draft-ietf-cbor-network-addresses-09.txt   draft-ietf-cbor-network-addresses-10.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 C. Bormann Intended status: Standards Track C. Bormann
Expires: 26 March 2022 Universität Bremen TZI Expires: 9 April 2022 Universität Bremen TZI
22 September 2021 6 October 2021
CBOR tags for IPv4 and IPv6 addresses and prefixes CBOR tags for IPv4 and IPv6 addresses and prefixes
draft-ietf-cbor-network-addresses-09 draft-ietf-cbor-network-addresses-10
Abstract Abstract
This specification defines two CBOR Tags to be used with IPv6 and This specification defines two CBOR Tags for use with IPv6 and IPv4
IPv4 addresses and prefixes. addresses and prefixes.
// RFC-EDITOR-please-remove: This work is tracked at // RFC-EDITOR-please-remove: This work is tracked at
// https://github.com/cbor-wg/cbor-network-address // https://github.com/cbor-wg/cbor-network-address
Status of This Memo Status of This Memo
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This Internet-Draft will expire on 26 March 2022. This Internet-Draft will expire on 9 April 2022.
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
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Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Three Forms . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Three Forms . . . . . . . . . . . . . . . . . . . . . . . 3
3.1.1. Addresses . . . . . . . . . . . . . . . . . . . . . . 3 3.1.1. Addresses . . . . . . . . . . . . . . . . . . . . . . 3
3.1.2. Prefixes . . . . . . . . . . . . . . . . . . . . . . 3 3.1.2. Prefixes . . . . . . . . . . . . . . . . . . . . . . 3
3.1.3. Interface Definition . . . . . . . . . . . . . . . . 3 3.1.3. Interface Definition . . . . . . . . . . . . . . . . 4
3.2. IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. IPv4 . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3. IPv4 . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Encoder Considerations for Prefixes . . . . . . . . . . . . . 5 4. Encoder Considerations for Prefixes . . . . . . . . . . . . . 6
5. Decoder Considerations for Prefixes . . . . . . . . . . . . . 6 5. Decoder Considerations for Prefixes . . . . . . . . . . . . . 6
6. CDDL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 6. CDDL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8.1. Tag 54 - IPv6 . . . . . . . . . . . . . . . . . . . . . . 8 8.1. Tag 54 - IPv6 . . . . . . . . . . . . . . . . . . . . . . 9
8.2. Tag 52 - IPv4 . . . . . . . . . . . . . . . . . . . . . . 8 8.2. Tag 52 - IPv4 . . . . . . . . . . . . . . . . . . . . . . 9
8.3. Tags 260 and 261 . . . . . . . . . . . . . . . . . . . . 8 8.3. Tags 260 and 261 . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 8 9.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . 9 Appendix A. Changelog . . . . . . . . . . . . . . . . . . . . . 10
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
[RFC8949] defines a number of CBOR Tags for common items. Tags 260 [RFC8949] defines a number of CBOR Tags for common items. Tags 260
and 261 were later defined through IANA [IANA.cbor-tags]. These tags and 261 were later defined in drafts listed with IANA
cover addresses (260), and prefixes (261). Tag 260 distinguishes [IANA.cbor-tags]. These tags were intended to cover addresses (260)
between IPv6, IPv4 and Ethernet through the length of the byte string and prefixes (261). Tag 260 distinguishes between IPv6, IPv4, and
only. Tag 261 was not documented well enough to be used. MAC [RFC7042] addresses only through the length of the byte string
making it impossible, for example, to drop trailing zeros in the
encoding of IP addresses. Tag 261 was not documented well enough for
use.
This specification defines tags 54 and 52. These new tags are This specification defines tags 54 and 52 achieving an explicit
indication of IPv6 or IPv4 by the tag number. These new tags are
intended to be used in preference to tags 260 and 261. They provide intended to be used in preference to tags 260 and 261. They provide
formats for IPv6 and IPv4 addresses, prefixes, and addresses with formats for IPv6 and IPv4 addresses, prefixes, and addresses with
prefixes, achieving an explicit indication of IPv6 or IPv4. The prefixes, achieving an explicit indication of IPv6 or IPv4. The
prefix format omits trailing zeroes in the address part. (Due to the prefix format omits trailing zeroes in the address part. (Due to the
complexity of testing, the value of omitting trailing zeros for the complexity of testing, the value of omitting trailing zeros for the
pure address format was considered non-essential and support for that pure address format was considered non-essential and support for that
is not provided in this specification.) This specification does not is not provided in this specification.) This specification does not
deal with 6- or 8-byte Ethernet addresses. deal with 6- or 8-byte Ethernet addresses.
