to work out a valid new
// state root.
//
// 1. Nonce handling
// 2. Pre pay gas
// 3. Create a new state object if the recipient is nil
// 4. Value transfer
//
// == If contract creation ==
//
// 4a. Attempt to run transaction data
// 4b. If valid, use result as code for the new state object
//
// == end ==
//
// 5. Run Script section
// 6. Derive new state root
type StateTransition struct {
gp *GasPool
msg Message
gas uint64
gasPrice *big.Int
gasFeeCap *big.Int
gasTipCap *big.Int
initialGas uint64
value *big.Int
data []byte
state vm.StateDB
evm *vm.EVM
}
// Message represents a message sent to a contract.
type Message interface {
From() common.Address
To() *common.Address
GasPrice() *big.Int
GasFeeCap() *big.Int
GasTipCap() *big.Int
Gas() uint64
Value() *big.Int
Nonce() uint64
IsFake() bool
Data() []byte
AccessList() types.AccessList
}
// ExecutionResult includes all output after executing given evm
// message no matter the execution itself is successful or not.
type ExecutionResult struct {
UsedGas uint64 // Total used gas but include the refunded gas
Err error // Any error encountered during the execution(listed in core/vm/errors.go)
ReturnData []byte // Returned data from evm(function result or data supplied with revert opcode)
}
// Unwrap returns the internal evm error which allows us for further
// analysis outside.
func (result *ExecutionResult) Unwrap() error {
return result.Err
}
// Failed returns the indicator whether the execution is successful or not
func (result *ExecutionResult) Failed() bool { return result.Err != nil }
// Return is a helper function to help caller distinguish between revert reason
// and function return. Return returns the data after execution if no error occurs.
func (result *ExecutionResult) Return() []byte {
if result.Err != nil {
return nil
}
return common.CopyBytes(result.ReturnData)
}
// Revert returns the concrete revert reason if the execution is aborted by `REVERT`
// opcode. Note the reason can be nil if no data supplied with revert opcode.
func (result *ExecutionResult) Revert() []byte {
if result.Err != vm.ErrExecutionReverted {
return nil
}
return common.CopyBytes(result.ReturnData)
}
// IntrinsicGas computes the 'intrinsic gas' for a message with the given data.
func IntrinsicGas(data []byte, accessList types.AccessList, isContractCreation bool, isHomestead, isEIP2028 bool, isEIP3860 bool) (uint64, error) {
// Set the starting gas for the raw transaction
var gas uint64
if isContractCreation && isHomestead {
gas = params.TxGasContractCreation
} else {
gas = params.TxGas
}
dataLen := uint64(len(data))
// Bump the required gas by the amount of transactional data
if dataLen > 0 {
// Zero and non-zero bytes are priced differently
var nz uint64
for _, byt := range data {
if byt != 0 {
nz++
}
}
// Make sure we don't exceed uint64 for all data combinations
nonZeroGas := params.TxDataNonZeroGasFrontier
if isEIP2028 {
nonZeroGas = params.TxDataNonZeroGasEIP2028
}
if (math.MaxUint64-gas)/nonZeroGas < nz {
return 0, ErrGasUintOverflow
}
gas += nz * nonZeroGas
z := dataLen - nz
if (math.MaxUint64-gas)/params.TxDataZeroGas < z {
return 0, ErrGasUintOverflow
}
gas += z * params.TxDataZeroGas
if isContractCreation && isEIP3860 {
lenWords := toWordSize(dataLen)
if (math.MaxUint64-gas)/params.InitCodeWordGas < lenWords {
return 0, ErrGasUintOverflow
}
gas += lenWords * params.InitCodeWordGas
}
}
if accessList != nil {
gas += uint64(len(accessList)) * params.TxAccessListAddressGas
gas += uint64(accessList.StorageKeys()) * params.TxAccessListStorageKeyGas
}
return gas, nil
}
// toWordSize returns the ceiled word size required for init code payment calculation.
func toWordSize(size uint64) uint64 {
if size > math.MaxUint64-31 {
return math.MaxUint64/32 + 1
}
return (size + 31) / 32
}
// NewStateTransition initialises and returns a new state transition object.
func NewStateTransition(evm *vm.EVM, msg Message, gp *GasPool) *StateTransition {
return &StateTransition{
gp: gp,
evm: evm,
msg: msg,
gasPrice: msg.GasPrice(),
gasFeeCap: msg.GasFeeCap(),
gasTipCap: msg.GasTipCap(),
value: msg.Value(),
data: msg.Data(),
state: evm.StateDB,
}
}
// ApplyMessage computes the new state by applying the given message
// against the old state within the environment.
