147 lines
4.1 KiB
Go
147 lines
4.1 KiB
Go
// Copyright 2020 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package difficulty
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import (
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"bytes"
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"encoding/binary"
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"fmt"
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"io"
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"math/big"
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"github.com/ethereum/go-ethereum/consensus/ethash"
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"github.com/ethereum/go-ethereum/core/types"
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)
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type fuzzer struct {
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input io.Reader
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exhausted bool
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}
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func (f *fuzzer) read(size int) []byte {
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out := make([]byte, size)
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if _, err := f.input.Read(out); err != nil {
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f.exhausted = true
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}
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return out
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}
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func (f *fuzzer) readSlice(min, max int) []byte {
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var a uint16
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binary.Read(f.input, binary.LittleEndian, &a)
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size := min + int(a)%(max-min)
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out := make([]byte, size)
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if _, err := f.input.Read(out); err != nil {
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f.exhausted = true
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}
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return out
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}
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func (f *fuzzer) readUint64(min, max uint64) uint64 {
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if min == max {
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return min
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}
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var a uint64
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if err := binary.Read(f.input, binary.LittleEndian, &a); err != nil {
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f.exhausted = true
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}
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a = min + a%(max-min)
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return a
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}
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func (f *fuzzer) readBool() bool {
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return f.read(1)[0]&0x1 == 0
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}
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// Fuzz function must return
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//
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// - 1 if the fuzzer should increase priority of the
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// given input during subsequent fuzzing (for example, the input is lexically
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// correct and was parsed successfully);
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// - -1 if the input must not be added to corpus even if gives new coverage; and
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// - 0 otherwise
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//
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// other values are reserved for future use.
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func Fuzz(data []byte) int {
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f := fuzzer{
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input: bytes.NewReader(data),
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exhausted: false,
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}
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return f.fuzz()
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}
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var minDifficulty = big.NewInt(0x2000)
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type calculator func(time uint64, parent *types.Header) *big.Int
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func (f *fuzzer) fuzz() int {
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// A parent header
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header := &types.Header{}
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if f.readBool() {
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header.UncleHash = types.EmptyUncleHash
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}
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// Difficulty can range between 0x2000 (2 bytes) and up to 32 bytes
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{
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diff := new(big.Int).SetBytes(f.readSlice(2, 32))
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if diff.Cmp(minDifficulty) < 0 {
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diff.Set(minDifficulty)
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}
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header.Difficulty = diff
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}
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// Number can range between 0 and up to 32 bytes (but not so that the child exceeds it)
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{
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// However, if we use astronomic numbers, then the bomb exp karatsuba calculation
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// in the legacy methods)
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// times out, so we limit it to fit within reasonable bounds
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number := new(big.Int).SetBytes(f.readSlice(0, 4)) // 4 bytes: 32 bits: block num max 4 billion
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header.Number = number
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}
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// Both parent and child time must fit within uint64
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var time uint64
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{
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childTime := f.readUint64(1, 0xFFFFFFFFFFFFFFFF)
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//fmt.Printf("childTime: %x\n",childTime)
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delta := f.readUint64(1, childTime)
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//fmt.Printf("delta: %v\n", delta)
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pTime := childTime - delta
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header.Time = pTime
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time = childTime
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}
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// Bomb delay will never exceed uint64
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bombDelay := new(big.Int).SetUint64(f.readUint64(1, 0xFFFFFFFFFFFFFFFe))
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if f.exhausted {
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return 0
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}
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for i, pair := range []struct {
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bigFn calculator
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u256Fn calculator
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}{
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{ethash.FrontierDifficultyCalculator, ethash.CalcDifficultyFrontierU256},
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{ethash.HomesteadDifficultyCalculator, ethash.CalcDifficultyHomesteadU256},
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{ethash.DynamicDifficultyCalculator(bombDelay), ethash.MakeDifficultyCalculatorU256(bombDelay)},
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} {
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want := pair.bigFn(time, header)
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have := pair.u256Fn(time, header)
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if want.Cmp(have) != 0 {
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panic(fmt.Sprintf("pair %d: want %x have %x\nparent.Number: %x\np.Time: %x\nc.Time: %x\nBombdelay: %v\n", i, want, have,
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header.Number, header.Time, time, bombDelay))
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}
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}
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return 1
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}
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