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The original source[0] states that access to Recovery Mode is not possible, at least in some cases. One user there reports[1] that the device shows no signs of

The original source[0] states that access to Recovery Mode is not possible, at least in some cases. One user there reports[1] that the device shows no signs of life--no power, no fans spinning, nothing: > No power at all. I tried SMC and PRAM reset but sadly was unable to do either since my computer won’t even turn on. [0]: https://forums.macrumors.com/threads/warning-macos-catalina-10-15-4-supplemental-update-bricked-my-13-inch-macbook-2018.2230133/ https://forums.macrumors.com/threads/warning-macos-catalina-... [1]: https://forums.macrumors.com/threads/warning-macos-catalina-10-15-4-supplemental-update-bricked-my-13-inch-macbook-2018.2230133/?post=28350304#post-28350304 https://forums.macrumors.com/threads/warning-macos-catalina-...

floatingatoll 7y ago
Does this issue only affect T2 Macs and MacBooks? If so, maybe a DFU restore is needed.
- apfsx 7y ago
  Do T2 Mac’s have DFU mode like iPhone’s? If so that’s news to me and pretty interesting.
  - Shank 7y ago
    Yes. It’s essentially an ARM A-series chip — it has firmware (BridgeOS) and does have a DFU mode. See https://help.apple.com/configurator/mac/2.7.1/#/apd0020c3dc2 https://help.apple.com/configurator/mac/2.7.1/#/apd0020c3dc2
    - FireBeyond 7y ago
      Best have your spare MacBook available to do it!
      - floatingatoll 7y ago
        Desktop Macs should also be fine. I wouldn't be surprised if Apple ships Configurator iOS someday, but today is not that day.
      - nimish 7y ago
        Love to need another $3000 machine to fix my $3000 machine
        jedieaston 7y ago
        Right now, yes, but in usual circumstances you could just borrow a friend's box, your IT department could fix it, or you could have a el-cheapo Mac (either an old one or like a Mini from 2010) that can run Configurator (which doesn't require a recent version of OS X, I don't think). Still sucks, just a bit less. not really different than an iPhone, except that you can rebuild those on Windows (for now).
  - morpheuskafka 7y ago
    The T2 chip itself (runs bridgeOS which is like watchOS) do. It is used only to recover the firmware of the T2, AFAIK it can't be used to write to the SSD directly. The checkra1n team recently showed that all Macs with a T2 chip are vulnerable to checkm8 exploit used to jailbreak iPhones, and this could persist for a while due to the T2 chip staying on between application processor reboots. This allows override of mic disconnect (except on the newest models which switched to hardware disconnect), Secure Boot/Firmware Password, and allows you to bypass Apple's signing of Intel ME firmware, TB3 firmware, and CPU microcode. Whether or not there is still Intel signing after that is unknown, but there are already some sort of issues with the host key being leaked on that. The one useful feature I can think of is allowing SSD replacement (you still have to find a way to resolder ofc) and Touch Bar customization. I think the most likely attack vector for this is an evil maid style attack where corrupted T2 firmware is loaded that rewrites the contents of the SSD while macOS is running to launch further exploit code on that platform. The one thing not to worry about is if you have FileVault turned on with a password, that still can't be cracked because your password is not stored anywhere on the device. But the BitLocker-style automatic encryption with no password that just locks the SSD to that specific T2 chip isn't useful anymore.
