70 lines
2 KiB
Markdown
70 lines
2 KiB
Markdown
# I Can Haz Fuzz?
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LibFuzzer
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=========
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Or, how to fuzz OpenSSL with [libfuzzer](llvm.org/docs/LibFuzzer.html).
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Starting from a vanilla+OpenSSH server Ubuntu install.
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Use Chrome's handy recent build of clang. Older versions may also work.
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$ sudo apt-get install git
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$ mkdir git-work
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$ git clone https://chromium.googlesource.com/chromium/src/tools/clang
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$ clang/scripts/update.py
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You may want to git pull and re-run the update from time to time.
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Update your path:
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$ PATH=~/third_party/llvm-build/Release+Asserts/bin/:$PATH
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Get and build libFuzzer (there is a git mirror at
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https://github.com/llvm-mirror/llvm/tree/master/lib/Fuzzer if you prefer):
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$ cd
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$ sudo apt-get install subversion
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$ mkdir svn-work
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$ cd svn-work
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$ svn co http://llvm.org/svn/llvm-project/llvm/trunk/lib/Fuzzer
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$ cd Fuzzer
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$ clang++ -c -g -O2 -std=c++11 *.cpp
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$ ar r libFuzzer.a *.o
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$ ranlib libFuzzer.a
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Configure for fuzzing:
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$ CC=clang ./config enable-fuzz-libfuzzer \
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--with-fuzzer-include=../../svn-work/Fuzzer \
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--with-fuzzer-lib=../../svn-work/Fuzzer/libFuzzer \
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enable-asan enable-ubsan no-shared
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$ sudo apt-get install make
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$ LDCMD=clang++ make -j
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$ fuzz/helper.py <fuzzer> <arguments>
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Where `<fuzzer>` is one of the executables in `fuzz/`. Most fuzzers do not
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need any command line arguments, but, for example, `asn1` needs the name of a
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data type.
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If you get a crash, you should find a corresponding input file in
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`fuzz/corpora/<fuzzer>-crash/`. You can reproduce the crash with
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$ fuzz/<fuzzer> <crashfile>
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AFL
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===
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Configure for fuzzing:
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$ sudo apt-get install afl-clang
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$ CC=afl-clang-fast ./config enable-fuzz-afl no-shared
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$ make
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Run one of the fuzzers:
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$ afl-fuzz fuzz/<fuzzer> -i fuzz/corpora/<fuzzer> -o fuzz/corpora/<fuzzer>/out <fuzzer> <arguments>
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Where `<fuzzer>` is one of the executables in `fuzz/`. Most fuzzers do not
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need any command line arguments, but, for example, `asn1` needs the name of a
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data type.
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