6tisch Working Group M. Richardson
Internet-Draft Sandelman Software Works
Intended status: Informational October 22, 2018
Expires: April 25, 2019
6tisch Zero-Touch Secure Join protocol
draft-ietf-6tisch-dtsecurity-zerotouch-join-03
Abstract
This document describes a Zero-touch Secure Join (ZSJ) mechanism to
enroll a new device (the "pledge") into a IEEE802.15.4 TSCH network
using the 6tisch signaling mechanisms. The resulting device will
obtain a domain specific credential that can be used with either
802.15.9 per-host pair keying protocols, or to obtain the network-
wide key from a coordinator. The mechanism describe here is an
augmentation to the one-touch mechanism described in
[I-D.ietf-6tisch-minimal-security], and a constrained version of
[I-D.ietf-anima-bootstrapping-keyinfra].
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Prior Bootstrapping Approaches . . . . . . . . . . . . . 6
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Scope of solution . . . . . . . . . . . . . . . . . . . . 7
1.3.1. Support environment . . . . . . . . . . . . . . . . . 8
1.3.2. Constrained environments . . . . . . . . . . . . . . 8
1.3.3. Network Access Controls . . . . . . . . . . . . . . . 8
1.4. Leveraging the new key infrastructure / next steps . . . 8
1.4.1. Key Distribution Process . . . . . . . . . . . . . . 8
1.5. Requirements for Autonomic Network Infrastructure (ANI)
devices . . . . . . . . . . . . . . . . . . . . . . . . . 8
2. Architectural Overview . . . . . . . . . . . . . . . . . . . 8
2.1. Behavior of a Pledge . . . . . . . . . . . . . . . . . . 9
2.2. Secure Imprinting using Vouchers . . . . . . . . . . . . 10
2.3. Initial Device Identifier . . . . . . . . . . . . . . . . 10
2.3.1. Identification of the Pledge . . . . . . . . . . . . 11
2.3.2. MASA URI extension . . . . . . . . . . . . . . . . . 12
2.4. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . 12
2.5. Architectural Components . . . . . . . . . . . . . . . . 13
2.5.1. Pledge . . . . . . . . . . . . . . . . . . . . . . . 13
2.5.2. Stateless IPIP Join Proxy . . . . . . . . . . . . . . 13
2.5.3. Domain Registrar . . . . . . . . . . . . . . . . . . 13
2.5.4. Manufacturer Service . . . . . . . . . . . . . . . . 14
2.5.5. Public Key Infrastructure (PKI) . . . . . . . . . . . 14
2.6. Certificate Time Validation . . . . . . . . . . . . . . . 14
2.6.1. Lack of realtime clock . . . . . . . . . . . . . . . 14
2.6.2. Infinite Lifetime of IDevID . . . . . . . . . . . . . 14
2.7. Cloud Registrar . . . . . . . . . . . . . . . . . . . . . 14
2.8. Determining the MASA to contact . . . . . . . . . . . . . 15
3. Voucher-Request artifact . . . . . . . . . . . . . . . . . . 15
4. Proxying details (Pledge - Proxy - Registrar) . . . . . . . . 15
5. Proxy details . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1. Pledge discovery of Proxy . . . . . . . . . . . . . . . . 15
5.2. CoAP connection to Registrar . . . . . . . . . . . . . . 16
5.3. HTTPS proxy connection to Registrar . . . . . . . . . . . 16
5.4. Proxy discovery of Registrar . . . . . . . . . . . . . . 16
6. Protocol Details (Pledge - Registrar - MASA) . . . . . . . . 16
6.1. BRSKI-EST (D)TLS establishment details . . . . . . . . . 17
6.1.1. BRSKI-EST CoAP/DTLS estasblishment details . . . . . 17
6.1.2. BRSKI-EST CoAP/EDHOC estasblishment details . . . . . 17
6.2. Pledge Requests Voucher from the Registrar . . . . . . . 19
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6.3. BRSKI-MASA TLS establishment details . . . . . . . . . . 19
6.4. Registrar Requests Voucher from MASA . . . . . . . . . . 19
6.4.1. MASA renewal of expired vouchers . . . . . . . . . . 20
6.4.2. MASA verification of voucher-request signature
consistency . . . . . . . . . . . . . . . . . . . . . 20
6.4.3. MASA authentication of registrar (certificate) . . . 20
6.4.4. MASA revocation checking of registrar (certificate) . 20
6.4.5. MASA verification of pledge prior-signed-voucher-
request . . . . . . . . . . . . . . . . . . . . . . . 21
6.4.6. MASA pinning of registrar . . . . . . . . . . . . . . 21
6.4.7. MASA nonce handling . . . . . . . . . . . . . . . . . 21
6.5. MASA Voucher Response . . . . . . . . . . . . . . . . . . 21
6.5.1. Pledge voucher verification . . . . . . . . . . . . . 22
6.5.2. Pledge authentication of provisional TLS connection . 22
6.6. Pledge Voucher Status Telemetry . . . . . . . . . . . . . 22
6.7. Registrar audit log request . . . . . . . . . . . . . . . 22
6.7.1. MASA audit log response . . . . . . . . . . . . . . . 22
6.7.2. Registrar audit log verification . . . . . . . . . . 22
6.8. EST Integration for PKI bootstrapping . . . . . . . . . . 22
6.8.1. EST Distribution of CA Certificates . . . . . . . . . 22
6.8.2. EST CSR Attributes . . . . . . . . . . . . . . . . . 23
6.8.3. EST Client Certificate Request . . . . . . . . . . . 23
6.8.4. Enrollment Status Telemetry . . . . . . . . . . . . . 23
6.8.5. Multiple certificates . . . . . . . . . . . . . . . . 23
6.8.6. EST over CoAP . . . . . . . . . . . . . . . . . . . . 23
6.9. Use of Secure Transport for Minimal Join . . . . . . . . 23
7. Reduced security operational modes . . . . . . . . . . . . . 24
7.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 24
7.2. Pledge security reductions . . . . . . . . . . . . . . . 24
7.3. Registrar security reductions . . . . . . . . . . . . . . 24
7.4. MASA security reductions . . . . . . . . . . . . . . . . 24
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8.1. Well-known EST registration . . . . . . . . . . . . . . . 24
8.2. PKIX Registry . . . . . . . . . . . . . . . . . . . . . . 24
8.3. Voucher Status Telemetry . . . . . . . . . . . . . . . . 24
8.4. DNS Service Names . . . . . . . . . . . . . . . . . . . . 25
8.5. MUD File Extension for the MASA server . . . . . . . . . 25
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 25
9.1. Privacy Considerations for Production network . . . . . . 25
9.2. Privacy Considerations for New Pledges . . . . . . . . . 25
9.2.1. EUI-64 derived address for join time IID . . . . . . 26
9.3. Privacy Considerations for Join Proxy . . . . . . . . . . 26
10. Security Considerations . . . . . . . . . . . . . . . . . . . 26
10.1. Security of MASA voucher signing key(s) . . . . . . . . 26
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 27
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
12.1. Normative References . . . . . . . . . . . . . . . . . . 27
12.2. Informative References . . . . . . . . . . . . . . . . . 31
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Appendix A. Extra text . . . . . . . . . . . . . . . . . . . . . 32
A.1. Assumptions . . . . . . . . . . . . . . . . . . . . . . . 32
A.1.1. One-Touch Assumptions . . . . . . . . . . . . . . . . 32
A.1.2. Factory provided credentials (if any) . . . . . . . . 33
A.1.3. Credentials to be introduced . . . . . . . . . . . . 33
A.2. Network Assumptions . . . . . . . . . . . . . . . . . . . 33
A.2.1. Security above and below IP . . . . . . . . . . . . . 33
A.2.2. Join network assumptions . . . . . . . . . . . . . . 34
A.2.3. Number and cost of round trips . . . . . . . . . . . 35
A.2.4. Size of packets, number of fragments . . . . . . . . 35
A.3. Target end-state for join process . . . . . . . . . . . . 35
Appendix B. Join Protocol . . . . . . . . . . . . . . . . . . . 35
B.1. Key Agreement process . . . . . . . . . . . . . . . . . . 36
B.2. Provisional Enrollment process . . . . . . . . . . . . . 36
Appendix C. IANA Considerations . . . . . . . . . . . . . . . . 37
Appendix D. Protocol Definition . . . . . . . . . . . . . . . . 37
D.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 37
D.1.1. Proxy Discovery Protocol Details . . . . . . . . . . 38
D.1.2. Registrar Discovery Protocol Details . . . . . . . . 38
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 38
1. Introduction
Enrollment of new nodes into LLNs present unique challenges. The
constrained nodes has no user interfaces, and even if they did,
configuring thousands of such nodes manually is undesireable from a
human resources issue, as well as the difficulty in getting
consistent results.
