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ANIMA WG M. Pritikin
Internet-Draft Cisco
Intended status: Informational M. Richardson
Expires: August 25, 2016 SSW
M. Behringer
S. Bjarnason
Cisco
February 22, 2016
Bootstrapping Key Infrastructures
draft-ietf-anima-bootstrapping-keyinfra-01
Abstract
This document specifies automated bootstrapping of an key
infrastructure using vendor installed IEEE 802.1AR manufacturing
installed certificates, in combination with a vendor based service on
the Internet. Before being authenticated, a new device has only
link-local connectivity, and does not require a routable address.
When a vendor provides an Internet based service, devices can be
forced to join only specific domains but in limited/disconnected
networks or legacy environments we describe a variety of options that
allow bootstrapping to proceed.
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 http://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 August 25, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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 . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Scope of solution . . . . . . . . . . . . . . . . . . . . 5
1.3. Trust bootstrap . . . . . . . . . . . . . . . . . . . . . 6
2. Architectural Overview . . . . . . . . . . . . . . . . . . . 6
3. Functional Overview . . . . . . . . . . . . . . . . . . . . . 8
3.1. Behavior of a new entity . . . . . . . . . . . . . . . . 10
3.1.1. Discovery . . . . . . . . . . . . . . . . . . . . . . 12
3.1.2. Identity . . . . . . . . . . . . . . . . . . . . . . 13
3.1.3. Request Join . . . . . . . . . . . . . . . . . . . . 13
3.1.4. Imprint . . . . . . . . . . . . . . . . . . . . . . . 14
3.1.5. Enrollment . . . . . . . . . . . . . . . . . . . . . 15
3.1.6. Being Managed . . . . . . . . . . . . . . . . . . . . 15
3.2. Behavior of a proxy . . . . . . . . . . . . . . . . . . . 16
3.3. Behavior of the Registrar (Bootstrap Server) . . . . . . 16
3.3.1. Entity Authentication . . . . . . . . . . . . . . . . 17
3.3.2. Entity Authorization . . . . . . . . . . . . . . . . 17
3.3.3. Claiming the New Entity . . . . . . . . . . . . . . . 18
3.3.4. Log Verification . . . . . . . . . . . . . . . . . . 19
3.3.5. Forwarding Audit Token plus Configuration . . . . . . 19
3.4. Behavior of the MASA Service . . . . . . . . . . . . . . 20
3.4.1. Issue Authorization Token and Log the event . . . . . 20
3.4.2. Retrieve Audit Entries from Log . . . . . . . . . . . 20
3.5. Leveraging the new key infrastructure / next steps . . . 21
3.5.1. Network boundaries . . . . . . . . . . . . . . . . . 21
3.6. Interactions with Network Access Control . . . . . . . . 21
4. Domain Operator Activities . . . . . . . . . . . . . . . . . 21
4.1. Instantiating the Domain Certification Authority . . . . 22
4.2. Instantiating the Registrar . . . . . . . . . . . . . . . 22
4.3. Accepting New Entities . . . . . . . . . . . . . . . . . 22
4.4. Automatic Enrollment of Devices . . . . . . . . . . . . . 23
4.5. Secure Network Operations . . . . . . . . . . . . . . . . 23
5. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 24
5.1. Request Audit Token . . . . . . . . . . . . . . . . . . . 26
5.2. Request Audit Token from MASA . . . . . . . . . . . . . . 27
5.3. Basic Configuration Information Package . . . . . . . . . 29
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5.4. Request MASA authorization log . . . . . . . . . . . . . 29
6. Reduced security operational modes . . . . . . . . . . . . . 30
6.1. New Entity security reductions . . . . . . . . . . . . . 30
6.2. Registrar security reductions . . . . . . . . . . . . . . 30
6.3. MASA security reductions . . . . . . . . . . . . . . . . 31
7. Security Considerations . . . . . . . . . . . . . . . . . . . 31
7.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 33
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 33
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 33
9.1. Normative References . . . . . . . . . . . . . . . . . . 33
9.2. Informative References . . . . . . . . . . . . . . . . . 33
Appendix A. Editor notes . . . . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction
To literally "pull yourself up by the bootstraps" is an impossible
action. Similarly the secure establishment of a key infrastructure
without external help is also an impossibility. Today it is accepted
that the initial connections between nodes are insecure, until key
distribution is complete, or that domain-specific keying material is
pre-provisioned on each new device in a costly and non-scalable
manner. This document describes a zero-touch approach to
bootstrapping an entity by securing the initial distribution of key
material using third-party generic keying material, such as a
manufacturer installed IEEE 802.1AR certificate [IDevID], and a
corresponding third-party service on the Internet.
