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

submitted 9 months ago* (last edited 9 months ago) by [email protected] to c/[email protected]

47 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] 2 points 9 months ago (1 children)

Option to disable this behavior would be 100x better then current, but what do I know lol

Prevent docker from manipulating iptables

Don't know what it's actually doing, I'm just learning how to work with nftables, but I saved that link in case oneday I want to manage the iptables rules myself :)

[–] [email protected] 1 points 9 months ago (1 children)

Good luck. Your going to have to change the rules whenever the up address of the container changes.

[–] [email protected] 1 points 9 months ago* (last edited 9 months ago)

If you are talking about the IP address then just add a static address, no? I do it anyway in my docker compose:

...
    networks:
      traefik.net:
        ipv4_address: 10.10.10.99

networks:
    traefik.net:
      name: traefik-net
      external: true

I'm not an expert so maybe I'm wrong, if so do not hesitate to correct me !

EDIT: If the IP address doesn't change, you do not need to change to routing and iptables/nftables rules. ??