add security headers to nginx (fixes #208)

ansible/templates/nginx.conf

@@ -16,7 +16,35 @@ server {
     ssl_certificate /certs/live/{{ domain }}/fullchain.pem;
     ssl_certificate_key /certs/live/{{ domain }}/privkey.pem;
 
-    # TODO: add security params
+    # Various TLS hardening settings
+    # https://raymii.org/s/tutorials/Strong_SSL_Security_On_nginx.html
+    ssl_protocols TLSv1.2 TLSv1.3;
+    ssl_prefer_server_ciphers on;
+    ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256';
+    ssl_session_timeout  10m;
+    ssl_session_cache shared:SSL:10m;
+    ssl_session_tickets off;
+    ssl_stapling on;
+    ssl_stapling_verify on;
+
+    # Hide nginx version
+    server_tokens off;
+
+    # Enable compression for JS/CSS/HTML bundle, for improved client load times.
+    # It might be nice to compress JSON, but leaving that out to protect against potential
+    # compression+encryption information leak attacks like BREACH.
+    gzip on;
+    gzip_types text/css application/javascript;
+    gzip_vary on;
+
+    # Only connect to this site via HTTPS for the two years
+    add_header Strict-Transport-Security "max-age=63072000";
+
+    # Various content security headers
+    add_header Referrer-Policy "same-origin";
+    add_header X-Content-Type-Options "nosniff";
+    add_header X-Frame-Options "DENY";
+    add_header X-XSS-Protection "1; mode=block";
 
     location / {
         rewrite (\/(user|u|inbox|post|community|c|login|search|sponsors|communities|modlog|home)+) /static/index.html break;