FTP state?
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Thread: FTP state?

  1. #1
    Member
    Join Date
    Feb 2002
    Posts
    42

    FTP state?

    Just a normal day-to-day gibberish chat.

    This just arrose as I was trying to get a dear freind of mine to browse the web while at work. Their FW was pretty strict, only allows two services out, ftp and telnet, and nothing in.

    As you expected, my freind wasn't satisfied with that at all, he wanted to browse the WWW, IRC, etc.., in breif, he wanted to enjoy his work-time :-).

    Well, first of all, there was the Q of how?
    ...................................................................................................................................................................................................................................................................................................................................................Found it!

    If our objective was getting a session to start from the end behind the FW to some party infront (not protected by) the FW, then we should use something that would allow an *extra* connection outbound, in other words, something that would allow a connection to go outbound without being refused by the connections table or by the rulebase.

    Since the only options we had were FTP and Telnet, we had to find a way around them. Telnet doesn't allow any forum of other-conn unlike FTP's PASV command.

    FTP uses to main forms of transmitting data, active and passive. Active means the server would open a connection from its side on port 20 to a random port on your side, this is considered inbound and usually isn't allowed by admins <even with stateful firewalls>, the other form is passive FTP. Passive works by telling the client where to connect to fetch a file <this method is preferred by admins so much > and therfor could be used in our little plethoria.

    The idea was simple, setup a firewall on your own home network with some string matching, NAT and active response magic.

    This problem was un-fixed although it is pretty simple.

    I'll just explain the scenario and you'll understand how it works <hopefully>
    The user connects to his home firewall using FTP <wich is actually just the FW listening for input on that port> issue the PASV command with the destination and port you wanna connect to, then your ftp session will give you a port number, just load whatever tool you want, and point it to your FW with a dport of whatever it returned.

    Simple eih?

    Now for the real Q,

    Does anyone have a fix to such a gay problem?

    Thanks
    etsh911
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  2. #2
    AntiOnline Senior Member souleman's Avatar
    Join Date
    Oct 2001
    Location
    Flint, MI
    Posts
    2,884
    umm, why not just telnet out to a shell account, and use lynx to browse the web?
    \"Ignorance is bliss....
    but only for your enemy\"
    -- souleman
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