Network Working Group M. Pritikin
Internet-Draft M. Behringer
Intended status: Informational S. Bjarnason
Expires: July 19, 2014 Cisco
January 15, 2014
Bootstrapping Key Infrastructures
draft-pritikin-bootstrapping-keyinfrastructures-00
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 cloud
service. Before being authenticated, a new device has only link-
local connectivity, and does not require a routable address. When a
vendor cloud service is provided devices can be forced to join only
specific domains but for contrained environments we describe a
variety of options that allow bootstrapping to proceed.
Status of this Memo
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on July 19, 2014.
Copyright Notice
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Architectural Overview . . . . . . . . . . . . . . . . . . . . 4
3. Operational Overview . . . . . . . . . . . . . . . . . . . . . 7
3.1. Instantiating the Domain Certification Authority . . . . . 7
3.2. Instantiating the Registrar . . . . . . . . . . . . . . . 7
3.3. Accepting New Entities . . . . . . . . . . . . . . . . . . 7
3.4. Operating the Network . . . . . . . . . . . . . . . . . . 8
4. Functional Overview . . . . . . . . . . . . . . . . . . . . . 8
4.1. Behavior of a new entity . . . . . . . . . . . . . . . . . 9
4.1.1. Proxy Discovery . . . . . . . . . . . . . . . . . . . 9
4.1.2. Receiving and accepting the Domain Identity . . . . . 10
4.1.3. Enrollment . . . . . . . . . . . . . . . . . . . . . . 11
4.1.4. After Enrollment . . . . . . . . . . . . . . . . . . . 11
4.2. Behavior of a proxy . . . . . . . . . . . . . . . . . . . 12
4.3. Behavior of the Registrar . . . . . . . . . . . . . . . . 12
4.3.1. Authenticating the Device . . . . . . . . . . . . . . 12
4.3.2. Accepting the Entity . . . . . . . . . . . . . . . . . 12
4.3.3. Claiming the new entity . . . . . . . . . . . . . . . 13
4.4. Behavior of the MASA Cloud Service . . . . . . . . . . . . 13
4.4.1. Issue Authorization Token and Log the event . . . . . 13
4.4.2. Retrieve Audit Entries from Log . . . . . . . . . . . 14
4.5. Leveraging the new key infrastructure / next steps . . . . 14
4.5.1. Network boundaries . . . . . . . . . . . . . . . . . . 14
5. Protocol Details . . . . . . . . . . . . . . . . . . . . . . . 14
5.1. EAP-EST . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2. Request bootstrap token . . . . . . . . . . . . . . . . . 15
5.3. Request MASA authorization token . . . . . . . . . . . . . 16
5.4. Request MASA authorization log . . . . . . . . . . . . . . 16
6. Reduced security operational modes . . . . . . . . . . . . . . 17
7. Security Considerations . . . . . . . . . . . . . . . . . . . 17
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
8.1. Normative References . . . . . . . . . . . . . . . . . . . 18
8.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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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 cloud service.
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 an established key infrastructure(s). The domain's
decisions are based on the new entity's 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 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 cloud service for
verification. The concept also works with less requirements, but is
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 a cloud service,
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which is itself authenticated using HTTPS, bootstrapping of a domain
specific Public Key Infrastructure (PKI) is fully described.
Sufficient agility to support bootstrapping alternative key
infrastructures (such as symmetric key solutions) is considered
although no such 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:
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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Factory components
.
. +------------+
. | Factory CA |
. +------------+
. |
. +------------+
. | |
+--------------(provides)---------------------------| Factory |
| +---------->| |
| | . +------------+
| V .
| +---------------+ . +------------+
| | Orchestrator | . | MASA |
V +---------------+ . | Cloud |
+-------+ | . | Service |
| New | +------------+ +-----------+ . +------------+
| Entity|<--L2-->| Proxy |<----->| | ....... ^
| | +------------+ | | |
| | | Registrar | |
| | | | |
| |<--DHCP-->(L3 bootstrap) | | |
| | | | |
| |<-----L3---------------------( registrar )-----------+
| | ( may proxy ) |
+-------+ +-----------+
|
+----------------------------+
^ | Domain Certification | ^
. | Authority | .
