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# AFL quick start guide
You should read [README.md](README.md) - it's pretty short. If you really can't, here's
how to hit the ground running:
1) Compile AFL with 'make'. If build fails, see [INSTALL.md](INSTALL.md) for tips.
2) Find or write a reasonably fast and simple program that takes data from
a file or stdin, processes it in a test-worthy way, then exits cleanly.
If testing a network service, modify it to run in the foreground and read
from stdin. When fuzzing a format that uses checksums, comment out the
checksum verification code, too.
If this is not possible (e.g. in -Q(emu) mode) then use
AFL_CUSTOM_MUTATOR_LIBRARY to calculate the values with your own library.
The program must crash properly when a fault is encountered. Watch out for
custom SIGSEGV or SIGABRT handlers and background processes. For tips on
detecting non-crashing flaws, see section 11 in [README.md](README.md) .
3) Compile the program / library to be fuzzed using afl-gcc. A common way to
do this would be:
CC=/path/to/afl-gcc CXX=/path/to/afl-g++ ./configure --disable-shared
make clean all
If program build fails, ping <afl-users@googlegroups.com>.
4) Get a small but valid input file that makes sense to the program. When
fuzzing verbose syntax (SQL, HTTP, etc), create a dictionary as described in
dictionaries/README.md, too.
5) If the program reads from stdin, run 'afl-fuzz' like so:
./afl-fuzz -i testcase_dir -o findings_dir -- \
/path/to/tested/program [...program's cmdline...]
If the program takes input from a file, you can put @@ in the program's
command line; AFL will put an auto-generated file name in there for you.
6) Investigate anything shown in red in the fuzzer UI by promptly consulting
[status_screen.md](status_screen.md).
7) compile and use llvm_mode (afl-clang-fast/afl-clang-fast++) as it is way
faster and has a few cool features
8) There is a basic docker build with 'docker build -t aflplusplus .'
That's it. Sit back, relax, and - time permitting - try to skim through the
following files:
- README.md - A general introduction to AFL,
- docs/perf_tips.md - Simple tips on how to fuzz more quickly,
- docs/status_screen.md - An explanation of the tidbits shown in the UI,
- docs/parallel_fuzzing.md - Advice on running AFL on multiple cores.
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