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Downfall Attacks

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121–130 of 349 posts

Re: Downfall Attacks

#121
The Linux mitigation can be disabled with gather_data_sampling=off in the kernel boot parameters.

Be warned, apparently Grub had some kind of problem back in August 2022 and this pre-existing bug broke my boot completely when I updated grub for the above mitigation. I had to boot into a live ISO and reinstall grub to fix it.

Re: Downfall Attacks

#122

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 ma…

Tinfoil hat time:

They know at release about many of these bugs but between incentivizing upgrades and selling the resultant bugs as backdoor to 'three letter agencies' there's simply too much money to be made by not disclosing/patching the problems before third parties release discovery of the problems.

Re: Downfall Attacks

#123

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 ma…

This could be a case of survivorship bias - we don't know how many spectre-like bugs did get patched, because they never made it to the public

Re: Downfall Attacks

#124

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 ma…

Like how car companies will do a cost/benefit analysis to see if a recall is worth it.

Re: Downfall Attacks

#125

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 ma…

A fundamental problem is that the attack surface is so, so huge. Even if their security researchers are doing blue-sky research on both very small and very broad areas of processor functionality, they're going to miss a lot.

And in line with that and

>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?

... maybe they have patched a number of issues and just never announced them.

Re: Downfall Attacks

#126

The Linux mitigation can be disabled with gather_data_sampling=off in the kernel boot parameters. Be warned, apparently Grub had some kind of problem back in August 2022 and this pre-existing bug broke my boot completely when I updated grub for the above mitigation. I had to boot into a live ISO and reinstall grub to fix it.

Simply removing the parameter didn't fix it? Or you just reinstalled grub to be sure it would work

Re: Downfall Attacks

#127

The Linux mitigation can be disabled with gather_data_sampling=off in the kernel boot parameters. Be warned, apparently Grub had some kind of problem back in August 2022 and this pre-existing bug broke my boot completely when I updated grub for the above mitigation. I had to boot into a live ISO and reinstall grub to fix it.

Simply removing the parameter didn't fix it? Or you just reinstalled grub to be sure it would work

The parameter was unrelated to the issue with grub but I thought I'd mention the grub issue in case anyone else gets surprised like me.

Re: Downfall Attacks

#128

Stop. Releasing. Attack research. Without. Detection strategies.

They probably concluded it wasn't possible in this case. From their FAQ:

[Q] Is there a way to detect Downfall attacks?

[A] It is not easy. Downfall execution looks mostly like benign applications. Theoretically, one could develop a detection system that uses hardware performance counters to detect abnormal behaviors like exessive cache misses. However, off-the-shelf Antivirus software cannot detect this attack.

Re: Downfall Attacks

#129
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?

Yeah, I am sure the customers can sue, but would they win? I find it unlikely.

Re: Downfall Attacks

#130

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 ma…

Like how car companies will do a cost/benefit analysis to see if a recall is worth it.

Having worked in the industry, my gut feeling is that chipmakers don't invest all that much in looking for and preventing these sorts of attacks.

When working on a new feature, you are desperately trying to deliver on time something that adds value in the sorts of scenarios that it was designed for. And that is already hard enough.

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