This document is about a standard way to introduce new nodes into a
6tisch network that does not involve any direct manipulation of the
nodes themselves. This act has been called "zero-touch"
provisioning, and it does not occur by chance, but requires
coordination between the manufacturer of the node, the service
operator running the LLN, and the installers actually taking the
devices out of the shipping boxes.
This document is a constrained profile of
[I-D.ietf-anima-bootstrapping-keyinfra]. The above document/protocol
is referred by by it's acronym: BRSKI. The pronounciation of which
is "brew-ski", a common north american slang for beer with a pseudo-
polish ending. This constrained protocol is called ZSJ (pronounced
zees-Jay).
This document follows the same structure as BRSKI in order to
emphasize the similarities, but specializes a number of things to
constrained networks of constrained devices. Like
[I-D.ietf-anima-bootstrapping-keyinfra], the networks which are in
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scope for this protocol are deployed by a professional operator. The
deterministic mechanisms which have been designed into 6tisch have
been created to satisfy the operational needs of industrial settings
where such an operator exists.
This document builds upon the "one-touch" provisioning described in
[I-D.ietf-6tisch-minimal-security], reusing the OSCOAP Join Request
mechanism when appropriate, but preceeding it with either the EDHOC
key agreement protocol, or a DTLS setup process. The [RFC7030] EST
protocol extended in [I-D.ietf-6tisch-minimal-security], has been
mapped by [I-D.ietf-ace-coap-est] into CoAP, and has the same
security profile as this protocol.
Whenever possible, this document does not introduce new protocols or
mechanisms, but rather integrates them from other documents.
Otherwise, this document follows BRSKI with the following high-level
changes:
o HTTP is replaced with CoAP.
o TLS (HTTPS) is replaced with either DTLS+CoAP, or EDHOC/
OSCOAP+CoAP
o the domain-registrar anchor certificate is replaced with a Raw
Public Key (RPK) using [RFC7250].
o the PKCS7 signed JSON voucher format is replaced with CWT
o the GRASP discovery mechanism for the Proxy is replaced with an
announcement in the Enhanced Beacon
[I-D.richardson-6tisch-join-enhanced-beacon]
o the TCP circuit proxy mechanism is not used. The IPIP mechanism
if mandatory to implement when deployed with DTLS, while the CoAP
based stateless proxy mechanism is used for OSCOAP/EDHOC.
o real time clocks are assumed to be unavailable, so expiry dates in
ownership vouchers are never used
o nonce-full vouchers are encouraged, but off-line nonce-less
operation is also supported, however, the resulting vouchers have
infinite life.
802.1AR Client Certificates (IDevID) are retained, but optionally are
specified by reference rather than value.
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It is expected that the back-end network operator infrastructure
would be able to bootstrap ANIMA BRSKI-type devices over ethernet,
while also being able bootstrap 6tisch devices over 802.15.4 with few
changes.
NOTE TO RFC-EDITOR: during production of this document, it was
matched against [I-D.ietf-anima-bootstrapping-keyinfra] section by
section. This results in a few sections, such as IANA Considerations
where there is no requested activity. Those sections are marked "NO
ACTION, PLEASE REMOVE" and should be removed (along with this
paragraph) from the final document. Some sections are marked as "no
changes" and should be left in place so that the section numbering
remains consistent with [I-D.ietf-anima-bootstrapping-keyinfra].
1.1. Prior Bootstrapping Approaches
Constrained devices as used in industrial control systems are usually
installed (or replaced) by technicians with expertise in the
equipment being serviced, not in secure enrollment of devices.
Devices therefore are typically pre-configured in advance, marked for
a particular factory, assembly line, or even down to the specific
machine. It is not uncommon for manufacturers to have a product code
(stock keeping unit -SKU) for each part, and for each customer as the
part will be loaded with customer specifc security configuration.
The resulting customer-specific parts are hard to inventory and
spare, and should parts be delivered to the wrong customer,
determining the reason for inability to configure is difficult and
time consuming.
End-user actions to configure the part at the time of installation,
aside from being error prone, also suffer from requiring a part that
has an interface.
1.2. Terminology
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.
The reader is expected to be familiar with the terms and concepts
defined in [I-D.ietf-6tisch-terminology], [RFC7252],
[I-D.ietf-core-object-security], and
[I-D.ietf-anima-bootstrapping-keyinfra]. The following terms are
imported: drop ship, imprint, enrollment, pledge, join proxy,
ownership voucher, join registrar/coordinator. The following terms
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are repeated here for readability, but this document is not
authoritative for their definition:
pledge the prospective device, which has the identity provided to at
the factory. Neither the device nor the network knows if the
device yet knows if this device belongs with this network.
Joined Node the prospective device, after having completing the join
process, often just called a Node.
Join Proxy (JP): a stateless relay that provides connectivity
between the pledge and the join registrar/coordinator.
Join Registrar/Coordinator (JRC): central entity responsible for
authentication and authorization of joining nodes.
Audit Token A signed token from the manufacturer authorized signing
authority indicating that the bootstrapping event has been
successfully logged. This has been referred to as an
"authorization token" indicating that it authorizes bootstrapping
to proceed.
Ownership Voucher A signed voucher from the vendor vouching that a
specific domain "owns" the new entity as defined in
[I-D.ietf-anima-voucher].
MIC manufacturer installed certificate. An [ieee802-1AR] identity.
Not to be confused with a (cryptographic) "Message Integrity
Check"
1.3. Scope of solution
The solution described in this document is appropriate to enrolling
between hundreds to hundreds of thousands of diverse devices into a
network without any prior contact with the devices. The devices
could be shipped by the manufacturer directly to the customer site
without ever being seen by the operator of the network. As described
in BRSKI, in the audit-mode of operation the device will be claimed
by the first network that sees it. In the tracked owner mode of
operation, sales channel integration provides a strong connection
that the operator of the network is the legitimate owner of the
device.
BRSKI describes a more general, more flexible approach for
bootstrapping devices into an ISP or Enterprise network.
