NAC is Not A Container for macOS

NAC provides a lightweight virtual environment for macOS with container-like user experience.

NAC does not need the root privilege and does not conflict with System Integrity Protection (SIP).

Note that NAC is Not A Container; NAC does not provide a secure isolation in any way. In this sense, NAC is akin to Python's venv rather than Docker.

Installation

make
sudo make install

Usage

The command below virtually mounts $HOME/usr_local into /usr/local:

nac run -it --rm -v $HOME/usr_local:/usr/local host bash

The syntax of nac run is similar to docker run, but nac run does not support "images" yet.

[!WARNING]

Some applications (such as Homebrew) may not recognize the virtual mounts.

Be cautious, especially when removing or overwriting a file on a virtual mount. It may potentially result in removing or or overwriting a file on the real filesystem.

[!NOTE]

GUI applications do not work (yet).

How it works

NAC copies a command binary into a temporary directory and attaches the com.apple.security.cs.allow-dyld-environment-variables entitlement to it so that dylib calls for libc can be intercepted with DYLD_INSERT_LIBRARIES.

Non-dylib calls, such as a direct invocation of the svc (ARM) / syscall (Intel) instructions, are not intercepted.

Future work

• Support running multiple Homebrew instances with isolated /opt/homebrew
• Build a fork of /usr/lib/system/libsystem_kernel.dylib, and inject it via DYLD_LIBRARY_PATH.
  This is expected to be more robust and will need less amount of hooks.
  However, it seems very hard to compile libsystem_kernel.dylib from
  the source.