# I Can Haz Fuzz? LibFuzzer ========= Or, how to fuzz OpenSSL with [libfuzzer](llvm.org/docs/LibFuzzer.html). Starting from a vanilla+OpenSSH server Ubuntu install. Use Chrome's handy recent build of clang. Older versions may also work. $ sudo apt-get install git $ mkdir git-work $ git clone https://chromium.googlesource.com/chromium/src/tools/clang $ clang/scripts/update.py You may want to git pull and re-run the update from time to time. Update your path: $ PATH=~/third_party/llvm-build/Release+Asserts/bin/:$PATH Get and build libFuzzer (there is a git mirror at https://github.com/llvm-mirror/llvm/tree/master/lib/Fuzzer if you prefer): $ cd $ sudo apt-get install subversion $ mkdir svn-work $ cd svn-work $ svn co http://llvm.org/svn/llvm-project/llvm/trunk/lib/Fuzzer $ cd Fuzzer $ clang++ -c -g -O2 -std=c++11 *.cpp $ ar r libFuzzer.a *.o $ ranlib libFuzzer.a Configure for fuzzing: $ CC=clang ./config enable-fuzz-libfuzzer \ --with-fuzzer-include=../../svn-work/Fuzzer \ --with-fuzzer-lib=../../svn-work/Fuzzer/libFuzzer \ -DPEDANTIC enable-asan enable-ubsan no-shared $ sudo apt-get install make $ LDCMD=clang++ make -j $ fuzz/helper.py $FUZZER Where $FUZZER is one of the executables in `fuzz/`. If you get a crash, you should find a corresponding input file in `fuzz/corpora/$FUZZER-crash/`. You can reproduce the crash with $ fuzz/$FUZZER AFL === Configure for fuzzing: $ sudo apt-get install afl-clang $ CC=afl-clang-fast ./config enable-fuzz-afl no-shared $ make Run one of the fuzzers: $ afl-fuzz -i fuzz/corpora/$FUZZER -o fuzz/corpora/$FUZZER/out fuzz/$FUZZER Where $FUZZER is one of the executables in `fuzz/`.