I'm talking about the time Apple was asked to provide an alternative firmware to unlock the iPhone of the San Bernardino shooter, which suggests that at least Apple itself can put a new firmware on a locked device without having it wiped.
Anyway, a hypothetical alternative firmware couldn't just magically bypass the encryption. What it could have done, and I think this may only apply to older iPhone models as it's now handled by the Secure Enclave(?), is make it easier to brute-force the pincode (no lockout, less delay).
It also doesn't really matter whether the compromise is a direct key extraction or just defeating the anti-bruteforce protections, the root flaw here is with the phone accepting new privileged software while locked and still retaining its state.
No, but it could presumably brute force the pin (unless the rate limiting is hardware controlled?) or wait until the user enters it, then decrypt everything.
I think this is the case on newer iPhones. But it might be flawed somehow given how Cellebrite were still able to brute-force?
I'm talking about having device data preserved and made accessible, while the device is screen-locked, without having any credentials or the passcode - pick all three.