AndroidNativeEmu

Allows you to partly emulate an Android native library.

This is an educational project to learn more about the ELF file format and Unicorn.

Features

• Emulation of the JNI Invocation API so JNI_OnLoad can be called properly.
• Emulation of native memory for malloc / memcpy.
• Emulation of syscalls (SVC #0) instruction.
• Hooking through the symbol table.
• All JavaVM, JNIEnv and hooked functions are handled by python.
• Enable VFP support.

Usage

In the future this will be possible through pypi.

Make sure you are using python 3.7.

1. Clone the repository
2. Run pip install -r requirements.txt
3. Run python example.py

If you have trouble getting the keystone-engine dependency on Windows (as I did):

1. Clone their repository
2. Open a terminal in bindings/python
3. Run python setup.py install (Make sure you are using python 3.7)
4. Download their Windows - Core engine package here for your python arch.
5. Put the keystone.dll in C:\location_to_python\Lib\site-packages\keystone\.

TODO

• Improve file descriptors in vfs/file_system.py so they are re-useable.
• Add a way for the VirtualFileSystem to give back dynamic files, such as /proc/self/status, /proc/self/status but also /dev/urandom.
• Library consumers must be able to easily rebuild the needed Java classes for a native library, which are used by the native library through the JNIEnv.
  • Classes
  • Objects
  • Methods
  • Native methods
  • Fields
  • Types
  • Reflection

Dependencies

• Unicorn CPU emulator framework
• Keystone assembler framework

Resources

All resources used while developing AndroidNativeEmu.

Text sources

• https://greek0.net/elf.html
• https://stackoverflow.com/questions/13908276/loading-elf-file-in-c-in-user-space
• https://programtalk.com/python-examples/pyelftools.elftools.elf.relocation.Relocation/
• http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044f/IHI0044F_aaelf.pdf
• https://wiki.osdev.org/ELF_Tutorial
• https://docs.oracle.com/javase/7/docs/technotes/guides/jni/spec/functions.html
• https://android.googlesource.com/platform/dalvik/+/donut-release/vm/Jni.c

Code sources

• https://github.com/lunixbochs/usercorn
• https://github.com/slick1015/pad_unpacker (SVC 0 instruction)