Comment by kfreds

2 years ago

> I feel like this is all smoke and mirrors to redirect from the likelihood intentional silicon backdoors that are effectively undetectable.

The technologies Apple PCC is using has real benefits and is most certainly not "all smoke and mirrors". Reproducible builds, remote attestation and transparency logging are individually useful, and the combination of them even more so.

As for the likelihood of Apple launching Apple PCC to redirect attention from backdoors in their silicon, that seems extremely unlikely. We can debate how unlikely, but there are many far more likely explanations. One is that Apple PCC is simply good business. It'll likely reduce security costs for Apple, and strengthen the perception that Apple respects users' privacy.

> when registers r0-rN are set to values [A, ..., N] and a jump to address 0xCONSTANT occurs

I would recommend something more deniable, or at the very least something that can't easily be replayed. Put a challenge-response in there, or attack the TRNG. It is trivial to make a stream of bytes appear random while actually being deterministic. Such an attack would be more deniable, while also allowing a passive network attacker to read all user data. No need to get code execution on the machines.

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kfreds

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formerly_proven  2 years ago

Apple forgot to disable some cache debugging registers a while back which in effect was similar to something GP described, although exploitation required root privileges and would allow circumventing their in-kernel protections; protections most other systems do not have. (And they still didn't manage to achieve persistence, despite having beyond-root privileges).

  • kfreds  2 years ago

    > Apple forgot to disable some cache debugging registers a while back which in effect was similar to something GP described

    Thank you for bringing that up. Yes, it is an excellent example that proves the existence of silicon vulnerabilities that allow privilege escalation. Who knows whether it was left there intentionally or not, and if so by whom.

    I was primarily arguing that (1) the technologies of Apple PCC are useful and (2) it is _very_ unlikely that Apple PCC is a ploy by Apple, to direct attention away from backdoors in the silicon.