draft-ietf-dhc-dhcpv6-privacy-04.txt   draft-ietf-dhc-dhcpv6-privacy-05.txt 
dhc S. Krishnan dhc S. Krishnan
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Informational T. Mrugalski Intended status: Informational T. Mrugalski
Expires: August 19, 2016 ISC Expires: August 27, 2016 ISC
S. Jiang S. Jiang
Huawei Technologies Co., Ltd Huawei Technologies Co., Ltd
February 16, 2016 February 24, 2016
Privacy considerations for DHCPv6 Privacy considerations for DHCPv6
draft-ietf-dhc-dhcpv6-privacy-04 draft-ietf-dhc-dhcpv6-privacy-05
Abstract Abstract
DHCPv6 is a protocol that is used to provide addressing and DHCPv6 is a protocol that is used to provide addressing and
configuration information to IPv6 hosts. This document describes the configuration information to IPv6 hosts. This document describes the
privacy issues associated with the use of DHCPv6 by the Internet privacy issues associated with the use of DHCPv6 by the Internet
users. It is intended to be an analysis of the present situation and users. It is intended to be an analysis of the present situation and
does not propose any solutions. does not propose any solutions.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 19, 2016. This Internet-Draft will expire on August 27, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Identifiers in DHCPv6 options and fields . . . . . . . . . . 4 3. Identifiers in DHCPv6 options and fields . . . . . . . . . . 3
3.1. Source IPv6 address . . . . . . . . . . . . . . . . . . . 4 3.1. Source IPv6 address . . . . . . . . . . . . . . . . . . . 4
3.2. DUID . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. DUID . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Client Identifier Option . . . . . . . . . . . . . . . . 5 3.3. Client Identifier Option . . . . . . . . . . . . . . . . 5
3.4. IA_NA, IA_TA, IA_PD, IA Address and IA Prefix Options . . 5 3.4. IA_NA, IA_TA, IA_PD, IA Address and IA Prefix Options . . 5
3.5. Client FQDN Option . . . . . . . . . . . . . . . . . . . 5 3.5. Client FQDN Option . . . . . . . . . . . . . . . . . . . 5
3.6. Client Link-layer Address Option . . . . . . . . . . . . 6 3.6. Client Link-layer Address Option . . . . . . . . . . . . 6
3.7. Option Request Option . . . . . . . . . . . . . . . . . . 6 3.7. Option Request Option . . . . . . . . . . . . . . . . . . 6
3.8. Vendor Class and Vendor-specific Information Options . . 6 3.8. Vendor Class and Vendor-specific Information Options . . 6
3.9. Civic Location Option . . . . . . . . . . . . . . . . . . 7 3.9. Civic Location Option . . . . . . . . . . . . . . . . . . 7
3.10. Coordinate-Based Location Option . . . . . . . . . . . . 7 3.10. Coordinate-Based Location Option . . . . . . . . . . . . 7
3.11. Client System Architecture Type Option . . . . . . . . . 7 3.11. Client System Architecture Type Option . . . . . . . . . 7
3.12. Relay Agent Options . . . . . . . . . . . . . . . . . . . 7 3.12. Relay Agent Options . . . . . . . . . . . . . . . . . . . 7
3.12.1. Subscriber ID Option . . . . . . . . . . . . . . . . 8 3.12.1. Subscriber ID Option . . . . . . . . . . . . . . . . 7
3.12.2. Interface ID Option . . . . . . . . . . . . . . . . 8 3.12.2. Interface ID Option . . . . . . . . . . . . . . . . 8
3.12.3. Remote ID Option . . . . . . . . . . . . . . . . . . 8 3.12.3. Remote ID Option . . . . . . . . . . . . . . . . . . 8
3.12.4. Relay-ID Option . . . . . . . . . . . . . . . . . . 8 3.12.4. Relay-ID Option . . . . . . . . . . . . . . . . . . 8
4. Existing Mechanisms That Affect Privacy . . . . . . . . . . . 9 4. Existing Mechanisms That Affect Privacy . . . . . . . . . . . 8
4.1. Temporary addresses . . . . . . . . . . . . . . . . . . . 9 4.1. Temporary addresses . . . . . . . . . . . . . . . . . . . 9
4.2. DNS Updates . . . . . . . . . . . . . . . . . . . . . . . 9 4.2. DNS Updates . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Allocation strategies . . . . . . . . . . . . . . . . . . 9 4.3. Allocation strategies . . . . . . . . . . . . . . . . . . 9
5. Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Attacks . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Device type discovery (fingerprinting) . . . . . . . . . 11 5.1. Device type discovery (fingerprinting) . . . . . . . . . 11
5.2. Operating system discovery (fingerprinting) . . . . . . . 11 5.2. Operating system discovery (fingerprinting) . . . . . . . 11
5.3. Finding location information . . . . . . . . . . . . . . 11 5.3. Finding location information . . . . . . . . . . . . . . 11
5.4. Finding previously visited networks . . . . . . . . . . . 12 5.4. Finding previously visited networks . . . . . . . . . . . 12
5.5. Finding a stable identity . . . . . . . . . . . . . . . . 12 5.5. Finding a stable identity . . . . . . . . . . . . . . . . 12
5.6. Pervasive monitoring . . . . . . . . . . . . . . . . . . 12 5.6. Pervasive monitoring . . . . . . . . . . . . . . . . . . 12
5.7. Finding client's IP address or hostname . . . . . . . . . 13 5.7. Finding client's IP address or hostname . . . . . . . . . 13
