Re: Strange CONNECT entries in apache logs

From: Christian Vogel (chris@netlynx-server.net)
Date: Thu Jul 10 2003 - 10:01:26 PDT

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    Hi,
    
    On Thu, Jul 10, 2003 at 01:52:17AM -0000, sgaskinsat_private wrote:
    > 172.150.203.171 - - [09/Jul/2003:17:58:00 -0400] "POST 
    > http://172.150.203.171:25/ HTTP/1.1" 200 781 "-" "-"
    
    What does happen here:
    
    If you use a http-proxy to proxy HTTP-POST requests the
    payload is most often forwarded verbatim. Of course, this request
    will have http-headers in front of the data, but many smtp-servers
    ignore those. So you can try to make a POST request like this
    via the proxy:
    
            POST http://victim:25/ HTTP/1.1
            Host: victim
            (empty line)
            HELO spammer
            MAIL FROM: <..>
            RCPT TO: <..>
            DATA
            spam
            .
    
    The SMTP-server will most likely complain about
    unsupported SMTP-commands "POST", "Host:", "X-Forwarded-For"
    and so on, but many will just silently accept the junkmail
    after these commands.
    
    Why back to the spammer's own IP-address:
    
    with the CONNECT the spammer can instantly see if he is talking
    to a SMTP-server and if it works. But to check how the proxy
    possibly mangles his POST-request he will have to check on a
    machine where he has access to the data as it comes out of the
    proxy.
    
            Chris
    
    
    
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