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// Copyright 2020 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 difficulty
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"math/big"
"github.com/ethereum/go-ethereum/consensus/ethash"
"github.com/ethereum/go-ethereum/core/types"
)
type fuzzer struct {
input io.Reader
exhausted bool
debugging bool
}
func (f *fuzzer) read(size int) []byte {
out := make([]byte, size)
if _, err := f.input.Read(out); err != nil {
f.exhausted = true
}
return out
}
func (f *fuzzer) readSlice(min, max int) []byte {
var a uint16
binary.Read(f.input, binary.LittleEndian, &a)
size := min + int(a)%(max-min)
out := make([]byte, size)
if _, err := f.input.Read(out); err != nil {
f.exhausted = true
}
return out
}
func (f *fuzzer) readUint64(min, max uint64) uint64 {
if min == max {
return min
}
var a uint64
if err := binary.Read(f.input, binary.LittleEndian, &a); err != nil {
f.exhausted = true
}
a = min + a%(max-min)
return a
}
func (f *fuzzer) readBool() bool {
return f.read(1)[0]&0x1 == 0
}
// 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(data []byte) int {
f := fuzzer{
input: bytes.NewReader(data),
exhausted: false,
}
return f.fuzz()
}
var minDifficulty = big.NewInt(0x2000)
type calculator func(time uint64, parent *types.Header) *big.Int
func (f *fuzzer) fuzz() int {
// A parent header
header := &types.Header{}
if f.readBool() {
header.UncleHash = types.EmptyUncleHash
}
// Difficulty can range between 0x2000 (2 bytes) and up to 32 bytes
{
diff := new(big.Int).SetBytes(f.readSlice(2, 32))
if diff.Cmp(minDifficulty) < 0 {
diff.Set(minDifficulty)
}
header.Difficulty = diff
}
// Number can range between 0 and up to 32 bytes (but not so that the child exceeds it)
{
// However, if we use astronomic numbers, then the bomb exp karatsuba calculation
// in the legacy methods)
// times out, so we limit it to fit within reasonable bounds
number := new(big.Int).SetBytes(f.readSlice(0, 4)) // 4 bytes: 32 bits: block num max 4 billion
header.Number = number
}
// Both parent and child time must fit within uint64
var time uint64
{
childTime := f.readUint64(1, 0xFFFFFFFFFFFFFFFF)
//fmt.Printf("childTime: %x\n",childTime)
delta := f.readUint64(1, childTime)
//fmt.Printf("delta: %v\n", delta)
pTime := childTime - delta
header.Time = pTime
time = childTime
}
// Bomb delay will never exceed uint64
bombDelay := new(big.Int).SetUint64(f.readUint64(1, 0xFFFFFFFFFFFFFFFe))
if f.exhausted {
return 0
}
for i, pair := range []struct {
bigFn calculator
u256Fn calculator
}{
{ethash.FrontierDifficultyCalulator, ethash.CalcDifficultyFrontierU256},
{ethash.HomesteadDifficultyCalulator, ethash.CalcDifficultyHomesteadU256},
{ethash.DynamicDifficultyCalculator(bombDelay), ethash.MakeDifficultyCalculatorU256(bombDelay)},
} {
want := pair.bigFn(time, header)
have := pair.u256Fn(time, header)
if want.Cmp(have) != 0 {
panic(fmt.Sprintf("pair %d: want %x have %x\nparent.Number: %x\np.Time: %x\nc.Time: %x\nBombdelay: %v\n", i, want, have,
header.Number, header.Time, time, bombDelay))
}
}
return 1
}