GHSA-8r6w-3qq5-4p4r

Pterodactyl's improper JWT scoping allows subuser to upload files when not explicitly granted `file.create` permissions

### Summary A privilege escalation vulnerability exists in the Wings /upload/file endpoint due to insufficient validation of panel-signed JWTs. Wings accepts any valid panel-signed JWT containing `server_uuid`, `user_uuid`, and `unique_id`, regardless of the token’s intended purpose. Because the Panel issues JWTs with these same claims for other lower-privilege operations (such as WebSocket authentication and file download links), an authenticated subuser can reuse one of those tokens to upload arbitrary files without possessing the required `file.create` permission. ### Impact Any subuser with permission to connect to a server's console, download files, or download backups could reuse those tokens to upload arbitrary files to the _same server_. A user that does not have access to a server as a subuser is not able to arbitrarily upload files. ### Details The panel generated JWT tokens for various purposes: - https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Services/Backups/DownloadLinkService.php#L33-L36 - https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Http/Controllers/Api/Client/Servers/FileUploadController.php#L45 - https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Http/Controllers/Api/Client/Servers/WebsocketController.php#L58-L61 - https://github.com/pterodactyl/panel/blob/0f82c105201b192d229f6abd5827e2ee7e672a05/app/Http/Controllers/Api/Client/Servers/FileController.php#L82-L85 Though as the actual purpose is not conveyed part of the JWT tokens, this introduces this vulnerability of being able to do non-intended actions due to the expected fields (i.e. `server_uuid`) on most endpoints being the same when parsing it on wings' side. ### PoC Create a new subuser that has the minimal amount of permissions on a server (`websocket.connect`). As that subuser, retrieve a websocket JWT token from the `GET /api/client/servers/[...]/websocket` endpoint (in my case, I manually just make a request under that user's browser session; you can probably just resend the /websocket request in browser console to get a fresh unused token). Using that websocket token, we can abuse this by directly using it in the `/upload/file` endpoint of the wings node instead of using it for websocket authentication: ```python3 import requests wings_url = 'http://[...]:8080' websocket_token = '[...]' res = requests.post(f'{wings_url}/upload/file', params = { 'token': websocket_token, }, files = { 'files': ('file-upload.txt', b'Hello, World!'), }) print(res.status_code, res.content) ``` Observe, that even though our subuser never has permissions outside viewing the console, they are able to write arbitrary files in the server. This pattern happens in a lot of other action, but this is probably the most interesting one.