draft-ietf-babel-dtls-08.txt   draft-ietf-babel-dtls-09.txt 
Network Working Group A. Decimo Network Working Group A. Decimo
Internet-Draft IRIF, University of Paris-Diderot Internet-Draft IRIF, University of Paris-Diderot
Intended status: Standards Track D. Schinazi Intended status: Standards Track D. Schinazi
Expires: February 10, 2020 Google LLC Expires: February 14, 2020 Google LLC
J. Chroboczek J. Chroboczek
IRIF, University of Paris-Diderot IRIF, University of Paris-Diderot
August 9, 2019 August 13, 2019
Babel Routing Protocol over Datagram Transport Layer Security Babel Routing Protocol over Datagram Transport Layer Security
draft-ietf-babel-dtls-08 draft-ietf-babel-dtls-09
Abstract Abstract
The Babel Routing Protocol does not contain any means to authenticate The Babel Routing Protocol does not contain any means to authenticate
neighbours or provide integrity or confidentiality for messages sent neighbours or provide integrity or confidentiality for messages sent
between them. This document specifies a mechanism to ensure these between them. This document specifies a mechanism to ensure these
properties, using Datagram Transport Layer Security (DTLS). properties, using Datagram Transport Layer Security (DTLS).
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
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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 February 10, 2020. This Internet-Draft will expire on February 14, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
(https://trustee.ietf.org/license-info) in effect on the date of (https://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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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Specification of Requirements . . . . . . . . . . . . . . 2 1.1. Specification of Requirements . . . . . . . . . . . . . . 2
1.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 3
2. Operation of the Protocol . . . . . . . . . . . . . . . . . . 3 2. Operation of the Protocol . . . . . . . . . . . . . . . . . . 3
2.1. DTLS Connection Initiation . . . . . . . . . . . . . . . 3 2.1. DTLS Connection Initiation . . . . . . . . . . . . . . . 3
2.2. Protocol Encoding . . . . . . . . . . . . . . . . . . . . 4 2.2. Protocol Encoding . . . . . . . . . . . . . . . . . . . . 4
2.3. Transmission . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Transmission . . . . . . . . . . . . . . . . . . . . . . 4
2.4. Reception . . . . . . . . . . . . . . . . . . . . . . . . 5 2.4. Reception . . . . . . . . . . . . . . . . . . . . . . . . 5
2.5. Neighbour table entry . . . . . . . . . . . . . . . . . . 5 2.5. Neighbour table entry . . . . . . . . . . . . . . . . . . 5
2.6. Simultaneous operation of both Babel over DTLS and 2.6. Simultaneous operation of both Babel over DTLS and
unprotected Babel on a Node . . . . . . . . . . . . . . . 5 unprotected Babel on a Node . . . . . . . . . . . . . . . 6
2.7. Simultaneous operation of both Babel over DTLS and 2.7. Simultaneous operation of both Babel over DTLS and
unprotected Babel on a Network . . . . . . . . . . . . . 6 unprotected Babel on a Network . . . . . . . . . . . . . 6
3. Interface Maximum Transmission Unit Issues . . . . . . . . . 6 3. Interface Maximum Transmission Unit Issues . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.1. Normative References . . . . . . . . . . . . . . . . . . 8 6.1. Normative References . . . . . . . . . . . . . . . . . . 8
6.2. Informative References . . . . . . . . . . . . . . . . . 8 6.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Performance Considerations . . . . . . . . . . . . . 9 Appendix A. Performance Considerations . . . . . . . . . . . . . 9
Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 9 Appendix B. Acknowledgments . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
The Babel Routing Protocol [RFC6126bis] does not contain any means to The Babel Routing Protocol [RFC6126bis] does not contain any means to
authenticate neighbours or protect messages sent between them. authenticate neighbours or protect messages sent between them.