[I-D.ietf-6tisch-minimal-security] provides an extremely streamlined
approach to enrolling from hundreds to thousands of devices into a
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network, provided that a unique secret key can be installed in each
device.
1.3.1. Support environment
TBD
1.3.2. Constrained environments
TBD
1.3.3. Network Access Controls
TBD
1.4. Leveraging the new key infrastructure / next steps
In constrained networks, it is unlikely that an ACP be formed. This
document does not preclude such a thing, but it is not mandated.
The resulting secure channel MAY be used just to distribute network-
wide keys using a protocol such as
[I-D.ietf-6tisch-minimal-security]. (XXX - do we need to signal this
somehow?)
The resulting secure channel MAY be instead used to do an enrollment
of an LDevID as in BRSKI, but the resulting certificate is used to do
per-pair keying such as described by {{ieee802159}.
1.4.1. Key Distribution Process
In addition to being used for the initial enrollment process, the
secure channel may be kept open (and reversed) to use for network
rekeying. Such a process is out of scope of this document, please
see future work such as [I-D.richardson-6tisch-minimal-rekey].
1.5. Requirements for Autonomic Network Infrastructure (ANI) devices
TBD
2. Architectural Overview
Section 2 of BRSKI has a diagram with all of the components shown
together. There are no significant changes to the diagram.
The use of a circuit proxy is not mandated. Instead the IPIP
mechanism described in appendix C ("IPIP Join Proxy mechanism")
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SHOULD be be used instead as it supports both DTLS, EDHOC and OSCOAP
protocols.
The CoAP proxy mechanism MAY be implemented instead: the decision
depends upon the capabilities of the Registrar and the proxy. A
mechanism is included for the Registrar to announce it's capabilities
(XXX)
2.1. Behavior of a Pledge
The pledge goes through a series of steps which are outlined here at
a high level.
+--------------+
| Factory |
| default |
+------+-------+
|
+------v-------+
| (1) Discover |
+------------> |
| +------+-------+
| |
| +------v-------+
| | (2) Identity |
^------------+ |
| rejected +------+-------+
| |
| +------v-------+
| | (3) Request |
| | Join |
| +------+-------+
| |
| +------v-------+
| | (4) Imprint |
^------------+ |
| Bad MASA +------+-------+
| response | send Voucher Status Telemetry
| +------v-------+
| | (5) Enroll |
^------------+ |
| Enroll +------+-------+
| Failure |
| +------v-------+
| | (6) Enrolled |
^------------+ |
Factory +--------------+
reset
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State descriptions for the pledge are as follows:
1. Discover a communication channel to a Registrar. This is done by
listening for beacons as described by
[I-D.richardson-anima-6join-discovery]
2. Identify itself. This is done by presenting an X.509 IDevID
credential to the discovered Registrar (via the Proxy) in a DTLS
or EDHOC handshake. (The Registrar credentials are only
provisionally accepted at this time).
The registrar identifies itself using a raw public key, while the
the pledge identifies itself to the registrar using an IDevID
credential.
3. Requests to Join the discovered Registrar. A unique nonce can be
included ensuring that any responses can be associated with this
particular bootstrapping attempt.
4. Imprint on the Registrar. This requires verification of the
vendor service (MASA) provided voucher. A voucher contains
sufficient information for the Pledge to complete authentication
of a Registrar. The voucher is signed by the vendor (MASA) using
a raw public key, previously installed into the pledge at
manufacturing time.
5. Optionally Enroll. By accepting the domain specific information
from a Registrar, and by obtaining a domain certificate from a
Registrar using a standard enrollment protocol, e.g. Enrollment
over Secure Transport (EST) [RFC7030].
6. The Pledge is now a member of, and can be managed by, the domain
and will only repeat the discovery aspects of bootstrapping if it
is returned to factory default settings.
2.2. Secure Imprinting using Vouchers
As in BRSKI, the format and cryptographic mechansim of vouchers is
described in detail in [I-D.ietf-anima-voucher]. As described in
section YYY, the physical format for vouchers in this document
differs from that of BRSKI, in that it uses
[I-D.ietf-ace-cbor-web-token] to encode the voucher and to sign it.
2.3. Initial Device Identifier
The essential component of the zero-touch operation is that the
pledge is provisioned with an 802.1AR (PKIX) certificate installed
during the manufacturing process.
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It is expected that constrained devices will use a signature
algorithm corresponding to the hardware acceleration that they have,
if they have any. The anticipated algorithms are the ECDSA P-256
(secp256p1), and SHOULD be supported. Newer devices SHOULD begin to
appear using EdDSA curves using the 25519 curves.
The manufacturer will always know what algorithms are available in
the Pledge, and will use an appropriate one. The other components
that need to evaluate the IDevID (the Registrar and MASA) are
expected to support all common algorithms.
There are a number of simplications detailed later on in this
document designed to eliminate the need for an ASN.1 parser in the
pledge.
The pledge should consider it's 802.1AR certificate to be an opaque
blob of bytes, to be inserted into protocols at appropriate places.
The pledge SHOULD have access to it's public and private keys in the
most useable native format for computation.
The pledge MUST have the public key of the MASA built in a
manufacturer time. This is a seemingly identical requirement as for
BRSKI, but rather than being an abstract trust anchor that can be
augmented with a certificate chain, the pledge MUST be provided with
the Raw Public Key that the MASA will use to sign vouchers for that
pledge.
There are a number of security concerns with use of a single MASA
signing key, and section Section 10.1 addresses some of them with
some operational suggestions.
BRSKI places some clear requirements upon the contents of the IDevID,
but leaves the exact origin of the voucher serial-number open. This
document restricts the process to being the hwSerialNum OCTET STRING.
As CWT can handle binary formats, no base64 encoding is necessary.
The use of the MASA-URL extension is encouraged if the certificate is
sent at all.
EDNOTE: here belongs text about sending only a reference to the
IDevID rather than the entire certificate
2.3.1. Identification of the Pledge
TBD
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2.3.2. MASA URI extension
TBD
2.4. Protocol Flow
The diagram from BRSKI is reproduced with some edits:
+--------+ +---------+ +------------+ +------------+
| Pledge | | IPIP | | Domain | | Vendor |
| | | Proxy | | Registrar | | Service |
| | | | | (JRC) | | (MASA) |
+--------+ +---------+ +------------+ +------------+
| | | |
|<-RFC4862 IPv6 adr | | |
| | | |
|<--------------------| | |
| Enhanced Beacon | | |
| periodic broadcast| | |
| | | |
|<------------------->C<----------------->| |
| DTLS via the IPIP Proxy | |
|<--Registrar DTLS server authentication--| |
[PROVISIONAL accept of server cert] | |
P---X.509 client authentication---------->| |
P | | |
P---Voucher Request (include nonce)------>| |
P | | |
P | | |
P | [accept device?] |
P | [contact Vendor] |
P | |--Pledge ID-------->|
P | |--Domain ID-------->|
P | |--nonce------------>|
P | | [extract DomainID]
P | | |
P | | [update audit log]
P | | |
P | | |
P | | |
P | | |
P | | |
P | |<-device audit log--|
P | |<- voucher ---------|
P | | |
P | | |
P | [verify audit log and voucher] |
P | | |
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P<------voucher---------------------------| |
[verify voucher ] | | |
[verify provisional cert| | |
| | | |
|<--------------------------------------->| |
| Continue with RFC7030 enrollment | |
| using now bidirectionally authenticated | |
| DTLS session. | | |
| | | |
|<--------------------------------------->| |
| Use 6tisch-minimal-security join request |
Noteable changes are:
1. no IPv4 support/options.
