llvm-project/llvm/lib/Fuzzer/FuzzerMutate.cpp

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//===- FuzzerMutate.cpp - Mutate a test input -----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// Mutate a test input.
//===----------------------------------------------------------------------===//
#include <cstring>
#include "FuzzerInternal.h"
#include <algorithm>
namespace fuzzer {
struct Mutator {
size_t (MutationDispatcher::*Fn)(uint8_t *Data, size_t Size, size_t Max);
const char *Name;
};
struct DictionaryEntry {
Word W;
size_t PositionHint;
};
class Dictionary {
public:
static const size_t kMaxDictSize = 1 << 14;
bool ContainsWord(const Word &W) const {
return std::any_of(begin(), end(),
[&](const DictionaryEntry &DE) { return DE.W == W; });
}
const DictionaryEntry *begin() const { return &DE[0]; }
const DictionaryEntry *end() const { return begin() + Size; }
const DictionaryEntry & operator[] (size_t Idx) const {
assert(Idx < Size);
return DE[Idx];
}
void push_back(DictionaryEntry DE) {
if (Size < kMaxDictSize)
this->DE[Size++] = DE;
}
void clear() { Size = 0; }
bool empty() const { return Size == 0; }
size_t size() const { return Size; }
private:
DictionaryEntry DE[kMaxDictSize];
size_t Size = 0;
};
const size_t Dictionary::kMaxDictSize;
struct MutationDispatcher::Impl {
// Dictionary provided by the user via -dict=DICT_FILE.
Dictionary ManualDictionary;
// Temporary dictionary modified by the fuzzer itself,
// recreated periodically.
Dictionary TempAutoDictionary;
// Persistent dictionary modified by the fuzzer, consists of
// entries that led to successfull discoveries in the past mutations.
Dictionary PersistentAutoDictionary;
std::vector<Mutator> Mutators;
std::vector<Mutator> CurrentMutatorSequence;
Dictionary CurrentDictionaryEntrySequence;
const std::vector<Unit> *Corpus = nullptr;
FuzzerRandomBase &Rand;
void Add(Mutator M) { Mutators.push_back(M); }
Impl(FuzzerRandomBase &Rand) : Rand(Rand) {
Add({&MutationDispatcher::Mutate_EraseByte, "EraseByte"});
Add({&MutationDispatcher::Mutate_InsertByte, "InsertByte"});
Add({&MutationDispatcher::Mutate_ChangeByte, "ChangeByte"});
Add({&MutationDispatcher::Mutate_ChangeBit, "ChangeBit"});
Add({&MutationDispatcher::Mutate_ShuffleBytes, "ShuffleBytes"});
Add({&MutationDispatcher::Mutate_ChangeASCIIInteger, "ChangeASCIIInt"});
Add({&MutationDispatcher::Mutate_CrossOver, "CrossOver"});
Add({&MutationDispatcher::Mutate_AddWordFromManualDictionary,
"AddFromManualDict"});
Add({&MutationDispatcher::Mutate_AddWordFromTemporaryAutoDictionary,
"AddFromTempAutoDict"});
Add({&MutationDispatcher::Mutate_AddWordFromPersistentAutoDictionary,
"AddFromPersAutoDict"});
}
void SetCorpus(const std::vector<Unit> *Corpus) { this->Corpus = Corpus; }
size_t AddWordFromDictionary(const Dictionary &D, uint8_t *Data, size_t Size,
size_t MaxSize);
};
static char FlipRandomBit(char X, FuzzerRandomBase &Rand) {
int Bit = Rand(8);
char Mask = 1 << Bit;
char R;
if (X & (1 << Bit))
R = X & ~Mask;
else
R = X | Mask;
assert(R != X);
return R;
}
static char RandCh(FuzzerRandomBase &Rand) {
if (Rand.RandBool()) return Rand(256);
const char *Special = "!*'();:@&=+$,/?%#[]123ABCxyz-`~.";
return Special[Rand(sizeof(Special) - 1)];
}
size_t MutationDispatcher::Mutate_ShuffleBytes(uint8_t *Data, size_t Size,
size_t MaxSize) {
assert(Size);
size_t ShuffleAmount =
Rand(std::min(Size, (size_t)8)) + 1; // [1,8] and <= Size.
