Now I get it… Updating Mac firmware


Perusing Allister Banks’ look into Thunderstrike vulnerability it didn’t quite click for me at first what I was looking at.

The condensed version that I finally was able to tease out was that you can get yourself into a situation where you:

  1. Have some machines with old, unpatched firmware
  2. You build an image with AutoDmg or some other method to upgrade those machines (in our case, we went from 10.9.5 to 10.10.4 during the summer vacation)
  3. The machine retains the old, unpatched firmware.

The reason for this is that the FirmwareUpdate part of the combo updater isn’t included in the images built by AutoDMG. If you instead update through the App Store/SUS, part of the update process includes patching the firmware.

Upon delivering the next point update, the firmware would probably get updated. Probably.

In terms of Thunderstrike vulnerability, you only need to have a newer firmware version than as detected in this extension attribute.

So the final word is, if you’re imaging machines with out-of-date firmware, and you care about the firmware being up-to-date, AND you don’t have pending point updates to apply, you can go grab the FirmwareUpdate.pkg package from the most recent OS X combo updater in your SUS and install it on the affected machines.

You can find this update by looking in your SUS, which is of course Reposado…

    find /path/to/reposado -name "OSXUpdCombo*"

…will give you the paths to whatever OS X combo updaters you still have kicking around. Within (probably the newest one) you’ll find the FirmwareUpdate.pkg you seek.

For example, the 10.10.4 one is here: /reposado/html/content/downloads/02/26/031-25777/01sza4ly2cuww3yxfpsbeov51p5n3v7l87/FirmwareUpdate.pkg

The package safely does nothing if a machine is already up-to-date, or if the package is actually too old, so there’s no harm in a speculative or better-safe-than-sorry run (or two).

Hopefully this is an infrequent circumstance. And you could find yourself in a circumstance where a firmware that ships with a machine is newer than the most recent OS X update contains. That firmware will probably be a part of the next update, but you might not want to wait.