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https://issues.apache.org/jira/browse/GUACAMOLE-2290?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18091589#comment-18091589
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Per von Zweigbergk commented on GUACAMOLE-2290:
-----------------------------------------------
I went ahead and made a PR for this since I needed to implement this in my own
local environment anyway.
> White screen with no error message when localStorage GUAC_AUTH_TOKEN is
> "undefined"
> -----------------------------------------------------------------------------------
>
> Key: GUACAMOLE-2290
> URL: https://issues.apache.org/jira/browse/GUACAMOLE-2290
> Project: Guacamole
> Issue Type: Bug
> Components: guacamole-client
> Reporter: Per von Zweigbergk
> Priority: Major
>
> I have run into an issue where Guacamole fails to load and presents the user
> with a white screen, instead of the expected login page. Refreshing doesn't
> resolve the issue.
> After some investigation, I found an error message like this in the
> Javascript console:
> jquery.min.js:2
> Uncaught SyntaxError: "undefined" is not valid JSON
> at JSON.parse (<anonymous>)
> at a.getItem (localStorageService.js:125:25)
> at h.getCurrentToken (authenticationService.js:466:36)
> at h.request (authenticationService.js:536:34)
> at Object.getLanguages (languageService.js:45:38)
> at v (translationLoader.js:74:25)
> at translationLoader.js:149:9
> at Object.invoke (angular.min.js:45:264)
> The relevant code appears to be here:
> [https://github.com/apache/guacamole-client/blame/27922fe19823942e7bc3a6b70560cebabec44e64/guacamole/src/main/frontend/src/app/storage/services/localStorageService.js#L125]
> Investigating the local storage, the {{GUAC_AUTH_TOKEN}} value seems to be
> set to the string "undefined" whenever this problem occurs.
> I've not been able to figure out *why* the GUAC_AUTH_TOKEN value is set to
> "undefined". It could be an interaction with the Barracuda WAF we have in
> front. But either way, it appears there is a specific bug in this part of the
> code. There is no proper handling of the exception thrown by the
> JSON.parse(data) call, if data is invalid JSON (in this case, the string
> "undefined").
> Either way, the fact that guacamole-client itself chokes in case the
> GUAC_AUTH_TOKEN value ends up being corrupted is a bug in its own right, and
> could be easy enough to fix by just handling the SyntaxError exception being
> thrown by JSON.parse and treating it as an empty value in this case.
> As a workaround, I've been telling my users to run the following command in
> the Javascript console to clear out this state:
> {{localStorage.removeItem('GUAC_AUTH_TOKEN');}} and this seems to
> temporarilly fix the issue, which leads me to believe that adding some guards
> around JSON parsing and treating an unparsable value as missing would
> properly mask your problem.
> I'm up submitting a PR for this if this approach to the fix is accepted.
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