3.0 KiB
Introduction
This test uses american fuzzy lop to mangle real dns, dhcp client, dhcp server packets and look for exceptions caused by the parser.
A few actual packets are collected and exported as bins in the in_dns, in_dhcp_client, in_dhcp_server folders, 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/lwip/test_afl_host
make fuzz MODE=dns/dhcp_client/dhcp_server
(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 $IDF_PATH/components/lwip/test_afl_host
make INSTR=off MODE=dns/dhcp_client/dhcp_server
Installing AFL
To run the test yourself, you need to download the latest afl archive and extract it to a folder on your computer.
The rest of the document will refer to that folder as PATH_TO_AFL.
Preparation
-
On Mac, you will need to install the latest Xcode and llvm support from Homebrew
/usr/bin/ruby -e "$(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:$PATH" -
On Ubuntu you need the following packages:
sudo apt-get install make clang-4.0(or <=4.0) llvm-4.0(or <=4.0) libbsd-dev
Please note that if specified package version can't be installed(becouse the system is newer than 2017), you can install it from source.
Compile AFL
Compiling AFL is as easy as running make:
cd [PATH_TO_AFL]
make
cd llvm_mode/
make
After successful compilation, you can export the following variables to your shell (you can also add them to your profile if you want to use AFL in other projects).
export AFL_PATH=[PATH_TO_AFL]
export PATH="$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 AFL's 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