Problem with newly added subdomain is automatically redirect to SSL

I’m having the same issue.

1. Initial Server Setup with Ubuntu 16.04
	1. How to Use SSH Keys with DigitalOcean Droplets
	2. Community Post: Updating Ubuntu (14.04) -- Security Updates
2. How to Install Nginx on Ubuntu 16.04
3. How to Set Up Nginx Server Blocks on Ubuntu 16.04
4. How to Install Node.JS on Ubuntu 16.04

Installed in the following order above, all DigitalOcean articles. I’m stuck on #3 because my test subdomain keeps rerouting to https as well. I’ve combed through everything I can think of, from DNS settings to nginx.conf and sites-available/enabled and default_server.

How does your HTTP (80) server block for example.com looks like? Make sure server_name is set only to example.com www.example.com. If there is _ or wildcard entry *.example.com make sure to change it to example.com www.example.com. This is example how it should look like:

server {
    listen 80 default_server;
    listen [::]:80 default_server;
    server_name example.com www.example.com;
    return 301 https://$server_name$request_uri;
}

Setup one block that will serve some static content for sub.example.com. You can take a look at Server blocks tutorial if it comes to help. You can share config here so we can look at it.

Heya,

Just an update on an older topic in case anyone finds it

The behavior you’re observing, where http://sub.example.com automatically redirects to https://sub.example.com, even though you haven’t explicitly set up SSL for the subdomain, could be due to a few reasons. Let’s explore these and the steps you can take to troubleshoot and resolve the issue:

1. Check Existing Nginx Configuration

First, carefully review your Nginx configuration files for any global or server-level redirect rules that might be causing this behavior:

• Look for any return 301 https://$server_name$request_uri; or similar redirect statements in your Nginx config files.
• The configuration files are typically located in /etc/nginx/sites-available/ and linked to /etc/nginx/sites-enabled/.

2. HSTS (HTTP Strict Transport Security)

If you have previously visited https://example.com and your server includes an HSTS header, your browser remembers to automatically use HTTPS for all subdomains:

• Check your Nginx configuration for a line like add_header Strict-Transport-Security "max-age=...";.
• If HSTS is set with the includeSubDomains directive, it will apply to all subdomains, including sub.example.com.
• Clearing your browser’s cache or using a different browser/device that hasn’t accessed example.com yet can help determine if this is the cause.

3. SSL Certificate Configuration

Sometimes, the SSL configuration can cause automatic redirection if it’s set up to include subdomains:

• Check the SSL certificate used for example.com to see if it’s a wildcard certificate or includes sub.example.com as an alternate name.

4. DNS Caching

DNS caching might lead your requests to an old configuration:

• Ensure your DNS records are properly set up for sub.example.com.
• Clear your local DNS cache or wait for the DNS changes to propagate.

5. Client-Side Caching

Browsers often cache 301 redirects aggressively:

• Try accessing http://sub.example.com using a different browser or incognito mode to see if the issue persists.
• Clear your browser cache.

6. Nginx Virtual Host Configuration for Subdomain

Ensure your Nginx server block for the subdomain is correctly set up:

• Create a separate server block for sub.example.com.
• Do not include SSL configuration or redirection rules in this block if you wish to serve it over HTTP.

Example configuration for sub.example.com:

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

    root /path/to/subdomain/root;
    index index.html;

    # Other necessary configurations
}

7. Nginx and System Logs

• Check the Nginx access and error logs (/var/log/nginx/access.log and /var/log/nginx/error.log) for any entries related to sub.example.com.
• System logs (/var/log/syslog) may also provide insights.

8. Nginx Reload

After making changes to your Nginx configuration files, reload Nginx to apply them:

sudo nginx -t
sudo systemctl reload nginx