draft-ietf-anima-bootstrapping-keyinfra-04.txt   draft-ietf-anima-bootstrapping-keyinfra-05.txt 
ANIMA WG M. Pritikin ANIMA WG M. Pritikin
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Informational M. Richardson Intended status: Informational M. Richardson
Expires: May 4, 2017 SSW Expires: September 14, 2017 SSW
M. Behringer M. Behringer
S. Bjarnason S. Bjarnason
Cisco Cisco
K. Watsen K. Watsen
Juniper Networks Juniper Networks
October 31, 2016 March 13, 2017
Bootstrapping Remote Secure Key Infrastructures (BRSKI) Bootstrapping Remote Secure Key Infrastructures (BRSKI)
draft-ietf-anima-bootstrapping-keyinfra-04 draft-ietf-anima-bootstrapping-keyinfra-05
Abstract Abstract
This document specifies automated bootstrapping of a remote secure This document specifies automated bootstrapping of a remote secure
key infrastructure (BRSKI) using vendor installed X.509 certificate, key infrastructure (BRSKI) using vendor installed X.509 certificate,
in combination with a vendor authorized service on the Internet. in combination with a vendor's authorizing service, both online the
Bootstrapping a new device can occur using a routable address and a Internet, and offline. Bootstrapping a new device can occur using a
cloud service, or using only link-local connectivity, or on limited/ routable address and a cloud service, or using only link-local
disconnected networks. Support for lower security models, including connectivity, or on limited/disconnected networks. Support for lower
devices with minimal identity, is described for legacy reasons but security models, including devices with minimal identity, is
not encouraged. Bootstrapping is complete when the cryptographic described for legacy reasons but not encouraged. Bootstrapping is
identity of the new key infrastructure is successfully deployed to complete when the cryptographic identity of the new key
the device but the established secure connection can be used to infrastructure is successfully deployed to the device but the
deploy a locally issued certificate to the device as well. established secure connection can be used to deploy a locally issued
certificate to the device as well.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 4, 2017. This Internet-Draft will expire on September 14, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Secure Imprinting without Vouchers . . . . . . . . . . . 5
1.2. Scope of solution . . . . . . . . . . . . . . . . . . . . 7 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Trust bootstrap . . . . . . . . . . . . . . . . . . . . . 8 1.3. Scope of solution . . . . . . . . . . . . . . . . . . . . 8
2. Architectural Overview . . . . . . . . . . . . . . . . . . . 8 2. Architectural Overview . . . . . . . . . . . . . . . . . . . 9
3. Functional Overview . . . . . . . . . . . . . . . . . . . . . 10 2.1. Secure Imprinting without Vouchers . . . . . . . . . . . 11
3.1. Behavior of a Pledge . . . . . . . . . . . . . . . . . . 11 2.2. Secure Imprinting using Vouchers . . . . . . . . . . . . 12
3.1.1. Discovery . . . . . . . . . . . . . . . . . . . . . . 13 2.3. Initial Device Identifier . . . . . . . . . . . . . . . . 12
3.1.2. Identity . . . . . . . . . . . . . . . . . . . . . . 14 3. Functional Overview . . . . . . . . . . . . . . . . . . . . . 13
3.1.3. Request Join . . . . . . . . . . . . . . . . . . . . 15 3.1. Behavior of a Pledge . . . . . . . . . . . . . . . . . . 15
3.1.4. Imprint . . . . . . . . . . . . . . . . . . . . . . . 15 3.1.1. Discovery . . . . . . . . . . . . . . . . . . . . . . 17
3.1.5. Lack of realtime clock . . . . . . . . . . . . . . . 16 3.1.2. Identity . . . . . . . . . . . . . . . . . . . . . . 18
3.1.6. Enrollment . . . . . . . . . . . . . . . . . . . . . 17 3.1.3. Request Join . . . . . . . . . . . . . . . . . . . . 18
3.1.7. Being Managed . . . . . . . . . . . . . . . . . . . . 18 3.1.4. Imprint . . . . . . . . . . . . . . . . . . . . . . . 19
3.2. Behavior of a Proxy . . . . . . . . . . . . . . . . . . . 18 3.1.5. Lack of realtime clock . . . . . . . . . . . . . . . 19
3.2.1. CoAP connection to Registrar . . . . . . . . . . . . 19 3.1.6. Enrollment . . . . . . . . . . . . . . . . . . . . . 20
3.2.2. HTTPS proxy connection to Registrar . . . . . . . . . 19 3.1.7. Being Managed . . . . . . . . . . . . . . . . . . . . 20
3.3. Behavior of the Registrar . . . . . . . . . . . . . . . . 20 3.2. Behavior of a Join Proxy . . . . . . . . . . . . . . . . 21
3.3.1. Pledge Authentication . . . . . . . . . . . . . . . . 21 3.2.1. CoAP connection to Registrar . . . . . . . . . . . . 22
3.3.2. Pledge Authorization . . . . . . . . . . . . . . . . 22 3.2.2. HTTPS proxy connection to Registrar . . . . . . . . . 22
3.3.3. Claiming the New Entity . . . . . . . . . . . . . . . 23 3.3. Behavior of the Registrar . . . . . . . . . . . . . . . . 22
3.3.4. Log Verification . . . . . . . . . . . . . . . . . . 23 3.3.1. Pledge Authentication . . . . . . . . . . . . . . . . 23
3.4. Behavior of the MASA Service . . . . . . . . . . . . . . 24 3.3.2. Pledge Authorization . . . . . . . . . . . . . . . . 24
3.4.1. Issue Audit Voucher and Log the event . . . . . . . . 24 3.3.3. Claiming the New Entity . . . . . . . . . . . . . . . 24
3.4.2. Retrieve Audit Entries from Log . . . . . . . . . . . 24 3.3.4. Log Verification . . . . . . . . . . . . . . . . . . 25
3.5. Leveraging the new key infrastructure / next steps . . . 25 3.4. Behavior of the MASA Service . . . . . . . . . . . . . . 26
3.5.1. Network boundaries . . . . . . . . . . . . . . . . . 25 3.5. Leveraging the new key infrastructure / next steps . . . 26
3.6. Interactions with Network Access Control . . . . . . . . 25 3.5.1. Network boundaries . . . . . . . . . . . . . . . . . 26
4. Domain Operator Activities . . . . . . . . . . . . . . . . . 25 3.6. Interactions with Network Access Control . . . . . . . . 27
4.1. Instantiating the Domain Certification Authority . . . . 26 4. Domain Operator Activities . . . . . . . . . . . . . . . . . 27
4.2. Instantiating the Registrar . . . . . . . . . . . . . . . 26 4.1. Instantiating the Domain Certification Authority . . . . 27
4.3. Accepting New Entities . . . . . . . . . . . . . . . . . 26 4.2. Instantiating the Registrar . . . . . . . . . . . . . . . 27
4.4. Automatic Enrollment of Devices . . . . . . . . . . . . . 27 4.3. Accepting New Entities . . . . . . . . . . . . . . . . . 28
4.5. Secure Network Operations . . . . . . . . . . . . . . . . 27 4.4. Automatic Enrollment of Devices . . . . . . . . . . . . . 29
5. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 28 4.5. Secure Network Operations . . . . . . . . . . . . . . . . 29
5.1. Request Voucher from the Registrar . . . . . . . . . . . 30 5. Proxy Discovery Protocol Details . . . . . . . . . . . . . . 29
5.2. Request Voucher from MASA . . . . . . . . . . . . . . . . 32 6. Registrar Discovery Protocol Details . . . . . . . . . . . . 29
5.3. Audit Voucher Response . . . . . . . . . . . . . . . . . 33 7. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 30
5.3.1. Completing authentication of Provisional TLS 7.1. Request Voucher from the Registrar . . . . . . . . . . . 34
connection . . . . . . . . . . . . . . . . . . . . . 34 7.2. Request Voucher from MASA . . . . . . . . . . . . . . . . 35
5.4. Voucher Status Telemetry . . . . . . . . . . . . . . . . 35 7.3. Voucher Response . . . . . . . . . . . . . . . . . . . . 36
5.5. MASA authorization log Request . . . . . . . . . . . . . 36 7.3.1. Completing authentication of Provisional TLS
5.6. MASA authorization log Response . . . . . . . . . . . . . 36 connection . . . . . . . . . . . . . . . . . . . . . 37
5.7. EST Integration for PKI bootstrapping . . . . . . . . . . 37 7.4. Voucher Status Telemetry . . . . . . . . . . . . . . . . 38
5.7.1. EST Distribution of CA Certificates . . . . . . . . . 37 7.5. MASA authorization log Request . . . . . . . . . . . . . 39
5.7.2. EST CSR Attributes . . . . . . . . . . . . . . . . . 37 7.6. MASA authorization log Response . . . . . . . . . . . . . 39
5.7.3. EST Client Certificate Request . . . . . . . . . . . 38 7.7. EST Integration for PKI bootstrapping . . . . . . . . . . 40
5.7.4. Enrollment Status Telemetry . . . . . . . . . . . . . 38 7.7.1. EST Distribution of CA Certificates . . . . . . . . . 41
5.7.5. EST over CoAP . . . . . . . . . . . . . . . . . . . . 39 7.7.2. EST CSR Attributes . . . . . . . . . . . . . . . . . 41
6. Reduced security operational modes . . . . . . . . . . . . . 39 7.7.3. EST Client Certificate Request . . . . . . . . . . . 42
6.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 40 7.7.4. Enrollment Status Telemetry . . . . . . . . . . . . . 42
6.2. New Entity security reductions . . . . . . . . . . . . . 40 7.7.5. EST over CoAP . . . . . . . . . . . . . . . . . . . . 43
6.3. Registrar security reductions . . . . . . . . . . . . . . 41 8. Reduced security operational modes . . . . . . . . . . . . . 43
6.4. MASA security reductions . . . . . . . . . . . . . . . . 42 8.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 43
7. Security Considerations . . . . . . . . . . . . . . . . . . . 42 8.2. New Entity security reductions . . . . . . . . . . . . . 44
7.1. Security concerns with discovery process . . . . . . . . 44 8.3. Registrar security reductions . . . . . . . . . . . . . . 44
7.1.1. Discovery of Registrar by Proxy . . . . . . . . . . . 44 8.4. MASA security reductions . . . . . . . . . . . . . . . . 45
7.1.2. Discovery of Proxy by New Entity . . . . . . . . . . 44 9. Security Considerations . . . . . . . . . . . . . . . . . . . 46
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 44 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 48
