6 ms·

"When Apple's servers go down you lose the ability to do low-level recovery on these machines anyway, since DFU flashing requires phoning home to get a ticket f

"When Apple's servers go down you lose the ability to do low-level recovery on these machines anyway, since DFU flashing requires phoning home to get a ticket for your machine as well as low-level configuration data" https://news.ycombinator.com/item?id=29704923 https://news.ycombinator.com/item?id=29704923

judge2020 5y ago
This has been a thing on iOS since I want to say the iOS 7 days, ie. the introduction of shsh2 blobs, and it ultimately hasn't been an issue.
- InvertedRhodium 5y ago
  Unless, of course, you need to perform a low level recovery when Apples servers are unavailable, for whatever reason. Then, it seems that it would be quite the problem.
  - afandian 5y ago
    Or they do the equivalent of forgetting to update a root CA, orphaning your machine, as happened to a family member of mine.
marcan_42 5y ago
For comparison, note that you can't do low level recovery at all on e.g. Google Pixel phones. Lose the contents of your storage there and the phone is bricked, as Google does not provide the low level flashing tools and signed images to do that. Apple does, with the phone home caveat. On x86 PCs, you can usually download a BIOS image, but to flash it you need hardware tools on most computers. So it's better in that you don't need to phone home, and worse in that you need specialized tools to do it. You might also lose serial numbers and other personalization information. Note: "Factory" images aren't this (and that's a misnomer, they aren't what is used at the factory). Those are OS images. To flash them your bootloader needs to be intact. We're talking about recovering from complete loss of writable storage here - that requires OEM tools to boot low level recovery images from the boot ROM alone. Some of these have leaked, but for very few devices. Apple just gives all of this to you on macOS and we have an open source reimplementation of their DFU tooling (idevicerestore) that you can run on any OS to restore any M1 Mac or iDevice to any (signable) OS version. To this day, all non-beta macOS for M1 releases are signable; I imagine they'll only revoke old ones if a major security flaw is found that impacts device backdoorability or allows SEP compromise or so, and even then you could still install an older OS in reduced security mode, just not as the first OS installed during low level recovery.
- duskwuff 5y ago
  > On x86 PCs, you can usually download a BIOS image, but to flash it you need hardware tools on most computers. Even then, it isn't always obvious how to write that image to flash. Sometimes you get lucky and the downloadable BIOS is a full image of the serial flash chip, but sometimes it's a delta update, or the flash chip contains other data (like configuration) which isn't part of the public image. And even then, there's a ton of other updatable firmware in a typical PC that isn't part of a BIOS update -- most video adapters and network devices will have at least a small flash chip on board, which may not be repairable at all if it's damaged.
  - marcan_42 5y ago
    Yup. On M1s Apple tries to make all external chips either use runtime loaded firmware or be bootloadable, both for security and recoverability reasons. I don't know if it's possible to truly brick an M1, but if it is you have to try really hard.
  - floatboth 5y ago
    GPUs are often the easiest to recover actually – boot with another GPU, keeping the screwed-up one plugged in – it will still be flashable, just run atiflash or whatever. Also, high end "gamer" hardware often includes "dual BIOS" (on both mainboards and graphics cards) and/or "BIOS flashback" (special button makes a microcontroller flash an image from a USB stick inserted into a marked port, even without a CPU present).
- est31 5y ago
  Google Pixel phones are phones though, and not personal computer devices like M1 Macs are. Phones have traditionally been more locked down. A fairer comparison would be to Chromebooks, which do have a screw to let you flash a different BIOS.
  - floatboth 5y ago
    The screw meme just doesn't die… Modern Chromebooks use a debug USB-C cable for flashing and serial console access, and a "sit around for like 15 minutes pressing power button when told" process to prove ownership to unlock dev mode.

judge2020 5y ago

This has been a thing on iOS since I want to say the iOS 7 days, ie. the introduction of shsh2 blobs, and it ultimately hasn't been an issue.

InvertedRhodium 5y ago
Unless, of course, you need to perform a low level recovery when Apples servers are unavailable, for whatever reason. Then, it seems that it would be quite the problem.
- afandian 5y ago
  Or they do the equivalent of forgetting to update a root CA, orphaning your machine, as happened to a family member of mine.

marcan_42 5y ago

For comparison, note that you can't do low level recovery at all on e.g. Google Pixel phones. Lose the contents of your storage there and the phone is bricked, as Google does not provide the low level flashing tools and signed images to do that. Apple does, with the phone home caveat. On x86 PCs, you can usually download a BIOS image, but to flash it you need hardware tools on most computers. So it's better in that you don't need to phone home, and worse in that you need specialized tools to do it. You might also lose serial numbers and other personalization information. Note: "Factory" images aren't this (and that's a misnomer, they aren't what is used at the factory). Those are OS images. To flash them your bootloader needs to be intact. We're talking about recovering from complete loss of writable storage here - that requires OEM tools to boot low level recovery images from the boot ROM alone. Some of these have leaked, but for very few devices. Apple just gives all of this to you on macOS and we have an open source reimplementation of their DFU tooling (idevicerestore) that you can run on any OS to restore any M1 Mac or iDevice to any (signable) OS version. To this day, all non-beta macOS for M1 releases are signable; I imagine they'll only revoke old ones if a major security flaw is found that impacts device backdoorability or allows SEP compromise or so, and even then you could still install an older OS in reduced security mode, just not as the first OS installed during low level recovery.

duskwuff 5y ago
> On x86 PCs, you can usually download a BIOS image, but to flash it you need hardware tools on most computers. Even then, it isn't always obvious how to write that image to flash. Sometimes you get lucky and the downloadable BIOS is a full image of the serial flash chip, but sometimes it's a delta update, or the flash chip contains other data (like configuration) which isn't part of the public image. And even then, there's a ton of other updatable firmware in a typical PC that isn't part of a BIOS update -- most video adapters and network devices will have at least a small flash chip on board, which may not be repairable at all if it's damaged.
- marcan_42 5y ago
  Yup. On M1s Apple tries to make all external chips either use runtime loaded firmware or be bootloadable, both for security and recoverability reasons. I don't know if it's possible to truly brick an M1, but if it is you have to try really hard.
- floatboth 5y ago
  GPUs are often the easiest to recover actually – boot with another GPU, keeping the screwed-up one plugged in – it will still be flashable, just run atiflash or whatever. Also, high end "gamer" hardware often includes "dual BIOS" (on both mainboards and graphics cards) and/or "BIOS flashback" (special button makes a microcontroller flash an image from a USB stick inserted into a marked port, even without a CPU present).
est31 5y ago
Google Pixel phones are phones though, and not personal computer devices like M1 Macs are. Phones have traditionally been more locked down. A fairer comparison would be to Chromebooks, which do have a screw to let you flash a different BIOS.
- floatboth 5y ago
  The screw meme just doesn't die… Modern Chromebooks use a debug USB-C cable for flashing and serial console access, and a "sit around for like 15 minutes pressing power button when told" process to prove ownership to unlock dev mode.