[tor-bugs] #25870 [Core Tor/Tor]: Fix vanguard restrictions

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#25870: Fix vanguard restrictions
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 Reporter:  mikeperry     |          Owner:  (none)
     Type:  defect        |         Status:  needs_review
 Priority:  Medium        |      Milestone:  Tor: 0.3.4.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:  #25546        |         Points:
 Reviewer:  asn           |        Sponsor:
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Comment (by asn):

 OK, the explanation above makes sense but it's also quite complicated. I'm
 gonna try to write some unittests and see if I can get a bit more
 confidence.

 Another design-level question: Why are we doing this change just for
 vanguard circuits and not for all circuits? Is it because we only aim to
 protect against guard-discovery attacks like #14917 only in vanguard
 circuits? Or because vanguard-circuits are naturally not 3-hops and so
 it's eaier to block A - B -A type circs? Or something else?

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25870#comment:6>
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