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 44 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 48
9.1. Normative References . . . . . . . . . . . . . . . . . . 44 11.1. Normative References . . . . . . . . . . . . . . . . . . 48
9.2. Informative References . . . . . . . . . . . . . . . . . 46 11.2. Informative References . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 47 Appendix A. IPv4 operations . . . . . . . . . . . . . . . . . . 51
A.1. IPv4 Link Local addresses . . . . . . . . . . . . . . . . 51
A.2. Use of DHCPv4 . . . . . . . . . . . . . . . . . . . . . . 51
Appendix B. mDNS / DNSSD proxy discovery options . . . . . . . . 51
Appendix C. IPIP Join Proxy mechanism . . . . . . . . . . . . . 52
C.1. Multiple Join networks on the Join Proxy side . . . . . . 53
C.2. Automatic configuration of tunnels on Registrar . . . . . 53
C.3. Proxy Neighbor Discovery by Join Proxy . . . . . . . . . 53
C.4. Use of connected sockets; or IP_PKTINFO for CoAP on
Registrar . . . . . . . . . . . . . . . . . . . . . . . . 54
C.5. Use of socket extension rather than virtual interface . . 54
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
1. Introduction 1. Introduction
To literally "pull yourself up by the bootstraps" is an impossible To literally "pull yourself up by the bootstraps" is an impossible
action. Similarly the secure establishment of a key infrastructure action. Similarly the secure establishment of a key infrastructure
without external help is also an impossibility. Today it is accepted without external help is also an impossibility. Today it is commonly
that the initial connections between nodes are insecure, until key accepted that the initial connections between nodes are insecure,
distribution is complete, or that domain-specific keying material is until key distribution is complete, or that domain-specific keying
pre-provisioned on each new device in a costly and non-scalable material is pre-provisioned on each new device in a costly and non-
manner. This document describes a zero-touch approach to scalable manner. These existing mechanisms are known as non-secured
bootstrapping an entity by securing the initial distribution of key 'Trust on First Use' (TOFU) [RFC7435], 'resurrecting duckling'
material using third-party issued X.509 certificates and [Stajano99theresurrecting] or 'pre-staging'.
cryptographically signed "vouchers" issued by a new form of cloud
service.
The two sides of an association being bootstrapped authenticate each This document describes a zero-touch approach to bootstrapping that
other and then determine appropriate authorization. This process is secures the initial distribution of key material between an
described as four distinct steps between the existing domain and the unconfigured and untouched device called a "Pledge" and the
device, or "pledge", being added: "Registrar" device that is a member of an established network domain.
The bootstrapping process provides a foundation to securely answer
the following questions:
o Pledge authentication: "Who is this? What is its identity?" o Registrar authenticating the Pledge: "Who is this device? What is
its identity?"
o Pledge authorization: "Is it mine? Do I want it? What are the o Registrar authorization the Pledge: "Is it mine? Do I want it?
chances it has been compromised?" What are the chances it has been compromised?"
o Domain authentication: "What is this domain's claimed identity?" o Pledge authenticating the Registrar/Domain: "What is this domain's
identity?"
o Domain authorization: "Should I join it?" o Pledge authorization the Registrar: "Should I join it?"
A precise answer to these questions can not be obtained without This document details protocols and messages to the endpoints to
leveraging an established key infrastructure(s). The pledge's answer the above questions. The Registrar actions derive from Pledge
decisions are made according to verified communication with a trusted identity, third party cloud service communications, and local access
third-party. The domain's decisions are made by comparing the control lists. The Pledge actions derive from a cryptographically
pledge's authenticated identity against domain information such as a protected "voucher" message delivered through the Registrar.
configured list of purchased devices supplimented by information Multiple forms of "vouchers" are described to support a variety of
provided by a trusted third-party. The third-party is not required use cases.
to provide sales channel ownership tracking nor is it required to
authenticate the domain.
Optimal security is achieved with X.509 certificates on each Pledge, The syntactic details of vouchers are described in detail in
accompanied by a third-party (e.g., vendor, manufacturer or [I-D.ietf-anima-voucher]. This document details automated protocol
integrator) Internet based service for verification. Bootstrapping mechanisms to obtain vouchers.
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
pledge.
The result of bootstrapping is that a domain specific key The result of bootstrapping is that a security association between
infrastructure is deployed. Since X.509 PKI certificates are used the Pledge and the Registrar is established. A method of leveraging
for identifying the pledge, and the public key of the domain identity this association to optimize PKI enrollment is described.
is leveraged during communications 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 described system is agile enough to support bootstrapping
alternative key infrastructures, such as a symmetric key solutions,
but no such system is described.
1.1. Secure Imprinting without Vouchers
There are pre-existing methods available for establishing initial
trust. For example 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).
These "touch" methods do not meet the requirements for zero-touch.
There are "call home" technologies where the Pledge first establishes
a connection to a well known vendor service using a common client-
server authentication model. After mutual authentication appropriate
credentials to authenticate the target domain are transfered to the
Pledge. This creates serveral problems and limitations:
o the pledge requires realtime connectivity to the vendor service,
o the domain identity is exposed to the vendor service (this is a
privacy concern),
o the vendor is responsible for making the authorization decisions
(this is a liability concern),
BRSKI addresses these issues by introducting an authorization layer
via "vouchers". The additional complexity provides for significant
flexibility.
1.2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
The following terms are defined for clarity: The following terms are defined for clarity:
DomainID: The domain identity is the 160-bit SHA-1 hash of the BIT 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 STRING of the subjectPublicKey of the domain trust anchor that is
skipping to change at page 5, line 52 skipping to change at page 7, line 4
network and acquires a network specific identity. For example network and acquires a network specific identity. For example
when a certificate signing request is presented to a certification when a certificate signing request is presented to a certification
authority and a certificate is obtained in response. authority and a certificate is obtained in response.
Pledge: The prospective device, which has an identity installed by a Pledge: The prospective device, which has an identity installed by a
third-party (e.g., vendor, manufacturer or integrator). third-party (e.g., vendor, manufacturer or integrator).
Voucher A signed statement from the MASA service that indicates to a Voucher A signed statement from the MASA service that indicates to a
Pledge the cryptographic identity of the Registrar it should Pledge the cryptographic identity of the Registrar it should
trust. There are different types of vouchers depending on how trust. There are different types of vouchers depending on how
that trust verified. that trust asserted. Multiple voucher types are defined in
[I-D.ietf-anima-voucher]
Audit Voucher: A voucher from the MASA service that indicates that
the bootstrapping event has been successfully logged. The
Registrar is primarily responsible for verifying the logs and
ensuring domain network security.
Ownership Voucher: A voucher from the MASA service that indicates
the explicit owner identity. The MASA is primarily responsible
for tracking ownership using out-of-band sales channel integration
(the definition of which is out-of-scope of this document). It is
defined in [I-D.ietf-netconf-zerotouch].
Domain: The set of entities that trust a common key infrastructure Domain: The set of entities that trust a common key infrastructure
trust anchor. This includes the Proxy, Registrar, Domain trust anchor. This includes the Proxy, Registrar, Domain
Certificate Authority, Management components and any existing Certificate Authority, Management components and any existing
entity that is already a member of the domain. entity that is already a member of the domain.
Domain CA: The domain Certification Authority (CA) provides Domain CA: The domain Certification Authority (CA) provides
certification functionalities to the domain. At a minimum it certification functionalities to the domain. At a minimum it
provides certification functionalities to a Registrar and stores provides certification functionalities to a Registrar and stores
the trust anchor that defines the domain. Optionally, it the trust anchor that defines the domain. Optionally, it
certifies all elements. certifies all elements.
