// Copyright 2023 The go-fuzz-headers Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package gofuzzheaders
import (
"archive/tar"
"bytes"
"encoding/binary"
"errors"
"fmt"
"io"
"math"
"os"
"path/filepath"
"reflect"
"strings"
"time"
"unsafe"
securejoin "github.com/cyphar/filepath-securejoin"
)
var (
MaxTotalLen uint32 = 2000000
maxDepth = 100
)
func SetMaxTotalLen(newLen uint32) {
MaxTotalLen = newLen
}
type ConsumeFuzzer struct {
data []byte
dataTotal uint32
CommandPart []byte
RestOfArray []byte
NumberOfCalls int
position uint32
fuzzUnexportedFields bool
curDepth int
Funcs map[reflect.Type]reflect.Value
}
func IsDivisibleBy(n int, divisibleby int) bool {
return (n % divisibleby) == 0
}
func NewConsumer(fuzzData []byte) *ConsumeFuzzer {
return &ConsumeFuzzer{
data: fuzzData,
dataTotal: uint32(len(fuzzData)),
Funcs: make(map[reflect.Type]reflect.Value),
curDepth: 0,
}
}
func (f *ConsumeFuzzer) Split(minCalls, maxCalls int) error {
if f.dataTotal == 0 {
return errors.New("could not split")
}
numberOfCalls := int(f.data[0])
if numberOfCalls < minCalls || numberOfCalls > maxCalls {
return errors.New("bad number of calls")
}
if int(f.dataTotal) < numberOfCalls+numberOfCalls+1 {
return errors.New("length of data does not match required parameters")
}
// Define part 2 and 3 of the data array
commandPart := f.data[1 : numberOfCalls+1]
restOfArray := f.data[numberOfCalls+1:]
// Just a small check. It is necessary
if len(commandPart) != numberOfCalls {
return errors.New("length of commandPart does not match number of calls")
}
// Check if restOfArray is divisible by numberOfCalls
if !IsDivisibleBy(len(restOfArray), numberOfCalls) {
return errors.New("length of commandPart does not match number of calls")
}
f.CommandPart = commandPart
f.RestOfArray = restOfArray
f.NumberOfCalls = numberOfCalls
return nil
}
func (f *ConsumeFuzzer) AllowUnexportedFields() {
f.fuzzUnexportedFields = true
}
func (f *ConsumeFuzzer) DisallowUnexportedFields() {
f.fuzzUnexportedFields = false
}
func (f *ConsumeFuzzer) GenerateStruct(targetStruct interface{}) error {
e := reflect.ValueOf(targetStruct).Elem()
return f.fuzzStruct(e, false)
}
func (f *ConsumeFuzzer) setCustom(v reflect.Value) error {
// First: see if we have a fuzz function for it.
doCustom, ok := f.Funcs[v.Type()]
if !ok {
return fmt.Errorf("could not find a custom function")
}
switch v.Kind() {
case reflect.Ptr:
if v.IsNil() {
if !v.CanSet() {
return fmt.Errorf("could not use a custom function")
}
v.Set(reflect.New(v.Type().Elem()))
}
case reflect.Map:
if v.IsNil() {
if !v.CanSet() {
return fmt.Errorf("could not use a custom function")
}
v.Set(reflect.MakeMap(v.Type()))
}
default:
return fmt.Errorf("could not use a custom function")
}
verr := doCustom.Call([]reflect.Value{v, reflect.ValueOf(Continue{
F: f,
})})
// check if we return an error
if verr[0].IsNil() {
return nil
}
return fmt.Errorf("could not use a custom function")
}
func (f *ConsumeFuzzer) fuzzStruct(e reflect.Value, customFunctions bool) error {
if f.curDepth >= maxDepth {
// return err or nil here?
return nil
}
f.curDepth++
defer func() { f.curDepth-- }()
// We check if we should check for custom functions
if customFunctions && e.IsValid() && e.CanAddr() {
err := f.setCustom(e.Addr())
if err != nil {
return err
}
}
switch e.Kind() {
case reflect.Struct:
for i := 0; i < e.NumField(); i++ {
var v reflect.Value
if !e.Field(i).CanSet() {
if f.fuzzUnexportedFields {
v = reflect.NewAt(e.Field(i).Type(), unsafe.Pointer(e.Field(i).UnsafeAddr())).Elem()
}
if err := f.fuzzStruct(v, customFunctions); err != nil {
return err
}
} else {
v = e.Field(i)
if err := f.fuzzStruct(v, customFunctions); err != nil {
return err
}
}
}
case reflect.String:
str, err := f.GetString()
if err != nil {
return err
}
if e.CanSet() {
e.SetString(str)
}
case reflect.Slice:
var maxElements uint32
// Byte slices should not be restricted
if e.Type().String() == "[]uint8" {
maxElements = 10000000
} else {
maxElements = 50
}
randQty, err := f.GetUint32()
if err != nil {
return err
}
numOfElements := randQty % maxElements
if (f.dataTotal - f.position) < numOfElements {
numOfElements = f.dataTotal - f.position
}
uu := reflect.MakeSlice(e.Type(), int(numOfElements), int(numOfElements))
for i := 0; i < int(numOfElements); i++ {
// If we have more than 10, then we can proceed with that.
