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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 {
typedef size_t (MutationDispatcher::*Mutator)(uint8_t *Data, size_t Size,
size_t Max);
struct MutationDispatcher::Impl {
std::vector<Unit> Dictionary;
std::vector<Mutator> Mutators;
Impl() {
Mutators.push_back(&MutationDispatcher::Mutate_EraseByte);
Mutators.push_back(&MutationDispatcher::Mutate_InsertByte);
Mutators.push_back(&MutationDispatcher::Mutate_ChangeByte);
Mutators.push_back(&MutationDispatcher::Mutate_ChangeBit);
Mutators.push_back(&MutationDispatcher::Mutate_ShuffleBytes);
}
void AddWordToDictionary(const uint8_t *Word, size_t Size) {
if (Dictionary.empty()) {
Mutators.push_back(&MutationDispatcher::Mutate_AddWordFromDictionary);
}
Dictionary.push_back(Unit(Word, Word + Size));
}
};
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, 8UL)) + 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_AddWordFromDictionary(uint8_t *Data,
size_t Size,
size_t MaxSize) {
auto &D = MDImpl->Dictionary;
assert(!D.empty());
if (D.empty()) return 0;
const Unit &Word = D[Rand(D.size())];
if (Size + Word.size() > MaxSize) return 0;
size_t Idx = Rand(Size + 1);
memmove(Data + Idx + Word.size(), Data + Idx, Size - Idx);
memcpy(Data + Idx, Word.data(), Word.size());
return Size + Word.size();
}
// 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());
size_t NewSize =
(this->*(MDImpl->Mutators[MutatorIdx]))(Data, Size, MaxSize);
if (NewSize) return NewSize;
}
return Size;
}
void MutationDispatcher::AddWordToDictionary(const uint8_t *Word, size_t Size) {
MDImpl->AddWordToDictionary(Word, Size);
}
MutationDispatcher::MutationDispatcher(FuzzerRandomBase &Rand) : Rand(Rand) {
MDImpl = new Impl;
}
MutationDispatcher::~MutationDispatcher() { delete MDImpl; }
} // namespace fuzzer
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