draft-ietf-dhc-relay-server-security-05.txt   rfc8213.txt 
Network Working Group B. Volz Internet Engineering Task Force (IETF) B. Volz
Internet-Draft Cisco Systems Request for Comments: 8213 Y. Pal
Intended status: Standards Track Y. Pal Category: Standards Track Cisco Systems
Expires: October 21, 2017 Cisco Systems, Inc. ISSN: 2070-1721 August 2017
April 19, 2017
Security of Messages Exchanged Between Servers and Relay Agents Security of Messages Exchanged between Servers and Relay Agents
draft-ietf-dhc-relay-server-security-05.txt
Abstract Abstract
The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) has no The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) has no
guidance for how to secure messages exchanged between servers and guidance for how to secure messages exchanged between servers and
relay agents. The Dynamic Host Configuration Protocol for IPv6 relay agents. The Dynamic Host Configuration Protocol for IPv6
(DHCPv6) states that IPsec should be used to secure messages (DHCPv6) states that IPsec should be used to secure messages
exchanged between servers and relay agents, but does not require exchanged between servers and relay agents but does not require
encryption. And, with recent concerns about pervasive monitoring and encryption. With recent concerns about pervasive monitoring and
other attacks, it is appropriate to require securing relay to relay other attacks, it is appropriate to require securing relay-to-relay
and relay to server communication for DHCPv6 and relay to server and relay-to-server communication for DHCPv6 and relay-to-server
communication for DHCPv4. communication for DHCPv4.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on October 21, 2017. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8213.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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 Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction ....................................................2
2. Requirements Language and Terminology . . . . . . . . . . . . 3 2. Requirements Language and Terminology ...........................3
3. Security of Messages Exchanged Between Servers and Relay 3. Security of Messages Exchanged between Servers and Relay
Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Agents ..........................................................3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations .........................................5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations .............................................5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 6. References ......................................................6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 6.1. Normative References .......................................6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6 6.2. Informative References .....................................6
7.2. Informative References . . . . . . . . . . . . . . . . . 6 Acknowledgments ....................................................8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses .................................................8
1. Introduction 1. Introduction
The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) [RFC2131] The Dynamic Host Configuration Protocol for IPv4 (DHCPv4) [RFC2131]
and [RFC1542] has no guidance for how to secure messages exchanged and the Bootstrap Protocol [RFC1542] have no guidance for how to
between servers and relay agents. The Dynamic Host Configuration secure messages exchanged between servers and relay agents. The
Protocol for IPv6 (DHCPv6) [RFC3315] states that IPsec should be used Dynamic Host Configuration Protocol for IPv6 (DHCPv6) [RFC3315]
to secure messages exchanged between servers and relay agents, but states that IPsec should be used to secure messages exchanged between
does not recommend encryption. And, with recent concerns about servers and relay agents but does not recommend encryption. With
pervasive monitoring [RFC7258], it is appropriate to require use of recent concerns about pervasive monitoring [RFC7258], it is
IPsec with encryption for relay to server communication for DHCPv4 appropriate to require use of IPsec with encryption for relay-to-
and require use of IPsec with encryption for relay to relay and relay server communication for DHCPv4 and require use of IPsec with
to server communication for DHCPv6. encryption for relay-to-relay and relay-to-server communication for
DHCPv6.
This document specifies the optional requirements for relay agent and This document specifies the optional requirements for relay agent and
server implementations to support IPsec authentication and encryption server implementations to support IPsec authentication and encryption
and recommends operators enable this IPsec support. and recommends that operators enable this IPsec support.
2. Requirements Language and Terminology 2. Requirements Language and 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119] when they "OPTIONAL" in this document are to be interpreted as described in BCP
appear in ALL CAPS. When these words are not in ALL CAPS (such as 14 [RFC2119] [RFC8174] when, and only when, they appear in all
"should" or "Should"), they have their usual English meanings, and capitals, as shown here.
are not to be interpreted as [RFC2119] key words.
This document uses terminology from [RFC1542], [RFC2131], and This document uses terminology from [RFC1542], [RFC2131], and
[RFC3315]. [RFC3315].
3. Security of Messages Exchanged Between Servers and Relay Agents 3. Security of Messages Exchanged between Servers and Relay Agents
For DHCPv6 [RFC3315], this specification REQUIRES relay and server For DHCPv6 [RFC3315], this specification REQUIRES relay and server
implementations to support IPsec encryption of relay to relay and implementations to support IPsec encryption of relay-to-relay and
relay to server communication as documented below (this replaces the relay-to-server communication as documented below. The remainder of
text in RFC3315 Section 21.1). this section replaces the text in Section 21.1 of [RFC3315] when this
specification is followed.
