I’m fascinated that they aren’t requiring an entitlement for all usage of setting & posting notifications through this API. A way to share 64 bits of information (at a time) to any process on the device? That is right in the wheelhouse of tracking a user across apps.
I don’t specifically know the types of things that you’d want to share across apps, but there’s a long history of cross process information channels being removed or restricted.
If the system is storing values for you, and isn’t keeping track of which app they came from, now you’ve got persistent storage across app deletion & re-install, as long as there isn’t a reboot in between.
I think you could easily use it to work around IDFA or IDFV resets, as a simple example.
> That is right in the wheelhouse of tracking a user across apps.
The design is old. It probably predates facebook, so it's not been intentional, as your comment might be interpreted. But it certainly seems ripe for abuse. I'm curious if it would actually be used for that, because any app that can access internet already has a better way to share information.
this is exactly where my mind went immediately - 64 bits is more than enough for easy (1 line!) unenforced cross-app tracking of a user for advertising purposes, basically a super cookie for iOS. If they now require an entitlement for this API it's a privacy win
The IDFV already supports tracking user across apps, as long as they are from the same vendor. It resets when apps from a vendor are removed from a device. Not sure if the user can reset it by themselves, but the vendor could then always tie things together using another self-generated identifier stored on the device, as long as any of its apps are on it, which boils down to the same.
I think the approach you describe allows roughly the same, except perhaps doing so without (or with different) permissions, and allowing to do this between vendors (that must agree upon this upfront).
I think it’s most interesting for 3rd party SDKs (analytics, advertising, others?), because they’re in a position to have their code running in apps from different vendors.
As per the DMA if it's available to Apple's own apps it has to be available to third party apps as well. Of course apple will fight this tooth and nail so they can maintain their walled garden, making them billions per year.
The exploit as described doesn't "brick" the device; that would require permanently disabling it. A tethered restore would be all that's required to recover in this case.
There's physically no way to permanently "brick" an iPhone.
DFU mode boots entirely from read-only ROM, and from there, you can just restore everything via USB cable.
Same applies to Apple Silicon Macs. You can damage the system, recovery and emergency recovery volumes, but even then, you can still boot into DFU from ROM and re-initialize everything via another Mac.
This is in contrast to some PCs, where if you damage the BIOS (e.g. by suddenly losing power during a firmware update), your device may or may not be bricked. There have even been stories of peoples' computers being bricked via rm -rf /, due to removing everything at /sys/firmware/efi/efivars/ (which is actually stored inside the motherboard), and sometimes contains things that the motherboard won't boot without
> There's physically no way to permanently "brick" an iPhone.
There definitely are (If you count jailbroken iPhones). I've managed to brick one by removing all thermal throttling limits and subsequently damaging the motherboard with the world's shittiest watercooling setup.
Can't use DFU to restore if you've got damaged hardware
"physically" is overstating it. Certainly during development it's possible, which means that -- conditioned on a bad enough bug -- it could hypothetically happen to customers too. Not that I think that's likely, of course, but it is physically possible.
I'm gonna walk through this because I have a bit of experience here on the computer side of things, but I'm not really making an excuse for the fact that the PC version of this is less user-friendly; from my perspective, I fully respect that Apple has done a good job with user experience where PC manufacturers have lagged. However, my main concern is devices turning to e-waste, so the important thing for that isn't UX, it's just how plausible it is to recover once you've bricked. With that out of the way...
> This is in contrast to some PCs, where if you damage the BIOS (e.g. by suddenly losing power during a firmware update), your device may or may not be bricked.
I accidentally destroyed the firmware on a machine that did not have any recovery features, when flashing modified UEFI images, leaving it mostly inoperable. I wound up recovering it using flashrom and a Raspberry Pi. I think this counts as a hard brick, but the modular nature of PCs (e.g. most BIOS chips are on sockets so you can pull them out easily) it's not nearly as big of an issue if you hard-bricked a device that's more integrated and locked down. It's not instant e-waste because no bricks are permanent.
(It's a little harder for laptops, but I did also flashrom a laptop in a similar fashion, in-circuit using a SOIC8 clamp. This was not a brick recovery but rather messing with coreboot.)
Definitely not as much for the faint of heart, but a repair technician could do it for you. Alternatively, for PCs with socketed BIOS, you can buy a new EEPROM that's already flashed with the right firmware--they were readily available on eBay last I looked.
