QSYM: A Practical Concolic Execution Engine Tailored for Hybrid Fuzzing

Environment

Tested on Ubuntu 14.04 64bit and 16.04 64bit

Installation

# disable ptrace_scope for PIN
$ echo 0|sudo tee /proc/sys/kernel/yama/ptrace_scope

# install z3 and system deps
$ ./setup.sh

# install using virtual env
$ virtualenv venv
$ source venv/bin/activate
$ pip install .

Installation using Docker

# disable ptrace_scope for PIN
$ echo 0|sudo tee /proc/sys/kernel/yama/ptrace_scope

# build docker image
$ docker build -t qsym ./

# run docker image
$ docker run --cap-add=SYS_PTRACE -it qsym /bin/bash

Installation using vagrant

Since QSYM is dependent on underlying kernel because of its old PIN, we decided to provide a convenient way to install QSYM with VM. Please take a look our vagrant directory.

Run hybrid fuzzing with AFL

# require to set the following environment variables
#   AFL_ROOT: afl directory (http://lcamtuf.coredump.cx/afl/)
#   INPUT: input seed files
#   OUTPUT: output directory
#   AFL_CMDLINE: command line for a testing program for AFL (ASAN + instrumented)
#   QSYM_CMDLINE: command line for a testing program for QSYM (Non-instrumented)

# run AFL master
$ $AFL_ROOT/afl-fuzz -M afl-master -i $INPUT -o $OUTPUT -- $AFL_CMDLINE
# run AFL slave
$ $AFL_ROOT/afl-fuzz -S afl-slave -i $INPUT -o $OUTPUT -- $AFL_CMDLINE
# run QSYM
$ bin/run_qsym_afl.py -a afl-slave -o $OUTPUT -n qsym -- $QSYM_CMDLINE

Run for testing

$ cd tests
$ python build.py
$ python -m pytest -n $(nproc)

Troubleshooting

If you find that you can’t get QSYM to work and you get the undefined symbol: Z3_is_seq_sort error in pin.log file, please make sure that you compile and make the target when you’re in the virtualenv (env) environment. When you’re out of this environment and you compile the target, QSYM can’t work with the target binary and issues the mentioned error in pin.log file. This will save your time a lot to compile and make the target from env and then run QSYM on the target, then QSYM will work like a charm!

Authors

Insu Yun [email protected]
Sangho Lee [email protected]
Meng Xu [email protected]
Yeongjin Jang [email protected]
Taesoo Kim

Publications

QSYM: A Practical Concolic Execution Engine Tailored for Hybrid Fuzzing

@inproceedings{yun:qsym,
  title        = {{QSYM: A Practical Concolic Execution Engine Tailored for Hybrid Fuzzing}},
  author       = {Insu Yun and Sangho Lee and Meng Xu and Yeongjin Jang and Taesoo Kim},
  booktitle    = {Proceedings of the 27th USENIX Security Symposium (Security)},
  month        = aug,
  year         = 2018,
  address      = {Baltimore, MD},
}