2. Terminology 2. Terminology
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where a prefix is expected, then it is to be assumed that all bits where a prefix is expected, then it is to be assumed that all bits
are relevant. That is, for IPv4, a /32 is implied, and for IPv6, a are relevant. That is, for IPv4, a /32 is implied, and for IPv6, a
/128 is implied. /128 is implied.
This form is called the Prefix Format. This form is called the Prefix Format.
3.1.3. Interface Definition 3.1.3. Interface Definition
When applied to an array that starts with a byte string, which stands When applied to an array that starts with a byte string, which stands
for an IP address, followed by an unsigned integer giving the bit for an IP address, followed by an unsigned integer giving the bit
length of a prefix built out of the first "length" bits of the length of a prefix built out of the first length bits of the address,
address, they represent information that is commonly used to specify they represent information that is commonly used to specify both the
both the network prefix and the IP address of an interface. network prefix and the IP address of an interface.
The length of the byte string is always 16 bytes (for IPv6) and 4
bytes (for IPv4).
This form is called the Interface Format. This form is called the Interface Format.
Interface Format definitions support an optional third element to the
array, which is to be used as the IPv6 Link-Local interface
identifier Section 4 of [RFC3542]. This may be an integer, in which
case it is to be interpreted as the interface index. This may be a
string, in which case it is to be interpreted as an interface name.
In the cases where the Interface Format is being used to represent
only an address with an interface identifier, and no interface prefix
information, then the prefix length may be replaced with the CBOR
"false" (0xF4).
3.2. IPv6 3.2. IPv6
IANA has allocated tag 54 for IPv6 uses. (Note that this is the IANA has allocated tag 54 for IPv6 uses. (This is the ASCII code for
ASCII code for '6'.) '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
(Section 3.1 of [RFC8949], major type 2), enclosed in Tag number 54. (Section 3.1 of [RFC8949], major type 2), enclosed in Tag number 54.
For example: For example:
54(h'20010db81234DEEDBEEFCAFEFACEFEED') 54(h'20010db81234deedbeefcafefacefeed')
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 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, configuring an interface, is to be encoded as a two element array,
with the (full-length) IPv6 address first and the length of the with the (full-length) IPv6 address first and the length of the
associated network the prefix next. associated network the prefix next.
For example: For example:
54([h'20010db81234DEEDBEEFCAFEFACEFEED', 56]) 54([h'20010db81234deedbeefcafefacefeed', 56])
Note that the address-with-prefix form can be reliably distinguished The address-with-prefix form can be reliably distinguished from the
from the prefix form only in the sequence of the array elements. prefix form only in the sequence of the array elements.
Some example of a link-local IPv6 address with a 64-bit prefix:
54([h'fe8000000000020202fffffffe030303', 64, 'eth0'])
with a numeric interface identifier:
54([h'fe8000000000020202fffffffe030303', 64, 42])
An IPv6 link-local address without a prefix length:
54([h'fe8000000000020202fffffffe030303', false, 42])
Interface identifiers may be used with any kind of IPv6 address, not
just Link-Local addresses. In particular, they are valid for
multicast addresses, and there may still be some significance for
Globally Unique Addresses (GUA).
3.3. IPv4 3.3. IPv4
IANA has allocated tag 52 for IPv4 uses. (Note that this is the IANA has allocated tag 52 for IPv4 uses. (This is the ASCII code for
ASCII code for '4'.) '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
(Section 3.1 of [RFC8949], major type 2), enclosed in Tag number 52. (Section 3.1 of [RFC8949], major type 2), enclosed in Tag number 52.
