Towards Automated Generation of Exploitation Primitives for Web Browsers

Behrad Garmany, Martin Stoffel, Robert Gawlik, Philipp Koppe, Tim Blazytko, Thorsten Holz

Annual Computer Security Applications Conference (ACSAC), San Juan, Puerto Rico, USA, December 2018


The growing dependence on software and the increasing complexity of such systems builds and feeds the attack surface for exploitable vulnerabilities. Security researchers put up a lot of effort to develop exploits and analyze existing exploits with the goal of staying ahead of the state-of-the-art in attacks and defenses. The urge for automated systems that operate at scale, speed and efficiency is therefore undeniable. Given their complexity and large user base, web browsers pose an attractive target. Due to various mitigation strategies, the exploitation of a browser vulnerability became a time consuming, multi-step task: creating a working exploit even from a crashing input is a resource-intensive task that can take a substantial amount of time to complete.

In this paper, we introduce novel methods to significantly improve and partially automate the development process for browser exploits. Our approach is based on the observation that an analyst typically performs certain manual analysis steps that can be automated. This serves the purpose to propagate the bug-induced, controlled data to a specific program location to carry out a desired action. These actions include achieving write-what-where or control over the instruction pointer primitives. These are useful to extend control over the target program and are necessities towards successful code execution, the ultimate goal of the adversary. We implemented a prototype of our approach called PrimGen. For a given browser vulnerability, it is capable of automatically crafting data objects that lead the execution to a desired action. We show in our evaluation that our approach is able to generate new and previously unknown exploitation opportunities for real-world vulnerabilities in Mozilla Firefox, Internet Explorer, and Google Chrome. Using small templates, PrimGen generates inputs that conducts specific primitives. In total, PrimGen has found 48 alternative JavaScript inputs which conduct the desired primitives when fed into the target browsers.