Hey they promised to cut the PST though! That 1% buys me uh… uhhhhh… a whole extra coffee every so often!

Yea let’s just give a vulnerable population a free trial of a gambling addiction lol

{“level”:“error”,“ts”:1691499478.2793655,“logger”:“tls.handshake”,“msg”:“getting certificate from external certificate manager”,“remote_ip”:"100

.125.48.40",“remote_port”:“60140”,“sni”:“machine.domain.ts.net”,“cert_manager”:0,“error”:"Get "http://local-tailscaled.sock/localapi/v0/cert/vaulty.tail

a5148.ts.net?type=pair": dial unix /var/run/tailscale/tailscaled.sock: connect: no such file or directory"}

This is your main issue - looks like Caddy can’t access the tailscale socket in order to serve their TLS cert. check you’re running caddy>2.5, check the socket exists and check the user running the caddy process has access to it. docs

Are you running Caddy with docker?

I read your comment in more detail, you’re going down the wrong path. What you’re looking for cannot function the way you want the way you want to achieve it, and may not even make sense to want. I am wrong, I didn’t realize Caddy could just serve their cert over the socket. What user is the caddy process on your VM being run as?

If you want to use Tailscale DNS, you can use their TLS cert (assuming it gives a valid cert for machine.domain.ts.net) and just reverse proxy HTTP traffic with nginx on the VPS/VM (assuming nginx can listen on their network device. I’ve fought with that with openresty before, but that may be because I was trying to host it in another docker container lol).

But, the connection is unsecured over HTTP. I’d like to take it a step further in order to make the connections go over HTTPS.

Why? You’re already VPN’d into a machine you control via tailscale. Protecting the specific application TCP traffic with TLS is kind of redundant at that point. If you really care, just use nginx not Caddy because this will never work using Tailscale DNS, self sign a cert for your Tailscale domain and use nginx to serve traffic on the Tailscale network device.

Also, use docker compose. This will feed DNS records into the containers’ /etc/hosts file as well as put the containers on their own network so the main containers won’t be exposed directly, only caddy.

docker-compose.yml

version: "3.4"
services:
  caddy:
    container_name: caddy
    image: ghcr.io/authp/authp:latest  # I use authp for OAuth authentication instead of VPN-only access
    restart: unless-stopped
    ports:
      - 443:443
      - 443:443/udp
      - 80:80
    volumes:
      - ${ROOT}/config/caddy/Caddyfile:/etc/caddy/Caddyfile
      - ${ROOT}/config/caddy/data:/data/
    dns:
      - 1.1.1.1  # set these to your local DNS if you have one, I run pihole
      - 8.8.8.8
      - 8.8.4.4
  whoami:
    container_name: whoami
    depends_on:
      - caddy
    image: containous/whoami
    restart: unless-stopped

Caddyfile

{
	http_port 80
	https_port 443
}

whoami.example.com{
    reverse_proxy whoami:80
}

As you can see the Caddyfile directs the Caddy container to reverse proxy whoami.example.com to http://whoami:80, which uses the /etc/hosts entry that docker-compose inserts for whoami to the whoami container’s Docker IP address. In this scheme, only Caddy needs to have a port listening on the host machine. Assuming Caddy can access your tailscale network, this will work - for that. (although I worry that Tailscale mounts the network device as a unix socket, which may complicate matters - I ran into this when trying some bullshit with nginx/openresty)

The issue that you’re having in your logs is that you’re trying to get Caddy to get a TLS cert for machine.domain.ts.net, which will never work, because machine.domain.ts.net is not a globally recognized DNS record - it’s a split zone DNS for within the Tailscale network exclusively. LetsEncrypt needs to be able to prove you own machine.domain.ts.net in order to issue a cert for it, meaning it needs to be able to resolve the domain and chat with Caddy. Since LetsEncrypt isn’t on your Tailscale network, it cannot do this.