Registrar: A representative of the domain that is configured, Join Registrar (and Coordinator): A representative of the domain
perhaps autonomically, to decide whether a new device is allowed that is configured, perhaps autonomically, to decide whether a new
to join the domain. The administrator of the domain interfaces device is allowed to join the domain. The administrator of the
with a Registrar to control this process. Typically a Registrar domain interfaces with a Join Registrar (and Coordinator) to
is "inside" its domain. control this process. Typically a Join Registrar is "inside" its
domain. For simplicity this document often refers to this as just
"Registrar". The term JRC is used in common with other bootstrap
mechanisms.
Proxy: A domain entity that helps the pledge join the domain. A Join Proxy: A domain entity that helps the pledge join the domain.
Proxy facilitates communication for devices that find themselves A Proxy facilitates communication for devices that find themselves
in an environment where they are not provided connectivity until in an environment where they are not provided connectivity until
after they are validated as members of the domain. The pledge is after they are validated as members of the domain. The pledge is
unaware that they are communicating with a proxy rather than unaware that they are communicating with a proxy rather than
directly with a Registrar. directly with a Registrar.
MASA Service: A third-party Manufacturer Authorized Signing MASA Service: A third-party Manufacturer Authorized Signing
Authority (MASA) service on the global Internet. The MASA Authority (MASA) service on the global Internet. The MASA signs
provides a repository for audit log information concerning privacy vouchers. It also provides a repository for audit log information
protected bootstrapping events. It does not track ownership. of privacy protected bootstrapping events. It does not track
ownership.
Ownership Tracker An Ownership Tracker service on the global Ownership Tracker: An Ownership Tracker service on the global
internet. The Ownership Tracker uses business processes to internet. The Ownership Tracker uses business processes to
accurately track ownership of all devices shipped against domains accurately track ownership of all devices shipped against domains
that have purchased them. Although optional this component allows that have purchased them. Although optional this component allows
vendors to provide additional value in cases where their sales and vendors to provide additional value in cases where their sales and
distribution channels allow for accurately tracking of such distribution channels allow for accurately tracking of such
ownership. ownership. Ownership tracking information is indicated in
vouchers as described in [I-D.ietf-anima-voucher]
IDevID An Initial Device Identity X.509 certificate installed by the IDevID: An Initial Device Identity X.509 certificate installed by
vendor on new equipment. The [IDevID] certificate format is the the vendor on new equipment.
primary example. In particular the X.509 certificate needs to
contain the device's serial number in a well known location in
order to perform white list operations and in order to extract it
for inclusion in messages to the MASA service. The subject
field's DN encoding MUST include the "serialNumber" attribute with
the device's unique serial number.
1.2. Scope of solution TOFU: Trust on First Use. Used similarly to [RFC7435]. This is
where a Pledge device makes no security decisions but rather
simply trusts the first Registrar it is contacted by. This is
also known as the "resurrecting duckling" model.
1.3. Scope of solution
Questions have been posed as to whether this solution is suitable in Questions have been posed as to whether this solution is suitable in
general for Internet of Things (IoT) networks. This depends on the general for Internet of Things (IoT) networks. This depends on the
capabilities of the devices in question. The terminology of capabilities of the devices in question. The terminology of
[RFC7228] is best used to describe the boundaries. [RFC7228] is best used to describe the boundaries.
The entire solution described in this document is aimed in general at The solution described in this document is aimed in general at non-
non-constrained (i.e. class 2+) devices operating on a non-Challenged constrained (i.e. class 2+) devices operating on a non-Challenged
network. The entire solution described here is not intended to be network. The entire solution as described here is not intended to be
useable as-is by constrained devices operating on challenged networks useable as-is by constrained devices operating on challenged networks
(such as 802.15.4 LLNs). (such as 802.15.4 LLNs).
There are a number of optional mechanisms in BRSKI. These mechanisms
are not mandatory to implement for the core applicability to ANIMA.
These mechanisms have been moved out of the main flow of the document
to appendices to emphasis that they are not considered normative,
mandatory to implement, while making it easier for another document
to normatively reference them.
In many target applications, the systems involved are large router In many target applications, the systems involved are large router
platforms with multi-gigabit inter-connections, mounted in controlled platforms with multi-gigabit inter-connections, mounted in controlled
access data centers. But this solution is not exclusive to the access data centers. But this solution is not exclusive to the
large, it is intended to scale to thousands of devices located in large, it is intended to scale to thousands of devices located in
hostile environments, such as ISP provided CPE devices which are hostile environments, such as ISP provided CPE devices which are
drop-shipped to the end user. The situation where an order is drop-shipped to the end user. The situation where an order is
fulfilled from distributed warehouse from a common stock and shipped fulfilled from distributed warehouse from a common stock and shipped
directly to the target location at the request of the domain owner is directly to the target location at the request of the domain owner is
explicitly supported. That stock ("SKU") could be provided to a explicitly supported. That stock ("SKU") could be provided to a
number of potential domain owners, and the eventual domain owner will number of potential domain owners, and the eventual domain owner will
not know a-priori which device will go to which location. not know a-priori which device will go to which location.
The bootstraping process can take minutes to complete depending on The bootstrapping process can take minutes to complete depending on
the network infrastructure and device processing speed. The network the network infrastructure and device processing speed. The network
communication itself is not optimized for speed; the discovery communication itself is not optimized for speed; for privacy reasons,
process allows for the Pledge to avoid broadcasting for privacy the discovery process allows for the Pledge to avoid announcing it's
reasons. This protocol is not intended for low latency handoffs. presence through broadcasting. This protocol is not intended for low
latency handoffs. In networks requiring such things, the pledge
SHOULD already have been enrolled.
Specifically, there are protocol aspects described here which might Specifically, there are protocol aspects described here which might
result in congestion collapse or energy-exhaustion of intermediate result in congestion collapse or energy-exhaustion of intermediate
battery powered routers in an LLN. Those types of networks SHOULD battery powered routers in an LLN. Those types of networks SHOULD
NOT use this solution. These limitations are predominately related NOT use this solution. These limitations are predominately related
to the large credential and key sizes required for device to the large credential and key sizes required for device
authentication. Defining symmetric key techniques that meet the authentication. Defining symmetric key techniques that meet the
operational requirements is out-of-scope but the underlying protocol operational requirements is out-of-scope but the underlying protocol
operations (TLS handshake and signing structures) have sufficient operations (TLS handshake and signing structures) have sufficient
algorithm agility to support such techniques when defined. algorithm agility to support such techniques when defined.
The imprint protocol described here could, however, be used by non- The imprint protocol described here could, however, be used by non-
energy constrained devices joining a non-constrained network (for energy constrained devices joining a non-constrained network (for
instance, smart light bulbs are usually mains powered, and speak instance, smart light bulbs are usually mains powered, and speak
802.11). It could also be used by non-constrained devices across a 802.11). It could also be used by non-constrained devices across a
non-energy constrained, but challenged network (such as 802.15.4). non-energy constrained, but challenged network (such as 802.15.4).
The use of an IDevID that is consistant with [IDevID] allows for This document presumes that network access control has either already
alignment with 802.1X network access control methods which could need occurred, is not required, or is integrated by the proxy and
to complete before bootstrapping can be initiated. This document registrar in such a way that the device itself does not need to be
presumes that network access control has either already occured, is aware of the details. Although the use of an X.509 Initial Device
not required, or is integrated by the proxy and registrar in such a Identity is consistant with IEEE 802.1AR [IDevID], and allows for
way that the device itself does not need to be aware of the details. alignment with 802.1X network access control methods, its use here is
Further integration is not in scope. for Pledge authentication rather than network access control.
Some aspects are in scope for constrained devices on challenged Some aspects are in scope for constrained devices on challenged
networks: the certificate contents, and the process by which the four networks: the certificate contents, and the process by which the four
questions above are resolved is in scope. It is simply the actual questions above are resolved is in scope. It is simply the actual
on-the-wire imprint protocol which is likely inappropriate. on-the-wire imprint protocol which is likely inappropriate.
1.3. Trust bootstrap
The imprint protocol results in a secure relationship between a
domain Registrar and the Pledge. 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 2. Architectural Overview
The logical elements of the bootstrapping framework are described in The logical elements of the bootstrapping framework are described in
this section. Figure 1 provides a simplified overview of the this section. Figure 1 provides a simplified overview of the
components. Each component is logical and may be combined with other components. Each component is logical and may be combined with other
components as necessary. components as necessary.
. .
