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Catsplash

Introduction

Catsplash is a captive portal written in Go, designed for resource-constrained Linux environments. Its purpose is to manage Internet access on temporary WiFi networks, blocking traffic from unauthenticated clients and releasing it once they accept the portal terms.

How it works

Section titled “How it works”
  1. A client connects to the WiFi hotspot.
  2. When browsing, their HTTP request is intercepted by iptables.
  3. Catsplash redirects the client to the welcome portal.
  4. The user accepts the terms and Catsplash releases their traffic.
  5. Sessions expire by absolute time or inactivity.

Why Catsplash?

Section titled “Why Catsplash?”
  • Minimalist: A single Go binary. No external dependencies beyond iptables and SQLite.
  • Efficient: Under 25 MB RAM at peak load.
  • Deterministic: Firewall rules are injected and cleaned atomically.
  • Portable: Cross-compiled for amd64, 386, arm64 and armv7.
  • Tested: Network namespace simulation suite for concurrency and stability validation.

Limitations

Section titled “Limitations”
  • Works on Linux only with iptables and root access.
  • HTTPS interception is not implemented as a production solution.
  • No advanced web admin panel (CLI only).
Section titled “Links”