1 juin 2023

Linux Stack Protection By Default

Modern gcc compiler (v9.2.0) protects the stack by default and you will notice it because instead of SIGSEGV on stack overflow you will get a SIGABRT, but it also generates coredumps.




In this case the compiler adds the variable local_10. This variable helds a canary value that is checked at the end of the function.
The memset overflows the four bytes stack variable and modifies the canary value.



The 64bits canary 0x5429851ebaf95800 can't be predicted, but in specific situations is not re-generated and can be bruteforced or in other situations can be leaked from memory for example using a format string vulnerability or an arbitrary read wihout overflowing the stack.

If the canary doesn't match, the libc function __stack_chck_fail is called and terminates the prorgam with a SIGABORT which generates a coredump, in the case of archlinux managed by systemd and are stored on "/var/lib/systemd/coredump/"


❯❯❯ ./test 
*** stack smashing detected ***: terminated
fish: './test' terminated by signal SIGABRT (Abort)

❯❯❯ sudo lz4 -d core.test.1000.c611b7caa58a4fa3bcf403e6eac95bb0.1121.1574354610000000.lz4
[sudo] password for xxxx: 
Decoding file core.test.1000.c611b7caa58a4fa3bcf403e6eac95bb0.1121.1574354610000000 
core.test.1000.c611b : decoded 249856 bytes 

 ❯❯❯ sudo gdb /home/xxxx/test core.test.1000.c611b7caa58a4fa3bcf403e6eac95bb0.1121.1574354610000000 -q 


We specify the binary and the core file as a gdb parameters. We can see only one LWP (light weight process) or linux thread, so in this case is quicker to check. First of all lets see the back trace, because in this case the execution don't terminate in the segfaulted return.




We can see on frame 5 the address were it would had returned to main if it wouldn't aborted.



Happy Idea: we can use this stack canary aborts to detect stack overflows. In Debian with prevous versions it will be exploitable depending on the compilation flags used.
And note that the canary is located as the last variable in the stack so the previous variables can be overwritten without problems.




Related word

  1. Hackrf Tools
  2. Hack Tools For Games
  3. Blackhat Hacker Tools
  4. Pentest Tools Windows
  5. Pentest Tools Open Source
  6. Computer Hacker
  7. Hacking Tools For Windows Free Download
  8. Blackhat Hacker Tools
  9. Hacking Tools 2019
  10. Hack Tools For Ubuntu
  11. Hacking Tools Windows
  12. Hack And Tools
  13. New Hack Tools
  14. Hacking Tools Hardware
  15. How To Make Hacking Tools
  16. Best Hacking Tools 2019
  17. Pentest Tools For Windows
  18. Beginner Hacker Tools
  19. Underground Hacker Sites
  20. Ethical Hacker Tools
  21. Hacker Tools Apk
  22. Hacking Tools And Software
  23. Hacker Tools
  24. Hackers Toolbox
  25. Black Hat Hacker Tools
  26. Hacking Tools Mac
  27. Pentest Tools Kali Linux
  28. Bluetooth Hacking Tools Kali
  29. Hacking Tools
  30. Hack App
  31. Termux Hacking Tools 2019
  32. Hacking Tools For Windows
  33. Pentest Tools Website Vulnerability
  34. Pentest Tools For Ubuntu
  35. Nsa Hacker Tools
  36. Pentest Automation Tools
  37. How To Make Hacking Tools
  38. Hack Tools Mac
  39. Tools For Hacker
  40. Hacking Tools Name
  41. Pentest Tools Apk
  42. Hack Tools 2019
  43. Install Pentest Tools Ubuntu
  44. Pentest Tools Website
  45. What Are Hacking Tools
  46. New Hack Tools
  47. Hacker Tools Github
  48. Nsa Hack Tools Download
  49. Hacker Techniques Tools And Incident Handling
  50. Hacker Tools Apk Download
  51. Hacker Search Tools
  52. Hack Tools Github
  53. Hacking Tools Name
  54. Hacker Tools 2020
  55. Hack Tools Pc
  56. Hacking Tools 2019
  57. Hacker Tools Windows
  58. Hacker Tools Apk
  59. Hacker Tools For Pc
  60. Hacker Tools For Windows
  61. Hack Tool Apk
  62. Hacking Tools For Kali Linux
  63. Physical Pentest Tools
  64. Hacker Tools For Mac
  65. Pentest Tools For Android
  66. Hacking Tools For Mac
  67. Hacker Tools Free Download
  68. New Hacker Tools
  69. Pentest Tools Review

Aucun commentaire: