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1# Copyright 2021 Google LLC
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7#      http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14"""Module for dealing with fuzz targets affected by the change-under-test
15(CUT)."""
16import logging
17import os
18import sys
19
20# pylint: disable=wrong-import-position,import-error
21sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
22import utils
23
24
25def remove_unaffected_fuzz_targets(clusterfuzz_deployment, out_dir,
26                                   files_changed, repo_path):
27  """Removes all non affected fuzz targets in the out directory.
28
29  Args:
30    clusterfuzz_deployment: The ClusterFuzz deployment object.
31    out_dir: The location of the fuzz target binaries.
32    files_changed: A list of files changed compared to HEAD.
33    repo_path: The location of the OSS-Fuzz repo in the docker image.
34
35  This function will not delete fuzz targets unless it knows that the fuzz
36  targets are unaffected. For example, this means that fuzz targets which don't
37  have coverage data on will not be deleted.
38  """
39  if not files_changed:
40    # Don't remove any fuzz targets if there is no difference from HEAD.
41    logging.info('No files changed compared to HEAD.')
42    return
43
44  logging.info('Files changed in PR: %s', files_changed)
45
46  fuzz_target_paths = utils.get_fuzz_targets(out_dir)
47  if not fuzz_target_paths:
48    # Nothing to remove.
49    logging.error('No fuzz targets found in out dir.')
50    return
51
52  coverage = clusterfuzz_deployment.get_coverage(repo_path)
53  if not coverage:
54    # Don't remove any fuzz targets unless we have data.
55    logging.error('Could not find latest coverage report.')
56    return
57
58  affected_fuzz_targets = get_affected_fuzz_targets(coverage, fuzz_target_paths,
59                                                    files_changed)
60
61  if not affected_fuzz_targets:
62    logging.info('No affected fuzz targets detected, keeping all as fallback.')
63    return
64
65  logging.info('Using affected fuzz targets: %s.', affected_fuzz_targets)
66  unaffected_fuzz_targets = set(fuzz_target_paths) - affected_fuzz_targets
67  logging.info('Removing unaffected fuzz targets: %s.', unaffected_fuzz_targets)
68
69  # Remove all the targets that are not affected.
70  for fuzz_target_path in unaffected_fuzz_targets:
71    try:
72      os.remove(fuzz_target_path)
73    except OSError as error:
74      logging.error('%s occurred while removing file %s', error,
75                    fuzz_target_path)
76
77
78def is_fuzz_target_affected(coverage, fuzz_target_path, files_changed):
79  """Returns True if a fuzz target (|fuzz_target_path|) is affected by
80  |files_changed|."""
81  fuzz_target = os.path.basename(fuzz_target_path)
82  covered_files = coverage.get_files_covered_by_target(fuzz_target)
83  if not covered_files:
84    # Assume a fuzz target is affected if we can't get its coverage from
85    # OSS-Fuzz.
86    # TODO(metzman): Figure out what we should do if covered_files is [].
87    # Should we act as if we couldn't get the coverage?
88    logging.info('Could not get coverage for %s. Treating as affected.',
89                 fuzz_target)
90    return True
91
92  logging.info('Fuzz target %s is affected by: %s', fuzz_target, covered_files)
93  for filename in files_changed:
94    if filename in covered_files:
95      logging.info('Fuzz target %s is affected by changed file: %s',
96                   fuzz_target, filename)
97      return True
98
99  logging.info('Fuzz target %s is not affected.', fuzz_target)
100  return False
101
102
103def get_affected_fuzz_targets(coverage, fuzz_target_paths, files_changed):
104  """Returns a list of paths of affected targets."""
105  affected_fuzz_targets = set()
106  for fuzz_target_path in fuzz_target_paths:
107    if is_fuzz_target_affected(coverage, fuzz_target_path, files_changed):
108      affected_fuzz_targets.add(fuzz_target_path)
109
110  return affected_fuzz_targets
111