draft-ietf-babel-dtls-09.txt   draft-ietf-babel-dtls-10.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 14, 2020 Google LLC Expires: January 1, 2021 Google LLC
J. Chroboczek J. Chroboczek
IRIF, University of Paris-Diderot IRIF, University of Paris-Diderot
August 13, 2019 June 30, 2020
Babel Routing Protocol over Datagram Transport Layer Security Babel Routing Protocol over Datagram Transport Layer Security
draft-ietf-babel-dtls-09 draft-ietf-babel-dtls-10
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 14, 2020. This Internet-Draft will expire on January 1, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 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
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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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 . . . . . . . . . . . . . . . 6 unprotected Babel on a Node . . . . . . . . . . . . . . . 5
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 . . . . . . . . . . . . . . . . . . . . . 6
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 . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
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themselves and prove possession of secrets tied to these identities. themselves and prove possession of secrets tied to these identities.
This document does not prescribe which of these mechanisms to use; This document does not prescribe which of these mechanisms to use;
details of identity management are left to deployment profiles of details of identity management are left to deployment profiles of
Babel over DTLS. 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 to both unicast and multicast destinations.
destinations.
2.1. DTLS Connection Initiation 2.1. DTLS Connection Initiation
Babel over DTLS operates on a different port than unencrypted Babel. Babel over DTLS operates on a different port than unencrypted Babel.
All Babel over DTLS nodes MUST act as DTLS servers on a given UDP All Babel over DTLS nodes MUST act as DTLS servers on a given UDP
port, and MUST listen for unencrypted Babel traffic on another UDP port, and MUST listen for unencrypted Babel traffic on another UDP
port, which MUST be distinct from the first one. The default port port, which MUST be distinct from the first one. The default port
for Babel over DTLS is registered with IANA as the "babel-dtls" port for Babel over DTLS is registered with IANA as the "babel-dtls" port
(UDP port TBD, see Section 4), and the port exchanging unencrypted (UDP port TBD, see Section 4), and the port exchanging unencrypted
Babel traffic is registered as the "babel" port (UDP port 6696, see Babel traffic is registered as the "babel" port (UDP port 6696, see
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2.5. Neighbour table entry 2.5. Neighbour table entry
It is RECOMMENDED for nodes to associate the state of their DTLS It is RECOMMENDED for nodes to associate the state of their DTLS
connection with their neighbour table. When a neighbour entry is connection with their neighbour table. When a neighbour entry is
flushed from the neighbour table (Appendix A of [RFC6126bis]), its flushed from the neighbour table (Appendix A of [RFC6126bis]), its
associated DTLS state SHOULD be discarded. The node SHOULD send a associated DTLS state SHOULD be discarded. The node SHOULD send a
DTLS close_notify alert to the neighbour if it believes the link is DTLS close_notify alert to the neighbour if it believes the link is
still viable. still viable.
While DTLS provides protection against an attacker that replays valid
packets, DTLS is not able to detect when an active on-path attacker
intercepts valid packets and resends them at a later time. This
attack could be used to make a node believe it has bidirectional
reachability to a neighbour even though that neighbour has
disconnected from the network. To prevent this attack, nodes MUST
discard the DTLS state associated with a neighbour after a finite
time of not receiving valid DTLS packets. This can be implemented
by, for example, discarding a neighbour's DTLS state when its
associated IHU timer fires. Note that relying solely on the receipt
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). An implementation MAY offer
options to allow unprotected Babel on some interfaces but not others; configuration options to allow unprotected Babel on some interfaces
this effectively gives nodes on that interface the same access as but not others; this effectively gives nodes on that interface the
authenticated nodes, and SHOULD NOT be done unless that interface has same access as authenticated nodes, and SHOULD NOT be done unless
a mechanism to authenticate nodes at a lower layer (e.g., IPsec). that interface has a mechanism to authenticate nodes at a lower layer
(e.g., IPsec).
2.7. Simultaneous operation of both Babel over DTLS and unprotected 2.7. Simultaneous operation of both Babel over DTLS and unprotected
Babel on a Network Babel on a Network
If Babel over DTLS and unprotected Babel are both operated on the If Babel over DTLS and unprotected Babel are both operated on the
same network, the Babel over DTLS implementation will receive same network, the Babel over DTLS implementation will receive
unprotected multicast Hellos and attempt to initiate a DTLS unprotected multicast Hellos and attempt to initiate a DTLS
connection. These connection attempts can be sent to nodes that only connection. These connection attempts can be sent to nodes that only
run unprotected Babel, who will not respond. Babel over DTLS run unprotected Babel, who will not respond. Babel over DTLS
implementations SHOULD therefore rate-limit their DTLS connection implementations SHOULD therefore rate-limit their DTLS connection
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of this document. of this document.
Babel over DTLS allows sending multicast Hellos unprotected; Babel over DTLS allows sending multicast Hellos unprotected;
attackers can therefore tamper with them. For example, an attacker attackers can therefore tamper with them. For example, an attacker
could send erroneous values for the Seqno and Interval fields, could send erroneous values for the Seqno and Interval fields,
causing bidirectional reachability detection to fail. While causing bidirectional reachability detection to fail. While
implementations MAY use multicast Hellos for link quality estimation, implementations MAY use multicast Hellos for link quality estimation,
they SHOULD also emit protected unicast Hellos to prevent this class they SHOULD also emit protected unicast Hellos to prevent this class
of denial-of-service attack. of denial-of-service attack.
While DTLS provides protection against an attacker that replays valid
packets, DTLS is not able to detect when an active on-path attacker
intercepts valid packets and resends them at a later time. This
attack could be used to make a node believe it has bidirectional
reachability to a neighbour even though that neighbour has
disconnected from the network. To prevent this attack, nodes MUST
discard the DTLS state associated with a neighbour after a finite
time of not receiving valid DTLS packets. This can be implemented
by, for example, discarding a neighbour's DTLS state when its
associated IHU timer fires. Note that relying solely on the receipt
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. This can be mitigated by discarding received packets that have
been reordered by more than two IHU intervals.
6. References 6. References
6.1. Normative References 6.1. Normative References
[BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre, [BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(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-13, Protocol", Internet Draft draft-ietf-babel-rfc6126bis-17,
August 2019. February 2020.
[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-09, August 2019. babel-hmac-10, 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-07, October 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,
June 2014, <https://www.rfc-editor.org/info/rfc7250>. June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport [RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport
Layer Security (TLS) False Start", RFC 7918, Layer Security (TLS) False Start", RFC 7918,
DOI 10.17487/RFC7918, August 2016, DOI 10.17487/RFC7918, August 2016,
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