core, core/vm: implemented a generic environment (#3348)

Environment is now a struct (not an interface). This
reduces a lot of tech-debt throughout the codebase where a virtual
machine environment had to be implemented in order to test or run it.

The new environment is suitable to be used en the json tests, core
consensus and light client.

1 files changed, 276 insertions, 87 deletions

diff --git a/core/vm/environment.go b/core/vm/environment.go
index e97c1e58c..50a09d444 100644
--- a/core/vm/environment.go
+++ b/core/vm/environment.go
@@ -17,110 +17,299 @@
 package vm
 
 import (
+	"fmt"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/params"
 )
 
-// Environment is an EVM requirement and helper which allows access to outside
-// information such as states.
-type Environment interface {
-	// The current ruleset
-	ChainConfig() *params.ChainConfig
-	// The state database
-	Db() Database
-	// Creates a restorable snapshot
-	SnapshotDatabase() int
-	// Set database to previous snapshot
-	RevertToSnapshot(int)
-	// Address of the original invoker (first occurrence of the VM invoker)
-	Origin() common.Address
-	// The block number this VM is invoked on
-	BlockNumber() *big.Int
-	// The n'th hash ago from this block number
-	GetHash(uint64) common.Hash
-	// The handler's address
-	Coinbase() common.Address
-	// The current time (block time)
-	Time() *big.Int
-	// Difficulty set on the current block
-	Difficulty() *big.Int
-	// The gas limit of the block
-	GasLimit() *big.Int
-	// Determines whether it's possible to transact
-	CanTransfer(from common.Address, balance *big.Int) bool
-	// Transfers amount from one account to the other
-	Transfer(from, to Account, amount *big.Int)
-	// Adds a LOG to the state
-	AddLog(*Log)
-	// Type of the VM
-	Vm() Vm
-	// Get the curret calling depth
-	Depth() int
-	// Set the current calling depth
-	SetDepth(i int)
-	// Call another contract
-	Call(me ContractRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
-	// Take another's contract code and execute within our own context
-	CallCode(me ContractRef, addr common.Address, data []byte, gas, price, value *big.Int) ([]byte, error)
-	// Same as CallCode except sender and value is propagated from parent to child scope
-	DelegateCall(me ContractRef, addr common.Address, data []byte, gas, price *big.Int) ([]byte, error)
-	// Create a new contract
-	Create(me ContractRef, data []byte, gas, price, value *big.Int) ([]byte, common.Address, error)
+type (
+	CanTransferFunc func(StateDB, common.Address, *big.Int) bool
+	TransferFunc    func(StateDB, common.Address, common.Address, *big.Int)
+	// GetHashFunc returns the nth block hash in the blockchain
+	// and is used by the BLOCKHASH EVM op code.
+	GetHashFunc func(uint64) common.Hash
+)
+
+// Context provides the EVM with auxilary information. Once provided it shouldn't be modified.
+type Context struct {
+	// CanTransfer returns whether the account contains
+	// sufficient ether to transfer the value
+	CanTransfer CanTransferFunc
+	// Transfer transfers ether from one account to the other
+	Transfer TransferFunc
+	// GetHash returns the hash corresponding to n
+	GetHash GetHashFunc
+
+	// Message information
+	Origin   common.Address // Provides information for ORIGIN
+	GasPrice *big.Int       // Provides information for GASPRICE
+
+	// Block information
+	Coinbase    common.Address // Provides information for COINBASE
+	GasLimit    *big.Int       // Provides information for GASLIMIT
+	BlockNumber *big.Int       // Provides information for NUMBER
+	Time        *big.Int       // Provides information for TIME
+	Difficulty  *big.Int       // Provides information for DIFFICULTY
+}
+
+// Environment provides information about external sources for the EVM
+//
+// The Environment should never be reused and is not thread safe.
+type Environment struct {
+	// Context provides auxiliary blockchain related information
+	Context
+	// StateDB gives access to the underlying state
+	StateDB StateDB
+	// Depth is the current call stack
+	Depth int
+
+	// evm is the ethereum virtual machine
+	evm Vm
+	// chainConfig contains information about the current chain
+	chainConfig *params.ChainConfig
+	vmConfig    Config
+}
+
+// NewEnvironment retutrns a new EVM environment.
+func NewEnvironment(context Context, statedb StateDB, chainConfig *params.ChainConfig, vmConfig Config) *Environment {
+	env := &Environment{
+		Context:     context,
+		StateDB:     statedb,
+		vmConfig:    vmConfig,
+		chainConfig: chainConfig,
+	}
+	env.evm = New(env, vmConfig)
+	return env
+}
+
+// Call executes the contract associated with the addr with the given input as paramaters. It also handles any
+// necessary value transfer required and takes the necessary steps to create accounts and reverses the state in
+// case of an execution error or failed value transfer.
+func (env *Environment) Call(caller ContractRef, addr common.Address, input []byte, gas, value *big.Int) ([]byte, error) {
+	if env.vmConfig.NoRecursion && env.Depth > 0 {
+		caller.ReturnGas(gas)
+
+		return nil, nil
+	}
+
+	// Depth check execution. Fail if we're trying to execute above the
+	// limit.
+	if env.Depth > int(params.CallCreateDepth.Int64()) {
+		caller.ReturnGas(gas)
+
+		return nil, DepthError
+	}
+	if !env.Context.CanTransfer(env.StateDB, caller.Address(), value) {
+		caller.ReturnGas(gas)
+
+		return nil, ErrInsufficientBalance
+	}
+
+	var (
+		to                  Account
+		snapshotPreTransfer = env.StateDB.Snapshot()
+	)
+	if !env.StateDB.Exist(addr) {
+		if Precompiled[addr.Str()] == nil && env.ChainConfig().IsEIP158(env.BlockNumber) && value.BitLen() == 0 {
+			caller.ReturnGas(gas)
+			return nil, nil
+		}
+
+		to = env.StateDB.CreateAccount(addr)
+	} else {
+		to = env.StateDB.GetAccount(addr)
+	}
+	env.Transfer(env.StateDB, caller.Address(), to.Address(), value)
+
+	// initialise a new contract and set the code that is to be used by the
+	// E The contract is a scoped environment for this execution context
+	// only.
+	contract := NewContract(caller, to, value, gas)
+	contract.SetCallCode(&addr, env.StateDB.GetCodeHash(addr), env.StateDB.GetCode(addr))
+	defer contract.Finalise()
+
+	ret, err := env.EVM().Run(contract, input)
+	// When an error was returned by the EVM or when setting the creation code
+	// above we revert to the snapshot and consume any gas remaining. Additionally
+	// when we're in homestead this also counts for code storage gas errors.
+	if err != nil {
+		contract.UseGas(contract.Gas)
+
+		env.StateDB.RevertToSnapshot(snapshotPreTransfer)
+	}
+	return ret, err
 }
 
