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


Triforce Mod to allow test cases isolated execution

Each time QEMU does full system emulation, it creates three threads that manage the next parts: control over the Central Processing Unit (CPU), Input/Output (I/O) of the system, and Read-Copy Update (RCU) for synchronization. The trick consists of stopping the Virtual CPU (vCPU); with this, it will go out from the CPU loop, the state is recorded, and the thread still exists, keeping only the RCU and I/O threads. The process to manage the CPU will be forked, and the child process will contain the thread from the vCPU.

We can find the process in the startForkserver method from the qemu_mode/qemu/target-*/translate.c file from the different supported architectures, then we move to the afl_forkserver method, which will call the POSIX fork function to start the new process:

static target_ulong startForkserver(CPUArchState *env, target_ulong enableTicks)