For example: For example:
52(h'C0000201') 52(h'c0000201')
An IPv4 prefix, such as 192.0.2.0/24 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 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, configuring an interface, is to be encoded as a two element array,
with the (full-length) IPv4 address first and the length of the with the (full-length) IPv4 address first and the length of the
associated network the prefix next. associated network the prefix next.
For example, 192.0.2.1/24 is to be encoded as a two element array, 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. with the length of the prefix (implied 192.0.2.0/24) last.
52([h'C0000201', 24]) 52([h'c0000201', 24])
Note that the address-with-prefix form can be reliably distinguished The address-with-prefix form can be reliably distinguished from the
from the prefix form only in the sequence of the array elements. prefix form only in the sequence of the array elements.
4. Encoder Considerations for Prefixes 4. Encoder Considerations for Prefixes
For the byte strings used in representing prefixes, an encoder MUST For the byte strings used in representing prefixes, an encoder MUST
omit any right-aligned (trailing) sequence of bytes that are all omit any right-aligned (trailing) sequence of bytes that are all
zero. zero.
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 encoded as: prefix length. For instance, the prefix 2001:db8::/64 is encoded as:
54([64, h'20010db8']) 54([64, h'20010db8'])
An encoder MUST take care to set all trailing bits in the final byte An encoder MUST take care to set all trailing bits in the final byte
to zero, if any. While decoders are expected to ignore them, such to zero, if any. While decoders are expected to ignore them, such
garbage entities could be used as a covert channel, or may reveal the garbage entities could be used as a covert channel, or may reveal the
state of what would otherwise be private memory contents. So for state of what would otherwise be private memory contents. So for
example, "2001:db8:1230::/44" MUST be encoded as: example, 2001:db8:1230::/44 MUST be encoded as:
52([44, h'20010db81230']) 52([44, h'20010db81230'])
even though variations like: even though variations like:
54([44, h'20010db81233']) WRONG 54([44, h'20010db81233'])
54([45, h'20010db8123f']) WRONG 54([45, h'20010db8123f'])
would be parsed in the exact same way. would be parsed in the exact same way; they MUST be considered
invalid.
The same considerations apply to IPv4 prefixes. The same considerations apply to IPv4 prefixes.
5. Decoder Considerations for Prefixes 5. Decoder Considerations for Prefixes
A decoder MUST consider all bits to the right of the prefix length to A decoder MUST consider all bits to the right of the prefix length to
be zero. be zero.
A decoder MUST handle the case where a prefix length specifies that A decoder MUST handle the case where a prefix length specifies that
more bits are relevant than are actually present in the byte-string. more bits are relevant than are actually present in the byte-string.
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Then taking whichever is smaller between (a) the length of the Then taking whichever is smaller between (a) the length of the
included byte-string, and (b) the number of bytes covered by the included byte-string, and (b) the number of bytes covered by the
prefix-length rounded up to the next multiple of 8: fail if that prefix-length rounded up to the next multiple of 8: fail if that
number is greater than 16 (or 4), and then copy that many bytes from number is greater than 16 (or 4), and then copy that many bytes from
the byte-string into the array. the byte-string into the array.
Finally, looking at the last three bits of the prefix-length in bits Finally, looking at the last three bits of the prefix-length in bits
(that is, the prefix-length modulo 8), use a static array of 8 values (that is, the prefix-length modulo 8), use a static array of 8 values
to force the lower, non-relevant bits to zero, or simply: to force the lower, non-relevant bits to zero, or simply:
unused_bits = (-prefix_length_in_bits) & 7; unused_bits = (8 - (prefix_length_in_bits & 7)) % 8;
if (length_in_bytes > 0) if (length_in_bytes > 0)
address_bytes[length_in_bytes - 1] &= (0xFF << unused_bits); address_bytes[length_in_bytes - 1] &= (0xFF << unused_bits);
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.
