Do you guys expose the docker socket to any of your containers or is that a strict no-no? What are your thoughts behind it if you don’t? How do you justify this decision from a security standpoint if you do?

I am still fairly new to docker but I like the idea of something like Watchtower. Even though I am not a fan of auto-updates and I probably wouldn’t use that feature I still find it interesting to get a notification if some container needs an update. However, it needs to have access to the docker socket to do its work and I read a lot about that and that this is a bad idea which can result in root access on your host filesystem from within a container.

There are probably other containers as well especially in this whole monitoring and maintenance category, that need that privilege, so I wanted to ask how other people handle this situation.

Cheers!

  • chameleon@fedia.io
    3·
    1 day ago

    All true, wanted to add on to this:

    Note that smart peeps say that the docker socket is not safe as read-only.

    That’s true, and it’s not just something mildly imperfect, read-only straight up does nothing. For connecting to a socket, Linux ignores read-only mount state and only checks write permission on the socket itself. Read-only would only make it impossible to make a new socket there. Once you do have a connection, that connection can write anything it wants to it. Traefik and other “read-only” uses still have to send GET queries for the data they need, so that’s happening for legitimate use cases too.

    If you really need a “GET-only” Docker socket, it has to be done with some other kind of mechanism, and frankly the options aren’t very good. Docker has authorization plugins that seem like too much of a headache to set up, and proxies don’t seem very good to me either.

    Or TLDR: :ro or stripping off permission bits doesn’t do anything aside from potentially break all uses for the socket. If it can connect at all, it’s root-equivalent or has all privileges of your rootless user, unless you took other steps. That might or might not be a massive problem for your setup, but it is something you should know when doing it.