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Library for injecting a shared library into a Linux or Windows process
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Makefile.win32
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README.md

Injector

Library for injecting a shared library into a Linux or Windows process

Linux

I was inspired by linux-inject and the basic idea came from it. However the way to call __libc_dlopen_mode in libc.so.6 is thoroughly different.

  • linux-inject writes about 80 bytes of code to the target process on x86_64. This writes only four or eight bytes.
  • linux-inject writes code at the firstly found executable region of memory, which may be referred by other threads. This writes it at the entry point of libc.so.6, which will be referred by nobody unless the libc itself is executed as a program.

This was tested only on Ubuntu 16.04 x86_64 and Debian 8 arm64. It may not work on other distributions.

Windows

Windows version is also here. It uses well-known CreateRemoteThread+LoadLibrary technique to load a DLL into another process with some improvements.

  1. It gets Win32 error messages when LoadLibrary fails by copying assembly code into the target process.
  2. It can inject a 32-bit dll into a 32-bit process from 64-bit processes by checking the export entries in 32-bit kernel32.dll.

Compilation

Linux

$ git clone https://github.com/kubo/injector.git
$ cd injector
$ make

The make command creates:

filename -
src/linux/libinjector.a a static library
src/linux/libinjector.so a shared library
cmd/injector a command line program linked with the static library

Windows

Open a Visual Studio command prompt and run the following commands:

$ git clone https://github.com/kubo/injector.git # Or use any other tool
$ cd injector
$ nmake -f Makefile.win32

The nmake command creates:

filename -
src/windows/injector-static.lib a static library (release build)
src/windows/injector.dll a shared library (release build)
src/windows/injector.lib an import library for injector.dll
src/windows/injectord-static.lib a static library (debug build)
src/windows/injectord.dll a shared library (debug build)
src/windows/injectord.lib an import library for injectord.dll
cmd/injector.exe a command line program linked the static library (release build)

Usage

C API

#include <injector.h>

...

    injector_t *injector;

    /* attach to a process whose process id is 1234. */
    if (injector_attach(&injector, 1234) != 0) {
        printf("ATTACH ERROR: %s\n", injector_error());
        return;
    }
    /* inject a shared library into the process. */
    if (injector_inject(injector, "/path/to/shared/library") != 0) {
        printf("INJECT ERROR: %s\n", injector_error());
    }
    /* inject another shared library. */
    if (injector_inject(injector, "/path/to/another/shared/library") != 0) {
        printf("INJECT ERROR: %s\n", injector_error());
    }
    /* cleanup */
    injector_detach(injector);

Command line program

See Usage section and Sample section in linux-inject and substitute inject with injector in the page.

Tested Architectures

Linux

injector process \ target process x86_64 i386 x32(*1)
x86_64 success success success
i386 failure(*2) success failure(*3)
x32(*1) failure(*2) success failure(*3)
injector process \ target process arm64 armhf armel
arm64 success success success
armhf failure(*2) success success
armel failure(*2) success success

*1: x32 ABI
*2: failure with 64-bit target process isn't supported by 32-bit process.
*3: failure with x32-ABI target process is supported only by x86_64.

Windows

injector process \ target process x64 32-bit
x64 success success
32-bit failure(*1) success

*1: failure with 64-bit target process isn't supported by 32-bit process.

Caveats

Caveat about ptrace() is same with linux-inject.

__libc_dlopen_mode internally calls malloc() and free(). If the target process is allocating or freeing memory and malloc() or free() holds a lock, this may stop the process forever. Same caveat is in linux-inject also.

License

Files under include and src are licensed under LGPL 2.1 or later.
Files under cmd are licensed under GPL 2 or later.
Files under util are licensed under 2-clause BSD.

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