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Downfall Attacks

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Re: Downfall Attacks

#81

Post by tomsmeding »

sidewndr46 wrote: post #65
throwaway892238 wrote: post #58

Earlier quoted context omitted.

Agreed. Browsers are now nothing but an application platform of APIs ( https://developer.mozilla.org/en-US/docs/Web/API ). For some reason they still retain the vestigial HTML, CSS and JS, but really all you need is bytecode that calls an ABI, and a widget toolkit that talks to a rendering API. Then we can finally ship apps to users without the shackles of how a browser wants to interpret and render some markup. The…

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.

Re: Downfall Attacks

#82

Post by BeeOnRope »

amarshall wrote: post #78
mike_hearn wrote: post #32

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…

> same physical core…between hyperthreads These are not the same thing. Afaik, most “vCPU” are hyperthreads, not physical cores. > I thought most had changed their schedulers years ago so you can't get cross-domain leaks between hyperthreads anymore It would be great to have a source on this.

> These are not the same thing. Afaik, most “vCPU” are hyperthreads, not physical cores.

OP didn't say otherwise. They are saying that public clouds do not let work from different tenants run on the same physical core (on different hyperthreads) at the same time.

This doesn't prevent you from selling 1 hyperthread as 1 vCPU, it just means there are some scheduling restrictions and your smallest instance type will probably have 2 vCPUs if you have SMT-2 hardware (and that's exactly what you see on AWS outside of the burstable instance types).

Re: Downfall Attacks

#83

Post by tedunangst »

mike_hearn wrote: post #32

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…

Does Digital Ocean count as a major cloud player?

Re: Downfall Attacks

#84

Post by ngneer »

I do not doubt the severity of the flaw, but most practical attacks end up being far more mundane. Consider SolarWinds, for example. No dazzling tricks needed, whatever gets the job done.

Re: Downfall Attacks

#85

Post by xigency »

throwaway892238 wrote: post #58
marssaxman wrote: post #35

Earlier quoted context omitted.

> For JavaScript it’s a bit harder. "We should probably just stop doing it" works for me.

Agreed. Browsers are now nothing but an application platform of APIs ( https://developer.mozilla.org/en-US/docs/Web/API ). For some reason they still retain the vestigial HTML, CSS and JS, but really all you need is bytecode that calls an ABI, and a widget toolkit that talks to a rendering API. Then we can finally ship apps to users without the shackles of how a browser wants to interpret and render some markup. The…

I do think there’s never been a better time to reinvent the web, including basic technologies like HTML and JavaScript.

For example, picking up more elements of semantic web and distributed systems and leveraging interconnected devices.

Re: Downfall Attacks

#86

Post by stalfosknight »

coder543 wrote: post #47
stalfosknight wrote: post #39

Earlier quoted context omitted.

I'm not trying to suggest that Apple's ARM chips are magically better because they're designed by Apple. Rather that the x86 architecture is obviously very long in the tooth and now would be a great time to switch to a far more modern architecture especially in light of this steady stream of vulnerabilities and defects that keep being found in x86. I'm sure ARM64 isn't perfect but I've yet to learn of something as se…

Just as a couple of examples… ARM has suffered from Spectre too: https://developer.arm.com/Arm%20Security%20Center/Spectre-BH... There was also PACMAN: https://appleinsider.com/articles/22/06/10/new-pacman-flaw-i... Speculative vulnerabilities have virtually nothing to do with the instruction set. Changing the language of the processor has little to do with how the processor works under the hood, especially for funda…

I did not know about PACMAN!

Re: Downfall Attacks

#87

Post by BeeOnRope »

vladvasiliu wrote: post #79
mike_hearn wrote: post #32

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…

> 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. Isn't this the whole point of AWS' t instances? It's my understanding that they are "shared" at the core level, or else there wouldn't be a reason for the CPU credit balance thing.

They are definitely time-sliced among tenants and very possibly two tenants may run at the same time on two hardware threads on the same core: but you could have a viable burstable instance with time-slicing alone.

Re: Downfall Attacks

#88

Post by rocqua »

mike_hearn wrote: post #60
winternewt wrote: post #41

Earlier quoted context omitted.

The Spectre attack had to be patched in the kernel in a way that significantly slowed down execution on Intel CPU:s: https://www.notebookcheck.net/Spectre-v2-mitigation-wreaks-h...

Yes, I think that's what I said? Every attack no matter how deep it seemed to be has been patchable in microcode, sometimes at a cost in performance. But so far nobody had to toss the physical silicon, at least not with Intel. The malleability of these chips is quite fascinating.

The meltdown and spectre mitigations weren't patched in microcode, they were patched by changing the internal calling methods of the kernel.

Re: Downfall Attacks

#89

Post by graton »

buildbot wrote: post #2

This is a huge performance hit - up to 50% it is claimed! 70% of modern intel processors are affected apparently as well.

It is kind of like thinking that it is a huge sale at a store when they say "Up to 70% off". And there are like two things in the whole store which are 70% off.

I am always suspicious of "up to" claims.

Re: Downfall Attacks

#90

Post by tedunangst »

stalfosknight wrote: post #39
SoftTalker wrote: post #25

Earlier quoted context omitted.

I'm not sure what evidence there is to think that Apple's chips are any better. And that's not really a dig at Apple; these are just very complicated devices and especially with the optimizations that CPUs need to make to run today's software with acceptable performance, it can become very hard to foresee all possible attacks and vulnerabilities.

I'm not trying to suggest that Apple's ARM chips are magically better because they're designed by Apple. Rather that the x86 architecture is obviously very long in the tooth and now would be a great time to switch to a far more modern architecture especially in light of this steady stream of vulnerabilities and defects that keep being found in x86. I'm sure ARM64 isn't perfect but I've yet to learn of something as se…

Today you get to learn that there were ARM CPUs affected by Meltdown as well, including those sold by Apple.
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