Biblio

This paper argues about a new conceptual modeling language for the White-Box (WB) security analysis. In the WB security domain, an attacker may have access to the inner structure of an application or even the entire binary code. It becomes pretty easy for attackers to inspect, reverse engineer, and tamper the application with the information they steal. The basis of this paper is the 14 patterns developed by a leading provider of software protection technologies and solutions. We provide a part of a new modeling language named i-WBS (White-Box Security) to describe problems of WB security better. The essence of White-Box security problem is code security. We made the new modeling language focus on code more than ever before. In this way, developers who are not security experts can easily understand what they need to really protect.

Code obfuscation is the de facto standard to protect intellectual property when delivering code in an unmanaged environment. It relies on additive layers of code tangling techniques, white-box encryption calls and platform-specific or tool-specific countermeasures to make it harder for a reverse engineer to access critical pieces of data or to understand core algorithms. The literature provides plenty of different obfuscation techniques that can be used at compile time to transform data or control flow in order to provide some kind of protection against different reverse engineering scenarii. Scheduling code transformations to optimize a given metric is known as the pass scheduling problem, a problem known to be NP-hard, but solved in a practical way using hard-coded sequences that are generally satisfactory. Adding code obfuscation to the problem introduces two new dimensions. First, as a code obfuscator needs to find a balance between obfuscation and performance, pass scheduling becomes a multi-criteria optimization problem. Second, obfuscation passes transform their inputs in unconventional ways, which means some pass combinations may not be desirable or even valid. This paper highlights several issues met when blindly chaining different kind of obfuscation and optimization passes, emphasizing the need of a formal model to combine them. It proposes a non-intrusive formalism to leverage on sequential pass management techniques. The model is validated on real-world scenarii gathered during the development of an industrial-strength obfuscator on top of the LLVM compiler infrastructure.