92 lines
2.8 KiB
ReStructuredText
92 lines
2.8 KiB
ReStructuredText
Fuzzing The Library
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============================
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Botan comes with a set of fuzzing endpoints which can be used to test
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the library.
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.. highlight:: shell
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Fuzzing with libFuzzer
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------------------------
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To fuzz with libFuzzer (https://llvm.org/docs/LibFuzzer.html), you'll first
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need to compile libFuzzer::
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$ svn co https://llvm.org/svn/llvm-project/compiler-rt/trunk/lib/fuzzer libFuzzer
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$ cd libFuzzer && clang -c -g -O2 -std=c++11 *.cpp
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$ ar cr libFuzzer.a libFuzzer/*.o
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Then build the fuzzers::
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$ ./configure.py --cc=clang --build-fuzzer=libfuzzer --unsafe-fuzzer-mode \
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--with-debug-info --enable-sanitizers=coverage,address,undefined
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$ make fuzzers
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Enabling 'coverage' sanitizer flags is required for libFuzzer to work.
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Address sanitizer and undefined sanitizer are optional.
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The fuzzer binaries will be in `build/fuzzer`. Simply pick one and run it, optionally
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also passing a directory containing corpus inputs.
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Using `libfuzzer` build mode implicitly assumes the fuzzers need to
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link with `libFuzzer`; if another library is needed (for example in
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OSS-Fuzz, which uses `libFuzzingEngine`), use the flag
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`--with-fuzzer-lib` to specify the desired name.
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Fuzzing with AFL
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--------------------
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To fuzz with AFL (http://lcamtuf.coredump.cx/afl/)::
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$ ./configure.py --with-sanitizers --build-fuzzer=afl --unsafe-fuzzer-mode --cc-bin=afl-g++
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$ make fuzzers
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For AFL sanitizers are optional. You can also use `afl-clang-fast++`
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or `afl-clang++`, be sure to set `--cc=clang` also.
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The fuzzer binaries will be in `build/fuzzer`. To run them you need to
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run under `afl-fuzz`::
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$ afl-fuzz -i corpus_path -o output_path ./build/fuzzer/binary
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Fuzzing with TLS-Attacker
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--------------------------
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TLS-Attacker (https://github.com/RUB-NDS/TLS-Attacker) includes a mode for fuzzing
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TLS servers. A prebuilt copy of TLS-Attacker is available in a git repository::
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$ git clone --depth 1 https://github.com/randombit/botan-ci-tools.git
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To run it against Botan's server::
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$ ./configure.py --with-sanitizers
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$ make botan
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$ ./src/scripts/run_tls_attacker.py ./botan ./botan-ci-tools
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Output and logs from the fuzzer are placed into `/tmp`. See the
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TLS-Attacker documentation for more information about how to use this
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tool.
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Input Corpus
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-----------------------
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AFL requires an input corpus, and libFuzzer can certainly make good
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use of it.
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Some crypto corpus repositories include
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* https://github.com/randombit/crypto-corpus
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* https://github.com/mozilla/nss-fuzzing-corpus
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* https://github.com/google/boringssl/tree/master/fuzz
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* https://github.com/openssl/openssl/tree/master/fuzz/corpora
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Adding new fuzzers
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---------------------
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New fuzzers are created by adding a source file to `src/fuzzers` which
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have the signature:
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``void fuzz(const uint8_t in[], size_t len)``
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After adding your fuzzer, rerun ``./configure.py`` and build.
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