server: anonymous LIST of users returns 403, not 200 with an empty array

Found while re-verifying the security posture against the public hostname now
that the server is internet-exposed. pb_hooks/main.pb.js covered bookcases,
shelves and books but never users, so an anonymous GET of the accounts
collection answered 200 with an empty array.

Nothing leaked: two real accounts exist and the declarative listRule filtered
both out, so no account, email or id was ever visible to an anonymous caller.
But "200 with []" is the exact wrong signal this hook exists to remove — some
clients read it as an allowed request — and the accounts collection is the last
place to leave it. Defensible while the server was localhost-only; not now.

Re-verified over the internet after restarting the service: books, shelves,
bookcases and users all 403 anonymous, self-registration 403, health 200.

Also re-verified that login still works, since this hook now runs on a
collection the app authenticates against: auth-with-password returns 200 with a
token, and an authenticated LIST of all four collections still returns 200. The
hook rejects unauthenticated list/search only, and auth-with-password is not a
list request.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPpdG8VnRfS3KkisR3HUAE

server/README.md

@@ -90,12 +90,18 @@ A `200` with a non-empty `items` array from any of those is a breach, and a
 `200` with an empty one means the `pb_hooks` guard is not loaded — see the
 quirk described above.
 
-> **Known gap:** `GET /api/collections/users/records` currently answers
-> **200 with an empty array** rather than 403. Nothing is disclosed — the
-> `listRule` filters every row out, so an anonymous caller sees no accounts,
-> no emails, no ids — but it is the same wrong-signal quirk as above, and
-> `pb_hooks/main.pb.js` does not yet cover the `users` collection. Adding it
-> to that hook's collection list closes it.
+Check the accounts collection too — it is covered by the same hook:
+
+```sh
+curl -s -o /dev/null -w '%{http_code}\n' "$BASE/api/collections/users/records"
+# -> 403
+
+# ...but logging in must still work, which is the thing to re-check after any
+# change to pb_hooks (the hook rejects anonymous LIST, not authentication):
+curl -s -o /dev/null -w '%{http_code}\n' -X POST "$BASE/api/collections/users/auth-with-password" \
+  -H 'Content-Type: application/json' -d '{"identity":"you@example.com","password":"..."}'
+# -> 200
+```
 
 ## Where the live server runs
 

server/pb_hooks/main.pb.js

@@ -10,12 +10,24 @@
 // ever get a 200 back from these endpoints, even an empty one, since some
 // HTTP/JS clients treat "200 with []" as a successful, allowed request.
 // This hook makes that explicit: anonymous list/search requests against the
-// three app collections are rejected with 403, matching create/update/
+// app collections are rejected with 403, matching create/update/
 // view/delete (which already 400/404 for unauthenticated callers via the
 // declarative rules alone).
+//
+// "users" is in this list as of 2026-09-12. It was omitted originally, when
+// the server was only reachable on localhost; the server is now exposed to
+// the internet, so an anonymous GET of /api/collections/users/records was
+// answering 200 with an empty array. Nothing leaked — the declarative
+// listRule filters every row out, so no account, email or id was ever
+// visible — but it is the same wrong signal this hook exists to remove, and
+// the accounts collection is the last place to leave it.
+//
+// This blocks only UNAUTHENTICATED list/search. Logging in is unaffected:
+// auth-with-password is not a list request, and it is the only users
+// endpoint the app calls at all.
 onRecordsListRequest((e) => {
   if (!e.auth) {
     throw new ForbiddenError("Authentication required.");
   }
   e.next();
-}, "bookcases", "shelves", "books");
+}, "bookcases", "shelves", "books", "users");