cross-posted from: https://programming.dev/post/39212874

I recently migrated my services from rootful docker to rootless podman quadlets. It went smoothly, since nothing I use actually needs to be rootful. Well, except for caddy. It needs to be able to attach to privileged ports 80 and 443.

My current way to bypass it is using HAProxy running as root and forwarding connections using proxy protocol. (Tried to use firewalld but that makes the client IP opaque to caddy.) But that adds an extra layer, which means extra latency. It’s perfectly usable, but I’d like to get rid of it, if possible.

I’m willing to run caddy in rootful podman if needed. But from what I understand, that means I can’t have it in the same rootless network as my other containers. I really don’t wanna open most of my containers’ ports, so that’s not an option.

So, I’m asking whether any of these three things are possible.

  1. Use firewalld to forward ports to caddy without obscuring the client’s IP.
  2. Make rootful caddy share a network with other rootless containers.
  3. Assign privileged ports to caddy somehow, in rootless mode. (I know there’s a way to make all these ports unprivileged, but is it possible to only assign these 2 ports as unprivileged?)

Or maybe there’s a fourth way that I’m missing. I feel like this is a common enough setup, that there must be a way to do it. Any pointers are appreciated, thanks.

  • El_Quentinator@lemmy.worldEnglish
    5·
    2 days ago

    You can use rootless caddy via systemd socket activation, here’s a basic setup:

    1. rootless-caddy.service
    [Unit]
Description=rootless-caddy

Requires=rootless-caddy.socket
After=rootless-caddy.socket

[Service]
# a non root user here
User=El_Quentinator
ExecStart=podman run --name caddy --rm -v [...] docker.io/caddy:alpine

[Install]
WantedBy=default.target
    1. rootless-caddy.socket
    [Socket]
BindIPv6Only=both

### sockets for the HTTP reverse proxy
# fd/3
ListenStream=[::]:443

# fdgram/4
ListenDatagram=[::]:443

[Install]
WantedBy=sockets.target
    1. Caddyfile
    {$SITE_ADDRESS} {
        # tcp/443
        bind fd/3 {
                protocols h1 h2
        }
        # udp/443
        bind fdgram/4 {
                protocols h3
        }
        [...]
}

    And that’s it really.

    You can find a few more examples over here: https://github.com/eriksjolund/podman-caddy-socket-activation

    Systemd socket activation has a few more interesting advantages on top of unlocking binding priviliged ports:

    • allowing to not bind any port on the container, which itself allows to use --network none while still being able to connect to it via systemd socket, pretty neat to expose some web app while completely cutting its own external access.
    • getting rootful networking performance
    • starting up your service only when connecting to it (and potentially shutting it back down after some time)

    Drawbacks is that the file descriptor binding is a bit awkward and not always supported (caddy/nginx/haproxy do support it though). And that podman pods / kube do not support it (or at least not yet).

    • SinTan1729@programming.devOPEnglish
      1·
      2 days ago

      It seems that I’d still need to modify net.ipv4.ip_unprivileged_port_start=80 in sysctl, which I don’t want to do. If I do it, the socket isn’t even strictly necessary.

      • El_Quentinator@lemmy.worldEnglish
        2·
        2 days ago

        TBH I haven’t played with passing caddy’s podman network to other containers, mine is a simple reverse proxy to other standalone containers but not directly connected via podman run --network (or quadlet network). In my scenario I can at least confirm that net.ipv4.ip_unprivileged_port_start doesn’t need to be modified, the only annoyance is that I cannot use a systemd user service, even though the end process doesn’t run as root.

        EDIT: Actually looking at the examples a bit more closely I think the primary difference with my setup is that the systemd socket is started with systemd --user which thus requires the sysctl change, whereas I’m not using a systemd user service, relying instead on User=some-non-root-user to use rootless podman, but requiring root privileges to manage the systemd service.