. +----------------------------+ .
. .
.........................................
|
"domain" components
Figure 1
Domain: The set of entities that trust a common key infrastructure
trust anchor.
Domain CA: The domain Certification Authority (CA) optionally
provides certification functionalities to the domain entities. At
a minimum it provides certification funtionalities to the
Registrar and stores the trust anchor that defines the domain.
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Domain Identity: 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 colloqually used as a humanized identity value but
during protocol discussions the more exact term as defined here is
used).
Orchestrator: Although bootstrapping of an individual device is
automated and requires zero administrative involvement
(particularly on the New Entity) the orchestrator drives general
operations of the domain. In simple deployments this might be a
single administrator ordering a new device from the Factory and
manually inputing a serial number from the bill-of-sale into a
Registrar. In a more complex environment this might be an
automated process that directs a hypervisor "Factory" to
instantiate a new virtual machine.
Factory: This instantiates the New Entity. For physical devices
this can be representative of third-party vendor manufacturing,
ordering and shipping process(es) that results in a physical
hardware device with an IEEE 802.1AR identity being drop shipped
to a destination domain for physical installation. In a virtual
machine environment this can be the virtual machine hypervisor
control software that initiates a virtual machine instance, in
which case the factory is a "virtual factory" and might be managed
by the domain itself.
Factory CA: This Certification Authority is leveraged by the Factory
to issue IEEE 802.1AR identities to each New Entity. For a
virtual factory it may be reasonable to assume the domain
certification authority is directly used but in a complex
environment it is assumed the Factory does not have direct access
to the Domain Certification Authority.
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
with a Registrar to control this process.
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 L3 connectivity
until after they are validated as members of the domain.
MASA Cloud Service: A Manufacturer Authorized Signing Authority
(MASA) cloud service on the global Internet. At a minimum the
MASA provides a trusted repository for audit information
concerning privacy protected bootstrapping events. As a service
offering the MASA can encorporate many of the bootstrapping
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elements (such as the Registrar and the Domain CA) into the cloud
service.
3. Operational Overview
This section describes how an operator interacts with a domain that
supports the bootstrapping as described in this document.
3.1. Instantiating the Domain Certification Authority
This is a one time step by the domain administrator. This is an "off
the shelf" CA with the exception that it is designed to work as an
integrated part of the security solution. This precludes the use of
3rd party certification authority services that do not provide
support for delegation of certificate issuance decisions to a domain
managed Registration Authority.
3.2. Instantiating the Registrar
This is a one time step by the domain administrator. One or more
devices in the domain are configured take on a Registrar function.
A device can be configured to act as a Registrar or a device can
auto-select itself to take on this function, using a detection
mechanism to resolve potential conflicts and setup communication with
the Domain Certification Authority. An automated Registrar selection
processes is not detailed here. [[EDNOTE: yet]]
3.3. Accepting New Entities
For each New Entity the Registrar is informed a priori the unique
identifier (e.g. serial number). This can be supplied automatically
from the Orchestrator [[EDNOTE: TBD]] or inputed manually by the
administrator.
For each entity that will be accepted a Registrar maintains the
Factory CA identity and the entity's unique identifier. The Factory
CA identity could be implemented as the Factory CA root certificate
keyIdentifier (the 160-bit SHA-1 hash of the value of the BIT STRING
subjectPublicKey). For user interface purposes the keyIdentifier
information can be mapped to a colloquial Factory name (Registrars
can be shipped with the keyIdentifier of a significant number of
third-party manufacturers).
Additional policy can be stored for future authorization decisions.
For example an expected deployment time window or that a certain
Proxy must be used.
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3.4. Operating the Network
Once devices are enrolled to the domain, the network operator can
specify a policy, or otherwise configure the devices if required.
This is outside scope for this document.
