This is required because the PDF Viewer itself is embedded using an iframe from the same domain. The default policy is blocking this.
Going on further, we have to come up with a solution in the future how to handle previews by applications, one example might be that they call their own endpoint and not the generic share page to allow applications to have full control over how to display previews.
Anyways, to test this behaviour use a decent newer browser (such as Chrome 41) and share a PDF file, obviously the PDF viewer needs to be enabled as well. Without this patch publicly shared PDF files should not get previewed and an error is thrown. (if it isn't then your browser is probably not obeying our Content-Security-Policy and you might consider switching to another one ;))
Issue report:
> Hum, well I upgraded the package then visited the web interface to
trigger the update and it failed; the UI would say there was a
possible CSRF attack and after that it'd be stuck in maintenance mode.
Tried a few times (by editing maintenance to false in owncloud.conf)
and same result each time.
That smells partially like an issue caused by our EventSource implementation, due to legacy concerns the CSRF verification happens within the EventSource handling and not when the actual endpoint is called, what happens here then is:
1. User has somehow an invalid CSRF token in session (or none at all)
2. User clicks the update button
3. Invalid CSRF token is sent to update.php - no CSRF check there => Instance gets set in maintenance mode
4. Invalid CSRF token is processed by the EventSource code => Code Execution is stopped and ownCloud is stuck in maintenance mode
I have a work-around for this problem, basically it verifies the CSRF token already in step 3 and cancels execution then. The same error will be shown to the user however he can work around it by refreshing the page – as stated by the error. I think that’s an acceptable behaviour for now: INSERT LINK
To verify this test:
1. Delete your ownCloud cookies
2. Increment the version in version.php
3. Try to upgrade
=> Before the patch: Instance shows an error, is set to upgrade mode and a refresh does not help
=> After the patch: Instance shows an error, a refresh helps though.
This is not really the best fix as a better solution would be to catch such situations when bootstrapping ownCloud, however, I don’t dare to touch base.php for this sake only, you never know what breaks then…
That said: There might be other bugs as well, especially the stacktrace is somewhat confusing but then again it installing ownCloud under /usr/share/owncloud/ and I bet that is part of the whole issue ;-)