That was probably a decade ago or more by now. Many modern PC motherboards from many vendors have mitigations for this; it was a common enough pain point after all. For example, my desktop PC has an embedded controller that can boot and rewrite the flash chip for you, using a copy of BIOS from a USB stick. (Works even if the CPU isn't installed. Pretty cool.)
> There have even been stories of peoples' computers being bricked via rm -rf /, due to removing everything at /sys/firmware/efi/efivars/ (which is actually stored inside the motherboard), and sometimes contains things that the motherboard won't boot without
EFI vars are stored in NVRAM, not the EEPROM. You can usually clear that a couple of ways:
- Use an integrated NVRAM reset system. Some machines have a way to do this listed in their manual. On desktop PC motherboards, it tends to be a jumper you set for a few seconds. Sometimes you will have an easier option, like a button somewhere, or even possibly a key combination at boot (Long time Macintosh fans probably have memorized the NVRAM reset key chord for Apple computers... I wonder if it still works on Apple Silicon.)
- Remove the battery for a few seconds. Usually easily accessible on a desktop. Usually a little less easy to get to on a laptop, but nothing absurd, usually just some screws.
Certainly it could be easier to recover from, I'd say it's actually not very easy to brick a typical desktop PC in a particularly permanent fashion. The only time I've ever done it was because I was modifying my UEFI image intentionally. Screwing up EFI vars doesn't make most systems unbootable. I have corrupted my EFI vars quite a few times trying to do funny things. UEFI implementations do tend to be buggy, but not all of them are that catastrophically bad.
--
Now... as for whether or not an Apple Silicon device can "physically" be bricked by software, the most obvious way to do that would be to wear the SSD down to the point where it can no longer be rewritten. I think the M4 Mac Mini finally no longer solders these and that the Mac Minis do have a way you can recover from this brick (using another Mac to restore to a new SSD) but there are many Macs where if the SSD is destroyed, it's pretty hard to fix since you need Apple tools that are hard to obtain if you want to pair a new SSD. This is unfortunate because Apple has often had dodgy hardware choices around the SSD (e.g. the notorious TPS62180 buck converter) and doesn't always use SSDs that have the best reliability (IIRC they use a lot of Kioxia in the newer Apple Silicon devices, which are not considered to be bad devices by any means, but are generally considered less durable than e.g. Samsung SSDs.)
Rather than have an Apple device become ewaste due to software issues, in recent years, it is much more likely that it will become ewaste due to hardware issues, as a result of parts pairing and having failure-prone components that are not modular even when they really can and should be (Good on them for rectifying this lately, e.g., with the Mac Mini SSD, but it's a bit sad that it took this long. And on the note of that SSD... Apple, you really could've used a standard electrical interface for that.)
This is somewhat a testament to Apple's software and system design, but it's simultaneously a condemnation of their recent track record with repair, too. Best we can hope is that they don't go backwards from this point forward, because they created a lot of devices that will become ewaste over time for almost no gain for anyone. (I strongly dislike but can understand the justification for something like parts pairing in iPhones and iPads, but much less so for similar sorts of mechanisms in computers.)
From observation, "brick" has evolved, as things do in language. In practice, it rarely means the traditional definition you refer to, but the softer one used here.
And for that reason I wouldn't hassle laymen over it but among the HN crowd I expect a bit more care. An "anything goes" attitude makes communication more difficult.
"Soft brick" is the correct term that already exists.
Also, although HN readers probably have many devices in their homes there are people out there who have only a phone and no computer. For them this would be pretty catastrophic. Hopefully they’d take their device to Apple or a third party technician
“Bricking” isn’t a rigorously defined term, it’s more like “realtime” in the sense that it comes with an implicit “(for this particular user in this particular scenario)”. For most users a device is bricked if it doesn’t turn on and work when you press the power button. For most readers here, using dev tools to re-flash a bootloader would be fairly easy but if USB stops working it might be game over. I’m sure there are a few around who could de-cap an ASIC and circuit bend it back to life.
Incorrect. Bricking means a device becomes a doorstop that cannot be resurrected or repaired by the user non-invasively. That's the whole point of the term.
Correct. The terminology is wrong. It's an annoying, repeated DoS that doesn't ruin the device permanently but could lose user data if it must be erased.
Neat, $17,500 is pretty good, I’m so used to these blog posts being for peanuts, or where companies fix the vulnerability but don’t pay out at all. Apple’s gotten better about this since 2019.
