parking_solution/apps/server/src/routes/ws.ts

import { randomBytes } from "node:crypto";
import type { FastifyInstance } from "fastify";
import type { Db } from "@parking/db";
import type { LedgerEvent } from "@parking/shared";
import { requireAuth, roleHasPermissions } from "../auth.js";
import {
  deviceEvents,
  type LaneStatusEvent,
  type LanePresenceEvent,
  type PlateRecognizedEvent,
} from "../device-events.js";
import { enrichEvent } from "../event-enrich.js";
import type { DeviceMonitor } from "../device-monitor.js";
import type { LaneStatus } from "../lane-status.js";
import type { LanePresence } from "../lane-presence.js";
import { getOccupancy } from "../occupancy.js";

// Live booth feed over a WebSocket. The booth UI opens ONE socket and receives
// server-pushed updates instead of polling: each signed ledger append (entry,
// exit, payment, void) is fanned out, and the recomputed occupancy rides along
// so the screen's count stays exact (occupancy is a fold over the same ledger,
// never a counter). Printer-status changes are forwarded too.
//
// Auth: the handshake is a normal GET through Fastify's lifecycle, so the same
// HttpOnly JWT cookie that guards the REST API guards this. We verify the JWT and
// role here. A browser's WebSocket constructor cannot set custom headers, so the
// CSRF double-submit header the REST mutations use is unavailable — which would
// leave the socket open to Cross-Site WebSocket Hijacking: a malicious page in the
// operator's browser could open ws://<booth>/api/ws, the browser would auto-attach
// the HttpOnly cookie, and the attacker would receive the live entry/exit/payment
// stream. The cookie alone is NOT a control here. So we replace the CSRF check with
// an Origin allowlist: the handshake's Origin must be same-origin (or an explicitly
// allowed booth UI origin). Non-browser clients (no Origin) are rejected too.
// See auth.ts, event-log.ts (emitLedger), capacity-occupancy.md.
//
// Desktop shell (Tauri) exception — the WS TICKET. The desktop app's HTTP goes
// through tauri-plugin-http (reqwest, its own cookie jar) and its WebSocket
// through tauri-plugin-websocket (bare tungstenite, NO cookie jar at all), so
// the JWT cookie set at login can never ride on the WS handshake — jwtVerify()
// would 401 every connect (found 2026-09-04: the desktop live feed reconnected
// every 10s forever). The JWT is HttpOnly and must stay out of JS, so instead
// the desktop client POSTs /api/ws/ticket (normal cookie + CSRF auth) to get a
// single-use, 30-second random ticket bound to its user, and presents it in an
// `x-ws-ticket` header on the handshake. A browser page cannot set custom
// headers on a WebSocket, so this path is unreachable from a browser and adds
// no CSWSH surface; the Origin allowlist still applies to both paths.

/** Permission required to watch the live feed (a read-only stream of ledger +
 *  device status). Any role granted `report:read` may watch. */
const WATCH_PERMISSION = "report:read" as const;

/** Handshake header carrying a desktop WS ticket (see file header). */
const WS_TICKET_HEADER = "x-ws-ticket";
/** A ticket is only good for the connect that immediately follows its issue. */
const WS_TICKET_TTL_MS = 30_000;

interface WsTicket {
  sub: string;
  roleId: string;
  expiresAt: number;
}

/** Outstanding tickets. Tiny (one per desktop connect attempt), in-memory only —
 *  a server restart invalidates them, which is fine: the client just asks for
 *  another on its next reconnect. */
const tickets = new Map<string, WsTicket>();

function issueWsTicket(sub: string, roleId: string): string {
  const now = Date.now();
  for (const [key, t] of tickets) {
    if (t.expiresAt <= now) tickets.delete(key);
  }
  const ticket = randomBytes(32).toString("hex");
  tickets.set(ticket, { sub, roleId, expiresAt: now + WS_TICKET_TTL_MS });
  return ticket;
}

/** Single-use: the ticket is removed whether or not it turns out to be valid. */
function consumeWsTicket(ticket: string): WsTicket | null {
  const t = tickets.get(ticket);
  if (!t) return null;
  tickets.delete(ticket);
  return t.expiresAt > Date.now() ? t : null;
}

/**
 * Is the handshake's Origin trusted? Same-origin (Origin host === Host header) is
 * always allowed; additional origins can be allowlisted via WS_ALLOWED_ORIGINS
 * (comma-separated) for a booth UI served from a different origin. A missing or
 * mismatched Origin is rejected — that is the anti-CSWSH control.
 */
function isAllowedOrigin(origin: string | undefined, host: string | undefined): boolean {
  if (!origin) return false; // no Origin → not a same-origin browser request
  let originHost: string;
  try {
    originHost = new URL(origin).host;
  } catch {
    return false; // malformed Origin
  }
  if (host && originHost === host) return true; // same-origin (any scheme/port match via host)
  const allow = (process.env.WS_ALLOWED_ORIGINS ?? "")
    .split(",")
    .map((s) => s.trim())
    .filter(Boolean);
  return allow.includes(origin);
}

