dlinject: Inject a shared library into a live linux process without ptrace

dlinject.py

Inject a shared library (i.e. arbitrary code) into a live Linux process, without ptrace. Inspired by Cexigua and linux-inject, among other things.

How it Works

• Send the stop signal to the target process. (optional)
• Locate the _dl_open() symbol.
• Retreive RIP and RSP via /proc/[pid]/syscall.
• Make a backup of part of the stack, and the code we’re about to overwrite with our shellcode, by reading from /proc/[pid]/mem.
• Generate primary and secondary shellcode buffers.
• Insert primary shellcode at RIP, by writing to /proc/[pid]/mem.
• The primary shellcode:
  • Pushes common registers to the stack.
  • Loads the secondary shellcode via mmap().
  • Jumps to the secondary shellcode.
• The secondary shellcode:
  • Restores the stack and program code to their original states.
  • Pivots the stack (so we don’t touch the original one at all).
  • Calls _dl_open() to load the user-specified library. Any constructors will be executed on load, as usual.
  • Restores register state, un-pivots the stack, and jumps back to where it was at the time of the original SIGSTOP.

Limitations:

• Sending SIGSTOP may cause unwanted side-effects, for example, if another thread is waiting on waitpid(). The –nostop option avoids this but introduces race conditions.
• I’m not entirely sure how this will interact with complex multi-threaded applications. There’s certainly potential for breakage.
• x86-64 Linux only (for now – 32-bit support could potentially be added).
• Requires root, or relaxed YAMA configuration (echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope is useful when testing).
• If the target process is sandboxed (e.g. seccomp filters), it might not have permission to mmap() the second stage shellcode, or to dlopen() the library.

Download

git clone https://github.com/DavidBuchanan314/dlinject.git

Use

usage: dlinject.py [-h] [--nostop] pid lib.so



Inject a shared library into a live process.



positional arguments:

  pid         target pid

  lib.so      Path of the shared library to load (note: must be relative to the target process's cwd, or absolute)



optional arguments:

  -h, --help  show this help message and exit

  --nostop    Don't stop the target process prior to injection (race condition-y, but avoids potential side-effects

              of SIGSTOP)

Demo

Copyright (c) 2019 David Buchana

Source: https://github.com/DavidBuchanan314/