Comment by hnburnsy

2 years ago

>It was complex because of all of the defenses put in place by Apple and others.

I don't know jack about hardware but it would seem obvious that when one designs a chip, you make sure it does not have 'unknown hardware registers' or unknown anything when you get it back from the manufacture.

This makes everything written on this page worthless...

>Prevent anyone except you from using your devices and accessing your information. https://www.apple.com/privacy/control/

10 comments

hnburnsy

Reply
tuetuopay  2 years ago

> I don't know jack about hardware but it would seem obvious that when one designs a chip, you make sure it does not have 'unknown hardware registers' or unknown anything when you get it back from the manufacture.

well you are in trouble then. all of modern hardware have such hidden parts in them, and are most of the time referenced as "undocumented" instead of "unknown". I know this seems pedantic, but from a public eye, anything undocumented is unknown. what makes those special however, is those are not used at all by public software, thus truly unknown as one can only guess their use or even their mere existence.

  • adrian_b  2 years ago

    "Undocumented" as used by hardware manufacturers is an euphemism for "secret".

    • nl  2 years ago

      It's actually not at all. Secret means "do not disclose". Undocumented can include that set but also a bunch of other things.

aidenn0  2 years ago

> I don't know jack about hardware but it would seem obvious that when one designs a chip, you make sure it does not have 'unknown hardware registers' or unknown anything when you get it back from the manufacture.

Either Apple or Arm has employees that know what these registers do. They are likely used for debugging and/or testing.

A lot of those registers can do very interesting things, since e.g. fault-injection is an important part of testing. A security-minded implementation will allow these to either be fused off or disabled very early in the boot process. The latter is probably more common, and any disconnect between the hardware and software side can cause this step to get missed.

  • hnburnsy  2 years ago

    Very interesting, thanks dor the insight. Would you fault Apple for not disabling these?

dagmx  2 years ago

You’re assuming the registers are unknown to the chip designer.

The article doesn’t state that. It says it’s undocumented for the security researchers.