The two sides of an association being bootstrapped authenticate each
other and then determine appropriate authorization. This process is
described as four distinct steps between the existing domain and the
new entity being added:
o New entity authentication: "Who is this? What is its identity?"
o New entity authorization: "Is it mine? Do I want it? What are
the chances it has been compromised?"
o Domain authentication: "What is this domain's claimed identity?"
o Domain authorization: "Should I join it?"
A precise answer to these questions can not be obtained without
leveraging some established key infrastructure(s). A complexity that
this protocol deals with are dealing with devices from a variety of
vendors, and a network infrastructure (the domain) that is operated
by parties that do not have any priveledged relationship with the
device vendors. The domain's decisions are based on the new entity's
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authenticated identity, as established by verification of previously
installed credentials such as a manufacturer installed IEEE 802.1AR
certificate, and verified back-end information such as a configured
list of purchased devices or communication with a (unidirectionally)
trusted third-party. The new entity's decisions are made according
to verified communication with a trusted third-party or in a strictly
auditable fasion.
Optimal security is achieved with IEEE 802.1AR certificates on each
new entity, accompanied by a third-party Internet based service for
verification. Bootstrapping concepts run to completion with less
requirements, but are then less secure. A domain can choose to
accept lower levels of security when a trusted third-party is not
available so that bootstrapping proceeds even at the risk of reduced
security. Only the domain can make these decisions based on
administrative input and known behavior of the new entity.
The result of bootstrapping is that a domain specific key
infrastructure is deployed. Since IEEE 802.1AR PKI certificates are
used for identifying the new entity, and the public key of the domain
identity is leveraged during communiciations with an Internet based
service, which is itself authenticated using HTTPS, bootstrapping of
a domain specific Public Key Infrastructure (PKI) is described.
Sufficient agility to support bootstrapping alternative key
infrastructures (such as symmetric key solutions) is considered
although no such alternate key infrastructure is described.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
The following terms are defined for clarity:
DomainID: The domain identity is the 160-bit SHA-1 hash of the BIT
STRING of the subjectPublicKey of the domain trust anchor that is
stored by the Domain CA. This is consistent with the RFC5280
Certification Authority subject key identifier of the Domain CA's
self signed root certificate. (A string value bound to the Domain
CA's self signed root certificate subject and issuer fields is
often colloquially used as a humanized identity value but during
protocol discussions the more exact term as defined here is used).
drop ship: The physical distribution of equipment containing the
"factory default" configuration to a final destination. In zero-
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touch scenarios there is no staging or pre-configuration during
drop-ship.
imprint: the process where a device that wishes to join a network
acquires it's domain specific identity. This term is taken from
Konrad Lorenz's work in biology with new ducklings: during a
critical period, the duckling would assume that anything that
looks like a mother duck is in fact their mother. [imprinting].
The word "enrollment" is sometimes used when more appropriate.
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. This
is definition 6, according to [pledge]
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.
1.2. Scope of solution
Questions have been posed as to whether this solution is suitable in
general for Internet of Things (IoT) networks. In general the answer
is no, but the terminology of [RFC7228] is best used to describe the
boundaries.