4. Functional Overview
Entities behave in an autonomic fashion. They discover each other
and autonomically establish a key infrastructure deliminating the
autonomic domain. See [I-D.behringer-autonomic-network-framework]
for more information.
The overall flow is shown in Figure 2:
+---------+ +----------+ +-----------+
| New | | | | Factory |
| Entity | | Domain | | Cloud |
| | | | | Service |
+---------+ +----------+ +-----------+
| | |
|<-------discovery--------->| |
|---802.1AR credential----->| |
| | |
| [ accept device? ] |
| | |
| |---802.1AR identity-------->|
| |---Domain ID--------------->|
| | |
| | [device belongs]
| | [to domain? ]
| | |
| | [update audit log]
| | |
| |<---device history log------|
| |<-- authorization token-----|
| | |
| [ still accept device?] |
| | |
|<----authorization token---| |
|<----domain information----| |
| | |
[auth token valid?] | |
| | |
|----domain enrolment------>| |
|<----domain certificate----| |
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| |
4.1. Behavior of a new entity
A New Entity that has not yet been bootstrapped attempts to find a
local domain and join it. A number of methods are attempted for
establishing communications with the domain in a specified order.
Client behavior is as follows:
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 Neighbor
Discovery. If multiple local proxies are discovered attempt
communications with each before widening the search to other
options. If this fails:
B. Obtain an IP address using DHCP, and search for a local
registrar using DNS service discovery. If this fails:
C. Obtain an IP address using DHCP, and search for a pre-defined
Factory provided global registrar using DNS.
2. Present 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. Verify the MASA cloud service generated authorization token as
provided by the contacted Registrar. The nonce information
previously provided is also checked, if it was not removed by the
Registrar.
4. If and only if step three is successful: Join Domain, by
accepting the domain specific information from the registrar, and
by enrolling a domain certificate from the registrar.
5. The New Entity is now a member of the domain and will only repeat
the discovery aspects of bootstrapping if it is returned to
factory default settings.
[[EDNOTE: Step (1b and 1c) is similar to the vendor DNS mechanisms
described in draft-kwatsen-netconf-zerotouch although the goal here
is to contact a Registrar rather than a vendor supplied NMS]
The following sections describe each of these steps in more detail.
4.1.1. Proxy Discovery
Existing protocols provide the appropriate functionality for both
discovering the Proxy and facilitating communication through the
Proxy:
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IEEE 802.1X Where the New Entity can be cast as the "supplicant" and
the Proxy is the "authenticator". The bootstrapping protocol
messages are encapsulated as EAP methods. The "authenticator"
reencapsulates the EAPOL frames and forwards them to the
"Authentication Server", which provides Registrar functionalities.
PANA [RFC5191] [[EDNOTE: TBD]]
ND [RFC2461] / [RFC4861] [[EDNOTE: TBD]] NOTE: Neighbor Discovery
protocols do not describe a mechanism for forwarding messages.
Each provides a method for the New Entity to discover and initiate
communication with a local neighbor. In each protocol methods are
available to support encapsulation of the bootstrapping protocol
messages described elsewhere in this document. Other protocols for
transporting bootstrapping messages can be added in future
references.
All security assocaitions established are between the new device and
the Registrar regardless of proxy operations.
If multiple proxies are available the New Entity tries each until a
successful bootstrapping occurs. The New Entity may prioritize
proxies selection order as appropriate for the anticipated
environment.
If Proxy discovery fails the New Entity moves on to discovering a
Registrar directly.
4.1.2. Receiving and accepting the Domain Identity
The domain trust anchor is received by the New Entity during the
boostrapping protocol exchange.
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 and using a configured Explicit TA database (not an autonomic
solution because the distribution of symmetric key material is not
autonomic).
This document describes two additional autonomic methods:
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MASA authorization token Authorization tokens are obtained by the
Registrar from the MASA cloud service and presented to the New
Entity for validation.