if err := f.fuzzStruct(uu.Index(i), customFunctions); err != nil {
if i >= 10 {
if e.CanSet() {
e.Set(uu)
}
return nil
} else {
return err
}
}
}
if e.CanSet() {
e.Set(uu)
}
case reflect.Uint16:
newInt, err := f.GetUint16()
if err != nil {
return err
}
if e.CanSet() {
e.SetUint(uint64(newInt))
}
case reflect.Uint32:
newInt, err := f.GetUint32()
if err != nil {
return err
}
if e.CanSet() {
e.SetUint(uint64(newInt))
}
case reflect.Uint64:
newInt, err := f.GetInt()
if err != nil {
return err
}
if e.CanSet() {
e.SetUint(uint64(newInt))
}
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
newInt, err := f.GetInt()
if err != nil {
return err
}
if e.CanSet() {
e.SetInt(int64(newInt))
}
case reflect.Float32:
newFloat, err := f.GetFloat32()
if err != nil {
return err
}
if e.CanSet() {
e.SetFloat(float64(newFloat))
}
case reflect.Float64:
newFloat, err := f.GetFloat64()
if err != nil {
return err
}
if e.CanSet() {
e.SetFloat(float64(newFloat))
}
case reflect.Map:
if e.CanSet() {
e.Set(reflect.MakeMap(e.Type()))
const maxElements = 50
randQty, err := f.GetInt()
if err != nil {
return err
}
numOfElements := randQty % maxElements
for i := 0; i < numOfElements; i++ {
key := reflect.New(e.Type().Key()).Elem()
if err := f.fuzzStruct(key, customFunctions); err != nil {
return err
}
val := reflect.New(e.Type().Elem()).Elem()
if err = f.fuzzStruct(val, customFunctions); err != nil {
return err
}
e.SetMapIndex(key, val)
}
}
case reflect.Ptr:
if e.CanSet() {
e.Set(reflect.New(e.Type().Elem()))
if err := f.fuzzStruct(e.Elem(), customFunctions); err != nil {
return err
}
return nil
}
case reflect.Uint8:
b, err := f.GetByte()
if err != nil {
return err
}
if e.CanSet() {
e.SetUint(uint64(b))
}
}
return nil
}
func (f *ConsumeFuzzer) GetStringArray() (reflect.Value, error) {
// The max size of the array:
const max uint32 = 20
arraySize := f.position
if arraySize > max {
arraySize = max
}
stringArray := reflect.MakeSlice(reflect.SliceOf(reflect.TypeOf("string")), int(arraySize), int(arraySize))
if f.position+arraySize >= f.dataTotal {
return stringArray, errors.New("could not make string array")
}
for i := 0; i < int(arraySize); i++ {
stringSize := uint32(f.data[f.position])
if f.position+stringSize >= f.dataTotal {
return stringArray, nil
}
stringToAppend := string(f.data[f.position : f.position+stringSize])
strVal := reflect.ValueOf(stringToAppend)
stringArray = reflect.Append(stringArray, strVal)
f.position += stringSize
}
return stringArray, nil
}
func (f *ConsumeFuzzer) GetInt() (int, error) {
if f.position >= f.dataTotal {
return 0, errors.New("not enough bytes to create int")
}
returnInt := int(f.data[f.position])
f.position++
return returnInt, nil
}
func (f *ConsumeFuzzer) GetByte() (byte, error) {
if f.position >= f.dataTotal {
return 0x00, errors.New("not enough bytes to get byte")
}
returnByte := f.data[f.position]
f.position++
return returnByte, nil
}
func (f *ConsumeFuzzer) GetNBytes(numberOfBytes int) ([]byte, error) {
if f.position >= f.dataTotal {
return nil, errors.New("not enough bytes to get byte")
}
returnBytes := make([]byte, 0, numberOfBytes)
for i := 0; i < numberOfBytes; i++ {
newByte, err := f.GetByte()
if err != nil {
return nil, err
}
returnBytes = append(returnBytes, newByte)
}
return returnBytes, nil
}
func (f *ConsumeFuzzer) GetUint16() (uint16, error) {
u16, err := f.GetNBytes(2)
if err != nil {
return 0, err
}
littleEndian, err := f.GetBool()
if err != nil {
return 0, err
}
if littleEndian {
return binary.LittleEndian.Uint16(u16), nil
}
return binary.BigEndian.Uint16(u16), nil
}
func (f *ConsumeFuzzer) GetUint32() (uint32, error) {
i, err := f.GetInt()
if err != nil {
return uint32(0), err
}
return uint32(i), nil
}
func (f *ConsumeFuzzer) GetUint64() (uint64, error) {
u64, err := f.GetNBytes(8)
if err != nil {
