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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[–] irmadlad@lemmy.world 2 points 8 months ago* (last edited 8 months ago)

So, this discussion has intrigued me and some good points have been brought up by seemingly knowledgeable network engineers of which I am not. If I may, introduce you guys to my network to see if there are points I can improve on.

For simplicity, the network diagram would be: modem---->stand alone pfsense firewall with a tailscale overlay, running Suricata, pfblockerng, vlans to segment server traffic from normal traffic, & a very robust rule set & ntopng for traffic analysis -----> server & devices. Server is piped through Cloudflare Tunnel/Zero Trust. On the server, I run UFW, fail2ban with a hair trigger & Crowdsec. Also, since I am the only user, I lock everything down in the .host Allow/Deny & use ssh keys. Users cause complexities and complexities turn into issues. All devices are running a VPN. I do run Docker in lieu of Podman. Server has been hardened through various means and to an extent in line with Lynis.

I've been told that this is overengineered, but it seems to work just jammy. Knock on wood, I've never had a breach on my local network, though there is always the possibility. A long time ago, when I stood my first server up on a VPS, it got hacked almost immediately. So I dropped back and did some studying, but I am no network engineer.

Anyways, for the experts here, my question is: What would you do to improve, harden, rip out, redo, add etc?

ETA: Server also has a tailscale overlay.