Re: Another port forwarding question

From: Richard E. Silverman (slade@shore.net)
Date: 03/02/02 

From: slade@shore.net (Richard E. Silverman)
Date: 02 Mar 2002 17:34:15 -0500

>>>>> "joe" == joe <joe@invalid.address> writes:

    joe> From the ftp session I list the directory and get a file. I've
    joe> been capturing the session in a third window with tcpdump. When I
    joe> look at the tcpdump output I can see the directory listing and
    joe> the file I transferred in plain text. Same thing happens with and
    joe> without passive mode.

    joe> Anyone see what I'm doing wrong? Suggestions, slap upside the
    joe> head, etc welcome.

The only thing wrong is your expectations. The FTP protocol uses separate
TCP connections on dynamically-determined ports for data transfers (which
includes directory listings). Passive mode simply changes the direction
of these connections. Because of this (and other features), FTP is not
amenable to simple port forwarding. Your setup will only protect the FTP
control channel (which includes your password, so that's something).

There are SSH clients with FTP-specific forwarding, that munge the control
channel traffic and establish forwarding channels as needed to handle
FTP. The ssh.com product is one of them. 

-- 
  Richard Silverman
  slade@shore.net

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