.+------------------------+ .+------------------------+
+--------------Drop Ship-------------->.| Vendor Service | +--------------Drop Ship-------------->.| Vendor Service |
skipping to change at page 9, line 20 skipping to change at page 10, line 20
| .| A uthorized |Ownership| | .| A uthorized |Ownership|
| .| S igning |Tracker | | .| S igning |Tracker |
| .| A uthority | | | .| A uthority | |
| .+--------------+---------+ | .+--------------+---------+
| .............. ^ | .............. ^
V | V |
+-------+ ............................................|... +-------+ ............................................|...
| | . | . | | . | .
| | . +------------+ +-----------+ | . | | . +------------+ +-----------+ | .
| | . | | | | | . | | . | | | | | .
| | . | | | <-------+ . |Pledge | . | Circuit | | Domain <-------+ .
| | . | Proxy | | Registrar | . | | . | Proxy | | Registrar | .
| <--------> <-------> | . | <--------> <-------> | .
| New | . | | | | . | | . | | | | .
| Entity| . +------------+ +-----+-----+ . | | . +------------+ +-----+-----+ .
| | . | . |IDevID | . | .
| | . +-----------------+----------+ . | | . +-----------------+----------+ .
| | . | Domain Certification | . | | . | Domain Certification | .
| | . | Authority | . | | . | Authority | .
+-------+ . | Management and etc | . +-------+ . | Management and etc | .
. +----------------------------+ . . +----------------------------+ .
. . . .
................................................ ................................................
"Domain" components "Domain" components
Figure 1 Figure 1
We assume a multi-vendor network. In such an environment there could We assume a multi-vendor network. In such an environment there could
be a MASA or Ownership Tracker for each vendor that supports devices be a Vendor Service for each vendor that supports devices following
following this document's specification, or an integrator could this document's specification, or an integrator could provide a
provide a MASA service for all devices. It is unlikely that an generic service authorized by multiple vendors. It is unlikely that
integrator could provide Ownership Tracking services for multiple an integrator could provide Ownership Tracking services for multiple
vendors. vendors due to the required sales channel integrations necessary to
track ownership.
The domain is the managed network infrastructure the Pledge is
managed by. The a domain provides initial device connectivity
minimally sufficient for bootstrapping through the Circuit Proxy.
The Domain registrar makes authorization decisions and handles
connectivity to the vendor services and authenticates the Pledge.
Optional cryptographic credential and configuration management
systems are expected.
This document describes a secure zero-touch approach to bootstrapping This document describes a secure zero-touch approach to bootstrapping
a key infrastructure; if certain devices in a network do not support a remote key infrastructure. Secure bootstrapping requires
this approach, they can still be bootstrapped manually. Although mitigating the threat of an attacker domain establishing a management
manual deployment is not scalable and is not a focus of this document role over the pledge device. In a "trust on first use" model, where
the necessary mechanisms are called out in this document to ensure this threat is ignored, the attacker has an opportunity to install a
such edge conditions are covered by the architectural and protocol persistent malware component. This document uses Vouchers to address
models. the threat while maintaining a significant level of flexibility.
2.1. Secure Imprinting without Vouchers
There are pre-existing methods available for establishing initial
trust. For example 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).
These "touch" methods do not meet the requirements for zero-touch.
There are "call home" technologies where the Pledge first establishes
a connection to a well known vendor service using a common client-
server authentication model. After mutual authentication appropriate
credentials to authenticate the target domain are transfered to the
Pledge. This creates serveral problems and limitations:
o the pledge requires realtime connectivity to the vendor service,
o the domain identity is exposed to the vendor service (this is a
privacy concern),
o the vendor is responsible for making the authorization decisions
(this is a liability concern),
BRSKI addresses these issues by introducting an authorization layer
via "vouchers". The additional complexity provides for significant
flexibility.
2.2. Secure Imprinting using Vouchers
A voucher is a cryptographically protected statement to the Pledge
device authorizing a zero-touch imprint on the Registrar domain.
The format and cryptographic mechanism of vouchers is described in
detail in [I-D.ietf-anima-voucher].
Vouchers provide a flexible mechanism to secure imprinting: the
Pledge device only imprints when a voucher can be validated. At the
lowest security levels the MASA server can indiscriminately issue
vouchers. At the highest security levels issuance of vouchers can be
integrated with complex sales channel integrations that are beyond
the scope of this document. This provides the flexability for a
number of use cases via a single common protocol mechanism on the
Pledge and Registrar devices that are to be widely deployed in the
field. The MASA vendor services have the flexibility to leverage
either the currently defined claim mechanisms or to experiment with
higher or lower security levels.
2.3. Initial Device Identifier
Pledge authentication is via an X.509 certificate installed during
the manufacturing process. This Initial Device Identifier provides a
basis for authenticating the Pledge during subsequent protocol
exchanges and informing the Registrar of the MASA URI. There is no
requirement for a common root PKI hierarchy. Each device vendor can
generate their own root certificate.
The following previously defined fields are in the X.509 IDevID
certificate:
o The subject field's DN encoding MUST include the "serialNumber"
attribute with the device's unique serial number.
o The subject alt field's encoding SHOULD include the a non-critical
version of the RFC4108 defined HardwareModuleName.
The following newly defined field SHOULD be in the X.509 IDevID
certificate: An X.509 non-critical certificate extension that
contains a single Uniform Resource Identifier (URI) that points to an
on-line Manufacturer Authorized Signing Authority. The URI is
represented as described in Section 7.4 of [RFC5280].
Any Internationalized Resource Identifiers (IRIs) MUST be mapped to
URIs as specified in Section 3.1 of [RFC3987] before they are placed
in the certificate extension.
The semantics of the URI are defined in Section 7 of this document.
The new extension is identified as follows:
<CODE BEGINS>
MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-mod-MASAURLExtn2016(TBD) }
DEFINITIONS IMPLICIT TAGS ::= BEGIN
-- EXPORTS ALL --
IMPORTS
EXTENSION
FROM PKIX-CommonTypes-2009
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkixCommon-02(57) }
id-pe
FROM PKIX1Explicit-2009
{ iso(1) identified-organization(3) dod(6) internet(1)
security(5) mechanisms(5) pkix(7) id-mod(0)
id-mod-pkix1-explicit-02(51) } ;
MASACertExtensions EXTENSION ::= { ext-MASAURL, ... }
ext-MASAURL EXTENSION ::= { SYNTAX MASAURLSyntax
IDENTIFIED BY id-pe-masa-url }
id-pe-masa-url OBJECT IDENTIFIER ::= { id-pe TBD }
MASAURLSyntax ::= IA5String
END
<CODE ENDS>
The choice of id-pe is based on guidance found in Section 4.2.2 of
[RFC5280], "These extensions may be used to direct applications to
on-line information about the issuer or the subject". The MASA URL
is precisely that: online information about the particular subject.
3. Functional Overview 3. Functional Overview
Entities behave in an autonomic fashion. They discover each other Entities behave in an autonomic fashion. They discover each other
and autonomically bootstrap into a key infrastructure delineating the and autonomically bootstrap into a key infrastructure delineating the
autonomic domain. See [RFC7575] for more information. autonomic domain. See [RFC7575] for more information.
This section details the state machine and operational flow for each This section details the state machine and operational flow for each
of the main three entities. The pledge, the domain (primarily a of the main three entities. The pledge, the domain (primarily a
Registrar) and the MASA service. Registrar) and the MASA service.
A representative flow is shown in Figure 2: A representative flow is shown in Figure 2:
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
| Pledge | | Circuit | | Domain | | Vendor | | Pledge | | Circuit | | Domain | | Vendor |
| | | Proxy | | Registrar | | Service | | | | Proxy | | Registrar | | Service |
| | | | | | | (Internet | | | | | | | | (Internet |
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
| | | | | | | |
|<-RFC3927 IPv4 adr | | | |<-RFC3927 IPv4 adr | Appendix A | |
or|<-RFC4862 IPv6 adr | | | or|<-RFC4862 IPv6 adr | | |
| | | | | | | |
|-------------------->| | | |-------------------->| | |
| optional: mDNS query| | | | optional: mDNS query| Appendix B | |
| RFC6763/RFC6762 | | | | RFC6763/RFC6762 | | |
| | | | | | | |
|<--------------------| | | |<--------------------| | |
| mDNS broadcast | | | | GRASP M_FLOOD | | |
| response or periodic| | | | periodic broadcast| | |
| | | | | | | |
|<------------------->C<----------------->| | |<------------------->C<----------------->| |
| TLS via the Circuit Proxy | | | TLS via the Circuit Proxy | |
|<--Registrar TLS server authentication---| | |<--Registrar TLS server authentication---| |
[PROVISIONAL accept of server cert] | | [PROVISIONAL accept of server cert] | |
P---X.509 client authentication---------->| | P---X.509 client authentication---------->| |
P | | | P | | |
P---Request Voucher (include nonce)------>| | P---Request Voucher (include nonce)------>| |
P | | | P | | |
P | /---> | | P | /---> | |
skipping to change at page 12, line 27 skipping to change at page 16, line 27
^------------+ | ^------------+ |
| rejected +------+-------+ | rejected +------+-------+
| | | |
| +------v-------+ | +------v-------+
| | Request | | | Request |
| | Join | | | Join |
| +------+-------+ | +------+-------+
| | | |
| +------v-------+ | +------v-------+
| | Imprint | Optional | | Imprint | Optional
^------------+ <--+Manual input ^------------+ <--+Manual input (Appendix C)
| Bad Vendor +------+-------+ | Bad Vendor +------+-------+
| response | | response |
| +------v-------+ | +------v-------+
| | Enroll | | | Enroll |
^------------+ | ^------------+ |
| Enroll +------+-------+ | Enroll +------+-------+
| Failure | | Failure |
| +------v-------+ | +------v-------+
| | Being | | | Being |
^------------+ Managed | ^------------+ Managed |
Factory +--------------+ Factory +--------------+
reset reset
Figure 3 Figure 3
State descriptions for the pledge are as follows: State descriptions for the pledge are as follows:
1. Discover a communication channel to a Registrar. 1. Discover a communication channel to a Registrar.
2. Identify itself. This is done by presenting an IDevID X.509 2. Identify itself. This is done by presenting an X.509 IDevID
credential to the discovered Registrar (via the Proxy) in a TLS credential to the discovered Registrar (via the Proxy) in a TLS
handshake. (The Registrar credentials are only provisionally handshake. (The Registrar credentials are only provisionally
accepted at this time). accepted at this time).
