How to set up HTTPS for your website using Cloudflare’s SSL certificate and Nginx.

In this case, I'll use my website as an example.

Step 1: Set Up Cloudflare

Sign Up/Login to Cloudflare:
- Go to the Cloudflare website.
- Sign up for a new account or log in to your existing account.
Add Your Site:
- After logging in, click on the “Add a Site” button.
- Enter your domain name (e.g., fudongs.com) and click “Add Site”.
Choose a Plan:
- Select a plan. You can start with the free plan which provides basic SSL/TLS and CDN features.
- Click “Continue”.
Update DNS Settings:
- Cloudflare will scan your DNS records. Review and confirm that all records are correct.
- Click “Continue”.
- Cloudflare will provide you with nameservers. You need to update your domain’s nameservers to these Cloudflare nameservers.
- Log in to your domain registrar (e.g., GoDaddy, Namecheap) and update the nameservers to the ones provided by Cloudflare.
- Once done, go back to Cloudflare and click “Continue”.

Step 2: Enable SSL/TLS in Cloudflare

Navigate to SSL/TLS:
- In the Cloudflare dashboard, go to the “SSL/TLS” section.
Choose SSL/TLS Mode:
- Select the SSL/TLS mode. The recommended option is “Full” or “Full (Strict)” if you already have an SSL certificate on your origin server.
  - Flexible: Encrypts traffic between the browser and Cloudflare.
  - Full: Encrypts traffic between the browser and Cloudflare, and between Cloudflare and your origin server using a self-signed certificate.
  - Full (Strict): Encrypts traffic between the browser and Cloudflare, and between Cloudflare and your origin server using a valid SSL certificate.

Step 3: Create a Cloudflare Origin Certificate

Create Certificate:
- In the Cloudflare dashboard, navigate to SSL/TLS -> Origin Server.
- Click on "Create Certificate".
- Choose "Let Cloudflare generate a private key and a CSR".
- Select the domain you want to secure (e.g., fudongs.com and *.fudongs.com for the wildcard).
- Click “Next”.
Save the Certificate and Private Key:
- Copy the Origin Certificate and Private Key provided by Cloudflare and save them to your server.

Step 4: Configure Nginx to Use Cloudflare’s Certificate

Save the Certificate and Private Key:
- Save the Origin Certificate to a file on your server, e.g., /etc/ssl/certs/cloudflare_origin.pem.
- Save the Private Key to a file on your server, e.g., /etc/ssl/private/cloudflare_origin.key.

Edit Nginx Configuration:

Open your Nginx configuration file for your site. This is usually found in /etc/nginx/sites-available/fudongs.com.
```
sudo nano /etc/nginx/sites-available/fudongs.com
```

Update the configuration to include SSL settings:

server {
    listen 80;
    server_name fudongs.com www.fudongs.com;
    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl;
    server_name fudongs.com www.fudongs.com;

    ssl_certificate /etc/ssl/certs/cloudflare_origin.pem;
    ssl_certificate_key /etc/ssl/private/cloudflare_origin.key;

    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_prefer_server_ciphers on;
    ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384;

    root /var/www/fudongs.com/html;
    index index.html index.htm index.nginx-debian.html;

    location / {
        try_files $uri $uri/ =404;
    }
}

Test and Reload Nginx:
- Test the configuration for syntax errors:
```
sudo nginx -t
```
- Reload Nginx to apply the changes:
```
sudo systemctl reload nginx
```

Step 5: Verify HTTPS

Check in Browser:
- Open your website in a browser and verify that it loads over HTTPS.
Verify Certificate:
- Use a tool like SSL Labs to verify your SSL certificate and configuration.

Additional Security (Optional)

HTTP Strict Transport Security (HSTS):

Add HSTS to enforce HTTPS:

add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;

Redirect All Traffic to HTTPS:
- Ensure all HTTP traffic is redirected to HTTPS. This is already included in the configuration above with the return 301 https://$host$request_uri; directive in the port 80 server block.

By following these detailed steps, you should be able to successfully set up HTTPS on your website using Cloudflare’s SSL certificate and Nginx.