[tor-bugs] #16458 [Tor]: torspec references UTC, but tor uses unix time (leap second handling)

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#16458: torspec references UTC, but tor uses unix time (leap second handling)
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 Reporter:  teor                    |          Owner:
     Type:  task                    |         Status:  new
 Priority:  normal                  |      Milestone:
Component:  Tor                     |        Version:
 Keywords:  tor-spec documentation  |  Actual Points:
Parent ID:                          |         Points:
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 When the various torspec documents specify time, they refer to UTC. But
 the implementations used by at least Linux, *BSD and OS X are based on the
 Unix time epoch.

 This makes a difference to how leap seconds are handled: UTC includes leap
 seconds, but unix time excludes them.

 We should:
 * ensure that none of the security properties of tor depend on leap
 seconds either being present or absent, either individually or in
 aggregate:
  * every minute is not 60 seconds long (and equivalently for hour, day,
 week)
  * some epoch times can repeat or be missing
  * UTC and Unix time differ by approximately 30 seconds
 * check how the current Linux, BSD, Windows and OS X implementations
 handle leap seconds (in roughly that order of priority)
 * consider and document tor's handling of leap seconds

 See:
 * https://en.wikipedia.org/wiki/Leap_second
 * https://en.wikipedia.org/wiki/Unix_time

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/16458>
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