Thread by @axi0mX

Security implications of this SEPROM vulnerability are not as bad as you might think:

(1) Browser-based (nation states) or app-based (community) jailbreaks cannot use it, because the value in TZ0 register is locked and cannot be changed after boot.

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https://twitter.com/axi0mX/status/1286651383186219009

(2) Apple's HW and SW uses many different mitigations, and they work together to limit the impact of a single vuln. This vuln cannot even be triggered without a vuln like #checkm8. Unless something like #checkm8 is found for A12/A13, we cannot even check if this issue exists.

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(3) A #checkm8-based jailbreak can use this vuln to exploit SEPROM, patch SEP/OS in a meaningful way, and then protect SEP from further access after iOS boots. SEP could then still be secure against accesses from the AP, and apps and tweaks will not be able to exploit it.

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(4) If you think about it, it is amazing that we can use powerful low-level public vulnerabilities to control what code we run on the iPhone AP and SEP, and yet those vulnerabilities cannot be abused in a meaningful way after the device boots.

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(5) As long as no one else takes physical possession of the device, plugs in a cable and puts it in DFU Mode, it is still secure, and we can use latest iOS with all security patches. Yet, we have the option to jailbreak it anytime, if we want to, and do anything we want.

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(6) We should have the option to take full control of our devices, if we want to. Whether it is for research, development, or just for jailbreaking, Apple should give us the option to take full control of our devices. We should not need public exploits to be able to do this.

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(7) There are no technical reasons preventing Apple from doing this. They could ask us to pay a fee to enable developer features, wait 30 days, disable Apple Pay, force a development SEP UID key to disable access to existing user data, and require a tethered boot every time.

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(8) No hardware changes would be needed to make this possible. They could even allow us to only choose this option when the device is first sold, and never give us any tickets for booting the device without a cable and a computer.

They could easily do this if they wanted to.

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