[tor-bugs] #16300 [Tor Browser]: Make sure the BroadcastChannel API adheres to our URL bar domain isolation

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#16300: Make sure the BroadcastChannel API adheres to our URL bar domain isolation
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     Reporter:  gk       |      Owner:  mcs
         Type:  task     |     Status:  needs_revision
     Priority:  major    |  Milestone:
    Component:  Tor      |    Version:
  Browser                |   Keywords:  ff38-esr, tbb-linkability, tbb-5
   Resolution:           |  .0a-highrisk, TorBrowserTeam201506R,
Actual Points:           |  GeorgKoppen201506R
       Points:           |  Parent ID:
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Changes (by mikeperry):

 * status:  needs_review => needs_revision


Comment:

 It seems like GetFirstPartyHost() can fail to get an isolation host in
 InitializeRunnable::MainThreadRun() in
 dom/broadcastchannel/BroadcastChannel.cpp if there is no document yet in
 the Worker. Doesn't this mean that workers who can trigger this case can
 still broadcast to eachother even if they are launched from different
 isolation domains, because their empty isolation host strings will match?

 I'm not completely clear on what is the best way to handle this case.
 Perhaps broadcast messages should fail if isolation is enabled and the
 isolation host is either empty (and also if prefixed with "--
 NoFirstPartyHost-", for when the getFirstPartyHostForIsolation API itself
 fails)?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16300#comment:11>
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