Darren Foley created GUACAMOLE-1849:
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Summary: Parser reparses same instructions multiple times in some
cases
Key: GUACAMOLE-1849
URL: https://issues.apache.org/jira/browse/GUACAMOLE-1849
Project: Guacamole
Issue Type: Bug
Components: guacamole-common-js
Affects Versions: 1.5.2, 1.5.3
Reporter: Darren Foley
When using a tunnel that relies on XHR rather than websockets, parseResponse in
Tunnel.js calls parse.receive(current, true) when xmlhttprequest.readyState is
3 or 4. When the readyState is 3, setInterval is used to periodically call
parseResponse to check the state, until reaching readyState 4. This means that
the parser.receive call can be made multiple times for one request. This is
supposed to be fine, since we're setting isBuffer to true, which means we
should send in the same message, with anything new simply tacked onto the end.
The startIndex and elementEnd variables in receive should simply keep track of
where we last left off, and only parse any new instructions. However, this is
not what's happening. Instead, they are getting reset each time and the entire
message is parsed again, re-executing the same instructions. This was really
clear in our customized version of guacamole, as we've added our own
instruction which adds an icon to the top right corner when something is
enabled. Due to this issue, the icon was duplicated many times. I've made a
hotfix in our copy of the js which fixes this when isBuffer is true and retains
the existing behaviour when it's false. I can provide this in a pull request,
though I'm not sure if you'll want to use this change or rework the whole
function.
Note: I believe this bug came in with d6a01c28e56edb0b0d3bab4459b1f1a75414e999
so it would affect 1.5.2, too, though I've only tested with 1.5.3.
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