Matching Control Flow of Program Versions

In many application areas, including piracy detection, software debugging and maintenance, situations arise in which there is a need for comparing two versions of a program that dynamically behave the same even though they statically appear to be different. Recently dynamic matching [18] was proposed by us which uses execution histories to automatically produce mappings between instructions in the two program versions. The mappings then can be used to understand the correspondence between the two versions by a user involved in software piracy detection or a comparison checker involved in debugging of optimized code. However, if a program´s control flow is substantially altered, which usually occurs in obfuscation or even manual transformations, mappings at instruction level are not sufficient to enable a good understanding of the correspondence. In this paper, we present a comprehensive dynamic matching algorithm with the focus on call graph and control flow matching. Our technique works in the presence of aggressive control flow transformations (both interprocedural such as function Mining/outlining and intraprocedural such as control flow flattening) and produces mappings of interprocedural and intraprocedural control flow in addition to mapping between instructions. We evaluated our dynamic matching algorithms by attempting to match original program with versions that were subjected to popular obfuscation and control flow altering transformations. Our experimental results show that the control flow mappings produced are highly accurate and complete, for the programs considered.