draft-ietf-cbor-network-addresses-04.txt		draft-ietf-cbor-network-addresses-05.txt
	CBOR Working Group M. Richardson		CBOR Working Group M. Richardson
	Internet-Draft Sandelman Software Works		Internet-Draft Sandelman Software Works
	Intended status: Standards Track 21 April 2021		Intended status: Standards Track C. Bormann
	Expires: 23 October 2021		Expires: 13 January 2022 Universität Bremen TZI
			12 July 2021
	CBOR tags for IPv4 and IPv6 addresses and prefixes		CBOR tags for IPv4 and IPv6 addresses and prefixes
	draft-ietf-cbor-network-addresses-04		draft-ietf-cbor-network-addresses-05
	Abstract		Abstract
	This document describes two CBOR Tags to be used with IPv4 and IPv6		This document describes two CBOR Tags to be used with IPv4 and IPv6
	addresses and prefixes.		addresses and prefixes.
	RFC-EDITOR-please remove: This work is tracked at https://github.com/		RFC-EDITOR-please remove: This work is tracked at https://github.com/
	cbor-wg/cbor-network-address		cbor-wg/cbor-network-address
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 34 ¶		skipping to change at page 1, line 35 ¶
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	Copyright Notice		Copyright Notice
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2021 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
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	and restrictions with respect to this document. Code Components		and restrictions with respect to this document. Code Components
	extracted from this document must include Simplified BSD License text		extracted from this document must include Simplified BSD License text
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	provided without warranty as described in the Simplified BSD License.		provided without warranty as described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
	3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 2		3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3.1. IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 2		3.1. IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3.2. IPv4 . . . . . . . . . . . . . . . . . . . . . . . . . . 3		3.2. IPv4 . . . . . . . . . . . . . . . . . . . . . . . . . . 3
	4. Encoder Consideration for prefixes . . . . . . . . . . . . . 3		4. Encoder Consideration for prefixes . . . . . . . . . . . . . 4
	5. Decoder Considerations for prefixes . . . . . . . . . . . . . 4		5. Decoder Considerations for prefixes . . . . . . . . . . . . . 5
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 4		6. CDDL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	7.1. Tag 54 - IPv6 . . . . . . . . . . . . . . . . . . . . . . 5		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
	7.2. Tag 52 - IPv4 . . . . . . . . . . . . . . . . . . . . . . 5		8.1. Tag 54 - IPv6 . . . . . . . . . . . . . . . . . . . . . . 7
	8. Normative References . . . . . . . . . . . . . . . . . . . . 5		8.2. Tag 52 - IPv4 . . . . . . . . . . . . . . . . . . . . . . 7
	Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . 5		9. Normative References . . . . . . . . . . . . . . . . . . . . 7
	Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6		Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . 7
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6		Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 8
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	[RFC8949] defines a number of CBOR Tags for common items.		[RFC8949] defines a number of CBOR Tags for common items.
	Not included are ones to indicate if the item is an IPv4 or IPv6		Tag 260 and tag 261 was later defined through IANA. These tags cover
	address, or if it is an address plus prefix length. This document		addresses (260), and prefixes (261). Tag 260 distinguishes between
	defines them.		IPv4, IPv6 and Ethernet through the length of the byte string only.
			Tag 261 was not documented well enough to be used.
			The present specification achieves an explicit indication of IPv4 or
			IPv6, and the possibility to omit trailing zeroes.
			This document provides a format for IPv6 and IPv4 addresses,
			prefixes, and addresses with prefixes. Prefixes MUST omit trailing
			zeroes in the address. Due to the complexity of testing the value of
			omitting trailing zeros for addresses was considered non-essential
			and support for that was removed in this specification.
			This document does not deal with 6 or 8-byte Ethernet addressees.
	2. Terminology		2. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in		"OPTIONAL" in this document are to be interpreted as described in
	BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all		BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
	capitals, as shown here.		capitals, as shown here.
	3. Protocol		3. Protocol
	These tags can applied to byte strings to represent a single address.		These tags can applied to byte strings to represent a single address.
	When applied to an array, the represent a CIDR-style prefix. When a		When applied to an array that starts with a number, they represent a
	byte string (without prefix) appears in a context where a prefix is		CIDR-style prefix of that length. When a byte string (without
	expected, then it is to be assumed that all bits are relevant. That		prefix) appears in a context where a prefix is expected, then it is
	is, for IPv4, a /32 is implied, and for IPv6, a /128 is implied.		to be assumed that all bits are relevant. That is, for IPv4, a /32
			is implied, and for IPv6, a /128 is implied.
