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The One Weird Trick SecureROM Hates [pdf] (iokit.racing)
78 points by 1on0 25 days ago | hide | past | web | favorite | 22 comments

TIL SecureROM != SecuROM.

I came to this post anticipating a nostalgic trip about some ancient DRM and a stupidly simple way to break it.

Got confused when it was about Apple phone OS.


It was weird to see people from the jailbreak scene (easily recognisable because they all have names l1ke th1s) in such an exploit... turns out SecureROM is also something from iPhone

haha, same here


Cellebrite is listed under whoareus, but with a bunch of pseudonyms.

Is that the same Cellebrite?


Wow, it's really cool to read how things like this happen.

While we're here, is there anything I can use to remove the alphanumeric passcode from an iPad 4 (A6X chipset, no Secure Enclave) that I've forgotten the password to?

There's a device called "IP box" which may be able to do that, it's not cheap but a mobile repair/unlocking store would probably have one.

How does it work?

For a 4 digit unlock code, the device would enter them sequentially starting from 0000 and ending at 9999 [1]. Because there is a delay of 6 seconds between each attempt (on iOS 7.xx) it would take just over 16 and a half hours to try all codes.

[1] https://www.fonefunshop.com/ip-box-iphone-password-unlock-to...

Right now with these tools you are just playing passcode roulette to recover your device if you forgot the code and you enabled factory wipe after N tries.

Out of these retries, at least 1/N correct passcode attempts are needed, so such tools are close to useless if your care about retrieving your data with factory wipe enabled.

Why on earth would you have a heap in a zero-stage-burned-into-chip bootloader, not to mention a USB stack. It's just self-inflicted harm at this point.

USB stack is because one of the rom bootloader’s primary functions is DFU mode so that you can reflash a bricked device.

A heap isn't needed, it is just super helpful.

Also DFU is not the world's best protocol, I am surprised Apple didn't just roll their own. It isn't exactly hard to replace DFU with something simpler that gets the job done.

Either all the senior engineers and PhDs working for Apple are idiots, or it’s harder than you think.

This same heuristic can be applied all across the HN front page with good results.

> Either all the senior engineers and PhDs working for Apple are idiots, or it’s harder than you think.

I was part of a team that rolled our own firmware update mechanism at Microsoft . (I didn't work on the replacement myself, the engineer sitting next to me did.)

And deeply embedded USB stacks w/o a heap aren't exactly uncommon, considering malloc is forbidden in a large % of firmware.

I'm sure the choice was made by a small team back when iPhone was still a carefully guarded secret inside the company, and it's stuck around since then.

The costs just outweigh the benefits.

Nothing to do with idiot engineers or the task being hard. They could be idiots _and_ the task easy. Some things just don't need to be done.

It's entirely possible that it was a "good enough for now" decision, and that the next bootrom will include additional hardening based on this attack.

As has been well documented, while Apple the organization may have practically unlimited resources, specific teams within Apple do not, so a lot of stuff is sort of "if it ain't broke" mode until the CADT model kicks in and they do a total rewrite and close all the old bugs.

Not the best, but not the worst. It's pretty simple as it is.

That there are allocations is odd.

One slide says for some roms: No crash is triggered whatsoever as the ROM is deterministic enough that the buffer is reallocated in the same place every time upon USB stack initialization.

We aren't looking at the code, but "deterministic reallocation" or just static storage class? Seems like dynamic memory allocation was introduced recently into this rom. And why is a good question.

lol The title is technically against HN guidelines (clickbait), but since it's so blatantly obvious that it's tongue-in-cheek/sarcastic, it's probably fine.

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