llfw: Low Level Firewall

This tool adds rules to the macOS pf firewall. The pf firewall has no UI other than pfctl so it works well for fleet-wide low-level security purposes.

Rules are embedded in the file Sources/llfw/Ruleset.swift

• engage - if llfw isn't disabled, will create or overwrite the rule file and load it into pf. It will also retain pf and store the token value at /Library/Application Support/llfw/pfReferenceToken
• disable will unload these rules, release our claim on pf if we had one, and create a touchfile that deactivates future enagage commands. The touchfile is /Library/Application Support/llfw/doNotLoadLLFWRules
• enable removes the touchfile /Library/Application Support/llfw/doNotLoadLLFWRules