"Invalid HTTP_HOST header" from unknown domain - django

Question

I am using Nginx and Gunicorn to host a Django project. I need to secure this site, and as a test I set up Let's encrypt to an unused domain of mine. While tailing the Django access log, I noticed the following entry from time to time:
Invalid HTTP_HOST header: 'aydinfatih.com'. You may need to add u'aydinfatih.com' to ALLOWED_HOSTS.
This is an unknown domain to me, and while trying to access the domain (it got 400 response), I could se more of these log entries on my server. What is this? Is it related to my SSL-setup, and an indication that it's not secure?
server {
server_name example.com example.com;
location /static/ {
root /home/user/project/django-project;
}
location /media/ {
root /home/user/project/django-project;
}
location / {
include proxy_params;
proxy_pass http://unix:/home/user/project/project.sock;
}
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
if ($scheme != "https") {
return 301 https://$host$request_uri;
} # managed by Certbot
}
server {
listen 80;
server_name my.server.ip.here example.com;
return 301 https://example.com;
}
I added the following to my server block:
if ($host !~* ^(example.com|www.example.com)$ ) {
return 444;
}
The unknown domain now displays 520. Is this the correct way to deal with this? Something else I've missed?

Answer 1

I misread your question. Here's a new answer.
Someone configs their DNS record to point their domain name to your server IP. Adding hostname checking certainly helps, but normally we use a default "catch all" server block to handle all unwanted requests:
# "Catch all" server
server {
server_name _;
return 444;
}
# Your site settings
server {
server_name example.com example.com;
location /static/ {
root /home/user/project/django-project;
}
location /media/ {
root /home/user/project/django-project;
}
location / {
include proxy_params;
proxy_pass http://unix:/home/user/project/project.sock;
}
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
if ($scheme != "https") {
return 301 https://$host$request_uri;
} # managed by Certbot
}
server {
listen 80;
server_name my.server.ip.here example.com;
return 301 https://example.com;
}