[tor-bugs] #17945 [Core Tor/Tor]: Stop Tor2Web connecting to (Rendezvous) Single Onion Services

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#17945: Stop Tor2Web connecting to (Rendezvous) Single Onion Services
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 Reporter:  teor                                 |          Owner:  teor
     Type:  enhancement                          |         Status:
 Priority:  Medium                               |  needs_information
Component:  Core Tor/Tor                         |      Milestone:  Tor:
 Severity:  Normal                               |  0.2.???
 Keywords:  rsos, sos, tor2web, tor-hs,          |        Version:
  029-proposed, 029-nickm-unsure, 029-teor-no,   |     Resolution:
  needs-design, needs-proposal-maybe             |  Actual Points:
Parent ID:                                       |         Points:  5
 Reviewer:                                       |        Sponsor:
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Comment (by teor):

 Split off #19662 and #19663 so that Tor2web and Single Onions build 3-hop
 paths on failure.
 Split off #19642 so that Single Onions tell Tor2web to use a 3-hop path to
 the intro and rendezvous.

 So the work remaining in this ticket is:
 * Relays should avoid being the only relay in a circuit between Tor2web
 and a Single Onion Service - so it isn't in a position to de-anonymise
 both client and service (this discourages attacks)
   * intro points and rend points should require one or both sides of the
 connection to be in the consensus

 I think it's ok for the intro and rend points to just use the consensus
 they have right now, even if it's a bit outdated. It's unlikely that both
 sides of a client to HS connection will be new in the consensus.
 Occasionally there will be a false positive on Tor2web to HS or client to
 Single Onion connections (but the retry will fix that).

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/17945#comment:19>
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