I read a comment under the story about the recent YouTube vulnerability where one could unmask the related Google account and its owner using the standard YouTube API (something similar to that anyway), and they explained a lot of lesser-known nuances in establishing values for bounties like these, and it helped explain a lot (not all) of the reasons for what might seem like low-ball/high-ball valuations on the surface. If I can find their comment I’ll post back, it was really insightful. That said, there are also plenty of examples of people just getting shafted.
Great work! This is my favourite type of vulnerability, simple, effective and brutal. Reminds me of a time two decades ago when with a friend from uni we theorised about a perfect server vulnerability where you’d exploit a machine by pinging it. And of course, two years ago it was in fact discovered as CVE-2022-23093.
It was actually almost 3 decades ago, making me feel extremely old - the period right at the end of '96 and into mid '97 when this was a popular way to cause mischief via IRC was truly a magical time
When I was in college circa 2001 we used to prank each other with the ping of death and other crash exploits. Also random IPs on the college network when we were bored. It was crazy how long it was around for and how easy it was to exploit.
Only if their modem didn’t implement the Hayes command set properly or you could otherwise control the per-character timing of the OS sending. It required a pause (1sec by default), “+++” with no pauses, another pause, _then_ the ATH command
I’m too lazy to look it up but there was some string you could send over IRC that would make some routers drop the connection immediately - if you pasted that string in a big channel you would see dozens of people immediately disconnect.
I remember you could brute force passwords by brute forcing in sequence single characters to access anyone’s disk on a giant dialup network. Crazy times.
Hilariously, the PPP (Point-to-Point Protocol) is still used in modern IoT modules. It is actually the only way to run your own TCP/IP stack (and maintain control over TLS), as not all modules support QMI or MBIM.
Seems like this should have been obvious to someone on the iOS team, no?
Like, "hey we need a way to trigger springboard UI events.."
"ok let's just use this unauthenticated bus and have springboard subscribe to it"
Something like that? Only thing I can think of is that this line of code was written so long ago and it's way at the bottom of the abstraction stack, so no one had a look
The notification API is quite old (iOS 3). It's explicitly an untrusted API that you shouldn't use for something like showing the restore in progress UI, so I suspect that was something written quite a bit later. Widget extensions are iOS 14. There's older ways to run background tasks, but none of them would give the soft brick. Background fetch, for example, originally didn't run until after you launched an app for the first time after restarting.
Darwin notifications are so old they don't have any availability annotations (block-based darwin notification APIs like notify_register_dispatch() were introduced in macOS 10.6 / iOS 3.2, but the rest of them are declared as always available). They absolutely predate any notion of an AppStore, of being able to install apps without implicitly putting a lot of trust in the app to not be malicious.
> That single line of code was enough to make the device enter “Restore in Progress”.
> as established before, any process could send the notification and trick the system into entering that mode.
Readit News
I don’t specifically know the types of things that you’d want to share across apps, but there’s a long history of cross process information channels being removed or restricted.
If the system is storing values for you, and isn’t keeping track of which app they came from, now you’ve got persistent storage across app deletion & re-install, as long as there isn’t a reboot in between.
I think you could easily use it to work around IDFA or IDFV resets, as a simple example.
The design is old. It probably predates facebook, so it's not been intentional, as your comment might be interpreted. But it certainly seems ripe for abuse. I'm curious if it would actually be used for that, because any app that can access internet already has a better way to share information.
I think the approach you describe allows roughly the same, except perhaps doing so without (or with different) permissions, and allowing to do this between vendors (that must agree upon this upfront).
DFU mode boots entirely from read-only ROM, and from there, you can just restore everything via USB cable.
Same applies to Apple Silicon Macs. You can damage the system, recovery and emergency recovery volumes, but even then, you can still boot into DFU from ROM and re-initialize everything via another Mac.
This is in contrast to some PCs, where if you damage the BIOS (e.g. by suddenly losing power during a firmware update), your device may or may not be bricked. There have even been stories of peoples' computers being bricked via rm -rf /, due to removing everything at /sys/firmware/efi/efivars/ (which is actually stored inside the motherboard), and sometimes contains things that the motherboard won't boot without
There definitely are (If you count jailbroken iPhones). I've managed to brick one by removing all thermal throttling limits and subsequently damaging the motherboard with the world's shittiest watercooling setup.
Can't use DFU to restore if you've got damaged hardware
I would expect that most systems should be recoverable from this state with a CMOS clear.
> This is in contrast to some PCs, where if you damage the BIOS (e.g. by suddenly losing power during a firmware update), your device may or may not be bricked.
