[tor-bugs] #31964 [Core Tor/Tor]: Dir auths could withhold HSIntro 4 in their votes if the relay would be a buggy v3 intro point

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#31964: Dir auths could withhold HSIntro 4 in their votes if the relay would be a
buggy v3 intro point
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     Reporter:  arma          |      Owner:  (none)
         Type:  enhancement   |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
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 In #27841 we learned that some old relays have a buggy implementation when
 they're used as a new-style intro point, which is causing misery -- both
 inconsistent reachability for v3 onion services and extra load on the
 network.

 In
 https://trac.torproject.org/projects/tor/ticket/27841#comment:33 we
 thought that withholding the HSIntro 4 vote for buggy relays would require
 a new consensus method, but I don't think that is so: in
 networkstatus_compute_consensus() when we're crafting the consensus out of
 the votes, we do
 {{{
         smartlist_sort_strings(protocols);
         chosen_protocol_list = get_most_frequent_member(protocols);
 }}}

 So all we need to do is change authorities to vote different protovers for
 those relays in their votes, and once a majority of them are voting the
 new protovers, that's it.

 Mind you, the implementation looks a bit tricky at first, because right
 now the vote is simply created by passing through the protovers
 volunteered in the relay descriptor: see routerstatus_format_entry()'s
 {{{
   if (protocols) {
     smartlist_add_asprintf(chunks, "pr %s\n", protocols);
   }
 }}}
 but we could avoid all the parsing mess by some simpler logic like "if
 it's a bad version, and it's claiming the expected full protover string x,
 use the full string y instead".

 I'm waiting to hear from dgoulet what versions remain buggy with the
 HSIntro protocol 4. It might be that we have nothing to fix here, once
 we've bumped out all the obsolete relays from the network, and instead we
 should just keep in mind for the future that this situation is what
 protovers were meant for.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31964>
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