The entire solution described in this document is aimed in general at
non-constrained (i.e. class 2+) devices operating on a non-Challenged
network. The entire solution described here is not intended to be
useable as-is by constrained devices operating on challenged networks
(such as 802.15.4 LLNs).
In many target applications, the systems involved are large router
platforms with multi-gigabit inter-connections, mounted in controlled
access data centers. But this solution is not exclusive to the
large, it is intended to scale to thousands of devices located in
hostile environments, such as ISP provided CPE devices which are
drop-shipped to the end user. The situation where an order is
fulfilled from distributed warehouse from a common stock and shipped
directly to the target location at the request of the domain owner is
explicitely supported. That stock ("SKU") could be provided to a
number of potential domain owners, and the eventual domain owner will
not know a-priori which device will go to which location.
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Specifically, there are protocol aspects described here which might
result in congestion collapse or energy-exhaustion of intermediate
battery powered routers in an LLN. Those types of networks SHOULD
NOT use this solution.
The imprint protocol described here could, however, be used by non-
energy constrained devices joining a non-constrained network (for
instance, smart light bulbs are usually mains powered, and speak
802.11). It could also be used by non-constrained devices across a
non-energy constrained, but challenged network (such as 802.15.4).
Some aspects are in scope for constrained devices on challenged
networks: the certificate contents, and the process by which the four
questions above are resolved is in scope. It is simply the actual
on-the-wire imprint protocol which is likely inappropriate.
1.3. Trust bootstrap
The imprint protocol results in a secure relationship between the
domain registrar and the new device. If the new device is
sufficiently constrained that the ACE protocol should be leveraged
for operation, (see [I-D.ietf-ace-actors]), and the domain registrar
is also the Client Authorization Server or the Authorization Server,
then it may be appropriate to use this secure channel to exchange ACE
tokens.
2. Architectural Overview
The logical elements of the bootstrapping framework are described in
this section. Figure 1 provides a simplified overview of the
components. Each component is logical and may be combined with other
components as necessary.
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.
.+------------------------+
+--------------Drop Ship-------------->.| Vendor Service |
| .+------------------------+
| .| M anufacturer| |
| .| A uthorized |Ownership|
| .| S igning |Tracker |
| .| A uthority | |
| .+--------------+---------+
| .............. ^
V |
+-------+ ............................................|...
| | . | .
| | . +------------+ +-----------+ | .
| | . | | | | | .
| <---L2---> | | <-------+ .
| | or | Proxy | | Registrar | .
| <---L3---> <---L3--> | .
| New | . | | | | .
| Entity| . +------------+ +-----+-----+ .
| | . | .
| | . +-----------------+----------+ .
| | . | Domain Certification | .
| | . | Authority | .
+-------+ . | Management and etc | .
. +----------------------------+ .
. .
................................................
"Domain" components
Figure 1
Domain: The set of entities that trust a common key infrastructure
trust anchor. This includes the Proxy, Registrar, Domain
Certificate Authority, Management components and any existing
entity that is already a member of the domain.
Domain CA: The domain Certification Authority (CA) provides
certification functionalities to the domain. At a minimum it
provides certification functionalities to the Registrar and stores
the trust anchor that defines the domain. Optionally, it
certifies all elements.
Registrar: A representative of the domain that is configured,
perhaps autonomically, to decide whether a new device is allowed
to join the domain. The administrator of the domain interfaces
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with a Registrar to control this process. Typically a Registrar
is "inside" its domain.
New Entity: A new device or virtual machine or software component
that is not yet part of the domain.
Proxy: A domain entity that helps the New Entity join the domain. A
Proxy facilitates communication for devices that find themselves
in an environment where they are not provided connectivity until
after they are validated as members of the domain. The New Entity
is unaware that they are communicating with a proxy rather than
directly with the Registrar.