-// Vm is the basic interface for an implementation of the EVM.
-type Vm interface {
-	// Run should execute the given contract with the input given in in
-	// and return the contract execution return bytes or an error if it
-	// failed.
-	Run(c *Contract, in []byte) ([]byte, error)
+// CallCode executes the contract associated with the addr with the given input as paramaters. It also handles any
+// necessary value transfer required and takes the necessary steps to create accounts and reverses the state in
+// case of an execution error or failed value transfer.
+//
+// CallCode differs from Call in the sense that it executes the given address' code with the caller as context.
+func (env *Environment) CallCode(caller ContractRef, addr common.Address, input []byte, gas, value *big.Int) ([]byte, error) {
+	if env.vmConfig.NoRecursion && env.Depth > 0 {
+		caller.ReturnGas(gas)
+
+		return nil, nil
+	}
+
+	// Depth check execution. Fail if we're trying to execute above the
+	// limit.
+	if env.Depth > int(params.CallCreateDepth.Int64()) {
+		caller.ReturnGas(gas)
+
+		return nil, DepthError
+	}
+	if !env.CanTransfer(env.StateDB, caller.Address(), value) {
+		caller.ReturnGas(gas)
+
+		return nil, fmt.Errorf("insufficient funds to transfer value. Req %v, has %v", value, env.StateDB.GetBalance(caller.Address()))
+	}
+
+	var (
+		snapshotPreTransfer = env.StateDB.Snapshot()
+		to                  = env.StateDB.GetAccount(caller.Address())
+	)
+	// initialise a new contract and set the code that is to be used by the
+	// E The contract is a scoped environment for this execution context
+	// only.
+	contract := NewContract(caller, to, value, gas)
+	contract.SetCallCode(&addr, env.StateDB.GetCodeHash(addr), env.StateDB.GetCode(addr))
+	defer contract.Finalise()
+
+	ret, err := env.EVM().Run(contract, input)
+	if err != nil {
+		contract.UseGas(contract.Gas)
+
+		env.StateDB.RevertToSnapshot(snapshotPreTransfer)
+	}
+
+	return ret, err
 }
 
