this post was submitted on 22 Jul 2024
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Security and docker (sh.itjust.works)
submitted 4 months ago by [email protected] to c/selfhosted
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How do i you decide whats safe to run

I recently ran Gossa on my home server using Docker, mounting it to a folder. Since I used rootless Docker, I was curious - if Gossa were to be a virus, would I have been infected? Have any of you had experience with Gossa?

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[–] asap 6 points 4 months ago* (last edited 4 months ago) (2 children)

Containers are isolated from the host by default.

Are you certain about that? My understanding is that Docker containers are literally just processes running on the host (ideally rootless), but with no isolation in the way that VMs are isolated from the host.

If you have some links for further reading it would be great, as I have been extremely cautious with my Docker usage so far.

I haven't found anything to refute this, but this post from 2017 states:

In 2017 alone, 434 linux kernel exploits were found, and as you have seen in this post, kernel exploits can be devastating for containerized environments. This is because containers share the same kernel as the host, thus trusting the built-in protection mechanisms alone isn’t sufficient.

If someone exploits a kernel bug inside a container, they exploited it on the host OS. If this exploit allows for code execution, it will be executed on the host OS, not inside the container.

If this exploit allows for arbitrary memory access, the attacker can change or read any data for any other container.

[–] [email protected] 1 points 4 months ago

The Linux kernel recently became a CVE numbering authority. That means that there are now tons of CVEs coming out but the overwhelming majority aren't easily exploitable. They can be rated pretty high with no actual impact. Furthermore, a lot of them require a very specific setup with specific kernel components. It is best to look at the exploitablity score and the recommended CISA actions.

[–] [email protected] 1 points 4 months ago

There is definitely isolation. In theory (if containers worked perfectly as intended) a container can't see any processes from the host, sees different filesystems, possibly a different network interface and basically everything else. There are some things that are shared like CPU, Memory and disk space but these can also be limited by the host.

But yes, in practice the Linux kernel is wildly complex and these interfaces don't work quite as well as intended. You get bugs in permission checks and even memory corruption and code execution vulnerabilities. This results in unintended ways for code to break out of containers.

So in theory the isolation is quite strong, but in practice you shouldn't rely on it for security critical isolation.