MASA Service: A Manufacturer Authorized Signing Authority (MASA)
service on the global Internet. The MASA provides a trusted
repository for audit log information concerning privacy protected
bootstrapping events.
Ownership Tracker An Ownership Tracker service on the global
internet. The Ownership Tracker uses business processes to
accurately track ownership of all devices shipped against domains
that have purchased them. Although optional this component allows
vendors to provide additional value in cases where their sales and
distribution channels allow for accurately tracking of such
ownership.
We assume a multi-vendor network. In such an environment there could
be a MASA or Ownership Tracker for each vendor that supports devices
following this document's specification, or an integrator could
provide a MASA service for all devices. It is unlikely that an
integrator could provide Ownership Tracking services for multiple
vendors.
This document describes a secure zero-touch approach to bootstrapping
a key infrastructure; if certain devices in a network do not support
this approach, they can still be bootstrapped manually. Although
manual deployment is not scalable and is not a focus of this document
the necessary mechanisms are called out in this document to ensure
such edge conditions are covered by the architectural and protocol
models.
3. Functional Overview
Entities behave in an autonomic fashion. They discover each other
and autonomically bootstrap into a key infrastructure deliminating
the autonomic domain. See
[I-D.irtf-nmrg-autonomic-network-definitions] for more information.
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This section details the state machine and operational flow for each
of the main three entities. The New Entity, the Domain (primarily
the Registrar) and the MASA service.
The overall flow is shown in Figure 2:
+---------+ +----------+ +-----------+
| New | Proxy | | | Vendor |
| Entity | not | Domain | | Service |
| | shown | | | (Internet)|
+---------+ +----------+ +-----------+
| | |
|<-------discovery--------->| |
|---IEEE 802.1AR identity-->| |
| | |
| [accept device?] |
| | |
| |---IEEE 802.1AR identity--->|
| |---Domain ID--------------->|
| | |
| | [optional: does
| | the device belong
| | to the domain?]
| | |
| | [update audit log]
| | |
| |<---device audit log--------|
| |<---audit token-------------|
| |<-- ownership voucher-------|
| | (optional) |
| | |
| [ still accept device?] |
| | |
|<----audit token-----------| |
|<----ownership voucher-----| (optional) |
|<----config information----| |
| | |
[audit token valid?] | |
[or ownership voucher valid?] | |
[apply config information] | |
| | |
|----domain enrollment----->| |
|<----domain certificate----| |
| | |
Figure 2
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3.1. Behavior of a new entity
A New Entity that has not yet been bootstrapped attempts to find a
local domain and join it.
States of a New Entity are as follows:
+--------------+
| Start |
| |
+------+-------+
|
+------v-------+
| Discover |
+------------> |
| +------+-------+
| |
| +------v-------+
| | Identity |
^------------+ |
| rejected +------+-------+
| |
| +------v-------+
| | Request |
| | Join |
| +------+-------+
| |
| +------v-------+
| | Imprint | Optional
^------------+ <--+Manual input
| Bad Vendor +------+-------+
| response |
| +------v-------+
| | Enroll |
^------------+ |
| Enroll +------+-------+
| Failure |
| +------v-------+
| | Being |
^------------+ Managed |
Factory +--------------+
reset
Figure 3
State descriptions are as follows:
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1. Discover a communication channel to the "closest" Registrar by
trying the following steps in this order:
A. Search for a Proxy on the local link using a link local
discovery protocol (no routable addresses are required for
this approach). If multiple local proxies are discovered
attempt communications with each before widening the search
to other options. The proxy relays information to the
registrar. If this fails:
B. Obtain an IP address using existing methods, such as SLAAC or
DHCPv6, and search for a local registrar using DNS service
discovery. [[EDNOTE: ]]If this fails:
C. Obtain an IP address (as above), and search for the domain
registrar using a pre-defined Factory provided Internet based
re-direct service. Various methods could be used, such as
DNS or RESTful APIs.
