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Last Updated: 14 Feb 2020 07:39 by George
George
Created on: 13 Feb 2020 09:10
Type: Feature Request
0
Auto detect zlib compression inside WebSocket packet viewer.

It's a common practice to compress binary payloads inside WebSockets using zlib.deflate, though in Fiddler they are displayed as binary dump. It's quite simple to analyze two trailing bytes of a binary packet, and if they are equal to 0xFFFF you could try to apply zlib.inflate to that packet. If it succeeds, replace the binary contents with its unzipped text equivalent.

WMBR, George Hazan.

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2 comments
George
Posted on: 14 Feb 2020 07:39

Hi, thanks for the response.

In my case the problem is that the server rejects any attempt to connect if the "Sec-WebSocket-Extensions" header has no "permessage-deflate" option, so this trick doesn't work.

When I manually edit WebSocket headers (either via Headers editor or using Raw window), the changes disappear immediately when I press F2 in the second time, so it doesn't help either. Maybe I'm doing smth wrong?

WMBR, George Hazan.

Eric
Posted on: 14 Feb 2020 05:41

I think this is basically the same as https://feedback.telerik.com/fiddler/1361360-support-sec-websocket-extensions-permessage-deflate (there's a workaround in that thread).

The trick here that makes this slightly non-trivial is that it's possible to share the decompression context across multiple messages.

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