XEP-0065: SOCKS5 Bytestreams

SOCKS5 Bytestreams ("S5B")
out-of-band bytestream

Requester
    The entity that starts a bytestream negotiation with a Target. [7]
Target
    The entity with which the Requester is attempting to establish a bytestream.
Proxy
    An entity that is willing to be a middleman for the bytestream between the Requester and the Target.
StreamHost
    The system that the Target connects to and that is "hosting" the bytestream; the Streamhost can be either the Requester or a Proxy.
StreamID
    A relatively unique Stream ID for this connection; this is generated by the Requester for tracking purposes and MUST be less than 128 characters in length.

    * "----" ... communications over XMPP
    * "____" ... communications over TCP
    * "\\\\" and "////" ... communications over SOCKS 5
    * "====" ... communications over the bytestream itself



Direct Connections
In this situation, the StreamHost is the Requester

Requester                           Target
   |                                  |
   | Send S5B initiation request      |
   | -------------------------------> |
   |                                  |
   | Open TCP socket                  |
   | <_______________________________ |
   |                                  |
   | Request SOCKS 5 connection       |
   | <\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\ |
   |                                  |
   | Acknowledge SOCKS 5 connection   |
   | ///////////////////////////////> |
   |                                  |
   | Send S5B acceptance              |
   | <------------------------------- |
   |                                  |
   | Exchange data over S5B           |
   | <==============================> |
   |                

1. Requester Initiates S5B Negotiation

<iq from='[email protected]/foo'
    id='hu3vax16'
    to='[email protected]/bar'
    type='set'>
  <query xmlns='http://jabber.org/protocol/bytestreams'
         sid='vxf9n471bn46'>
    <streamhost
        jid='[email protected]/foo'
        host='192.168.4.1'
        port='5086'/>
  </query>
</iq>

2. the Target attempts to open a standard TCP socket on the network address of the StreamHost/Requester.

3. Target Establishes SOCKS5 Connection with StreamHost

CMD = X'01'
ATYP = X'03'
DST.ADDR = SHA1 Hash of: (SID + Requester JID + Target JID)
DST.PORT = 0

4. StreamHost Acknowledges Connection

STATUS = X'00'

5. Target Notifies Requester of Bytestream

<iq from='[email protected]/bar'
    id='hu3vax16'
    to='[email protected]/foo'
    type='result'>
  <query xmlns='http://jabber.org/protocol/bytestreams'
         sid='vxf9n471bn46'>
    <streamhost-used jid='[email protected]/foo'/>
  </query>
</iq>

Mediated Connections
In this situation, the StreamHost is not the Requester but a Proxy, which means that the Requester needs to discover the network address of the StreamHost before sending the initiation request to the Target, needs to negotiate a connection with the StreamHost in the same way that the Target does, and needs to ask the StreamHost to activate the bytestream before it can be used.

1. Requester Initiates Negotiation

<iq from='[email protected]/foo'
    id='npq71g53'
    to='[email protected]/bar'
    type='set'>
  <query xmlns='http://jabber.org/protocol/bytestreams'
         sid='vxf9n471bn46'>
    <streamhost
        host='24.24.24.1'
        jid='streamer.example.com'
        port='7625'/>
  </query>
</iq>

2. the Target attempts to open a standard TCP socket on the network address of the Proxy.

3. Target Establishes SOCKS5 Connection with StreamHost

CMD = X'01'
ATYP = X'03'
DST.ADDR = SHA1 Hash of: (SID + Requester JID + Target JID)
DST.PORT = 0

4. StreamHost Acknowledges Connection

STATUS = X'00'

5. Target Acknowledges Bytestream

<iq from='[email protected]/bar'
    id='npq71g53'
    to='[email protected]/foo'
    type='result'>
  <query xmlns='http://jabber.org/protocol/bytestreams'
         sid='vxf9n471bn46'>
    <streamhost-used jid='streamer.example.com'/>
  </query>
</iq>

6. Requester Establishes SOCKS5 Connection with StreamHost

CMD = X'01'
ATYP = X'03'
DST.ADDR = SHA1 Hash of: (SID + Requester JID + Target JID)
DST.PORT = 0

7. StreamHost Acknowledges Connection to Requester

STATUS = X'00'

8. Requester Requests Activation of Bytestream

<iq from='[email protected]/foo'
    id='oqx6t1c9'
    to='streamer.example.com'
    type='set'>
  <query xmlns='http://jabber.org/protocol/bytestreams'
         sid='vxf9n471bn46'>
    <activate>[email protected]/bar</activate>
  </query>
</iq>

9. Proxy Informs Requester of Activation

<iq from='streamer.example.com'
    id='oqx6t1c9'
    to='[email protected]/foo'
    type='result'/>