2. Identify itself. This is done by presenting an IEEE 802.1AR
credentials to the discovered Registrar (via a Proxy if
necessary). Included is a generated nonce that is specific to
this attempt.
3. Requests to Join the Discovered domain. The device indicates the
Imprint methods it will accept and provides a nonce ensuring that
any responses can be associated with this particular
bootstrapping attempt.
4. Imprint on the Registrar. This requires verification of the MASA
service generated Audit Token as provided by the contacted
Registrar or the validation of the vendor provided ownership
voucher. The Audit Token contains the DomainID information for
this device and is signed by the MASA service. The device uses a
pre-installed root certificate of the MASA service to validate
the signature of the Audit Token or the Ownership Voucher.
5. Enroll by accepting the domain specific information from the
Registrar, and by obtaining a domain certificate from the
Registrar using a standard enrollment protocol, e.g. Enrolment
over Secure Transport (EST) [RFC7030].
6. The New Entity 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.
The following sections describe each of these steps in more detail.
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3.1.1. Discovery
Existing protocols provide the functionality for discovery of the
Domain Bootstrap Server. The result of discovery might be
communication with a proxy instead of a Domain Bootstrap Server. In
such a case the proxy facilitates communication with the actual
Domain Bootstrap Server in a manner that is transparent to the New
Entity.
To discover the Domain Bootstrap Server the New Entity performs the
following actions in this order:
1. MUST: Obtains a local address using either IPv4 or IPv6 methods
as described in [[EDNOTE: do we need a reference?]].
2. MUST: Attempt to establish a TLS connection to the next hop
neighbor at a well known AN port building on the [[EDNOTE: AN
node discovery discussion, need a reference??]]. [Toerless to
provide updated text]
3. MUST: unsecured-GRASP as a link local discovery method?
[Toerless to provide updated text]
4. MAY: Performs DNS-based Service Discovery [RFC6763] over
Multicast DNS [RFC6762] searching for the service
"_bootstrapks._tcp.local."
5. MAY: Performs DNS-based Service Discovery [RFC6763] over normal
DNS operations. In this case the domain is known so the service
searched for is "_bootstrapks._tcp.example.com".
6. MAY: If no local bootstrapks service is located using the DNS-
based Sevice Discovery methods the New Entity contacts a well
known vendor provided bootstrapping server by perfoming a DNS
lookup using a well known URI such as "bootstrapks.vendor-
example.com".
Once a domain bootstrapping server is discovered the New Entity
communicates with the discovered server using the bootstrapping
protocol defined in Section 5. The current DNS services returned
during each query is maintained until bootstrapping is completed. If
bootstrapping fails and the New Entity returns to the Discovery state
it picks up where it left off and continues attempting bootstrapping.
For example if the first Multicast DNS _bootstrapks._tcp.local
response doens't work then the second and third responses are tried.
If these fail the New Entity moves on to normal DNS-based Service
Discovery.
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Once all discovered services are attempted the device SHOULD return
to Multicast DNS and keep trying. The New Entity may prioritize
selection order as appropriate for the anticipated environment.
[[EDNOTE: An appropriate backoff or rate limiting strategy should be
defined here such that the device doesn't flood the local network
with queries. If the device were to eventually give up -- or at
least have too long between attempts -- a power cycle would restart
the backoff mechanism.]]
[[EDNOTE: it is unclear yet if discovery happens on a per interface
basis or once per device. What is the requirement around joining
multiple domains; is this a bootstrapping requirement or is this a
broader autonomic requirement]] [[EDNOTE: b. carpenter: I seem to
think we settled on joining one domain (which might be a sub-domain)
and then doing some sort of cross-certification to get authenticated
and authorized in another domain. If so, it isn't a bootstrap
requirement.]]
3.1.2. Identity
The New Entity identifies itself during the communication protocol
handshake. If the client identity is rejected the New Entity repeats
the Discovery process using the next proxy or discovery method
available.
