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Fed-up Torvalds suggests disabling AMD’s 'stupid' performance-killing fTPM RNG
(www.theregister.com)
this post was submitted on 01 Aug 2023
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Linux
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TPM is basically never for your benefit. It's becoming a requirement because Microsoft is going to one day say "you can only run apps installed from the Windows Store, because everything else is insecure" and lock down the software market. Valve knows this which is why they're going so hard on the Steam Deck and Linux.
You're going to need a TPM or some other security key if you want to come close to the security Bitlocker's and Apple's T2 chip provide. TPM+password encryption is the norm on any serious attempts at data protection, for good reason.
It's already quite hard to get decent encryption on most Linux distros, with GRUB lacking support for modern key derivation techniques for full disk encryption, and several distros still relying on unencrypted boot partitions that anyone can modify the initrd of without any trace.
Secure boot can protect all of these steps without TPM encryption if you bother to set up your own keys, kick out Microsoft's keys (killing any chance of a successful dual boot), and set up automatic signing of your bootloader and every intermediate step, but that's more than any common Linux user is willing to go through. For Secure Boot to work well you'll probably also want some kind of verification that the system didn't just modify its environment and chainloaded the Linux bootloader and TPMs are the only way to do that on many systems.
"TPM bad" is as bad a take as "Linux bad". The technology isn't inherently good or bad, and both good and bad actors can use it to their advantage, just like the Linux kernel is used in portable hacking devices and in firewalls alike. You can make a problem out of the signed firmware and backdoors and such, but unless you're running a Pentium II or a RISC-V chip that probably runs at the same speeds, you're stuck with some kind of binary blob of microcode and firmware on any computer anyway; TPMs don't add or remove anything from that.
This is why I keep my initrd tattooed as a barcode on my testicles.
"Please teabag the web cam to boot."
There's two types of users, those who write a detailed precise technical answer to the subject, and then there's you
You know, I've been thinking about what I want my first tattoo to be for months, you've just given me a great idea
Kernel upgrades are very... Painful.
I don't know why I keep hearing of security measures to stop someone sleuthing into bootloaders.
Am I the only person using Linux who isn't James Bond?
The thing is, Windows does this out of the box. So does macOS. So do iOS and Android. When you set a PIN on Windows 11 or even add an extra password to your already TPM-encrypted hard drive, you don't even know you're getting any of this security. You don't need to! It just works!
Linux is the only system that doesn't just make this stuff work out of the box. There are some issues that prevent it from being as easy to use as on other systems (the fact that loading Linux keys into a motherboard take an extra user interaction, for example) but there are solutions to all of these problems if Linux distros were to put some work into it.
There's absolutely no reason why you should need to use the terminal to configure the TPM, you should just need to tick a box during install that makes the system use better encryption (or disable it if you use the drive in multiple computers). The reason you need to play James bond with layers of encryption and boot configurations is that standard Linux tooling had awful support for using the security hardware that every computer sold the last decade or so already contains.
I’m an engineer with trade secrets on his laptop. I’ve heard of dozens of people getting laptops stolen from their cars that they left for like ten or fifteen minutes.
The chances are slims, but if it happens I’m in deep trouble whether those secrets leak of not. I’m not taking the risk. I’m encrypting my disk.
It’s not like there’s a difference in performance nowadays.
so you never caught a team of government officials in your living room brute forcing your bootloader at 4am as you got up to use the bathroom, huh. Lucky guy.
TPM bad, put your secrets on a proper encryption peripheral, like a smartcard running javacardOS
TPM will turn into cpu-bound DRM, the more you use it, the more this cancer will grow
Intel literally removed CPU-bound DRM from their recent processors because it wasn't secure. Besides, the encryption keys for DRM are safely stored deep inside the iGPU anyway. All the TPM does is store a few kilobytes of cryptographic data and record signals sent to it by the OS in a way that the OS can't alter down the line.
The TPM is literally built to be used as an encryption peripheral. You can use alternatives like Yubikeys as external TPMs for extra security of course, but that doesn't mean every desktop, laptop, and smartphone needs one.
Your smartcard has the exact same potential to become used as a means for DRM. In standard use cases it's literally meant to govern access to a computer.
Today I learned that I actually set up secure boot properly. Neat!
https://hothardware.com/news/steam-deck-tpm-support-install-windows-11
I mean I generally agree with you, but the SteamDeck runs on an AMD processor with a fTPM that Valve slowly added support for.
It seems unlikely Valve will ever make Windows the primary OS for their devices. And they'd lose a lot of user support if they ever required the TPM for their own software, so hopefully they wouldn't risk it.
Why does everybody seem to think that userspace attestation is the only use for the TPM? The primary use is for data to be encrypted at rest but decrypted at boot as long as certain flags aren't tripped. TPM is great for the security of your data if you know how to set it up.
Valve is never going to require TPM attestation to use Steam, that's just silly. Anti-cheat companies might, but my suggestion there is to just not play games that bundle malware.
Whatever is touted as the primary use doesn't matter as much as what anti-user features it enables.
Anti-user features which are enabled by games and programs that were already anti-user before this. Hardly worth getting upset about, nothing has really changed. You already should have been avoiding them, because they were already anti-user.
I like to think that Valve knows better than to try that.
Support for old software is now the only reason to use windows.
I'm a big fan of Linux, but I can't believe you really think this.
I legitimately have not booted into windows for years.
Sadly, I agree. I'm at the point now where as long as I'm not trying to game I can thrive on Linux. But even then I spend way more time than necessary getting things to work that do so out of the box on Windows. We have a long way to go before legacy apps is the only reason to run it.
Personally I found the time I saved from not having any control over my system has more than made up for tinkering that I have to do to get things running. My laptop would regularly become unusable for 20+ minutes on windows because of disk performance issues, and I as the user had no means to prevent windows from running the service that locked everything up. That along with other times windows just decides your use case is less important have added up to far more time then having to debug a game here and there
Ungh, yeah I used to have that problem with my laptop when I was in college.
I only booted it up for classes unless I had a test coming up I needed to study for or something. Because why the fuck would I not do that - I had a regular computer at home for everything else.
Every couple weeks, that meant it was updating instead of being available for note taking, and usually for the entire hour I needed it. Because apparently setting the updates to run during shutdown wasn’t good enough, they needed to be run on boot, because fuck you that’s why.
Linux is just.. hey I should probably update this shit at some point… meh, tomorrow.
Oh it also loves to install updates on shut down. So when you need to leave the class room to go home that fucking thing tells you to not cut power because it needs to install shit. Fuck you, I need to catch my bus!
The people that prefer Windows for gaming are not the people that will have performance issues on an OS basis, their rig is powerful enough to run complex games, the OS based performance loss is negligible in comparison. Hell, I sometimes don't reboot the work computer for days and it doesn't freeze at all. The system is on an SSD and there are no hiccups nor disk performance issues. In any case, with current day prices, buying a new m2 stick and new ram is less than 100€ total, and to be honest, I'd rather pay that and be fine for 4-5 years than spend a big part of my free time trying to make witcher 3, baldur's gate 3, path of exile, tons of steam games and league working perfectly for Linux. It's just not worth it.
I use WSL for work because coding in a Linux environment is better but I still need access to office tools, because companies work with those tools.
Linux won the servers war, but it still has to do much to win the home/work computer war.
We use the TPM pretty extensively with no Windows in the environment.
You do realize that he is talking about a RNG gen and not the TPM?
It is talking about the RNG built into the fTPM.