//
// ApplyMessage returns the bytes returned by any EVM execution (if it took place),
// the gas used (which includes gas refunds) and an error if it failed. An error always
// indicates a core error meaning that the message would always fail for that particular
// state and would never be accepted within a block.
func ApplyMessage(evm *vm.EVM, msg Message, gp *GasPool) (*ExecutionResult, error) {
return NewStateTransition(evm, msg, gp).TransitionDb()
}
// to returns the recipient of the message.
func (st *StateTransition) to() common.Address {
if st.msg == nil || st.msg.To() == nil /* contract creation */ {
return common.Address{}
}
return *st.msg.To()
}
func (st *StateTransition) buyGas() error {
mgval := new(big.Int).SetUint64(st.msg.Gas())
mgval = mgval.Mul(mgval, st.gasPrice)
balanceCheck := mgval
if st.gasFeeCap != nil {
balanceCheck = new(big.Int).SetUint64(st.msg.Gas())
balanceCheck = balanceCheck.Mul(balanceCheck, st.gasFeeCap)
balanceCheck.Add(balanceCheck, st.value)
}
if have, want := st.state.GetBalance(st.msg.From()), balanceCheck; have.Cmp(want) < 0 {
return fmt.Errorf("%w: address %v have %v want %v", ErrInsufficientFunds, st.msg.From().Hex(), have, want)
}
if err := st.gp.SubGas(st.msg.Gas()); err != nil {
return err
}
st.gas += st.msg.Gas()
st.initialGas = st.msg.Gas()
st.state.SubBalance(st.msg.From(), mgval)
return nil
}
func (st *StateTransition) preCheck() error {
// Only check transactions that are not fake
if !st.msg.IsFake() {
// Make sure this transaction's nonce is correct.
stNonce := st.state.GetNonce(st.msg.From())
if msgNonce := st.msg.Nonce(); stNonce < msgNonce {
return fmt.Errorf("%w: address %v, tx: %d state: %d", ErrNonceTooHigh,
st.msg.From().Hex(), msgNonce, stNonce)
} else if stNonce > msgNonce {
return fmt.Errorf("%w: address %v, tx: %d state: %d", ErrNonceTooLow,
st.msg.From().Hex(), msgNonce, stNonce)
} else if stNonce+1 < stNonce {
return fmt.Errorf("%w: address %v, nonce: %d", ErrNonceMax,
st.msg.From().Hex(), stNonce)
}
// Make sure the sender is an EOA
if codeHash := st.state.GetCodeHash(st.msg.From()); codeHash != emptyCodeHash && codeHash != (common.Hash{}) {
return fmt.Errorf("%w: address %v, codehash: %s", ErrSenderNoEOA,
st.msg.From().Hex(), codeHash)
}
}
// Make sure that transaction gasFeeCap is greater than the baseFee (post london)
if st.evm.ChainConfig().IsLondon(st.evm.Context.BlockNumber) {
// Skip the checks if gas fields are zero and baseFee was explicitly disabled (eth_call)
if !st.evm.Config.NoBaseFee || st.gasFeeCap.BitLen() > 0 || st.gasTipCap.BitLen() > 0 {
if l := st.gasFeeCap.BitLen(); l > 256 {
return fmt.Errorf("%w: address %v, maxFeePerGas bit length: %d", ErrFeeCapVeryHigh,
st.msg.From().Hex(), l)
}
if l := st.gasTipCap.BitLen(); l > 256 {
return fmt.Errorf("%w: address %v, maxPriorityFeePerGas bit length: %d", ErrTipVeryHigh,
st.msg.From().Hex(), l)
}
if st.gasFeeCap.Cmp(st.gasTipCap) < 0 {
return fmt.Errorf("%w: address %v, maxPriorityFeePerGas: %s, maxFeePerGas: %s", ErrTipAboveFeeCap,
st.msg.From().Hex(), st.gasTipCap, st.gasFeeCap)
}
// This will panic if baseFee is nil, but basefee presence is verified
// as part of header validation.
if st.gasFeeCap.Cmp(st.evm.Context.BaseFee) < 0 {
return fmt.Errorf("%w: address %v, maxFeePerGas: %s baseFee: %s", ErrFeeCapTooLow,
st.msg.From().Hex(), st.gasFeeCap, st.evm.Context.BaseFee)
}
}
}
return st.buyGas()
}
// TransitionDb will transition the state by applying the current message and
// returning the evm execution result with following fields.
//
// - used gas: total gas used (including gas being refunded)
// - returndata: the returned data from evm
// - concrete execution error: various EVM errors which abort the execution, e.g.
