Important Security Note
Please note that Firefly Field Day Logger does NOT have the required web application security to run over the public Internet. FFDL is intended to be a lightweight application for local use at a Field Day operation over a local LAN/WiFi connection with a group of well-behaved, well-meaning operators. It does not contain any authentication security, serious input sanitization, or significant anti-XSS protections.
If you feel like you MUST implement this over the Internet, the best I can suggest is that the server implements HTTP Basic Authentication at the server-level. However DO NOT plan to actually do this - it is not recommended.
HTTPS / TLS Considerations
As the web evolves, the reliability of using cookies with sites not using the https:// (i.e. TLS-encrypted) connections is becoming problematic. It is strongly recommended that the server is configured to offer https:// connections and clients use those connections. There are known issues with stock Chromium on Linux with non-TLS-protected cookies. Here's how to enable https:// connections for this application.
Test the TLS configuration by visiting the server on https://. For example if the hostname is logger.fd.local, browse to https://logger.fd.local. A warning about a certificate error will appear because the configuration is using the default "fake" certificate. This is OKAY for non-Internet-connected purposes. Accept the error and select the browser's equivalent of "trust this site" or "continue anyway" or "accept the risk and continue". The site should load.
It is strongly recommended to enable HTTPS/TLS on all Firefly Logger installations to avoid potential cookie problems.