postject

Easily inject arbitrary read-only resources into executable formats (Mach-O, PE, ELF) and use it at runtime.

Building

Windows

You'll need CMake and Ninja to build LIEF.

$ cd vendor\lief
$ python3 ./setup.py --ninja build_ext -b ..\..\dist\lief

macOS / Linux

$ sudo make install-deps
$ make lief

Usage

$ ./postject.py --macho-segment-name __ELECTRON /Users/dsanders/electron/src/out/Testing/Electron.app/Contents/Frameworks/Electron\ Framework.framework/Electron\ Framework app_asar /Users/dsanders/test.asar

Testing

$ make check

Design

To ensure maximum capatibility and head off unforeseen issues, the implementation for each format tries to use that format's standard practices for embedding binary data. As such, it should be possible to embed the binary data at build-time as well. The CLI provides the ability to inject the resources into pre-built executables, with the goal that the end result should be as close as possible to what is obtained by embedding them at build-time.

Windows

For PE executables, the resources are added into the .rsrc section, with the RT_RCDATA (raw data) type.

The build-time equivalent is adding the binary data as a resource in the usual manner, such as the Resource Compiler, and marking it as RT_RCDATA.

The run-time lookup uses the FindResource and LoadResource APIs.

macOS

For Mach-O executables, the resources are added as sections inside a new segment.

The build-time equivalent of embedding binary data with this approach uses a linker flag: -sectcreate,__FOO,__foo,content.txt

The run-time lookup uses APIs from <mach-o/getsect.h>.

Linux

For ELF executables, the resources are added as notes.

The build-time equivalent is to use a linker script.