[tor-bugs] #19186 [Applications/Tor Browser]: KeyboardEvents are only rounding to 100ms

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#19186: KeyboardEvents are only rounding to 100ms
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 Reporter:  arthuredelstein                      |          Owner:
     Type:  defect                               |  arthuredelstein
 Priority:  Medium                               |         Status:
Component:  Applications/Tor Browser             |  needs_review
 Severity:  Normal                               |      Milestone:
 Keywords:  tbb-fingerprinting,                  |        Version:
  TorBrowserTeam201505R                          |     Resolution:
Parent ID:                                       |  Actual Points:
 Reviewer:                                       |         Points:
                                                 |        Sponsor:
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Changes (by arthuredelstein):

 * keywords:  tbb-fingerprinting, TorBrowserTeam201505 => tbb-
     fingerprinting, TorBrowserTeam201505R
 * status:  new => needs_review


Comment:

 If we want to make sure that KeyboardEvent::timeStamp rounding to 250 ms
 is exposed to content JS, we can make Event::timeStamp virtual (and fix
 the return type of KeyboardEvent::timeStamp). Here's an
 [https://github.com/arthuredelstein/tor-browser/commit/19186_virtual
 example fixup], probably not for use.

 But I'm not sure this is really useful, as it's still very easy to get
 100-ms precision on keystroke times. Just ignore `KeyboardEvent.timeStamp`
 and use `Date.now()` on the KeyboardEvent handler:

 {{{
 document.addEventListener("keydown", e => console.log(e.key + ": " +
 Date.now()));
 }}}

 So I'm proposing the following patch instead, which simply removes our
 original change to KeyboardEvent.h. Then we would rely on the 100-ms
 rounding inside Event.cpp, which is already applied to KeyboardEvents. (If
 it looks like 100-ms is unsufficient jitter for KeyboardEvents, then we
 may want to increase the rounding for all JS timing sources.)

 https://github.com/arthuredelstein/tor-browser/commit/19186
 Hash cb8eace4cd33cc9905bb7edbb8d9c066cc4217df

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19186#comment:1>
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