How to get Elastic Beanstalk nginx-backed proxy server to auto-redirect from HTTP to HTTPS?

After several false-starts with ideas from Amazon’s paid support, they did come through in the end. The way you get this to work is you configure your environment to respond to both port 80 and 443. Then create a folder in your main Node.js app folder called .ebextensions, and you place a file named 00_nginx_https_rw.config in there, with this text as the contents:

files:
  "/tmp/45_nginx_https_rw.sh":
    owner: root
    group: root
    mode: "000644"
    content: |
      #! /bin/bash

      CONFIGURED=`grep -c "return 301 https" /etc/nginx/conf.d/00_elastic_beanstalk_proxy.conf`

      if [ $CONFIGURED = 0 ]
        then
          sed -i '/listen 8080;/a \    if ($http_x_forwarded_proto = "http") { return 301 https://$host$request_uri; }\n' /etc/nginx/conf.d/00_elastic_beanstalk_proxy.conf
          logger -t nginx_rw "https rewrite rules added"
          exit 0
        else
          logger -t nginx_rw "https rewrite rules already set"
          exit 0
      fi

container_commands:
  00_appdeploy_rewrite_hook:
    command: cp -v /tmp/45_nginx_https_rw.sh /opt/elasticbeanstalk/hooks/appdeploy/enact
  01_configdeploy_rewrite_hook:
    command: cp -v /tmp/45_nginx_https_rw.sh /opt/elasticbeanstalk/hooks/configdeploy/enact
  02_rewrite_hook_perms:
    command: chmod 755 /opt/elasticbeanstalk/hooks/appdeploy/enact/45_nginx_https_rw.sh /opt/elasticbeanstalk/hooks/configdeploy/enact/45_nginx_https_rw.sh
  03_rewrite_hook_ownership:
    command: chown root:users /opt/elasticbeanstalk/hooks/appdeploy/enact/45_nginx_https_rw.sh /opt/elasticbeanstalk/hooks/configdeploy/enact/45_nginx_https_rw.sh

Amazon’s support team explained: This config creates a deployment hook which will add the rewrite rules to /etc/nginx/conf.d/00_elastic_beanstalk_proxy.conf.

(Previously they had offered me .config’s that copied separate files into /etc/nginx/conf.d, but those either had no effect, or worse, seemed to overwrite or take precedence over the default nginx configuration, for some reason.)

If you ever want to undo this, i.e. to remove the hooks, you need to remove this ebextension and issue a command to remove the files that it creates. You can do this either manually, or via ebextensions commands you put in place temporarily:

/opt/elasticbeanstalk/hooks/appdeploy/enact/45_nginx_https_rw.sh
/opt/elasticbeanstalk/hooks/configdeploy/enact/45_nginx_https_rw.sh

I haven’t tried this, but presumably something like this would work to remove them and undo this change:

container_commands:
  00_undochange:
    command: rm /opt/elasticbeanstalk/hooks/appdeploy/enact/45_nginx_https_rw.sh
  01_undochange:
    command: rm /opt/elasticbeanstalk/hooks/configdeploy/enact/45_nginx_https_rw.sh

Hope this can help someone else in the future.