The boostrapping protocol server is as of yet not validated. Thus
this connection is provisional and all data recieved is untrusted
until sufficiently validated even though it is over a (D)TLS
connection. This is aligned with the existing provisional mode of
EST [RFC7030] during s4.1.1 "Bootstrap Distribution of CA
Certificates".
All security associations established are between the new device and
the Bootstrapping server regardless of proxy operations.
3.1.3. Request Join
The New Entity POSTs a request to join the domain to the
Bootstrapping server. This request contains a New Entity generated
nonce and informs the Bootstrapping server which imprint methods the
New Entity will accept.
As indicated in EST [RFC7030] the bootstrapping server MAY redirect
the client to an alternate server. This is most useful in the case
where the New Entity has resorted to a well known vendor URI and is
communicating with the vendor's Registrar directly. In this case the
New Entity has authenticated the Registrar using the local Implicit
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Trust Anchor database and can therefore treat the redirect URI as a
trusted URI which can also be validated using the Implicit Trust
Anchor database. Since client authentication occurs during the TLS
handshake the bootstrapping server has sufficient information to
apply appropriate policy concerning which server to redirect to.
The nonce ensures the New Entity can verify that responses are
specific to this bootstrapping attempt. This minimizes the use of
global time and provides a substantial benefit for devices without a
valid clock.
3.1.4. Imprint
The domain trust anchor is received by the New Entity during the
boostrapping protocol methods in the form of either an Audit Token
containing the domainID or an explicit ownership voucher. The goal
of the imprint state is to securely obtain a copy of this trust
anchor without involving human interaction.
The enrollment protocol EST [RFC7030] details a set of non-autonomic
bootstrapping methods such as:
o using the Implicit Trust Anchor database (not an autonomic
solution because the URL must be securely distributed),
o engaging a human user to authorize the CA certificate using out-
of-band data (not an autonomic solution because the human user is
involved),
o using a configured Explicit TA database (not an autonomic solution
because the distribution of an explicit TA database is not
autonomic),
o and using a Certificate-Less TLS mutual authentication method (not
an autonomic solution because the distribution of symmetric key
material is not autonomic).
This document describes additional autonomic methods:
MASA audit token Audit tokens are obtained by the Registrar from the
MASA service and presented to the New Entity for validation.
These indicate to the New Entity that joining the domain has been
logged by a trusted logging server.
Ownership Voucher Ownership Vouchers are obtained by the Registrar
from the MASA service and explicitly indicate the fully qualified
domain name of the domain the new entity currently belongs to.
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Since client authentication occurs during the TLS handshake the
bootstrapping server has sufficient information to apply appropriate
policy concerning which method to use.
An arbitrary basic configuration information package that is signed
by the domain can be delivered alongside the Audit Token or ownership
validation. This information is signed by the domain private keys
and is a one time delivery containing information such as which
enrollment server to communicate with and which management system to
communicate with. It is intended as a limited basic configuration
for these purposes and is not intended to deliver entire final
configuration to the device.
If the autonomic methods fail the New Entity returns to discovery
state and attempts bootstrapping with the next available discovered
Registrar.
3.1.5. Enrollment
As the final step of bootstrapping a Registrar helps to issue a
domain specific credential to the New Entity. For simplicity in this
document, a Registrar primarily facilitates issuing a credential by
acting as an RFC5280 Registration Authority for the Domain
Certification Authority.
Enrollment proceeds as described in Enrollment over Secure Transport
(EST) [RFC7030]. The New Entity contacts the Registrar using EST as
indicated:
o The New Entity is authenticated using the IEEE 802.1AR
credentials.
o The EST section 4.1.3 CA Certificates Response is verified using
either the Audit Token which provided the domain identity -or-
o The EST server is authenticated by using the Owership Voucher
indicated fully qualified domain name to build the EST URI such
that EST section 4.1.1 bootstrapping using the New Entity implicit
Trust Anchor database can be used.
