draft-ietf-dhc-relay-server-security-02.txt   draft-ietf-dhc-relay-server-security-03.txt 
Network Working Group B. Volz Network Working Group B. Volz
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Standards Track Y. Pal Intended status: Standards Track Y. Pal
Expires: June 18, 2017 Cisco Systems, Inc. Expires: August 11, 2017 Cisco Systems, Inc.
December 15, 2016 February 7, 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-02.txt draft-ietf-dhc-relay-server-security-03.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. And, 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
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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 June 18, 2017. This Internet-Draft will expire on August 11, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 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
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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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 . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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 [RFC1542] has no guidance for how to secure messages exchanged
between servers and relay agents. The Dynamic Host Configuration between servers and relay agents. The Dynamic Host Configuration
Protocol for IPv6 (DHCPv6) [RFC3315] states that IPsec should be used Protocol for IPv6 (DHCPv6) [RFC3315] states that IPsec should be used
to secure messages exchanged between servers and relay agents, but to secure messages exchanged between servers and relay agents, but
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document are to be interpreted as described in [RFC2119] when they document are to be interpreted as described in [RFC2119] when they
appear in ALL CAPS. When these words are not in ALL CAPS (such as appear in ALL CAPS. When these words are not in ALL CAPS (such as
"should" or "Should"), they have their usual English meanings, and "should" or "Should"), they have their usual English meanings, and
are not to be interpreted as [RFC2119] key words. 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
The following text replaces the text in RFC3315 section 21.1 and also For DHCPv6 [RFC3315], this specification REQUIRES IPsec encryption of
applies to DHCPv4 (RFC1542) for relay to server communication. This relay to relay and relay to server communication and replaces the
revised text REQUIRES IPsec encryption of relay to relay and relay to text in RFC3315 Section 21.1.
server communications as relay agents may forward unencrypted client
messages as well as include additional sensitive information, such as For DHCPv4 [RFC2131], this specification REQUIRES IPsec encryption of
vendor-specific information (for example, [CableLabs-DHCP]) and relay to server communication.
[RFC7839]. By using IPsec with encryption, the potentially sensitive
communication between relays and servers is protected from pervasive By using IPsec with encryption for this communication, the
monitoring and other attacks. potentially sensitive client message and relay included information,
such as the DHCPv4 relay-agent information option (82) [RFC3046],
vendor-specific information (for example, [CableLabs-DHCP]), and
Access-Network-Identifier Option(s) [RFC7839], are protected from
pervasive monitoring and other attacks.
Relay agents and servers MUST exchange messages securely using the Relay agents and servers MUST exchange messages securely using the
IPsec mechanisms described in [RFC4301]. If a client message is IPsec mechanisms described in [RFC4301]. If a client message is
relayed through multiple relay agents, each of the relay agents MUST relayed through multiple relay agents, each of the relay agents MUST
have an established independent, pairwise trust relationships. That have an established independent, pairwise trust relationships. That
is, if messages from client C will be relayed by relay agent A to is, if messages from client C will be relayed by relay agent A to
relay agent B and then to the server, relay agents A and B MUST be relay agent B and then to the server, relay agents A and B MUST be
configured to use IPsec for the messages they exchange, and relay configured to use IPsec for the messages they exchange, and relay
agent B and the server MUST be configured to use IPsec for the agent B and the server MUST be configured to use IPsec for the
messages they exchange. messages they exchange.
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UDP port 67 or DHCPv6 UDP port 547. 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 mode and Encapsulating Security transport mode and 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 ESP authenticated encryption, algorithms for ESP authenticated encryption,
ESP encryption algorithms, and ESP ESP encryption algorithms, and ESP
authentication algorithms as per section 2.1, authentication algorithms as per Sections
2.2, and 2.3 of [RFC7321] respectively. 2.1, 2.2, and 2.3 of [RFC7321] respectively.
Encryption is required as relay agents may Encryption is required as relay agents may
forward unencrypted client messages as well forward unencrypted client messages as well
as include additional sensitive information, as include additional sensitive information,
such as vendor-specific information (for such as vendor-specific information (for
example, [CableLabs-DHCP]) and [RFC7839]. example, [CableLabs-DHCP]) and [RFC7839].
Key management Because both relay agents and servers tend to Key management Because both relay agents and servers tend to
be managed by a single organizational entity, be managed by a single organizational entity,
public key schemes MAY be optional. Manually public key schemes MAY be optional. Manually
configured key management MAY suffice, but configured key management MAY suffice, but
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Security policy DHCP messages between relay agents and Security policy DHCP messages between relay agents and
servers MUST only be accepted from DHCP peers servers MUST only be accepted from DHCP peers
as identified in the local configuration. as identified in the local configuration.
Authentication Shared keys, indexed to the source IP address Authentication Shared keys, indexed to the source IP address
of the received DHCP message, are adequate in of the received DHCP message, are adequate in
this application. this application.
4. Security Considerations 4. Security Considerations
The security model specified in this document is hop-by-hop. For
DHCPv6, there could be multiple relay agents between a client and
server and each of these hops needs to be secured. For DHCPv4, 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 [I-D.ietf-dhc-sedhcpv6] 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 [RFC4552] Section 14, 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.
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7.2. Informative References 7.2. Informative References
[CableLabs-DHCP] [CableLabs-DHCP]
"CableLabs' DHCP Options Registry", "CableLabs' DHCP Options Registry",
<http://www.cablelabs.com/specification/ <http://www.cablelabs.com/specification/
cablelabs-dhcp-options-registry-2/>. cablelabs-dhcp-options-registry-2/>.
[I-D.ietf-dhc-sedhcpv6] [I-D.ietf-dhc-sedhcpv6]
Jiang, S., Li, L., Cui, Y., Jinmei, T., Lemon, T., and D. Jiang, S., Li, L., Cui, Y., Jinmei, T., Lemon, T., and D.
Zhang, "Secure DHCPv6", draft-ietf-dhc-sedhcpv6-18 (work Zhang, "Secure DHCPv6", draft-ietf-dhc-sedhcpv6-20 (work
in progress), December 2016. in progress), January 2017.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, DOI 10.17487/RFC3046, January 2001,
<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
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006, for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<http://www.rfc-editor.org/info/rfc4552>. <http://www.rfc-editor.org/info/rfc4552>.
[RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A. [RFC6221] Miles, D., Ed., Ooghe, S., Dec, W., Krishnan, S., and A.
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