main.cpp

/*
Copyright 2020 Google LLC

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

    https://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.
*/

#include "common.h"
#include "fuzzer.h"
#include "mutator.h"
#include "mersenne.h"
#include "mutators/grammar/grammar.h"
#include "mutators/grammar/grammarmutator.h"
#include "mutators/grammar/grammarminimizer.h"


class BinaryFuzzer : public Fuzzer {
  Mutator *CreateMutator(int argc, char **argv, ThreadContext *tc) override;
  bool TrackHotOffsets() override { return true; }
};

Mutator * BinaryFuzzer::CreateMutator(int argc, char **argv, ThreadContext *tc) {
  bool use_deterministic_mutations = true;
  if(GetBinaryOption("-server", argc, argv, false)) {
    // don't do deterministic mutation if a server is specified
    use_deterministic_mutations = false;
  }
  use_deterministic_mutations = GetBinaryOption("-deterministic_mutations",
                                                argc, argv,
                                                use_deterministic_mutations);

  bool deterministic_only = GetBinaryOption("-deterministic_only",
                                            argc, argv,
                                            false);

  int nrounds = GetIntOption("-iterations_per_round", argc, argv, 1000);

  char* dictionary = GetOption("-dict", argc, argv);

  // a pretty simple mutation strategy

  PSelectMutator *pselect = new PSelectMutator();

  // select one of the mutators below with corresponding
  // probablilities
  pselect->AddMutator(new ByteFlipMutator(), 0.8);
  pselect->AddMutator(new ArithmeticMutator(), 0.2);
  pselect->AddMutator(new AppendMutator(1, 128), 0.2);
  pselect->AddMutator(new BlockInsertMutator(1, 128), 0.1);
  pselect->AddMutator(new BlockFlipMutator(2, 16), 0.1);
  pselect->AddMutator(new BlockFlipMutator(16, 64), 0.1);
  pselect->AddMutator(new BlockFlipMutator(1, 64, true), 0.1);
  pselect->AddMutator(new BlockDuplicateMutator(1, 128, 1, 8), 0.1);

  InterestingValueMutator *iv_mutator = new InterestingValueMutator(true);
  if (dictionary) iv_mutator->AddDictionary(dictionary);
  pselect->AddMutator(iv_mutator, 0.1);

  // SpliceMutator is not compatible with -keep_samples_in_memory=0
  // as it requires other samples in memory besides the one being
  // fuzzed.
  if (GetBinaryOption("-keep_samples_in_memory", argc, argv, true)) {
    pselect->AddMutator(new SpliceMutator(1, 0.5), 0.1);
    pselect->AddMutator(new SpliceMutator(2, 0.5), 0.1);
  }

  Mutator* pselect_or_range = pselect;

  // if we are tracking ranges, insert a RangeMutator
  // between RepeatMutator and individual mutators
  if (GetBinaryOption("-track_ranges", argc, argv, false)) {
    RangeMutator* range_mutator = new RangeMutator(pselect);
    pselect_or_range = range_mutator;
  }

  // potentially repeat the mutation
  // (do two or more mutations in a single cycle
  // 0 indicates that actual mutation rate will be adapted
  RepeatMutator *repeater = new RepeatMutator(pselect_or_range, 0);

  if(!use_deterministic_mutations && !deterministic_only) {
    
    // and have nrounds of this per sample cycle
    NRoundMutator *mutator = new NRoundMutator(repeater, nrounds);
    return mutator;
    
  } else {
    
    MutatorSequence *deterministic_sequence = new MutatorSequence(false, true);
    // do deterministic byte flip mutations (around hot bits)
    deterministic_sequence->AddMutator(new DeterministicByteFlipMutator());
    // ..followed by deterministc interesting values
    deterministic_sequence->AddMutator(new DeterministicInterestingValueMutator(true));
    
    size_t deterministic_rounds, nondeterministic_rounds;
    if (deterministic_only) {
      deterministic_rounds = nrounds;
    } else {
      deterministic_rounds = nrounds / 2;
    }
    nondeterministic_rounds = nrounds - deterministic_rounds;

    // do 1000 rounds of derministic mutations, will switch to nondeterministic mutations
    // once deterministic mutator is "done"
    DtermininsticNondeterministicMutator *mutator = 
      new DtermininsticNondeterministicMutator(
        deterministic_sequence, 
        deterministic_rounds,
        repeater,
        nondeterministic_rounds);

    return mutator;
  }
}

class GrammarFuzzer : public Fuzzer {
public:
  GrammarFuzzer(const char *grammar_file);
protected:
  Grammar grammar;
  Mutator* CreateMutator(int argc, char** argv, ThreadContext* tc) override;
  Minimizer* CreateMinimizer(int argc, char** argv, ThreadContext* tc) override;
  bool OutputFilter(Sample* original_sample, Sample* output_sample, ThreadContext* tc) override;

  bool IsReturnValueInteresting(uint64_t return_value) override;
};

GrammarFuzzer::GrammarFuzzer(const char* grammar_file) {
  if (!grammar.Read(grammar_file)) {
    FATAL("Error reading grammar");
  }
}

Mutator* GrammarFuzzer::CreateMutator(int argc, char** argv, ThreadContext* tc) {
  GrammarMutator* grammar_mutator = new GrammarMutator(&grammar);

  NRoundMutator* mutator = new NRoundMutator(grammar_mutator, 20);

  return mutator;
}

Minimizer* GrammarFuzzer::CreateMinimizer(int argc, char** argv, ThreadContext* tc) {
  return new GrammarMinimizer(&grammar);
}

bool GrammarFuzzer::OutputFilter(Sample* original_sample, Sample* output_sample, ThreadContext* tc) {
  uint64_t string_size = *((uint64_t*)original_sample->bytes);
  if (original_sample->size < (string_size + sizeof(string_size))) {
    FATAL("Incorrectly encoded grammar sample");
  }

  output_sample->Init(original_sample->bytes + sizeof(string_size), string_size);
  return true;
}

bool GrammarFuzzer::IsReturnValueInteresting(uint64_t return_value) {
  return (return_value == 0);
}

void TestGrammar(char* grammar_path) {
  Grammar grammar;
  grammar.Read(grammar_path);
  PRNG* prng = new MTPRNG();
  Grammar::TreeNode *tree = grammar.GenerateTree("root", prng);
  if (!tree) {
    printf("Grammar failed to generate sample\n");
  } else {
    std::string out;
    grammar.ToString(tree, out);
    printf("Generated sample:\n%s\n", out.c_str());
  }
}

int main(int argc, char **argv)
{
  Fuzzer* fuzzer;

  char* grammar = GetOption("-test_grammar", argc, argv);
  if (grammar) {
    TestGrammar(grammar);
    return 0;
  }

  grammar = GetOption("-grammar", argc, argv);
  if (grammar) {
    fuzzer = new GrammarFuzzer(grammar);
  } else {
    fuzzer = new BinaryFuzzer();
  }

  fuzzer->Run(argc, argv);
  return 0;
}