return 0, err
}
littleEndian, err := f.GetBool()
if err != nil {
return 0, err
}
if littleEndian {
return binary.LittleEndian.Uint64(u64), nil
}
return binary.BigEndian.Uint64(u64), nil
}
func (f *ConsumeFuzzer) GetBytes() ([]byte, error) {
if f.position >= f.dataTotal {
return nil, errors.New("not enough bytes to create byte array")
}
length, err := f.GetUint32()
if err != nil {
return nil, errors.New("not enough bytes to create byte array")
}
if f.position+length > MaxTotalLen {
return nil, errors.New("created too large a string")
}
byteBegin := f.position - 1
if byteBegin >= f.dataTotal {
return nil, errors.New("not enough bytes to create byte array")
}
if length == 0 {
return nil, errors.New("zero-length is not supported")
}
if byteBegin+length >= f.dataTotal {
return nil, errors.New("not enough bytes to create byte array")
}
if byteBegin+length < byteBegin {
return nil, errors.New("numbers overflow")
}
f.position = byteBegin + length
return f.data[byteBegin:f.position], nil
}
func (f *ConsumeFuzzer) GetString() (string, error) {
if f.position >= f.dataTotal {
return "nil", errors.New("not enough bytes to create string")
}
length, err := f.GetUint32()
if err != nil {
return "nil", errors.New("not enough bytes to create string")
}
if f.position > MaxTotalLen {
return "nil", errors.New("created too large a string")
}
byteBegin := f.position
if byteBegin >= f.dataTotal {
return "nil", errors.New("not enough bytes to create string")
}
if byteBegin+length > f.dataTotal {
return "nil", errors.New("not enough bytes to create string")
}
if byteBegin > byteBegin+length {
return "nil", errors.New("numbers overflow")
}
f.position = byteBegin + length
return string(f.data[byteBegin:f.position]), nil
}
func (f *ConsumeFuzzer) GetBool() (bool, error) {
if f.position >= f.dataTotal {
return false, errors.New("not enough bytes to create bool")
}
if IsDivisibleBy(int(f.data[f.position]), 2) {
f.position++
return true, nil
} else {
f.position++
return false, nil
}
}
func (f *ConsumeFuzzer) FuzzMap(m interface{}) error {
return f.GenerateStruct(m)
}
func returnTarBytes(buf []byte) ([]byte, error) {
// Count files
var fileCounter int
tr := tar.NewReader(bytes.NewReader(buf))
for {
_, err := tr.Next()
if err == io.EOF {
break
}
if err != nil {
return nil, err
}
fileCounter++
}
if fileCounter >= 1 {
return buf, nil
}
return nil, fmt.Errorf("not enough files were created\n")
}
func setTarHeaderFormat(hdr *tar.Header, f *ConsumeFuzzer) error {
ind, err := f.GetInt()
if err != nil {
return err
}
switch ind % 4 {
case 0:
hdr.Format = tar.FormatUnknown
case 1:
hdr.Format = tar.FormatUSTAR
case 2:
hdr.Format = tar.FormatPAX
case 3:
hdr.Format = tar.FormatGNU
}
return nil
}
func setTarHeaderTypeflag(hdr *tar.Header, f *ConsumeFuzzer) error {
ind, err := f.GetInt()
if err != nil {
return err
}
switch ind % 13 {
case 0:
hdr.Typeflag = tar.TypeReg
case 1:
hdr.Typeflag = tar.TypeLink
linkname, err := f.GetString()
if err != nil {
return err
}
hdr.Linkname = linkname
case 2:
hdr.Typeflag = tar.TypeSymlink
linkname, err := f.GetString()
if err != nil {
return err
}
hdr.Linkname = linkname
case 3:
hdr.Typeflag = tar.TypeChar
case 4:
hdr.Typeflag = tar.TypeBlock
case 5:
hdr.Typeflag = tar.TypeDir
case 6:
hdr.Typeflag = tar.TypeFifo
case 7:
hdr.Typeflag = tar.TypeCont
case 8:
hdr.Typeflag = tar.TypeXHeader
case 9:
hdr.Typeflag = tar.TypeXGlobalHeader
case 10:
hdr.Typeflag = tar.TypeGNUSparse
case 11:
hdr.Typeflag = tar.TypeGNULongName
case 12:
hdr.Typeflag = tar.TypeGNULongLink
}
return nil
}
func tooSmallFileBody(length uint32) bool {
if length < 2 {
return true
}
if length < 4 {
return true
}
if length < 10 {
return true
}
if length < 100 {
return true
}
if length < 500 {
return true
}
if length < 1000 {
return true
}
if length < 2000 {
