Book Image

Fuzzing Against the Machine

By : Antonio Nappa, Eduardo Blázquez
Book Image

Fuzzing Against the Machine

By: Antonio Nappa, Eduardo Blázquez

Overview of this book

Emulation and fuzzing are among the many techniques that can be used to improve cybersecurity; however, utilizing these efficiently can be tricky. Fuzzing Against the Machine is your hands-on guide to understanding how these powerful tools and techniques work. Using a variety of real-world use cases and practical examples, this book helps you grasp the fundamental concepts of fuzzing and emulation along with advanced vulnerability research, providing you with the tools and skills needed to find security flaws in your software. The book begins by introducing you to two open source fuzzer engines: QEMU, which allows you to run software for whatever architecture you can think of, and American fuzzy lop (AFL) and its improved version AFL++. You’ll learn to combine these powerful tools to create your own emulation and fuzzing environment and then use it to discover vulnerabilities in various systems, such as iOS, Android, and Samsung's Mobile Baseband software, Shannon. After reading the introductions and setting up your environment, you’ll be able to dive into whichever chapter you want, although the topics gradually become more advanced as the book progresses. By the end of this book, you’ll have gained the skills, knowledge, and practice required to find flaws in any firmware by emulating and fuzzing it with QEMU and several fuzzing engines.
Table of Contents (18 chapters)
Part 1: Foundations
Part 2: Emulation and Fuzzing
Part 3: Advanced Concepts
Chapter 12: Conclusion and Final Remarks

Preparing your harness to start fuzzing

The objective of this chapter is to design a syscall fuzzer for iOS. To achieve this, we leveraged Trung’s harness, incorporating as much of it as possible, which is primarily located in softmmu/main.c and is generally understandable. Trung crafted a very handy harness that avoids some of the delays of TriforceAFL. Thanks to the dup2() call, we just bring AFL’s output to QEMU’s stdin with a little trick, by duplicating its standard input to a safer file descriptor. The dup2() call moves the file descriptor 0 (which is the QEMU stdin) to descriptor number 9. This is an arbitrary choice to avoid conflicts with other program descriptors and, simultaneously isolate the interaction of AFL with QEMU to a specific file descriptor. Let’s observe the code in bold:

 56 int main(int argc, char **argv, char **envp)
 57 {
 58     if (getenv(SHM_ENV_VAR)) {
 59       ...