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Mac App Store | Security Generation
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Posts tagged ‘Mac App Store’

8
Jul

Mac OS X “Lion” and the Dangers of Restoring from a Partition

With the release of Mac OS X 10.7 “Lion”, Apple is changing the way we’ll be doing system upgrades. Lion will only be available to Snow Leopard users electronically through the Mac App Store, and thus it will no longer be possible to purchase a physical install DVD. Before I go into the intended topic of this post, allow me to <rant> about how I’m not too keen on this decision. As a result, it’s no longer possible to install OSX on Macs that don’t have an internet connection (yes, these do exist!). Even for those who do, many don’t have very fast internet connections, or may have extremely low usage caps. I know that UK internet providers still offer entry-level packages 5Mbit lines and stupidly low 1-5 GB monthly limits. Lion is likely to be about 4GBs in size. Oh, you want to install OSX on more than one Mac? Suuure, just download the 4GB install package on each Mac.</rant> You get the point…

The real thing I wanted to talk about is Apple’s solution to system re-installation or recovery, and specifically the security implications thereof. Installing Lion will cause it to create a small ‘recovery’ partition on your primary drive, which is essentially a partition equivalent of an install DVD. If you have a problem with your main OSX partition, and need to run repair utilities or reinstall, you just boot from the recovery partition. Sounds really useful actually, as you don’t need to worry about having a DVD handy. But where this solution brings ease-of-use and convenience, it also brings some security risks.

Although Mac OS X is still largely unaffected by malware, the winds of change are indeed upon us, and it’s unrealistic to assume the Mac will remain virus-free forever. As viruses get more complex they find ever-improving ways of making themselves persistent on a system. There are countless examples of Master Boot Record viruses on Windows where the only sure-fire solution is to completely wipe the hard drive and reinstall from CD/DVD. Because once your system is infected, good security practice forces you to assume that any file or executable is compromised. So, how does this affect a bootable recovery partition? If I were a virus writer, I’d make pretty darn sure that I infect a core installer file on the recovery partition so that any  installation will have my virus. The nice thing about DVDs is that even if you insert them into an infected computer, they can’t be changed, and so you have complete confidence (barring a very advanced/rare firmware virus) that wiping and reinstalling from DVD yields a fresh and clean install of your system. As a security professional, I don’t think I’ll be able to trust a recovery partition like that.

But wait, there’s more. Viruses are a concern, but if you’re a smart user they’re not really a problem. We can run anti-virus, disable Flash, Java and Javascript, etc, and as long as you browse safely and don’t open random executables you’ll be perfectly fine. What about an attacker with remote or physical access to your computer? If I remotely hack into someone’s Mac, either due to a vulnerability or a weak password, all I have to do is modify a few files in the existing system and the recovery partition, and boom, persistent back door! The user can reinstall OSX all they want… my back door will simply be reinstalled with it.

But wait, there’s more. Even if your computer is completely secure from remote attacks, the same goes for someone with physical access to your Mac. Now, as a disclaimer, I have to point out that anytime an attacker gets physical access to any computer it’s game over. Even if you use FileVault, I may not be able to log in to your computer (unless some kind of cold boot attack is still possible), but I can easily boot your computer from a USB stick (or remove your hard drive if you have a Firmware password), trojan your recovery partition and corrupt your primary boot partition (similar to an Evil Maid attack). What are you going to do? Reinstall Mac OS X from my trojaned recovery partition of course! It’s not like you have a choice.

Any system compromise can lead to the installation of a persistent backdoor for the lifetime of the recovery partition on that hard drive. I don’t want to sound overly critical; I am probably one of the most fervent Apple supporters you’ll ever meet (with good reasons too), but not to the extent it stops me from thinking about potential impacts. I appreciate that Apple is trying to make things easier for Joe User. Being able to download updates electronically is awesome, and I honestly believe many would take advantage of that (myself included), but users should be given the choice. Particularly in situations like this where not having a physical install medium can have an impact on both usability and security.

My guess (or maybe hope) is that if Apple is not going to sell install DVDs itself, we may be allowed to burn our own install DVDs after downloading Lion from the Mac App Store. Either way, it is fairly trivial to burn the Lion installer onto a DVD – but users shouldn’t have to (or sometimes can’t) resort to a hack like that. Take heed, Apple.

[Update 21/07/11] Ok, so Apple isn’t going to allow users to burn their own DVDs, but they have confirmed that Lion will be available on a mini USB drive in August (for $69).

7
Jun

Find My iPhone Brings Improved Offline Device Support

Apple has released an update to their free Find My iPhone offering, which greatly improves the support for tracking devices that are offline at the time. Note that this doesn’t mean you can track an iPhone or iPad that is turned off, or out of signal range (not possible). Instead, if a device is offline when you try to locate it, Apple will later send you an email with its location the next time that device gets back online. Thanks to this, it’s no longer necessary to constantly be checking the Find My iPhone app/webpage. Here is Apple’s summary of the changes:

  • When you are unable to locate a device because it is offline, you will receive an email if the device comes online and is located.
  • Ability to remove an offline device from the list using the app.

Note, it appears this updated feature is only available using the Find My iPhone app (version 1.2) available in the App Store – it is not yet available in the MobileMe web interface. I assume it won’t be updated until the new iCloud Find My iPhone web interface is launched. [Update: I was right.]

For more information on how to use this great free service to recover your iOS devices, check out Protecting and Recovering Your iPhone and iPad from Loss and Theft.

8
Jan

Mac App Store Simple Copy Protection Security Bypassed

The Mac App Store was released in the recent 10.6.6 update, allowing Mac users to buy and install apps in the same, easy, one-click fashion as iPhone and iPod Touch users. Over 1 million apps were downloaded in the first 24 hours. Although the Mac App Store doesn’t make use of a sandbox like the iOS App Store does, there are still several mechanisms developers can use to prevent their software from being copied and shared between different users.

Hackers have discovered that one of the simpler methods used to authenticate an app is actually stored as a separate plist file within the application bundle. This means that an app can be copied, and the authentication files within its bundle can be replaced with those from an app that was legally purchased (even if it’s a free app).

In order to resolve this, developers should not rely solely on the data found within the plist file external to the binary, and perform some checks against hard-coded values within the binary itself. Some simple tips are available here. Ultimately all software is crackable, Mac App Store or not, so my suggestion to application developers is: spend more time developing great new features, and less time worrying about anti-piracy. This is what itself Apple does. In the long run most people will follow the simplicity route and buy the app.

In related news: How not to store passwords in iOS (developers take heed)

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