FileGator: Missing authorization in GET /batchdownload allows cross-user retrieval of another user's archive

Summary

GET /batchdownload streams a batch ZIP to any requester who supplies its uniqid, without checking that the current user/session created it. In deployments where users have separate home directories, a valid low-privileged user who obtains an active archive id can download another user's batch archive, disclosing files the per-user boundary otherwise protects. Reported with explicit preconditions and bounded impact — not a universal "any user steals any file" issue.

Details

The archive id is generated with plain uniqid() and no ownership metadata is bound to it before streaming.

• backend/Services/Archiver/Adapters/ZipArchiver.php:44 — createArchive() uses plain uniqid().
• backend/Controllers/DownloadController.php:144-145 — batchDownloadStart() reads the tmpfs file by the request-supplied uniqid after only a charset preg_replace().
• backend/Controllers/DownloadController.php:158 — the tmpfs archive is removed only after streaming.
• backend/Controllers/routes.php:207-226 — both batch endpoints are exposed to normal roles with read, download, batchdownload.

No user id, session id, home directory, or creator check is applied before streaming. The code path is unchanged since commit 3f03a40 (2022-05-31) and is present in the latest release v7.14.3.

PoC

Preconditions: a multi-user deployment with distinct per-user homedirs (set per-user in users.json, or private_repos => true on the WordPress/LDAP adapter). The shipped sample config (admin/guest both at /, guest with no perms) does not create this boundary on its own. Attacker is a valid user with read, download, batchdownload.

1. User John (homedir /john) creates secret.txt, signs in, and creates a batch archive via POST /batchdownload. The JSON response returns the archive uniqid.
2. User Jane (homedir /jane, with batchdownload) signs in normally.
3. Jane's direct GET /download of /secret.txt returns 302 — the normal home-directory boundary blocks the file.
4. Jane sends GET /batchdownload?uniqid=<John's id> and receives a valid ZIP containing secret.txt with John's content.

A PHPUnit proof with two real sessions reproduces this end to end (OK, 3 tests / 29 assertions), plus a lifecycle test (OK, 2 tests / 9 assertions). Full test files, run logs, and a real Apache access-log replay demo are available on request.

Lifetime / acquisition: a normal completed download removes the archive at the end of streaming, limiting the window. An aborted/failed download leaves the archive in tmpfs (cleanup never reached). The frontend issues the download as a top-level navigation (window.open('.../batchdownload&uniqid='+ret.uniqid, '_blank')), so the id appears in standard web access logs. That access-log path only adds meaningful impact when log visibility is decoupled from host filesystem access (e.g. a log-aggregation/shared-hosting/downstream-sink reader) and the archive is still alive; if the reader is ops/root on the same host they can already read the storage tree directly. The uniqid() token is timestamp-derived (1,000,000-value space per known second) — included to justify a CSPRNG, not presented as a practical universal brute force.

Impact

Missing authorization (CWE-862) on a temporary download object, leading to cross-user file disclosure across the per-user home-directory boundary in configured multi-user deployments. Secondary effect: a successful replay deletes the victim's pending archive (the GET removes the tmpfs file after streaming), denying the victim their own download if not yet consumed.

Remediation: generate ids with bin2hex(random_bytes(32)); store creator user/session + home dir + expiry per archive id; verify the requester matches before streaming and return 403/404 on mismatch or unknown/expired id; delete metadata with the tmpfs file.