remote-local-storage/main.go

// Save and serve HTML local storage in server
// This application provides a wrapper to save and restore localStorage of webapps in a server.
// It's designed for browsers that clear localStorage when exiting (like Tor Browser) or to share localStorage across multiple browsers.
package main

import (
	"bytes"
	_ "embed"
	"flag"
	"io"
	"log"
	"net/http"
	"os"
	"strings"
	"time"

	"go.balki.me/anyhttp"
)

//go:embed wrap.html
var html []byte

// getDumpFileName generates a hostname-specific dump filename
func getDumpFileName(host string) string {
	// Extract hostname from Host header
	hostname := host
	if hostname == "" {
		hostname = "localhost"
	}
	// Sanitize hostname to prevent path traversal
	hostname = strings.ReplaceAll(hostname, "/", "_")
	hostname = strings.ReplaceAll(hostname, "..", "_")

	// Create dump file name with hostname
	return hostname + "-dump.json"
}

func main() {
	addr := flag.String("address", "localhost:3242", "Listen address. See go.balki.me/anyhttp for usage")

	flag.Parse()

	// Handle root path - show error message
	http.HandleFunc("/", func(w http.ResponseWriter, _ *http.Request) {
		if _, err := w.Write([]byte("<h2>Error!</h2><p>Check your webserver config, You should not see this!</p>")); err != nil {
			log.Panic(err)
		}
	})

	// Serve the wrap.html page at /wrap/ path
	http.HandleFunc("/wrap/", func(w http.ResponseWriter, r *http.Request) {
		http.ServeContent(w, r, "index.html", time.Now(), bytes.NewReader(html))
	})

	// Handle saving local storage data to server
	http.HandleFunc("/wrap/saveLS", func(w http.ResponseWriter, r *http.Request) {
		// Read the request body containing localStorage data
		data, err := io.ReadAll(r.Body)
		if err != nil {
			log.Panic(err)
		}

		// Generate dump filename
		dumpFile := getDumpFileName(r.Host)

		// Write the data to the dump file
		if err := os.WriteFile(dumpFile, data, 0o600); err != nil {
			log.Panic(err)
		}

		log.Println("Saved!")

		// Send OK response
		if _, err := w.Write([]byte("OK")); err != nil {
			log.Panic(err)
		}
	})

	// Handle loading local storage data from server
	http.HandleFunc("/wrap/loadLS", func(w http.ResponseWriter, r *http.Request) {
		// Set proper content type for JSON response
		w.Header().Set("Content-Type", "application/json")

		// Generate dump filename
		dumpFile := getDumpFileName(r.Host)

		// Read the dump file
		data, err := os.ReadFile(dumpFile)
		if err != nil { // First time - return empty JSON
			data = []byte("{}")
		}

		// Send the data back to client
		if _, err := w.Write(data); err != nil {
			log.Panic(err)
		}
		log.Println("Sent!")
	})

	// Start the HTTP server
	err := anyhttp.ListenAndServe(*addr, nil)
	if err != nil {
		log.Panic(err)
	}
}