    - apfsx 7y ago
      hi, thank you for posting this. I was fascinated by the checkm8 exploit since I read about it last September. Completely unknown to me was that T2 Mac's were also vulnerable to this. With all the vulnerabilities that are now open due to this, i'm questioning was it even worth ever putting these chips inside Macbooks? In retrospect, would they have been better off just scrapping this idea completely? Because the way you put it, due to the checkm8 exploit the T2 is now practically useless in everything it was originally meant to do.
- tbagman 7y ago
  Confirmed; this is what happened to my 16" after this install. I needed to do a DFU restore (using Apple Configurator 2 -- you can download it to your hopefully spare MacBook from the app store) to get my mac back up and running. Unfortunately, for some reason, after the DFU restore, my 16" came back up to do a full reinstall, and I had to restore my files from backup. Took a day, but all's well now.
  - bnt 7y ago
    I hope Apple doesn’t expect that everyone has a “Spare Macbook” laying around. I’ve been experiencing random system crashes when anything connects via TB3, and 3 random Kernel panics since the update.
  - floatingatoll 7y ago
    The SSD in a T2 Mac is encrypted in the same way that an iPhone is, so if the DFU crashes hard enough you’ll have to regenerate new keys and that’s equivalent to drive zero. Glad it helped.
    - jplayer01 7y ago
      Is it possible to export a recovery key? Because this kind of failure simply due to a bad update shouldn't be acceptable.
      - ThePowerOfFuet 7y ago
        No.
      - pvg 7y ago
        You get a recovery key when the original key is generated.
        floatingatoll 7y ago
        Yes: You can export a FileVault recovery key when enabling FileVault, whether on a T2 Mac or not. No: There’s no opportunity to use FileVault recovery keys when you’re doing a DFU on a T2 Mac. If you have to DFU, your data is lost. (edited to clarify per reply)
odshoifsdhfs 7y ago
I have this issue. Computer went to sleep after the update. This was on Friday. Haven't been able to do any kind of thing on it. Trackpad 'clicks' but no screen, not touchbar, nothing (2018 Macbook Pro). Called apple, they tld me it had to go a store, unfortunately where I live, due to quarantine there are no shops available to pick it, and we aren't allowed to drive outside our district. Will try the apple configurator idea someone posted below and will report back. Just need to find a cable that supports both power and data that is USB a to USB c.
- ThePowerOfFuet 7y ago
  Have you tried force-restarting it?
  - odshoifsdhfs 7y ago
    Tried it all, nothing worked. Even the DFU revive/restore. Tomorrow will call a close enough store that seems to be (stated on their website) doing pick-ups and see if they can come and pick it. My main concern now is they will try to try and charge 1000 or so euros for a repair and I will have to eat the cost as I can't really ask for a replacement one from company or friends since everyone is stuck at home
- LASR 7y ago
  Did you try the basics first? Hold down power for long time. 30 seconds. There is a small chance you’re not affected by this issue.
  - odshoifsdhfs 7y ago
    All possible things. 30 seconds, 60 seconds. 10 seconds then plug in cable. SMC reset. DFU mode (it enters dfu mode, but restore doesn't work). I spent the last 48 hours trying to bring it back to life. Unless Apple releases some kind of software we can use on another mac to 'fix' this one, I don't feel it will be fixed without shipping it to them.
- xenospn 7y ago