// ErrOutOfGas, ErrExecutionReverted
//
// However if any consensus issue encountered, return the error directly with
// nil evm execution result.
func (st *StateTransition) TransitionDb() (*ExecutionResult, error) {
// First check this message satisfies all consensus rules before
// applying the message. The rules include these clauses
//
// 1. the nonce of the message caller is correct
// 2. caller has enough balance to cover transaction fee(gaslimit * gasprice)
// 3. the amount of gas required is available in the block
// 4. the purchased gas is enough to cover intrinsic usage
// 5. there is no overflow when calculating intrinsic gas
// 6. caller has enough balance to cover asset transfer for **topmost** call
// Check clauses 1-3, buy gas if everything is correct
if err := st.preCheck(); err != nil {
return nil, err
}
if st.evm.Config.Debug {
st.evm.Config.Tracer.CaptureTxStart(st.initialGas)
defer func() {
st.evm.Config.Tracer.CaptureTxEnd(st.gas)
}()
}
var (
msg = st.msg
sender = vm.AccountRef(msg.From())
rules = st.evm.ChainConfig().Rules(st.evm.Context.BlockNumber, st.evm.Context.Random != nil, st.evm.Context.Time)
contractCreation = msg.To() == nil
)
// Check clauses 4-5, subtract intrinsic gas if everything is correct
gas, err := IntrinsicGas(st.data, st.msg.AccessList(), contractCreation, rules.IsHomestead, rules.IsIstanbul, rules.IsShanghai)
if err != nil {
return nil, err
}
if st.gas < gas {
return nil, fmt.Errorf("%w: have %d, want %d", ErrIntrinsicGas, st.gas, gas)
}
st.gas -= gas
// Check clause 6
if msg.Value().Sign() > 0 && !st.evm.Context.CanTransfer(st.state, msg.From(), msg.Value()) {
return nil, fmt.Errorf("%w: address %v", ErrInsufficientFundsForTransfer, msg.From().Hex())
}
// Check whether the init code size has been exceeded.
if rules.IsShanghai && contractCreation && len(st.data) > params.MaxInitCodeSize {
return nil, fmt.Errorf("%w: code size %v limit %v", ErrMaxInitCodeSizeExceeded, len(st.data), params.MaxInitCodeSize)
}
// Execute the preparatory steps for state transition which includes:
// - prepare accessList(post-berlin)
// - reset transient storage(eip 1153)
st.state.Prepare(rules, msg.From(), st.evm.Context.Coinbase, msg.To(), vm.ActivePrecompiles(rules), msg.AccessList())
var (
ret []byte
vmerr error // vm errors do not effect consensus and are therefore not assigned to err
)
if contractCreation {
ret, _, st.gas, vmerr = st.evm.Create(sender, st.data, st.gas, st.value)
} else {
// Increment the nonce for the next transaction
st.state.SetNonce(msg.From(), st.state.GetNonce(sender.Address())+1)
ret, st.gas, vmerr = st.evm.Call(sender, st.to(), st.data, st.gas, st.value)
}
if !rules.IsLondon {
// Before EIP-3529: refunds were capped to gasUsed / 2
st.refundGas(params.RefundQuotient)
} else {
// After EIP-3529: refunds are capped to gasUsed / 5
st.refundGas(params.RefundQuotientEIP3529)
}
effectiveTip := st.gasPrice
if rules.IsLondon {
effectiveTip = cmath.BigMin(st.gasTipCap, new(big.Int).Sub(st.gasFeeCap, st.evm.Context.BaseFee))
}
if st.evm.Config.NoBaseFee && st.gasFeeCap.Sign() == 0 && st.gasTipCap.Sign() == 0 {
// Skip fee payment when NoBaseFee is set and the fee fields
// are 0. This avoids a negative effectiveTip being applied to
// the coinbase when simulating calls.
} else {
fee := new(big.Int).SetUint64(st.gasUsed())
fee.Mul(fee, effectiveTip)
st.state.AddBalance(st.evm.Context.Coinbase, fee)
}
return &ExecutionResult{
UsedGas: st.gasUsed(),
Err: vmerr,
ReturnData: ret,
}, nil
}
func (st *StateTransition) refundGas(refundQuotient uint64) {
// Apply refund counter, capped to a refund quotient
refund := st.gasUsed() / refundQuotient
if refund > st.state.GetRefund() {
refund = st.state.GetRefund()
}
st.gas += refund
// Return ETH for remaining gas, exchanged at the original rate.
remaining := new(big.Int).Mul(new(big.Int).SetUint64(st.gas), st.gasPrice)
st.state.AddBalance(st.msg.From(), remaining)
// Also return remaining gas to the block gas counter so it is
// available for the next transaction.
st.gp.AddGas(st.gas)
}
// gasUsed returns the amount of gas used up by the state transition.
func (st *StateTransition) gasUsed() uint64 {
return st.initialGas - st.gas
}