Full Disclosure mailing list archives
Re: Sidewinder G2
From: Michael Gale <michael () bluesuperman com>
Date: Tue, 18 Nov 2003 16:37:09 -0700
Oh my God -- I never said "And as you yourself note, A PROXY DOESN'T WORK IF IT DOESN'T PRESENT A SERVER INTERFACE ON ONE SIDE. At which point, as far as the protocol is concerned, it's a server." Look it you connect to a SMTP server, for example mail.bluesuperman.com this device accepts the message. If it was a relay server or gateway it would then forward the message onto another SMTP server and you would see this as a SMTP "hop" or MTA in the SMTP headers. The proxy can not and does not do this, a proxy does not accept a SMTP message and then forward it on, it accepts incoming packets and then forwards them on to another server after inspecting them. If you look at the message header of a e-mail that came from a out side server, through a SMTP application proxy to your internal SMTP server, you would not see the address of your smtp proxy machine in the mail headers. What I did say was -- you can have a smtp server with out a smtp proxy in front of it. The use would be connecting directly to the SMTP server. You can not have a successful SMTP proxy, if there is NO server somewhere to connect to. Which means, if you have a SMTP proxy on your firewall. That points to a internal exchange server (bad idea), a external SMTP server is sending the message to the exchange server, LOOK AT THE MESSAGE HEADERS !!!! --- the message can not be sent as in it will NOT leave the queue of the external SMTP server if the internal exchange server is down -- because the transaction could not be completed. That is what I said - now you are reading what you want to hear !!! If the proxy was a server -- then in the above example -- the message would NOT stay in the remote queue because your proxy would accept the message, keep it in it's queue and the forward it to the exchange server. But then you would see this in your message headers. Also if you did this -- how would you be able to tell who the message was coming from ? Everything would look like it came from your version of the SMTP proxy -- RBL's would not work, Reverse DNS checks, MX checks would not work also. Quit wording the RFC into what you want it to be. Look up SMTP servers, SMTP relay servers and then look at the code or tcpdump and see what a proxy does. As long are you are reading RFC's I believe it states that every time a message passes through a SMTP server that it most show that in the message headers. So again -- going through a proxy does not show this in a message header. Michael On Wed, 19 Nov 2003 01:05:39 -0500 Valdis.Kletnieks () vt edu wrote:
On Tue, 18 Nov 2003 15:23:21 MST, you said:A SMTP relay is NOT a SMTP application proxy -- A application level proxy is NOT a server.You're being *intentionally* obtuse now.If a application level proxy was a server, then why call it a proxy. Look at your definition of a proxy you provide. It does not say that IT is a server -- it goes to explain how it works using client and server references and comparisions.Yes, and if you actually read the rest of the spec,you'll find that they consider a proxy to be logically a server and a client glued back to back - a server side catching inbound client requests, and then a client side forwarding the requests to the destination - similarly for an SMTP gateway - it acts as a server on the one side, and as a client when it talks to the "real" server on the other side. And as you yourself note, A PROXY DOESN'T WORK IF IT DOESN'T PRESENT A SERVER INTERFACE ON ONE SIDE. At which point, as far as the protocol is concerned, it's a server. Or to quote 2821 some more: Section 2.3 provides definitions of terms specific to this document. Except when the historical terminology is necessary for clarity, this document uses the current 'client' and 'server' terminology to identify the sending and receiving SMTP processes, respectively. OK? Got that? If you're on the receiving end of an SMTP connection, YOU ARE A SERVER. If you're on the sending side, YOU ARE A CLIENT.
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Current thread:
- Sidewinder G2 Daniel Sichel (Nov 17)
- Re: Sidewinder G2 Shawn McMahon (Nov 17)
- Re: Sidewinder G2 Michael Gale (Nov 17)
- RE: Sidewinder G2 Paul Niranjan (Nov 18)
- Re: Sidewinder G2 Goetz Von Berlichingen (Nov 18)
- My take on the Newly discovered Exchange Flaw Lan Guy (Nov 18)
- Re: Sidewinder G2 Valdis . Kletnieks (Nov 18)
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- Re: Sidewinder G2 Michael Gale (Nov 18)
- Re: Sidewinder G2 Valdis . Kletnieks (Nov 18)
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- Re: Sidewinder G2 Michael Gale (Nov 18)
- Re: Sidewinder G2 Michael Gale (Nov 17)
- Re: Sidewinder G2 Shawn McMahon (Nov 17)
- <Possible follow-ups>
- RE: Sidewinder G2 Schmehl, Paul L (Nov 18)
- RE: Sidewinder G2 Ron DuFresne (Nov 20)
- RE: Sidewinder G2 Perrymon, Josh L. (Nov 18)
- Re: Sidewinder G2 Valdis . Kletnieks (Nov 18)
- RE: Sidewinder G2 Patrick Doyle (Nov 18)
- Re: Sidewinder G2 Michael Gale (Nov 18)
- RE: Sidewinder G2 Kruse, Steve (Nov 18)
- RE: Sidewinder G2 Brent J. Nordquist (Nov 18)