4 ms·

That mode indicates that the boot ROM failed to verify the signature on the bootloader. Generally this means that for some reason your bootloader got corrupted.

That mode indicates that the boot ROM failed to verify the signature on the bootloader. Generally this means that for some reason your bootloader got corrupted. The way to restore this is a special qualcomm tool, but you also need a properly formatted and signed package to flash using the tool, and i doubt that google would give it to you. How did it get corrupted? FTL issue in an aging eMMC? Bug in linux kernel block device driver? Malicious code? Sheer dumb misfortune? Who knows...

userbinator 5y ago
The way to restore this is a qualcomm tool, but you also need a properly formatted and signed package to flash using the tool, and i doubt that google would give it to you. I don't know how it is now, but my almost-decade-old generic Mediatek Android smartphone (still working, although seldom used) lets you access the whole eMMC in a special recovery mode using SPFlashTool, and there's no signing required. Looks like they have locked down things since then, ostensibly for security but more likely for corporate control and planned obolescence...
- dmitrygr 5y ago
  The official answer is that with no bootloader locking, there is no way to prevent an evil maid attack (replace OS with a replica that logs your passwords, exfiltrate them later). The real reasons are anyone's best guess...
  - Dylan16807 5y ago
    Which doesn't explain why you can't even wipe+unlock.
    - c0d3z3r0 5y ago
      Read again. It does. The boot ROM fails to verify the bootloaders (XBL) signature for some reason.
      - Dylan16807 5y ago
        Read what again? If the flash bootloader is failing to verify, I should be able to send a new one over the USB port, even if that requires wiping the device for security purposes. Defending against an evil maid attack doesn't explain why I can't do that.
        c0d3z3r0 5y ago
        Read the post from dmitrygr again or mine. The bootloader does not get loaded, because the verification fails. That means there is no way to wope or reset the device. Without a signed firehorse binary you can't do anything, because EDL just won't talk to you. More details: https://blog.quarkslab.com/analysis-of-qualcomm-secure-boot-chains.html https://blog.quarkslab.com/analysis-of-qualcomm-secure-boot-...
        Dylan16807 5y ago
        > The bootloader does not get loaded I get that, but there should be something in the ROM that can reflash the device. It already has signature verification code, which is the hard part to fit into a tiny ROM. > Without a signed firehorse binary you can't do anything, because EDL just won't talk to you. So... either they should release a firehorse binary that can wipe devices, or they should add a small bit of code that can wipe and flash without needing a firehorse binary. As I read it, dmitrygr was saying that the ostensible reason you can't do anything is fear of evil maid attacks, but that ostensible reason doesn't explain why there isn't a wipe+access mode. And "the bootloader is corrupt" isn't the reason, because this is about the pre-bootloader code.
        c0d3z3r0 5y ago
        > So... either they should release a firehorse binary that can wipe devices, or they should add a small bit of code that can wipe and flash without needing a firehorse binary. And how should they add code to a ROM of yet bricked devices? > As I read it, dmitrygr was saying that the ostensible reason you can't do anything is fear of evil maid attacks, but that ostensible reason doesn't explain why there isn't a wipe+access mode. And "the bootloader is corrupt" isn't the reason, because this is about the pre-bootloader code. Well, ask Google? :-)
- c0d3z3r0 5y ago
  Don't compare Qualcomm to Mediatek... it's different
molticrystal 5y ago
How is under investigation, but the when is much easier, the reports surge in the morning after an OTA update occurs while the owner is asleep.
c0d3z3r0 5y ago
Mostly correct. Just a slight correction: You not only need the right image to flash, which you do get from google (factory images) but you need a signed firehorse/edl binary the boot ROM will accept.

userbinator 5y ago

The way to restore this is a qualcomm tool, but you also need a properly formatted and signed package to flash using the tool, and i doubt that google would give it to you. I don't know how it is now, but my almost-decade-old generic Mediatek Android smartphone (still working, although seldom used) lets you access the whole eMMC in a special recovery mode using SPFlashTool, and there's no signing required. Looks like they have locked down things since then, ostensibly for security but more likely for corporate control and planned obolescence...

dmitrygr 5y ago
The official answer is that with no bootloader locking, there is no way to prevent an evil maid attack (replace OS with a replica that logs your passwords, exfiltrate them later). The real reasons are anyone's best guess...
- Dylan16807 5y ago
  Which doesn't explain why you can't even wipe+unlock.
  - c0d3z3r0 5y ago
    Read again. It does. The boot ROM fails to verify the bootloaders (XBL) signature for some reason.
    - Dylan16807 5y ago
      Read what again? If the flash bootloader is failing to verify, I should be able to send a new one over the USB port, even if that requires wiping the device for security purposes. Defending against an evil maid attack doesn't explain why I can't do that.
      - c0d3z3r0 5y ago
        Read the post from dmitrygr again or mine. The bootloader does not get loaded, because the verification fails. That means there is no way to wope or reset the device. Without a signed firehorse binary you can't do anything, because EDL just won't talk to you. More details: https://blog.quarkslab.com/analysis-of-qualcomm-secure-boot-chains.html https://blog.quarkslab.com/analysis-of-qualcomm-secure-boot-...
        Dylan16807 5y ago
        > The bootloader does not get loaded I get that, but there should be something in the ROM that can reflash the device. It already has signature verification code, which is the hard part to fit into a tiny ROM. > Without a signed firehorse binary you can't do anything, because EDL just won't talk to you. So... either they should release a firehorse binary that can wipe devices, or they should add a small bit of code that can wipe and flash without needing a firehorse binary. As I read it, dmitrygr was saying that the ostensible reason you can't do anything is fear of evil maid attacks, but that ostensible reason doesn't explain why there isn't a wipe+access mode. And "the bootloader is corrupt" isn't the reason, because this is about the pre-bootloader code.
        c0d3z3r0 5y ago
        > So... either they should release a firehorse binary that can wipe devices, or they should add a small bit of code that can wipe and flash without needing a firehorse binary. And how should they add code to a ROM of yet bricked devices? > As I read it, dmitrygr was saying that the ostensible reason you can't do anything is fear of evil maid attacks, but that ostensible reason doesn't explain why there isn't a wipe+access mode. And "the bootloader is corrupt" isn't the reason, because this is about the pre-bootloader code. Well, ask Google? :-)
c0d3z3r0 5y ago
Don't compare Qualcomm to Mediatek... it's different

molticrystal 5y ago

How is under investigation, but the when is much easier, the reports surge in the morning after an OTA update occurs while the owner is asleep.

c0d3z3r0 5y ago

Mostly correct. Just a slight correction: You not only need the right image to flash, which you do get from google (factory images) but you need a signed firehorse/edl binary the boot ROM will accept.