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 Universit├Ąt 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
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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'])
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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
Universit├Ąt Bremen TZI
Germany
Email: cabo@tzi.org
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