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Square Enix invests in Linux distribution
(www.gamingonlinux.com)
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this post was submitted on 03 Sep 2024
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Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
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It's bazzite with a custom UI instead of Steam Big Picture and no desktop mode. Their big claim seems to be that they say that they have solved anti cheat on Linux: the system generates a checksum of the kernel space, the anti cheat then compares this checksum with the one on file. No custom kernel module needed on the part of the anti cheat dev. At least in theory.
I'm having a hard time understanding how this would work. udev will load kernel modules depending on your hardware, and these modules run in kernel space. Is there an assumption that a kernel module can't cheat? Or do they have a checksum for each possible kernel module that can be loaded?
Also, how do they read the kernel space code? Userspace can't do this afaik. Do they load a custom kernel module to do this? Who says it can't just be replaced with a module that returns the "right" checksum?
Here is the quote I paraphrased in my comment (I'm sure I got something wrong):
https://www.theverge.com/2024/3/19/24106356/playtron-explains-how-immutable-file-systems-are-not-but-could-help-with-linux-anti-cheat
Ah, so they don't actually say that they read kernel space. They check the version of all installed packages and checksum the installed DLLs/SOs.
If the user still has root privileges, this may still not prevent sideloading of kernel modules. Even if it would detect a kernel module that has been sideloaded, I believe it's possible to write a kernel module that will still be resident after you unload it. This kernel module can then basically do anything without the knowledge of userspace. It could for example easily replace any code running in userspace, and their anticheat would miss that as it doesn't actually check what code is currently running. Most simply, code could be injected that skips the anticheat.
Of course, in their model, if a user isn't given root privileges it seems much harder to do anything, then probably the first thing you'd want to look for is a privilege escalation attack to obtain root privileges. This might not be that hard if they for example run Xorg as it isn't known to be the most secure - there's a reason there's a strong recommendation to not run any graphical UI on servers.
Another way if you don't have root is to simply run the code on a system that does but that does have such a kernel module - or perhaps modify the binary itself to skip the anticheat. I don't see anything preventing that in their scheme.