Tunnelling nntp

From: Lisa Becktold {CADIG STAFF} (lisa_at_cadig2.usna.navy.mil)
Date: 06/20/03

  • Next message: Michael Bruckmeier: "remote-controlled printing" 
    Date: 20 Jun 2003 17:13:52 -0400

    Hi:

    I have been told that my incoming Internet News feed (nntp/port 119) must
    be tunnelled over ssh. Port 119 will be shut down at the firewall;
    the only way I can get a newsfeed is if my remote news server tunnels
    the newsfeed through ssh to get through our firewall and to my news server.

    So now I am trying to tunnel nntp over ssh. Once I figure it out,
    I will have to ask my remote news server if he will consider
    implementing the same thing.

    I have set up a test scenario between two local news servers within
    our firewall. One news server (server1) is the newsfeed; it's
    batching up article files for another news server (server2). Server1
    runs nntpsend to transfer the files to server2.

      *****************************************************************

    NOTE: In the "real" world, outside the test scenario, a remote news
    server is my actual newsfeed. That remote server will have to tunnel the
    feed through ssh to get through our firewall and reach my news server.
    Server1 is standing in for that remote news server in my test scenario.
    Whatever I implement on server1 will have to be implemented on the
    remote news server.

      *****************************************************************

    I need a sanity check! My understanding of ssh tunnelling may be
    simplistic or downright wrong. Here's what I'm doing:

    On server1, I type this command:

            /usr/local/bin/ssh -v -L 3002:localhost:119 server2

    I'm assuming (perhaps incorrectly) that:

            . nntp traffic on server1 is now routed to local port 3002;
            
            . ssh encrypts traffic going to 3002 and sends it through the
              ssh connection to the remote machine (server2)
              
            . The "remote" machine, server2, receives the data
              sent over the ssh connection, decrypts it and sends it
              to port 119 on server2

            . Any status info that server2 generates is sent
              from 119 to ssh, and routed back to server1 via the ssh
              connection. Once the status info reaches server1, it is
              decrypted and sent to port 3002.

    Is this correct? Or have I misunderstood?

    Now for some port checking...After typing the ssh command above, I type
    "netstat -a" on server1 to check port 3002, and see this entry:

           *.3002 *.* 0 0 0 0 LISTEN

    I'm assuming that I can now route nntp traffic from server1 (the newsfeed)
    to server2 through ssh. On server1, I type:

            nntpsend -d
            
    This actually sends the news articles, but I'm not sure they're being routed
    via port 3002 or ssh. When I look at "snoop" output, the only reference
    I see is to NNTP port 33250.

    # snoop server1
    Using device /dev/hme (promiscuous mode)
    server1 -> server2 NNTP C port=33250
            server2 -> server1 NNTP R port=33250
    server1 -> server2 NNTP C port=33250
            server2 -> server1 NNTP R port=33250 200 server2
    server1 -> server2 NNTP C port=33250
    server1 -> server2 NNTP C port=33250 mode stream\r\n
            server2 -> server1 NNTP R port=33250
            server2 -> server1 NNTP R port=33250 203 StreamOK.\r\n

    How do I ensure that an outside server tunnels through ssh to reach
    me? What are the commands that need to be executed? And how do
    I verify that the traffic is indeed going through the ssh port?

    Any clarification or advice would be much appreciated!!!!!

    Lisa 

    -- 
    ----------------------------------------------------------
      Lisa M. Becktold - lisa@usna.navy.mil, (410) 293-6480
               United States Naval Academy - CADIG          
    590 Holloway Road, Rickover Hall, Annapolis, MD 21402-5000
  • Next message: Michael Bruckmeier: "remote-controlled printing"

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