Malifar GPU-accelerated NSEC3 Zone Walker

Disclaimer

This tool may generate a large amount of DNS traffic to critical infrastructure. While the default settings are believed to be safe, be sure you understand the consequences of launching large scans before your run this tool on large DNS zones.

How it works

Malifar works by exploiting the NSEC3 zone walking weakness. It's splitting the work between two processes: the main dumper (dumper.py) and a GPU-accelerated crackserver.py. The dumper generates requests to splice the unexplored areas in the hashed nsec3 space. Unexplored areas are sent to the crackserver process and fqdn candidates are sent back. In most cases this is very fast, but sometimes tough holes are found that may require between 10 minutes and a few hours of cracking. By default, no job more difficult than 2^39 will be sent to the crack server but this can be configured in config_local.py or -m command line option.

./dumper.py domain

The dumper generates three files:

domain-DATE.zone: this file contains the zone information that was extracted from the zone.
domain.cache: a cache file containing all intermediate hashes that were useful to the domain extraction. This file will be reused later so less GPU cracking is required.
domain.restore: a very simple snapshot of the scanner's state so a scan can be recovered later.

The files may be extracted in a way that can be parsed by hashcat with

./haptool.py -f workdir/domain-date.zone hashcat -o out.hashcat

How does it differ from nsec3map

nsec3map works really well but requires a lot of memory and CPU on larger zones. Malifar has a few notable differences:

GPU acceleration: searching for intermediate hashes is accelerated with OpenCL. x1000 performance boost
asyncio design: more modern Python and better handling of IOs
DNS over TCP instead of UDP
GPU cracking and network parts can be on different computers
Optimized cache and result files
Optimized RAM usage. Malifar dumps a 10M records zone with less than 1G RAM on a single core.
Per-domain configuration parameters in case we repeat scans regularly.

Malifar currently does not support NSEC and does not implement any attack against anti-scanning countermeasures.

Installation

You need Swig 4, CMake, libssl-dev.

mkdir hap/build
cd hap/build
cmake ..
make
cd ../..
pip3 install -r requirements.txt

Malifar has been tested on Ubuntu 22.04 with nvidia RTX cards and osx on M2. Other platforms may require tweaking the OpenCL code.

Publications

Malifar will be presented at SSTIC2024 https://www.sstic.org/2024/presentation/dig_com_axfr_dnssec__lister_linternet_grce__dnssec/

arisada / malifar