[tor-bugs] #17682 [Tor]: safe_timer_diff is unsafe under wrapping

[Tor Bug Tracker & Wiki]

#17682: safe_timer_diff is unsafe under wrapping
------------------------+--------------------------------
     Reporter:  teor    |      Owner:
         Type:  defect  |     Status:  new
     Priority:  Medium  |  Milestone:  Tor: 0.2.8.x-final
    Component:  Tor     |    Version:  Tor: unspecified
     Severity:  Normal  |   Keywords:
Actual Points:          |  Parent ID:
       Points:  small   |    Sponsor:
------------------------+--------------------------------
 safe_timer_diff is meant to avoid overflow (or perhaps negative return
 values) but doesn't. (It was introduced to tor 0.2.8.0-alpha-dev in
 #3199.)

 For example:
 * safe_timer_diff(INT_MIN, INT_MAX) returns -1 on a system where
 TIME_T_IS_SIGNED. It should return a (clipped) value representing the
 largest integer difference possible, such as INT_MAX.

 I'm sure there are equivalent issues where TIME_T_IS_UNSIGNED, but I can't
 think of any right now.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17682>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online