Security Basics mailing list archives
RE: educating rDNS violators]
From: LordInfidel () directionweb com
Date: Mon, 27 Sep 2004 10:05:24 -0400
point of clarification...... when you or a server connects to a smtp server, regardless of the intent, the HELO (or EHLO for extended HELO) must be issued. It is the same as a SYN packet. So when the RFC talks rejecting connections it is assuming that the HELO command has been issued. The HELO(EHLO) command is the first step of communication between mail servers and is how each server initially identifies themselves. This is where the smtp server get's the IP address and or FQDN of the client. (I use the term client because it is a client/server connection, the sending smtp server is the client in this scenario) So the RFC does apply when talking about rejecting connections since all smtp transmissions occur via HELO(EHLO). -----Original Message----- From: Pat Moffitt [mailto:pmoffitt () wrv com] Sent: Thursday, September 23, 2004 5:19 PM To: security-basics () securityfocus com Subject: [RE: educating rDNS violators] I am not attempting to verify the HELO Command. I am attempting to verify the IP Address of the system that is trying to make the SMTP connection. As such, this section of the RFC does not apply. I see nothing in this RFC that applies to using RDNS to reject mail connections, only on using RDNS to verify HELO commands. Pat Moffitt MIS Administrator Western Recreational Vehicles, Inc. -------- Original Message -------- Subject: RE: educating rDNS violators Date: Tue, 31 Aug 2004 13:35:34 -0400 From: LordInfidel () directionweb com To: 'Derek Schaible' <dschaible () cssiinc com>, Niek <niek () packetstorm nu> CC: security-basics () securityfocus com [snip - to supply the relevent part of the message] 6. Section 5.2.5 of rfc1123 covers this quite explicitly. Rejecting mail based on RDNS ~~~***VIOLATES***~~~ the RFC: http://www.faqs.org/rfcs/rfc1123.html 5.2.5 HELO Command: RFC-821 Section 3.5 [snip]
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- RE: educating rDNS violators] LordInfidel (Sep 27)