[tor-bugs] #12971 [Tor]: Invalid SOCKS5 response to UDP associate request

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#12971: Invalid SOCKS5 response to UDP associate request
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     Reporter:  yurivict271  |      Owner:  rl1987
         Type:  defect       |     Status:  accepted
     Priority:  normal       |  Milestone:  Tor: 0.2.???
    Component:  Tor          |    Version:
   Resolution:               |   Keywords:  tor-client, easy
Actual Points:               |  Parent ID:
       Points:               |
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Comment (by rl1987):

 The above Python script was testing this behavior in slightly incorrect
 way, since it would send the UDP ASSOCIATE request right after
 establishing TCP connection to Tor. This is wrong way to do it, since
 SOCKS5 server expects to get version identifier/method selection message
 from client right after the TCP connection is established. If we send the
 UDP ASSOCIATE request when Socks listener is still in expecting-to-get-
 version-id/method-selection-message-from client state, it rightfully
 responds with METHOD selection message `05 00` (see section "3. Procedure
 for TCP-based clients" in RFC 1928).

 I have fixed this fault in Python script and made quick-and-dirty fix for
 SOCKS5 code as well. See https://github.com/rl1987/tor/tree/bug12971

 Testing it with fixed script:
 {{{
 >> 05 01 00
 << 05 00
 >> 05 03 00 01 08 08 08 08 00 35
 << 05 07 00 01 00 00 00 00 00 00
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12971#comment:9>
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