Более подробное перечитывание документации дало свои результаты. Создатели SockJS заблокировали авторизацию через кукиз. Мотивировали это возникновением проблем безопасности если используется эмуляция через iframe.
AuthorisationSockJS-node does not expose cookies to the application. This is done deliberately as using cookie-based authorisation with SockJS simply doesn't make sense and will lead to security issues.
Cookies are a contract between a browser and an http server, and are identified by a domain name.
If a browser has a cookie set for particular domain, it will pass it as a part of all http requests to the host. But to get various transports working, SockJS uses a middleman
an iframe hosted from target SockJS domain. That means the server will receive requests from the iframe, and not from the real domain. The domain of an iframe is the same as the SockJS domain. The problem is that any website can embed the iframe and communicate with it - and request establishing SockJS connection. Using cookies for authorisation in this scenario will result in granting full access to SockJS communication with your website from any website. This is a classic CSRF attack.
Basically - cookies are not suited for SockJS model.
If you want to authorise a session - provide a unique token on a page, send it as a first thing over SockJS connection and validate it on the server side. In essence, this is how cookies work.
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