341–350 of 378 posts
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Under what circumstances is this not a medium? The only case this applies is if you have public runners running completely untrusted code, and if you're doing that I hope you're doing it on EPYC, which is fixed. And if you're doing that, you're probably mining crypto for randoms.
What about running JavaScript on a browser?
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The problem is, VMs aren't really "Virtual Machines" anymore. You're not parsing opcodes in a big switch statement, you're running instructions on the actual CPU, with a few hardware flags that the CPU says will guarantee no data or instruction overlap. It promises! But that's a hard promise to make in reality.
> you're running instructions on the actual CPU Just how many times is the average operating system workload (with or without a virtual machine also running a second average operating system workload) context switching a second? Like... unless I'm wrong... the kernel is the main process, and then it slices up processes/threads, and each time those run, they have their own EAX/EBX/ECX/ESP/EBP/EIP/etc. (I know it's RAX…
A nice way of thinking about it is the kernel visualizes the CPU among multiple programs.
Great reading material on all this OS stuff: https://pages.cs.wisc.edu/~remzi/OSTEP/
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Yes but the Firecracker VMs are pinned to specific cores. So no two tenants never share a CPU core. Other than Rowhammer, has there been a hardware vulnerability of this nature that has worked x-core? I don't recall. Still, I think that if your company is handling user data it's worth seriously considering dedicated instances for any service that encounters plaintext user information.
Interesting. Physical cores or SMT virtual cores? Is there a link to their docs about this?
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Eric Brandwine (VP/DE @ AWS) said publicly in 2019 that EC2 had never scheduled different tenants on the same physical core at the same time, even before we learned about these kinds of side-channel attacks. https://www.youtube.com/watch?v=kQ4H6XO-iao&t=2485s
Yes (lowest vCPU seems to be 2 everywhere), and that protects against this attack. However, this thread was talking about airgapping hosts, which is needed for the general threat of VM escapes.
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Yes (lowest vCPU seems to be 2 everywhere), and that protects against this attack. However, this thread was talking about airgapping hosts, which is needed for the general threat of VM escapes.
At least Fargate and Lightsail can select < 2 vCPU. (and maybe micro EC2 instance types?)
As usual, cost is the biggest hindrance to security.
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What about running JavaScript on a browser?
I am very doubtful that there exists any JavaScript that compiles to the specific instructions needed for this exploit.