[tor-bugs] #7144 [Tor]: Implement Bridge Guards and other anti-enumeration defenses

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#7144: Implement Bridge Guards and other anti-enumeration defenses
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 Reporter:  karsten                              |          Owner:
     Type:  project                              |         Status:
 Priority:  High                                 |  needs_review
Component:  Tor                                  |      Milestone:  Tor:
 Severity:  Normal                               |  0.2.8.x-final
 Keywords:  SponsorZ, tor-bridge,                |        Version:
  027-triaged-1-out, TorCoreTeam201509,          |     Resolution:
  028-triage, 028-triaged                        |  Actual Points:
Parent ID:                                       |         Points:  medium
  Sponsor:                                       |
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Changes (by nickm):

 * severity:   => Normal


Comment:

 Okay, I came here to drink coffee and review code, and my doctor tells me
 I shouldn't drink so much coffee.  I'll look at the smaller ones first.

 fbb21bbd9d21 Refactor loop over cpath for getting nicknames into separate
 function.
    * lgtm!
 43670da13937 Generalise logic for whether a circuit_t supports ntor.
    * Yes but we should also open a ticket here for removing
 *_supports_ntor() entirely; we no-longer allow TAP-only relays on the
 network.  (Opened as #17882)
 05d5eaa18985 Generalize logic for calculating cpath length.
    * lgtm
 04fd0097cd9a Refactor circuit_get_cpath_hop() to operate on just the
 cpath.
    * lgtm
 1568e1449278 Redefine CIRCUIT_IS_ORIGIN to use ORIGIN_CIRCUIT_MAGIC, not
 purpose.
    * lgtm.  There is a too-wide line here, I think, but please don't fix
 it now; I'll get it when I do "make check-spaces" after merge.
 6daf9165951d Make logic for choosing create cell type be agnostic to
 circuit type.
    * hmm. I know this isn't new, but the `!cpath->extend_info->onion_key`
 check looks poor to me, since it will fail once no-TAP relays are a
 reality.  Probably doesn't need to get fixed on this branch though.
 b5546456b415 Check circuit types before casting in
 relay_send_command_from_edge_().
    * If we're going to make this change, we need to recognize that this
 function isn't really "from_edge" any more -- a cell sent outwards from a
 bridge is not sent "from_edge".   Renaming this function might be
 overkill, but we should document its new semantics in its comments.
 e81acaf5f33e Implement Bridge Guards (prop188).
   * '''I'll come back to this in my next comment.  It's the big one.'''
 45d2457abd5c Add unittests for loose.c.
   * Changes to non-test code all lgtm
   * Tests seem okay after a quick skim.  If you haven't already done so,
 please run them under valgrind to make sure they don't leak.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/7144#comment:21>
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