feat(sense): add loopback NVR management console

Sense/internal/console/handler.go

@@ -0,0 +1,100 @@
+// Package console serves the loopback-only Sense engineering console.
+package console
+
+import (
+	"embed"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net"
+	"net/http"
+	"net/url"
+	"strings"
+)
+
+//go:embed assets/index.html assets/app.css assets/app.js
+var assets embed.FS
+
+type handler struct {
+	previewBaseURL string
+	previewOrigin  string
+}
+
+// NewHandler builds the self-contained console handler. Config validation also
+// enforces this boundary; validating here keeps the package safe in isolation.
+func NewHandler(previewBaseURL string) (http.Handler, error) {
+	parsed, err := url.Parse(previewBaseURL)
+	if err != nil || parsed.Host == "" ||
+		(parsed.Scheme != "http" && parsed.Scheme != "https") ||
+		parsed.User != nil || parsed.RawQuery != "" || parsed.Fragment != "" ||
+		(parsed.Path != "" && parsed.Path != "/") {
+		return nil, errors.New("invalid Sense console WebRTC base URL")
+	}
+	host := parsed.Hostname()
+	ip := net.ParseIP(host)
+	if host != "localhost" && (ip == nil || !ip.IsLoopback()) {
+		return nil, errors.New("Sense console WebRTC base URL is not loopback")
+	}
+	base := strings.TrimRight(parsed.String(), "/")
+	return &handler{
+		previewBaseURL: base,
+		previewOrigin:  parsed.Scheme + "://" + parsed.Host,
+	}, nil
+}
+
+func (h *handler) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
+	h.securityHeaders(writer)
+	if request.Method != http.MethodGet && request.Method != http.MethodHead {
+		writer.Header().Set("Allow", "GET, HEAD")
+		http.Error(writer, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	switch request.URL.Path {
+	case "/sense-console/":
+		h.serveAsset(writer, request, "assets/index.html", "text/html; charset=utf-8")
+	case "/sense-console/app.css":
+		h.serveAsset(writer, request, "assets/app.css", "text/css; charset=utf-8")
+	case "/sense-console/app.js":
+		h.serveAsset(writer, request, "assets/app.js", "text/javascript; charset=utf-8")
+	case "/sense-console/config":
+		writer.Header().Set("Content-Type", "application/json")
+		if request.Method == http.MethodHead {
+			writer.WriteHeader(http.StatusOK)
+			return
+		}
+		_ = json.NewEncoder(writer).Encode(map[string]any{
+			"webrtc_base_url":        h.previewBaseURL,
+			"page_size":              16,
+			"max_active_previews":    4,
+			"recording_and_playback": false,
+		})
+	default:
+		http.NotFound(writer, request)
+	}
+}
+
+func (h *handler) securityHeaders(writer http.ResponseWriter) {
+	writer.Header().Set("Cache-Control", "no-store")
+	writer.Header().Set("Content-Security-Policy", fmt.Sprintf(
+		"default-src 'none'; script-src 'self'; style-src 'self'; connect-src 'self'; frame-src %s; img-src 'self' data:; font-src 'none'; base-uri 'none'; form-action 'self'; frame-ancestors 'none'",
+		h.previewOrigin,
+	))
+	writer.Header().Set("Permissions-Policy", "camera=(), microphone=(), geolocation=(), payment=(), usb=()")
+	writer.Header().Set("Referrer-Policy", "no-referrer")
+	writer.Header().Set("X-Content-Type-Options", "nosniff")
+	writer.Header().Set("X-Frame-Options", "DENY")
+}
+
+func (h *handler) serveAsset(writer http.ResponseWriter, request *http.Request, path, contentType string) {
+	contents, err := assets.ReadFile(path)
+	if err != nil {
+		http.Error(writer, "asset unavailable", http.StatusInternalServerError)
+		return
+	}
+	writer.Header().Set("Content-Type", contentType)
+	writer.Header().Set("Content-Length", fmt.Sprintf("%d", len(contents)))
+	writer.WriteHeader(http.StatusOK)
+	if request.Method == http.MethodGet {
+		_, _ = writer.Write(contents)
+	}
+}