3.1.6. Being Managed
Functionality to provide generic "configuration" information is
supported. The parsing of this data and any subsequent use of the
data, for example communications with a Network Management System is
out of scope but is expected to occur after bootstrapping enrollment
is complete. This ensures that all communications with management
systems which can divulge local security information (e.g. network
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topology or raw key material) is secured using the local credentials
issued during enrollment.
See Section 3.5.
3.2. Behavior of a proxy
The role of the Proxy is to facilitate communications. The Proxy
forwards EST transport (TLS or DTLS) packets between the New Entity
and the Registrar that has been configured on the Proxy.
[[EDNOTE: To what extent do we need to explain how this occurs? It
is sufficient to indicate the basic behavior or do we need to
indicate here all the details? A rough implementation of an ipv4
proxy would be as follows:
socat -v tcp4-listen:443,reuseaddr,fork tcp4:registrar.example.com:443
There have been suggestions that a stateless proxy implementation
using a DTLS extension would be preferred. Is this a future
optimization opportunity or a short term requirement?]]
3.3. Behavior of the Registrar (Bootstrap Server)
Once a Registrar is established it listens for new entities and
determines if they can join the domain. The registrar delivers any
necessary authorization information to the new device and facilitates
enrollment with the domain PKI.
Registrar behavior is as follows:
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Contacted by New Entity
+
|
+-------v----------+
| Entity | fail?
| Authentication +---------+
+-------+----------+ |
| |
+-------v----------+ |
| Entity | fail? |
| Authorization +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Claiming the | fail? |
| Entity +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Log Verification | fail? |
| +--------->
+-------+----------+ |
| |
+-------v----------+ +----v-------+
| Forward | | |
| Audit | | Reject |
| token + config | | Device |
| to the Entity | | |
+------------------+ +------------+
Figure 4
3.3.1. Entity Authentication
The applicable authentication methods detailed in EST [RFC7030] are:
o the use of an IEEE 802.1AR IDevID credential,
o or the use of a secret that is transmitted out of band between the
New Entity and the Registrar (this use case is not autonomic).
3.3.2. Entity Authorization
In a fully automated network all devices must be securely identified
and authorized to join the domain.
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A Registrar accepts or declines a request to join the domain, based
on the authenticated identity presented. Automated acceptance
criteria include:
o allow any device of a specific type (as determined by the IEEE
802.1AR device identity),
o allow any device from a specific vendor (as determined by the IEEE
802.1AR identity),
o allow a specific device from a vendor (as determined by the IEEE
802.1AR identity)
Since all New Entities accept Audit Tokens the Registrar MUST use the
vendor provided MASA service to verify that the device's history log
does not include unexpected Registrars. If a device had previously
registered with another domain, the Registrar of that domain would
show in the log.
In order to validate the IEEE 802.1AR device identity the Registrar
maintains a database of vendor trust anchors (e.g. vendor root
certificates or keyIdentifiers for vendor root public keys). For
user interface purposes this database can be mapped to colloquial
vendor names. Registrars can be shipped with the trust anchors of a
significant number of third-party vendors within the target market.
If a device is accepted into the domain, it is expected request a
domain certificate through a certificate enrolment process. The
result is a common trust anchor and device certificates for all
autonomic devices in a domain (these certificates can subsequently be
used to determine the boundaries of the homenet, to authenticate
other domain nodes, and to autonomically enable services on the
homenet). The authorization performed during this phase MAY be
cached for the TLS session and applied to subsequent EST enrollment
requests so long as the session lasts.
3.3.3. Claiming the New Entity
Claiming an entity establishes an audit log at the MASA server and
provides the Registrar with proof, in the form of a MASA
authorization token, that the log entry has been inserted. As
indicated in Section 3.1.4 a New Entity will only proceed with
bootstrapping if a validated MASA authorization token has been
recieved. The New Entity therefore enforces that bootstrapping only