5.8. Correlation of activities over time . . . . . . . . . . . 13 5.8. Correlation of activities over time . . . . . . . . . . . 13
5.9. Location tracking . . . . . . . . . . . . . . . . . . . . 13 5.9. Location tracking . . . . . . . . . . . . . . . . . . . . 13
5.10. Leasequery & bulk leasequery . . . . . . . . . . . . . . 14 5.10. Leasequery & bulk leasequery . . . . . . . . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 14 7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1. Normative References . . . . . . . . . . . . . . . . . . 15 10.1. Normative References . . . . . . . . . . . . . . . . . . 15
10.2. Informative References . . . . . . . . . . . . . . . . . 15 10.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
DHCPv6 [RFC3315] is a protocol that is used to provide addressing and DHCPv6 [RFC3315] is a protocol that is used to provide addressing and
configuration information to IPv6 hosts. DHCPv6 uses several configuration information to IPv6 hosts. DHCPv6 uses several
identifiers that could become a source for gleaning information about identifiers that could become a source for gleaning information about
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considered less important as they are typically open for public considered less important as they are typically open for public
services. And, it is generally assumed that relay agent to server services. And, it is generally assumed that relay agent to server
communication is protected from casual snooping, as that communication is protected from casual snooping, as that
communication occurs in the provider's backbone. Nevertheless, the communication occurs in the provider's backbone. Nevertheless, the
topics involving relay agents and servers are explored to some topics involving relay agents and servers are explored to some
degree. However, future work may want to further explore privacy of degree. However, future work may want to further explore privacy of
DHCPv6 servers and relay agents. DHCPv6 servers and relay agents.
2. Terminology 2. Terminology
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 [RFC2119]. When these
words are not in ALL CAPS (such as "should" or "Should"), they have
their usual English meanings, and are not to be interpreted as
[RFC2119] key words.
Naming convention from [RFC3315] and related is used throughout this Naming convention from [RFC3315] and related is used throughout this
document. In addition the following terminology is used: document. In addition the following terminology is used:
Stable identifier - Any property disclosed by a DHCPv6 client that Stable identifier - Any property disclosed by a DHCPv6 client that
does not change over time or changes very infrequently and is does not change over time or changes very infrequently and is
unique for said client in a given context. Examples include unique for said client in a given context. Examples include
MAC address, client-id, and a hostname. Some identifiers may MAC address, client-id, and a hostname. Some identifiers may
be considered stable only under certain conditions, for be considered stable only under certain conditions, for
example one client implementation may keep its client-id example one client implementation may keep its client-id
stored in stable storage while another may generate it on the stored in stable storage while another may generate it on the
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The Client Fully Qualified Domain Name (FQDN) option [RFC4704] is The Client Fully Qualified Domain Name (FQDN) option [RFC4704] is
used by DHCPv6 clients and servers to exchange information about the used by DHCPv6 clients and servers to exchange information about the
client's fully qualified domain name and about who has the client's fully qualified domain name and about who has the
responsibility for updating the DNS with the associated AAAA and PTR responsibility for updating the DNS with the associated AAAA and PTR
RRs. RRs.
A client can use this option to convey all or part of its domain name A client can use this option to convey all or part of its domain name
to a DHCPv6 server for the IPv6-address-to-FQDN mapping. In most to a DHCPv6 server for the IPv6-address-to-FQDN mapping. In most
case a client sends its hostname as a hint for the server. The case a client sends its hostname as a hint for the server. The
DHCPv6 server MAY be configured to modify the supplied name or to DHCPv6 server may be configured to modify the supplied name or to
substitute a different name. The server should send its notion of substitute a different name. The server should send its notion of
the complete FQDN for the client in the Domain Name field. the complete FQDN for the client in the Domain Name field.
3.6. Client Link-layer Address Option 3.6. Client Link-layer Address Option
The Client link-layer address option [RFC6939] is used by first-hop The Client link-layer address option [RFC6939] is used by first-hop
DHCPv6 relays to provide the client's link-layer address towards the DHCPv6 relays to provide the client's link-layer address towards the
server. server.
