Introduction

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

A few actuall 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. Output of the parser before fuzzing can be found in input_packets.txt

Installing AFL

To run the test yourself, you need to dounload 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 insall 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 llvm libbsd-dev
  

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"

Running the test

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

After going through all of the requirements above, you can cd into this test's folder and simply run make fuzz.