Android Hacker's Handbook

Chapter 6Finding Vulnerabilities with Fuzz Testing

Fuzz testing, or fuzzing for short, is a method for testing software input validation by feeding it intentionally malformed input. This chapter discusses fuzzing in great detail. It introduces you to the origins of fuzzing and explains the nuances of various associated tasks. This includes target identification, crafting inputs, system automation, and monitoring results. The chapter introduces you to the particulars of fuzzing on Android devices. Finally, it walks you through three fuzzers tested during the writing of this book, each with their own approaches, challenges, and considerations. These serve as examples of just how easy it is to find bugs and security vulnerabilities with fuzzing. After reading this chapter, you will understand fuzzing well enough to apply the technique to uncover security issues lurking in the Android operating system.

Fuzzing Background

Fuzz testing has a long history and has been proven effective for finding bugs. It was originally developed by Professor Barton Miller at the University of Wisconsin—Madison in 1988. It started as a class project to test various UNIX system utilities for faults. However, in the modern information security field it serves as a way for security professionals and developers to audit the input validation of software. In fact, several prominent security researchers have written books entirely focused on the subject. This simple technique has led to the discovery of ...