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So, hypothetically speaking, say a laptop firmware has an SMM backdoor, how does using Linux bypass it in any way? Such firmware could for example scan system
by vardump 10y ago
So, hypothetically speaking, say a laptop firmware has an SMM backdoor, how does using Linux bypass it in any way?
Such firmware could for example scan system memory for cryptographic keys and send them over wifi or ethernet connection, without main OS even knowing.
SMM code is going to be executed at arbitrary times at highest possible privileges regardless of operating system.
Also any microcontrollers inside laptop manufacturers' ASICs can also do pretty much anything the manufacturer wants them to do (or possibly even some other party compromises them to do).
Manufacturer itself might not even be aware they're shipping compromised systems.
- deleted 10y ago[deleted]
- ryao 10y agoMy Linux remark applied solely to the backdoor that used a ACPI table to make Windows install malware on every boot, which I had linked. It did not claim that installing Linux protected you from anything else.
- vardump 10y agoThat ACPI table payload is conditional and obviously OS dependent. Overall not a huge threat. SMM interrupt code comes from the very same BIOS image and is executed at arbitrary times regardless of operating system. SMM code can do pretty much anything it pleases, it runs at the highest privilege and priority level possible.
- ryao 10y agoDiscussion of SMM interrupt code is irrelevant to the observation that installing Linux protects you from a Windows specific backdoor. That was not a claim that Linux provided safety against every possible backdoor. You seem to be trying to debunk a claim that no one made.
- vardump 10y agoI don't try to debunk anything. I think it's just silly to talk about some ACPI table payload, when there's a greater threat controlled by the same binary blob. SMM can do anything that ACPI payload could do and more. And we need to trust the same entity for its integrity. SMM is also operating system independent. It'll run no matter what operating system end user runs.
- ryao 10y agoIf you were not trying to debunk anything, then this was a very poor choice of words: > So, hypothetically speaking, say a laptop firmware has an SMM backdoor, how does using Linux bypass it in any way? Aside from that, good point.
- qb45 10y agoACPI? I think it's UEFI mounting the Windows partition and dropping some files there before booting the OS. ACPI executes on a virtual machine inside the kernel and afaik it's not supposed to be able to write to files.