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

/proc/kcore and GDB exploration

The /proc/kcore technique is an interface for accessing kernel memory, and is conveniently in the form of an ELF core file that can be easily navigated with GDB.

Using GDB with /proc/kcore is a priceless technique that can be expanded to very in-depth forensics for the skilled analyst. Here is a brief example that shows how to navigate sys_call_table.

An example of navigating sys_call_table

$ sudo gdb -q vmlinux /proc/kcore
Reading symbols from vmlinux...
[New process 1]
Core was generated by `BOOT_IMAGE=/vmlinuz-3.16.0-49-generic root=/dev/mapper/ubuntu--vg-root ro quiet'.
#0  0x0000000000000000 in ?? ()
(gdb) print &sys_call_table
$1 = (<data variable, no debug info> *) 0xffffffff81801460 <sys_call_table>
(gdb) x/gx &sys_call_table
0xffffffff81801460 <sys_call_table>:  0xffffffff811d5260
(gdb) x/5i 0xffffffff811d5260
   0xffffffff811d5260 <sys_read>:  data32 data32 data32 xchg %ax,%ax
   0xffffffff811d5265 <sys_read+5>:  push   %rbp
   0xffffffff811d5266 <sys_read+6>:  mov    %rsp,%rbp
   0xffffffff811d5269 <sys_read+9>:  push   %r14
   0xffffffff811d526b <sys_read+11>:mov    %rdx,%r14

In this example, we can look at the first pointer held in sys_call_table[0] and determine that it contains the address of the syscall function sys_read. We can then look at the first five instructions of that syscall. This is an example of how easy it is to navigate kernel memory using GDB and /proc/kcore. If there had been a kernel rootkit installed that hooked sys_read with function trampolines, then displaying the first few instructions would have shown a jump or return to another malicious function. Using a debugger in this manner to detect kernel rootkits is very useful if you know what to look for. The structural nuances of the Linux kernel and how it may be infected are advanced topics and seem esoteric to many people. One chapter is not enough to fully demystify all of this, but we will cover the methods that may be used to infect the kernel and detect the infections. In the following sections, I will discuss a few approaches used to infect the kernel from a general standpoint, while giving some examples.

Note

Using just GDB and /proc/kcore, it is possible to detect every type of infection that is mentioned throughout this chapter. Tools such as kernel Voodoo are very nice and convenient but are not absolutely necessary to detect deviations from a normally operating kernel.