I have an odd problem with nginx subdomains. First, my configuration:

server {
    listen              443 ssl;
    server_name         secure.example.com;
    ssl_certificate     example.crt;
    ssl_certificate_key example.key;
    keepalive_timeout   70;

    location / {
        fastcgi_pass    127.0.0.1:8000;
        ...
    }
}

server {
    listen              80;
    server_name         example.com www.example.com;

    location / {
        fastcgi_pass    127.0.0.1:8000;
        ...
    }
}

The idea being that I have a secure domain, secure.example.com and a normal domain, example.com. In practice, I can go to https://example.com and http://secure.example.com. I worked around the second issue with an intermediary server:

server {
    listen              80;
    server_name         secure.example.com;
    rewrite     ^(.*)  https://secure.example.com$1 permanent;
}

But this is not an optimal solution and I'd have to create another one to redirect https on the tld to the subdomain. I feel like I must be doing something wrong if I need multiple servers like that. Why does https://example.com work when there is no server listening on 443 there? Shouldn't it just fail to connect? I'm rather confused.