[Bug 21203] EME leaks information cross-origin

https://www.w3.org/Bugs/Public/show_bug.cgi?id=21203

--- Comment #30 from Adrian Bateman [MSFT] <adrianba@microsoft.com> ---
(In reply to David Dorwin from comment #29)
> Should we really report an error when the first key reference is encountered
> or should we wait until an encrypted block is encountered (even though we
> cannot report a needkey event). It's possible playback could proceed without
> error (i.e. using only unencrypted streams within the media data. Also,
> having one place to report errors is simpler for impelementors.

Having looked at this, I have a different proposal:

1) We should change step 3 of the algorithm in 4.1 (First time a key reference
is encountered) and instead of throwing an error, we should send the needkey
event with empty initdata. This allows apps that can get the initdata from a
different source to know the key reference has been reached.

2) We should remove the error from step 1 of 4.2 (encrypted block encountered)
if keys is null. This means that applications that see encrypted content but
haven't handled needkey or otherwise tried to provide keys will stall playback
instead of throwing an error. I think this is acceptable.

If we do this then we can remove MEDIA_ERR_ENCRYPTED from the spec.

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Received on Friday, 15 November 2013 03:37:48 UTC