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Context: Docker bypasses all UFW firewall rules (lemmy.world)
submitted 1 year ago* by to c/programmer_humor@programming.dev
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Docker docs:

Docker routes container traffic in the nat table, which means that packets are diverted before it reaches the INPUT and OUTPUT chains that ufw uses. Packets are routed before the firewall rules can be applied, effectively ignoring your firewall configuration.

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[–] 11 points 1 year ago (2 children)

Somehow I think that's on ufw not docker. A firewall shouldn't depend on applications playing by their rules.

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  • [–] [S] 18 points 1 year ago (3 children)

    ufw just manages iptables rules, if docker overrides those it's on them IMO

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  • [–] 10 points 1 year ago (2 children)

    Feels weird that an application is allowed to override iptables though. I get that when it's installed with root everything's off the table, but still....

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  • [–] 6 points 1 year ago (2 children)

    Linux lets you do whatever you want and that's a side effect of it, there's nothing preventing an app from messing with things it shouldn't.

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  • [–] 6 points 1 year ago

    Not really.

    Both docker and ufw edit iptables rules.

    If you instruct docker to expose a port, it will do so.

    If you instruct ufw to block a port, it will only do so if you haven't explicitly exposed that port in docker.

    Its a common gotcha but it's not really a shortcoming of docker.

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  • [–] 7 points 1 year ago

    Docker spesifically creates rules for itself which are by default open to everyone. UFW (and underlying eftables/iptables) just does as it's told by the system root (via docker). I can't really blame the system when it does what it's told to do and it's been administrators job to manage that in a reasonable way since forever.

    And (not related to linux or docker in any way) there's still big commercial software which highly paid consultants install and the very first thing they do is to turn the firewall off....

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