Around the start of the year, I was pretty burnt out on CTF problems and was interested in writing an exploit for something more complicated and practical. I settled on writing a WebKit exploit for a few reasons:
- It is code that is broadly used in the real world
- Browsers seemed like a cool target in an area I had little familiarity (both C++ and interpreter exploitation.)
- WebKit is (supposedly) the softest of the major browser targets.
- There were good existing resources on WebKit exploitation, namely saelo’s Phrack article, as well as a variety of public console exploits.
With this in mind, I got a recommendation for an interesting looking bug that has not previously been publicly exploited: @natashenka’s CVE-2017-2446 from the project zero bugtracker. The bug report had a PoC which crashed in
memcpy() with some partially controlled registers, which is always a promising start.
Finally, the goal of doing this initially and now writing it up was and is to learn as much as possible. There is clearly a lot more for me to learn in this area, so if you read something that is incorrect, inefficient, unstable, a bad idea, or just have some thoughts to share, I’d love to hear from you.more ...
Below is a collection of notes regarding unikernels. I had originally prepared this stuff to submit to EkoParty’s CFP, but ended up not wanting to devote time to stabilizing PHP7’s heap structures and I lost interest in the rest of the project before it was complete. However, there are still some cool takeaways I figured I could write down. Maybe they’ll come in handy? If so, please let let me know.
Unikernels are a continuation of turning everything into a container or VM. Basically, as many VMs currently just run one userland application, the idea is that we can simplify our entire software stack by removing the userland/kernelland barrier and essentially compiling our usermode process into the kernel. This is, in the implementation I looked at, done with a NetBSD kernel and a variety of either native or lightly-patched POSIX applications (bonus: there is significant lag time between upstream fixes and rump package fixes, just like every other containerized solution).
While I don’t necessarily think that conceptually unikernels are a good idea (attack surface reduction vs mitigation removal), I do think people will start more widely deploying them shortly and I was curious what memory corruption exploitation would look like inside of them, and more generally what your payload options are like.
All of the following is based off of two unikernel programs, nginx and php5 and only makes use of public vulnerabilities. I am happy to provide all referenced code (in varying states of incompleteness), on request.more ...
A few months ago, I was writing a Linux kernel exploitation challenge on ARM in an attempt to learn about kernel exploitation and I thought I'd explore things a little. I chose the ARM architecture mainly because I thought it would be fun to look at. This article is going to describe how the ARM Exception Vector Table (EVT) can aid in kernel exploitation in case an attacker has a write what-where primitive. It will be covering a local exploit scenario as well as a remote exploit scenario. Please note that corrupting the EVT has been mentioned in the paper "Vector Rewrite Attack", which briefly talks about how it can be used in NULL pointer dereference vulnerabilities on an ARM RTOS.
The article is broken down into two main sections. First a brief description of the ARM EVT and its implications from an exploitation point of view (please note that a number of things about the EVT will be omitted to keep this article relatively short). We will go over two examples showing how we can abuse the EVT.
I am assuming the reader is familiar with Linux kernel exploitation and knows some ARM assembly (seriously).more ...
I am currently playing with pool-based memory corruption vulnerabilities. That’s why I wanted to program a PoC exploit for the vulnerability presented by Tarjei Mandt during his first talk “Kernel Pool Exploitation on Windows 7” . I think it's a good exercise to start learning about pool overflows.more ...