debugging privileged helper

Three things:

• Add comprehensive logging (using

  os.log

  ) to your privileged helper. This will help you debug problems that show up in the field.

• For initial bring up, structure your privileged helper code so that you can debug it in a non-privileged context. There’s two parts to this:

  • Add an internal API your code so that you can test your core code using a standard testing harness (like XCTest).

  • Add command-line options to your tool so that you can debug it directly in Xcode. For example, let’s say your privileged helper tool exists to update a file in a privileged directory. Add a command-line option to override the location of that file so that, during debugging, you can point it to a location that’s not privileged.

• Once you’ve done the above, you have a lot less debugging to do because you only have to deal with issues that show up when the code is run in the privileged environment. To debug those problems:

  1. Modify your

     launchd

     property list to set

     WaitForDebugger

     . See

     launchd.plist

     man page for details.

  2. Once the tool is paused this way, attach using Debug > Attach to Process by PID or Name, setting Debug Process As to “root”.

  3. You can now set breakpoints and continue execution.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"