[tor-bugs] #18479 [Tor]: Avoid overflow in tor_timegm when time_t is 32 bit

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#18479: Avoid overflow in tor_timegm when time_t is 32 bit
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 Reporter:  teor                                 |          Owner:  asn
     Type:  defect                               |         Status:
 Priority:  Medium                               |  needs_review
Component:  Tor                                  |      Milestone:  Tor:
 Severity:  Normal                               |  0.2.8.x-final
 Keywords:  integer-overflow security-maybe      |        Version:  Tor:
  must-fix-before-028-rc                         |  unspecified
Parent ID:                                       |     Resolution:
 Reviewer:                                       |  Actual Points:
                                                 |         Points:
                                                 |        Sponsor:
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Changes (by asn):

 * status:  assigned => needs_review


Comment:

 Patch looks good. I addressed both comments by Nick in my branch
 `timegm_overflow`.

 I also changed the assert to a simple check. I agree that `seconds` should
 only take positive values, however I opted for explicitly checking for it,
 in case there is any other unexpected overflows in the calculations above.

 Unfortunately, I don't have a 32-bit box to actually test the overflow.
 Tests pass fine in my 64-bit box.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18479#comment:6>
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