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core/vm, protocol_params: implement eip-2565 modexp repricing (#21607)

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* core/vm, protocol_params: implement eip-2565 modexp repricing

* core/vm: fix review concerns
This commit is contained in:
Martin Holst Swende
2020-11-13 13:39:59 +01:00
committed by GitHub
parent 0703c91fba
commit 6f4cccf8d2
4 changed files with 209 additions and 20 deletions
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80
core/vm/contracts.go
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@ -58,7 +58,7 @@ var PrecompiledContractsByzantium = map[common.Address]PrecompiledContract{
common.BytesToAddress([]byte{2}): &sha256hash{},
common.BytesToAddress([]byte{3}): &ripemd160hash{},
common.BytesToAddress([]byte{4}): &dataCopy{},
common.BytesToAddress([]byte{5}): &bigModExp{},
common.BytesToAddress([]byte{5}): &bigModExp{eip2565: false},
common.BytesToAddress([]byte{6}): &bn256AddByzantium{},
common.BytesToAddress([]byte{7}): &bn256ScalarMulByzantium{},
common.BytesToAddress([]byte{8}): &bn256PairingByzantium{},
@ -71,7 +71,7 @@ var PrecompiledContractsIstanbul = map[common.Address]PrecompiledContract{
common.BytesToAddress([]byte{2}): &sha256hash{},
common.BytesToAddress([]byte{3}): &ripemd160hash{},
common.BytesToAddress([]byte{4}): &dataCopy{},
common.BytesToAddress([]byte{5}): &bigModExp{},
common.BytesToAddress([]byte{5}): &bigModExp{eip2565: false},
common.BytesToAddress([]byte{6}): &bn256AddIstanbul{},
common.BytesToAddress([]byte{7}): &bn256ScalarMulIstanbul{},
common.BytesToAddress([]byte{8}): &bn256PairingIstanbul{},
@ -85,7 +85,7 @@ var PrecompiledContractsYoloV2 = map[common.Address]PrecompiledContract{
common.BytesToAddress([]byte{2}): &sha256hash{},
common.BytesToAddress([]byte{3}): &ripemd160hash{},
common.BytesToAddress([]byte{4}): &dataCopy{},
common.BytesToAddress([]byte{5}): &bigModExp{},
common.BytesToAddress([]byte{5}): &bigModExp{eip2565: false},
common.BytesToAddress([]byte{6}): &bn256AddIstanbul{},
common.BytesToAddress([]byte{7}): &bn256ScalarMulIstanbul{},
common.BytesToAddress([]byte{8}): &bn256PairingIstanbul{},
@ -222,14 +222,19 @@ func (c *dataCopy) Run(in []byte) ([]byte, error) {
}
// bigModExp implements a native big integer exponential modular operation.
type bigModExp struct{}
type bigModExp struct {
eip2565 bool
}
var (
big0 = big.NewInt(0)
big1 = big.NewInt(1)
big3 = big.NewInt(3)
big4 = big.NewInt(4)
big7 = big.NewInt(7)
big8 = big.NewInt(8)
big16 = big.NewInt(16)
big20 = big.NewInt(20)
big32 = big.NewInt(32)
big64 = big.NewInt(64)
big96 = big.NewInt(96)
@ -239,6 +244,34 @@ var (
big199680 = big.NewInt(199680)
)
// modexpMultComplexity implements bigModexp multComplexity formula, as defined in EIP-198
//
// def mult_complexity(x):
// if x <= 64: return x ** 2
// elif x <= 1024: return x ** 2 // 4 + 96 * x - 3072
// else: return x ** 2 // 16 + 480 * x - 199680
//
// where is x is max(length_of_MODULUS, length_of_BASE)
func modexpMultComplexity(x *big.Int) *big.Int {
switch {
case x.Cmp(big64) <= 0:
x.Mul(x, x) // x ** 2
case x.Cmp(big1024) <= 0:
// (x ** 2 // 4 ) + ( 96 * x - 3072)
x = new(big.Int).Add(
new(big.Int).Div(new(big.Int).Mul(x, x), big4),
new(big.Int).Sub(new(big.Int).Mul(big96, x), big3072),
)
default:
// (x ** 2 // 16) + (480 * x - 199680)
x = new(big.Int).Add(
new(big.Int).Div(new(big.Int).Mul(x, x), big16),
new(big.Int).Sub(new(big.Int).Mul(big480, x), big199680),
)
}
return x
}
// RequiredGas returns the gas required to execute the pre-compiled contract.
func (c *bigModExp) RequiredGas(input []byte) uint64 {
var (
@ -273,25 +306,36 @@ func (c *bigModExp) RequiredGas(input []byte) uint64 {
adjExpLen.Mul(big8, adjExpLen)
}
adjExpLen.Add(adjExpLen, big.NewInt(int64(msb)))
// Calculate the gas cost of the operation
gas := new(big.Int).Set(math.BigMax(modLen, baseLen))
switch {
case gas.Cmp(big64) <= 0:
if c.eip2565 {
// EIP-2565 has three changes
// 1. Different multComplexity (inlined here)
// in EIP-2565 (https://eips.ethereum.org/EIPS/eip-2565):
//
// def mult_complexity(x):
// ceiling(x/8)^2
//
//where is x is max(length_of_MODULUS, length_of_BASE)
gas = gas.Add(gas, big7)
gas = gas.Div(gas, big8)
gas.Mul(gas, gas)
case gas.Cmp(big1024) <= 0:
gas = new(big.Int).Add(
new(big.Int).Div(new(big.Int).Mul(gas, gas), big4),
new(big.Int).Sub(new(big.Int).Mul(big96, gas), big3072),
)
default:
gas = new(big.Int).Add(
new(big.Int).Div(new(big.Int).Mul(gas, gas), big16),
new(big.Int).Sub(new(big.Int).Mul(big480, gas), big199680),
)
gas.Mul(gas, math.BigMax(adjExpLen, big1))
// 2. Different divisor (`GQUADDIVISOR`) (3)
gas.Div(gas, big3)
if gas.BitLen() > 64 {
return math.MaxUint64
}
// 3. Minimum price of 200 gas
if gas.Uint64() < 200 {
return 200
}
return gas.Uint64()
}
gas = modexpMultComplexity(gas)
gas.Mul(gas, math.BigMax(adjExpLen, big1))
gas.Div(gas, new(big.Int).SetUint64(params.ModExpQuadCoeffDiv))
gas.Div(gas, big20)
if gas.BitLen() > 64 {
return math.MaxUint64