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 9. Linux /proc/kcore Analysis

So far, we have covered Linux binaries and memory as it pertains to userland. This book won't be complete, however, if we don't spend a chapter on the Linux kernel. This is because it is actually an ELF binary as well. Similar to how a program is loaded into memory, the Linux kernel image, also known as vmlinux, is loaded into memory at boot time. It has a text segment and a data segment, overlaid with many section headers that are very specific to the kernel, and which you won't see in userland executables. We will also briefly cover LKMs in this chapter, as they are ELF files too.

Linux kernel forensics and rootkits

It is important to learn the layout of the Linux kernel image if you want to be a true master of kernel forensics in Linux. Attackers can modify the kernel memory to create very sophisticated kernel rootkits. There are quite a number of techniques out there for infecting a kernel at runtime. To list a few, we have the following:

  • A sys_call_table infection
  • Interrupt handler patching
  • Function trampolines
  • Debug register rootkits
  • Exception table infection
  • Kprobe instrumentation

The techniques listed here are the primary methods that are most commonly used by a kernel rootkit, which usually infects the kernel in the form of an LKM (short for Loadable Kernel Module). Getting an understanding of each technique and knowing where each infection resides within the Linux kernel and where to look in the memory are paramount to being able to detect this insidious class of Linux malware. Firstly, however, let's take a step back and see what we have to work with. Currently, there are a number of tools in the market and in the open source world that are capable of detecting kernel rootkits and help in searches for memory infections. We will not be discussing those. We will, however, be discussing methods that are taken from kernel Voodoo. Kernel Voodoo is a project of mine that is still mostly private, with the exception of releasing a few components of it to the public, such as taskverse. This will be discussed later in this chapter, with a link to download it from. It uses some very practical techniques for detecting almost any type of kernel infection. The software is based on ideas from my original work, named Kernel Detective, which was designed in 2009, and for the curious, it can still be found on my website at http://www.bitlackeys.org/#kerneldetective.

This software works on older 32-bit Linux kernels (2.6.0 to 2.6.32) only; 64-bit support was only partially completed. Some of the ideas from this project were timeless, however, and I extracted them recently and coupled them with some new ideas. The result is Kernel Voodoo, a host intrusion detection system, and kernel forensics software that relies on /proc/kcore for advanced memory acquisition and analysis. In this chapter, we are going to discuss some of the fundamental techniques that it uses, and in some cases, we will employ them manually with GDB and /proc/kcore.