floatingatoll 7y ago

Does this issue only affect T2 Macs and MacBooks? If so, maybe a DFU restore is needed.

apfsx 7y ago
Do T2 Mac’s have DFU mode like iPhone’s? If so that’s news to me and pretty interesting.
- Shank 7y ago
  Yes. It’s essentially an ARM A-series chip — it has firmware (BridgeOS) and does have a DFU mode. See https://help.apple.com/configurator/mac/2.7.1/#/apd0020c3dc2 https://help.apple.com/configurator/mac/2.7.1/#/apd0020c3dc2
  - FireBeyond 7y ago
    Best have your spare MacBook available to do it!
    - floatingatoll 7y ago
      Desktop Macs should also be fine. I wouldn't be surprised if Apple ships Configurator iOS someday, but today is not that day.
    - nimish 7y ago
      Love to need another $3000 machine to fix my $3000 machine
      - jedieaston 7y ago
        Right now, yes, but in usual circumstances you could just borrow a friend's box, your IT department could fix it, or you could have a el-cheapo Mac (either an old one or like a Mini from 2010) that can run Configurator (which doesn't require a recent version of OS X, I don't think). Still sucks, just a bit less. not really different than an iPhone, except that you can rebuild those on Windows (for now).
- morpheuskafka 7y ago
  The T2 chip itself (runs bridgeOS which is like watchOS) do. It is used only to recover the firmware of the T2, AFAIK it can't be used to write to the SSD directly. The checkra1n team recently showed that all Macs with a T2 chip are vulnerable to checkm8 exploit used to jailbreak iPhones, and this could persist for a while due to the T2 chip staying on between application processor reboots. This allows override of mic disconnect (except on the newest models which switched to hardware disconnect), Secure Boot/Firmware Password, and allows you to bypass Apple's signing of Intel ME firmware, TB3 firmware, and CPU microcode. Whether or not there is still Intel signing after that is unknown, but there are already some sort of issues with the host key being leaked on that. The one useful feature I can think of is allowing SSD replacement (you still have to find a way to resolder ofc) and Touch Bar customization. I think the most likely attack vector for this is an evil maid style attack where corrupted T2 firmware is loaded that rewrites the contents of the SSD while macOS is running to launch further exploit code on that platform. The one thing not to worry about is if you have FileVault turned on with a password, that still can't be cracked because your password is not stored anywhere on the device. But the BitLocker-style automatic encryption with no password that just locks the SSD to that specific T2 chip isn't useful anymore.
  - apfsx 7y ago
    hi, thank you for posting this. I was fascinated by the checkm8 exploit since I read about it last September. Completely unknown to me was that T2 Mac's were also vulnerable to this. With all the vulnerabilities that are now open due to this, i'm questioning was it even worth ever putting these chips inside Macbooks? In retrospect, would they have been better off just scrapping this idea completely? Because the way you put it, due to the checkm8 exploit the T2 is now practically useless in everything it was originally meant to do.
tbagman 7y ago
Confirmed; this is what happened to my 16" after this install. I needed to do a DFU restore (using Apple Configurator 2 -- you can download it to your hopefully spare MacBook from the app store) to get my mac back up and running. Unfortunately, for some reason, after the DFU restore, my 16" came back up to do a full reinstall, and I had to restore my files from backup. Took a day, but all's well now.
- bnt 7y ago
  I hope Apple doesn’t expect that everyone has a “Spare Macbook” laying around. I’ve been experiencing random system crashes when anything connects via TB3, and 3 random Kernel panics since the update.
- floatingatoll 7y ago
  The SSD in a T2 Mac is encrypted in the same way that an iPhone is, so if the DFU crashes hard enough you’ll have to regenerate new keys and that’s equivalent to drive zero. Glad it helped.
  - jplayer01 7y ago
    Is it possible to export a recovery key? Because this kind of failure simply due to a bad update shouldn't be acceptable.
    - ThePowerOfFuet 7y ago
      No.
    - pvg 7y ago
      You get a recovery key when the original key is generated.
      - floatingatoll 7y ago
        Yes: You can export a FileVault recovery key when enabling FileVault, whether on a T2 Mac or not. No: There’s no opportunity to use FileVault recovery keys when you’re doing a DFU on a T2 Mac. If you have to DFU, your data is lost. (edited to clarify per reply)

odshoifsdhfs 7y ago

I have this issue. Computer went to sleep after the update. This was on Friday. Haven't been able to do any kind of thing on it. Trackpad 'clicks' but no screen, not touchbar, nothing (2018 Macbook Pro). Called apple, they tld me it had to go a store, unfortunately where I live, due to quarantine there are no shops available to pick it, and we aren't allowed to drive outside our district. Will try the apple configurator idea someone posted below and will report back. Just need to find a cable that supports both power and data that is USB a to USB c.

ThePowerOfFuet 7y ago
Have you tried force-restarting it?
- odshoifsdhfs 7y ago
  Tried it all, nothing worked. Even the DFU revive/restore. Tomorrow will call a close enough store that seems to be (stated on their website) doing pick-ups and see if they can come and pick it. My main concern now is they will try to try and charge 1000 or so euros for a repair and I will have to eat the cost as I can't really ask for a replacement one from company or friends since everyone is stuck at home
LASR 7y ago
Did you try the basics first? Hold down power for long time. 30 seconds. There is a small chance you’re not affected by this issue.
- odshoifsdhfs 7y ago
  All possible things. 30 seconds, 60 seconds. 10 seconds then plug in cable. SMC reset. DFU mode (it enters dfu mode, but restore doesn't work). I spent the last 48 hours trying to bring it back to life. Unless Apple releases some kind of software we can use on another mac to 'fix' this one, I don't feel it will be fixed without shipping it to them.
xenospn 7y ago