size_t ShuffleStart = Rand(Size - ShuffleAmount);
assert(ShuffleStart + ShuffleAmount <= Size);
std::random_shuffle(Data + ShuffleStart, Data + ShuffleStart + ShuffleAmount,
Rand);
return Size;
}
size_t MutationDispatcher::Mutate_EraseByte(uint8_t *Data, size_t Size,
size_t MaxSize) {
assert(Size);
if (Size == 1) return 0;
size_t Idx = Rand(Size);
// Erase Data[Idx].
memmove(Data + Idx, Data + Idx + 1, Size - Idx - 1);
return Size - 1;
}
size_t MutationDispatcher::Mutate_InsertByte(uint8_t *Data, size_t Size,
size_t MaxSize) {
if (Size == MaxSize) return 0;
size_t Idx = Rand(Size + 1);
// Insert new value at Data[Idx].
memmove(Data + Idx + 1, Data + Idx, Size - Idx);
Data[Idx] = RandCh(Rand);
return Size + 1;
}
size_t MutationDispatcher::Mutate_ChangeByte(uint8_t *Data, size_t Size,
size_t MaxSize) {
size_t Idx = Rand(Size);
Data[Idx] = RandCh(Rand);
return Size;
}
size_t MutationDispatcher::Mutate_ChangeBit(uint8_t *Data, size_t Size,
size_t MaxSize) {
size_t Idx = Rand(Size);
Data[Idx] = FlipRandomBit(Data[Idx], Rand);
return Size;
}
size_t MutationDispatcher::Mutate_AddWordFromManualDictionary(uint8_t *Data,
size_t Size,
size_t MaxSize) {
return MDImpl->AddWordFromDictionary(MDImpl->ManualDictionary, Data, Size,
MaxSize);
}
size_t MutationDispatcher::Mutate_AddWordFromTemporaryAutoDictionary(
uint8_t *Data, size_t Size, size_t MaxSize) {
return MDImpl->AddWordFromDictionary(MDImpl->TempAutoDictionary, Data, Size,
MaxSize);
}
size_t MutationDispatcher::Mutate_AddWordFromPersistentAutoDictionary(
uint8_t *Data, size_t Size, size_t MaxSize) {
return MDImpl->AddWordFromDictionary(MDImpl->PersistentAutoDictionary, Data, Size,
MaxSize);
}
size_t MutationDispatcher::Impl::AddWordFromDictionary(const Dictionary &D,
uint8_t *Data,
size_t Size,
size_t MaxSize) {
if (D.empty()) return 0;
const DictionaryEntry &DE = D[Rand(D.size())];
const Word &W = DE.W;
size_t PositionHint = DE.PositionHint;
bool UsePositionHint = PositionHint != std::numeric_limits<size_t>::max() &&
PositionHint + W.size() < Size && Rand.RandBool();
if (Rand.RandBool()) { // Insert W.
if (Size + W.size() > MaxSize) return 0;
size_t Idx = UsePositionHint ? PositionHint : Rand(Size + 1);
memmove(Data + Idx + W.size(), Data + Idx, Size - Idx);
memcpy(Data + Idx, W.data(), W.size());
Size += W.size();
} else { // Overwrite some bytes with W.
if (W.size() > Size) return 0;
size_t Idx = UsePositionHint ? PositionHint : Rand(Size - W.size());
memcpy(Data + Idx, W.data(), W.size());
}
CurrentDictionaryEntrySequence.push_back(DE);
return Size;
}
size_t MutationDispatcher::Mutate_ChangeASCIIInteger(uint8_t *Data, size_t Size,
size_t MaxSize) {
size_t B = Rand(Size);
while (B < Size && !isdigit(Data[B])) B++;
if (B == Size) return 0;
size_t E = B;
while (E < Size && isdigit(Data[E])) E++;
assert(B < E);
// now we have digits in [B, E).
// strtol and friends don't accept non-zero-teminated data, parse it manually.
uint64_t Val = Data[B] - '0';
for (size_t i = B + 1; i < E; i++)
Val = Val * 10 + Data[i] - '0';
// Mutate the integer value.
switch(Rand(5)) {
case 0: Val++; break;
case 1: Val--; break;
case 2: Val /= 2; break;
case 3: Val *= 2; break;
case 4: Val = Rand(Val * Val); break;
default: assert(0);
}
// Just replace the bytes with the new ones, don't bother moving bytes.
