I'm not saying this specific attack is something to get worked up over. But, as I have already said, writing off an entire class of vulnerabilities because you think it's all theatre is naive. Weighing each exploit against your attack surface, risks, and risk tolerance is not.

>It's security theater specifically because individuals and organizations following these blind mitigation recommendations don't assess the attack surface that's being exposed.

Blaming researchers for security theatre when it is the organizations which are not doing their due diligence is, at least to me, a weird way to look at things.

I wouldn't want Intel or AMD or anyone else to abandon speculative execution, clock boosting, or any other of the "vulnerable" technologies just because their unsafe in specific application spaces, which seems to be what half of HN starts advocating for whenever this stuff comes up.

An application bug like OpenSSH is a completely separate spiritually from the hardware bugs that inspire these mitigation discussions.

The person I replied to asserted that all timing attacks are theatre, which I disagree with (and, evidently, poorly communicated my stance). Perhaps they did not mean the entire class of vulnerabilities which rely on some sort of exploitable timing difference, but only those that require privileged (or physical) access. In that case, I still believe it is foolish to completely dismiss them simply for being a 'timing attack' (and therefor theatre), but I also believe it is foolish to blindly follow mitigation recommendations without analysis.

And then you put 'mitigations=off' in your kernel command line and go on your way. I do it for all my BOINC compute nodes, because they literally have nothing sensitive on them.

But remember, L1TF/Foreshadow could reach across virtual machine boundaries. It's not just inter-process speculation that's a problem.

There's a reason this CVE is classified as medium severity

Probably 90% of PCs are single-user Windows desktops, though. It's a "nonexistent severity" issue for those use cases... yet we all get to pay.

On the other hand, if you're a cloud provider that multiplexes tons of virtual cores on your physical hardware, I suspect anyone trying to do the sort of careful timing analysis required for these types of attacks would find themselves drowning in noise, as their processes get migrated arbitrarily between cores of hardware shared with tons of others.

It's odd, because this agrees with what I wrote, and the parent to your comment says they "fully concur", yet they are arguing that I'm incorrect. I did a poor job in communicating.

As an attempt to better clarify what I wrote: I agree with you that for the vast majority of people this specific attack is a non-issue. But, there are plenty of different timing attacks, and some of those may affect some people. It would follow then that some timing attacks should not be abruptly dismissed simply because it's classified as a timing attack.

However, my initial comment was replying to someone who wrote off the entire class of vulnerabilities, asserting that no timing attack of any variety has been used successfully. I find this a naive approach to vulnerability management. Instead of dismissing all attacks that are classified as timing attacks, vulnerabilities should be assessed for what they can do, the ease of doing it, and the potential impact of a successful attack.

But they just straight up don't run in constant time, so they're vulnerable to a timing attack across the network. That's clearly just a library bug? Like surely the dumbest part of a "constant time" algorithm is double checking that you ran for a constant wall clock amount of time?

It's... hard. A lot of the "constant cache behavior" and "constant time behavior" algorithms were written back in the day when the CPU speeds didn't change randomly on you, or at worst toggled between "idle" and "running hard." Think... oh, even the Core 2 days, really. They didn't switch that fast.

And then the hardware behavior changed out from under the algorithms, and nobody noticed. Now the throttling is far more rapid. So they may still be "constant instruction count," but that no longer implies constant time.

It's... complicated. :( And what's worse, even the people in charge of managing the complexity don't understand all the details anymore. When stuff like this surprises Intel, we've got problems.

While this won't fool timing attacks that are operating on the same machine as your process, the computation time becomes completely opaque to the network which is what the "remote" attacks are built on.