Fixing urllib3 port binding crash #9958
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DavidKorczynski
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Apr 5, 2023
We've still got an issue with crashes on the urllib3 requests test that uses the mock HTTP server. Fix #9958 to handle port mapping errors didn't resolve it. I got a feeling there's an ordering issue. Looking at the error logs [https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=56500#c2](https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=56500#c2) there appears to be an issue where we're throwing exceptions before the coverage completes. ``` === Uncaught Python exception: === -- | MaxRetryError: HTTPConnectionPool(host='localhost', port=8011): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f4cdf33d1f0>: Failed to establish a new connection: [Errno 101] Network is unreachable')) | Traceback (most recent call last): | File "fuzz_requests.py", line 109, in TestOneInput | File "urllib3/_request_methods.py", line 118, in request | File "urllib3/_request_methods.py", line 217, in request_encode_body | File "urllib3/poolmanager.py", line 433, in urlopen | File "urllib3/connectionpool.py", line 874, in urlopen | File "urllib3/connectionpool.py", line 874, in urlopen | File "urllib3/connectionpool.py", line 874, in urlopen | File "urllib3/connectionpool.py", line 844, in urlopen | File "urllib3/util/retry.py", line 505, in increment | MaxRetryError: HTTPConnectionPool(host='localhost', port=8011): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7f4cdf33d1f0>: Failed to establish a new connection: [Errno 101] Network is unreachable')) | | INFO: Instrumenting 3854 functions... | INFO: Instrumentation complete. | ==10674== ERROR: libFuzzer: fuzz target exited | #0 0x7f4ce0bac694 in __sanitizer_print_stack_trace /src/llvm-project/compiler-rt/lib/ubsan/ubsan_diag_standalone.cpp:31:3 | #1 0x7f4ce0b2df48 in fuzzer::PrintStackTrace() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerUtil.cpp:210:5 | #2 0x7f4ce0b12cdc in fuzzer::Fuzzer::ExitCallback() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:250:3 | #3 0x7f4ce09068a6 in __run_exit_handlers /build/glibc-SzIz7B/glibc-2.31/stdlib/exit.c:108:8 | #4 0x7f4ce0906a5f in exit /build/glibc-SzIz7B/glibc-2.31/stdlib/exit.c:139:3 | #5 0x7f4ce03b2c78 in libpython3.8.so.1.0 | #6 0x7f4ce03b76cf in libpython3.8.so.1.0 | #7 0x403ad2 in fuzz_requests.pkg | #8 0x403e67 in fuzz_requests.pkg | #9 0x7f4ce08e4082 in __libc_start_main /build/glibc-SzIz7B/glibc-2.31/csu/libc-start.c:308:16 | #10 0x40249d in fuzz_requests.pkg | | SUMMARY: libFuzzer: fuzz target exited ``` This is an attempted fix inspired by the requests [fuzz_server.py](https://github.com/google/oss-fuzz/blob/master/projects/requests/fuzz_server.py) where the lifecycle of the test thread is managed within the server. Since the web server is created at the start of `TestOneInput` I don't expect there to be any timing issues or thread initialisation issues.
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I've managed to recreate the issue that was stopping the
fuzz_requestscoverage onurllib3( see #9863 )The issues not visible running introspector locally but can be see in clusterfuzzlite which is a port binding error. This change randomises the port that's used and ensures that it can bind to it before fuzzing starts. Change is tested and demonstrated as working here sg3-141-592/urllib3 - ClusterFuzzLite PR fuzzing.
Also I've changed the style of the main block and atheris to be consistent with the other fuzzers added lately.