[Bug 1849644] Re: QEMU VNC websocket proxy requires non-standard 'binary' subprotocol

[Christian Ehrhardt ]

Repro steps:
$ sudo apt install qemu-system-x86 novnc
/usr/share/novnc
python3 -m http.server

Connect browser to http://<IP>:8000/vnc.html
  Click "Settings"
  Open "advanced"
  Open "websocket"
  Set port 5700
  Clear path
  Click "Connect"

And it works ...

Turns out my former check on the offending noVNC commit was wrong.
There are
https://github.com/novnc/noVNC/commit/f8318361b1b62c4d76b091132d4a8ccfdd2957e4 
(referenced on this bug before)
$ git tag --contains f8318361b1b62c4d76b091132d4a8ccfdd2957e4
v1.0.0
But only really gone later with:
https://github.com/novnc/noVNC/commit/c912230309806aacbae4295faf7ad6406da97617
$ git tag --contains c912230309806aacbae4295faf7ad6406da97617
v1.2.0

So the novnc of Focal isn't affected but anyone who uses a newer noVNC >=1.2 
would be.
=> lower SRU priority
=> Modify above repro steps to not use noVNC from Focal via apt but use 1.2 
from snaps


Repro steps:
$ snap install novnc
$ novnc --vnc localhost:5700
Connect browser to http://<IP>:6080/vnc.html
Click "Connect"

TODO: repro steps to be verified with a qemu that has the fix applied

** Changed in: qemu (Ubuntu Focal)
   Importance: Undecided => Low

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https://bugs.launchpad.net/bugs/1849644

Title:
  QEMU VNC websocket proxy requires non-standard 'binary' subprotocol

Status in QEMU:
  Fix Released
Status in qemu package in Ubuntu:
  Fix Released
Status in qemu source package in Focal:
  Confirmed

Bug description:
  When running a machine using "-vnc" and the "websocket" option QEMU
  seems to require the subprotocol called 'binary'. This subprotocol
  does not exist in the WebSocket specification. In fact it has never
  existed in the spec, in one of the very early drafts of WebSockets it
  was briefly mentioned but it never made it to a final version.

  When the WebSocket server requires a non-standard subprotocol any
  WebSocket client that works correctly won't be able to connect.

  One example of such a client is noVNC, it tells the server that it
  doesn't want to use any subprotocol. QEMU's WebSocket proxy doesn't
  let noVNC connect. If noVNC is modified to ask for 'binary' it will
  work, this is, however, incorrect behavior.

  Looking at the code in "io/channel-websock.c" it seems it's quite
  hard-coded to binary:

  Look at line 58 and 433 here:
  https://git.qemu.org/?p=qemu.git;a=blob;f=io/channel-websock.c

  This code has to be made more dynamic, and shouldn't require binary.

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