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<pre>Internet Engineering Task Force (IETF) R. Clayton
Request for Comments: 6692 University of Cambridge
Updates: <a href="./rfc6591">6591</a> M. Kucherawy
Category: Standards Track Cloudmark, Inc.
ISSN: 2070-1721 July 2012
<span class="h1">Source Ports in Abuse Reporting Format (ARF) Reports</span>
Abstract
This document defines an additional header field for use in Abuse
Reporting Format (ARF) reports to permit the identification of the
source port of the connection involved in an abuse incident.
This document updates <a href="./rfc6591">RFC 6591</a>.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in <a href="./rfc5741#section-2">Section 2 of RFC 5741</a>.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
<a href="http://www.rfc-editor.org/info/rfc6692">http://www.rfc-editor.org/info/rfc6692</a>.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
<span class="grey">Clayton & Kucherawy Standards Track [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc6692">RFC 6692</a> ARF Source Ports July 2012</span>
Table of Contents
<a href="#section-1">1</a>. Introduction ....................................................<a href="#page-2">2</a>
<a href="#section-2">2</a>. Keywords ........................................................<a href="#page-2">2</a>
<a href="#section-3">3</a>. Source-Port Field Definition ....................................<a href="#page-2">2</a>
<a href="#section-4">4</a>. Time Accuracy ...................................................<a href="#page-3">3</a>
<a href="#section-5">5</a>. IANA Considerations .............................................<a href="#page-3">3</a>
<a href="#section-6">6</a>. Security Considerations .........................................<a href="#page-3">3</a>
<a href="#section-7">7</a>. References ......................................................<a href="#page-4">4</a>
<a href="#section-7.1">7.1</a>. Normative References .......................................<a href="#page-4">4</a>
<a href="#section-7.2">7.2</a>. Informative References .....................................<a href="#page-4">4</a>
<a href="#appendix-A">Appendix A</a>. Acknowledgements .......................................<a href="#page-5">5</a>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
[<a id="ref-ARF">ARF</a>] defined the Abuse Reporting Format, an extensible message
format for Email Feedback Reports. These reports are used to report
incidents of email abuse. ARF was extended by [<a href="#ref-AUTHFAILURE-REPORT">AUTHFAILURE-REPORT</a>]
to enable the reporting of email authentication failures. These
specifications provided for the source IP address to be included in a
report. As explained in [<a href="#ref-LOG" title=""Logging Recommendations for Internet-Facing Servers"">LOG</a>], the deployment of IP address sharing
techniques requires the source port values to be included in reports
if unambiguous identification of the origin of abuse is to be
achieved.
This document defines an ARF reporting field to contain this
information and provides guidance for its use.
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Keywords</span>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [<a href="#ref-KEYWORDS">KEYWORDS</a>].
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Source-Port Field Definition</span>
A new ARF header field called "Source-Port" is defined. When present
in a report, it MUST contain the client port of the TCP connection
from which the reported message originated, corresponding to the
"Source-IP" field that contains the client address of that same
connection, thereby describing completely the origin of the abuse
incident.
Per, [<a href="#ref-ABNF" title=""Augmented BNF for Syntax Specifications: ABNF"">ABNF</a>], the formal syntax is:
source-port = "Source-Port:" [CFWS] 1*5DIGIT [CFWS] CRLF
<span class="grey">Clayton & Kucherawy Standards Track [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc6692">RFC 6692</a> ARF Source Ports July 2012</span>
"CFWS", which represents email-style comments or folding white space,
is imported from [<a href="#ref-MAIL" title=""Internet Message Format"">MAIL</a>].
When any report is generated that includes the "Source-IP" field (see
Section 3.2 of [<a href="#ref-ARF" title=""An Extensible Format for Email Feedback Reports"">ARF</a>]), this field SHOULD also be present, unless the
port number is unavailable.
Use of this field is RECOMMENDED for reports generated per
[<a href="#ref-AUTHFAILURE-REPORT">AUTHFAILURE-REPORT</a>] (see <a href="#section-3.1">Section 3.1</a> of that document).
