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fuzz.go
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fuzz.go
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package fuzz
import (
"fmt"
"math/rand"
"reflect"
"strconv"
"strings"
"time"
)
// Based on https://github.com/google/gofuzz
// Fuzzer knows how to fill any object with random fields.
type Fuzzer struct {
r *rand.Rand
failRatio float64
}
func randomInt(min, max int) int {
return min + rand.Intn(max-min)
}
// New returns a new Fuzzer.
func New() *Fuzzer {
return NewWithSeed(time.Now().UnixNano())
}
// NewWithSeed returns a new Fuzzer with a specific seed.
func NewWithSeed(seed int64) *Fuzzer {
f := &Fuzzer{
r: rand.New(rand.NewSource(seed)),
}
return f
}
// SetFailureRatio sets the failure ratio for the fuzzer
func (f *Fuzzer) SetFailureRatio(failRatio float64) {
f.failRatio = failRatio
}
// Fuzz recursively fills all of obj's fields with something random
func (f *Fuzzer) Fuzz(obj interface{}) bool {
v := reflect.ValueOf(obj)
if v.Kind() != reflect.Ptr {
panic("needed ptr!")
}
v = v.Elem()
fc := &fuzzerContext{fuzzer: f}
fc.doFuzz(v, "")
return fc.failed
}
type fuzzerContext struct {
fuzzer *Fuzzer
failed bool
}
func convertNum(str string) int {
num, err := strconv.Atoi(str)
if err != nil {
panic(err)
}
return num
}
func (f *Fuzzer) getShoudlFail() bool {
return f.r.Float64() < f.failRatio
}
func (fc *fuzzerContext) getRandomNum(maxStr string, isMax bool) int {
max := convertNum(maxStr)
if max > 5000 {
// hard cap for long values in Beacon state
return 1000
}
if !fc.failed {
if fc.fuzzer.getShoudlFail() {
fc.failed = true
if isMax {
nn := randomInt(max+1, max+10)
return nn
}
// fixed size, return lower and higher values and avoid the
// input value since we already set ourselves as failed
num := randomInt(max-10, max+10)
if num == max {
return num + 1
}
if num < 0 {
num = 1
}
return num
}
}
return max
}
func (fc *fuzzerContext) genElementCount(tag reflect.StructTag) (reflect.StructTag, int) {
if size := tag.Get("ssz-size"); size != "" {
indx := strings.Index(size, ",")
if indx == -1 {
// just one size
return "", fc.getRandomNum(size, false)
}
var num int
if size[:indx] == "?" {
// search for ssz-max tag
max := tag.Get("ssz-max")
if max == "" {
panic("BUG: Max tag expected after ?")
}
num = fc.getRandomNum(max, true)
} else {
// its a number
num = fc.getRandomNum(size[:indx], false)
}
// a,b
return reflect.StructTag("ssz-size:\"" + size[indx+1:] + "\""), num
}
if max := tag.Get("ssz-max"); max != "" {
return "", fc.getRandomNum(max, true)
}
if typ := tag.Get("ssz"); typ != "" {
if typ == "bitlist" {
return "", randomInt(1, 10)
}
}
panic("BUG: Tags not expected")
}
func (fc *fuzzerContext) doFuzz(v reflect.Value, tag reflect.StructTag) {
if !v.CanSet() {
return
}
switch v.Kind() {
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
fuzzUint(v, fc.fuzzer.r)
case reflect.Bool:
v.SetBool(randBool(fc.fuzzer.r))
case reflect.String:
v.SetString(randString(fc.fuzzer.r.Int(), letters))
case reflect.Ptr:
v.Set(reflect.New(v.Type().Elem()))
fc.doFuzz(v.Elem(), "")
return
case reflect.Slice:
subTag, n := fc.genElementCount(tag)
v.Set(reflect.MakeSlice(v.Type(), n, n))
for i := 0; i < n; i++ {
fc.doFuzz(v.Index(i), subTag)
}
case reflect.Struct:
typ := v.Type()
for i := 0; i < v.NumField(); i++ {
// fuzz nil values if the field of the struct is
// another struct
if isPtrToStruct(v.Field(i)) {
if fc.addNil(v.Field(i)) {
continue
}
}
fc.doFuzz(v.Field(i), typ.Field(i).Tag)
}
case reflect.Array:
n := v.Len()
for i := 0; i < n; i++ {
fc.doFuzz(v.Index(i), tag)
}
default:
panic(fmt.Sprintf("Can't handle %#v", v.Interface()))
}
}
func (fc *fuzzerContext) addNil(v reflect.Value) bool {
if !fc.failed {
if fc.fuzzer.getShoudlFail() {
// set to nil, we dont fail because marshal fills empty values
v.Set(reflect.Zero(v.Type()))
return true
}
}
return false
}
func isPtrToStruct(v reflect.Value) bool {
if v.Kind() == reflect.Ptr {
if v.Type().Elem().Kind() == reflect.Struct {
return true
}
}
return false
}
func fuzzInt(v reflect.Value, r *rand.Rand) {
v.SetInt(int64(randUint64(r)))
}
func fuzzUint(v reflect.Value, r *rand.Rand) {
v.SetUint(randUint64(r))
}
func randBool(r *rand.Rand) bool {
if r.Int()&1 == 1 {
return true
}
return false
}
const letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
func randString(n int, dict string) string {
b := make([]byte, n)
for i := range b {
b[i] = dict[rand.Intn(len(dict))]
}
return string(b)
}
func randUint64(r *rand.Rand) uint64 {
return uint64(r.Uint32())<<32 | uint64(r.Uint32())
}