forked from cerc-io/plugeth
91 lines
3.0 KiB
Go
91 lines
3.0 KiB
Go
// Copyright 2022 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 modexp
|
|
|
|
import (
|
|
"fmt"
|
|
"math/big"
|
|
|
|
"github.com/ethereum/go-ethereum/common"
|
|
"github.com/ethereum/go-ethereum/core/vm"
|
|
big2 "github.com/holiman/big"
|
|
)
|
|
|
|
// Fuzz is the fuzzing entry-point.
|
|
// The function must return
|
|
//
|
|
// - 1 if the fuzzer should increase priority of the
|
|
// given input during subsequent fuzzing (for example, the input is lexically
|
|
// correct and was parsed successfully);
|
|
// - -1 if the input must not be added to corpus even if gives new coverage; and
|
|
// - 0 otherwise
|
|
//
|
|
// other values are reserved for future use.
|
|
func Fuzz(input []byte) int {
|
|
if len(input) <= 96 {
|
|
return -1
|
|
}
|
|
// Abort on too expensive inputs
|
|
precomp := vm.PrecompiledContractsBerlin[common.BytesToAddress([]byte{5})]
|
|
if gas := precomp.RequiredGas(input); gas > 40_000_000 {
|
|
return 0
|
|
}
|
|
var (
|
|
baseLen = new(big.Int).SetBytes(getData(input, 0, 32)).Uint64()
|
|
expLen = new(big.Int).SetBytes(getData(input, 32, 32)).Uint64()
|
|
modLen = new(big.Int).SetBytes(getData(input, 64, 32)).Uint64()
|
|
)
|
|
// Handle a special case when both the base and mod length is zero
|
|
if baseLen == 0 && modLen == 0 {
|
|
return -1
|
|
}
|
|
input = input[96:]
|
|
// Retrieve the operands and execute the exponentiation
|
|
var (
|
|
base = new(big.Int).SetBytes(getData(input, 0, baseLen))
|
|
exp = new(big.Int).SetBytes(getData(input, baseLen, expLen))
|
|
mod = new(big.Int).SetBytes(getData(input, baseLen+expLen, modLen))
|
|
base2 = new(big2.Int).SetBytes(getData(input, 0, baseLen))
|
|
exp2 = new(big2.Int).SetBytes(getData(input, baseLen, expLen))
|
|
mod2 = new(big2.Int).SetBytes(getData(input, baseLen+expLen, modLen))
|
|
)
|
|
if mod.BitLen() == 0 {
|
|
// Modulo 0 is undefined, return zero
|
|
return -1
|
|
}
|
|
var a = new(big2.Int).Exp(base2, exp2, mod2).String()
|
|
var b = new(big.Int).Exp(base, exp, mod).String()
|
|
if a != b {
|
|
panic(fmt.Sprintf("Inequality %#x ^ %#x mod %#x \n have %s\n want %s", base, exp, mod, a, b))
|
|
}
|
|
return 1
|
|
}
|
|
|
|
// getData returns a slice from the data based on the start and size and pads
|
|
// up to size with zero's. This function is overflow safe.
|
|
func getData(data []byte, start uint64, size uint64) []byte {
|
|
length := uint64(len(data))
|
|
if start > length {
|
|
start = length
|
|
}
|
|
end := start + size
|
|
if end > length {
|
|
end = length
|
|
}
|
|
return common.RightPadBytes(data[start:end], int(size))
|
|
}
|