I accidentally destroyed the firmware on a machine that did not have any recovery features, when flashing modified UEFI images, leaving it mostly inoperable. I wound up recovering it using flashrom and a Raspberry Pi. I think this counts as a hard brick, but the modular nature of PCs (e.g. most BIOS chips are on sockets so you can pull them out easily) it's not nearly as big of an issue if you hard-bricked a device that's more integrated and locked down. It's not instant e-waste because no bricks are permanent.
(It's a little harder for laptops, but I did also flashrom a laptop in a similar fashion, in-circuit using a SOIC8 clamp. This was not a brick recovery but rather messing with coreboot.)
Definitely not as much for the faint of heart, but a repair technician could do it for you. Alternatively, for PCs with socketed BIOS, you can buy a new EEPROM that's already flashed with the right firmware--they were readily available on eBay last I looked.
That was probably a decade ago or more by now. Many modern PC motherboards from many vendors have mitigations for this; it was a common enough pain point after all. For example, my desktop PC has an embedded controller that can boot and rewrite the flash chip for you, using a copy of BIOS from a USB stick. (Works even if the CPU isn't installed. Pretty cool.)
> There have even been stories of peoples' computers being bricked via rm -rf /, due to removing everything at /sys/firmware/efi/efivars/ (which is actually stored inside the motherboard), and sometimes contains things that the motherboard won't boot without
EFI vars are stored in NVRAM, not the EEPROM. You can usually clear that a couple of ways:
- Use an integrated NVRAM reset system. Some machines have a way to do this listed in their manual. On desktop PC motherboards, it tends to be a jumper you set for a few seconds. Sometimes you will have an easier option, like a button somewhere, or even possibly a key combination at boot (Long time Macintosh fans probably have memorized the NVRAM reset key chord for Apple computers... I wonder if it still works on Apple Silicon.)
- Remove the battery for a few seconds. Usually easily accessible on a desktop. Usually a little less easy to get to on a laptop, but nothing absurd, usually just some screws.
Certainly it could be easier to recover from, I'd say it's actually not very easy to brick a typical desktop PC in a particularly permanent fashion. The only time I've ever done it was because I was modifying my UEFI image intentionally. Screwing up EFI vars doesn't make most systems unbootable. I have corrupted my EFI vars quite a few times trying to do funny things. UEFI implementations do tend to be buggy, but not all of them are that catastrophically bad.
--
Now... as for whether or not an Apple Silicon device can "physically" be bricked by software, the most obvious way to do that would be to wear the SSD down to the point where it can no longer be rewritten. I think the M4 Mac Mini finally no longer solders these and that the Mac Minis do have a way you can recover from this brick (using another Mac to restore to a new SSD) but there are many Macs where if the SSD is destroyed, it's pretty hard to fix since you need Apple tools that are hard to obtain if you want to pair a new SSD. This is unfortunate because Apple has often had dodgy hardware choices around the SSD (e.g. the notorious TPS62180 buck converter) and doesn't always use SSDs that have the best reliability (IIRC they use a lot of Kioxia in the newer Apple Silicon devices, which are not considered to be bad devices by any means, but are generally considered less durable than e.g. Samsung SSDs.)
Rather than have an Apple device become ewaste due to software issues, in recent years, it is much more likely that it will become ewaste due to hardware issues, as a result of parts pairing and having failure-prone components that are not modular even when they really can and should be (Good on them for rectifying this lately, e.g., with the Mac Mini SSD, but it's a bit sad that it took this long. And on the note of that SSD... Apple, you really could've used a standard electrical interface for that.)
This is somewhat a testament to Apple's software and system design, but it's simultaneously a condemnation of their recent track record with repair, too. Best we can hope is that they don't go backwards from this point forward, because they created a lot of devices that will become ewaste over time for almost no gain for anyone. (I strongly dislike but can understand the justification for something like parts pairing in iPhones and iPads, but much less so for similar sorts of mechanisms in computers.)
https://news.ycombinator.com/item?id=43775027
Dead Comment
"Soft brick" is the correct term that already exists.
> The result is a device that’s soft-bricked, requiring a device erase and restore from backup.
Requiring a device erase isn't a full brick, no, but it's still pretty serious.
https://web.archive.org/web/19981206105844/http://www.sophis...
Like, "hey we need a way to trigger springboard UI events.." "ok let's just use this unauthenticated bus and have springboard subscribe to it"
Something like that? Only thing I can think of is that this line of code was written so long ago and it's way at the bottom of the abstraction stack, so no one had a look
It seems like such an obvious security concern. Maybe it was pre-AppStore? And more assumed trust in other apps?