[theossuary]

I came in expecting not to, but I completely agree with this article. I moved off RHEL after using CentOS exclusively for a decade because of the changes in 2023. I loved SELinux, it's a technology you need to sink your teeth into if you want to understand it, but it has decent tooling (like audit2why) and isn't too hard to modify to get working if needed (SELinux booleans are a powerful way to modify base policies without having to recompile).

I do a lot in Kubernetes, and there's been more than one CVE with a line like "Affects all versions of docker/containerd, unless running SELinux," which gave me a lot of reassurance that the effort put into making SELinux work was worth it.

Now that I'm on Debian, I'm slowly building a new set of policies for the OS. Thankfully SELinux has an excellent reference policy[1] to base off of. I'm hoping my new debian base images for my homelab & elsewhere will have a nice restrictive default SELinux policy by the end of the year. I hope there's more community effort here as well, SELinux really can't compare to AppArmor, and is absolutely necessary for proper security.

Honestly I'd love if the wider community took another stab at replacing SELinux with a KSM that had similar functionality but better tooling and design. I'd pick it up in a heartbeat, but right now SELinux is what we have.

[1]: https://selinuxproject.org/page/NB_RefPolicy

[NewJazz]

I do a lot in Kubernetes, and there's been more than one CVE with a line like "Affects all versions of docker/containerd, unless running SELinux," which gave me a lot of reassurance that the effort put into making SELinux work was worth it.

I've seen this too, but I usually see AA mentioned in the same situations as an equivalent mitigation to SELinux.

[theossuary]

I can't say I've seen the same, so I dug into it. There's a good list from RedHat[1] on CVEs SELinux mitigated. I went through them:

- CVE-2016-9962 - Bypasses Apparmor [2], mitigated by SELinux

- CVE-2022-0492 - Apparmor and Seccomp also protect against

- CVE-2019-5736 - Mixed, blocked by the default SELinux policy in RHEL (not Fedora), not blocked by the default AppArmor policy[3]

- CVE-2021-3156 - This one is not a good one for RedHat to put on the list. SELinux by default doesn't protect against it, Debian 10 at the time had a Linux security feature enabled (fs.protected_symlinks) that helped mitigate it, and additionally CVE-2021-23240 came out which had similar effects but only occurred on SELinux systems.

- CVE-2019-9213 - Not mitigated by AppArmor, mitigated by SELinux

- CVE-2019-13272 - Not mitigated by AppArmor, not mitigated by default SELinux policy, but easy to mitigate by enabling boolean. I'd consider this a win for SELinux, but only just.

While digging into this more, I came across this BlackHat talk[4] which really quantifies how SELinux improves security (though doesn't contrast it with AppArmor). I also came across a paper on usability of SELinux and AppArmor[5] which brings up an interesting point: If the tool is too complex, even if it's more powerful, more often than not it won't end up having better results.

That's all to say, I think if you're willing to invest a lot of time into it (say you want to make security your niche in your development career), SELinux is still the best. But I can see why many may gravitate towards AppArmor so as to not make perfect the enemy of good. That said, I still wish Debian had a choice between the two, right now SELinux isn't really doable without a lot of work.

[1]: https://access.redhat.com/solutions/7032454

[2]: https://github.com/opencontainers/runc/issues/2128

[3]: https://www.cloudfoundry.org/blog/cve-2019-5736/

[4]: https://www.youtube.com/watch?v=EkL1sDMXRVk

[5]: https://researchportal.murdoch.edu.au/esploro/outputs/journa...

[turtle_heck]

I agree SELinux is awesome.

SELinux can be frustrating without the proper background about what it is, how it works, and how it helps you. There is a surprising amount of tooling for it actually.