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

Resistance to emulation

Often, emulators are used to perform dynamic analysis and reverse engineering tasks on executables. One very good reason for this is that they allow the reverse engineer to easily instrument the control of the execution, and they also bypass a lot of typical anti-debugging techniques. There are many emulators being used out there—QEMU, BOCHS, and Chris Eagles' IDA X86 emulator plugin, to name some. So, countless anti-emulation techniques exist, but some of them are specific to each emulator's particular implementation.

This topic could expand into some very in-depth discussions and move in many directions, but I will keep it limited to my own experience. In my own experimentation with emulation and anti-emulation in the Maya protector, I have learned some generic techniques that should work against at least some emulators. The goal of our binary protector's anti-emulation is to be able to detect when it is being run in an emulator, and if this is true, it should halt the execution and exit.

Detecting emulation through syscall testing

This technique can be especially useful in application-level emulators that are somewhat OS agnostic and are unlikely to have implemented more than the basic system calls (read, write, open, mmap, and so on). If an emulator does not support a system call and also does not delegate the unsupported syscall to the kernel, it is very likely that it will posit an erroneous return value.

So, the binary protector could invoke a handful of less common syscalls and check whether the return value matches the expected value. A very similar technique would be to invoke certain interrupt handlers to see whether they behave correctly. In either case, we are looking for OS features that were not properly implemented by the emulator.

Detecting emulated CPU inconsistencies

The chances of an emulator perfectly emulating CPU architectures are next to none. Therefore, it is common to look for certain inconsistencies between how the emulator behaves and how the CPU should behave. One such technique is to attempt writing to privileged instructions, such as debug registers (for example, db0 to db7) or control registers (for example, cr0 to cr4). The emulation detection code may have a stub of ASM code that attempts to write to cr0 and see whether it succeeds.

Checking timing delays between certain instructions

Another technique that can sometimes cause instability in the emulator itself is checking the timestamps between certain instructions and seeing how long the execution took. A real CPU should execute a sequence of instructions several magnitudes faster than an emulator.