Comment by bri3d
4 hours ago
We can just do research to figure that out? The recent trend towards conspiracy theories against things that are trivially discoverable is so frustrating.
https://post-cyberlabs.github.io/Offensive-security-publicat...
https://blog.scrt.ch/2024/10/28/privilege-escalation-through...
Yes, the PIN is entangled with the key material.
The article shows that the PIN-entangled key material can still be downloaded directly from the TPM.
This means it's vulnerable to an offline bruteforce attack to derive the PIN.
So it's still doable, even in an automated fashion, just slower.
With today's multi-GPU cloud systems available to everyone with a credit card, you can probably crack the default-length 6-digit PIN the same day you extract the key protector.
I'm glad we were able to move past "We don't know how that mechanism works, it could just be a totally separate gate that IS bypassable" and into the actual way the mechanism works!
> The article shows that the PIN-entangled key material can still be downloaded directly from the TPM.
Not exactly, the TPM has PolicyAuthValue(PIN), so the PIN also needs to be provided to the TPM to unseal the material, and the hardware anti-hammering should prevent brute forcing it this way. The blog post documents dumping the PIN-entangled key material by MITM-ing the TPM communication while a user enters the PIN; the entanglement is a belt-and-suspenders approach.
> The recent trend towards conspiracy theories against things that are trivially discoverable is so frustrating.
So true.