tests/fuzzer/flatbuffers_monster_fuzzer.cc

/*
 * Copyright 2014 Google Inc. All rights reserved.
 *
 * 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.
 */

#include <stddef.h>
#include <stdint.h>

#include <clocale>
#include <string>

#include "cpp17/generated_cpp17/monster_test_generated.h"
#include "flatbuffers/idl.h"
#include "test_init.h"

namespace {
constexpr bool use_binary_schema = true;
// should point to flatbuffers/tests/
constexpr const char *test_data_path = "../../";
constexpr const char *schema_file_name = "monster_test";

static constexpr uint8_t flags_strict_json = 0x80;
static constexpr uint8_t flags_skip_unexpected_fields_in_json = 0x40;
static constexpr uint8_t flags_allow_non_utf8 = 0x20;

flatbuffers::Parser make_parser(const flatbuffers::IDLOptions opts) {
  // once loaded from disk
  static const std::string schemafile = [&]() {
    std::string schemafile;
    TEST_EQ(
        flatbuffers::LoadFile((std::string(test_data_path) + schema_file_name +
                               (use_binary_schema ? ".bfbs" : ".fbs"))
                                  .c_str(),
                              use_binary_schema, &schemafile),
        true);

    if (use_binary_schema) {
      flatbuffers::Verifier verifier(
          reinterpret_cast<const uint8_t *>(schemafile.c_str()),
          schemafile.size());
      TEST_EQ(reflection::VerifySchemaBuffer(verifier), true);
    }
    return schemafile;
  }();

  // parse schema first, so we can use it to parse the data after
  flatbuffers::Parser parser;
  if (use_binary_schema) {
    TEST_EQ(parser.Deserialize(
                reinterpret_cast<const uint8_t *>(schemafile.c_str()),
                schemafile.size()),
            true);
  } else {
    auto include_test_path =
        flatbuffers::ConCatPathFileName(test_data_path, "include_test");
    const char *include_directories[] = { test_data_path,
                                          include_test_path.c_str(), nullptr };
    TEST_EQ(parser.Parse(schemafile.c_str(), include_directories), true);
  }
  // (re)define parser options
  parser.opts = opts;
  return parser;
}

std::string do_test(const flatbuffers::IDLOptions &opts,
                    const std::string input_json) {
  auto parser = make_parser(opts);
  std::string jsongen;
  if (parser.ParseJson(input_json.c_str())) {
    flatbuffers::Verifier verifier(parser.builder_.GetBufferPointer(),
                                   parser.builder_.GetSize());
    TEST_EQ(MyGame::Example::VerifyMonsterBuffer(verifier), true);
    TEST_ASSERT(
        GenerateText(parser, parser.builder_.GetBufferPointer(), &jsongen));
  }
  return jsongen;
};
}  // namespace

// Utility for test run.
OneTimeTestInit OneTimeTestInit::one_time_init_;

extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
  // Reserve one byte for Parser flags and one byte for repetition counter.
  if (size < 3) return 0;
  const uint8_t flags = data[0];
  (void)data[1];  //  reserved
  data += 2;
  size -= 2;  // bypass

  const std::string original(reinterpret_cast<const char *>(data), size);
  auto input = std::string(original.c_str());  // until '\0'
  if (input.empty()) return 0;

  flatbuffers::IDLOptions opts;
  opts.strict_json = (flags & flags_strict_json);
  opts.skip_unexpected_fields_in_json =
      (flags & flags_skip_unexpected_fields_in_json);
  opts.allow_non_utf8 = (flags & flags_allow_non_utf8);

  const std::string jsongen_1 = do_test(opts, input);
  if (!jsongen_1.empty()) {
    const std::string jsongen_2 = do_test(opts, jsongen_1);
    TEST_EQ(jsongen_1, jsongen_2);
  }
  return 0;
}