PureDarwin / XPC

XPC and Friends (libxpc, launchd and soon xpc.framework)

XPC and Friends!

An open-source reimplementation of Apple's XPC library and launchd for PureDarwin. Based on launchd 842.91.1 and iXsystems's skeleton re-implementation of libxpc.

NOTE: The code in this repo compiles and runs but is currently untested. In particular, the implementation of xpc is incomplete, with several functions being no-ops.

This project differs from a 'pure' launchd built from Apple's source to align better with what can be inferred of the current (macOS 10.13) implementation:

• liblaunch.dylib contains no code. Instead it acts as a proxy to libxpc.dylib by way of indirect symbols.
• libxpc.dylib contains the bulk of the logic that was in liblaunch.dylib, along with the untested / non-existant XPC code.
• launchd is mostly unchanged, although audit logging is currently disabled.
• launchctl has had a couple of code paths commented-out so that it builds.
• A launch daemon script is included to launch bash at startup.

Prerequisites

You will need a version of libSystem which links to libxpc, like this one. You will also need a version of libcoreservices, which it requires. You can find one here.

You will also need a versions of libedit and libbsm.

Installation

A binary root will be made availble once the code has been shown to work to at least minimum standards.

Install the binaries into a Darwin image in the following locations:

• libxpc.dylib and liblaunch.dylib into /usr/lib/system.
• launchd into /sbin, but please read the discussion below first, you'll probably need to rename it to pdlaunchd.
• launchctl into /bin.
• Copy org.puredarwin.console.plist into /System/Library/LaunchDaemons/.
• Install a version of libSystem which links to liblaunch and libxpc.
• Install a version of libsystem_coreservices if one isn't already present.
• Install versions of libedit and libbsm if they aren't already available.

Once you have done this, check the ownership of all directories up to the LaunchDaemons directory and all files inside it. They need to be root:wheel for launchd to be happy about launching them. Please note that if chown/chmod has no effect, you may need to run diskutil enableOwnership on the mounted volume first.

launchd should run as the first user task (pid 1) in order to set up certain important services (such as the mach port nameserver) which child tasks inherit. When the kernel finishes booting the system it automatically runs /sbin/launchd. In current PureDarwin systems this file is a script which sets up various system parameters and then runs /bin/bash. To work with this, you should rename launchd to pdlaunchd and then replace

/bin/bash -i

in the launchd script with

exec /sbin/pdlaunchd

The exec part is important. This will allow launchd to replace the startup script as pid 1. launchd will then in turn launch launchctl to bootstrap the system. If you have installed the org.puredarwin.console.plist then a bash shell will be started.

TODO

• Complete implementation of these xpc functions: XPC_ERROR_CONNECTION_INTERRUPTED; XPC_CONNECTION_MACH_SERVICE_LISTENER; XPC_CONNECTION_MACH_SERVICE_PRIVILEGED; XPC_ERROR_CONNECTION_INVALID
• Get audit logging working using recent OpenBSM