2. no mDNS steps, 6tisch only uses Enhanced Beacon
3. nonce-full option is always mandatory
2.5. Architectural Components
The bootstrap process includes the following architectural
components:
2.5.1. Pledge
The Pledge is the device which is attempting to join. Until the
pledge completes the enrollment process, it has network connectivity
only to the Proxy.
2.5.2. Stateless IPIP Join Proxy
The stateless CoAP or DTLS Proxy provides CoAP or DTLS connectivity
(respectively) between the pledge and the registrar. The stateless
CoAP proxy mechanism is described in
[I-D.ietf-6tisch-minimal-security] section 5.1.
The stateless DTLS mechanism is not yet described (TBD).
2.5.3. Domain Registrar
The Domain Registrar (having the formal name Join Registrar/
Coordinator (JRC)), operates as a CMC Registrar, terminating the EST
and BRSKI connections. The Registrar is manually configured or
distributed with a list of trust anchors necessary to authenticate
any Pledge device expected on the network. The Registrar
communicates with the Vendor supplied MASA to establish ownership.
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The JRC is typically located on the 6LBR/DODAG root, but it may be
located elsewhere, provided IP level connectivity can be established.
The 6LBR may also provide a proxy or relay function to connect to the
actual registrar in addition to the IPIP proxy described above. The
existence of such an additional proxy is a private matter, and this
documents assumes without loss of generality that the registrar is
co-located with the 6LBR.
2.5.4. Manufacturer Service
The Manufacturer Service provides two logically seperate functions:
the Manufacturer Authorized Signing Authority (MASA), and an
ownership tracking/auditing function. This function is identical to
that used by BRSKI, except that a different format voucher is used.
2.5.5. Public Key Infrastructure (PKI)
TBD
2.6. Certificate Time Validation
2.6.1. Lack of realtime clock
For the constrained situation it is assumed that devices have no real
time clock. These nodes do have access to a monotonically increasing
clock that will not go backwards in the form of the Absolute Sequence
Number. Synchronization to the ASN is required in order to transmit/
receive data and most nodes will maintain it in hardware.
The heuristic described in BRSKI under this section SHOULD be applied
if there are dates in the CWT format voucher.
Voucher requests SHOULD include a nonce. For devices intended for
off-line deployment, the vouchers will have been generated in advance
and no nonce-ful operation will not be possible.
2.6.2. Infinite Lifetime of IDevID
TBD
2.7. Cloud Registrar
In 6tisch, the pledge never has network connectivity until it is
enrolled, so no alternate registrar is ever possible.
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2.8. Determining the MASA to contact
There are no changes from BRSKI: the IDevID provided by the pledge
will contain a MASA URL extension.
3. Voucher-Request artifact
The voucher-request artifact is defined in
[I-D.ietf-anima-constrained-voucher] section 6.1.
For the 6tisch ZSJ protocol defined in this document, only COSE
signed vouchers as described in [I-D.ietf-anima-constrained-voucher]
section 6.3.2 are supported.
4. Proxying details (Pledge - Proxy - Registrar)
The voucher-request artifact is defined in
[I-D.ietf-anima-constrained-voucher].
The 6tisch use of the constrained version differs from the non-
constrained version in two ways:
1. it does not include the pinned-domain-cert, but rather than
pinned-domain-subjet-public-key-info entry. This accomodates the
use of a raw public key to identify the registrar.
2. the pledge voucher-request is never signed.
An appendix shows detailed examples of COSE format voucher requests.
5. Proxy details
The role of the Proxy is to facilitate communication. In the
constrained situation the proxy needs to be stateless as there is
very little ram to begin with, and none can be allocated to keep
state for an unlimited number of potential pledges.
5.1. Pledge discovery of Proxy
In BRSKI, the pledge discovers the proxy via use of a GRASP M_FLOOD
messages sent by the proxy. In 6tisch ZSJ, the existence of the
proxy is announced by the Enhanced Beacon message described in
[I-D.richardson-6tisch-enrollment-enhanced-beacon]. The proxy as
described by [I-D.ietf-6tisch-minimal-security] section 10 is to be
used in an identical fashion when EDHOC and OSCOAP are used.
When DTLS security is provided, then the proxy mechanism described in
TBD must be used.
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5.2. CoAP connection to Registrar
In BRSKI CoAP is future work. This document represents this work.
5.3. HTTPS proxy connection to Registrar
HTTPS connections are not used between the Pledge, Proxy and
Registrar. The Proxy relays CoAP or DTLS packets and does not
interpret or terminate either CoAP or DTLS connections. (HTTPS is
still used between the Registrar and MASA)
5.4. Proxy discovery of Registrar
In BRSKI, the proxy autonomically discovers the Registrar by
listening for GRASP messages.
In the constrained network, the proxies are optionally configured
with the address of the JRC by the Join Response in in
[I-D.ietf-6tisch-minimal-security] section 9.3.2. (As described in
that section, the address of the registrar otherwise defaults to be
that of the DODAG root)
Whether or not a 6LR will announce itself as a possible Join Proxy is
outside the scope of this document.
6. Protocol Details (Pledge - Registrar - MASA)
BRSKI is specified to run over HTTPS. This document respecifies it
to run over CoAP with either DTLS or EDHOC-provided OSCOAP security.
BRSKI introduces the concept of a provisional state for EST.
The same situation must also be added to DTLS: a situation where the
connection is active but the identity of the Registar has not yet
been confirmed. The DTLS MUST validate that the exchange has been
signed by the Raw Public Key that is presented by the Server, even
though there is as yet no trust in that key. Such a key is often
available through APIs that provide for channel binding, such as
described in [RFC5056].
There is an emerging (hybrid) possibility of DTLS-providing the
OSCOAP security, but such a specification does not yet exist, and
this document does at this point specify it.
[I-D.ietf-ace-coap-est] specifies that CoAP specifies the use of CoAP
Block-Wise Transfer ("Block") [RFC7959] to fragment EST messages at
the application layer.
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BRSKI introduces the concept of a provisional state for EST. The
same situation must also be added to DTLS: a situation where the
connection is active but the identity of the Registar has not yet
been confirmed.
The DTLS MUST validate that the exchange has been signed by the Raw
Public Key that is presented by the Server, even though there is as
yet no trust in that key. Such a key is often available through APIs
that provide for channel binding, such as described in [RFC5056].
As in [I-D.ietf-ace-coap-est], support for Observe CoAP options
[RFC7641] with BRSKI is not supported in the current BRSKI/EST
message flows.
Observe options could be used by the server to notify clients about a
change in the cacerts or csr attributes (resources) and might be an
area of future work.
Redirection as described in [RFC7030] section 3.2.1 is NOT supported.
6.1. BRSKI-EST (D)TLS establishment details
6tisch ZSJ does not use TLS. The connection is either CoAP over
DTLS, or CoAP with EDHOC security.
6.1.1. BRSKI-EST CoAP/DTLS estasblishment details
The details in the BRSKI document apply directly to use of DTLS.
The registrar SHOULD authenticate itself with a raw public key. A
256 bit ECDSA raw public key is RECOMMENDED. Pledges SHOULD support
EDDSA keys if they contain hardware that supports doing so
efficiently.
