Internet DRAFT - draft-gont-tcpm-tcp-mirrored-endpoints
draft-gont-tcpm-tcp-mirrored-endpoints
TCP Maintenance and Minor Extensions F. Gont
(tcpm) UTN-FRH / SI6 Networks
Internet-Draft March 29, 2012
Updates: 793 (if approved)
Intended status: Standards Track
Expires: September 30, 2012
Processing of TCP segments with Mirrored End-points
draft-gont-tcpm-tcp-mirrored-endpoints-00.txt
Abstract
This document describes a problem found in some popular
implementations regarding the processing of TCP segments in which the
local endpoint is equal to the remote endpoint. Additionally, it
formally updates RFC 793 clarifying how this scenario should be
handled.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on September 30, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Updating RFC 793 . . . . . . . . . . . . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 3
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 4
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1. Introduction
Some systems have been found to be unable to process TCP segments in
which the source endpoint {Source Address, Source Port} is the same
than the destination end-point {Destination Address, Destination
Port}. Such TCP segments have been reported to cause malfunction of
a number of implementations [CERT1996], and have been exploited in
the past to perform Denial of Service (DoS) attacks [Meltman1997].
While these packets are very very unlikely to exist in legitimate
scenarios, TCP should nevertheless be able to process them without
the need of any "extra" code.
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 RFC 2119 [RFC2119].
2. Updating RFC 793
TCP MUST be able to gracefully handle the case where the source end-
point (IP Source Address, TCP Source Port) is the same as the
destination end-point (IP Destination Address, TCP Destination Port).
A SYN segment in which the source end-point {Source Address,
Source Port} is the same as the destination end-point {Destination
Address, Destination Port} will result in a "simultaneous open"
scenario, such as the one described in page 32 of RFC 793
[RFC0793]. Therefore, those TCP implementations that correctly
handle simultaneous opens should already be prepared to handle
these unusual TCP segments.
3. IANA Considerations
This document has no IANA actions. The RFC Editor is requested to
remove this section before publishing this document as an RFC.
4. Security Considerations
This document describes a problem found in some popular
implementations regarding the processing of TCP instances in which
the local and the remote TCP endpoints are the equal. It formally
updates RFC 793, clarifying how such packets should be handled, thus
helping prevent unexpected behaviors in host implementations.
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5. Acknowledgements
The author would like to thank David Borman for a fruitful discussion
about this topic at IETF 73 (Minneapolis).
This document is based on the technical report "Security Assessment
of the Transmission Control Protocol (TCP)" [CPNI-TCP] written by
Fernando Gont on behalf of the UK CPNI.
Fernando Gont would like to thank the UK CPNI for their continued
support.
6. References
6.1. Normative References
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
6.2. Informative References
[CERT1996]
CERT, "CERT Advisory CA-1996-21: TCP SYN Flooding and IP
Spoofing Attacks", 1996,
<http://www.cert.org/advisories/CA-1996-21.html>.
[CPNI-TCP]
Gont, F., "CPNI Technical Note 3/2009: Security Assessment
of the Transmission Control Protocol (TCP)", 2009, <http:/
/www.gont.com.ar/papers/
tn-03-09-security-assessment-TCP.pdf>.
[Meltman1997]
Meltman, "new TCP/IP bug in win95. Post to the bugtraq
mailing-list", 1996,
<http://insecure.org/sploits/land.ip.DOS.html>.
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Author's Address
Fernando Gont
UTN-FRH / SI6 Networks
Evaristo Carriego 2644
Haedo, Provincia de Buenos Aires 1706
Argentina
Phone: +54 11 4650 8472
Email: fgont@si6networks.com
URI: http://www.si6networks.com
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