Book Image

Learning Linux Binary Analysis

By : Ryan "elfmaster" O'Neill
5 (1)
Book Image

Learning Linux Binary Analysis

5 (1)
By: Ryan "elfmaster" O'Neill

Overview of this book

Learning Linux Binary Analysis is packed with knowledge and code that will teach you the inner workings of the ELF format, and the methods used by hackers and security analysts for virus analysis, binary patching, software protection and more. This book will start by taking you through UNIX/Linux object utilities, and will move on to teaching you all about the ELF specimen. You will learn about process tracing, and will explore the different types of Linux and UNIX viruses, and how you can make use of ELF Virus Technology to deal with them. The latter half of the book discusses the usage of Kprobe instrumentation for kernel hacking, code patching, and debugging. You will discover how to detect and disinfect kernel-mode rootkits, and move on to analyze static code. Finally, you will be walked through complex userspace memory infection analysis. This book will lead you into territory that is uncharted even by some experts; right into the world of the computer hacker.
Table of Contents (17 chapters)
Learning Linux Binary Analysis
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Debug register rootkits – DRR


This type of kernel rootkit uses the Intel Debug registers as a means to hijack the control flow. A great Phrack paper was written by halfdead on this technique. It is available here:

http://phrack.org/issues/65/8.html.

This technique is often hailed as ultra-stealth because it requires no modification of sys_call_table. Once again, however, there are ways of detecting this type of infection as well.

Detecting DRR

In many rootkit implementations, sys_call_table and other common infection points do go unmodified, but the int1 handler does not. The call instruction to the do_debug function gets patched to call an alternative do_debug function, as shown in the phrack paper linked earlier. Therefore, detecting this type of rootkit is often as simple as disassembling the int1 handler and looking at the offset of the call do_debug instruction, as follows:

target_address = address_of_call + offset + 5

If target_address has the same value as the do_debug address found in...