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Time Accuracy</span>
[<a id="ref-LOG">LOG</a>] underscores the importance of accurate clocks when generating
reports that include source port information because of the fact that
source ports can be recycled very quickly in Internet Service
Provider environments. The same considerations described there apply
here.
Report generators that include an Arrival-Date report field MAY
choose to express the value of that date in Universal Coordinated
Time (UTC) to enable simpler correlation with local records at sites
that are following the provisions of [<a href="#ref-LOG" title=""Logging Recommendations for Internet-Facing Servers"">LOG</a>].
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. IANA Considerations</span>
IANA has added the following entry to the "Feedback Report Header
Fields" registry:
Field Name: Source-Port
Description: TCP source port from which the original message was
received
Multiple Appearances: No
Related "Feedback-Type": any
Reference: [<a href="./rfc6692">RFC6692</a>]
Status: current
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Security Considerations</span>
This extension introduces no new security considerations not already
covered in [<a href="#ref-ARF" title=""An Extensible Format for Email Feedback Reports"">ARF</a>].
Some security considerations related to the general topic of source
port logging can be found in [<a href="#ref-LOG" title=""Logging Recommendations for Internet-Facing Servers"">LOG</a>].
<span class="grey">Clayton & Kucherawy Standards Track [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc6692">RFC 6692</a> ARF Source Ports July 2012</span>
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. References</span>
<span class="h3"><a class="selflink" id="section-7.1" href="#section-7.1">7.1</a>. Normative References</span>
[<a id="ref-ABNF">ABNF</a>] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, <a href="./rfc5234">RFC 5234</a>, January 2008.
[<a id="ref-ARF">ARF</a>] Shafranovich, Y., Levine, J., and M. Kucherawy, "An
Extensible Format for Email Feedback Reports", <a href="./rfc5965">RFC 5965</a>,
August 2010.
[<a id="ref-AUTHFAILURE-REPORT">AUTHFAILURE-REPORT</a>]
Fontana, H., "Authentication Failure Reporting Using the
Abuse Reporting Format", <a href="./rfc6591">RFC 6591</a>, April 2012.
[<a id="ref-KEYWORDS">KEYWORDS</a>]
Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>, March 1997.
[<a id="ref-MAIL">MAIL</a>] Resnick, P., Ed., "Internet Message Format", <a href="./rfc5322">RFC 5322</a>,
October 2008.
<span class="h3"><a class="selflink" id="section-7.2" href="#section-7.2">7.2</a>. Informative References</span>
[<a id="ref-LOG">LOG</a>] Durand, A., Gashinsky, I., Lee, D., and S. Sheppard,
"Logging Recommendations for Internet-Facing Servers",
<a href="https://www.rfc-editor.org/bcp/bcp162">BCP 162</a>, <a href="./rfc6302">RFC 6302</a>, June 2011.
<span class="grey">Clayton & Kucherawy Standards Track [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc6692">RFC 6692</a> ARF Source Ports July 2012</span>
<span class="h2"><a class="selflink" id="appendix-A" href="#appendix-A">Appendix A</a>. Acknowledgements</span>
The authors wish to acknowledge the following for their review and
constructive criticism of this proposal: Steve Atkins, Scott
Kitterman, John Levine, and Doug Otis.
The idea for this work originated within the Messaging Anti-Abuse
Working Group (MAAWG).
Authors' Addresses
Richard Clayton
University of Cambridge
Computer Laboratory
JJ Thomson Avenue
Cambridge CB3 0FD
United Kingdom
Phone: +44 1223 763570
EMail: richard.clayton@cl.cam.ac.uk
Murray S. Kucherawy
Cloudmark, Inc.
128 King St., 2nd Floor
San Francisco, CA 94107
US
Phone: +1 415 946 3800
EMail: superuser@gmail.com
Clayton & Kucherawy Standards Track [Page 5]
</pre>
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