DHCPv6 relay agents that receive messages originating from clients DHCPv6 relay agents that receive messages originating from clients
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5.6. Pervasive monitoring 5.6. Pervasive monitoring
Pervasive Monitoring (PM) is widespread (and often covert) Pervasive Monitoring (PM) is widespread (and often covert)
surveillance through intrusive gathering of protocol artefacts, surveillance through intrusive gathering of protocol artefacts,
including application content, or protocol metadata such as headers. including application content, or protocol metadata such as headers.
Active or passive wiretaps and traffic analysis, (e.g., correlation, Active or passive wiretaps and traffic analysis, (e.g., correlation,
timing or measuring packet sizes), or subverting the cryptographic timing or measuring packet sizes), or subverting the cryptographic
keys used to secure protocols can also be used as part of pervasive keys used to secure protocols can also be used as part of pervasive
monitoring. PM is distinguished by being indiscriminate and very monitoring. PM is distinguished by being indiscriminate and very
large scale, rather than by introducing new types of technical large scale, rather than by introducing new types of technical
compromise. compromise. See [RFC7258] for a discussion about PM.
See [RFC7258] for a discussion about PM. In the DHCPv6 context, PM approach can be used to collect any
identifiers discussed in Section 3. DHCPv4 and DHCPv6 are especially
susceptible as the initial message sent (SOLICIT in case of DHCPv6)
is one of the very first packets sent when visiting a network.
Furthermore, in certain cases this packet can be logged even on
networks that do not support IPv6 (some implementations initiate
DHCPv6 even without receiving RA with M or O bits set). This may be
an easily overlooked attack vector when IPv6-capable device connects
to an IPv4 only network, gains only IPv4 connectivity, but still
leaks its stable identifiers over DHCPv6.
Using PM approach, attacks discussed in Sections 5.1, 5.2, 5.3, 5.4,
5.5, 5.7, 5.8 and possibly 5.9 apply.
5.7. Finding client's IP address or hostname 5.7. Finding client's IP address or hostname
Many DHCPv6 deployments use DNS Updates [RFC4704] that put client's Many DHCPv6 deployments use DNS Updates [RFC4704] that put client's
information (current IP address, client's hostname) into the DNS, information (current IP address, client's hostname) into the DNS,
where it is easily accessible by anyone interested. Client ID is where it is easily accessible by anyone interested. Client ID is
also disclosed, albeit in not easily accessible form (SHA-256 digest also disclosed, albeit in not easily accessible form (SHA-256 digest
of the client-id). As SHA-256 is considered irreversible, DHCID of the client-id). As SHA-256 is considered irreversible, DHCID
can't be converted back to client-id. However, SHA-256 digest can be can't be converted back to client-id. However, SHA-256 digest can be
used as an unique identifier that is accessible by any host. used as an unique identifier that is accessible by any host.
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8. IANA Considerations 8. IANA Considerations
This draft does not request any IANA action. This draft does not request any IANA action.
9. Acknowledgements 9. Acknowledgements
The authors would like to thank Stephen Farrell, Ted Lemon, Ines The authors would like to thank Stephen Farrell, Ted Lemon, Ines
Robles, Russ White, Christian Schaefer, Jinmei Tatuya, Bernie Volz, Robles, Russ White, Christian Schaefer, Jinmei Tatuya, Bernie Volz,
Marcin Siodelski, Christian Huitema, Brian Haberman, Robert Sparks, Marcin Siodelski, Christian Huitema, Brian Haberman, Robert Sparks,
Peter Yee and other members of DHC WG for their valuable comments. Peter Yee, Ben Campbell and other members of DHC WG for their
valuable comments.
This document was produced using the xml2rfc tool [RFC7749]. This document was produced using the xml2rfc tool [RFC7749].
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-6man-ipv6-address-generation-privacy] [I-D.ietf-6man-ipv6-address-generation-privacy]
Cooper, A., Gont, F., and D. Thaler, "Privacy Cooper, A., Gont, F., and D. Thaler, "Privacy
Considerations for IPv6 Address Generation Mechanisms", Considerations for IPv6 Address Generation Mechanisms",
draft-ietf-6man-ipv6-address-generation-privacy-08 (work draft-ietf-6man-ipv6-address-generation-privacy-08 (work
in progress), September 2015. in progress), September 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <http://www.rfc-editor.org/info/rfc3315>. 2003, <http://www.rfc-editor.org/info/rfc3315>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973, Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013, DOI 10.17487/RFC6973, July 2013,
<http://www.rfc-editor.org/info/rfc6973>. <http://www.rfc-editor.org/info/rfc6973>.
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