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Wireshark-users: [Wireshark-users] websocket unmask decrypted data

From: Rob Dyck <rob.dyck@xxxxxxxxx>
Date: Fri, 05 Mar 2021 09:23:45 -0800
Running Wireshark 3.4.3

I have been looking at WSS traffic. WSS uses TLS for encryption. I can decrypt 
by collecting the pre-master secret data as described in various howtos.

A peculiarity of websocket is that he client to server data is XOR'd with a 
mask prior to encrypting. To view the data it must first be decrypted and then 
unmasked. In my initial session I was pleased to see three tabs at the bottom 
of the window. ( raw, decrypted and unmasked ).

Now the problem is that in subsequent sessions the unmask tab no longer 
appears. I don't know what I did differently initially to get the tab. I cannot 
find a configuration option that would enable this behaviour.

Decryption is useless without unmasking. Wireshark does not list WS or WSS in 
the list of protocols. However unmasking exists somewhere. I saw it initially.