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diff --git a/src/rocksdb/fuzz/README.md b/src/rocksdb/fuzz/README.md new file mode 100644 index 000000000..238b283a2 --- /dev/null +++ b/src/rocksdb/fuzz/README.md @@ -0,0 +1,165 @@ +# Fuzzing RocksDB + +## Overview + +This directory contains [fuzz tests](https://en.wikipedia.org/wiki/Fuzzing) for RocksDB. +RocksDB testing infrastructure currently includes unit tests and [stress tests](https://github.com/facebook/rocksdb/wiki/Stress-test), +we hope fuzz testing can catch more bugs. + +## Prerequisite + +We use [LLVM libFuzzer](http://llvm.org/docs/LibFuzzer.html) as the fuzzying engine, +so make sure you have [clang](https://clang.llvm.org/get_started.html) as your compiler. + +Some tests rely on [structure aware fuzzing](https://github.com/google/fuzzing/blob/master/docs/structure-aware-fuzzing.md). +We use [protobuf](https://developers.google.com/protocol-buffers) to define structured input to the fuzzer, +and use [libprotobuf-mutator](https://github.com/google/libprotobuf-mutator) as the custom libFuzzer mutator. +So make sure you have protobuf and libprotobuf-mutator installed, and make sure `pkg-config` can find them. +On some systems, there are both protobuf2 and protobuf3 in the package management system, +make sure protobuf3 is installed. + +If you do not want to install protobuf library yourself, you can rely on libprotobuf-mutator to download protobuf +for you. For details about installation, please refer to [libprotobuf-mutator README](https://github.com/google/libprotobuf-mutator#readme) + +## Example + +This example shows you how to do structure aware fuzzing to `rocksdb::SstFileWriter`. + +After walking through the steps to create the fuzzer, we'll introduce a bug into `rocksdb::SstFileWriter::Put`, +then show that the fuzzer can catch the bug. + +### Design the test + +We want the fuzzing engine to automatically generate a list of database operations, +then we apply these operations to `SstFileWriter` in sequence, +finally, after the SST file is generated, we use `SstFileReader` to check the file's checksum. + +### Define input + +We define the database operations in protobuf, each operation has a type of operation and a key value pair, +see [proto/db_operation.proto](proto/db_operation.proto) for details. + +### Define tests with the input + +In [sst_file_writer_fuzzer.cc](sst_file_writer_fuzzer.cc), +we define the tests to be run on the generated input: + +``` +DEFINE_PROTO_FUZZER(DBOperations& input) { + // apply the operations to SstFileWriter and use SstFileReader to verify checksum. + // ... +} +``` + +`SstFileWriter` requires the keys of the operations to be unique and be in ascending order, +but the fuzzing engine generates the input randomly, so we need to process the generated input before +passing it to `DEFINE_PROTO_FUZZER`, this is accomplished by registering a post processor: + +``` +protobuf_mutator::libfuzzer::PostProcessorRegistration<DBOperations> +``` + +### Compile and link the fuzzer + +In the rocksdb root directory, compile rocksdb library by `make static_lib`. + +Go to the `fuzz` directory, +run `make sst_file_writer_fuzzer` to generate the fuzzer, +it will compile rocksdb static library, generate protobuf, then compile and link `sst_file_writer_fuzzer`. + +### Introduce a bug + +Manually introduce a bug to `SstFileWriter::Put`: + +``` +diff --git a/table/sst_file_writer.cc b/table/sst_file_writer.cc +index ab1ee7c4e..c7da9ffa0 100644 +--- a/table/sst_file_writer.cc ++++ b/table/sst_file_writer.cc +@@ -277,6 +277,11 @@ Status SstFileWriter::Add(const Slice& user_key, const Slice& value) { + } + + Status SstFileWriter::Put(const Slice& user_key, const Slice& value) { ++ if (user_key.starts_with("!")) { ++ if (value.ends_with("!")) { ++ return Status::Corruption("bomb"); ++ } ++ } + return rep_->Add(user_key, value, ValueType::kTypeValue); + } +``` + +The bug is that for `Put`, if `user_key` starts with `!` and `value` ends with `!