Advanced Static Analysis for Decompilation Using Scattered Context Grammars

Abstract: Reverse program compilation (i.e. decompilation) is a process heavily exploited in reverse engineering. The task of decompilation is to transform a platform-specific executable into a high-level language representation, which is usually the C language. Such a process can be used for source code reconstruction, compiler testing, mal-ware analysis, etc. In present, there are several existing decompilers that are able to decompile simple applications. However, we can see a drop-off in terms of the quality of the generated code when the decompiled code is highly optimized (e.g. usage of instruction idioms) or obfuscated (e.g. dead code insertion, register renaming). Optimized or obfuscated applications are usually generated by highly optimizing compilers or metamorphic engines (used by malware authors). In this paper, we present several innovative decompilation methods based on scattered context grammars. These methods are able to effectively decompile optimized or obfuscated code. For demonstration, we used these methods for enhancement of the static analysis phase of an existing decompiler. Experimental results of our solution are presented at the end of the paper. Key–Words: decompilation, Lissom, static analysis, LLVM IR, scattered context grammars