RFC 4581 PROPOSED STANDARD IPV6 · SECURITY
CGA extensions: Cryptographically Generated Addresses (CGA) Extension Field Format
A Type-Length-Value layout for the extension fields of Cryptographically Generated Addresses.
RFC EDITOR
Bagnulo, M. and J. Arkko, "Cryptographically Generated Addresses (CGA) Extension Field Format", RFC 4581, DOI 10.17487/RFC4581, October 2006, <https://www.rfc-editor.org/info/rfc4581>.
BIBTEX
@misc{rfc4581,
series = {Request for Comments},
number = 4581,
howpublished = {RFC 4581},
publisher = {RFC Editor},
doi = {10.17487/RFC4581},
url = {https://www.rfc-editor.org/info/rfc4581},
author = {M. Bagnulo and J. Arkko},
title = {{Cryptographically Generated Addresses (CGA) Extension Field Format}},
pagetotal = 4,
year = 2006,
month = oct,
} LINEAGE · FROM THE RFC INDEXOpen full graph →
RFC text
Contents
Network Working Group M. Bagnulo
Request for Comments: 4581 UC3M
Updates: 3972 J. Arkko
Category: Standards Track Ericsson
October 2006
Cryptographically Generated Addresses (CGA) Extension Field Format
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document defines a Type-Length-Value format for
Cryptographically Generated Address (CGA) Extensions. This document
updates RFC 3972.
Table of Contents
1. Introduction ....................................................2
2. CGA Extension Field Format ......................................2
3. IANA Considerations .............................................2
4. Security Considerations .........................................3
5. Acknowledgements ................................................3
6. Normative References ............................................3
1. Introduction
The Cryptographically Generated Address (CGA) specification [1]
defines Extension Fields that allow additional information to be
included in the CGA Parameter Data Structure. So far there seems to
be enough interest in including additional data items into the CGA
Parameter Data Structure through these Extension Fields that it seems
reasonable to expect that more than one mechanism will require its
usage. In order to simplify the addition of multiple data items,
this document updates RFC 3972 [1], and it defines a Type-Length-
Value format for the Extension Fields.
2. CGA Extension Field Format
Data items to be included in Extension Fields of the CGA Parameter
Data Structure MUST be encoded using the following Type-Length-Value
(TLV) format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extension Type | Extension Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Extension Data ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Extension Type: 16-bit identifier of the type of the Extension Field.
Extension Data Length: 16-bit unsigned integer. Length of the
Extension Data field of this option, in octets.
Extension Data: Variable-length field. Extension-Type-specific data.
3. IANA Considerations
The IANA has created and will maintain a registry entitled, "CGA
Extension Type". The values in this name space are 16-bit unsigned
integers. Initial values for the CGA Extension Type field are given
below; future assignments are to be made through Standards Action
[2]. Assignments consist of a name and the value.
As recommended in [3], this document makes the following assignments
for experimental and testing use: the value 0xFFFD, with name
Exp_FFFD; the value 0xFFFE, with name Exp_FFFE, and the value 0xFFFF,
with name Exp_FFFF.
4. Security Considerations
No security concerns are raised by the adoption of the CGA Extension
format described in this document. However, proper security analysis
is required when new CGA Extensions are defined in order to make sure
that they introduce no new vulnerabilities to the existing CGA
schemes.
5. Acknowledgements
Comments to this document were provided by Sam Hartman, Allison
Mankin, Pekka Savola, Thomas Narten, Tuomas Aura, Stefan Rommer,
Julien Laganier, and James Kempf.
6. Normative References
[1] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC
3972, March 2005.
[2] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[3] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692, January 2004.
Authors' Addresses
Marcelo Bagnulo
Universidad Carlos III de Madrid
Av. Universidad 30
Leganes, Madrid 28911
SPAIN
Phone: 34 91 6249500
EMail: marcelo@it.uc3m.es
URI: http://www.it.uc3m.es
Jari Arkko
Ericsson
Jorvas 02420
Finland
EMail: jari.arkko@ericsson.com
Full Copyright Statement
Copyright (C) The Internet Society (2006).
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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OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
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Acknowledgement
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Administrative Support Activity (IASA).
AI ELI5
On this page
PROBLEMCGA allows extension fields in its parameter data structure, but no standard format existed for packing more than one data item into them.
MECHANISMEach item is encoded as a 16-bit Extension Type, a 16-bit Extension Data Length in octets, and variable-length Extension Data.
WHY IT MATTERSFuture mechanisms can add data to CGA parameters in a uniform way, with a new IANA registry of extension types.
§1Why a Format Is Needed
The CGA specification, RFC 3972, defines Extension Fields that let extra information ride in the CGA Parameter Data Structure. The authors expect more than one mechanism to use them, so this memo updates RFC 3972 and defines a Type-Length-Value format to make adding several data items simple.
Many things might want to use the pocket, so there needs to be a tidy way to pack them.
§2The TLV Format
Data items in Extension Fields MUST use this layout: a 16-bit Extension Type identifying the kind of field, a 16-bit unsigned Extension Data Length giving the length of the data in octets, and then the variable-length Extension Data, whose meaning depends on the type.
Each note starts with its kind, then how long it is, then the note itself.
081624
| Field | Name | Size | Value | Description |
|---|---|---|---|---|
EXT-TYPE | Extension Type | 2 bytes | Identifier of the type of the Extension Field. | |
EXT-LENGTH | Extension Data Length | 2 bytes | Length of the Extension Data in octets. |
§3The Type Registry
IANA maintains a registry called "CGA Extension Type" whose values are 16-bit unsigned integers. Future assignments are made through Standards Action. For experimental and testing use, the memo assigns 0xFFFD (Exp_FFFD), 0xFFFE (Exp_FFFE) and 0xFFFF (Exp_FFFF).
There is an official list of note kinds, with three kinds set aside for trying things out.
§4Security Considerations
The format itself raises no security concerns. However, any new CGA extension needs proper security analysis to make sure it introduces no new vulnerabilities into the existing CGA schemes.
The label system is safe, but each new kind of note needs its own safety check.
§5References
[1]RFC 3972Aura, T., "Cryptographically Generated Addresses (CGA)", RFC 3972, March 2005.March 2005[2]RFC 2434Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.October 1998[3]RFC 3692Narten, T., "Assigning Experimental and Testing Numbers Considered Useful", BCP 82, RFC 3692, January 2004.January 2004