linux_injector
A simple ptrace-less shared library injector for x64 Linux.
Usage
linux_injector <mode> <pid> <file>
mode
- normal dlopen
- memfd + dlopen (for injecting into containers)
- raw shellcode
pid
Target process id. Must have ptrace rights to it (required for accessing /proc/$pid/mem). Not ptraced, so another process can freely ptrace it.
file
For mode 1: Module to inject, will be dlopened in the remote process. Should probably be a full path, because the remote LD_LIBRARY_PATH is used otherwise for resolution.
For mode 2: Module to inject, will be dlopened in the remote process from a memfd, where the content will be copied.
For mode 3: Raw shellcode to inject. You will be mapped at a 16-aligned address, and start execution on a random hijacked thread. Place hooks or create a thread, then return.
Modification
For control flow hijacking, this program needs a hijacking candidate. The code presented here uses malloc, this can be changed by editing FUN_NAME and recompiling. Make sure the hooked function can run under 100ms, so that it won't be overwritten while it executes. This means calls like sleep or wait are bad candidates for the initial shellcode. The function in question also needs to be more than 0x50 long for the shellcode not to overwrite other functions.
Supported platforms
Glibc and musl are supported for the both the target and the source process. The target process can be running in a container, and can use a different libc. Modes 2 and 3 will not require any paths accessible to the target process.
Mode 2 requires Linux 3.17.
Tested on Oracle Linux 7 (mode 2 not supported), Fedora 37, and Alpine Linux 3.17