Ankou

Ankou

Ankou is a source-based grey-box fuzzer. It intends to use a more rich fitness function by going beyond simple branch coverage and considering the combination of branches during program execution. The details of the technique can be found in our paper "Ankou: Guiding Grey-box Fuzzing towards Combinatorial Difference", which is published in ICSE 2020.

Dependencies.

Go

Ankou is written solely in Go and thus requires its installation. Be sure to configure this GOPATH environment variable, for example to ~/go directory.

AFL

Ankou relies on AFL instrumentation: fuzzed targets needs to compiled using afl-gcc or afl-clang. To install AFL:

wget http://lcamtuf.coredump.cx/afl/releases/afl-latest.tgz
tar xf afl-latest.tgz
cd afl-2.52b
make
# The last command is optional, but you'll need to provide the absolute path to
# the compiler in the configure step below if you don't install AFL compiler.
sudo make install

GDB

For the triaging gdb is required, and ASLR needs to be deactivated:

sudo echo 0 | sudo tee /proc/sys/kernel/randomize_va_space

Note that when using docker containers, this needs to be run in the host.

Installation

Once Go and AFL are installed, you can get Ankou by:

go get github.com/SoftSec-KAIST/Ankou   # Clone Ankou and its dependencies
go build github.com/SoftSec-KAIST/Ankou # Compile Ankou

mkdir -p $GOPATH/src/github.com/SoftSec-KAIST
cd $GOPATH/src/github.com/SoftSec-KAIST
git clone REPO  # By default REPO is https://github.com/SoftSec-KAIST/Ankou
cd Ankou
go get .    # Get dependencies
go build .  # Compile

Usage

Now we are ready to fuzz. We first to compile any target we want with afl-gcc or afl-clang. Let's take the classical starting example for fuzzing, binutils:

wget https://mirror.ibcp.fr/pub/gnu/binutils/binutils-2.33.1.tar.xz
tar xf binutils-2.33.1.tar.xz
cd binutils-2.33.1
CC=afl-gcc CXX=afl-g++ ./configure --prefix=`pwd`/install
make -j
make install

Now we are ready to run Ankou:

cd install/bin
mkdir seeds; cp elfedit seeds/ # Put anything in the seeds folder.
go run github.com/SoftSec-KAIST/Ankou -app ./readelf -args "-a @@" -i seeds -o out
# Or use the binary we compiled above:
/path/to/Ankou -app ./readelf -args "-a @@" -i seeds -o out

Evaluation Reproduction

Once Ankou is installed, in order to reproduce the Ankou evaluation:

1. Compile the 24 packages mentioned in the paper at the same version or commit using afl-gcc. All the packages' source can be found with the same version used in Ankou evaluation at https://github.com/SoftSec-KAIST/Ankou-Benchmark. Additionnally, this repository includes the seeds used to initialize the evalution fuzzing campaigns.
2. Run the produced subjects with the commands found in benchmark/configuration.json. benchmark/rq1_rq3.json only contains the 24 subjets used for Research Question 1 and 3 of the paper.
3. Analyze Ankou output directory for results. Crashes are listed in $OUTPUT_DIR/crashes-* and found seeds in $OUTPUT_DIR/seeds-*. Statistics of the fuzzing campaign can be found in the $OUTPUT_DIR/status* directory CSV files. The edge_n value of receiver.csv represents the branch coverage. And the execN column of seed_manager.csv represents the total number of test cases executed so far. Divide it by the time column to obtain the throughout.

There are too many programs in our benchmark, so we will use only one package in this example: cflow.

1. Compilation.

git clone https://github.com/SoftSec-KAIST/Ankou-Benchmark
cd Ankou-Benchmark
tar xf seeds.tar.xz
cd sources
tar xf cflow-1.6.tar.xz
cd cflow-1.6
CC=afl-gcc CXX=afl-g++ ./configure --prefix=`pwd`/build
make -j
make install
cd ../../..

1. Preparation of the fuzzing campaign.

mkdir fuzzrun
cp Ankou-Benchmark/sources/cflow-1.6/build/bin/cflow fuzzrun
cp -r Ankou-Benchmark/seeds/cflow fuzzrun/seeds

1. Run the campaign. The above starts a 24 hours fuzzing campaign. The '-dur' option can be adjusted, or Ankou interrupted earlier. In this version of cflow, and initialized with these seeds, a crash should be found in less than an hour.

cd fuzzrun
go run github.com/SoftSec-KAIST/Ankou -app cflow -args "-o /dev/null @@" \
    -i seeds -threads 1 -o cflow_out -dur 24h

1. Results analysis

cd cflow_out/status_*
# Print the final branch coverage:
python -c "print(open('receiver.csv').readlines()[-1].split(',')[0])"
# Print the overall throughput:
python -c "last = open('seed_manager.csv').readlines()[-1].split(','); print(float(last[5])/int(last[6]))"
# Print effectiveness of the dynamic PCA (see RQ2):
python -c "last = open('receiver.csv').readlines()[-1].split(','); print('{}%'.format(100-100*float(last[2])/float(last[1])))"

Safe Stack Hash Triaging

Once the environment is setup, the scripts works in two steps:

1. Run the binary on the crashing input to produce a core file. Using ulimit -c unlimited ensures the core to be dumped.
2. Use the scripts in the triage folder of this repository:

cd $GOPATH/src/github.com/SoftSec-KAIST/Ankou/triage
gdb -x triage.py -x triage.gdb -batch -c /path/to/core /path/to/binary
cat hash.txt # The stack hashes are found in this text file.