XNU Fuzz 2

Introduction

This program was originally going to be based off of the original xnufuzz, however that idea was scrapped due to the fact that the original xnufuzz was so bare bones, there would be nothing left to keep. Also, having JSON parsing would be extremely helpful, so in the end a full rewrite was written. The goal of this is to create a fuzzer that is capable of thoroughly fuzzing XNU syscalls using both completely randomly generated arguments, and also mutated arguments from syscalls collected the dtrace.

Prerequisites & Notices

As with any kernel fuzzing software, this can and will result in the loss of data, and it's even possible that this can impact the local network. As of right now, no protections are made to prevent this from shooting out network packets to random places in the internet, so please be conscious of these risks while running this software. raw/syscalls.master is a listing of syscalls from bsd/kern/syscalls.master in the XNU source, and it can be regenerated using ./tools/syscallparser.py.

Setup

In order to completely download and compile the software you can run the following commands

git clone https://github.com/block8437/xnufuzz2.git
cd xnufuzz2
make

To generate a new raw/syscall_logs.txt, run sudo dtruss -p ANYPID 2>> raw/syscall_logs.txt. ANYPID should be substituted for any PID you would like to read the syscalls from. In my experience, running it with finder yields quite a bit of good results. Afterwards, run ./tools/syslogparser.py to generate data/examples.json.

Running

$ ./xnufuzz2 --help
usage: ./xnufuzz2 [options] ...
options:
  -c, --count       amount of syscalls to generate (int [=0])
  -s, --specific    specific syscall to fuzz (int [=-1])
  -p, --syscalls    path to syscalls (string [=data/syscalls.json])
  -e, --examples    path to examples (string [=data/examples.json])
  -d, --dry         dry run or not (bool [=0])
  -?, --help        print this message

Credits

• Brian Smith: Creation of this project & all fuzzing & syscall related code
• Apple/FreeBSD/CMU: Creation of XNU
• github.com/bringhurst: Creation of xnufuzz - this inspiration for this project
• github.com/tanakh: Creation of cmdline.h (in this project named )
• github.com/nlohmann: Creation of json.hpp