URL redirect If the New Entity discovers a well known global
registrar using DNS then the EST protocol exchange is protected
using an Implicit TA database, but also the MASA authorization is
required. The global registrar MUST claim the device with the
MASA server to ensure the logging information is consistent. The
global registrar forwards the New Entity to an alternate URI as
described in EST [RFC7030].
If these methods fail the New Entity returns to discovery state and
attempts bootstrapping with the next available discovered Registrar.
[[EDNOTE: move protocol discussion down into protocol section]] The
domain trust anchor MUST be included in the TLS handshake Server
Certificate "certificate_list" [RFC5246] or the client MUST request
the EST Bootstrap Distribution of CA Certificates [RFC7030]. (This
document defines an additional method for accepting the CA
certificates).
4.1.3. 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 primarly 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
[[EDNOTE: or in the non-autonomic case using the the out of band
secret].
o The EST section 4.1.3 CA Certificates Response is verified using
the MASA authorization token provided domain identity.
4.1.4. After Enrollment
Functionality to provide generic "configuration" 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.
See Section 4.5.
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4.2. Behavior of a proxy
The role of the Proxy is to facilitate communications. The Proxy
forwards messages between the New Entity and a Registrar. Where
existing protocols as detailed in Section 4.1.1 already provide this
functionality nothing additional is defined.
[[EDNOTE: If neighbor discovery protocols are used for Proxy
discovery then a proxy forwarding protocol is to be defined here]]
4.3. Behavior of the Registrar
One 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:
4.3.1. Authenticating the Device
The 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).
4.3.2. Accepting the Entity
In a fully automated nework all devices must be securely identified.
A Registrar accepts or declines a request to join the domain, based
on the authenticated identity presented and other policy defined
criteria such as Proxy identity. 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 Factory (as determined by the
IEEE 802.1AR identity),
o allow a specific device from a Factory (as determined by the IEEE
802.1AR identity)
In all cases a Registrar must use the globally available MASA cloud
service to verify the device's history log does not include
unexpected Registrars.
If a device is accepted into the domain, it is then invited to
request a domain certificate through a certificate enrolment process.
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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.
4.3.3. Claiming the new entity
During initial bootstrapping the New Entity provides a nonce specific
to the particular bootstrapping attempt. The registrar should
include this nonce when claiming the New Entity from the MASA cloud
service. If a nonce is provided by the Registrar then claims from an
unauthenticated Registrar are serviced by the MASA cloud resource.
The Registrar can claim a New Entity that is not online by forming
the request using the entities unique identifier but not including a
nonce in the claim request. MASA authorization tokens obtained in
this way do not have a lifetime and they provide a permanent method
for the domain to claim the device. Evidence of such a claim is
provided in the audit log entries available to any future Registrar.
Such claims reduce the ability for future domains to secure
bootstrapping and therefore the Registrar MUST be authenticated by
the MASA cloud service.
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 4.1.2 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
occurs if the claim has been logged.
4.4. Behavior of the MASA Cloud Service
The cloud service is provided by the Factory provider. The URI of
the cloud service is well known. The URI should be provided as an
IEEE 802.1AR IDevID X.509 extension (a "MASA authorization token
Distribution Point" extension).
The cloud service provides the following functionalities to
Registrars:
4.4.1. Issue Authorization Token and Log the event
A Registrar POSTs a claim message optionally containing the bootstrap
nonce to the MASA server.
If a nonce is provided the MASA cloud service responds to all
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requests. The MASA cloud service verifies the Registrar is
representative of the domain and generates a privacy protected log
entry before responding with the authorization token.
If a nonce is not provided the MASA cloud service MUST authenticate
the Registrar as a valid customer. This prevents denial of service
attacks. The specific level of authentication provided by the
customer is not defined here. An MASA Practice Statement (MPS)
similar to the Certification Authority CPS, as defined in RFC5280, is
provided by the Factory such that Registrar's can determine the level
of trust they have in the Factory.
4.4.2. Retrieve Audit Entries from Log
When determining if a New Entity should be accepted into a domain the
Registrar retrieves a copy of the audit log from the MASA cloud
service. This contains a list of privacy protected domain identities
that have previously claimed the device. Included in the list is an
indication of the time the entry was made and if the nonce was
included.
