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Pointers for Websocket Security

Websocket security:

1. In case of form based authentication, the authentication must happen before WebSocket handshake. The sessiontoken must be used when doing the first handshake.

2.  The WebSocket server can use any client authentication
mechanism available to a generic HTTP server, such as any cookie field value, basic
authentication, digest authentication, or certificate authentication. As long there is a
possibility to authenticate the user in a secure manner and the WebSocket server
verifies it, the authentication mechanism in question is suitable for use.

3. After authentication comes the authorization part. Authorization is mostly application dependent and mostly controlled at the application logic leve. Same principle of least privilege are applied in this context too. Need to check if a unprivileged user is able to access/ see data/ function of other users. 
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4. Cross-origin headers must be checked, if they allow all the sites to communicate with server, any client can create handshake with the server. So Allow-Access-Origin header must contain a domain name rather than a wildcard (*).

5. Encryption must be turned on (wss://). It's not turned on by default for WebSockets.

6. All the usual relevant OWASP Top 10 issues.

7. Resource exhaustion- Denial Of Service attacks. Tries to consume server resources to slow it down considerably or make it down. By default WebSockets are connection-oriented protocol which means the connection does not close automatically until one of the parties close it down.

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