Because of this, an attacker is able to send maliciously crafted Because of this, an attacker is able to send maliciously crafted
Babel messages which could lead a network to route traffic to an Babel messages which could lead a network to route traffic to an
attacker or to an under-resourced target causing denial of service. attacker or to an under-resourced target causing denial of service.
This document specifies a mechanism to prevent such attacks, using This document specifies a mechanism to prevent such attacks, using
Datagram Transport Layer Security (DTLS) [RFC6347]. Datagram Transport Layer Security (DTLS) [RFC6347].
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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 BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
1.2. Applicability 1.2. Applicability
The protocol described in this document protects Babel packets with The protocol described in this document protects Babel packets with
DTLS. As such, it inherits the features offered by DTLS, notably DTLS. As such, it inherits the features offered by DTLS, notably
authentication, integrity, replay protection, confidentiality and authentication, integrity, optional replay protection,
asymmetric keying. It is therefore expected to be applicable in a confidentiality and asymmetric keying. It is therefore expected to
wide range of environments. be applicable in a wide range of environments.
There exists another mechanism for securing Babel, namely Babel HMAC There exists another mechanism for securing Babel, namely Babel HMAC
authentication [BABEL-HMAC]. HMAC only offers basic features, namely authentication [BABEL-HMAC]. HMAC only offers basic features, namely
authentication, integrity and replay protection with a small number authentication, integrity and replay protection with a small number
of symmetric keys. A comparison of Babel security mechanisms and of symmetric keys. A comparison of Babel security mechanisms and
their applicability can be found in [RFC6126bis]. their applicability can be found in [RFC6126bis].
Note that Babel over DTLS provides a single authentication domain, Note that Babel over DTLS provides a single authentication domain,
meaning that all nodes that have the right credentials can convey any meaning that all nodes that have the right credentials can convey any
and all routing information. and all routing information.
DTLS supports several mechanisms by which nodes can identify
themselves and prove possession of secrets tied to these identities.
This document does not prescribe which of these mechanisms to use;
details of identity management are left to deployment profiles of
Babel over DTLS.
2. Operation of the Protocol 2. Operation of the Protocol
Babel over DTLS requires some changes to how Babel operates. First, Babel over DTLS requires some changes to how Babel operates. First,
DTLS is a client-server protocol, while Babel is a peer-to-peer DTLS is a client-server protocol, while Babel is a peer-to-peer
protocol. Second, DTLS can only protect unicast communication, while protocol. Second, DTLS can only protect unicast communication, while
Babel packets can be sent over to both unicast and multicast Babel packets can be sent over to both unicast and multicast
destinations. destinations.
2.1. DTLS Connection Initiation 2.1. DTLS Connection Initiation
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packets, DTLS is not able to detect when an active on-path attacker packets, DTLS is not able to detect when an active on-path attacker
intercepts valid packets and resends them at a later time. This intercepts valid packets and resends them at a later time. This
attack could be used to make a node believe it has bidirectional attack could be used to make a node believe it has bidirectional
reachability to a neighbour even though that neighbour has reachability to a neighbour even though that neighbour has
disconnected from the network. To prevent this attack, nodes MUST disconnected from the network. To prevent this attack, nodes MUST
discard the DTLS state associated with a neighbour after a finite discard the DTLS state associated with a neighbour after a finite
time of not receiving valid DTLS packets. This can be implemented time of not receiving valid DTLS packets. This can be implemented
by, for example, discarding a neighbour's DTLS state when its by, for example, discarding a neighbour's DTLS state when its
associated IHU timer fires. Note that relying solely on the receipt associated IHU timer fires. Note that relying solely on the receipt
of Hellos is not sufficient as multicast Hellos are sent unprotected. of Hellos is not sufficient as multicast Hellos are sent unprotected.
Additionally, an attacker could save some packets and replay them
later in hopes of propagating stale routing information at a later
time. To mitigate this, nodes MUST discard received packets that
have been reordered by more than one IHU interval.