-// Database is a EVM database for full state querying.
-type Database interface {
-	GetAccount(common.Address) Account
-	CreateAccount(common.Address) Account
+// DelegateCall executes the contract associated with the addr with the given input as paramaters.
+// It reverses the state in case of an execution error.
+//
+// DelegateCall differs from CallCode in the sense that it executes the given address' code with the caller as context
+// and the caller is set to the caller of the caller.
+func (env *Environment) DelegateCall(caller ContractRef, addr common.Address, input []byte, gas *big.Int) ([]byte, error) {
+	if env.vmConfig.NoRecursion && env.Depth > 0 {
+		caller.ReturnGas(gas)
 
-	AddBalance(common.Address, *big.Int)
-	GetBalance(common.Address) *big.Int
+		return nil, nil
+	}
 
-	GetNonce(common.Address) uint64
-	SetNonce(common.Address, uint64)
+	// Depth check execution. Fail if we're trying to execute above the
+	// limit.
+	if env.Depth > int(params.CallCreateDepth.Int64()) {
+		caller.ReturnGas(gas)
+		return nil, DepthError
+	}
 
-	GetCodeHash(common.Address) common.Hash
-	GetCodeSize(common.Address) int
-	GetCode(common.Address) []byte
-	SetCode(common.Address, []byte)
+	var (
+		snapshot = env.StateDB.Snapshot()
+		to       = env.StateDB.GetAccount(caller.Address())
+	)
 
-	AddRefund(*big.Int)
-	GetRefund() *big.Int
+	// Iinitialise a new contract and make initialise the delegate values
+	contract := NewContract(caller, to, caller.Value(), gas).AsDelegate()
+	contract.SetCallCode(&addr, env.StateDB.GetCodeHash(addr), env.StateDB.GetCode(addr))
+	defer contract.Finalise()
 
-	GetState(common.Address, common.Hash) common.Hash
-	SetState(common.Address, common.Hash, common.Hash)
+	ret, err := env.EVM().Run(contract, input)
+	if err != nil {
+		contract.UseGas(contract.Gas)
 
-	Suicide(common.Address) bool
-	HasSuicided(common.Address) bool
+		env.StateDB.RevertToSnapshot(snapshot)
+	}
 
-	// Exist reports whether the given account exists in state.
-	// Notably this should also return true for suicided accounts.
-	Exist(common.Address) bool
-	// Empty returns whether the given account is empty. Empty
-	// is defined according to EIP161 (balance = nonce = code = 0).
-	Empty(common.Address) bool
+	return ret, err
 }
 