4.5. Leveraging the new key infrastructure / next steps
As the devices have a common trust anchor, device identity can be
securely established, making it possible to automatically deploy
services across the domain in a secure manner.
Examples of services:
o Device management.
o Routing authentication.
o Service discovery.
4.5.1. Network boundaries
When a device has joined the domain, it can validate the domain
membership of other devices. This makes it possible to create trust
boundaries where domain members have higher level of trusted than
external devices. Using the autonomic User Interface, specific
devices can be grouped into to sub domains and specific trust levels
can be implemented between those.
5. Protocol Details
The bootstrapping protocol is an extension of EST [RFC7030].
[[EDNOTE: Insert figure here]]
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EST provides a bootstrapping mechanism for new entities that are
configured with the URI of the EST server or new entities that can
"engage a human user to authorize the CA certificate using out-of-
band data such as a CA certificate". EST does not provide a
completely automated method of bootstrapping the PKI. [[EDNOTE: This
paragraph should be expanded to provide a detailed discussion of
current EST functionalitites, or do we assume the reader follows the
normative reference?]].
The following additions provide for fully automated functionality.
EST is extended by defining additional HTTP URIs and messages
specific to bootstrapping. These are optionally supported by the EST
server within the same .well-known URI tree as the existing EST URIs.
The "New Entity" is the EST client and the "Registrar" is the EST
server.
5.1. EAP-EST
In order to support Proxy environments EAP-EST is defined.
[[EDNOTE: TBD. EST is TLS with some data. EAP-TLS and other similar
protocols provide an example framework for filling out this section]]
5.2. Request bootstrap token
When the New Entity reaches the EST section 4.1.1 "Bootstrap
Distribution of CA Certificates" state but wishes to proceed in a
fully automated fashion it makes a request for a MASA authorization
token from the Registrar.
This is done with an HTTPS POST using the operation path value of
"/requestbootstraptoken".
The request format is a raw nonce value. [[EDNOTE: exact format TBD.
There is an advantage to having the client sign the nonce (similar to
a PKI Certification Signing Request) since this allows the MASA cloud
service to confirm the actual device identity. It is not clear that
there is a security benefit from this.]]
The Registrar validates the client identity as described in EST
[RFC7030] section 3.3.2. The registrar performs authorization as
detailed in Section 4.3.2. If authorization is successful the
Registrar obtains a MASA authorization token from the MASA cloud
service (see Section 5.3).
The recieved MASA authorization token is returned to the New Entity.
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[[EDNOTE: update to CMS language]]
5.3. Request MASA authorization token
A registrar requests the MASA authorization token from the cloud
service using this EST extension.
This is done with an HTTP POST using the operation path value of
"/requestMASAauthorization".
The request format is an optional raw nonce value (as obtained from
the bootstrap request) and the IEEE 802.1AR identity of the device as
a serial number (the full certificate is not needed and no proof-of-
possession information for the device identity is included). This
information is encapsulated in a PKCS7 signed data structure that is
signed by the Registrar. The entire certificate chain, up to and
including the Domain CA, is included in the PKCS7.
The MASA cloud service checks the internal consistency of the PKCS7
but is unable to actually authenticate the domain identity
information. The domain is not know to the MASA server in advance
and a shared trust anchor is not implied. The MASA server verifies
that the PKCS7 is signed by a Registrar (by checking for the cmc-idRA
field in the Registrar certificate) certificate that was issued by
the root certificate included in the PKCS7.
The domain ID is extracted from the root certificate and is used to
generate the MASA authorization token and to update the audit log.
[[EDNOTE: update to CMS language]]
5.4. Request MASA authorization log
A registrar requests the MASA authorization log from the cloud
service using this EST extension.
This is done with an HTTP GET using the operation path value of
"/requestMASAlog".
