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Downfall Attacks

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Re: Downfall Attacks

#111

Earlier quoted context omitted.

If someone created a way for WASM to talk to an SDL equivalent, it'd probably end use of HTML & CSS

If so, all people relying on (often limited even with html that contains text) accessibility features will have to sit in a corner and cry.

I think that should be addressable.

Re: Downfall Attacks

#112
post #36

Once again it seems clear that running code from two security domains on the same physical processor cores is just not possible to get right, and we should probably just stop doing it. There are really only two common cases for this anyway. VMs and JavaScript. For VMs we just need to give up on it. Dedicate specific cores to specific VMs or at least customers. For JavaScript it’s a bit harder. Either way, we need to…

This is an unreasonable position. Vulnerabilities can be fixed

> This is an unreasonable position. Vulnerabilities can be fixed

That's a highly optimistic position, to the point of being almost wishful thinking.

The vulnerability being talked about today has been around since 2014 according to the report. Possibly being exploited for unknown number of years since. Sure, maybe we can workaround this one, now.

Other similar ones to be published years into the future are also there today being likely exploited as we speak.

Running untrusted code on the same silicon as sensitive code (data), is unlikely to ever actually be truly safe.

Re: Downfall Attacks

#114
Am I correct in understanding this affects basically every CPU generation up to and including Alder Lake?

EDIT: Maybe not? That linked table is very esoteric.

Re: Downfall Attacks

#116
post #94

The Intel paper link is dead, this seems to be the right one: https://www.intel.com/content/www/us/en/developer/articles/t... General caveats: are there many clouds that still run workloads from different users on the same physical core? I thought most had changed their schedulers years ago so you can't get cross-domain leaks between hyperthreads anymore. Claiming that it affects all users on the internet seems like…

>are there many clouds that still run workloads from different users on the same physical core? There are a vast number of VPS providers out there that aren’t AWS/GCP/Azure/etc where the answer is yes. Even the ones that sell ‘dedicated’ cores, which really just means unmetered cpu

Per the paper, this looks like an attack against speculated instructions that modify the store forward buffer. The details aren't super clear, but that seems extremely unlikely to survive a context switch. In practice this is probably only an attack against hyperthread code running simultaneously on the same CPU, which I'd expect cloud hosts to have eliminated long ago.

Re: Downfall Attacks

#117
Only up to 11th gen... it didn't seem like this could have been disclosed to Intel soon enough for them to have fixed it for 12th gen, so had they just happened to fix it while fixing something else, or what?

Decided to look in the paper and "Intel states that newer CPUs such as Alder Lake, Raptor Lake, and Sapphire Rapids are unaffected, although not a security consideration and seems just a side effect of a significantly modified architecture." So basically they just randomly fixed it, or at least made this particular exploit nonworkable.

Re: Downfall Attacks

#118
post #98
post #94

Earlier quoted context omitted.

>are there many clouds that still run workloads from different users on the same physical core? There are a vast number of VPS providers out there that aren’t AWS/GCP/Azure/etc where the answer is yes. Even the ones that sell ‘dedicated’ cores, which really just means unmetered cpu

What about burstable instances on AWS, and whatever is the equivalent in other clouds? Hard to imagine those having a dedicated core, would probably defeat the purpose.

https://docs.aws.amazon.com/whitepapers/latest/security-desi....

Re: Downfall Attacks

#119
post #71

Earlier quoted context omitted.

The mitigation here can incur a whopping 50% performance penalty. At what point can customers return these CPUs for either being defective or sue for false advertising? If they can't safely meet the target performance they shouldn't be doing these tricks at all.

Did processor companies ever advertise that processors guaranteed certain security properties of the software they execute? Aren't system designers at fault for coming up with the idea of a context switch and assuming that we can trust a processor not to leak details across artificial software constructed boundaries?

According to OP, SGX is also vulnerable. There has been quite some marketing around the supposed security properties of SGX, yes.

Re: Downfall Attacks

#120
What I find odd is that after the initial Spectre attacks, there have been a long string of these attacks discovered by outside researchers and then patched by the chipmakers.

In principle it seems like the chipmakers should hold all the cards when it comes to discovery: they are experts in speculative execution, know exactly how their chips work and have massive existing validation suites, simulators and internal machine-readable specifications for the low-level operations of these chips.

Outside researches need to reverse all this by probing a black box (plus a few much-worse-than-insider sources like patents).

Yet years after the initial disclosures it's still random individuals or groups who are discovering these? Perhaps pre-Spectre this attack vector wasn't even considered, but once the general mechanism was obvious did the chip-makers not simply set their biggest brains down and say "go through this with a fine-toothed comb looking for other Spectre attacks"?

Maybe they did and are well aware of all these attacks but to save face and performance hits they simply hold on to them hoping nobody makes them public?

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