[tor-bugs] #22689 [Core Tor/Tor]: hs: Stop rend and intro points being used as single hop proxies

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#22689: hs: Stop rend and intro points being used as single hop proxies
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 Reporter:  teor          |          Owner:  dgoulet
     Type:  defect        |         Status:  needs_review
 Priority:  Medium        |      Milestone:  Tor: 0.3.3.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:  relay-safety  |  Actual Points:
Parent ID:  #17945        |         Points:  0.5
 Reviewer:  teor          |        Sponsor:
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Comment (by dgoulet):

 Replying to [comment:17 teor]:
 > Replying to [comment:16 teor]:
 > > v2 Intro:
 > >
 > > v2 Tor2web will extend to another intro point, and then succeed
 because it's no longer a single hop path.
 >
 > The client will only extend if it thinks that the service isn't
 connected to the intro point.
 > So maybe we shouldn't close intro circuits, but we should force them to
 extend instead?

 In theory, just a NACK received by the client will make it reuse the
 circuit and re-extend. See `handle_introduce_ack()`. This patch makes the
 intro return `HS_CELL_INTRO_ACK_NORELAY` which triggers a re-extend. Same
 goes for v2 in `rend_client_introduction_acked()`.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/22689#comment:18>
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