if (length_in_bytes > 0 && if (length_in_bytes > 0 &&
(address_bytes[length_in_bytes - 1] & ~(0xFF << unused_bits)) (address_bytes[length_in_bytes - 1] & ~(0xFF << unused_bits))
!= 0) != 0)
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ipv6-address-or-prefix = #6.54(ipv6-address / ipv6-address-or-prefix = #6.54(ipv6-address /
ipv6-address-with-prefix / ipv6-address-with-prefix /
ipv6-prefix) ipv6-prefix)
ipv4-address-or-prefix = #6.52(ipv4-address / ipv4-address-or-prefix = #6.52(ipv4-address /
ipv4-address-with-prefix / ipv4-address-with-prefix /
ipv4-prefix) ipv4-prefix)
ipv6-address = bytes .size 16 ipv6-address = bytes .size 16
ipv4-address = bytes .size 4 ipv4-address = bytes .size 4
ipv6-address-with-prefix = [ipv6-address, ipv6-prefix-length] ipv6-address-with-prefix = [ipv6-address, ipv6-prefix-value,
?ipv6-interface-identifier]
ipv4-address-with-prefix = [ipv4-address, ipv4-prefix-length] ipv4-address-with-prefix = [ipv4-address, ipv4-prefix-length]
ipv6-prefix-value = ipv6-prefix-length
/ false
ipv6-prefix-length = 0..128 ipv6-prefix-length = 0..128
ipv4-prefix-length = 0..32 ipv4-prefix-length = 0..32
ipv6-prefix = [ipv6-prefix-length, ipv6-prefix-bytes] ipv6-prefix = [ipv6-prefix-length, ipv6-prefix-bytes]
ipv4-prefix = [ipv4-prefix-length, ipv4-prefix-bytes] ipv4-prefix = [ipv4-prefix-length, ipv4-prefix-bytes]
ipv6-prefix-bytes = bytes .size (uint .le 16) ipv6-prefix-bytes = bytes .size (uint .le 16)
ipv4-prefix-bytes = bytes .size (uint .le 4) ipv4-prefix-bytes = bytes .size (uint .le 4)
ipv6-interface-identifier = uint / tstr
Figure 1 Figure 1
7. Security Considerations 7. Security Considerations
Identifying which byte sequences in a protocol are addresses may This document provides an CBOR encoding for IPv4 and IPv6 address
allow an attacker or eavesdropper to better understand what parts of information. Any applications using these encodings will need to
a packet to attack. That information, however, is likely to be found consider the security implications of this data in their specific
in the relevant RFCs anyway, so this is not a significant exposure. context. For example, identifying which byte sequences in a protocol
are addresses may allow an attacker or eavesdropper to better
understand what parts of a packet to attack.
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.
There are many ways in which the encodings may be invalid: wrong byte
lengths (too long, too short), or invalid prefix lengths (greater
than 32 for IPv4, greater than 128 for IPv6, negative values, etc.)
These are all invalid and this error needs to be signaled to the
application, and the entire content thrown away.
8. 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
[IANA.cbor-tags]: [IANA.cbor-tags]:
8.1. Tag 54 - IPv6 8.1. Tag 54 - IPv6
Data Item: byte string or array Data Item: byte string or array
Semantics: IPv6, [prefixlen,IPv6], [IPv6,prefixpart] Semantics: IPv6, [prefixlen,IPv6], [IPv6,prefixpart]
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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>.
9.2. Informative References 9.2. Informative References
[IANA.cbor-tags] [IANA.cbor-tags]
IANA, "Concise Binary Object Representation (CBOR) Tags", IANA, "Concise Binary Object Representation (CBOR) Tags",
<http://www.iana.org/assignments/cbor-tags>. <http://www.iana.org/assignments/cbor-tags>.
[RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
"Advanced Sockets Application Program Interface (API) for
IPv6", RFC 3542, DOI 10.17487/RFC3542, May 2003,
<https://www.rfc-editor.org/info/rfc3542>.
[RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and
IETF Protocol and Documentation Usage for IEEE 802
Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042,
October 2013, <https://www.rfc-editor.org/info/rfc7042>.
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 Roman Danyliw, Donald Eastlake, Ben Kaduk, Barry Leiba, and Eric
Vyncke reviewed the document and provided suggested text.
Authors' Addresses Authors' Addresses
Michael Richardson Michael Richardson
Sandelman Software Works Sandelman Software Works
Email: mcr+ietf@sandelman.ca Email: mcr+ietf@sandelman.ca
Carsten Bormann Carsten Bormann
Universität Bremen TZI Universität Bremen TZI
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