Seattle-based law firm Pfau Cochran Vertetis Amala (PCVA) today followed through with plans to bring a class action lawsuit against Apple over the "Error 53" controversy that made headlines last week.
"Error 53" is the error code that some iPhone 6 owners have received after third-party repairs that affect Touch ID were made to their iPhones, rendering the devices unusable. As explained by iFixit, repairs made by third-party services using components not sourced from the original device cause the iPhone to fail a Touch ID validation check because the mismatched parts are unable to properly sync. Parts that can impact Touch ID include the screen, flex cable, and Home button.
When this Touch ID validation check fails during an iOS update or restore, Apple disables the iPhone, effectively "bricking" it in an effort to protect Touch ID and the related Secure Enclave that stores customer fingerprint information. Apple says that without the validation check, a malicious Touch ID sensor could be used to gain access to the Secure Enclave.
PCVA attorney Darrell Cochran, who is leading the Error 53 lawsuit, claims that Apple's security argument is invalid because affected iPhones often work fine for several months following repairs as the validation check only occurs when downloading a new version of iOS. He also cites Apple's failure to give a warning about the consequence of an update as an issue that will be featured in the lawsuit.
"No materials we've seen from Apple ever show a disclosure that your phone would self-destruct if you download new software onto a phone," Cochran said. "If Apple wants to kill your phone under any set of circumstances and for any reason, it has to make it crystal clear to its customers before the damage is done."
Compounding the problem, according to Cochran, is how disagreeable Apple's reaction to the problem has been. "The error code 53 signals the death of the phone, and Apple's response has been to say 'you have no options; it's not covered under warranty, and you have to buy a new phone.'"
PCVA is aiming to get affected iPhone customers new, working devices to "provide immediate relief" to consumers. It is also seeking upwards of $5 million in damages and an update to eliminate the repair restrictions. PCVA is asking customers who have been impacted by Error 53 to get in touch.
Aside from explaining the reasoning behind the Error 53 message and its consequences, Apple has remained quiet about the controversy. MacRumors has, however, heard from a retail source that certain Apple Stores have received the go ahead from Apple to replace third-party screens and other components to resolve the issue. It is not yet clear if this replacement policy will be extended to all Apple Stores or if Apple will make an official comment on the situation.
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The API hides a lot of the implementation details, so most developers won't know how it really works, but Apple document it in their iOS Security Guide (PDF) ('https://www.apple.com/business/docs/iOS_Security_Guide.pdf').
When you boot your iPhone up, the filesystem is encrypted. It's just full of meaningless junk; you can't use the phone. Once you enter your passcode for the first time, the system reads the filesystem key (which itself is stored encrypted by your passcode), and tries to decrypt it. If your passcode is correct, it will end up with the correct filesystem key, and it can unlock your iPhone's hard drive and read useful data from it. This filesystem key is called "NSFileProtectionComplete".
IMPORTANT: At this point your phone is unlocked. That is all there is to it. This filesystem key gets placed in the Secure Enclave so your iPhone can read/write from its hard drive. We haven't used TouchID or fingerprints so far, just a passcode. This is why you always need to give your passcode after a restart.
So how does TouchID work, exactly?
Let's look at what happens when you lock the phone, and how it's different between TouchID and non-TouchID:
So basically if you have TouchID disabled (passcode only), this key gets thrown away and you need to enter the passcode again next time you unlock. It's the exact same process as you go through on first-boot.
What Apple is saying here is that TouchID just holds on to the key which you already obtained via your passcode for a while (48 hours if the device stays on). But is TouchID really completely optional? Let's ask Apple:
Okay, I guess that settles it.
What about other stuff like iTunes/ApplePay purchases? How does that work with TouchID?
So when you enter your iTunes Store password the first time after a reboot, your device gets a temporary token to use for purchases, stores it in the Secure Enclave, and guards it behind TouchID. Again, it's totally optional; just a shortcut for entering your password.
The same applies to Apple Pay:
Man, Apple is really going to regret writing this document...
So yeah, in conclusion:
1. it is totally technically possible to rip the TouchID sensor out of your phone and still be able to unlock it (assuming you have the passcode).
2. TouchID does not seem to be essential for any single feature of the device; it is only ever a shortcut for entering the passwords you have already recently entered in to the phone.
3. It's really weird that Apple only check the TouchID sensor's integrity when they update the OS. Surely they should check that on every boot?
So what did Apple do wrong?
1. Apple should have communicated better (not when performing the update, but when buying the device!) that the TouchID sensor can only be replaced by an authorised technician.
2. If the TouchID sensor is compromised, they should fall-back to the passcode. As I said, the passcode is the only thing you really need to unlock the device.
Law firms? I just did all of your investigation work for you. Feel free to cut me a cheque.
EDIT: Rewritten for greater clarity for non-technical folks.
EDIT2: My personal feeling is that this is a bug -- I mean, what if the legit sensor developed a hardware fault? You don't want the machine to just lock all access. I think Apple did intend to fall-back to the passcode if the TouchID sensor, but unfortunately this is a catastrophic bug: even if Apple fix it, once you're locked out of the phone you can't update to get the fix. They should release a software update ASAP and repair any affected phones for free.
There is a lot of misinformation on this subject. The "brick" happens when someone replaces the TouchID sensor--with a GENUINE OR 3rd party part. Apple is most likely within their right to disable TouchID when they detect a mismatched sensor as it's a security risk. However bricking the device and not giving any warning is probably going too far.
But on the other hand, Availability is a part of the CIA triad so bricking the phone does violate this premise.
However, Apple is doing this because a piece of hardware inserted between the Touch-ID Sensor and the Secure Enclave could in theory either intercept scans or access the enclave.
They are doing this to protect you, not as a "screw you for trying to fix your own phone." People will always see what they want to see though, I suppose.