Inject a shared library (i.e. arbitrary code) into a live linux process, without ptrace. Inspired by Cexigua and linux-inject, among other things.
.___.__ .__ __ __
__| _/| | |__| ____ |__| ____ _____/ |_ ______ ___.__.
/ __ | | | | |/ \ | |/ __ \_/ ___\ __\ \____ < | |
/ /_/ | | |_| | | \ | \ ___/\ \___| | | |_> >___ |
\____ | |____/__|___| /\__| |\___ >\___ >__| /\| __// ____|
\/ \/\______| \/ \/ \/|__| \/
source: https://github.com/DavidBuchanan314/dlinject
usage: dlinject.py [-h] [--stopmethod {sigstop,cgroup_freeze,none}]
pid /path/to/lib.so
Inject a shared library into a live process.
positional arguments:
pid The pid of the target process
/path/to/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
--stopmethod {sigstop,cgroup_freeze,none}
How to stop the target process prior to shellcode
injection. SIGSTOP (default) can have side-effects.
cgroup freeze requires root. 'none' is likely to cause
race conditions.
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Because I can.
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There are various anti-ptrace techniques, which this evades by simply not using ptrace.
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I don't like ptrace.
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Using
LD_PRELOADcan sometimes be fiddly or impossible, if the process you want to inject into is spawned by another process with a clean environment.
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Send the stop signal to the target process. (optional)
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Locate the
_dl_open()symbol. -
Retreive
RIPandRSPvia/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.
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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.
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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.
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Sending
SIGSTOPmay cause unwanted side-effects, for example if another thread is waiting onwaitpid(). The--stopmethod=cgroup_freezeoption avoids this, but requires root (on most distros, at least). -
I'm not entirely sure how this will interact with complex multi-threaded applications. There's certainly potential for breakage.
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x86-64Linux 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_scopeis 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 todlopen()the library.