For DHCPv4 [RFC2131], this specification REQUIRES relay and server For DHCPv4 [RFC2131], this specification REQUIRES relay and server
implementations to support IPsec encryption of relay to server implementations to support IPsec encryption of relay-to-server
communication as documented below. communication as documented below.
This specification RECOMMENDS that operators enable IPsec for this This specification RECOMMENDS that operators enable IPsec for this
communication. communication.
By using IPsec with encryption for this communication, the By using IPsec with encryption for this communication, potentially
potentially sensitive client message and relay included information, sensitive client message and relay included information, such as the
such as the DHCPv4 relay-agent information option (82) [RFC3046], DHCPv4 Relay Agent Information option (82) [RFC3046], vendor-specific
vendor-specific information (for example, [CableLabs-DHCP]), and information (for example, the options defined in [CableLabs-DHCP]),
Access-Network-Identifier Option(s) [RFC7839], are protected from and Access-Network-Identifier option(s) [RFC7839], are protected from
pervasive monitoring and other attacks. pervasive monitoring and other attacks.
Relay agents and servers MUST be able to exchange messages using the Relay agents and servers MUST be able to exchange messages using the
IPsec mechanisms described in [RFC4301] and with the conditions IPsec mechanisms described in [RFC4301] with the conditions below.
below. If a client message is relayed through multiple relay agents If a client message is relayed through multiple relay agents (relay
(relay chain), each of the relay agents MUST have an established chain), each of the relay agents MUST have established independent,
independent, pairwise trust relationships. That is, if messages from pairwise trust relationships. That is, if messages from client C
client C will be relayed by relay agent A to relay agent B and then will be relayed by relay agent A to relay agent B and then to the
to the server, relay agents A and B MUST be configured to use IPsec server, relay agents A and B MUST be configured to use IPsec for the
for the messages they exchange, and relay agent B and the server MUST messages they exchange, and relay agent B and the server MUST be
be configured to use IPsec for the messages they exchange. configured to use IPsec for the messages they exchange.
Relay agents and servers use IPsec with the following conditions: Relay agents and servers use IPsec with the following conditions:
Selectors Relay agents are manually configured with the Selectors Relay agents are manually configured with the
addresses of the relay agent or server to addresses of the relay agent or server to which DHCP
which DHCP messages are to be forwarded. messages are to be forwarded. Each relay agent and
server that will be using IPsec for securing DHCP
Each relay agent and server that will be messages MUST also be configured with a list of the
using IPsec for securing DHCP messages MUST relay agents to which messages will be returned.
also be configured with a list of the relay The selectors for the relay agents and servers will
agents to which messages will be returned. be the pairs of addresses defining relay agents and
The selectors for the relay agents and servers and the direction of DHCP message exchange
servers will be the pairs of addresses on DHCPv4 UDP port 67 or DHCPv6 UDP port 547.
defining relay agents and servers and the
direction of DHCP message exchange on DHCPv4
UDP port 67 or DHCPv6 UDP port 547.
Mode Relay agents and servers MUST use IPsec in Mode Relay agents and servers MUST use IPsec in transport
transport mode and Encapsulating Security mode and use Encapsulating Security Payload (ESP).
Payload (ESP).
Encryption and authentication algorithms Encryption and authentication algorithms
This document REQUIRES combined mode This document REQUIRES combined mode algorithms for
algorithms for ESP authenticated encryption, ESP authenticated encryption, ESP encryption
ESP encryption algorithms, and ESP algorithms, and ESP authentication algorithms as per
authentication algorithms as per Sections Sections 2.1, 2.2, and 2.3 of [RFC7321],
2.1, 2.2, and 2.3 of [RFC7321] respectively. respectively. Encryption is required as relay
Encryption is required as relay agents may agents may forward unencrypted client messages as
forward unencrypted client messages as well well as include additional sensitive information,
as include additional sensitive information, such as vendor-specific information (for example,
such as vendor-specific information (for the options defined in [CableLabs-DHCP]) and the
example, [CableLabs-DHCP]) and [RFC7839]. Access-Network-Identifier Option defined in
[RFC7839].
Key management Because both relay agents and servers tend to Key management Because both relay agents and servers tend to be
be managed by a single organizational entity, managed by a single organizational entity, public
public key schemes MAY be optional. Manually key schemes MAY be optional. Manually configured
configured key management MAY suffice, but key management MAY suffice but does not provide
does not provide defense against replayed defense against replayed messages. Accordingly,
messages. Accordingly, IKEv2 [RFC7296] with Internet Key Exchange Protocol Version 2 (IKEv2)
pre-shared secrets SHOULD be supported. [RFC7296] with pre-shared secrets SHOULD be
IKEv2 with public keys MAY be supported. supported. IKEv2 with public keys MAY be supported.
