[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                               |  assigned
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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Comment (by teor):

 Thanks for taking this over, dgoulet.

 Replying to [comment:2 nickm]:
 > NM.1. I'm not sure how I feel about this line:
 > {{{
 > +  tor_assert(seconds >= TIME_MIN);
 > }}}
 >
 > Are we sure that nobody can ever give tor_timgm() a big negative
 tm_year, causing it to crash Tor?

 We clip the year to a minimum of 1970 / 0, and the other fields are
 clipped to 0 or 1, so we can only get positive values.

 But I'm happy to include this check in the out of bounds condition rather
 than asserting on it.

 > NM.2. I think it would make more sense to make sure that `*time_out` is
 always set to _something_, in case some foolish programmer ignores the
 return value?

 I agree. 0 is as good as any other value.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18479#comment:5>
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