[tor-bugs] #20027 [Core Tor/Tor]: Ed25519 certificate parsing does badly with expirations after 2038

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#20027: Ed25519 certificate parsing does badly with expirations after 2038
------------------------------+--------------------------------
     Reporter:  nickm         |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.2.9.x-final
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:  TorCoreTeam201608
Actual Points:                |  Parent ID:  #15055
       Points:  0             |   Reviewer:
      Sponsor:                |
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 We deliberately chose an hour-based expiration counter for ed certs,
 because of 32-bit issues.  But when we parse them, we just multiply the
 32-bit field by 3600.  That results in an overflow if the time is greater
 than UINT32_MAX.

 The impact here isn't too bad.  First, it only affects certs that expire
 after 32-bit signed time overflows in Y2038.  Second, it can only make it
 seem that a non-expired cert is expired: it can never make it seem that an
 expired cert is still live.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20027>
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