This class is intended for students who have basic experience in reverse engineering and have to deal with obfuscated code. Furthermore, the course is also interesting for experienced reverse engineers who aim to deepen their understanding in program analysis techniques and code (de)obfuscation.
In this training, we get to know state-of-the-art code obfuscation techniques and look at how these complicate reverse engineering. Afterwards, we gradually familiarize ourselves with different deobfuscation techniques and use them to break obfuscation schemes in hands-on sessions. Thereby, participants will deepen their knowledge of program analysis and learn when and how (not) to use different techniques.
First, we have a look at important code obfuscation techniques and discuss how to attack them. Afterwards, we analyze a virtual machine-based (VM-based) obfuscation scheme, learn about VM hardening techniques and how to tackle them.
In the second part, we cover SMT-based program analysis. In detail, students learn how to solve program analysis problems with SMT solvers, how to prove characteristics of code, how to deobfuscate mixed Boolean-Arithmetic and how to break weak cryptography.
Before we use symbolic execution to automate large parts of code deobfuscation, we first introduce intermediate languages and compiler optimizations to simplify industrial-grade obfuscation schemes. Following, we use symbolic execution to automate SMT-based program analysis and break opaque predicates. Finally, we learn how to write disassemblers for virtualization-based obfuscators and how to reconstruct the original code.
The last part covers program synthesis, an approach to simplify code based on its semantic behavior. After collecting input-output pairs from binary code, we not only learn how to simplify large expression trees, but also how we can verify the correctness of simplifications. Then, we use program synthesis to deobfuscate mixed Boolean-Arithmetic and learn the semantics of VM instruction handlers.
**Note that the training focuses on hands-on sessions. While some lecture parts provide an understanding of when to use which method, various hands-on sessions teach how to use them to build custom purpose tools for one-off problems. The trainer actively supports the students to successfully solve the given tasks. After a task is completed, we discuss different solutions in class. Furthermore, students receive detailed reference solutions that can be used during and after the course.
While the hands-on sessions use x86 assembly, all tools and techniques can also be applied to other architectures such as MIPS, PPC or ARM.
- Motivation - Application Scenarios - Program Analysis Techniques
- Opaque Predicates - Control-flow Flattening - Mixed Boolean-Arithmetic - Virtual Machines - Virtual Machine Hardening
- Compiler Optimizations - Reconstructing Control Flow - SMT-based Program Analysis - Taint Analysis - Symbolic Execution - Program Synthesis
- Dead Code Elimination - Constant Propagation/Folding - Static Single Assignment (SSA) - Optimizing Obfuscated Code
- SAT and SMT Solvers - Encoding Programs Analysis Problems for SMT Solvers - Proving Semantic Equivalence - Proving Properties of a Piece of Code - Solving Complex Program Constraints - Deobfuscating Mixed Boolean-Arithmetic - Breaking Weak Cryptography
- Intermediate Languages for Reverse Engineering - Symbolic and Semantic Simplification of Obfuscated Code - Automation in Reverse Engineering - Identifying Virtual Machine Components - Interaction With SMT Solvers - Breaking Opaque Predicates - Writing Disassemblers for Virtualization-based Obfuscators
- Concept of Program Synthesis - Learning Code Semantics Based on its Input/Output Behavior - Obtaining Input/Output Pairs from Code - Methods to Simplify Large Expression Trees - Proving the Correctness of Simplifications - Deobfuscating mixed Boolean-Arithmetic - Learning Semantics of VM Instruction Handlers
Tim Blazytko @mr_phrazer is a well-known binary security researcher and co-founder of emproof. After working on novel methods for code deobfuscation, fuzzing and root cause analysis during his PhD, Tim now builds code obfuscation schemes tailored to embedded devices. Moreover, he gives trainings on reverse engineering & code deobfuscation, analyzes malware and performs security audits.
What students say about this training:
From Tim’s past HITB training
Would you recommend this class, or attend other classes by this trainer?
“I would absolutely recommend others take this class or any other classes taught by Tim”
“Yes, I would definitely recommend this class to any reverse engineers wanting to advance their skills, and I would attend other classes by this trainer.”
“Absolutely recommend this class. It has met and exceed all my expectations!”
What part of this course did you find most useful and interesting?
“I found all of it very interesting. The most useful parts to me were the coding/reversing exercises. That really helps to cement my understanding of the topics discussed”
“The latter part, dealing with the automation of analysis, [where we were] applying the theory of techniques covered earlier on”
“It is very difficult to fault any component of this course, its appears as a very mature and well refined project. Tim is clearly very passionate on the subjects and that is portrayed through the material and delivery.”