[tor-bugs] #30875 [Core Tor/Tor]: If you start Tor with UseBridges 1, no ClientTransportPlugin, and only obfs4 bridges, it should fail

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#30875: If you start Tor with UseBridges 1, no ClientTransportPlugin, and only
obfs4 bridges, it should fail
------------------------------+--------------------
     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:                |
------------------------------+--------------------
 If you start your Tor client with just this line:
 {{{
 usebridges 1
 }}}
 it will refuse to start, because you gave it no bridges:
 {{{
 Jun 13 00:06:48.337 [warn] Failed to parse/validate config: If you set
 UseBridges, you must specify at least one bridge.
 Jun 13 00:06:48.337 [err] Reading config failed--see warnings above.
 }}}

 But if instead you start it with
 {{{
 usebridges 1
 bridge obfs4 85.17.30.79:443 FC259A04A328A07FED1413E9FC6526530D9FD87A
 cert=RutxZlu8BtyP+y0NX7bAVD41+J/qXNhHUrKjFkRSdiBAhIHIQLhKQ2HxESAKZprn/lR3KA
 iat-mode=0
 }}}
 it will start up, trying to treat that bridge as a vanilla bridge:
 {{{
 Jun 13 00:10:23.164 [notice] Bootstrapped 0% (starting): Starting
 Jun 13 00:10:23.278 [notice] Starting with guard context "bridges"
 Jun 13 00:10:23.279 [notice] Delaying directory fetches: No running
 bridges
 Jun 13 00:10:24.153 [notice] Bootstrapped 5% (conn): Connecting to a relay
 Jun 13 00:10:24.247 [notice] Bootstrapped 10% (conn_done): Connected to a
 relay
 }}}

 That is, it's trying to connect to an ORPort on 85.17.30.79:443,
 presumably to fetch a bridge descriptor. Of course that isn't working
 because that's an obfs4 port.

 Should Tor not count bridges for transports it doesn't have a
 ClientTransportPlugin line for, and if it ends up with no bridges that it
 knows how to use, refuse that configuration in the same way that it does
 now for no bridges?

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/30875>
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