Additional information on manual vs automated Additional information on manual vs. automated key
key management and when one should be used management and when one should be used over the
over the other can be found in [RFC4107]. other can be found in [RFC4107].
Security policy DHCP messages between relay agents and Security policy DHCP messages between relay agents and servers MUST
servers MUST only be accepted from DHCP peers only be accepted from DHCP peers as identified in
as identified in the local configuration. the local configuration.
Authentication Shared keys, indexed to the source IP address Authentication Shared keys, indexed to the source IP address of the
of the received DHCP message, are adequate in received DHCP message, are adequate in this
this application. application.
Note: As using IPsec with multicast has additional complexities (see Note: As using IPsec with multicast has additional complexities (see
[RFC5374]), relay agents SHOULD be configured to forward DHCP [RFC5374]), relay agents SHOULD be configured to forward DHCP
messages to unicast addresses. messages to unicast addresses.
4. Security Considerations 4. Security Considerations
The security model specified in this document is hop-by-hop. For The security model specified in this document is hop by hop. For
DHCPv6, there could be multiple relay agents between a client and DHCPv6, there could be multiple relay agents between a client and
server and each of these hops needs to be secured. For DHCPv4, there server, and each of these hops needs to be secured. For DHCPv4,
is no support for multiple relays. there is no support for multiple relays.
As this document only mandates securing messages exchanged between As this document only mandates securing messages exchanged between
relay agents and servers, the message exchanges between clients and relay agents and servers, the message exchanges between clients and
the first hop relay agent or server are not secured. Clients may the first-hop relay agent or server are not secured. Clients may
follow the recommendations in [RFC7844] to minimize what information follow the recommendations in [RFC7844] to minimize what information
they expose or make use of [I-D.ietf-dhc-sedhcpv6] to secure they expose or make use of secure DHCPv6 [SEC-DHCPv6] to secure
communication between the client and server. communication between the client and server.
As mentioned in [RFC4552] Section 14, the following are known As mentioned in Section 14 of [RFC4552], the following are known
limitations of the usage of manual keys: limitations of the usage of manual keys:
o As the sequence numbers cannot be negotiated, replay protection o As the sequence numbers cannot be negotiated, replay protection
cannot be provided. This leaves DHCP insecure against all the cannot be provided. This leaves DHCP insecure against all the
attacks that can be performed by replaying DHCP packets. attacks that can be performed by replaying DHCP packets.
o Manual keys are usually long lived (changing them often is a o Manual keys are usually long lived (changing them often is a
tedious task). This gives an attacker enough time to discover the tedious task). This gives an attacker enough time to discover the
keys. keys.
It should be noted if the requirements in this document are followed, It should be noted that if the requirements in this document are
while the DHCP traffic on the wire between relays and servers is followed, while the DHCP traffic on the wire between relays and
encrypted, the unencrypted data may still be available through other servers is encrypted, the unencrypted data may still be available
attacks on the DHCP servers, relays, and related systems. Securing through other attacks on the DHCP servers, relays, and related
these systems and the data in databases and logs also needs to be systems. Securing these systems and the data in databases and logs
considered - on the systems themselves and if transferred over a also needs to be considered on both the systems themselves and when
network (i.e., to network attached storage, for backups, or to transferred over a network (i.e., to network attached storage for
operational support systems). backups or to operational support systems).
Use of IPsec as described herein is also applicable to Lightweight Use of IPsec as described herein is also applicable to Lightweight
DHCPv6 Relay Agents [RFC6221], as they have a link-local address DHCPv6 Relay Agents [RFC6221], as they have a link-local address that
which can be used to secure communication with their next hop can be used to secure communication with their next-hop relay(s).
relay(s).
5. IANA Considerations 5. IANA Considerations
This document has no requests of the fantastic IANA team. This document makes no request of IANA.
6. Acknowledgments
The motivation for this document was several IESG discusses on recent
DHCP relay agent options.
Thanks to Kim Kinnear, Jinmei Tatuya, Francis Dupont, and Tomek
Mrugalski for reviewing drafts and helping to improve the document.
And, thanks to the authors of [RFC3315] for the original Section 21.1
text.
7. References 6. References
7.1. Normative References 6.1. Normative References
[RFC1542] Wimer, W., "Clarifications and Extensions for the [RFC1542] Wimer, W., "Clarifications and Extensions for the
Bootstrap Protocol", RFC 1542, DOI 10.17487/RFC1542, Bootstrap Protocol", RFC 1542, DOI 10.17487/RFC1542,
October 1993, <http://www.rfc-editor.org/info/rfc1542>. October 1993, <http://www.rfc-editor.org/info/rfc1542>.
