[tor-bugs] #20165 [Core Tor/Tor]: When a relay advertises a new, unreachable address, OR reachability can succeed via the old address

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#20165: When a relay advertises a new, unreachable address, OR reachability can
succeed via the old address
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     Reporter:  teor          |      Owner:
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:  Tor: 0.2.???
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 If a relay has advertised a reachable address in the past, and continues
 listening on the old address, clients and relays will continue to contact
 Tor on that address for a few hours.

 If the relay starts advertising a new, unreachable address, ORPort
 reachability will appear to succeed for that new address, because Tor
 doesn't (and probably can't) check the address clients are connecting to
 is the one it actually advertised.

 And Tor doesn't do ongoing reachability checks, so it publishes its
 descriptor based on the mistaken reachability, and assumes everthing is OK
 from then on.

 Fortunately, the mandatory DirPort check catches this in 0.2.8 and later.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20165>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online