bisector.py

# Copyright 2019 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
#
#      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.
"""Uses bisection to determine which commit a bug was introduced and fixed.
This module takes a high and a low commit SHA, a repo name, and a bug.
The module bisects the high and low commit SHA searching for the location
where the bug was introduced. It also looks for where the bug was fixed.
This is done with the following steps:


  NOTE: Needs to be run from root of the OSS-Fuzz source checkout.

  Typical usage example:
        python3 infra/bisector.py
          --old_commit 1e403e9259a1abedf108ab86f711ba52c907226d
          --new_commit f79be4f2330f4b89ea2f42e1c44ca998c59a0c0f
          --fuzz_target rules_fuzzer
          --project_name yara
          --testcase infra/yara_testcase
          --sanitizer address
"""

import argparse
import collections
import logging
import os
import sys
import tempfile

import build_specified_commit
import helper
import repo_manager
import utils

Result = collections.namedtuple('Result', ['repo_url', 'commit'])

START_MARKERS = [
    '==ERROR',
    '==WARNING',
]

END_MARKERS = [
    'SUMMARY:',
]

DEDUP_TOKEN_MARKER = 'DEDUP_TOKEN:'


class BisectError(Exception):
  """Bisection error."""

  def __init__(self, message, repo_url):
    super().__init__(message)
    self.repo_url = repo_url


def main():
  """Finds the commit SHA where an error was initally introduced."""
  logging.getLogger().setLevel(logging.INFO)
  utils.chdir_to_root()
  parser = argparse.ArgumentParser(
      description='git bisection for finding introduction of bugs')

  parser.add_argument('--project_name',
                      help='The name of the project where the bug occurred.',
                      required=True)
  parser.add_argument('--new_commit',
                      help='The newest commit SHA to be bisected.',
                      required=True)
  parser.add_argument('--old_commit',
                      help='The oldest commit SHA to be bisected.',
                      required=True)
  parser.add_argument('--fuzz_target',
                      help='The name of the fuzzer to be built.',
                      required=True)
  parser.add_argument('--test_case_path',
                      help='The path to test case.',
                      required=True)
  parser.add_argument('--engine',
                      help='The default is "libfuzzer".',
                      default='libfuzzer')
  parser.add_argument('--sanitizer',
                      default='address',
                      help='The default is "address".')
  parser.add_argument('--type',
                      choices=['regressed', 'fixed'],
                      help='The bisection type.',
                      required=True)
  parser.add_argument('--architecture', default='x86_64')
  args = parser.parse_args()

  build_data = build_specified_commit.BuildData(project_name=args.project_name,
                                                engine=args.engine,
                                                sanitizer=args.sanitizer,
                                                architecture=args.architecture)

  result = bisect(args.type, args.old_commit, args.new_commit,
                  args.test_case_path, args.fuzz_target, build_data)
  if not result.commit:
    logging.error('No error was found in commit range %s:%s', args.old_commit,
                  args.new_commit)
    return 1
  if result.commit == args.old_commit:
    logging.error(
        'Bisection Error: Both the first and the last commits in'
        'the given range have the same behavior, bisection is not possible. ')
    return 1
  if args.type == 'regressed':
    print('Error was introduced at commit %s' % result.commit)
  elif args.type == 'fixed':
    print('Error was fixed at commit %s' % result.commit)
  return 0


def _get_dedup_token(output):
  """Get dedup token."""
  for line in output.splitlines():
    token_location = line.find(DEDUP_TOKEN_MARKER)
    if token_location == -1:
      continue

    return line[token_location + len(DEDUP_TOKEN_MARKER):].strip()

  return None


def _check_for_crash(project_name, fuzz_target, testcase_path):
  """Check for crash."""

  def docker_run(args, **kwargs):
    del kwargs
    command = ['docker', 'run', '--rm', '--privileged']
    if sys.stdin.isatty():
      command.append('-i')

    return utils.execute(command + args)

  logging.info('Checking for crash')
  out, err, return_code = helper.reproduce_impl(
      project=helper.Project(project_name),
      fuzzer_name=fuzz_target,
      valgrind=False,
      env_to_add=[],
      fuzzer_args=[],
      testcase_path=testcase_path,
      run_function=docker_run,
      err_result=(None, None, None))
  if return_code is None:
    return None

  logging.info('stdout =\n%s', out)
  logging.info('stderr =\n%s', err)

  # pylint: disable=unsupported-membership-test
  has_start_marker = any(
      marker in out or marker in err for marker in START_MARKERS)
  has_end_marker = any(marker in out or marker in err for marker in END_MARKERS)
  if not has_start_marker or not has_end_marker:
    return None

  return _get_dedup_token(out + err)


