[tor-bugs] #32157 [Core Tor/Tor]: When bridges lines leave out the fingerprint, how should controllers look them up by id?

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#32157: When bridges lines leave out the fingerprint, how should controllers look
them up by id?
------------------------------+--------------------
     Reporter:  arma          |      Owner:  (none)
         Type:  defect        |     Status:  new
     Priority:  Medium        |  Milestone:
    Component:  Core Tor/Tor  |    Version:
     Severity:  Normal        |   Keywords:
Actual Points:                |  Parent ID:
       Points:                |   Reviewer:
      Sponsor:                |
------------------------------+--------------------
 In #32125 we have a case where the user configures a bridge line but
 leaves the optional fingerprint out. In this case Tor learns the
 fingerprint when it connects:
 {{{
 Oct 19 01:42:54.644 [notice] Learned fingerprint
 1948xxxxxxxxF6A25E456B7DB9C2D37EFB7250C1 for bridge x.y.153.221:9001.
 }}}
 But most controller events and responses list relays by their identity
 fingerprint, e.g. here is a line from 'getinfo circuit-status':
 {{{
 12 BUILT
 $1948xxxxxxxxF6A25E456B7DB9C2D37EFB7250C1~badabim,$E14D10669DD6E472235F8F0161544B4E7B7CB3C7~BOOTCHAROO2,$C3B451E071694ABA3AC2E75D49418E866072E051~HiddenNix,$1D04FF920CE804CE357FE62C665901C578BC26D6~tower
 BUILD_FLAGS=IS_INTERNAL,NEED_UPTIME PURPOSE=GENERAL
 TIME_CREATED=2019-10-19T05:42:56.257467
 }}}
 So when the controller wants to (for example) tell the user about their
 path, what is the right way for the controller to match up the relay id to
 the configured bridge?

 Tor Browser does it with 'getconf bridges' and looking through the id
 fingerprints of each configured bridge line until it finds a match. But if
 the bridge lines in torrc leave out the fingerprint, then you won't find
 the bridge that way.

 We should provide a recommended way for controllers to accomplish this
 goal (and that might involve building this new way into Tor).

 [I cc atagar and pospeselr because they write controllers and might have
 an opinion; and phw and cohosh because bridges.]

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/32157>
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