Reverse Engineering Shaochun Xu Computer Science University of Windsor

Reverse Engineering Shaochun Xu Computer Science University of Windsor

Contents What is Reverse Engineering (RE)? Why do we need Reverse Engineering? Scope and Tasks of Reverse Engineering Different Approaches RE tools Conclusions

What is Reverse Engineering ? You have an unexpected case: You finished one course project using Java Your program runs OK But, by accident, you delete the java file How to hand in your project?

What is Reverse Engineering ? You have an unexpected case: You finished one course project using Java Your program runs OK But, by accident, you delete the java file How to hand in your project? Reverse Engineering

What is Reverse Engineering ? Waterfall Model of software development Requirement analysis design Implementation Testing and Maintenance

What is Reverse Engineering ? Forward Engineering Requirements Design Source Code Behavior

What is Reverse Engineering ? Forward Engineering Reverse Engineering Requirements Design Source Code Behavior

What is Reverse Engineering ? Abstraction System Reverse Engineering Abstraction Old system Forward Engineering Re-Implementation New System

What is Reverse Engineering? RE encompasses any activity that is done to determine how a product works, to learn the ideas and technology that were used in developing that product. RE can be done at many levels RE generally belongs to Software Maintenance

The Early Days of RE Law of Software Revolution (Lehman, 1980) Fundamental strategies for program comprehension (Brooks, 1983) Taxonomy of Reverse Engineering (Chikofsky&Cross, 1990) WCRE (Working Conference on R.E., 1990) IWPC (Int. Workshop on Program Comprehension)

Why do we need RE ? Recovery of lost information providing proper system documentation Assisting with maintenance identification of side effects and anomalies Migration to another hw/sw platform Facilitating software reuse

Why do we need RE ? Benefits maintenance cost savings quality improvements competitive advantages software reuse facilitation

Difficulties of Reverse Engineering Gap between problem /solution domain Gap between concrete and abstract Gap between coherency/disintegration Gap between hierarchical/associational

Scope and Task of Reverse Engineering program understanding Problem/Application domain Mapping Program/Implemen. domain

Scope and Task of Reverse Engineering Redocumentation and/or document generation Recovery of design approach and design details at any level of abstraction Identifying reusable components and components that need restructuring Recovering business rules Understanding high-level system description.

Discovery of Abstraction Discovery of abstraction in large system maintenance purpose evolution purpose reengineering purpose

Levels of abstractions Application Application concepts, business rule, policies Function Logical and functional specification, non-functional requirement Structure Data and control flow, dependency graphs Structure and subsystem charts Architectures Implementation Symbol tables, source text

Different Approaches Restructuring Transformation from one representation to another at the same level, Requirements Design Source code Behavior

Different Approaches Reverse Engineering Design Recovery – reproduce all the info for understanding the system Re-documentation – provide different views of the system Re-Engineering first phase --understanding the system second phase--forward engineering

Different Approaches Abstraction System Reverse Engineering Abstraction Old system Forward Engineering Re-Implementation New System

Reverse Engineering Tools Analysis Tools Browsers Object Server Task Oriented Tools

Example--Java Decompiler How to recover bytecode from .class file under Unix/Win with JDK? % javap -c filename % javap -help (to see the options) Java Decompilers ”ClassCracker” http://www.pcug.org.au/ mayon/ “DeCafe Pro" from DeCafe, France at http://decafe.hypermart.net/index.htm “SourceAgain" from Ahpah corp at http://www.ahpah.com

Example--Java Decompiler ClassCracker 2 Interface

Example--Java Decompiler Components of ClassCracker 2 Java decompiler – retrieves Java source code from Java class files Java disassembler – produces Java Assembly Code A Java class file viewer – displays Java class file structures.

Example--Java Decompiler Features of ClassCracker 2 User visual interface. Can decompile class files within zip or jar files. Conversion mode (JAVA, JASM or JDUMP) is selectable A Batc Mode allows multiple class files to be decompiled simultaneously more .

Example--Java Decompiler ClassCracker 2 System Requirements All platform (Window/Linus/Unix) JDK /JRE Do not believe it? From myClass origin.class myClass.java % javac myClass.java ( myClass.class) % diff myClass.class myClass origin.class

Example--Java Decompiler ClassCracker 2.0--want to try it? Free download at http://www.pcug.org.au/ mayon/classcracker/ccgetdemo.htm l Only first three methods are decoded. Bridge 1.0---Free http://www.geocities.com/SiliconValley/Bridge/8617/ jad.html

Conclusions Reverse Engineering is a new research area among software maintenance RE includes activities of understanding the system and recovery info from system Program understanding is the most important subset of Reverse Engineering Discovery of abstraction is key issue

Questions ?