[tor-bugs] #19127 [Core Tor/Tor]: Don't crash authorities with more than 254 shared random reveals

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#19127: Don't crash authorities with more than 254 shared random reveals
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     Reporter:  teor      |      Owner:
         Type:  defect    |     Status:  new
     Priority:  Medium    |  Milestone:  Tor: 0.2.9.x-final
    Component:  Core      |    Version:
  Tor/Tor                 |   Keywords:  tor-hs, 029-proposed, assert-crash
     Severity:  Normal    |  Parent ID:  #16943
Actual Points:  0.5       |   Reviewer:
       Points:  0.5       |
      Sponsor:            |
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 Rather than asserting that a tor network never has more than 253
 authorities, we could instead log when we truncate the number of reveals
 in the shared random hash.

 As a consequential change, we should do this truncation as late as
 possible, so that the value assigned to `srv->num_reveals` is not
 truncated.

 In any case, `tor_assert(reveal_num < UINT8_MAX);` is unnecessarily
 strict, it can be `tor_assert(reveal_num <= UINT8_MAX);`.

 Please see my branch sr-no-crash on https://github.com/teor2345/tor.git
 for fixes to these issues.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19127>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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