return true
}
if length < 4000 {
return true
}
if length < 8000 {
return true
}
if length < 16000 {
return true
}
if length < 32000 {
return true
}
if length < 64000 {
return true
}
if length < 128000 {
return true
}
if length < 264000 {
return true
}
return false
}
func (f *ConsumeFuzzer) createTarFileBody() ([]byte, error) {
length, err := f.GetUint32()
if err != nil {
return nil, errors.New("not enough bytes to create byte array")
}
shouldUseLargeFileBody, err := f.GetBool()
if err != nil {
return nil, errors.New("not enough bytes to check long file body")
}
if shouldUseLargeFileBody && tooSmallFileBody(length) {
return nil, errors.New("File body was too small")
}
// A bit of optimization to attempt to create a file body
// when we don't have as many bytes left as "length"
remainingBytes := f.dataTotal - f.position
if remainingBytes == 0 {
return nil, errors.New("created too large a string")
}
if f.position+length > MaxTotalLen {
return nil, errors.New("created too large a string")
}
byteBegin := f.position
if byteBegin >= f.dataTotal {
return nil, errors.New("not enough bytes to create byte array")
}
if length == 0 {
return nil, errors.New("zero-length is not supported")
}
if byteBegin+length >= f.dataTotal {
return nil, errors.New("not enough bytes to create byte array")
}
if byteBegin+length < byteBegin {
return nil, errors.New("numbers overflow")
}
f.position = byteBegin + length
return f.data[byteBegin:f.position], nil
}
// getTarFileName is similar to GetString(), but creates string based
// on the length of f.data to reduce the likelihood of overflowing
// f.data.
func (f *ConsumeFuzzer) getTarFilename() (string, error) {
length, err := f.GetUint32()
if err != nil {
return "nil", errors.New("not enough bytes to create string")
}
// A bit of optimization to attempt to create a file name
// when we don't have as many bytes left as "length"
remainingBytes := f.dataTotal - f.position
if remainingBytes == 0 {
return "nil", errors.New("created too large a string")
}
if remainingBytes < 50 {
length = length % remainingBytes
} else if f.dataTotal < 500 {
length = length % f.dataTotal
}
if f.position > MaxTotalLen {
return "nil", errors.New("created too large a string")
}
byteBegin := f.position
if byteBegin >= f.dataTotal {
return "nil", errors.New("not enough bytes to create string")
}
if byteBegin+length > f.dataTotal {
return "nil", errors.New("not enough bytes to create string")
}
if byteBegin > byteBegin+length {
return "nil", errors.New("numbers overflow")
}
f.position = byteBegin + length
return string(f.data[byteBegin:f.position]), nil
}
// TarBytes returns valid bytes for a tar archive
func (f *ConsumeFuzzer) TarBytes() ([]byte, error) {
numberOfFiles, err := f.GetInt()
if err != nil {
return nil, err
}
var buf bytes.Buffer
tw := tar.NewWriter(&buf)
defer tw.Close()
const maxNoOfFiles = 1000
for i := 0; i < numberOfFiles%maxNoOfFiles; i++ {
filename, err := f.getTarFilename()
if err != nil {
return returnTarBytes(buf.Bytes())
}
filebody, err := f.createTarFileBody()
if err != nil {
return returnTarBytes(buf.Bytes())
}
sec, err := f.GetInt()
if err != nil {
return returnTarBytes(buf.Bytes())
}
nsec, err := f.GetInt()
if err != nil {
return returnTarBytes(buf.Bytes())
}
hdr := &tar.Header{
Name: filename,
Size: int64(len(filebody)),
Mode: 0o600,
ModTime: time.Unix(int64(sec), int64(nsec)),
}
if err := setTarHeaderTypeflag(hdr, f); err != nil {
return returnTarBytes(buf.Bytes())
}
if err := setTarHeaderFormat(hdr, f); err != nil {
return returnTarBytes(buf.Bytes())
}
if err := tw.WriteHeader(hdr); err != nil {
return returnTarBytes(buf.Bytes())
}
if _, err := tw.Write(filebody); err != nil {
return returnTarBytes(buf.Bytes())
}
}
return buf.Bytes(), nil
}
// CreateFiles creates pseudo-random files in rootDir.
