anima Working Group M. Richardson
Internet-Draft Sandelman Software Works
Intended status: Standards Track P. van der Stok
Expires: April 2, 2019 vanderstok consultancy
P. Kampanakis
Cisco Systems
September 29, 2018
Constrained Join Proxy for Bootstrapping Protocols
draft-vanderstok-constrained-anima-dtls-join-proxy-00
Abstract
This document defines a protocol to securely assign a pledge to an
owner, using an intermediary node between pledge and owner. This
intermediary node is known as a "constrained-join-proxy".
This document extends the work of
[I-D.ietf-anima-bootstrapping-keyinfra] by replacing the Circuit-
proxy by a stateless constrained join-proxy, that uses IP
encapsulation.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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 https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 2, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
4. Join Proxy functionality . . . . . . . . . . . . . . . . . . 3
5. Join Proxy specification . . . . . . . . . . . . . . . . . . 4
6. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 7
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. Normative References . . . . . . . . . . . . . . . . . . 7
11.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Enrolment of new nodes into constrained networks with constrained
nodes present is described in [I-D.ietf-anima-bootstrapping-keyinfra]
and makes use of Enrolment over Secure Transport (EST) [RFC7030].
The specified solutions use https and may be too large in terms of
code space or bandwidth required. Constrained devices in constrained
networks [RFC7228] typically implement the IPv6 over Low-Power
Wireless personal Area Networks (6LoWPAN) [RFC4944] and Constrained
Application Protocol (CoAP) [RFC7252].
CoAP has chosen Datagram Transport Layer Security (DTLS) [RFC6347] as
the preferred security protocol for authenticity and confidentiality
of the messages. A constrained version of EST, using Coap and DTLS,
is described in [I-D.ietf-ace-coap-est].
DTLS is a client-server protocol relying on the underlying IP layer
to perform the routing between the DTLS Client and the DTLS Server.
However, the new "joining" device will not be IP routable until it is
authenticated to the network. A new "joining" device can only
initially use a link-local IPv6 address to communicate with a
neighbour node using neighbour discovery [RFC6775] until it receives
the necessary network configuration parameters. However, before the
device can receive these configuration parameters, it needs to
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authenticate itself to the network to which it connects. In
[I-D.ietf-anima-bootstrapping-keyinfra] Enrolment over Secure
Transport (EST) [RFC7030] is used to authenticate the joining device.
However, IPv6 routing is necessary to establish a connection between
joining device and the EST server.
This document specifies a Join-proxy and protocol to act as
intermediary between joining device and EST server to establish a
connection between joining device and EST server.
This document is very much inspired by text published earlier in
[I-D.kumar-dice-dtls-relay].
2. Terminology
The following terms are defined in [RFC8366], and are used
identically as in that document: artifact, imprint, domain, Join
Registrar/Coordinator (JRC), Manufacturer Authorized Signing
Authority (MASA), pledge, Trust of First Use (TOFU), and Voucher.
3. Requirements Language
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119
[RFC2119] and indicate requirement levels for compliant STuPiD
implementations.
4. Join Proxy functionality
As depicted in the Figure 1, the joining Device, or pledge (P), is
more than one hop away from the EST server (E) and not yet
authenticated into the network. At this stage, it can only
communicate one-hop to its nearest neighbour, the Join proxy (J)
using their link-local IPv6 addresses. However, the Device needs to
communicate with end-to-end security with a Registrar hosting the EST
server (E) to authenticate and get the relevant system/network
parameters. If the Pledge (P) initiates a DTLS connection to the EST
server whose IP address has been pre-configured, then the packets are
dropped at the Join Proxy (J) since the Pledge (P) is not yet
admitted to the network or there is no IP routability to Pledge (P)
for any returned messages.
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++++
|E |---- +--+ +--+
| | \ |J |........|P |
++++ \-----| | | |
EST server +--+ +--+
REgistrar Join Proxy PLedge
"Joining" Device
Figure 1: multi-hop enrolment.
Furthermore, the Pledge (P) may wish to establish a secure connection
to the EST server (E) in the network assuming appropriate credentials
are exchanged out-of-band, e.g. a hash of the Pledge (P)'s raw public
key could be provided to the EST server (E). However, the Pledge (P)
is unaware of the IP address of the EST-server (E) to initiate a DTLS
connection and perform authentication with.
An DTLS connection is required between Pledge and EST server. To
overcome the problems with non-routability of DTLS packets and/ or
discovery of the destination address of the EST Server to contact,
the Join Proxy is introduced. This Join-Proxy functionality is
configured into all authenticated devices in the network which may
act as the Join Proxy (J) for newly joining nodes. The Join Proxy
allows for routing of the packets from the Pledge (P) using IP
routing to the intended EST Server.
5. Join Proxy specification
In this section, the constrained Join Proxy functionality is
specified using DTLS and coaps. When a joining device as a client
attempts a DTLS connection to the EST server, it uses its link- local
IP address as its IP source address. This message is transmitted
one-hop to a neighbour node. Under normal circumstances, this
message would be dropped at the neighbour node since the joining
device is not yet IP routable or it is not yet authenticated to send
messages through the network. However, if the neighbour device has
the Join Proxy functionality enabled, it routes the DTLS message to a
specific EST Server. Additional security mechanisms need to exist to
prevent this routing functionality being used by rogue nodes to
bypass any network authentication procedures.
The Join-proxy is stateless to minimize the requirements on the
constrained Join-proxy device.
If an untrusted DTLS Client that can only use link-local addressing
wants to contact a trusted end-point EST Server, it sends the DTLS
message to the Join Proxy. The Join Proxy encapsulates this message
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into a new type of message called Join ProxY (JPY) message. The JPY
message consists of two parts:
o Header (H) field: consisting of the source link-local address and
port of the DTLS Client device, and
o Contents (C) field: containing the original DTLS message.
