[tor-bugs] #26924 [Core Tor/Tor]: Make single onion service to rend and Tor2web to intro link authentication into a protocol warning

[Tor Bug Tracker & Wiki]

#26924: Make single onion service to rend and Tor2web to intro link authentication
into a protocol warning
-------------------------+-------------------------------------------------
     Reporter:  teor     |      Owner:  teor
         Type:  defect   |     Status:  assigned
     Priority:  Medium   |  Milestone:  Tor: 0.3.5.x-final
    Component:  Core     |    Version:  Tor: 0.3.2.4-alpha
  Tor/Tor                |   Keywords:  tor-relay, certs, handshake,
     Severity:  Normal   |  ed25519, 035-roadmap-proposed, 035-must, fast-
                         |  fix, 035-triaged-in-20180711
Actual Points:           |  Parent ID:  #26627
       Points:           |   Reviewer:
      Sponsor:           |
-------------------------+-------------------------------------------------
 Single onion services and Tor2web connect directly to relays using
 untrusted link authentication keys.

 These connections can cause a lot of warnings, particularly due to the
 link auth bugs in #26627.

 We can either:
 * downgrade all link auth warnings to protocol warnings on single onion
 services and Tor2web (this is the fast fix)
 * taint untrusted link auth keys, and then downgrade connections using
 tainted keys to protocol warnings (this is very intrusive)

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26924>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online