[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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 6, line 47 skipping to change at page 6, line 37
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <http://www.rfc-editor.org/info/rfc4301>. December 2005, <http://www.rfc-editor.org/info/rfc4301>.
[RFC7321] McGrew, D. and P. Hoffman, "Cryptographic Algorithm [RFC7321] McGrew, D. and P. Hoffman, "Cryptographic Algorithm
Implementation Requirements and Usage Guidance for Implementation Requirements and Usage Guidance for
Encapsulating Security Payload (ESP) and Authentication Encapsulating Security Payload (ESP) and Authentication
Header (AH)", RFC 7321, DOI 10.17487/RFC7321, August 2014, Header (AH)", RFC 7321, DOI 10.17487/RFC7321, August 2014,
<http://www.rfc-editor.org/info/rfc7321>. <http://www.rfc-editor.org/info/rfc7321>.
7.2. Informative References [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
[CableLabs-DHCP] 6.2. Informative References
"CableLabs' DHCP Options Registry",
<http://www.cablelabs.com/specification/
cablelabs-dhcp-options-registry-2/>.
[I-D.ietf-dhc-sedhcpv6] [CableLabs-DHCP]
Li, L., Jiang, S., Cui, Y., Jinmei, T., Lemon, T., and D. CableLabs, "CableLabs' DHCP Options Registry",
Zhang, "Secure DHCPv6", draft-ietf-dhc-sedhcpv6-21 (work <https://apps.cablelabs.com/specification/CL-SP-CANN-DHCP-
in progress), February 2017. Reg>.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", [RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, DOI 10.17487/RFC3046, January 2001, RFC 3046, DOI 10.17487/RFC3046, January 2001,
<http://www.rfc-editor.org/info/rfc3046>. <http://www.rfc-editor.org/info/rfc3046>.
[RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic [RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic
Key Management", BCP 107, RFC 4107, DOI 10.17487/RFC4107, Key Management", BCP 107, RFC 4107, DOI 10.17487/RFC4107,
June 2005, <http://www.rfc-editor.org/info/rfc4107>. June 2005, <http://www.rfc-editor.org/info/rfc4107>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality [RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
skipping to change at page 8, line 5 skipping to change at page 7, line 42
[RFC7839] Bhandari, S., Gundavelli, S., Grayson, M., Volz, B., and [RFC7839] Bhandari, S., Gundavelli, S., Grayson, M., Volz, B., and
J. Korhonen, "Access-Network-Identifier Option in DHCP", J. Korhonen, "Access-Network-Identifier Option in DHCP",
RFC 7839, DOI 10.17487/RFC7839, June 2016, RFC 7839, DOI 10.17487/RFC7839, June 2016,
<http://www.rfc-editor.org/info/rfc7839>. <http://www.rfc-editor.org/info/rfc7839>.
[RFC7844] Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity [RFC7844] Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
Profiles for DHCP Clients", RFC 7844, Profiles for DHCP Clients", RFC 7844,
DOI 10.17487/RFC7844, May 2016, DOI 10.17487/RFC7844, May 2016,
<http://www.rfc-editor.org/info/rfc7844>. <http://www.rfc-editor.org/info/rfc7844>.
[SEC-DHCPv6]
Li, L., Jiang, S., Cui, Y., Jinmei, T., Lemon, T., and D.
Zhang, "Secure DHCPv6", Work in Progress,
draft-ietf-dhc-sedhcpv6-21, February 2017.
Acknowledgments
The motivation for this document was several IESG DISCUSSes on recent
DHCP relay agent options.
Thanks to Kim Kinnear, Jinmei Tatuya, Francis Dupont, and Tomek
Mrugalski for reviewing and helping to improve the document. Thanks
to the authors of [RFC3315] for the original Section 21.1 text.
Authors' Addresses Authors' Addresses
Bernie Volz Bernie Volz
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Ave 1414 Massachusetts Ave
Boxborough, MA 01719 Boxborough, MA 01719
USA United States of America
Email: volz@cisco.com Email: volz@cisco.com
Yogendra Pal Yogendra Pal
Cisco Systems, Inc. Cisco Systems
Cessna Business Park, Cessna Business Park
Varthur Hobli, Outer Ring Road, Varthur Hobli, Outer Ring Road
Bangalore, Karnataka 560103 Bangalore, Karnataka 560103
India India
Email: yogpal@cisco.com Email: yogpal@cisco.com
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