TBD: the Pledge needs to signal what kind of Raw Public Key it
supports before the Registrar sends its ServerCertificate. Can SNI
be used to do this?
The pledge SHOULD authenticate itself with the built-in IDevID
certificate as a ClientCertificate.
6.1.2. BRSKI-EST CoAP/EDHOC estasblishment details
[I-D.selander-ace-cose-ecdhe] details how to use EDHOC. The EDHOC
description identifiers a party U (the initiator), and a party V.
The Pledge is the party U, and the JRC is the party V.
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The communication from the Pledge is via CoAP via the Join Proxy.
The Join proxy relays traffic to the JRC, and using the mechanism
described in [I-D.ietf-6tisch-minimal-security] section 5.1. This is
designed so that the Join Proxy does not need to know if it is
performing the one-touch enrollment described in
[I-D.ietf-6tisch-minimal-security] or the zero-touch enrollment
protocol described in this document. A network could consist of a
mix of nodes of each type.
As generating ephemeral keys is expensive for a low-resource Pledge,
the use of a common E_U by the Pledge for multiple enrollment
attempts (should the first turn out to be the wrong network) is
encouraged.
The first communication detailed in [I-D.ietf-ace-coap-est] is to
query the "/.well-known/core" resource to request the Link for EST.
This is where the initial CoAP request is to sent.
The JRC MAY replace it's E_V ephermal key on a periodic basis, or
even for every communication session.
The Pledge's ID_U is the Pledge's IDevID. It is transmitted in an
x5bag [I-D.schaad-cose-x509]. An x5u (URL) MAY be used. An x5t
(hash) MAY also be used and would be the smallest, but the Registrar
may not know where to find the Pledge's IDevID unless the JRC has
been preloaded will all the IDevIDs via out-of-band mechanism. It is
impossible for the Pledge to know if the JRC has been loaded in such
a way so x5t is discouraged for general use.
The JRC's ID_V is the JRC's Raw Public Key. It is transmitted as a
key in COSE's YYY parameter.
The initial Mandatory to Implement (MTI) of an HKDF of SHA2-256, an
AEAD based upon AES-CCM-16-64-128, a signature verification of BBBB,
and signature generation of BBBB. The Pledge proposes a set of
algorithms that it supports, and Pledge need not support more than
one combination.
JRCs are expected to run on non-constrained servers, and are expected
to support the above initial MTI, and any subsequent ones that become
common. A JRC SHOULD support all available algorithms for a
significant amount of time. Even when algorithms become weak or
suspect, it is likely that it will still have to perform secure join
for older devices. A JRC that responds to such an older device might
not in the end accept the device into the network, but it is
important that it be able to audit the event and communicate the
event to an operator.
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While EDHOC supports sending additional data in the message_3, in the
constrained network situation, it is anticipated that the size of the
this message will already be large, and no additional data is to be
sent.
A COAP confirmable message SHOULD be used.
[I-D.ietf-6tisch-minimal-security] section 6 details how to setup
OSCORE context given a shared key derived by EDHOC.
The registrar SHOULD authenticate itself with a raw public key.
The pledge SHOULD authenticate itself with the built-in IDevID
certificate.
6.2. Pledge Requests Voucher from the Registrar
The voucher request and response as defined by BRSKI is modified
slightly.
In order to simplify the pledge, the use of a certificate (and chain)
for the Registrar is not supported. Instead the newly defined
pinned-domain-subject-public-key-info must contain the (raw) public
key info for the Registrar. It MUST be byte for byte identical to
that which is transmitted by the Registrar during the TLS
ServerCertificate handshake.
BRSKI permits the voucher request to be signed or unsigned. This
document defines the voucher request to be unsigned.
6.3. BRSKI-MASA TLS establishment details
There are no changes. The connection from the Registrar to MASA is
still HTTPS.
6.4. Registrar Requests Voucher from MASA
There are no change from BRSKI, as this step is between two non-
constrained devices.
The format of the voucher is COSE, which implies changes to both the
Registrar and the MASA, but semantically the content is the same.
The format of the voucher is COSE, which implies changes to both the
Registrar and the MASA, but semantically the content is the same.
The manufacturer will know what algorithms are supported by the
pledge, and will issue a 406 (Conflict) error to the Registrar if the
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Registar's public key format is not supported by the pledge. It is
however, too late for the Registar to use a different key, but at
least it can log a reason for a failure. It is likely that the ZSJ-
BRSKI-EST connection has already failed, and this step is never
reached.
6.4.1. MASA renewal of expired vouchers
There are assumed to be no useful real-time clocks on constrained
devices, so all vouchers are in effect infinite duration. Pledges
will use nonces for freshness, and a request for a new voucher with a
new voucher for the same Registrar is not unusual. A token-bucket
system SHOULD be used such that no more than 24 vouchers are issued
per-day, but more than one voucher can be issued in a one hour
period. Tokens should not accumulate for more than one day!
6.4.2. MASA verification of voucher-request signature consistency
The voucher-request is signed by the Registrar using it's Raw Public
Key. There is no additional certificate authority to sign this key.
The MASA MAY have this key via sales-channel integration, but in most
cases it will be seeing the key for the first time.
XXX-should the TLS connection from Registrar to MASA have a
ClientCertificate? If so, then should it use the same Public Key?
Or a different one?
6.4.3. MASA authentication of registrar (certificate)
IDEA: The MASA SHOULD pin the Raw Public Key (RPK) to the IP address
that was first used to make a request with it. Should the RPK <-> IP
address relationship be 1:1, 1:N, N:1? Should we take IP address to
mean, "IP subnet", essentially the IPv4/24, and IPv6/64? The value
of doing is about DDoS mitigation?
Should above mapping be on a per-Pledge basis?
6.4.4. MASA revocation checking of registrar (certificate)
As the Registrar has a Raw Public Key as an identity, there is no
meaningful standard revocation checking that can be done. The MASA
SHOULD have a blacklist table, and a way to add entries, but this
process is out of scope.
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6.4.5. MASA verification of pledge prior-signed-voucher-request
The MASA will know whether or not the Pledge is capable of producing
a signed voucher-request for inclusion by the Registrar. In the case
where the Pledge can sign the voucher-request to the Registrar, then
the Registrar will have put it in the 'prior-signed-voucher-request'.
The MASA can verify the signature from the Pledge using the MASA's
copy of the Pledge's IDevID public key.
In many cases, the Pledge will not be capable of doing signatures in
real time, so no 'prior-signed-voucher-request' will be present. The
MASA will have rely on the audit log as a history function to
determine if the Pledge has previously been claimed, and to identify
situations where the claim from the Registrar is fraudulent.
6.4.6. MASA pinning of registrar
When the MASA creates a voucher, it puts the Registrar's Raw Public
Key into the 'pinned-domain-subject-public-key-info' leaf of the
voucher.
The MASA does not include the 'pinned-domain-cert' field.
6.4.7. MASA nonce handling
Use of nonces is highly RECOMMENDED, but there are situations where
not all components are connected at the same time in which the nonce
will not be present.
There are no significant changes from BRSKI.
6.5. MASA Voucher Response
As exaplained in [I-D.ietf-anima-constrained-voucher] section 6.3.2,
when a voucher is returned by the MASA to the JRC, a public key or
certificate container that will verify the voucher SHOULD also be
returned.
In order to do this, the MASA MAY return a multipart/mixed return,
within that body, two items SHOULD be returned:
1. An application/voucher-cose+cbor body.
2. An application/pkcs7-mime; smime-type=certs-only, or an
application/SOMETHING containing a Raw Public Key.
