Pin camera sources by parsed URL

Camera catalog image URLs were pinned by string prefix, so a URL that only
began with the agency's directory before dot segments or an encoded separator
were resolved still counted as inside it. The pin now parses the URL and
requires the same scheme, the exact host, no credentials, the default port and
a normalized path inside the pinned directory. Redirects on a pinned host must
stay inside the same directory.

Document the response format checks and API response headers alongside the
existing server hardening notes.

server/providers/cctv/media.js

@@ -1,13 +1,21 @@
 import { Readable } from 'node:stream';
-import { hashSeed, escapeXml } from './normalize.js';
+import { hashSeed, escapeXml, pinnedCameraUrl } from './normalize.js';
 import {
+  CALGARY_IMAGE_ORIGIN,
   CCTV_FRAME_FETCH_TIMEOUT_MS,
   CCTV_FRAME_MAX_BODY_BYTES,
   CCTV_MEDIA_FETCH_TIMEOUT_MS,
   CCTV_MEDIA_IDLE_TIMEOUT_MS,
   CCTV_MEDIA_MAX_BODY_BYTES,
+  HK_IMAGE_ORIGIN,
+  KING_COUNTY_IMAGE_ORIGIN,
   NSW_IMAGE_ORIGIN,
   NSW_IMAGE_USER_AGENT,
+  TALLINN_IMAGE_ORIGIN,
+  TARKTEE_IMAGE_ORIGIN,
+  TFL_IMAGE_ORIGIN,
+  WARENDORF_IMAGE_ORIGINS,
+  WSDOT_IMAGE_ORIGIN,
 } from './constants.js';
 /**
  * Generate a synthetic SVG billboard image for a CCTV camera placeholder.
@@ -504,9 +512,40 @@ export async function fetchTxdotSnapshot(
 /** Redirect hops the frame path will follow, and only within the same host. */
 const MAX_SAME_HOST_REDIRECTS = 2;
 
+/**
+ * Directories camera catalogs are pinned to, by host. A redirect on one of
+ * these hosts must stay inside the pinned directory too, so a same-origin
+ * redirect cannot leave it (another bucket on a shared storage host).
+ */
+const CCTV_PINNED_PREFIXES_BY_HOST = new Map();
+for (const prefix of [
+  TFL_IMAGE_ORIGIN,
+  TALLINN_IMAGE_ORIGIN,
+  TARKTEE_IMAGE_ORIGIN,
+  ...WARENDORF_IMAGE_ORIGINS,
+  NSW_IMAGE_ORIGIN,
+  CALGARY_IMAGE_ORIGIN,
+  HK_IMAGE_ORIGIN,
+  KING_COUNTY_IMAGE_ORIGIN,
+  WSDOT_IMAGE_ORIGIN,
+]) {
+  const host = new URL(prefix).hostname;
+  CCTV_PINNED_PREFIXES_BY_HOST.set(host, [
+    ...(CCTV_PINNED_PREFIXES_BY_HOST.get(host) || []),
+    prefix,
+  ]);
+}
+
+/** Whether a redirect target stays inside its host's pinned directory. */
+function withinPinnedPrefix(url) {
+  const prefixes = CCTV_PINNED_PREFIXES_BY_HOST.get(url.hostname);
+  return !prefixes || prefixes.some((p) => pinnedCameraUrl(url.href, p));
+}
+
 /**
  * Fetch a registered frame URL following redirects ONLY within the original
- * origin (scheme, host and port; at most MAX_SAME_HOST_REDIRECTS hops).
+ * origin (scheme, host and port; at most MAX_SAME_HOST_REDIRECTS hops) and,
+ * on a pinned camera host, within its pinned directory.
  * Default redirect-following would let an upstream steer a host-pinned
  * request, and its host-specific headers, to any origin, another port, or a
  * plaintext downgrade.
@@ -547,7 +586,7 @@ export async function fetchWithinHost(url, init, fetchImpl = fetch) {
     } catch {
       return null;
     }
-    if (next.origin !== origin) return null;
+    if (next.origin !== origin || !withinPinnedPrefix(next)) return null;
     current = next;
   }
   return null;