core/vm: implements big int expmod precompile - EIP#198

core/vm/contracts.go

@@ -31,11 +31,11 @@ import (
 // requires a deterministic gas count based on the input size of the Run method of the
 // contract.
 type PrecompiledContract interface {
-	RequiredGas(inputSize int) uint64 // RequiredPrice calculates the contract gas use
+	RequiredGas(input []byte) uint64 // RequiredPrice calculates the contract gas use
 	Run(input []byte) []byte         // Run runs the precompiled contract
 }
 
-// Precompiled contains the default set of ethereum contracts
+// PrecompiledContracts contains the default set of ethereum contracts
 var PrecompiledContracts = map[common.Address]PrecompiledContract{
 	common.BytesToAddress([]byte{1}): &ecrecover{},
 	common.BytesToAddress([]byte{2}): &sha256hash{},
@@ -43,9 +43,19 @@ var PrecompiledContracts = map[common.Address]PrecompiledContract{
 	common.BytesToAddress([]byte{4}): &dataCopy{},
 }
 
+// PrecompiledContractsEIP198 contains the default set of ethereum contracts
+// for EIP198.
+var PrecompiledContractsEIP198 = map[common.Address]PrecompiledContract{
+	common.BytesToAddress([]byte{1}): &ecrecover{},
+	common.BytesToAddress([]byte{2}): &sha256{},
+	common.BytesToAddress([]byte{3}): &ripemd160{},
+	common.BytesToAddress([]byte{4}): &dataCopy{},
+	common.BytesToAddress([]byte{5}): &bigModexp{},
+}
+
 // RunPrecompile runs and evaluate the output of a precompiled contract defined in contracts.go
 func RunPrecompiledContract(p PrecompiledContract, input []byte, contract *Contract) (ret []byte, err error) {
-	gas := p.RequiredGas(len(input))
+	gas := p.RequiredGas(input)
 	if contract.UseGas(gas) {
 		ret = p.Run(input)
 
@@ -58,7 +68,7 @@ func RunPrecompiledContract(p PrecompiledContract, input []byte, contract *Contr
 // ECRECOVER implemented as a native contract
 type ecrecover struct{}
 
-func (c *ecrecover) RequiredGas(inputSize int) uint64 {
+func (c *ecrecover) RequiredGas(input []byte) uint64 {
 	return params.EcrecoverGas
 }
 
@@ -97,8 +107,8 @@ type sha256hash struct{}
 //
 // This method does not require any overflow checking as the input size gas costs
 // required for anything significant is so high it's impossible to pay for.
-func (c *sha256hash) RequiredGas(inputSize int) uint64 {
-	return uint64(inputSize+31)/32*params.Sha256WordGas + params.Sha256Gas
+func (c *sha256hash) RequiredGas(input []byte) uint64 {
+	return uint64(len(input)+31)/32*params.Sha256WordGas + params.Sha256Gas
 }
 func (c *sha256hash) Run(in []byte) []byte {
 	h := sha256.Sum256(in)
@@ -112,8 +122,8 @@ type ripemd160hash struct{}
 //
 // This method does not require any overflow checking as the input size gas costs
 // required for anything significant is so high it's impossible to pay for.
-func (c *ripemd160hash) RequiredGas(inputSize int) uint64 {
-	return uint64(inputSize+31)/32*params.Ripemd160WordGas + params.Ripemd160Gas
+func (c *ripemd160hash) RequiredGas(input []byte) uint64 {
+	return uint64(len(input)+31)/32*params.Ripemd160WordGas + params.Ripemd160Gas
 }
 func (c *ripemd160hash) Run(in []byte) []byte {
 	ripemd := ripemd160.New()
@@ -128,9 +138,67 @@ type dataCopy struct{}
 //
 // This method does not require any overflow checking as the input size gas costs
 // required for anything significant is so high it's impossible to pay for.
-func (c *dataCopy) RequiredGas(inputSize int) uint64 {
-	return uint64(inputSize+31)/32*params.IdentityWordGas + params.IdentityGas
+func (c *dataCopy) RequiredGas(input []byte) uint64 {
+	return uint64(len(input)+31)/32*params.IdentityWordGas + params.IdentityGas
 }
 func (c *dataCopy) Run(in []byte) []byte {
 	return in
 }
+
+// bigModexp implements a native big integer exponential modular operation.
+type bigModexp struct{}
+
+// RequiredGas returns the gas required to execute the pre-compiled contract.
+//
+// This method does not require any overflow checking as the input size gas costs
+// required for anything significant is so high it's impossible to pay for.
+func (c *bigModexp) RequiredGas(input []byte) uint64 {
+	// TODO reword required gas to have error reporting and convert arithmetic
+	// to uint64.
+	if len(input) < 3*32 {
+		input = append(input, make([]byte, 3*32-len(input))...)
+	}
+	var (
+		baseLen = common.BytesToBig(input[:31])
+		expLen  = common.BigMax(common.BytesToBig(input[32:64]), big.NewInt(1))
+		modLen  = common.BytesToBig(input[65:97])
+	)
+	x := new(big.Int).Set(common.BigMax(baseLen, modLen))
+	x.Mul(x, x)
+	x.Mul(x, expLen)
+	x.Div(x, new(big.Int).SetUint64(params.QuadCoeffDiv))
+
+	return x.Uint64()
+}
+
+func (c *bigModexp) Run(input []byte) []byte {
+	if len(input) < 3*32 {
+		input = append(input, make([]byte, 3*32-len(input))...)
+	}
+	// why 32-byte? These values won't fit anyway
+	var (
+		baseLen = common.BytesToBig(input[:32]).Uint64()
+		expLen  = common.BytesToBig(input[32:64]).Uint64()
+		modLen  = common.BytesToBig(input[64:96]).Uint64()
+	)
+
+	input = input[96:]
+	if uint64(len(input)) < baseLen {
+		input = append(input, make([]byte, baseLen-uint64(len(input)))...)
+	}
+	base := common.BytesToBig(input[:baseLen])
+
+	input = input[baseLen:]
+	if uint64(len(input)) < expLen {
+		input = append(input, make([]byte, expLen-uint64(len(input)))...)
+	}
+	exp := common.BytesToBig(input[:expLen])
+
+	input = input[expLen:]
+	if uint64(len(input)) < modLen {
+		input = append(input, make([]byte, modLen-uint64(len(input)))...)
+	}
+	mod := common.BytesToBig(input[:modLen])
+
+	return base.Exp(base, exp, mod).Bytes()
+}

