Update site-defaults.conf (#3780)

data/conf/nginx/includes/site-defaults.conf

@@ -4,8 +4,9 @@
   override_charset on;
 
   ssl_protocols TLSv1.2 TLSv1.3;
-  ssl_ciphers ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384;
-  ssl_prefer_server_ciphers off;
+  ssl_prefer_server_ciphers on;
+  ssl_ciphers ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305;
+  ssl_ecdh_curve X25519:X448:secp384r1:secp256k1;
   ssl_session_cache shared:SSL:50m;
   ssl_session_timeout 1d;
   ssl_session_tickets off;