[tor-bugs] #32439 [Circumvention/Obfs4]: tor can't bootstrap with obfs4 bridge and skewed clock

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#32439: tor can't bootstrap with obfs4 bridge and skewed clock
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 Reporter:  intrigeri                            |          Owner:  (none)
     Type:  defect                               |         Status:  new
 Priority:  Medium                               |      Milestone:
Component:  Circumvention/Obfs4                  |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  bootstrap, clock-skew, AffectsTails  |  Actual Points:
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by yawning):

 This is not a defect, this is how the protocol is specified.

 Servers should not respond to replayed handshakes.  In order to limit the
 amount of history that each server needs to keep, the number of hours
 since the UNIX epoch is included as part of the handshake authentication
 digest.

 As a concession to reality, per the specification, each server will
 tolerate a skew of up to +/- 1 hour.  While it is not overly difficult to
 increase the amount of skew tolerated, this will result in increased
 resource consumption on the server side, and more expensive handshakes.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32439#comment:2>
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