feat(gdpr): HttpOnly author-token cookie (PR3 of #6701)

doc/cookies.md

@@ -7,7 +7,7 @@ Cookies used by Etherpad.
 | express_sid       | s%3A7yCNjRmTW8ylGQ53I2IhOwYF9... | example.org | /    | Session         | true      | true   | Session ID of the [Express web framework](https://expressjs.com). When Etherpad is behind a reverse proxy, and an administrator wants to use session stickiness, he may use this cookie. If you are behind a reverse proxy, please remember to set `trustProxy: true` in `settings.json`. Set in [webaccess.js#L131](https://github.com/ether/etherpad-lite/blob/01497aa399690e44393e91c19917d11d025df71b/src/node/hooks/express/webaccess.js#L131).                                                                                                                                                                                                                                                                                                                                       |
 | language          | en                               | example.org | /    | Session         | false     | true   | The language of the UI (e.g.: `en-GB`, `it`). Set in [pad_editor.js#L111](https://github.com/ether/etherpad-lite/blob/01497aa399690e44393e91c19917d11d025df71b/src/static/js/pad_editor.js#L111).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
 | prefs / prefsHttp | %7B%22epThemesExtTheme%22...     | example.org | /p   | year 3000       | false     | true   | Client-side preferences (e.g.: font family, chat always visible, show authorship colors, ...). Set in [pad_cookie.js#L49](https://github.com/ether/etherpad-lite/blob/01497aa399690e44393e91c19917d11d025df71b/src/static/js/pad_cookie.js#L49). `prefs` is used if Etherpad is accessed over HTTPS, `prefsHttp` if accessed over HTTP. For more info see https://github.com/ether/etherpad-lite/issues/3179.                                                                                                                                                                                                                                                                                                                                                                              |
-| token             | t.tFzkihhhBf4xKEpCK3PU           | example.org | /    | 60 days         | false     | true   | A random token representing the author, of the form `t.randomstring_of_lenght_20`. The random string is generated by the client, at ([pad.js#L55-L66](https://github.com/ether/etherpad-lite/blob/01497aa399690e44393e91c19917d11d025df71b/src/static/js/pad.js#L55-L66)). This cookie is always set by the client (at [pad.js#L153-L158](https://github.com/ether/etherpad-lite/blob/01497aa399690e44393e91c19917d11d025df71b/src/static/js/pad.js#L153-L158)) without any solicitation from the server. It is used for all the pads accessed via the web UI (not used for the HTTP API). On the server side, its value is accessed at [SecurityManager.js#L33](https://github.com/ether/etherpad-lite/blob/01497aa399690e44393e91c19917d11d025df71b/src/node/db/SecurityManager.js#L33). |
+| token             | t.tFzkihhhBf4xKEpCK3PU           | example.org | /    | 60 days         | true      | true   | A random token representing the author, of the form `t.randomstring_of_length_20`. Set by the server as an `HttpOnly; SameSite=Lax` cookie on the first GET to `/p/:pad` (see `src/node/utils/ensureAuthorTokenCookie.ts`). The server reads the cookie from the socket.io handshake in `PadMessageHandler.handleClientReady` to resolve the author. Not readable from browser JavaScript. See [privacy.md](privacy.md). |
 
 For more info, visit the related discussion at https://github.com/ether/etherpad-lite/issues/3563.