3. Requests to Join the discovered Registrar. A unique nonce is 3. Requests to Join the discovered Registrar. A unique nonce can be
included ensuring that any responses can be associated with this included ensuring that any responses can be associated with this
particular bootstrapping attempt. particular bootstrapping attempt.
4. Imprint on the Registrar. This requires verification of the 4. Imprint on the Registrar. This requires verification of the
vendor service provided "Audit" or "Ownership" Voucher. Either vendor service provided voucher. A voucher contains sufficient
of these responses contains sufficient information for the pledge information for the Pledge to complete authentication of a
to complete authentication of a Registrar. (The pledge can now Registrar. (It enables the Pledge to finish authentication of
finish authentication of the Registrar TLS server certificate) the Registrar TLS server certificate).
5. Enroll by accepting the domain specific information from a 5. Enroll. By accepting the domain specific information from a
Registrar, and by obtaining a domain certificate from a Registrar Registrar, and by obtaining a domain certificate from a Registrar
using a standard enrollment protocol, e.g. Enrollment over using a standard enrollment protocol, e.g. Enrollment over
Secure Transport (EST) [RFC7030]. Secure Transport (EST) [RFC7030].
6. The Pledge is now a member of, and can be managed by, the domain 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 and will only repeat the discovery aspects of bootstrapping if it
is returned to factory default settings. is returned to factory default settings.
The following sections describe each of these steps in more detail. The following sections describe each of these steps in more detail.
3.1.1. Discovery 3.1.1. Discovery
The result of discovery is a logical communication with a Registrar, The result of discovery is a logical communication with a Registrar,
through a Proxy. The Proxy is transparent to the Pledge but is through a Proxy. The Proxy is transparent to the Pledge but is
always assumed to exist. always assumed to exist.
To discover the Registrar the Pledge performs the following actions: To discover the Registrar the Pledge performs the following actions:
a. MUST: Obtains a local address using either IPv4 or IPv6 methods a. MUST: Obtains a local address using IPv6 methods as described in
as described in [RFC4862] IPv6 Stateless Address [RFC4862] IPv6 Stateless Address AutoConfiguration. [RFC7217] is
AutoConfiguration or [RFC3927] Dynamic Configuration of IPv4 encouraged. IPv4 methods are described in Appendix A
Link-Local Addresses. The Plege MAY obtain an IP address via
DHCP [RFC2131]. The DHCP provided parameters for the Domain Name
System can be used to perform step (d) DNS operations if all
local discovery attempts fail (see below).
b. MUST: Performs DNS-based Service Discovery [RFC6763] over
Multicast DNS [RFC6762] searching for the service
"_bootstrapks._tcp.local.". To prevent unaccceptable levels of
network traffic the congestion avoidance mechanisms specified in
[RFC6762] section 7 MUST be followed. The Pledge SHOULD listen
for an unsolicited broadcast response as described in [RFC6762].
This allows devices to avoid announcing their presence via mDNS
broadcasts and instead silently join a network by watching for
periodic unsolicited broadcast responses.
c. MAY: Performs DNS-based Service Discovery [RFC6763] over normal
DNS operations. The service searched for is
"_bootstrapks._tcp.example.com". In this case the domain
"example.com" is discovered as described in [RFC6763] section 11.
d. MAY: If no local bootstrapks service is located using the DNS- b. MUST: Listen for GRASP M_FLOOD ([I-D.ietf-anima-grasp])
based Service Discovery methods the Pledge contacts a well known announcements of the objective: "ACP+Proxy". See section
vendor provided bootstrapping server by performing a DNS lookup Section 5 for the details of the the objective. The Pledge may
using a well known URI such as "bootstrapks.vendor-example.com". listen concurrently for other sources of information, see
The details of the URI are vendor specific. Vendors that Appendix B.
leverage this method on the Pledge are responsible for providing
the bootstrapks service.
DNS-based service discovery communicates the local proxy IPv4 or IPv6 Once a proxy is discovered the Pledge communicates with a Registrar
address and port to the Pledge. Once a proxy is discovered the through the proxy using the bootstrapping protocol defined in
Pledge communicates with a Registrar through the proxy using the Section 7.
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 Pledge 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 doesn't work then the second and
third responses are tried. If these fail the Pledge moves on to
normal DNS-based Service Discovery.
Each discovery method attempted SHOULD exponentially back-off Each discovery method attempted SHOULD exponentially back-off
attempts (to a maximum of one hour) to avoid overloading the network attempts (to a maximum of one hour) to avoid overloading the network
infrastructure with discovery. The back-off timer for each method infrastructure with discovery. The back-off timer for each method
MUST be independent of other methods. Methods SHOULD be run in MUST be independent of other methods. Methods SHOULD be run in
parallel to avoid head of queue problems. Once a connection to a parallel to avoid head of queue problems. Once a connection to a
Registrar is established (e.g. establishment of a TLS session key) Registrar is established (e.g. establishment of a TLS session key)
there are expectations of more timely responses, see Section 5.1. there are expectations of more timely responses, see Section 7.1.
Once all discovered services are attempted the device SHOULD return Once all discovered services are attempted the device SHOULD return
to Multicast DNS. It should periodically retry the vendor specific to listening for GRASP M_FLOOD. It should periodically retry the
mechanisms. The Pledge may prioritize selection order as appropriate vendor specific mechanisms. The Pledge MAY prioritize selection
for the anticipated environment. order as appropriate for the anticipated environment.
3.1.2. Identity 3.1.2. Identity
The Pledge identifies itself during the communication protocol The Pledge identifies itself during the communication protocol
handshake. If the client identity is rejected the Pledge repeats the handshake. If the client identity is rejected (that is, the TLS
Discovery process using the next proxy or discovery method available. handshake does not complete) the Pledge repeats the Identity process
using the next proxy or discovery method available.
The bootstrapping protocol server is not initially authenticated. The bootstrapping protocol server is not initially authenticated.
Thus the connection is provisional and all data received is untrusted Thus the connection is provisional and all data received is untrusted
until sufficiently validated even though it is over a TLS connection. until sufficiently validated even though it is over a TLS connection.
This is aligned with the existing provisional mode of EST [RFC7030] This is aligned with the existing provisional mode of EST [RFC7030]
during s4.1.1 "Bootstrap Distribution of CA Certificates". See during s4.1.1 "Bootstrap Distribution of CA Certificates". See
Section 5.3 for more information about when the TLS connection Section 7.3 for more information about when the TLS connection
authenticated is completed. authentication is completed.
All security associations established are between the new device and All security associations established are between the new device and
the Bootstrapping server regardless of proxy operations. the Bootstrapping server regardless of proxy operations.
3.1.2.1. Concurrent attempts to join
The Pledge MAY attempt multiple mechanisms concurrently, but if it
does so, it MUST wait in the provisional state until all mechanisms
have either succeeded or failed, and then MUST proceed with the
highest priority mechanism which has succeed. To proceed beyond this
point, specifically, to provide a nonce, could result in the MASA
gratuitously auditing a connection.
3.1.3. Request Join 3.1.3. Request Join
The Pledge POSTs a request to join the domain to the Bootstrapping The Pledge POSTs a request to join the domain to the Bootstrapping
server. This request contains a Pledge generated nonce and informs server. This request contains a Pledge generated nonce and informs
the Bootstrapping server which imprint methods the Pledge will the Bootstrapping server which imprint methods the Pledge will
accept. 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 Pledge has resorted to a well known vendor URI and is
communicating with the vendor's Registrar directly. In this case the
Pledge has authenticated the Registrar using the local Implicit 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 Pledge can verify that responses are specific The nonce ensures the Pledge can verify that responses are specific
to this bootstrapping attempt. This minimizes the use of global time to this bootstrapping attempt. This minimizes the use of global time
and provides a substantial benefit for devices without a valid clock. and provides a substantial benefit for devices without a valid clock.