type OutMsg =
  | {
      kind: "hello";
      occupancy: ReturnType<typeof getOccupancy>;
      devices: unknown;
      lanes: LaneStatusEvent;
      radar: LanePresenceEvent;
    }
  | { kind: "ledger"; event: unknown; occupancy: ReturnType<typeof getOccupancy> }
  | { kind: "printer-status"; event: unknown }
  | { kind: "device-status"; event: unknown }
  | { kind: "lane-status"; lanes: LaneStatusEvent }
  | { kind: "lane-presence"; radar: LanePresenceEvent }
  | { kind: "plate-recognized"; plate: PlateRecognizedEvent };

export async function wsRoutes(
  app: FastifyInstance,
  db: Db,
  deviceMonitor: DeviceMonitor,
  laneStatus: LaneStatus,
  lanePresence: LanePresence,
): Promise<void> {
  // Desktop-only: mint a WS ticket for the signed-in session (see file header).
  // Ordinary cookie + CSRF auth — the desktop client CAN do that over HTTP (via
  // tauri-plugin-http), it just can't carry the cookie onto the WebSocket.
  app.post("/api/ws/ticket", { preHandler: requireAuth }, async (req) => ({
    ticket: issueWsTicket(req.user.sub, req.user.roleId),
    expiresInMs: WS_TICKET_TTL_MS,
  }));

  app.get(
    "/api/ws",
    {
      websocket: true,
      // Origin allowlist (anti-CSWSH, replaces CSRF — see file header) THEN
      // session (JWT cookie, or a desktop WS ticket) THEN role. Reject a
      // cross/absent origin before touching either credential, so a hijack
      // attempt never reaches an authenticated socket.
      preHandler: async (req) => {
        if (!isAllowedOrigin(req.headers.origin, req.headers.host)) {
          throw Object.assign(new Error("forbidden origin"), { statusCode: 403 });
        }
        const rawTicket = req.headers[WS_TICKET_HEADER];
        const ticket = Array.isArray(rawTicket) ? rawTicket[0] : rawTicket;
        let roleId: string;
        if (ticket !== undefined) {
          const t = consumeWsTicket(ticket);
          if (!t) {
            throw Object.assign(new Error("invalid or expired ws ticket"), { statusCode: 401 });
          }
          roleId = t.roleId;
        } else {
          await req.jwtVerify(); // reads the HttpOnly cookie (browser path)
          if (!req.user) {
            throw Object.assign(new Error("forbidden"), { statusCode: 403 });
          }
          roleId = req.user.roleId;
        }
        if (!roleHasPermissions(roleId, [WATCH_PERMISSION])) {
          throw Object.assign(new Error("forbidden"), { statusCode: 403 });
        }
      },
    },
    (socket) => {
      const send = (msg: OutMsg) => {
        // readyState 1 = OPEN; never throw out of an event-bus callback.
        if (socket.readyState === 1) {
          try {
            socket.send(JSON.stringify(msg));
          } catch {
            /* drop on a broken socket */
          }
        }
      };

      // Initial snapshot so the client renders immediately, before any event:
      // occupancy AND the current device-status set (for the footer).
      send({
        kind: "hello",
        occupancy: getOccupancy(db),
        devices: deviceMonitor.snapshot(),
        lanes: laneStatus.snapshot(),
        radar: lanePresence.snapshot(),
      });

      // Subscribe to the live buses. Each handler recomputes occupancy from the
      // ledger (cheap fold) so the pushed count is always authoritative.
      const offLedger = deviceEvents.onLedger((event) => {
        // Enrich with read-time display fields (subscriber name) before fan-out.
        const enriched = enrichEvent(db, event as unknown as LedgerEvent);
        send({ kind: "ledger", event: enriched, occupancy: getOccupancy(db) });
      });
      const offPrinter = deviceEvents.onPrinterStatus((event) => {
        send({ kind: "printer-status", event });
      });
      // Unified device status (all categories) for the booth footer — pushed on
      // change; the initial set rode the hello above.
      const offDevice = deviceEvents.onDeviceStatus((event) => {
        send({ kind: "device-status", event });
      });
      // Lane busy/free (camera vehicle detection → booth barrier lights). Advisory.
      const offLane = deviceEvents.onLaneStatus((lanes) => {
        send({ kind: "lane-status", lanes });
      });
      // Lane RADAR presence (presence-input edge → barrier-light blink). Advisory.
      const offPresence = deviceEvents.onLanePresence((radar) => {
        send({ kind: "lane-presence", radar });
      });
      // A late async plate recognition → backfill the badge on the matching feed row. Advisory.
      const offPlate = deviceEvents.onPlateRecognized((plate) => {
        send({ kind: "plate-recognized", plate });
      });

      socket.on("close", () => {
        offLedger();
        offPrinter();
        offDevice();
        offLane();
        offPresence();
        offPlate();
      });
    },
  );
}