# pylint: disable=too-many-locals
# pylint: disable=too-many-arguments
# pylint: disable=too-many-statements
def _bisect(bisect_type, old_commit, new_commit, testcase_path, fuzz_target,
            build_data):
  """Perform the bisect."""
  # pylint: disable=too-many-branches
  base_builder_repo = build_specified_commit.load_base_builder_repo()

  with tempfile.TemporaryDirectory() as tmp_dir:
    repo_url, repo_path = build_specified_commit.detect_main_repo(
        build_data.project_name, commit=new_commit)
    if not repo_url or not repo_path:
      raise ValueError('Main git repo can not be determined.')

    if old_commit == new_commit:
      raise BisectError('old_commit is the same as new_commit', repo_url)

    # Copy /src from the built Docker container to ensure all dependencies
    # exist. This will be mounted when running them.
    host_src_dir = build_specified_commit.copy_src_from_docker(
        build_data.project_name, tmp_dir)

    bisect_repo_manager = repo_manager.RepoManager(
        os.path.join(host_src_dir, os.path.basename(repo_path)))
    bisect_repo_manager.fetch_all_remotes()

    commit_list = bisect_repo_manager.get_commit_list(new_commit, old_commit)

    old_idx = len(commit_list) - 1
    new_idx = 0
    logging.info('Testing against new_commit (%s)', commit_list[new_idx])
    if not build_specified_commit.build_fuzzers_from_commit(
        commit_list[new_idx],
        bisect_repo_manager,
        host_src_dir,
        build_data,
        base_builder_repo=base_builder_repo):
      raise BisectError('Failed to build new_commit', repo_url)

    if bisect_type == 'fixed':
      should_crash = False
    elif bisect_type == 'regressed':
      should_crash = True
    else:
      raise BisectError('Invalid bisect type ' + bisect_type, repo_url)

    expected_error = _check_for_crash(build_data.project_name, fuzz_target,
                                      testcase_path)
    logging.info('new_commit result = %s', expected_error)

    if not should_crash and expected_error:
      logging.warning('new_commit crashed but not shouldn\'t. '
                      'Continuing to see if stack changes.')

    range_valid = False
    for _ in range(2):
      logging.info('Testing against old_commit (%s)', commit_list[old_idx])
      if not build_specified_commit.build_fuzzers_from_commit(
          commit_list[old_idx],
          bisect_repo_manager,
          host_src_dir,
          build_data,
          base_builder_repo=base_builder_repo):
        raise BisectError('Failed to build old_commit', repo_url)

      if _check_for_crash(build_data.project_name, fuzz_target,
                          testcase_path) == expected_error:
        logging.warning('old_commit %s had same result as new_commit %s',
                        old_commit, new_commit)
        # Try again on an slightly older commit.
        old_commit = bisect_repo_manager.get_parent(old_commit, 64)
        if not old_commit:
          break

        commit_list = bisect_repo_manager.get_commit_list(
            new_commit, old_commit)
        old_idx = len(commit_list) - 1
        continue

      range_valid = True
      break

    if not range_valid:
      raise BisectError('old_commit had same result as new_commit', repo_url)

    while old_idx - new_idx > 1:
      curr_idx = (old_idx + new_idx) // 2
      logging.info('Testing against %s (idx=%d)', commit_list[curr_idx],
                   curr_idx)
      if not build_specified_commit.build_fuzzers_from_commit(
          commit_list[curr_idx],
          bisect_repo_manager,
          host_src_dir,
          build_data,
          base_builder_repo=base_builder_repo):
        # Treat build failures as if we couldn't repo.
        # TODO(ochang): retry nearby commits?
        old_idx = curr_idx
        continue

      current_error = _check_for_crash(build_data.project_name, fuzz_target,
                                       testcase_path)
      logging.info('Current result = %s', current_error)
      if expected_error == current_error:
        new_idx = curr_idx
      else:
        old_idx = curr_idx
    return Result(repo_url, commit_list[new_idx])


# pylint: disable=too-many-locals
# pylint: disable=too-many-arguments
def bisect(bisect_type, old_commit, new_commit, testcase_path, fuzz_target,
           build_data):
  """From a commit range, this function caluclates which introduced a
  specific error from a fuzz testcase_path.

  Args:
    bisect_type: The type of the bisect ('regressed' or 'fixed').
    old_commit: The oldest commit in the error regression range.
    new_commit: The newest commit in the error regression range.
    testcase_path: The file path of the test case that triggers the error
    fuzz_target: The name of the fuzzer to be tested.
    build_data: a class holding all of the input parameters for bisection.

  Returns:
    The commit SHA that introduced the error or None.

  Raises:
    ValueError: when a repo url can't be determine from the project.
  """
  try:
    return _bisect(bisect_type, old_commit, new_commit, testcase_path,
                   fuzz_target, build_data)
  finally:
    # Clean up projects/ as _bisect may have modified it.
    oss_fuzz_repo_manager = repo_manager.RepoManager(helper.OSS_FUZZ_DIR)
    oss_fuzz_repo_manager.git(['reset', 'projects'])
    oss_fuzz_repo_manager.git(['checkout', 'projects'])
    oss_fuzz_repo_manager.git(['clean', '-fxd', 'projects'])


if __name__ == '__main__':
  main()