• Martin Holst Swende's avatar
    core: improve contextual information on core errors (#21869) · 7770e41c
    Martin Holst Swende authored
    A lot of times when we hit 'core' errors, example: invalid tx, the information provided is
    insufficient. We miss several pieces of information: what account has nonce too high,
    and what transaction in that block was offending?
    
    This PR adds that information, using the new type of wrapped errors.
    It also adds a testcase which (partly) verifies the output from the errors.
    
    The first commit changes all usage of direct equality-checks on core errors, into
    using errors.Is. The second commit adds contextual information. This wraps most
    of the core errors with more information, and also wraps it one more time in
    stateprocessor, to further provide tx index and tx hash, if such a tx is encoutered in
    a block. The third commit uses the chainmaker to try to generate chains with such
    errors in them, thus triggering the errors and checking that the generated string meets
    expectations.
    7770e41c
state_transition.go 9.54 KB
// 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"
	"github.com/ethereum/go-ethereum/core/vm"
	"github.com/ethereum/go-ethereum/params"
)

/*
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 \0*32
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
	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
	Gas() uint64
	Value() *big.Int

	Nonce() uint64
	CheckNonce() bool
	Data() []byte
}

// 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, contractCreation, isHomestead bool, isEIP2028 bool) (uint64, error) {
	// Set the starting gas for the raw transaction
	var gas uint64
	if contractCreation && isHomestead {
		gas = params.TxGasContractCreation
	} else {
		gas = params.TxGas
	}
	// Bump the required gas by the amount of transactional data
	if len(data) > 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 := uint64(len(data)) - nz
		if (math.MaxUint64-gas)/params.TxDataZeroGas < z {
			return 0, ErrGasUintOverflow
		}
		gas += z * params.TxDataZeroGas
	}
	return gas, nil
}

// 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(),
		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).Mul(new(big.Int).SetUint64(st.msg.Gas()), st.gasPrice)
	if have, want := st.state.GetBalance(st.msg.From()), mgval; 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 {
	// Make sure this transaction's nonce is correct.
	if st.msg.CheckNonce() {
		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)
		}
	}
	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** error which aborts 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
	}
	msg := st.msg
	sender := vm.AccountRef(msg.From())
	homestead := st.evm.ChainConfig().IsHomestead(st.evm.Context.BlockNumber)
	istanbul := st.evm.ChainConfig().IsIstanbul(st.evm.Context.BlockNumber)
	contractCreation := msg.To() == nil

	// Check clauses 4-5, subtract intrinsic gas if everything is correct
	gas, err := IntrinsicGas(st.data, contractCreation, homestead, istanbul)
	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())
	}
	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)
	}
	st.refundGas()
	st.state.AddBalance(st.evm.Context.Coinbase, new(big.Int).Mul(new(big.Int).SetUint64(st.gasUsed()), st.gasPrice))

	return &ExecutionResult{
		UsedGas:    st.gasUsed(),
		Err:        vmerr,
		ReturnData: ret,
	}, nil
}

func (st *StateTransition) refundGas() {
	// Apply refund counter, capped to half of the used gas.
	refund := st.gasUsed() / 2
	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
}