Table of Contents for
Learning Linux Binary Analysis

Version ebook / Retour

Cover image for bash Cookbook, 2nd Edition Learning Linux Binary Analysis by Ryan elfmaster O'Neill Published by Packt Publishing, 2016
  1. Cover
  2. Table of Contents
  3. Learning Linux Binary Analysis
  4. Learning Linux Binary Analysis
  5. Credits
  6. About the Author
  7. Acknowledgments
  8. About the Reviewers
  9. www.PacktPub.com
  10. Preface
  11. What you need for this book
  12. Who this book is for
  13. Conventions
  14. Reader feedback
  15. Customer support
  16. 1. The Linux Environment and Its Tools
  17. Useful devices and files
  18. Linker-related environment points
  19. Summary
  20. 2. The ELF Binary Format
  21. ELF program headers
  22. ELF section headers
  23. ELF symbols
  24. ELF relocations
  25. ELF dynamic linking
  26. Coding an ELF Parser
  27. Summary
  28. 3. Linux Process Tracing
  29. ptrace requests
  30. The process register state and flags
  31. A simple ptrace-based debugger
  32. A simple ptrace debugger with process attach capabilities
  33. Advanced function-tracing software
  34. ptrace and forensic analysis
  35. Process image reconstruction – from the memory to the executable
  36. Code injection with ptrace
  37. Simple examples aren't always so trivial
  38. Demonstrating the code_inject tool
  39. A ptrace anti-debugging trick
  40. Summary
  41. 4. ELF Virus Technology �� Linux/Unix Viruses
  42. ELF virus engineering challenges
  43. ELF virus parasite infection methods
  44. The PT_NOTE to PT_LOAD conversion infection method
  45. Infecting control flow
  46. Process memory viruses and rootkits – remote code injection techniques
  47. ELF anti-debugging and packing techniques
  48. ELF virus detection and disinfection
  49. Summary
  50. 5. Linux Binary Protection
  51. Stub mechanics and the userland exec
  52. Other jobs performed by protector stubs
  53. Existing ELF binary protectors
  54. Downloading Maya-protected binaries
  55. Anti-debugging for binary protection
  56. Resistance to emulation
  57. Obfuscation methods
  58. Protecting control flow integrity
  59. Other resources
  60. Summary
  61. 6. ELF Binary Forensics in Linux
  62. Detecting other forms of control flow hijacking
  63. Identifying parasite code characteristics
  64. Checking the dynamic segment for DLL injection traces
  65. Identifying reverse text padding infections
  66. Identifying text segment padding infections
  67. Identifying protected binaries
  68. IDA Pro
  69. Summary
  70. 7. Process Memory Forensics
  71. Process memory infection
  72. Detecting the ET_DYN injection
  73. Linux ELF core files
  74. Summary
  75. 8. ECFS – Extended Core File Snapshot Technology
  76. The ECFS philosophy
  77. Getting started with ECFS
  78. libecfs – a library for parsing ECFS files
  79. readecfs
  80. Examining an infected process using ECFS
  81. The ECFS reference guide
  82. Process necromancy with ECFS
  83. Learning more about ECFS
  84. Summary
  85. 9. Linux /proc/kcore Analysis
  86. stock vmlinux has no symbols
  87. /proc/kcore and GDB exploration
  88. Direct sys_call_table modifications
  89. Kprobe rootkits
  90. Debug register rootkits – DRR
  91. VFS layer rootkits
  92. Other kernel infection techniques
  93. vmlinux and .altinstructions patching
  94. Using taskverse to see hidden processes
  95. Infected LKMs – kernel drivers
  96. Notes on /dev/kmem and /dev/mem
  97. /dev/mem
  98. K-ecfs – kernel ECFS
  99. Kernel hacking goodies
  100. Summary
  101. Index

Chapter 5. Linux Binary Protection

In this chapter, we are going to explore the basic techniques and motivations for obfuscation of Linux programs. Techniques that obfuscate or encrypt binaries or make them difficult to tamper with are called software protection schemes. By "software protection," we mean binary protection or binary hardening techniques. Binary hardening is not exclusive to Linux; in fact, there are many more products for the Windows OS in this technology genre, and there are definitely more examples to choose from for discussion.

What many people fail to realize is that Linux has a market for this too, although it largely exists for anti-tamper products used by the government. There are also a number of ELF binary protectors that were released over the last decade in the hacker community, several of which paved the way for many of the technologies used today.

An entire book could be dedicated to the art of software protection, and as the author of some of the more recent binary protection technologies for ELF, I could easily get carried away with this chapter. Instead, I will stick to explaining the fundamentals and some interesting techniques that are used, followed by some insights into my own binary protector—Maya's Veil. The tricky engineering and skills that go into binary protection make it a challenging topic to articulate, but I will do my best here.

ELF binary packers – dumb protectors

A packer is a type of software that is commonly used by malware authors and hackers to compress or encrypt an executable in order to obfuscate its code and data. One very common packer is named UPX (http://upx.sourceforge.net) and is available as a package on most Linux distributions. The original purpose of this type of packer was to compress an executable and make it smaller.

Since the code is compressed, it must have a way to decompress itself before executing in memory—this is where things get interesting, and we will discuss how this works in the Stub mechanics and the userland exec section. At any rate, malware authors have realized that compressing their malware-infected files would evade AV detection due to obfuscation. This led malware/antivirus researchers to develop automated unpackers, which are now used in most, if not all, modern AV products.

Nowadays, the term "packed binary" refers not only to compressed binaries but also to encrypted binaries or binaries that are shielded with an obfuscation layer of any kind. Since the early 2000s, there have been several remarkable ELF binary protectors that have shaped the future of binary protection in Linux. We will explore each one of these and use them to model the different techniques used to protect ELF binaries. Beforehand, however, let's look at how stubs work to load and execute a compressed or encrypted binary.