On receiving the JPY message, the EST Server decapsulates it to
retrieve the two parts. It uses the Header field information to
transiently store the DTLS Client's address and port. The EST Server
then performs the normal DTLS operations on the DTLS message from the
Contents field. However, when the EST Server replies, it also
encapsulates its DTLS message in a JPY message back to the Join
Proxy. The Header contains the original source link-local address
and port of the DTLS Client from the transient state stored earlier
(which can now be discarded) and the Contents field contains the DTLS
message.
On receiving the JPY message, the Join Proxy decapsulates it to
retrieve the two parts. It uses the Header field to route the DTLS
message retrieved from the Contents field to the joining node.
The Figure 2 depicts the message flow diagram when the EST Server
end-point address is known only to the Join Proxy:
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+--------------+------------+---------------+-----------------------+
| EST Client | Join Proxy | EST server | Message |
| (P) | (J) | (E) |Src_IP:port|Dst_IP:port|
+--------------+------------+---------------+-----------+-----------+
| --ClientHello--> | IP_C:p_C |IP_Ra:5684 |
| --JPY[H(IP_C:p_C),--> | IP_Rb:p_Rb|IP_S:5684 |
| C(ClientHello)] | | |
| <--JPY[H(IP_C:p_C),-- | IP_S:5684 |IP_Rb:p_Rb |
| C(ServerHello)] | | |
| <--ServerHello-- | IP_Ra:5684|IP_C:p_C |
| : | | |
| : | : | : |
| | : | : |
| --Finished--> | IP_C:p_C |IP_Ra:5684 |
| --JPY[H(IP_C:p_C),--> | IP_Rb:p_Rb|IP_S:5684 |
| C(Finished)] | | |
| <--JPY[H(IP_C:p_C),-- | IP_S:5684 |IP_Rb:p_Rb |
| C(Finished)] | | |
| <--Finished-- | IP_Ra:5684|IP_C:p_C |
| : | : | : |
+-------------------------------------------+-----------+-----------+
IP_C:p_C = Link-local IP address and port of DTLS Client
IP_S:5684 = IP address and coaps port of DTLS Server
IP_Ra:5684 = Link-local IP address and coaps port of DTLS Relay
IP_Rb:p_Rb = IP address(can be same as IP_Ra) and port of DTLS Relay
JPY[H(),C()] = Join Proxy message with header H and content C
Figure 2: constrained joining message flow.
6. Protocol
The JPY message is constructed as a single untagged [RFC7049] CBOR
map. The contents of the map include:
1: the pledge IPv6 Link Local address as a 16-byte binary value.
2: the pledge's UDP port number, if different from 5684, as a CBOR
integer.
3: the proxy's ifindex or other identifier for the physical port on
which the pledge is connected.
4: the contents of the UDP (DTLS) message received from the pledge.
(INSERT CDDL notation)
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7. Security Considerations
It should be noted here that the contents of the CBOR map are not
protected, but that the communication is between the Proxy and a
known registrar (a connected UDP socket), and that messages from
other origins are ignored.
8. IANA Considerations
This document needs to create a registry for key indexes in the CBOR
map. It should be given a name, and the amending formula should be
IETF Specification.
9. Acknowledgements
Much of this text is inspired by [I-D.kumar-dice-dtls-relay].
10. Changelog
empty
11. References
11.1. Normative References
[I-D.ietf-ace-cbor-web-token]
Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", draft-ietf-ace-cbor-web-token-15
(work in progress), March 2018.
[I-D.ietf-ace-coap-est]
Stok, P., Kampanakis, P., Kumar, S., Richardson, M.,
Furuhed, M., and S. Raza, "EST over secure CoAP (EST-
coaps)", draft-ietf-ace-coap-est-05 (work in progress),
July 2018.
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
S., and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-16 (work in progress), June 2018.
[I-D.ietf-core-object-security]
Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments
(OSCORE)", draft-ietf-core-object-security-15 (work in
progress), August 2018.
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[ieee802-1AR]
IEEE Standard, ., "IEEE 802.1AR Secure Device Identifier",
2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
[RFC8366] Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
"A Voucher Artifact for Bootstrapping Protocols",
RFC 8366, DOI 10.17487/RFC8366, May 2018,
<https://www.rfc-editor.org/info/rfc8366>.
11.2. Informative References
[duckling]
Stajano, F. and R. Anderson, "The resurrecting duckling:
security issues for ad-hoc wireless networks", 1999,
<https://www.cl.cam.ac.uk/~fms27/
papers/1999-StajanoAnd-duckling.pdf>.
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[I-D.kumar-dice-dtls-relay]
Kumar, S., Keoh, S., and O. Garcia-Morchon, "DTLS Relay
for Constrained Environments", draft-kumar-dice-dtls-
relay-02 (work in progress), October 2014.
[pledge] Dictionary.com, ., "Dictionary.com Unabridged", 2015,
<http://dictionary.reference.com/browse/pledge>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<https://www.rfc-editor.org/info/rfc4944>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/info/rfc6690>.
[RFC6775] Shelby, Z., Ed., Chakrabarti, S., Nordmark, E., and C.
Bormann, "Neighbor Discovery Optimization for IPv6 over
Low-Power Wireless Personal Area Networks (6LoWPANs)",
RFC 6775, DOI 10.17487/RFC6775, November 2012,
<https://www.rfc-editor.org/info/rfc6775>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/info/rfc7228>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>.
Authors' Addresses
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
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Peter van der Stok
vanderstok consultancy
Email: consultancy@vanderstok.org
Panos Kampanakis
Cisco Systems
Email: pkampana@cisco.com
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