3.1.4. Imprint 3.1.3.1. Redirects during the Join Process
The domain trust anchor is received by the Pledge during the
bootstrapping protocol methods in the form of a 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 autonomic methods that MUST be supported by
the Pledge:
Audit Voucher Audit Vouchers are obtained by a Registrar from the
MASA service and presented to the Pledge for validation. These
indicate to the Pledge that joining the domain has been logged by
a logging service.
Ownership Voucher Ownership Vouchers are obtained by a Registrar
from the MASA service and explicitly indicate the owner of the
Pledge. The Ownership Voucher is defined in
[I-D.ietf-netconf-zerotouch].
Since client authentication occurs during the TLS handshake the EST [RFC7030] describes situations where the bootstrapping server MAY
bootstrapping server has sufficient information to apply appropriate redirect the client to an alternate server via a 3xx status code.
policy concerning which method to use. Such redirects MAY be accepted if the pledge has used the methods
described in Appendix B, in combination with an implicit trust
anchor. Redirects during the provisional period are otherwise
unstrusted, and MUST cause a failure.
The Audit Voucher contains the domain's public key material as 3.1.4. Imprint
provided to the MASA service by a Registrar. This provides
sufficient information to the client to complete automated
bootstrapping with the local key infrastructure. The Ownership
Voucher contains the Owner Certificate which the Pledge uses to
authenticate the TLS connection.
If the autonomic methods fail the Pledge returns to discovery state The Pledge validates the voucher and accepts the Registrar ID. The
and attempts bootstrapping with the next available discovered provisional TLS connection is validated using the Registrar ID from
Registrar. the voucher.
3.1.5. Lack of realtime clock 3.1.5. Lack of realtime clock
Many devices when bootstrapping do not have knowledge of the current Many devices when bootstrapping do not have knowledge of the current
time. Mechanisms like Network Time Protocols can not be secured time. Mechanisms like Network Time Protocols can not be secured
until bootstrapping is complete. Therefore bootstrapping is defined until bootstrapping is complete. Therefore bootstrapping is defined
in a method that does not require knowledge of the current time. in a method that does not require knowledge of the current time.
Unfortunately there are moments during bootstrapping when Unfortunately there are moments during bootstrapping when
certificates are verified, such as during the TLS handshake, where certificates are verified, such as during the TLS handshake, where
skipping to change at page 17, line 13 skipping to change at page 19, line 40
resolved by the Pledge maintaining a concept of the current "window" resolved by the Pledge maintaining a concept of the current "window"
of presumed time validity that is continually refined throughout the of presumed time validity that is continually refined throughout the
bootstrapping process as follows: bootstrapping process as follows:
o Initially the Pledge does not know the current time. o Initially the Pledge does not know the current time.
o During Pledge authentiation by the Registrar a realtime clock can o During Pledge authentiation by the Registrar a realtime clock can
be used by the Registrar. This bullet expands on a closely be used by the Registrar. This bullet expands on a closely
related issue regarding Pledge lifetimes. RFC5280 indicates that related issue regarding Pledge lifetimes. RFC5280 indicates that
long lived Pledge certifiates "SHOULD be assigned the long lived Pledge certifiates "SHOULD be assigned the
GeneralizedTime value of 99991231235959Z" [RFC5280] so the GeneralizedTime value of 99991231235959Z" [RFC7030] so the
Registrar MUST support such lifetimes and SHOULD support ignoring Registrar MUST support such lifetimes and SHOULD support ignoring
Pledge lifetimes if they did not follow the RFC5280 Pledge lifetimes if they did not follow the RFC5280
recommendations. recommendations.
o Once the Audit Voucher is accepted the validity period of the o The Pledge authenticates the voucher presented to it. During this
domainCAcert in the voucher (see Section 5.3) now describes a authentication the Pledge ignores certificate lifetimes (by
necessity because it does not have a clock). The voucher itself
SHOULD contain the nonce included in the original request which
proves the voucher is fresh.
o Once the voucher is accepted the validity period of the
domainCAcert in the voucher (see Section 7.3) now serves as a
valid time window. Any subsequent certificate validity periods valid time window. Any subsequent certificate validity periods
checked during RFC5280 path validation MUST occur within this checked during RFC5280 path validation MUST occur within this
window. window.
o When accepting an enrollment certificate the validity period o When accepting an enrollment certificate the validity period
within the new certificate is assumed to be valid by the Pledge. within the new certificate is assumed to be valid by the Pledge.
The Pledge is now willing to use this credential for client The Pledge is now willing to use this credential for client
authentication. authentication.
Once in this state the Pledge has a valid trust anchor with the local
domain and has a locally issued credential. These MAY be used to
secure distribution of more accurate time information although
specification of such a protocol is out-of-scope of this document.
The nonce included in join attempts provides an alternate mechanism
for the Pledge to ensure Audit Voucher responses are associated with
a particular bootstrapping attempt. Nonceless Audit Vouchers from
the MASA server are always valid and thus time is not needed.
Ownership Vouchers include time information and MUST be validated
using a realtime clock.
3.1.6. Enrollment 3.1.6. Enrollment
As the final step of bootstrapping a Registrar helps to issue a As the final step of bootstrapping a Registrar helps to issue a
domain specific credential to the Pledge. For simplicity in this domain specific credential to the Pledge. For simplicity in this
document, a Registrar primarily facilitates issuing a credential by document, a Registrar primarily facilitates issuing a credential by
acting as an RFC5280 Registration Authority for the Domain acting as an RFC5280 Registration Authority for the Domain
Certification Authority. Certification Authority.
Enrollment proceeds as described in [RFC7030]. Authentication of the Enrollment proceeds as described in [RFC7030]. Authentication of the
EST server is done using the Voucher rather than the methods defined EST server is done using the Voucher rather than the methods defined
in EST. in EST.
Once the Audit or Ownership Voucher is received, as specified in this Once the Voucher is received, as specified in this document, the
document, the client has sufficient information to leverage the client has sufficient information to leverage the existing
existing communication channel with a Registrar to continue an EST communication channel with a Registrar to continue an EST RFC7030
RFC7030 enrollment. Enrollment picks up at RFC7030 section 4.1.1. enrollment. Enrollment picks up at RFC7030 section 4.1.1.
bootstrapping where the Audit Voucher provides the "out-of-band" CA bootstrapping where the Voucher provides the "out-of-band" CA
certificate fingerprint (in this case the full CA certificate) such certificate fingerprint (in this case the full CA certificate) such
that the client can now complete the TLS server authentication. At that the client can now complete the TLS server authentication. At
this point the client continues with EST enrollment operations this point the client continues with EST enrollment operations
including "CA Certificates Request", "CSR Attributes" and "Client including "CA Certificates Request", "CSR Attributes" and "Client
Certificate Request" or "Server-Side Key Generation". Certificate Request" or "Server-Side Key Generation".
For the purposes of creating the ANIMA Autonomic Control Plane, the
contents of the new certificate MUST be carefully specified.
[I-D.ietf-anima-autonomic-control-plane] section 5.1.1 contains
details. The Registrar MUST provide the the correct ACP information
to populate the subjectAltName / rfc822Name field in the "CSR
Attributes" step.
3.1.7. Being Managed 3.1.7. Being Managed
Functionality to provide generic "configuration" information is Functionality to provide generic "configuration" information is
supported. The parsing of this data and any subsequent use of the supported. The parsing of this data and any subsequent use of the
data, for example communications with a Network Management System is data, for example communications with a Network Management System is
out of scope but is expected to occur after bootstrapping enrollment out of scope but is expected to occur after bootstrapping enrollment
is complete. This ensures that all communications with management is complete. This ensures that all communications with management
systems which can divulge local security information (e.g. network systems which can divulge local security information (e.g. network
topology or raw key material) is secured using the local credentials topology or raw key material) is secured using the local credentials
issued during enrollment. issued during enrollment.
The Pledge uses bootstrapping to join only one domain. Management by The Pledge uses bootstrapping to join only one domain. Management by
multiple domains is out-of-scope of bootstrapping. After the device multiple domains is out-of-scope of bootstrapping. After the device
has successfully joined a domain and is being managed it is plausible has successfully joined a domain and is being managed it is plausible
that the domain can insert credentials for other domains depending on that the domain can insert credentials for other domains depending on
the device capabilities. the device capabilities.
See Section 3.5. See Section 3.5.
3.2. Behavior of a Proxy 3.2. Behavior of a Join Proxy
The role of the Proxy is to facilitate communications. The Proxy The role of the Proxy is to facilitate communications. The Proxy
forwards packets between the Pledge and a Registrar that has been forwards packets between the Pledge and a Registrar that has been
configured on the Proxy. The Proxy does not terminate the TLS configured on the Proxy.
handshake. A Proxy is always assumed even if directly integrated
into a Registrar. The Proxy does not terminate the TLS handshake.
