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#!/usr/bin/env python3
# Copyright 2020 Google Inc.
#
# 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.
#
################################################################################
"""Script for collecting dataflow traces using DFSan compiled binary. The script
imitates `CollectDataFlow` function from libFuzzer but provides some flexibility
for skipping long and/or slow corpus elements.
Follow https://github.com/google/oss-fuzz/issues/1632 for more details."""
import hashlib
import os
import subprocess
import sys
# pylint: skip-file
# See https://github.com/google/oss-fuzz/pull/5024#discussion_r561313003 for why
# we are disabling pylint for this file (we can't do it in .pylintrc, probably
# because of weirdness with this file's package, so we do it here).
# These can be controlled by the runner in order to change the values without
# rebuilding OSS-Fuzz base images.
FILE_SIZE_LIMIT = int(os.getenv('DFT_FILE_SIZE_LIMIT', 32 * 1024))
MIN_TIMEOUT = float(os.getenv('DFT_MIN_TIMEOUT', 1.0))
TIMEOUT_RANGE = float(os.getenv('DFT_TIMEOUT_RANGE', 3.0))
DFSAN_OPTIONS = 'fast16labels=1:warn_unimplemented=0'
def _error(msg):
sys.stderr.write(msg + '\n')
def _list_dir(dirpath):
for root, _, files in os.walk(dirpath):
for f in files:
yield os.path.join(root, f)
def _sha1(filepath):
h = hashlib.sha1()
with open(filepath, 'rb') as f:
h.update(f.read())
return h.hexdigest()
def _run(cmd, timeout=None):
result = None
try:
result = subprocess.run(cmd,
timeout=timeout,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
if result.returncode:
_error('{command} finished with non-zero code: {code}'.format(
command=str(cmd), code=result.returncode))
except subprocess.TimeoutExpired:
raise
except Exception as e:
_error('Exception: ' + str(e))
return result
def _timeout(size):
# Dynamic timeout value (proportional to file size) to discard slow units.
timeout = MIN_TIMEOUT
timeout += size * TIMEOUT_RANGE / FILE_SIZE_LIMIT
return timeout
def collect_traces(binary, corpus_dir, dft_dir):
stats = {
'total': 0,
'traced': 0,
'long': 0,
'slow': 0,
'failed': 0,
}
files_and_sizes = {}
for f in _list_dir(corpus_dir):
stats['total'] += 1
size = os.path.getsize(f)
if size > FILE_SIZE_LIMIT:
stats['long'] += 1
print('Skipping large file ({size}b): {path}'.format(size=size, path=f))
continue
files_and_sizes[f] = size
for f in sorted(files_and_sizes, key=files_and_sizes.get):
output_path = os.path.join(dft_dir, _sha1(f))
try:
result = _run([binary, f, output_path], timeout=_timeout(size))
if result.returncode:
stats['failed'] += 1
else:
stats['traced'] += 1
except subprocess.TimeoutExpired as e:
_error('Slow input: ' + str(e))
stats['slow'] += 1
return stats
def dump_functions(binary, dft_dir):
result = _run([binary])
if not result or result.returncode:
return False
with open(os.path.join(dft_dir, 'functions.txt'), 'wb') as f:
f.write(result.stdout)
return True
def main():
if len(sys.argv) < 4:
_error('Usage: {0} <binary> <corpus_dir> <dft_dir>'.format(sys.argv[0]))
sys.exit(1)
binary = sys.argv[1]
corpus_dir = sys.argv[2]
dft_dir = sys.argv[3]
os.environ['DFSAN_OPTIONS'] = DFSAN_OPTIONS
if not dump_functions(binary, dft_dir):
_error('Failed to dump functions. Something is wrong.')
sys.exit(1)
stats = collect_traces(binary, corpus_dir, dft_dir)
for k, v in stats.items():
print('{0}: {1}'.format(k, v))
# Checksum that we didn't lose track of any of the inputs.
assert stats['total'] * 2 == sum(v for v in stats.values())
sys.exit(0)
if __name__ == "__main__":
main()
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