[tor-bugs] #25472 [Obfuscation/Snowflake]: snowflake-client's `-url` option is intolerant of a missing trailing slash.

Tor Bug Tracker & Wiki blackhole at torproject.org
Tue Mar 13 03:16:30 UTC 2018


#25472: snowflake-client's `-url` option is intolerant of a missing trailing slash.
---------------------------------------+--------------------
     Reporter:  dcf                    |      Owner:  (none)
         Type:  defect                 |     Status:  new
     Priority:  Medium                 |  Milestone:
    Component:  Obfuscation/Snowflake  |    Version:
     Severity:  Minor                  |   Keywords:  easy
Actual Points:                         |  Parent ID:
       Points:                         |   Reviewer:
      Sponsor:                         |
---------------------------------------+--------------------
 I was following [https://gitweb.torproject.org/pluggable-
 transports/snowflake.git/tree/server-
 webrtc/README.md?id=ff8f3851082e8f7f8b4c8b99b161be35020aeb67 server-
 webrtc's README] and I made a small mistake in the client torrc. Instead
 of
 {{{
 -url http://127.0.0.1:8080/
 }}}
 I had (no trailing slash):
 {{{
 -url http://127.0.0.1:8080
 }}}
 This caused the client to fail with this error:
 {{{
 2018/03/13 03:10:40 Negotiating via BrokerChannel...
 Target URL:
 Front URL:   127.0.0.1:8080
 2018/03/13 03:10:40 BrokerChannel Error: dial tcp: unknown port
 tcp/8080client
 2018/03/13 03:10:40 Failed to retrieve answer. Retrying in 10 seconds
 }}}

 This is because the URL to request is built using string concatenation. It
 built the string `"http://127.0.0.1:8080client"` instead of
 `"http://127.0.0.1:8080/client"`.

 https://gitweb.torproject.org/pluggable-
 transports/snowflake.git/tree/client/rendezvous.go?id=ff8f3851082e8f7f8b4c8b99b161be35020aeb67#n83
 {{{
 request, err := http.NewRequest("POST", bc.url.String()+"client", data)
 }}}

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25472>
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