`, then corrupt. + +### Run fuzz testing to catch the bug + +Run the fuzzer by `time ./sst_file_writer_fuzzer`. + +Here is the output on my machine: + +``` +Corruption: bomb +==59680== ERROR: libFuzzer: deadly signal + #0 0x109487315 in __sanitizer_print_stack_trace+0x35 (libclang_rt.asan_osx_dynamic.dylib:x86_64+0x4d315) + #1 0x108d63f18 in fuzzer::PrintStackTrace() FuzzerUtil.cpp:205 + #2 0x108d47613 in fuzzer::Fuzzer::CrashCallback() FuzzerLoop.cpp:232 + #3 0x7fff6af535fc in _sigtramp+0x1c (libsystem_platform.dylib:x86_64+0x35fc) + #4 0x7ffee720f3ef (<unknown module>) + #5 0x7fff6ae29807 in abort+0x77 (libsystem_c.dylib:x86_64+0x7f807) + #6 0x108cf1c4c in TestOneProtoInput(DBOperations&)+0x113c (sst_file_writer_fuzzer:x86_64+0x100302c4c) + #7 0x108cf09be in LLVMFuzzerTestOneInput+0x16e (sst_file_writer_fuzzer:x86_64+0x1003019be) + #8 0x108d48ce0 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) FuzzerLoop.cpp:556 + #9 0x108d48425 in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) FuzzerLoop.cpp:470 + #10 0x108d4a626 in fuzzer::Fuzzer::MutateAndTestOne() FuzzerLoop.cpp:698 + #11 0x108d4b325 in fuzzer::Fuzzer::Loop(std::__1::vector<fuzzer::SizedFile, fuzzer::fuzzer_allocator<fuzzer::SizedFile> >&) FuzzerLoop.cpp:830 + #12 0x108d37fcd in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) FuzzerDriver.cpp:829 + #13 0x108d652b2 in main FuzzerMain.cpp:19 + #14 0x7fff6ad5acc8 in start+0x0 (libdyld.dylib:x86_64+0x1acc8) + +NOTE: libFuzzer has rudimentary signal handlers. + Combine libFuzzer with AddressSanitizer or similar for better crash reports. +SUMMARY: libFuzzer: deadly signal +MS: 7 Custom-CustomCrossOver-InsertByte-Custom-ChangeBit-Custom-CustomCrossOver-; base unit: 90863b4d83c3f994bba0a417d0c2ee3b68f9e795 +0x6f,0x70,0x65,0x72,0x61,0x74,0x69,0x6f,0x6e,0x73,0x20,0x7b,0xa,0x20,0x20,0x6b,0x65,0x79,0x3a,0x20,0x22,0x21,0x22,0xa,0x20,0x20,0x76,0x61,0x6c,0x75,0x65,0x3a,0x20,0x22,0x21,0x22,0xa,0x20,0x20,0x74,0x79,0x70,0x65,0x3a,0x20,0x50,0x55,0x54,0xa,0x7d,0xa,0x6f,0x70,0x65,0x72,0x61,0x74,0x69,0x6f,0x6e,0x73,0x20,0x7b,0xa,0x20,0x20,0x6b,0x65,0x79,0x3a,0x20,0x22,0x2b,0x22,0xa,0x20,0x20,0x74,0x79,0x70,0x65,0x3a,0x20,0x50,0x55,0x54,0xa,0x7d,0xa,0x6f,0x70,0x65,0x72,0x61,0x74,0x69,0x6f,0x6e,0x73,0x20,0x7b,0xa,0x20,0x20,0x6b,0x65,0x79,0x3a,0x20,0x22,0x2e,0x22,0xa,0x20,0x20,0x74,0x79,0x70,0x65,0x3a,0x20,0x50,0x55,0x54,0xa,0x7d,0xa,0x6f,0x70,0x65,0x72,0x61,0x74,0x69,0x6f,0x6e,0x73,0x20,0x7b,0xa,0x20,0x20,0x6b,0x65,0x79,0x3a,0x20,0x22,0x5c,0x32,0x35,0x33,0x22,0xa,0x20,0x20,0x74,0x79,0x70,0x65,0x3a,0x20,0x50,0x55,0x54,0xa,0x7d,0xa, +operations {\x0a key: \"!\"\x0a value: \"!\"\x0a type: PUT\x0a}\x0aoperations {\x0a key: \"+\"\x0a type: PUT\x0a}\x0aoperations {\x0a key: \".\"\x0a type: PUT\x0a}\x0aoperations {\x0a key: \"\\253\"\x0a type: PUT\x0a}\x0a +artifact_prefix='./'; Test unit written to ./crash-a1460be302d09b548e61787178d9edaa40aea467 +Base64: b3BlcmF0aW9ucyB7CiAga2V5OiAiISIKICB2YWx1ZTogIiEiCiAgdHlwZTogUFVUCn0Kb3BlcmF0aW9ucyB7CiAga2V5OiAiKyIKICB0eXBlOiBQVVQKfQpvcGVyYXRpb25zIHsKICBrZXk6ICIuIgogIHR5cGU6IFBVVAp9Cm9wZXJhdGlvbnMgewogIGtleTogIlwyNTMiCiAgdHlwZTogUFVUCn0K +./sst_file_writer_fuzzer 5.97s user 4.40s system 64% cpu 16.195 total +``` + +Within 6 seconds, it catches the bug. + +The input that triggers the bug is persisted in `./crash-a1460be302d09b548e61787178d9edaa40aea467`: + +``` +$ cat ./crash-a1460be302d09b548e61787178d9edaa40aea467 +operations { + key: "!" + value: "!" + type: PUT +} +operations { + key: "+" + type: PUT +} +operations { + key: "." + type: PUT +} +operations { + key: "\253" + type: PUT +} +``` + +### Reproduce the crash to debug + +The above crash can be reproduced by `./sst_file_writer_fuzzer ./crash-a1460be302d09b548e61787178d9edaa40aea467`, +so you can debug the crash. + +## Future Work + +According to [OSS-Fuzz](https://github.com/google/oss-fuzz), +`as of June 2020, OSS-Fuzz has found over 20,000 bugs in 300 open source projects.` + +RocksDB can join OSS-Fuzz together with other open source projects such as sqlite. |