			When applied to an array that starts with a byte string, that stands
			for an IP address, followed by the bit length of a prefix built out
			of the first "length" bits of the address.
	3.1. IPv6		3.1. IPv6
	IANA has allocated tag 54 for IPv6 uses. (Note that this is the		IANA has allocated tag 54 for IPv6 uses. (Note that this is the
	ASCII code for '6'.)		ASCII code for '6'.)
	An IPv6 address is to be encoded as a sixteen-byte byte string		An IPv6 address is to be encoded as a sixteen-byte byte string
	([RFC8949] section, 3.1, major type 2), prefixed with Tag(54).		(Section 3.1 of [RFC8949], major type 2), enclosed in Tag number 54.
	An IPv6 prefix, such as 2001:db8:1234::/48 is to be encoded as a two		An IPv6 prefix, such as 2001:db8:1234::/48 is to be encoded as a two
	element array, with the length of the prefix first. Trailing zero		element array, with the length of the prefix first. Trailing zero
	bytes MUST be omitted.		bytes MUST be omitted.
	For example:		For example:
	54([ 48, h'20010db81234'])		54([ 48, h'20010db81234'])
			An IPv6 address combined with a prefix length, such as being used for
			configuring an interface, is to be encoded as a two element array,
			with the (full-length) IPv6 address first and the length of the
			associated network the prefix next.
			For example:
			54([h'20010db81234DEEDBEEFCAFEFACEFEED', 56])
			Note that the address-with-prefix form can be reliably distinguished
			from the prefix form only in the sequence of the array elements.
	3.2. IPv4		3.2. IPv4
	IANA has allocated tag 54 for IPv4 uses. (Note that this is the		IANA has allocated tag 52 for IPv4 uses. (Note that this is the
	ASCII code for '4'.)		ASCII code for '4'.)
	An IPv4 address is to be encoded as a four-byte byte string		An IPv4 address is to be encoded as a four-byte byte string
	([RFC8949] section, 3.1, major type 2), prefixed with Tag(52).		(Section 3.1 of [RFC8949], major type 2), enclosed in Tag number 52.
	An IPv4 prefix, such as 192.0.2.1/24 is to be encoded as a two		An IPv4 prefix, such as 192.0.2.0/24 is to be encoded as a two
	element array, with the length of the prefix first. Trailing zero		element array, with the length of the prefix first. Trailing zero
	bytes MUST be omitted.		bytes MUST be omitted.
	For example:		For example:
	52([ 24, h'C00002'])		52([ 24, h'C00002'])
			An IPv4 address combined with a prefix length, such as being used for
			configuring an interface, is to be encoded as a two element array,
			with the (full-length) IPv4 address first and the length of the
			associated network the prefix next.
			For example, 192.0.2.1/24 is to be encoded as a two element array,
			with the length of the prefix (implied 192.0.2.0/24) last.
			52([ h'C0000201', 24])
			Note that the address-with-prefix form can be reliably distinguished
			from the prefix form only in the sequence of the array elements.
	4. Encoder Consideration for prefixes		4. Encoder Consideration for prefixes
	An encoder may omit as many right-hand (trailing) bytes which are all		An encoder may omit as many right-hand (trailing) bytes which are all
	zero as it wishes.		zero as it wishes.
	There is no relationship between the number of bytes omitted and the		There is no relationship between the number of bytes omitted and the
	prefix length. For instance, the prefix 2001:db8::/64 is optimally		prefix length. For instance, the prefix 2001:db8::/64 is optimally
	encoded as:		encoded as:
	54([64, h'20010db8'])		54([64, h'20010db8'])
	skipping to change at page 4, line 39 ¶		skipping to change at page 5, line 35 ¶
	the array.		the array.
	Finally, looking at the last three bits of the prefix-length (that		Finally, looking at the last three bits of the prefix-length (that
	is, the prefix-length modulo 8), use a static array of 8 values to		is, the prefix-length modulo 8), use a static array of 8 values to
	force the lower bits, non-relevant bits to zero.		force the lower bits, non-relevant bits to zero.
	A particularly paranoid decoder could examine the lower non-relevant		A particularly paranoid decoder could examine the lower non-relevant
	bits to determine if they are non-zero, and reject the prefix. This		bits to determine if they are non-zero, and reject the prefix. This
	would detect non-compliant encoders, or a possible covert channel.		would detect non-compliant encoders, or a possible covert channel.