A Proxy is always assumed even if it is directly integrated into a
Registrar. (In a completely autonomic network, the Registrar MUST
provide proxy functionality so that it can be discovered, and the
network can grow concentrically around the Registrar)
As a result of the Proxy Discovery process in section Section 3.1.1, As a result of the Proxy Discovery process in section Section 3.1.1,
the port number exposed by the proxy does not need to be well known, the port number exposed by the proxy does not need to be well known,
or require an IANA allocation. or require an IANA allocation.
If the Proxy joins an Autonomic Control Plane If the Proxy joins an Autonomic Control Plane
([I-D.ietf-anima-autonomic-control-plane]) it SHOULD use Autonomic ([I-D.ietf-anima-autonomic-control-plane]) it SHOULD use Autonomic
Control Plane secured GRASP ([I-D.ietf-anima-grasp]) to discovery the Control Plane secured GRASP ([I-D.ietf-anima-grasp]) to discovery the
Registrar address and port. For the IPIP encapsulation methods, the Registrar address and port. As part of the discovery process, the
port announced by the Proxy MUST be the same as on the registrar in proxy mechanism (Circuit Proxy vs IPIP encapsulation) is agreed to
order for the proxy to remain stateless. between the Registrar and Join Proxy.
For the IPIP encapsulation methods, the port announced by the Proxy
MUST be the same as on the registrar in order for the proxy to remain
stateless.
In order to permit the proxy functionality to be implemented on the In order to permit the proxy functionality to be implemented on the
maximum variety of devices the chosen mechanism SHOULD use the maximum variety of devices the chosen mechanism SHOULD use the
minimum amount of state on the proxy device. While many devices in minimum amount of state on the proxy device. While many devices in
the ANIMA target space will be rather large routers, the proxy the ANIMA target space will be rather large routers, the proxy
function is likely to be implemented in the control plane CPU such a function is likely to be implemented in the control plane CPU of such
device, with available capabilities for the proxy function similar to a device, with available capabilities for the proxy function similar
many class 2 IoT devices. to many class 2 IoT devices.
The document [I-D.richardson-anima-state-for-joinrouter] provides a The document [I-D.richardson-anima-state-for-joinrouter] provides a
more extensive analysis of the alternative proxy methods. more extensive analysis of the alternative proxy methods.
3.2.1. CoAP connection to Registrar 3.2.1. CoAP connection to Registrar
The proxy MUST implement an IPIP (protocol 41) encapsulation function The CoAP mechanism was depreciated.
for CoAP traffic to the configured UDP port on the registrar. The
proxy does not terminate the CoAP DTLS connection. [[EDNOTE: The
choice of CoAP as the mandatory to implement protocol rather than
HTTP maximizes code reuse on the smallest of devices. Unfortunately
this means this document will have to include the EST over CoAP
details as additional sections. The alternative is to make 'HTTPS
proxy' method the mandatory to implement and provide a less friendly
environment for the smallest of devices. This is a decision we'll
have to see addressed by the broader team.]]
The IPIP encapsulation allows the proxy to forward traffic which is
otherwise not to be forwarded, as the traffic between New Node and
Proxy use IPv6 Link Local addresses.
If the Proxy device has more than one interface on which it offers
the proxy function, then it must select a unique (ACP) IP address per
interface in order so that the proxy can stateless return the (link-
local) reply packets to the correct link.
3.2.2. HTTPS proxy connection to Registrar 3.2.2. HTTPS proxy connection to Registrar
The proxy SHOULD also provide one of: an IPIP encapsulation of HTTP The proxy SHOULD also provide one of: an IPIP encapsulation of HTTP
traffic on TCP port TBD to the registrar, or a TCP circuit proxy that traffic on TCP port TBD to the registrar, or a TCP circuit proxy that
connects the Pledge to a Registrar. connects the Pledge to a Registrar.
When the Proxy provides a circuit proxy to a Registrar the Registrar When the Proxy provides a circuit proxy to a Registrar the Registrar
MUST accept HTTPS connections. MUST accept HTTPS connections.
skipping to change at page 20, line 26 skipping to change at page 22, line 42
[RFC5660], except that a simple IPIP tunnel is used rather than an [RFC5660], except that a simple IPIP tunnel is used rather than an
IPsec tunnel). IPsec tunnel).
3.3. Behavior of the Registrar 3.3. Behavior of the Registrar
A Registrar listens for Pledges and determines if they can join the A Registrar listens for Pledges and determines if they can join the
domain. A Registrar obtains a Voucher from the MASA service and domain. A Registrar obtains a Voucher from the MASA service and
delivers them to the Pledge as well as facilitating enrollment with delivers them to the Pledge as well as facilitating enrollment with
the domain PKI. the domain PKI.
A Registrar is typically configured manually. If the Registrar joins A Registrar is typically configured manually. When the Registrar
an Autonomic Control Plane ([I-D.ietf-anima-autonomic-control-plane]) joins an Autonomic Control Plane
it MUST use Autonomic Control Plane secured GRASP ([I-D.ietf-anima-autonomic-control-plane]) it MUST respond to GRASP
([I-D.ietf-anima-grasp]) to broadcast the Registrar's address and ([I-D.ietf-anima-grasp]) M_DISCOVERY message. See Section 6
port to potential Proxies.
Registrar behavior is as follows: Registrar behavior is as follows:
Contacted by Pledge Contacted by Pledge
+ +
| |
+-------v----------+ +-------v----------+
| Entity | fail? | Entity | fail?
| Authentication +---------+ | Authentication +---------+
+-------+----------+ | +-------+----------+ |
skipping to change at page 21, line 30 skipping to change at page 23, line 30
| Entity +---------> | Entity +--------->
+-------+----------+ | +-------+----------+ |
| | | |
+-------v----------+ | +-------v----------+ |
| Log Verification | fail? | | Log Verification | fail? |
| +---------> | +--------->
+-------+----------+ | +-------+----------+ |
| | | |
+-------v----------+ +----v-------+ +-------v----------+ +----v-------+
| Forward | | | | Forward | | |
| Audit | | Reject | | Voucher | | Reject |
| voucher + config | | Device | | to the Pledge | | Device |
| to the Entity | | | | | | |
+------------------+ +------------+ +------------------+ +------------+
Figure 4 Figure 4
3.3.1. Pledge Authentication 3.3.1. Pledge Authentication
The applicable authentication methods detailed in EST [RFC7030] are: The applicable authentication methods detailed in EST [RFC7030] are:
o the use of an IDevID X.509 credential during the TLS client o the use of an X.509 IDevID credential during the TLS client
authentication, authentication,
o or the use of a secret that is transmitted out of band between the o or the use of a secret that is transmitted out of band between the
Pledge and a Registrar (this use case is not autonomic). Pledge and a Registrar (this use case is not autonomic).
In order to validate the IDevID X.509 credential a Registrar In order to validate the X.509 IDevID credential a Registrar
maintains a database of vendor trust anchors (e.g. vendor root maintains a database of vendor trust anchors (e.g. vendor root
certificates or keyIdentifiers for vendor root public keys). For certificates or keyIdentifiers for vendor root public keys). For
user interface purposes this database can be mapped to colloquial user interface purposes this database can be mapped to colloquial
vendor names. Registrars can be shipped with the trust anchors of a vendor names. Registrars can be shipped with the trust anchors of a
significant number of third-party vendors within the target market. significant number of third-party vendors within the target market.
3.3.2. Pledge Authorization 3.3.2. Pledge Authorization
In a fully automated network all devices must be securely identified In a fully automated network all devices must be securely identified
and authorized to join the domain. and authorized to join the domain.
skipping to change at page 22, line 22 skipping to change at page 24, line 22
criteria include: criteria include:
o allow any device of a specific type (as determined by the X.509 o allow any device of a specific type (as determined by the X.509
IDevID), IDevID),
o allow any device from a specific vendor (as determined by the o allow any device from a specific vendor (as determined by the
X.509 IDevID), X.509 IDevID),
o allow a specific device from a vendor (as determined by the X.509 o allow a specific device from a vendor (as determined by the X.509
IDevID) against a domain white list. (The mechanism for checking IDevID) against a domain white list. (The mechanism for checking
a shared white list potentiatlly used by multiple Registrars is a shared white list potentially used by multiple Registrars is out
out of scope). of scope).
To look the Pledge up in a domain white list a consistent method for To look the Pledge up in a domain white list a consistent method for
extracting device identity from the X.509 certificate is required. extracting device identity from the X.509 certificate is required.
RFC6125 describes Domain-Based Application Service identity but here RFC6125 describes Domain-Based Application Service identity but here
we require Vendor Device-Based identity. The subject field's DN we require Vendor Device-Based identity. The subject field's DN
encoding MUST include the "serialNumber" attribute with the device's encoding MUST include the "serialNumber" attribute with the device's
unique serial number. In the language of RFC6125 this provides for a unique serial number. In the language of RFC6125 this provides for a
SERIALNUM-ID category of identifier that can be included in a SERIALNUM-ID category of identifier that can be included in a
certificate and therefore that can also be used for matching certificate and therefore that can also be used for matching
purposes. The SERIALNUM-ID whitelist is collated according to vendor purposes. The SERIALNUM-ID whitelist is collated according to vendor
trust anchor since serial numbers are not globally unique. trust anchor since serial numbers are not globally unique.