for (size_t i = B; i < E; i++) {
size_t Idx = E + B - i - 1;
assert(Idx >= B && Idx < E);
Data[Idx] = (Val % 10) + '0';
Val /= 10;
}
return Size;
}
size_t MutationDispatcher::Mutate_CrossOver(uint8_t *Data, size_t Size,
size_t MaxSize) {
auto Corpus = MDImpl->Corpus;
if (!Corpus || Corpus->size() < 2 || Size == 0) return 0;
size_t Idx = Rand(Corpus->size());
const Unit &Other = (*Corpus)[Idx];
if (Other.empty()) return 0;
Unit U(MaxSize);
size_t NewSize =
CrossOver(Data, Size, Other.data(), Other.size(), U.data(), U.size());
assert(NewSize > 0 && "CrossOver returned empty unit");
assert(NewSize <= MaxSize && "CrossOver returned overisized unit");
memcpy(Data, U.data(), NewSize);
return NewSize;
}
void MutationDispatcher::StartMutationSequence() {
MDImpl->CurrentMutatorSequence.clear();
MDImpl->CurrentDictionaryEntrySequence.clear();
}
// Copy successful dictionary entries to PersistentAutoDictionary.
void MutationDispatcher::RecordSuccessfulMutationSequence() {
for (auto &DE : MDImpl->CurrentDictionaryEntrySequence)
// Linear search is fine here as this happens seldom.
if (!MDImpl->PersistentAutoDictionary.ContainsWord(DE.W))
MDImpl->PersistentAutoDictionary.push_back(
{DE.W, std::numeric_limits<size_t>::max()});
}
void MutationDispatcher::PrintRecommendedDictionary() {
std::vector<Word> V;
for (auto &DE : MDImpl->PersistentAutoDictionary)
if (!MDImpl->ManualDictionary.ContainsWord(DE.W))
V.push_back(DE.W);
if (V.empty()) return;
Printf("###### Recommended dictionary. ######\n");
for (auto &U: V) {
Printf("\"");
PrintASCII(U, "\"\n");
}
Printf("###### End of recommended dictionary. ######\n");
}
void MutationDispatcher::PrintMutationSequence() {
Printf("MS: %zd ", MDImpl->CurrentMutatorSequence.size());
for (auto M : MDImpl->CurrentMutatorSequence)
Printf("%s-", M.Name);
if (!MDImpl->CurrentDictionaryEntrySequence.empty()) {
Printf(" DE: ");
for (auto &DE : MDImpl->CurrentDictionaryEntrySequence) {
Printf("\"");
PrintASCII(DE.W, "\"-");
}
}
}
// Mutates Data in place, returns new size.
size_t MutationDispatcher::Mutate(uint8_t *Data, size_t Size, size_t MaxSize) {
assert(MaxSize > 0);
assert(Size <= MaxSize);
if (Size == 0) {
for (size_t i = 0; i < MaxSize; i++)
Data[i] = RandCh(Rand);
return MaxSize;
}
assert(Size > 0);
// Some mutations may fail (e.g. can't insert more bytes if Size == MaxSize),
// in which case they will return 0.
// Try several times before returning un-mutated data.
for (int Iter = 0; Iter < 10; Iter++) {
size_t MutatorIdx = Rand(MDImpl->Mutators.size());
auto M = MDImpl->Mutators[MutatorIdx];
size_t NewSize = (this->*(M.Fn))(Data, Size, MaxSize);
if (NewSize) {
MDImpl->CurrentMutatorSequence.push_back(M);
return NewSize;
}
}
return Size;
}
void MutationDispatcher::SetCorpus(const std::vector<Unit> *Corpus) {
MDImpl->SetCorpus(Corpus);
}
void MutationDispatcher::AddWordToManualDictionary(const Word &W) {
MDImpl->ManualDictionary.push_back(
{W, std::numeric_limits<size_t>::max()});
}
void MutationDispatcher::AddWordToAutoDictionary(const Word &W,
size_t PositionHint) {
static const size_t kMaxAutoDictSize = 1 << 14;
if (MDImpl->TempAutoDictionary.size() >= kMaxAutoDictSize) return;
MDImpl->TempAutoDictionary.push_back({W, PositionHint});
}
void MutationDispatcher::ClearAutoDictionary() {
MDImpl->TempAutoDictionary.clear();
}
MutationDispatcher::MutationDispatcher(FuzzerRandomBase &Rand) : Rand(Rand) {
MDImpl = new Impl(Rand);
}
MutationDispatcher::~MutationDispatcher() { delete MDImpl; }
} // namespace fuzzer