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A MASA is not obligated to return the public key, and MAY return only
the application/voucher-cose+cbor object. In that case, the JRC will
be unable to validate it.
6.5.1. Pledge voucher verification
The Pledge receives the voucher from the Registrar over it's CoAP
connection. It verifies the signature using the MASA anchor built
in, as in the BRSKI case.
6.5.2. Pledge authentication of provisional TLS connection
The BRSKI process uses the pinned-domain-cert field of the voucher to
validate the registrar's ServerCertificate. In the ZeroTouch case,
the voucher will contain a pinned-domain-subject-public-key-info
field containing the raw public key of the certificate. It should
match, byte-to-byte with the raw public key ServerCertificate.
6.6. Pledge Voucher Status Telemetry
The voucher status telemetry report is communicated from the pledge
to the registrar over CoAP channel. The shortened URL is as
described in table QQQ.
6.7. Registrar audit log request
There are no changes to the Registrar audit log request.
6.7.1. MASA audit log response
There are no changes to the MASA audit log response.
6.7.2. Registrar audit log verification
There are no changes to how the Registrar verifies the audit log.
6.8. EST Integration for PKI bootstrapping
TBD.
6.8.1. EST Distribution of CA Certificates
TBD.
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6.8.2. EST CSR Attributes
In 6tisch, no Autonomic Control Plane will be created, so none of the
criteria for SubjectAltname found in
[I-D.ietf-anima-autonomic-control-plane] apply.
The CSR Attributes request SHOULD NOT be performed.
6.8.3. EST Client Certificate Request
6tisch will use a certificate to:
1. to authenticate an 802.15.9 key agreement protocol.
2. to terminate an incoming DTLS or EDHOC key agreement as part of
application data protection.
It is recommended that the requested subjectAltName contain only the
[RFC4514] hwSerialNum.
6.8.4. Enrollment Status Telemetry
There are no changes to the status telemetry between Registrar and
MASA.
6.8.5. Multiple certificates
Multiple certificates are not supported.
6.8.6. EST over CoAP
This document and [I-D.ietf-ace-coap-est] detail how to run EST over
CoAP.
6.9. Use of Secure Transport for Minimal Join
Rather than bootstrap to a public key infrastructure, the secure
channel MAY instead be for the minimal security join process
described in [I-D.ietf-6tisch-minimal-security].
The desire to do a minimal-security join process is signaled by the
Registrar in it's voucher-request by including a 'join-process' value
of 'minimal'. The MASA copies this value into the voucher that is
creates, and also logs this to the audit log.
When the secure channel was created with EDHOC, then the keys setup
by EDHOC are simply used by OSCORE exactly as if they had been Pre-
Shared. The keys derived by EDHOC SHOULD be stored by both Registrar
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and Pledge as their long term key should the join process need to be
repeated.
7. Reduced security operational modes
This document defines a specific reduced security operational mode,
specifically:
1. X
2. Y
3. Z
7.1. Trust Model
TBD
7.2. Pledge security reductions
TBD
7.3. Registrar security reductions
TBD
7.4. MASA security reductions
TBD
8. IANA Considerations
XXX
8.1. Well-known EST registration
XXX
8.2. PKIX Registry
TBD
8.3. Voucher Status Telemetry
TBD
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8.4. DNS Service Names
TBD
8.5. MUD File Extension for the MASA server
TBD
9. Privacy Considerations
[I-D.ietf-6lo-privacy-considerations] details a number of privacy
considerations important in Resource Constrained nodes. There are
two networks and three sets of constrained nodes to consider. They
are: 1. the production nodes on the production network. 2. the new
pledges, which have yet to enroll, and which are on a join network.
3. the production nodes which are also acting as proxy nodes.
9.1. Privacy Considerations for Production network
The details of this are out of scope for this document.
9.2. Privacy Considerations for New Pledges
New Pledges do not yet receive Router Advertisements with PIO
options, and so configure link-local addresses only based upon
layer-2 addresses using the normal SLAAC mechanisms described in
[RFC4191].
These link-local addresses are visible to any on-link eavesdropper
(who is synchronized to the same Join Assistant), so regardless of
what is chosen they can be seen. This link-layer traffic is
encapsulated by the Join Proxy into IPIP packets and carried to the
JRC. The traffic SHOULD never leave the operator's network, will be
kept confidential by the layer-2 keys inside the LLN. As no outside
traffic can enter the join network, to do any ICMP scanning as
described in [I-D.ietf-6lo-privacy-considerations].
The join process described herein requires that some identifier
meaningful to the network operator be communicated to the JRC. The
join request with this object occurs within a secured CoAP channel,
although the link-local address configured by the pledge will be
visible in either the CoAP stateless proxy option (section 5.1 of
[I-D.ietf-6tisch-minimal-security]), or in the equivalent DTLS
stateless proxy option (reference TBD).
This need not be a manufacturer created EUI-64 as assigned by IEEE;
it could be another value with higher entropy and less interesting
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vendor/device information. Regardless of what is chosen, it can be
used to track where the device attaches.
For most constrained device, network attachment occurs very
infrequently, often only once in their lifetime, so tracking
opportunities may be rare. Once connected, the long 8-byte EUI64
layer-2 address is usually replaced with a short JRC assigned 2-byte
address.
Additionally, during the enrollment process, a DTLS connection or
EDHOC connection will be created. TLS1.3 will keep contents of the
certificates transmitted private while TLS 1.2 will not. If the
client certificate can be observed, then the device identity will be
visible to passive observers in the 802.11AR IDevID certificate that
is sent.
Even when TLS 1.3 is used, an active attacker could collect the
information by creating a rogue proxy.
The use of a manufacturer assigned EUI64 (whether derived from IEEE
assignment or created through another process during manufacturing
time) is encouraged.
9.2.1. EUI-64 derived address for join time IID
The IID used in the link-local address used during the join process
be a vendor assigned EUI-64. After the join process has concluded,
the device SHOULD be assigned a unique randomly generated long
address, and a unique short address (not based upon the vendor EUI-
64) for use at link-layer address. At that point, all layer-3
content is encrypted by the layer-2 key.
9.3. Privacy Considerations for Join Proxy
TBD.
10. Security Considerations
TBD
10.1. Security of MASA voucher signing key(s)
TBD
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11. Acknowledgements
Kristofer Pister helped with many non-IETF references.
12. References
12.1. Normative References
[cullenCiscoPhoneDeploy]
Jennings, C., "Transitive Trust Enrollment for Constrained
Devices", 2012, <http://www.lix.polytechnique.fr/hipercom/
SmartObjectSecurity/papers/CullenJennings.pdf>.
[I-D.ietf-6lo-privacy-considerations]
Thaler, D., "Privacy Considerations for IPv6 Adaptation
Layer Mechanisms", draft-ietf-6lo-privacy-
considerations-04 (work in progress), October 2016.
[I-D.ietf-6tisch-minimal]
Vilajosana, X., Pister, K., and T. Watteyne, "Minimal
6TiSCH Configuration", draft-ietf-6tisch-minimal-21 (work
in progress), February 2017.
[I-D.ietf-6tisch-minimal-security]
Vucinic, M., Simon, J., Pister, K., and M. Richardson,
"Minimal Security Framework for 6TiSCH", draft-ietf-
6tisch-minimal-security-06 (work in progress), May 2018.