-// Account represents a contract or basic ethereum account.
-type Account interface {
-	SubBalance(amount *big.Int)
-	AddBalance(amount *big.Int)
-	SetBalance(*big.Int)
-	SetNonce(uint64)
-	Balance() *big.Int
-	Address() common.Address
-	ReturnGas(*big.Int, *big.Int)
-	SetCode(common.Hash, []byte)
-	ForEachStorage(cb func(key, value common.Hash) bool)
-	Value() *big.Int
+// Create creates a new contract using code as deployment code.
+func (env *Environment) Create(caller ContractRef, code []byte, gas, value *big.Int) ([]byte, common.Address, error) {
+	if env.vmConfig.NoRecursion && env.Depth > 0 {
+		caller.ReturnGas(gas)
+
+		return nil, common.Address{}, nil
+	}
+
+	// Depth check execution. Fail if we're trying to execute above the
+	// limit.
+	if env.Depth > int(params.CallCreateDepth.Int64()) {
+		caller.ReturnGas(gas)
+
+		return nil, common.Address{}, DepthError
+	}
+	if !env.CanTransfer(env.StateDB, caller.Address(), value) {
+		caller.ReturnGas(gas)
+
+		return nil, common.Address{}, ErrInsufficientBalance
+	}
+
+	// Create a new account on the state
+	nonce := env.StateDB.GetNonce(caller.Address())
+	env.StateDB.SetNonce(caller.Address(), nonce+1)
+
+	snapshotPreTransfer := env.StateDB.Snapshot()
+	var (
+		addr = crypto.CreateAddress(caller.Address(), nonce)
+		to   = env.StateDB.CreateAccount(addr)
+	)
+	if env.ChainConfig().IsEIP158(env.BlockNumber) {
+		env.StateDB.SetNonce(addr, 1)
+	}
+	env.Transfer(env.StateDB, caller.Address(), to.Address(), value)
+
+	// initialise a new contract and set the code that is to be used by the
+	// E The contract is a scoped environment for this execution context
+	// only.
+	contract := NewContract(caller, to, value, gas)
+	contract.SetCallCode(&addr, crypto.Keccak256Hash(code), code)
+	defer contract.Finalise()
+
+	ret, err := env.EVM().Run(contract, nil)
+	// check whether the max code size has been exceeded
+	maxCodeSizeExceeded := len(ret) > params.MaxCodeSize
+	// if the contract creation ran successfully and no errors were returned
+	// calculate the gas required to store the code. If the code could not
+	// be stored due to not enough gas set an error and let it be handled
+	// by the error checking condition below.
+	if err == nil && !maxCodeSizeExceeded {
+		dataGas := big.NewInt(int64(len(ret)))
+		dataGas.Mul(dataGas, params.CreateDataGas)
+		if contract.UseGas(dataGas) {
+			env.StateDB.SetCode(addr, ret)
+		} else {
+			err = CodeStoreOutOfGasError
+		}
+	}
+
+	// When an error was returned by the EVM or when setting the creation code
+	// above we revert to the snapshot and consume any gas remaining. Additionally
+	// when we're in homestead this also counts for code storage gas errors.
+	if maxCodeSizeExceeded ||
+		(err != nil && (env.ChainConfig().IsHomestead(env.BlockNumber) || err != CodeStoreOutOfGasError)) {
+		contract.UseGas(contract.Gas)
+		env.StateDB.RevertToSnapshot(snapshotPreTransfer)
+
+		// Nothing should be returned when an error is thrown.
+		return nil, addr, err
+	}
+	// If the vm returned with an error the return value should be set to nil.
+	// This isn't consensus critical but merely to for behaviour reasons such as
+	// tests, RPC calls, etc.
+	if err != nil {
+		ret = nil
+	}
+
+	return ret, addr, err
 }
+
+// ChainConfig returns the environment's chain configuration
+func (env *Environment) ChainConfig() *params.ChainConfig { return env.chainConfig }
+
+// EVM returns the environments EVM
+func (env *Environment) EVM() Vm { return env.evm }