// It creates subdirs and places the files there.
// It is the callers responsibility to ensure that
// rootDir exists.
func (f *ConsumeFuzzer) CreateFiles(rootDir string) error {
numberOfFiles, err := f.GetInt()
if err != nil {
return err
}
maxNumberOfFiles := numberOfFiles % 4000 // This is completely arbitrary
if maxNumberOfFiles == 0 {
return errors.New("maxNumberOfFiles is nil")
}
var noOfCreatedFiles int
for i := 0; i < maxNumberOfFiles; i++ {
// The file to create:
fileName, err := f.GetString()
if err != nil {
if noOfCreatedFiles > 0 {
// If files have been created, we don't return an error.
break
} else {
return errors.New("could not get fileName")
}
}
fullFilePath, err := securejoin.SecureJoin(rootDir, fileName)
if err != nil {
return err
}
// Find the subdirectory of the file
if subDir := filepath.Dir(fileName); subDir != "" && subDir != "." {
// create the dir first; avoid going outside the root dir
if strings.Contains(subDir, "../") || (len(subDir) > 0 && subDir[0] == 47) || strings.Contains(subDir, "\\") {
continue
}
dirPath, err := securejoin.SecureJoin(rootDir, subDir)
if err != nil {
continue
}
if _, err := os.Stat(dirPath); os.IsNotExist(err) {
err2 := os.MkdirAll(dirPath, 0o777)
if err2 != nil {
continue
}
}
fullFilePath, err = securejoin.SecureJoin(dirPath, fileName)
if err != nil {
continue
}
} else {
// Create symlink
createSymlink, err := f.GetBool()
if err != nil {
if noOfCreatedFiles > 0 {
break
} else {
return errors.New("could not create the symlink")
}
}
if createSymlink {
symlinkTarget, err := f.GetString()
if err != nil {
return err
}
err = os.Symlink(symlinkTarget, fullFilePath)
if err != nil {
return err
}
// stop loop here, since a symlink needs no further action
noOfCreatedFiles++
continue
}
// We create a normal file
fileContents, err := f.GetBytes()
if err != nil {
if noOfCreatedFiles > 0 {
break
} else {
return errors.New("could not create the file")
}
}
err = os.WriteFile(fullFilePath, fileContents, 0o666)
if err != nil {
continue
}
noOfCreatedFiles++
}
}
return nil
}
// GetStringFrom returns a string that can only consist of characters
// included in possibleChars. It returns an error if the created string
// does not have the specified length.
func (f *ConsumeFuzzer) GetStringFrom(possibleChars string, length int) (string, error) {
if (f.dataTotal - f.position) < uint32(length) {
return "", errors.New("not enough bytes to create a string")
}
output := make([]byte, 0, length)
for i := 0; i < length; i++ {
charIndex, err := f.GetInt()
if err != nil {
return string(output), err
}
output = append(output, possibleChars[charIndex%len(possibleChars)])
}
return string(output), nil
}
func (f *ConsumeFuzzer) GetRune() ([]rune, error) {
stringToConvert, err := f.GetString()
if err != nil {
return []rune("nil"), err
}
return []rune(stringToConvert), nil
}
func (f *ConsumeFuzzer) GetFloat32() (float32, error) {
u32, err := f.GetNBytes(4)
if err != nil {
return 0, err
}
littleEndian, err := f.GetBool()
if err != nil {
return 0, err
}
if littleEndian {
u32LE := binary.LittleEndian.Uint32(u32)
return math.Float32frombits(u32LE), nil
}
u32BE := binary.BigEndian.Uint32(u32)
return math.Float32frombits(u32BE), nil
}
func (f *ConsumeFuzzer) GetFloat64() (float64, error) {
u64, err := f.GetNBytes(8)
if err != nil {
return 0, err
}
littleEndian, err := f.GetBool()
if err != nil {
return 0, err
}
if littleEndian {
u64LE := binary.LittleEndian.Uint64(u64)
return math.Float64frombits(u64LE), nil
}
u64BE := binary.BigEndian.Uint64(u64)
return math.Float64frombits(u64BE), nil
}
func (f *ConsumeFuzzer) CreateSlice(targetSlice interface{}) error {
return f.GenerateStruct(targetSlice)
}