core/vm/evm.go

@@ -33,6 +33,22 @@ type (
 	GetHashFunc func(uint64) common.Hash
 )
 
+// run runs the given contract and takes care of running precompiles with a fallback to the byte code interpreter.
+func run(evm *EVM, contract *Contract, input []byte) ([]byte, error) {
+	if contract.CodeAddr != nil {
+		precompiledContracts := PrecompiledContracts
+		if evm.ChainConfig().IsEIP198(evm.BlockNumber) {
+			precompiledContracts = PrecompiledContractsEIP198
+		}
+
+		if p := precompiledContracts[*contract.CodeAddr]; p != nil {
+			return RunPrecompiledContract(p, input, contract)
+		}
+	}
+
+	return evm.interpreter.Run(contract, input)
+}
+
 // Context provides the EVM with auxiliary information. Once provided it shouldn't be modified.
 type Context struct {
 	// CanTransfer returns whether the account contains
@@ -134,7 +150,7 @@ func (evm *EVM) Call(caller ContractRef, addr common.Address, input []byte, gas
 	contract := NewContract(caller, to, value, gas)
 	contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
 
-	ret, err = evm.interpreter.Run(contract, input)
+	ret, err = run(evm, 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.
@@ -175,7 +191,7 @@ func (evm *EVM) CallCode(caller ContractRef, addr common.Address, input []byte,
 	contract := NewContract(caller, to, value, gas)
 	contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
 
-	ret, err = evm.interpreter.Run(contract, input)
+	ret, err = run(evm, contract, input)
 	if err != nil {
 		contract.UseGas(contract.Gas)
 
@@ -210,7 +226,7 @@ func (evm *EVM) DelegateCall(caller ContractRef, addr common.Address, input []by
 	contract := NewContract(caller, to, nil, gas).AsDelegate()
 	contract.SetCallCode(&addr, evm.StateDB.GetCodeHash(addr), evm.StateDB.GetCode(addr))
 
-	ret, err = evm.interpreter.Run(contract, input)
+	ret, err = run(evm, contract, input)
 	if err != nil {
 		contract.UseGas(contract.Gas)
 
@@ -253,8 +269,7 @@ func (evm *EVM) Create(caller ContractRef, code []byte, gas uint64, value *big.I
 	contract := NewContract(caller, AccountRef(contractAddr), value, gas)
 	contract.SetCallCode(&contractAddr, crypto.Keccak256Hash(code), code)
 
-	ret, err = evm.interpreter.Run(contract, nil)
-
+	ret, err = run(evm, 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

core/vm/interpreter.go

@@ -84,12 +84,6 @@ func (evm *Interpreter) Run(contract *Contract, input []byte) (ret []byte, err e
 	evm.env.depth++
 	defer func() { evm.env.depth-- }()
 
-	if contract.CodeAddr != nil {
-		if p := PrecompiledContracts[*contract.CodeAddr]; p != nil {
-			return RunPrecompiledContract(p, input, contract)
-		}
-	}
-
 	// Don't bother with the execution if there's no code.
 	if len(contract.Code) == 0 {
 		return nil, nil

params/config.go

@@ -34,9 +34,10 @@ var (
 		EIP150Hash:     MainNetHomesteadGasRepriceHash,
 		EIP155Block:    MainNetSpuriousDragon,
 		EIP158Block:    MainNetSpuriousDragon,
+		EIP198Block:    MainNetMetropolis,
 	}
 
