this post was submitted on 09 Nov 2023
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How do you protect yourself against malicious docker containers / projects? (alien.top)
submitted 1 year ago by Simplixt@alien.top to c/main@selfhosted.forum
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Hi all,

as I'm running a lot of docker containers in my "self-hosted cloud", I'm also a little bit worried about getting malicious docker containers at some points. And I'm not a dev, so very limited capabilities to inspect the source code myself.

Not every docker container is a "nextcloud" image with hundred of active contributors and many eyes looking at the source code. Many Self-Hosted projects are quite small, and Github accounts can be hacked, etc. ...

What I'm doing in the moment, is:

Project selection:
- only select docker projects with high community activity on GitHub and a good track record

Docker networks:
- use separate isolated networks for every container without internet access
- if certain APIs need internet access (e.g. Geolocation data), I use an NGINX-proxy to forward this domain only (e.g. self-made outgoing application firewall)

Multiple LXC containers:
- I split my docker containers into multiple LXC instances via Proxmox, some senitive containers like Bitwarden are running on their own LXC instance

Watchtower:
- no automatic updates, but manual updates once per month and testing afterwards

Any other tips? Or am I worrying too much? ;)

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[–] Not_your_guy_buddy42@alien.top 1 points 1 year ago

It's funny how as a self-hoster with no open ports, sort of supply chain attacks are almost my biggest worry... Here's the tidbits I've collected so far, but just getting into this so take it with a grain of salt ...

  1. working out how to run my containers as non-root... Most support this already. It's adding a user:UID:GID in the compose file and making sure that user can read and write to any dirs you want to map, and it's done. Now whatever runs in the container does not have root and less chance of shenanigans in its container and on the host.
    Some smaller projects, you have to tweak or rebuild.*
  2. If I can manage I'll also run the docker daemon as rootless as the next milestone. I already had this working on Proxmox Ubuntu VM, but could not get it to work on a netcup VPS, for example.
  3. Docker sock proxy
  4. VLANs
  5. in compose files, if the containers can handle it:
    security_opt:
    - no-new-privileges:true
    cap_drop:
    - ALL
  6. (I have to work out the secrets stuff! secrets in files, ansible vault,...)

(* One example for non-rootifying a docker, I got tempo running as non root the other night as it is based on a nginx alpine linux image, after a while I found a nginx.conf file online where all the dirs are redirected to /tmp so nginx can still run if a non-root user launches it. Mapped that config file to the one in the container, set it to run as my user and it works. Did not even have to rebuild it.)