[I-D.ietf-6tisch-terminology]
Palattella, M., Thubert, P., Watteyne, T., and Q. Wang,
"Terms Used in IPv6 over the TSCH mode of IEEE 802.15.4e",
draft-ietf-6tisch-terminology-10 (work in progress), March
2018.
[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-06 (work in progress),
October 2018.
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[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-anima-constrained-voucher]
Richardson, M., Stok, P., and P. Kampanakis, "Constrained
Voucher Artifacts for Bootstrapping Protocols", draft-
ietf-anima-constrained-voucher-02 (work in progress),
September 2018.
[I-D.ietf-anima-grasp]
Bormann, C., Carpenter, B., and B. Liu, "A Generic
Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
grasp-15 (work in progress), July 2017.
[I-D.ietf-anima-voucher]
Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
"Voucher Profile for Bootstrapping Protocols", draft-ietf-
anima-voucher-07 (work in progress), January 2018.
[I-D.ietf-core-comi]
Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP
Management Interface", draft-ietf-core-comi-03 (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.
[I-D.ietf-core-yang-cbor]
Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A.
Minaburo, "CBOR Encoding of Data Modeled with YANG",
draft-ietf-core-yang-cbor-07 (work in progress), September
2018.
[I-D.ietf-netconf-keystore]
Watsen, K., "YANG Data Model for a Centralized Keystore
Mechanism", draft-ietf-netconf-keystore-06 (work in
progress), September 2018.
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[I-D.richardson-6tisch-enrollment-enhanced-beacon]
Dujovne, D. and M. Richardson, "IEEE802.15.4 Informational
Element encapsulation of 6tisch Join and Enrollment
Information", draft-richardson-6tisch-enrollment-enhanced-
beacon-01 (work in progress), April 2018.
[I-D.richardson-6tisch-join-enhanced-beacon]
Dujovne, D. and M. Richardson, "IEEE802.15.4 Informational
Element encapsulation of 6tisch Join Information", draft-
richardson-6tisch-join-enhanced-beacon-03 (work in
progress), January 2018.
[I-D.richardson-6tisch-minimal-rekey]
Richardson, M., "Minimal Security rekeying mechanism for
6TiSCH", draft-richardson-6tisch-minimal-rekey-02 (work in
progress), August 2017.
[I-D.richardson-anima-6join-discovery]
Richardson, M., "GRASP discovery of Registrar by Join
Assistant", draft-richardson-anima-6join-discovery-00
(work in progress), October 2016.
[I-D.schaad-cose-x509]
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Headers for carrying and referencing X.509 certificates",
draft-schaad-cose-x509-02 (work in progress), July 2018.
[I-D.selander-ace-cose-ecdhe]
Selander, G., Mattsson, J., and F. Palombini, "Ephemeral
Diffie-Hellman Over COSE (EDHOC)", draft-selander-ace-
cose-ecdhe-10 (work in progress), September 2018.
[iec62591]
IEC, ., "62591:2016 Industrial networks - Wireless
communication network and communication profiles -
WirelessHART", 2016,
<https://webstore.iec.ch/publication/24433>.
[ieee802-1AR]
IEEE Standard, ., "IEEE 802.1AR Secure Device Identifier",
2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>.
[ieee802154]
IEEE Standard, ., "802.15.4-2015 - IEEE Standard for Low-
Rate Wireless Personal Area Networks (WPANs)", 2015,
<http://standards.ieee.org/findstds/
standard/802.15.4-2015.html>.
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[ieee802159]
IEEE Standard, ., "802.15.9-2016 - IEEE Approved Draft
Recommended Practice for Transport of Key Management
Protocol (KMP) Datagrams", 2016,
<http://standards.ieee.org/findstds/
standard/802.15.9-2016.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>.
[RFC4514] Zeilenga, K., Ed., "Lightweight Directory Access Protocol
(LDAP): String Representation of Distinguished Names",
RFC 4514, DOI 10.17487/RFC4514, June 2006,
<https://www.rfc-editor.org/info/rfc4514>.
[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>.
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217,
DOI 10.17487/RFC7217, April 2014,
<https://www.rfc-editor.org/info/rfc7217>.
[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>.
[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>.
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[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>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>.
12.2. 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>.
[I-D.ietf-ace-actors]
Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An
architecture for authorization in constrained
environments", draft-ietf-ace-actors-07 (work in
progress), October 2018.
[I-D.ietf-anima-autonomic-control-plane]
Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
Control Plane (ACP)", draft-ietf-anima-autonomic-control-
plane-18 (work in progress), August 2018.
[I-D.ietf-core-sid]
Veillette, M. and A. Pelov, "YANG Schema Item iDentifier
(SID)", draft-ietf-core-sid-04 (work in progress), June
2018.
[I-D.ietf-roll-useofrplinfo]
Robles, I., Richardson, M., and P. Thubert, "When to use
RFC 6553, 6554 and IPv6-in-IPv6", draft-ietf-roll-
useofrplinfo-23 (work in progress), May 2018.
[ISA100] "The Technology Behind the ISA100.11a Standard", June
2010, <http://www.isa100wci.org/Documents/PDF/
The-Technology-Behind-ISA100-11a-v-3_pptx>.
[PFS] Wikipedia, ., "Forward Secrecy", August 2016,
<https://en.wikipedia.org/w/
index.php?title=Forward_secrecy&oldid=731318899>.
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[pledge-word]
Dictionary.com, ., "Dictionary.com Unabridged", 2015,
<http://dictionary.reference.com/browse/pledge>.
[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191,
November 2005, <https://www.rfc-editor.org/info/rfc4191>.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[RFC5056] Williams, N., "On the Use of Channel Bindings to Secure
Channels", RFC 5056, DOI 10.17487/RFC5056, November 2007,
<https://www.rfc-editor.org/info/rfc5056>.
[RFC7554] Watteyne, T., Ed., Palattella, M., and L. Grieco, "Using
IEEE 802.15.4e Time-Slotted Channel Hopping (TSCH) in the
Internet of Things (IoT): Problem Statement", RFC 7554,
DOI 10.17487/RFC7554, May 2015,
<https://www.rfc-editor.org/info/rfc7554>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/info/rfc7641>.
[RFC7731] Hui, J. and R. Kelsey, "Multicast Protocol for Low-Power
and Lossy Networks (MPL)", RFC 7731, DOI 10.17487/RFC7731,
February 2016, <https://www.rfc-editor.org/info/rfc7731>.
Appendix A. Extra text
The following text is from previous versions of this document. The
document has been re-organized to match the flow of
[I-D.ietf-anima-bootstrapping-keyinfra].
A.1. Assumptions
A.1.1. One-Touch Assumptions
This document interacts with the one-touch solution described in
[I-D.ietf-6tisch-minimal-security].
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A.1.2. Factory provided credentials (if any)
When a manufacturer installed certificate is provided as the IDevID,
it SHOULD contain a number of fields.
[I-D.ietf-anima-bootstrapping-keyinfra] provides a detailed set of
requirements.
A manufacturer unique serial number MUST be provided in the
serialNumber SubjectAltName extension, and MAY be repeated in the
Common Name. There are no sequential or numeric requirements on the
serialNumber, it may be any unique value that the manufacturer wants
to use. The serialNumber SHOULD be printed on the packaging and/or
on the device in a discrete way so that failures can be physically
traced to the relevant device.