2.6. Simultaneous operation of both Babel over DTLS and unprotected 2.6. Simultaneous operation of both Babel over DTLS and unprotected
Babel on a Node Babel on a Node
Implementations MAY implement both Babel over DTLS and unprotected Implementations MAY implement both Babel over DTLS and unprotected
Babel. Additionally, a node MAY simultaneously run both Babel over Babel. Additionally, a node MAY simultaneously run both Babel over
DTLS and unprotected Babel. However, a node running both MUST ensure DTLS and unprotected Babel. However, a node running both MUST ensure
that it runs them on separate interfaces, as the security properties that it runs them on separate interfaces, as the security properties
of Babel over DTLS rely on not accepting unprotected Babel packets of Babel over DTLS rely on not accepting unprotected Babel packets
(other than multicast Hellos). A node MAY allow configuration (other than multicast Hellos). A node MAY allow configuration
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(at least UDP and IP) or 512 octets, whichever is larger, but not (at least UDP and IP) or 512 octets, whichever is larger, but not
exceeding 2^16 - 1 adjusted for lower-layer headers. Every Babel exceeding 2^16 - 1 adjusted for lower-layer headers. Every Babel
speaker MUST be able to receive packets that are as large as any speaker MUST be able to receive packets that are as large as any
attached interface's MTU adjusted for UDP and IP headers or 512 attached interface's MTU adjusted for UDP and IP headers or 512
octets, whichever is larger. Note that this requirement on reception octets, whichever is larger. Note that this requirement on reception
does not take into account the overhead of DTLS because the peer may does not take into account the overhead of DTLS because the peer may
not have the ability to compute the overhead of DTLS and the packet not have the ability to compute the overhead of DTLS and the packet
may be fragmented by lower layers. may be fragmented by lower layers.
Note that distinct DTLS connections can use different ciphers, which Note that distinct DTLS connections can use different ciphers, which
can have different amounts of overhead per packet. Therefore, the can have different amounts of per-packet overhead. Therefore, the
MTU to one neighbour can be different from the MTU to another MTU to one neighbour can be different from the MTU to another
neighbour on the same link. neighbour on the same link.
4. IANA Considerations 4. IANA Considerations
If this document is approved, IANA is requested to register a UDP If this document is approved, IANA is requested to register a UDP
port number, called "babel-dtls", for use by Babel over DTLS. port number, called "babel-dtls", for use by Babel over DTLS.
Details of the request to IANA are as follows: Details of the request to IANA are as follows:
o Assignee: IESG, iesg@ietf.org o Assignee: IESG, iesg@ietf.org
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(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/bcp195>. 2015, <https://www.rfc-editor.org/info/bcp195>.
[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>.
[RFC6126bis] [RFC6126bis]
Chroboczek, J. and D. Schinazi, "The Babel Routing Chroboczek, J. and D. Schinazi, "The Babel Routing
Protocol", Internet Draft draft-ietf-babel-rfc6126bis-12, Protocol", Internet Draft draft-ietf-babel-rfc6126bis-13,
August 2019. August 2019.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>. January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[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>.
6.2. Informative References 6.2. Informative References
[BABEL-HMAC] [BABEL-HMAC]
Do, C., Kolodziejak, W., and J. Chroboczek, "Babel Do, C., Kolodziejak, W., and J. Chroboczek, "Babel
Cryptographic Authentication", Internet Draft draft-ietf- Cryptographic Authentication", Internet Draft draft-ietf-
babel-hmac-08, June 2019. babel-hmac-09, August 2019.
[DTLS-CID] [DTLS-CID]
Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom, Rescorla, E., Tschofenig, H., Fossati, T., and T. Gondrom,
"Connection Identifiers for DTLS 1.2", Internet Draft "Connection Identifiers for DTLS 1.2", Internet Draft
draft-ietf-tls-dtls-connection-id-06, July 2019. draft-ietf-tls-dtls-connection-id-06, July 2019.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J., [RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
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