this post was submitted on 07 Dec 2025
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Docker security (lemmy.zip)
submitted 8 months ago* (last edited 8 months ago) by jobbies@lemmy.zip to c/selfhosted@lemmy.world
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You're probably already aware of this, but if you run Docker on linux and use ufw or firewalld - it will bypass all your firewall rules. It doesn't matter what your defaults are or how strict you are about opening ports; Docker has free reign to send and receive from the host as it pleases.

If you are good at manipulating iptables there is a way around this, but it also affects outgoing traffic and could interfere with the bridge. Unless you're a pointy head with a fetish for iptables this will be a world of pain, so isn't really a solution.

There is a tool called ufw-docker that mitigates this by manipulating iptables for you. I was happy with this as a solution and it used to work well on my rig, but for some unknown reason its no-longer working and Docker is back to doing its own thing.

Am I missing an obvious solution here?

It seems odd for a popular tool like Docker - that is also used by enterprise - not to have a pain-free way around this.

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[–] GreenKnight23@lemmy.world 1 points 8 months ago (2 children)
  • anyone gaining physical or remote access to the device can set rules. by protecting the entire network with a hardware firewall you mitigate attack vectors from other hardware on your network that become compromised.
  • iptables and firewalld are notorious for locking users out of the system by overzealous or green system admins. in the msp world this happens practically by the hour.
  • iptables and firewalld can be used against you in the event of a breach. one of the first things an attacker may attempt is to forward ports and lock system admins out as they take over the system.
  • make sure you save your rules properly or they'll be gone after a reboot or botched upgrade
  • migrating your rules from one system to another when you're changing hardware or restoring a system is a huge pain in the ass.
  • got a network change that's going to modify the subnet your systems are on? get ready to migrate all 15 of your devices one by one for the next 8-15 hours (depending on the complexity of your rules)

it's far easier, and safer to have all your network config done in the network. from system migrations to securing/hardening. it's far more efficient and effective to have a single source of truth that manages network routing and firewall rules. hell, you can even have a redundant or load balanced firewall configuration if you're afraid of a single point of failure.

point is, firewalld and iptables is for amateur hour and hobbyists.

if you want to complain that "docker doesn't respect system firewalls" then at least have the chutzpah enough to do it the right way from the beginning.

[–] slazer2au@lemmy.world 2 points 8 months ago

None of those speak to the reliability of iptables. They all sound like skill issues.

In 15 years of network engineering iptables has been the simplest part.

A layered approach with hardware firewalls is valid but when those firewalls get popped, looking at you Cisco, Fortinet, and PA you still want host level restrictions.
Your firewall or switch should never be used as a jump host to servers

[–] atzanteol@sh.itjust.works 1 points 8 months ago (1 children)

point is, firewalld and iptables is for amateur hour and hobbyists.

Which is weird for you to say since practically all of the issues you list are mistakes that amateurs and hobbyists make.

[–] GreenKnight23@lemmy.world 1 points 8 months ago (1 children)

this is selfhosted. a community that's predominantly amateur or hobbyist.

[–] atzanteol@sh.itjust.works 1 points 8 months ago (1 children)

But absolutely none of the issues you listed are issues with iptables.

[–] GreenKnight23@lemmy.world 1 points 8 months ago (1 children)

I wouldn't go onto a teen community and spout off how to make explosives even though they're relatively safe to a trained individual.

same reason behind not allowing a hobbyist and amateur community to think that iptables and firewalld is the best/only solution.

it's dangerous and someone will get hurt eventually.

[–] atzanteol@sh.itjust.works 1 points 8 months ago

This is... Pretty stupid. There are things to be careful about but it's pretty straight forward to use iptables.