vmp-lazy-unpack

An emulation-based unpacker and import resolver for Windows (x64, x32) VMProtect 3.x binaries.

The project started as a script used to unpack VMProtect 3 in our devirtualization pipeline. It does this without the need to attach a debugger or dump live.

How

The project uses Unicorn to emulate syscalls used by VMProtect's unpacker and import resolver.

• The project ships with a catalog of Windows dll exports pinned to a specific Windows build.
• The binary is mapped with a simulated Windows process.
• Emulation starts at the entry point, handling api and syscalls while tracking restored code and resolved imports.
• We stop emulation when execution enters restored code.
• The IAT is rebuilt from collected meta, recognized import stubs are patched, exception tables are fixed.
• The unpacked, emulated process is then dumped from memory to disk.

Installation

py -m pip install -e .

For decent speeds its recommended to install Microsoft C++ Build Tools so the C helper is used. If not installed the unpacking falls back to purely python based hooks (slower).

Usage

For normal unpacking + import fixups run:

py -m unpack "C:\path\file.exe"

For 32bit use:

py -m unpack "C:\path\file.exe" --32bit

To fix imports on an already unpacked bin:

py -m unpack "C:\path\file.bin" --imports_only

Limitations

• Only supports Windows x86. Tested against VMProtect 3.4, 3.9, 3.10, and 3.11.
• This will not devirtualize code.
• This will not resolve external calls inside virtualized functions automatically. These recovered imports are included in IAT for later lifting.

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