	6. Security Considerations		6. CDDL
			For use with CDDL [RFC8610], the typenames defined in Figure 1 are
			recommended:
			ip-address-or-prefix = ipv6-address-or-prefix /
			ipv4-address-or-prefix
			ipv6-address-or-prefix = #6.54(ipv6-address /
			ipv6-address-with-prefix /
			ipv6-prefix)
			ipv4-address-or-prefix = #6.52(ipv4-address /
			ipv4-address-with-prefix /
			ipv4-prefix)
			ipv6-address = bytes .size 16
			ipv4-address = bytes .size 4
			ipv6-address-with-prefix = [ipv6-address, ipv6-prefix-length]
			ipv4-address-with-prefix = [ipv4-address, ipv4-prefix-length]
			ipv6-prefix-length = 0..128
			ipv4-prefix-length = 0..32
			ipv6-prefix = [ipv6-prefix-length, ipv6-prefix-bytes]
			ipv4-prefix = [ipv4-prefix-length, ipv4-prefix-bytes]
			ipv6-prefix-bytes = bytes .size (uint .le 16)
			ipv4-prefix-bytes = bytes .size (uint .le 4)
			Figure 1
			7. Security Considerations
	Identifying which byte sequences in a protocol are addresses may		Identifying which byte sequences in a protocol are addresses may
	allow an attacker or eavesdropper to better understand what parts of		allow an attacker or eavesdropper to better understand what parts of
	a packet to attack.		a packet to attack.
	Reading the relevant RFC may provide more information, so it would		Reading the relevant RFC may provide more information, so it would
	seem that any additional security that was provided by not being able		seem that any additional security that was provided by not being able
	to identify what are IP addresses falls into the security by		to identify what are IP addresses falls into the security by
	obscurity category.		obscurity category.
	The right-hand bits of the prefix, after the prefix-length, are		The right-hand bits of the prefix, after the prefix-length, are
	ignored by this protocol. A malicious party could use them to		ignored by this protocol. A malicious party could use them to
	transmit covert data in a way that would not affect the primary use		transmit covert data in a way that would not affect the primary use
	of this encoding. Such abuse would be detected by examination of the		of this encoding. Such abuse would be detected by examination of the
	raw protocol bytes. Users of this encoding should be aware of this		raw protocol bytes. Users of this encoding should be aware of this
	possibility.		possibility.
	7. IANA Considerations		8. IANA Considerations
	IANA has allocated two tags from the Specification Required area of		IANA has allocated two tags from the Specification Required area of
	the Concise Binary Object Representation (CBOR) Tags:		the Concise Binary Object Representation (CBOR) Tags:
	7.1. Tag 54 - IPv6		8.1. Tag 54 - IPv6
	Data Item: byte string or array		Data Item: byte string or array
	Semantics: IPv6 or [prefixlen,IPv6]		Semantics: IPv6, [prefixlen,IPv6], [IPv6,prefixpart]
	7.2. Tag 52 - IPv4		8.2. Tag 52 - IPv4
	Data Item: byte string or array		Data Item: byte string or array
	Semantics: IPv4 or [prefixlen,IPv4]		Semantics: IPv4, [prefixlen,IPv4], [IPv4,prefixpart]
	8. Normative References		9. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
			[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
			Definition Language (CDDL): A Notational Convention to
			Express Concise Binary Object Representation (CBOR) and
			JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
			June 2019, <https://www.rfc-editor.org/info/rfc8610>.
	[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object		[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
	Representation (CBOR)", STD 94, RFC 8949,		Representation (CBOR)", STD 94, RFC 8949,
	DOI 10.17487/RFC8949, December 2020,		DOI 10.17487/RFC8949, December 2020,
	<https://www.rfc-editor.org/info/rfc8949>.		<https://www.rfc-editor.org/info/rfc8949>.
	Appendix A. Changelog		Appendix A. Changelog
	This section is to be removed before publishing as an RFC.		This section is to be removed before publishing as an RFC.
	* 03		* 03
	* 02		* 02
	* 01 added security considerations about covert channel		* 01 added security considerations about covert channel
	Acknowledgements		Acknowledgements
	none yet		none yet
	Author's Address		Authors' Addresses
	Michael Richardson		Michael Richardson
	Sandelman Software Works		Sandelman Software Works
	Email: mcr+ietf@sandelman.ca		Email: mcr+ietf@sandelman.ca
			Carsten Bormann
			Universität Bremen TZI
			Germany
			Email: cabo@tzi.org
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