The log data returned is a file consisting of each log entry. The
data in each entry includes:
o date/time of the entry
o domain ID (this is just a hash of the public key information and
is thus privacy protected)
o nonce value
[[EDNOTE: exact format TBD]]
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6. Reduced security operational modes
A common requirement of bootstrapping infrastructures is often that
they support less secure operational modes. To support these
operational modes the Registrar can choose to accept devices using
less secure methods. For example:
1. The registrar may chose to accept all devices, or all devices of
a particular type, at the administrator's discretion. This may
occur when: Informing the Registrar of unique identifiers of new
entities might be operationally difficult.
2. The registrar may chose to accept devices that claim a unique
identity without the benefit of authenticating that claimed
identity. This may occur when: The New Entity does not include
an IEEE 802.1AR factory installed credential.
3. A representative of the Registar (e.g. the Orchestrator) may
request nonce-less authorization tokens from the MASA cloud
service when network connectivity is available. These tokens can
then be transmitted to the Registrar and stored until they are
needed during bootstrapping operations. Ths may occur when: The
target network is protected by an air gap and therefore can not
contact the MASA cloud service during New Entity deployment.
4. The device may have an operational mode where it skips
authorization token validation. For example if a physical button
is depressed during the bootstrapping operation. This may occur
when: A device Factory goes out of business or otherwise fails to
provide a reliable MASA cloud service.
5. The device may not require the MASA cloud service authorization
token. An entity that does not validate the domain identity is
inherently dangerous as it may contain malware. This risk should
be mitigated using attestation and measurement technologies. In
order to support an unsecured imprint the New Entity MUST support
remote attestation technologies such as is defined by the Trusted
Computing Group. [[EDNOTE: How to include remote attestation
into the boostrapping protocol exchange is TBD]]. This may occur
when: The device Factory does not provide a MASA cloud service.
7. Security Considerations
In order to support a variety of use cases, devices can be claimed by
a registrar without proving possession of the device in question.
This would result in a nonceless, and thus always valid, claim. The
MASA cloud service is required to authenticate such Registrars but no
programatic method is provided to ensure good behavior by the MASA
cloud service. Nonceless entries into the audit log therefore
permanently reduce the value of a device because future Registrars,
during future bootstrap attempts, must now be configured with policy
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to ignore previously (and potentially unknown) domains.
Future registrars are recommended to take the audit history of a
device into account when deciding to join such devices into their
network.
It is possible for an attacker to send an authorization request to
the MASA cloud service directly after the real Registrar obtains an
authorization log. If the attacker could also force the
bootstrapping protocol to reset there is a theoretical opportunity
for the attacker to use the authorization token to take control of
the New Entity but then proceed to enrol with the target domain. To
prevent this the MASA cloud service is rate limited to only generate
authorization tokens at a rate of 1 per minute. The Registrar
therefore has at least 1 minute to get the response back to the New
Entity. [[EDNOTE: a better solution can likely be found. This text
captures the issue for now.]] Also the Registar can double check the
log information after enrolling the New Entity.
The MASA cloud service could lock a claim and refuse to issue a new
token. Or the MASA cloud service could go offline (for example if a
vendor went out of business). This functionality provides benefits
such as theft resistance, but it also implies an operational risk.
This can be mitigated by Registrars that request nonce-less
authorization tokens.
8. References
8.1. Normative References
[IDevID] IEEE Standard, "IEEE 802.1AR Secure Device Identifier",
December 2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC7030] Pritikin, M., Yee, P., and D. Harkins, "Enrollment over
Secure Transport", RFC 7030, October 2013.
8.2. Informative References
[I-D.behringer-autonomic-network-framework]
Behringer, M., Pritikin, M., Bjarnason, S., and A. Clemm,
"A Framework for Autonomic Networking",
draft-behringer-autonomic-network-framework-01 (work in
progress), October 2013.
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Authors' Addresses
Max Pritikin
Cisco
Email: pritikin@cisco.com
Michael H. Behringer
Cisco
Email: mbehring@cisco.com
Steinthor Bjarnason
Cisco
Email: sbjarnas@cisco.com
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