-	// TestnetChainConfig contains the chain parameters to run a node on the ropsten test network.
+	// TestnetChainConfig is the chain parameters to run a node on the test network.
 	TestnetChainConfig = &ChainConfig{
 		ChainId:        big.NewInt(3),
 		HomesteadBlock: big.NewInt(0),
@@ -46,19 +47,20 @@ var (
 		EIP150Hash:     common.HexToHash("0x41941023680923e0fe4d74a34bdac8141f2540e3ae90623718e47d66d1ca4a2d"),
 		EIP155Block:    big.NewInt(10),
 		EIP158Block:    big.NewInt(10),
+		EIP198Block:    TestNetMetropolis,
 	}
 
 	// AllProtocolChanges contains every protocol change (EIPs)
 	// introduced and accepted by the Ethereum core developers.
-	// TestChainConfig is like AllProtocolChanges but has chain ID 1.
 	//
 	// This configuration is intentionally not using keyed fields.
 	// This configuration must *always* have all forks enabled, which
 	// means that all fields must be set at all times. This forces
 	// anyone adding flags to the config to also have to set these
 	// fields.
-	AllProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0)}
-	TestChainConfig    = &ChainConfig{big.NewInt(1), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0)}
+	AllProtocolChanges = &ChainConfig{big.NewInt(1337), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), big.NewInt(0)}
+	TestChainConfig    = &ChainConfig{big.NewInt(1), big.NewInt(0), nil, false, big.NewInt(0), common.Hash{}, big.NewInt(0), big.NewInt(0), nil}
+	TestRules          = TestChainConfig.Rules(new(big.Int))
 )
 
 // ChainConfig is the core config which determines the blockchain settings.
@@ -79,11 +81,13 @@ type ChainConfig struct {
 
 	EIP155Block *big.Int `json:"eip155Block"` // EIP155 HF block
 	EIP158Block *big.Int `json:"eip158Block"` // EIP158 HF block
+
+	EIP198Block *big.Int `json:"eip198Block"` // EIP198 HF block
 }
 
 // String implements the fmt.Stringer interface.
 func (c *ChainConfig) String() string {
-	return fmt.Sprintf("{ChainID: %v Homestead: %v DAO: %v DAOSupport: %v EIP150: %v EIP155: %v EIP158: %v}",
+	return fmt.Sprintf("{ChainID: %v Homestead: %v DAO: %v DAOSupport: %v EIP150: %v EIP155: %v EIP158: %v EIP198: %v}",
 		c.ChainId,
 		c.HomesteadBlock,
 		c.DAOForkBlock,
@@ -91,6 +95,7 @@ func (c *ChainConfig) String() string {
 		c.EIP150Block,
 		c.EIP155Block,
 		c.EIP158Block,
+		c.EIP198Block,
 	)
 }
 
@@ -200,6 +205,14 @@ func configNumEqual(x, y *big.Int) bool {
 	return x.Cmp(y) == 0
 }
 
+func (c *ChainConfig) IsEIP198(num *big.Int) bool {
+	if c.EIP198Block == nil || num == nil {
+		return false
+	}
+	return num.Cmp(c.EIP198Block) >= 0
+
+}
+
 // ConfigCompatError is raised if the locally-stored blockchain is initialised with a
 // ChainConfig that would alter the past.
 type ConfigCompatError struct {
@@ -230,3 +243,17 @@ func newCompatError(what string, storedblock, newblock *big.Int) *ConfigCompatEr
 func (err *ConfigCompatError) Error() string {
 	return fmt.Sprintf("mismatching %s in database (have %d, want %d, rewindto %d)", err.What, err.StoredConfig, err.NewConfig, err.RewindTo)
 }
+
+// Rules wraps ChainConfig and is merely syntatic sugar or can be used for functions
+// that do not have or require information about the block.
+//
+// Rules is a one time interface meaning that it shouldn't be used in between transition
+// phases.
+type Rules struct {
+	ChainId                                             *big.Int
+	IsHomestead, IsEIP150, IsEIP155, IsEIP158, IsEIP198 bool
+}
+
+func (c *ChainConfig) Rules(num *big.Int) Rules {
+	return Rules{ChainId: new(big.Int).Set(c.ChainId), IsHomestead: c.IsHomestead(num), IsEIP150: c.IsEIP150(num), IsEIP155: c.IsEIP155(num), IsEIP158: c.IsEIP158(num), IsEIP198: c.IsEIP198(num)}
+}

params/util.go

@@ -38,6 +38,9 @@ var (
 	TestNetSpuriousDragon = big.NewInt(10)
 	MainNetSpuriousDragon = big.NewInt(2675000)
 
+	TestNetMetropolis = big.NewInt(11)
+	MainNetMetropolis = big.NewInt(10000000)
+
 	TestNetChainID = big.NewInt(3) // Test net default chain ID
-	MainNetChainID = big.NewInt(1) // Mainnet default chain ID
+	MainNetChainID = big.NewInt(1) // main net default chain ID
 )