A.1.3. Credentials to be introduced
The goal of the bootstrap process is to introduce one or more new
locally relevant credentials:
1. a certificate signed by a local certificate authority/registrar.
This is the LDevID of [ieee802-1AR].
2. alternatively, a network-wide key to be used to secure L2
traffic.
3. alternatively, a network-wide key to be used to authenticate per-
peer keying of L2 traffic using a mechanism such as provided by
[ieee802159].
A.2. Network Assumptions
This document is about enrollment of constrained devices [RFC7228] to
a constrained network. Constrained networks is such as [ieee802154],
and in particular the time-slotted, channel hopping (tsch) mode,
feature low bandwidths, and limited opportunities to transmit. A key
feature of these networks is that receivers are only listening at
certain times.
A.2.1. Security above and below IP
802.15.4 networks have three kinds of layer-2 security:
o a network key that is shared with all nodes and is used for
unicast and multicast. The key may be used for privacy, and it
may be used in some cases for authentication only (in the case of
enhanced beacons).
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o a series of network keys that are shared (agreed to) between pairs
of nodes (the per-peer key)
o a network key that is shared with all nodes (through a group key
management system), and is used for multicast traffic only, while
a per-pair key is used for unicast traffic
Setting up the credentials to bootstrap one of these kinds of
security, (or directly configuring the key itself for the first case)
is required. This is the security below the IP layer.
Security is required above the IP layer: there are three aspects
which the credentials in the previous section are to be used.
o to provide for secure connection with a Path Computation Element
[RFC4655], or other LLC (see ({RFC7554}} section 3).
o to initiate a connection between a Resource Server (RS) and an
application layer Authorization Server (AS and CAS from
[I-D.ietf-ace-actors]).
A.2.1.1. Perfect Forward Secrecy
Perfert Forward Secrecy (PFS) is the property of a protocol such that
complete knowledge of the crypto state (for instance, via a memory
dump) at time X does not imply that data from a disjoint time Y can
also be recovered. ([PFS]).
PFS is important for two reasons: one is that it offers protection
against the compromise of a node. It does this by changing the keys
in a non-deterministic way. This second property also makes it much
easier to remove a node from the network, as any node which has not
participated in the key changing process will find itself no longer
connected.
A.2.2. Join network assumptions
The network which the new pledge will connect to will have to have
the following properties:
o a known PANID. The PANID 0xXXXX where XXXX is the assigned RFC#
for this document is suggested.
o a minimal schedule with some Aloha time. This is usually in the
same slotframe as the Enhanced Beacon, but a pledge MUST listen
for an unencrypted Enhanced Beacon to so that it can synchronize.
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A.2.3. Number and cost of round trips
TBD.
A.2.4. Size of packets, number of fragments
TBD
A.3. Target end-state for join process
At the end of the zero-touch join process there will be a symmetric
key protected channel between the Join Registrar/Coordinator and the
pledge, now known as a Joined Node. This channel may be rekeyed via
new exchange of asymmetric exponents (ECDH for instance),
authenticated using the domain specific credentials created during
the join process.
This channel is in the form of an OSCOAP protected connection with
[I-D.ietf-core-comi] encoded objects. This document includes
definition of a [I-D.ietf-netconf-keystore] compatible objects for
encoding of the relevant [I-D.ietf-anima-bootstrapping-keyinfra]
objects.
Appendix B. Join Protocol
The pledge join protocol state machine is described in
[I-D.ietf-6tisch-minimal-security], in section XYZ. The pledge
recognizes that it is in zero-touch configuration by the following
situation:
o no PSK has been configured for the network in which it has joined.
o the pledge has no locally defined certificate (no LDevID), only an
IDevID.
o the network asserts an identity that the pledge does not
recognize.
All of these conditions MUST be true. If any of these are not true,
then the pledge has either been connected to the wrong network, or it
has already been bootstrapped into a different network, and it should
wait until it finds that network.
The zero-touch process consists of three stages:
1. the key agreement process
2. the provisional enrollment process
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3. the key distribution process
B.1. Key Agreement process
The key agreement process is identical to
[I-D.ietf-6tisch-minimal-security]. The process uses EDHOC with
certificates.
The pledge will have to trust the JRC provisionally, as described in
[I-D.ietf-anima-bootstrapping-keyinfra], section 3.1.2, and in
section 4.1.1 of [RFC7030].
The JRC will be able to validate the IDevID of the pledge using the
manufacturer's CA.
The pledge may not know if it is in a zero-touch or one-touch
situation: the pledge may be able to verify the JRC based upon trust
anchors that were installed at manufacturing time. In that case, the
pledge runs the simplified one-touch process.
The pledge signals in the EDHOC message_2 if it has accepted the JRC
certificate. The JRC will in general, not trust the pledge with the
network keys until it has provided the pledge with a voucher. The
pledge will notice the absence of the provisioning keys.
XXX - there could be some disconnect here. May need additional
signals here.
B.2. Provisional Enrollment process
When the pledge determines that it can not verify the certificate of
the JRC using built-in trust anchors, then it enters a provisional
state. In this state, it keeps the channel created by EDHOC open.
A new EDHOC key derivation is done by the JRC and pledge using a new
label, "6tisch-provisional".
The pledge runs as a passive CoMI server, leaving the JRC to drive
the enrollment process. The JRC can interrogate the pledge in a
variety of fashions as shown below: the process terminates when the
JRC provides the pledge with an ownership voucher and the pledge
leaves the provisional state.
A typical interaction involves the following requests:
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+-----------+ +----------+ +-----------+ +----------+
| | | | | Circuit | | New |
| Vendor | | Registrar| | Proxy | | Entity |
| (MASA) | | | | | | |
++----------+ +--+-------+ +-----------+ +----------+
| | GET request voucher |
| |-------------------------------->
| <----------voucher-token---------|
|/requestvoucher| |
<---------------+ |
+---------------> |
|/requestlog | |
<---------------+ |
+---------------> |
| | POST voucher |
| |-------------------------------->
| <------------2.05 OK ------------+
| | |
| | POST csr attributes |
| |-------------------------------->
| <------------2.05 OK ------------+
| | |
| | GET cert request |
| |-------------------------------->
| ???? <------------2.05 OK ------------+
|<--------------| CSR |
|-------------->| |
| | POST certificate |
| |-------------------------------->
| <------------2.05 OK ------------+
| | |
Appendix C. IANA Considerations
This document allocates one value from the subregistry "Address
Registration Option Status Values": ND_NS_JOIN_DECLINED Join
Assistant, JOIN DECLINED (TBD-AA)
Appendix D. Protocol Definition
D.1. Discovery
Only IPv6 operations using Link-Local addresses are supported. Use
of a temporary address is NOT encouraged as the critial resource on
the Proxy device is the number of Neighbour Cache Entries that can be
used for untrusted pledge entries.
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D.1.1. Proxy Discovery Protocol Details
The Proxy is discovered using the enhanced beacon defined in
[I-D.richardson-6tisch-join-enhanced-beacon].
D.1.2. Registrar Discovery Protocol Details
The Registrar is not discovered by the Proxy. Any device that is
expected to be able to operate as a Registrar MAY be told the address
of the Registrar when that device joins the network. The address MAY
be included in the [I-D.ietf-6tisch-minimal-security] Join Response.
If the address is NOT included, then Proxy may assume that the
Registrar can be found at the DODAG root, which is well known in the
6tisch's use of the RPL protocol.
Author's Address
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
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