esp-idf/components/mdns/test_afl_fuzz_host

Introduction

This test uses american fuzzy lop to mangle real mdns packets and look for exceptions caused by the parser.

A few actual packets are collected and exported as bins in the in folder, which is then passed as input to AFL when testing. The setup procedure for the test includes all possible services and scenarios that could be used with the given input packets.The output of the parser before fuzzing can be found in input_packets.txt

Building and running the tests using AFL

To build and run the tests using AFL(afl-clang-fast) instrumentation

cd $IDF_PATH/components/mdns/test_afl_host
make fuzz

(Please note you have to install AFL instrumentation first, check Installing AFL section)

Building the tests using GCC INSTR(off)

To build the tests without AFL instrumentations and instead of that use GCC compiler(In this case it will only check for compilation issues and will not run AFL tests).

cd $IDF_PATH/components/mdns/test_afl_host
make INSTR=off

Note, that this setup is useful if we want to reproduce issues reported by fuzzer tests executed in the CI, or to simulate how the packet parser treats the input packets on the host machine.

Installing AFL

To run the test yourself, you need to download the latest afl archive and extract it to a folder on your computer.

The rest of the document will refer to that folder as PATH_TO_AFL.

Preparation

• On Mac, you will need to install the latest Xcode and llvm support from Homebrew

  /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
  brew install --with-clang --with-lld --HEAD llvm
  export PATH="/usr/local/opt/llvm/bin:$PATH"
  

• On Ubuntu you need the following packages:

  sudo apt-get install make clang-4.0(or <=4.0) llvm-4.0(or <=4.0) libbsd-dev
  

Please note that if specified package version can't be installed(due to system is the latest), you can download, build and install it manually.

Compile AFL

Compiling AFL is as easy as running make:

cd [PATH_TO_AFL]
make
cd llvm_mode/
make

After successful compilation, you can export the following variables to your shell (you can also add them to your profile if you want to use AFL in other projects).

export AFL_PATH=[PATH_TO_AFL]
export PATH="$AFL_PATH:$PATH"

Please note LLVM must be <=4.0.0, otherwise afl does not compile, as there are some limitations with building AFL on MacOS/Linux with the latest LLVM. Also, Windows build on cygwin is not fully supported.

Additional info

Apple has a crash reporting service that could interfere with AFLs normal operation. To turn that off, run the following command:

launchctl unload -w /System/Library/LaunchAgents/com.apple.ReportCrash.plist
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.ReportCrash.Root.plist

Ubuntu has a similar service. To turn that off, run as root:

echo core >/proc/sys/kernel/core_pattern