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93 lines
3.4 KiB
93 lines
3.4 KiB
4 months ago
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#!/usr/bin/python3
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# Copyright 2020 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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""" An example native JSON vs uJSON differential fuzzer.
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This fuzzer looks for differences between the built-in json library and the
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native ujson library. The ujson library should be built for coverage (see
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build_install_ujson.sh), and the Python fuzzer should be executed under ASAN.
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As an example:
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LD_PRELOAD="/usr/lib/llvm-9/lib/clang/9.0.1/lib/linux/libclang_rt.asan-x86_64.so
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$(python3 -c "import atheris; print(atheris.path())")" python3
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./json_differential_fuzzer.py -detect_leaks=0
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This fuzzer has found a bug with inconsistent handling of integers with
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too-high magnitude. uJSON sometimes refuses to process numbers that are too far
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from 0 with "Value is too big!" or the equivalent for values that are too
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negative. However, other times it happily processes them with two's compliment
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mod. As an example, it refuses to parse "-9223372036854775809" (the first
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integer not representable in a 64-bit signed number) with "Value is too small";
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but it will happily parse "-80888888888888888888", a significantly more negative
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number. However, it parses it as -9223372036854775808. The JSON spec
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(https://tools.ietf.org/html/rfc7159#section-6) "allows implementations to set
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limits on the range and precision of numbers accepted", so failing to parse
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values that are too big or too small is techincally fine; however,
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misinterpreting them is not.
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"""
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import atheris_no_libfuzzer as atheris
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import json
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import ujson
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import sys
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def ClearAllIntegers(data):
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"""Used to prevent known bug; sets all integers in data recursively to 0."""
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if type(data) == int:
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return 0
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if type(data) == list:
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for i in range(0, len(data)):
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data[i] = ClearAllIntegers(data[i])
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if type(data) == dict:
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for k, v in data:
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data[k] = ClearAllIntegers(v)
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return data
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def TestOneInput(input_bytes):
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fdp = atheris.FuzzedDataProvider(input_bytes)
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original = fdp.ConsumeUnicode(sys.maxsize)
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try:
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ujson_data = ujson.loads(original)
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json_data = json.loads(original)
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except Exception as e:
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# It would be interesting to enforce that if one of the libraries throws an
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# exception, the other does too. However, uJSON accepts many invalid inputs
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# that are uninteresting, such as "00". So, that is not done.
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return
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# Uncomment these lines to ignore the errors described in the docstring of
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# this file.
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# json_data = ClearAllIntegers(json_data)
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# ujson_data = ClearAllIntegers(ujson_data)
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json_dumped = json.dumps(json_data)
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ujson_dumped = json.dumps(ujson_data)
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if json_dumped != ujson_dumped:
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raise RuntimeError(
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"Decoding/encoding disagreement!\nInput: %s\nJSON data: %s\nuJSON data: %s\nJSON-dumped: %s\nuJSON-dumped: %s\n"
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% (original, json_data, ujson_data, json_dumped, ujson_dumped))
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def main():
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atheris.Setup(sys.argv, TestOneInput)
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atheris.Fuzz()
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if __name__ == "__main__":
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main()
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