BEHAVE WG F. Gont Internet-Draft UTN/FRH Intended status: BCP October 27, 2008 Expires: April 30, 2009 Security implications arising from the non-modification of protocol header fields by Network Address Translators (NATs) draft-gont-behave-nat-security-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. This document may not be modified, and derivative works of it may not be created. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 30, 2009. Abstract This document analizes the security implications arising from the non-modification of some TCP and IP protocol header fields by Network Address Translators (NATs). Gont Expires April 30, 2009 [Page 1] Internet-Draft NAT security implications October 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Internet Protocol version 4 (IPv4) header fields . . . . . . . 3 2.1. Version . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. IHL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.3. Type of Service . . . . . . . . . . . . . . . . . . . . . . 3 2.4. Total Length . . . . . . . . . . . . . . . . . . . . . . . 3 2.5. Identification . . . . . . . . . . . . . . . . . . . . . . 3 2.6. Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.7. Fragment Offset . . . . . . . . . . . . . . . . . . . . . . 3 2.8. Time to Live . . . . . . . . . . . . . . . . . . . . . . . 3 2.9. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.10. Header Checksum . . . . . . . . . . . . . . . . . . . . . . 3 2.11. Source Address . . . . . . . . . . . . . . . . . . . . . . 3 2.12. Destination Address . . . . . . . . . . . . . . . . . . . . 3 2.13. Options . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.14. Padding . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Transmission Control Protocol (TCP) header fields . . . . . . . 3 3.1. Source Port . . . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Destination Port . . . . . . . . . . . . . . . . . . . . . 4 3.3. Sequence Number . . . . . . . . . . . . . . . . . . . . . . 4 3.4. Acknowledgment Number . . . . . . . . . . . . . . . . . . . 4 3.5. Data Offset . . . . . . . . . . . . . . . . . . . . . . . . 4 3.6. Reserved . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.7. Flags . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.8. Window . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.9. Checksum . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.10. Urgent Pointer . . . . . . . . . . . . . . . . . . . . . . 4 3.11. Options . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.12. Padding . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 4 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7.1. Normative References . . . . . . . . . . . . . . . . . . . 4 7.2. Informative References . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5 Intellectual Property and Copyright Statements . . . . . . . . . . 6 Gont Expires April 30, 2009 [Page 2] Internet-Draft NAT security implications October 2008 1. Introduction This document analizes the security implications arising from the non-modification of some TCP and IP protocol header fields by Network Address Translators (NATs). 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. Internet Protocol version 4 (IPv4) header fields 2.1. Version 2.2. IHL 2.3. Type of Service 2.4. Total Length 2.5. Identification 2.6. Flags 2.7. Fragment Offset 2.8. Time to Live 2.9. Protocol 2.10. Header Checksum 2.11. Source Address 2.12. Destination Address 2.13. Options 2.14. Padding 3. Transmission Control Protocol (TCP) header fields 3.1. Source Port Gont Expires April 30, 2009 [Page 3] Internet-Draft NAT security implications October 2008 3.2. Destination Port 3.3. Sequence Number 3.4. Acknowledgment Number 3.5. Data Offset 3.6. Reserved 3.7. Flags 3.8. Window 3.9. Checksum 3.10. Urgent Pointer 3.11. Options 3.12. Padding 4. Security Considerations 5. IANA Considerations This document has no actions for IANA. 6. Acknowledgements 7. References 7.1. Normative References [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, September 1981. [RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989. [RFC1323] Jacobson, V., Braden, B., and D. Borman, "TCP Extensions Gont Expires April 30, 2009 [Page 4] Internet-Draft NAT security implications October 2008 for High Performance", RFC 1323, May 1992. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 7.2. Informative References [RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address Translator (NAT) Terminology and Considerations", RFC 2663, August 1999. Author's Address Fernando Gont Universidad Tecnologica Nacional / Facultad Regional Haedo Evaristo Carriego 2644 Haedo, Provincia de Buenos Aires 1706 Argentina Phone: +54 11 4650 8472 Email: fernando@gont.com.ar URI: http://www.gont.com.ar Gont Expires April 30, 2009 [Page 5] Internet-Draft NAT security implications October 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Gont Expires April 30, 2009 [Page 6]