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PSA: Docker nukes your firewall rules and replaces them with its own. (sh.itjust.works)

submitted 8 months ago* (last edited 8 months ago) by [email protected] to c/[email protected]

50 comments fedilink hide all child comments

I use nftables to set my firewall rules. I typically manually configure the rules myself. Recently, I just happened to dump the ruleset, and, much to my surprise, my config was gone, and it was replaced with an enourmous amount of extremely cryptic firewall rules. After a quick examination of the rules, I found that it was Docker that had modified them. And after some brief research, I found a number of open issues, just like this one, of people complaining about this behaviour. I think it's an enourmous security risk to have Docker silently do this by default.

I have heard that Podman doesn't suffer from this issue, as it is daemonless. If that is true, I will certainly be switching from Docker to Podman.

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[–] [email protected] 51 points 8 months ago (1 children)

It doesn’t nuke your rules. Just ads to them.

[–] [email protected] 11 points 8 months ago (1 children)

How come I don't see my previous rules when I dump the ruleset, then? I have my rules written in /etc/nftables.conf, and they were previously applied by running # nft -f /etc/nftables.conf. Now, when I dump the current ruleset with # nft list ruleset, those previous rules aren't there — all I see are Docker's rules.

[–] [email protected] 0 points 8 months ago (1 children)

You can use a bridge network or the host network.

In bridge network it is like a NAT host. With its own firewall settings.

In host network mode, it will just open the port it needs.

[–] [email protected] 1 points 7 months ago

I could be misunderstanding your comment, but you don't seem to have answered my question of why I don't see my rules anymore.