Injector

Library for injecting a shared library into a Linux, Windows and MacOS process

[!CAUTION]
Due to a shift in my personal interests, this repository is no longer maintained and has been archived. If you're looking for a successor project, please check the network graph to see if any forks have continued development.

Linux

[!WARNING]
Don't use this in production environments. It may stop target processes forever. See Caveats.

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 4 ~ 16 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.

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 x64 processes by checking the export entries in 32-bit kernel32.dll.

Note: It may work on Windows on ARM though I have not tested it because I have no ARM machines. Let me know if it really works.

MacOS

The injector connects to the target process using task_for_pid and creates a mach-thread. If dlopen is called in this thread, the target process will fail with an error, however, it is possible to create another thread using pthread_create_from_mach_thread function for Mac >= 10.12 or pthread_create otherwise. In the created thread, the code for loading the library is executed. The second thread is created when injector_inject is called and terminated when injector_detach is called.

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 (MSVC)

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)|

Windows (mingw-w64)

On MSYS2:

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

Cross-compilation on Linux:

$ git clone https://github.com/kubo/injector.git
$ cd injector
$ CC=x86_64-w64-mingw32-gcc OS=Windows_NT make

The environment variable OS=Windows_NT must be set on Linux.

MacOS

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

The make command creates:

| filename | - | |---|---| |src/macos/libinjector.a |a static library| |src/macos/libinjector.dylib |a shared library| |cmd/injector |a command line program linked with the static library|

Important: in order for the injector process to connect to another process using task_for_pid, it is necessary to [disable SIP][] or sign the injector with a self-signed certificate with debugging permission, for this:

$ cd cmd/macos-sign
$ chmod +x genkey.sh
$ ./genkey.sh
$ chmod +x sign.sh
$ ./sign.sh

If injector still does not work after signing, reboot the system.

Usage

C API

#include <injector.h>

...

    injector_t *injector;
    void *handle;

    /* 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", NULL) != 0) {
        printf("INJECT ERROR: %s\n", injector_error());
    }
    /* inject another shared library. */
    if (injector_inject(injector, "/path/to/another/shared/library", &handle) != 0) {
        printf("INJECT ERROR: %s\n", injector_error());
    }

...

    /* uninject the second shared library. */
    if (injector_uninject(injector, handle) != 0) {
        printf("UNINJECT ERROR: %s\n", injector_error());
    }

    /* cleanup */
    injector_detach(injector);

Command line program

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

Tested Architectures

Linux

x86_64:

injector process \ target process | x86_64 | i386 | x32(*1) ---|---|---|--- x86_64 | :smiley: success(*2) | :smiley: success(*3) | :smiley: success(*6) i386 | :skull: failure(*4) | :smiley: success(*3) | :skull: failure(*5) x32(*1) | :skull: failure(*4) | :smiley: success(*6) | :skull: failure(*5)

*1: x32 ABI
*2: tested on github actions with both glibc and musl.
*3: tested on github actions with glibc.
*4: failure with 64-bit target process isn't supported by 32-bit process.
*5: failure with x32-ABI target process is supported only by x86_64.
*6: tested on a local machine. CONFIG_X86_X32 isn't enabled in github actions.

ARM:

injector process \ target process | arm64 | armhf | armel ---|---|---|--- arm64 | :smiley: success | :smiley: success | :smiley: success armhf | :skull: failure(*1) | :smiley: success | :smiley: success armel | :skull: failure(*1) | :smiley: success | :smiley: success

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

MIPS:

injector process \ target process | mips64el | mipsel (n32) | mipsel (o32) ---|---|---|--- mips64el | :smiley: success (*1) | :smiley: success (*1) | :smiley: success (*1) mipsel (n32) | :skull: failure(*2) | :smiley: success (*1) | :smiley: success (*1) mipsel (o32) | :skull: failure(*2) | :smiley: success (*1) | :smiley: success (*1)

*1: tested on debian 11 mips64el on QEMU.
*2: failure with 64-bit target process isn't supported by 32-bit process.

PowerPC:

• ppc64le (tested on alpine 3.16.2 ppc64le on QEMU)
• powerpc (big endian) (tested on ubuntu 16.04 powerpc on QEMU

RISC-V:

• riscv64 (tested on Ubuntu 22.04.1 riscv64 on QEMU)

Windows

Windows x64:

injector process \ target process | x64 | x86 ---|---|--- x64 | :smiley: success(*2) | :smiley: success(*2) x86 | :skull: failure(*1) | :smiley: success(*2)

*1: failure with x64 target process isn't supported by x86 process.
*2: tested on github actions

Windows 11 on Arm:

injector process \ target process | arm64 | arm64ec | x64 | x86 | arm32 ---|---|---|---|---|--- arm64 | :smiley: success | :skull: failure | :skull: failure | :skull: failure | :smiley: success arm64ec | :skull: failure | :smiley: success | :smiley: success | :skull: failure | :skull: failure x64 | :skull: failure | :smiley: success | :smiley: success | :skull: failure | :skull: failure x86 | :skull: failure | :skull: failure | :skull: failure | :smiley: success | :skull: failure arm32 | :skull: failure | :skull: failure | :skull: failure | :skull: failure | :smiley: success

Wine (on Linux x86_64):

injector process \ target process | x64 | x86 ---|---|--- x64 | :smiley: success | :skull: failure x86 | :skull: failure | :smiley: success

MacOS

injector process \ target process | x64 | arm64 ---|---|--- x64 | :smiley: success(*1) | :skull: failure(*2) arm64 | :skull: failure(*3) | :smiley: success

*1: failure with x86_64 target process isn't supported by x86_64 process on ARM64 machine. Tested on github actions.
*2: failure with arm64 target process isn't supported by x86_64 process.
*3: failure with x86_64 target process isn't supported by arm64 process.

Caveats

The following restrictions are only on Linux.

Injector doesn't work where ptrace() is disallowed.

• Non-children processes (See [Caveat about ptrace()][])
• Docker containers on docker version < 19.03 or linux kernel version < 4.8. You need to pass --cap-add=SYS_PTRACE to docker run to allow it in the environments.
• Linux inside of UserLAnd (Android App) (See here)

Injector calls functions inside of a target process interr