Don’t fight Gatekeeper to install Office for Mac updates

Apple released OS X 10.8 (Mountain Lion) on Wednesday and with it released its new security technology called Gatekeeper. Gatekeeper’s purpose is to watch as you download applications and installers from the Internet and verify they are legitimate software not malware. That’s a good thing.

Most of Microsoft’s Office for Mac installers and updaters are not “signed”, which means Gatekeeper may not allow you to install them or at least may make them difficult to install. Rather than fighting Gatekeeper learn how to work with it so that you’re able to install important software and updates without compromising your Mac’s security.

What is Gatekeeper?

Gatekeeper’s settings are located under Apple menu –> System Preferences… –> Security & Privacy –> General tab.

Gatekeeper settings

Apple has preset Gatekeeper to allow installing applications from Mac App Store and identified developers. For the vast majority of Mac users this setting is perfect.

Apple requires developers to “sign” their applications that they distribute through the Mac App Store. Signing simply means that someone (in this case Apple) has verified the authenticity of the developer. Should the developer begin doing something malicious with its software such as including spyware then Apple can revoke the developer’s signing certificate and disable it.

Mountain Lion users can tell that an installer is signed simply by double-clicking it. If they receive no warnings and see the installer window they’ll also notice a tiny lock in the upper right corner. Clicking that lock will reveal the signing certificate that tells Gatekeeper the software is legitimate.

Installer and Certificate

Gatekeeper in action

What do we see when Gatekeeper is doing its job? Trying to install the Microsoft Office 2011 14.2.3 Update, which hasn’t been signed by Microsoft, will present this message:

“Office 2011 14.2.3 Update.pkg” can’t be opened because it is from an unidentified developer.
Your security preferences allow installation of only apps from the Mac App Store and identified developers.

Gatekeeper in Action

Note that the only option is to click the OK button. We aren’t, however, without options.

Installing Office updates without lowering Gatekeeper’s security

Gatekeeper’s security settings offer an Anywhere option that would effectively turn off Gatekeeper and allow all software be installed without verification.

Don’t do that!

We have at least three options to run unsigned Microsoft installers and updaters without lowering Gatekeeper’s security setting.

  1. The easiest means to install an update is to launch any Microsoft Office for Mac application and select Check for Updates from the Help menu. The Microsoft AutoUpdater application can download and install updates directly from Microsoft without interference from Gatekeeper.Check for Updates
  2. If you’ve manually downloaded an Office for Mac update then don’t double-click it to run it. Instead, right-click or Control-click it and select Open from the contextual menu that appears.Right-click or Control-click and select Open

    This will exempt the installer from Gatekeeper’s security and allow you to open it. Click the Open button to run the installer.

    Exempt

  3. Enterprise administrators who deploy Office for Mac updates to multiple machines will more than likely use Apple’s command line installer tool. So long as the Apple installer package has no signing certificate then installer will ignore Gatekeeper’s settings. (This may change in a future update for security reasons.) To install the Office for Mac 2011 14.2.3 Updatepackage via command line run this:

These workarounds aren’t necessarily specific to Office for Mac. Most any in-application updater mechanism will probably work without interference from Gatekeeper and both the contextual menu Open command and installer command line utility will install any Apple installer package file.

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