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JTAG lets us read / write the architecture states on a CPU core. Intel's CCA let's us connect to JTAG with a USB3 port. So why could an attacker not execute code to trick a flash drive plugged into a capable USB port to pass in the protocol used to communicate with JTAG.

enter image description here

It's not the typical USB protocol, but I don't see why an attacker couldn't potentially exploit the USB hardware to send a different protocol and take over the entire system in god-mode.

I suspect the answer is that USB's just cant be exploited to do that, but I thought I'd ask anyway since I've seen some exploitation vectors before that I'd never have thought imaginable.

Edit: To clarify, the question is about a remote attacker executing malware to leverage this feature meant for proximity access.

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  • \$\begingroup\$ clearly it depends on the flash drive. Not all flash drives are the same. Maybe it might require a specially crafted flash drive to perform the exploit. \$\endgroup\$
    – Kartman
    Commented Jun 12, 2021 at 4:58
  • \$\begingroup\$ Are you sure you're not asking a straw man question? If the interface's purpose is to debug, well yes, a debugger plugged into that port will be able to debug (notice that actual implementations might require some means of prior cryptographic authentication). Your question states "why can't...", and I'm missing the point where anyone claims that! \$\endgroup\$
    – mmmm
    Commented Jun 12, 2021 at 9:15
  • \$\begingroup\$ @mmmm you misunderstood. I'll edit to clarify. The attacker is a hacker is using malware on the machine in this case, not having physical access to it. \$\endgroup\$
    – J.Todd
    Commented Jun 12, 2021 at 11:40

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