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How to secure (podman or docker) containers for public-facing hosting? (lemmy.ml)

submitted 10 months ago* (last edited 10 months ago) by cyclohexane@lemmy.ml to c/linux@lemmy.ml

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Context

I want to host public-facing applications on a server in my home, without compromising security. I realize containers might be one way to do this, and want to explore that route further.

Requirements

I want to run applications within containers such that they

Must not be able to interfere with applications running on host
Must not be able to interfere with other containers or applications inside them
Must have no access or influence on other devices in the local network, or otherwise compromise the security of the network, but still accessible by devices via ssh.

Note: all of this within reason. I understand that sometimes there may be occasional vulnerabilities, like in kernel for example, that would eventually get fixed. Risks like this within reason I am willing to accept.

What I found so far

Running containers in rootless mode: in other words, running the container daemon with an unprivileged host user
Running applications in container under unprivileged users: the container user under which the container is ran should be unprivileged
Networking: The container's networking must be restricted. I am still not sure how to do this and shall explore it more, but would appreciate any resources.

Alternative solution

I have seen bubblewrap presented as an alternative, but it seems like it is not intended to be used directly in this manner, and information about using it for this is scarce.

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[–] sudneo@lemmy.world 7 points 10 months ago (1 children)

You already mentioned the most important things.

I will add, at the cost of being pedantic:

build the image properly, or use good images. This means limit dependencies as much as possible, as minimal images as possible (less updates due to CVEs, less tooling).
do not mount host volumes, if you really have to, use a dedicated subpath owned by the user of the container. Do not use homedirs etc.
do not run in host namespaces, like host network etc. Use port mapping to send traffic to the container.

If you want to go hardcore:

analyze your application, and if feasible, build and use a more restrictive seccomp profile compared to the default. This might limit additional syscalls that might be used during an exploitation but that your app doesn't need.
run falco on the node. Even with the default set of rules (nothing custom), many exploitation or posts-exploitation steps would be caught, such as "shell spawned" etc.

[–] krash@lemmy.ml 2 points 10 months ago (1 children)

Never heard of falco, why would you recommended it over other similar solutions out there?

[–] sudneo@lemmy.world 2 points 10 months ago

It's the de-facto standard for runtime container security (sysdig is based on it). The only competitor afaik is aqua security's tracee, which is way less mature. It is very well supporter, there are tons of rules maintained by the community and it is a CNCF project used by enterprise solutions (I.e., shouldn't disappear overnight).