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 have a look at how these complicate reverse engineering. Afterwards, we gradually become familiar 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 VM hardening techniques and see how to deal with 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.
The last part covers program synthesis, an approach that learns the code’s semantics based on its input-output behavior. We explore how to collect input-output pairs; then, we use program synthesis to deobfuscate mixed Boolean-Arithmetic and learn the semantics of VM instruction handlers.
- 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 - deobfuscating VM-based obfuscation schemes - interaction with SMT solvers - breaking opaque predicates
- concept of program synthesis - learning code semantics based on its input/output behavior - obtaining input/output pairs from code - deobfuscating mixed Boolean-Arithmetic - learning semantics of VM instruction handlers