Since all Pledges accept Audit Vouchers a Registrar MUST use the The Registrar MUST use the vendor provided MASA service to verify
vendor provided MASA service to verify that the device's history log that the device's history log does not include unexpected Registrars.
does not include unexpected Registrars. If a device had previously If a device had previously registered with another domain, a
registered with another domain, a Registrar of that domain would show Registrar of that domain would show in the log.
in the log.
If a Pledge is accepted into the domain, it is expected to request a The authorization performed during BRSKI MAY be used for EST
domain certificate through a certificate enrollment process. The enrollment requests by proceeding with EST enrollment using the
result is a common trust anchor and device certificates for all authenticated and authorized TLS connection. This minimizes the
autonomic devices in a domain (these certificates can be used for number of cryptographic and protocol operations necessary to complete
other methods, for example boundary detection, auto-securing bootstraping of the local key infrastructure.
protocols, etc.). The authorization performed during this phase is
used for EST enrollment requests.
3.3.3. Claiming the New Entity 3.3.3. Claiming the New Entity
Claiming an entity establishes an audit log at the MASA server and Claiming an entity establishes an audit log at the MASA server and
provides a Registrar with proof, in the form of a MASA Audit Voucher, provides a Registrar with proof, in the form of the Voucher, that the
that the log entry has been inserted. As indicated in Section 3.1.4 log entry has been inserted. As indicated in Section 3.1.4 a Pledge
a Pledge will only proceed with bootstrapping if a validated MASA will only proceed with bootstrapping if a Voucher has been received.
Audit Voucher has been received. The Pledge therefore enforces that
bootstrapping only occurs if the claim has been logged. There is no
requirement for the vendor to definitively know that the device is
owned by the Registrar.
Registrar's obtain the Vendor URI via static configuration or by The Pledge therefore enforces that bootstrapping only occurs if the
extracting it from the X.509 IDevID credential. The imprint method claim has been logged. There is no requirement for the vendor to
supported by the Pledge is known from the X.509 IDevID credential. definitively know that the device is owned by the Registrar.
[[EDNOTE: An appropriate extension for indicating the Vendor URI and
imprint method could be defined using the methods described in The Registrar obtains the MASA URI via static configuration or by
[I-D.lear-mud-framework]]]. extracting it from the X.509 IDevID credential. See Section 2.3.
During initial bootstrapping the Pledge provides a nonce specific to During initial bootstrapping the Pledge provides a nonce specific to
the particular bootstrapping attempt. The Registrar SHOULD include the particular bootstrapping attempt. The Registrar SHOULD include
this nonce when claiming the Pledge from the MASA service. Claims this nonce when claiming the Pledge from the MASA service. Claims
from an unauthenticated Registrar are only serviced by the MASA from an unauthenticated Registrar are only serviced by the MASA
resource if a nonce is provided. resource if a nonce is provided.
The Registrar can claim a Pledge that is not online by forming the The Registrar can claim a Pledge that is not online by forming the
request using the entities unique identifier and not including a request using the entities unique identifier and not including a
nonce in the claim request. Audit Voucher obtained in this way do nonce in the claim request. Vouchers obtained in this way do not
not have a lifetime and they provide a permanent method for the have a lifetime and they provide a permanent method for the domain to
domain to claim the device. Evidence of such a claim is provided in claim the device. Evidence of such a claim is provided in the audit
the audit log entries available to any future Registrar. Such claims log entries available to any future Registrar. Such claims reduce
reduce the ability for future domains to secure bootstrapping and the ability for future domains to secure bootstrapping and therefore
therefore the Registrar MUST be authenticated by the MASA service the Registrar MUST be authenticated by the MASA service although no
although no requirement is implied that the MASA associates this requirement is implied that the MASA associates this authentication
authentication with ownership. with ownership.
An Ownership Voucher requires the vendor to definitively know that a An Ownership Voucher requires the vendor to definitively know that a
device is owned by a specific domain. The method used to "claim" device is owned by a specific domain. The method used to "claim"
this are out-of-scope. A MASA ignores or reports failures when an this are out-of-scope. A MASA ignores or reports failures when an
attempt is made to claim a device that has a an Ownership Voucher. attempt is made to claim a device that has a an Ownership Voucher.
3.3.4. Log Verification 3.3.4. Log Verification
A Registrar requests the log information for the Pledge from the MASA A Registrar requests the log information for the Pledge from the MASA
service. The log is verified to confirm that the following is true service. The log is verified to confirm that the following is true
skipping to change at page 24, line 16 skipping to change at page 26, line 7
have physical possession of the Pledge or that the domainIDs are have physical possession of the Pledge or that the domainIDs are
recognized by the registrar. recognized by the registrar.
If any of these criteria are unacceptable to a Registrar the entity If any of these criteria are unacceptable to a Registrar the entity
is rejected. A Registrar MAY be configured to ignore the history of is rejected. A Registrar MAY be configured to ignore the history of
the device but it is RECOMMENDED that this only be configured if the device but it is RECOMMENDED that this only be configured if
hardware assisted NEA [RFC5209] is supported. hardware assisted NEA [RFC5209] is supported.
This document specifies a simple log format as provided by the MASA This document specifies a simple log format as provided by the MASA
service to the registar. This format could be improved by service to the registar. This format could be improved by
distributed consensus technologies that integrate the Audit Voucher distributed consensus technologies that integrate vouchers with a
with a current technologies such as block-chain or hash trees or the technologies such as block-chain or hash trees or the like. Doing so
like. Doing so is out of the scope of this document but are is out of the scope of this document but are anticipated improvements
anticipated improvements for future work. for future work.
3.4. Behavior of the MASA Service 3.4. Behavior of the MASA Service
The MASA service is provided by the Factory provider on the global The Manufacturer Authorized Signing Authority service is directly
Internet. The URI of this service is well known. The URI SHOULD provided by the manufacturer, or can be provided by a third party the
also be provided as an X.509 IDevID extension (a "MASA Audit Voucher manufacturer authorizes. It is a cloud resource. The MASA service
Distribution Point" extension). provides the following functionalities to Registrars:
The MASA service provides the following functionalities to
Registrars:
3.4.1. Issue Audit Voucher 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 service responds to all requests.
The MASA service verifies the Registrar is representative of the
domain and generates a privacy protected log entry before responding
with the Audit Voucher. For the simple log format defined in this
document using the DomainID is considered sufficient privacy. Future
work to improve the logging mechanism could include additional
privacy protections.
If a nonce is not provided then the MASA service MUST authenticate Issue Vouchers: In response to Registrar requests the MASA service
the Registrar as a valid customer. This prevents denial of service issues vouchers. Depending on the MASA policy the Registrar claim
attacks. of device ownership is either accepted or verified using out-of-
scope methods (that are expected to improve over time).
3.4.2. Retrieve Audit Entries from Log Log Vouchers Issued: When a voucher is issued the act of issuing it
includes updating the certifiable logs. Future work to enhance
and distribute these logs is out-of-scope but expected over time.
When determining if a Pledge should be accepted into a domain the Provide Logs: As a baseline implementation of the certified logging
Registrar retrieves a copy of the audit log from the MASA service. mechanism the MASA is repsonsible for reporting logged
This contains a list of privacy protected domain identities that have information. The current method involves trusting the MASA.
previously claimed the device. Included in the list is an indication Other logging methods where the MASA is less trusted are expected
of the time the entry was made and if the nonce was included. to be developed over time.
3.5. Leveraging the new key infrastructure / next steps 3.5. Leveraging the new key infrastructure / next steps
As the devices have a common trust anchor, device identity can be As the devices have a common trust anchor, device identity can be
securely established, making it possible to automatically deploy securely established, making it possible to automatically deploy
services across the domain in a secure manner. services across the domain in a secure manner.
Examples of services: Examples of services:
o Device management. o Device management.
skipping to change at page 28, line 5 skipping to change at page 29, line 27
subsequent operations. For example, to determine the boundaries of subsequent operations. For example, to determine the boundaries of
the domain: If a neighbor has a certificate from the same trust the domain: If a neighbor has a certificate from the same trust
anchor it can be assumed "inside" the same organization; if not, as anchor it can be assumed "inside" the same organization; if not, as
outside. See also Section 3.5.1. The certificate can also be used outside. See also Section 3.5.1. The certificate can also be used
to securely establish a connection between devices and central to securely establish a connection between devices and central
control functions. Also autonomic transactions can use the domain control functions. Also autonomic transactions can use the domain
certificates to authenticate and/or encrypt direct interactions certificates to authenticate and/or encrypt direct interactions
between devices. The usage of the domain certificates is outside between devices. The usage of the domain certificates is outside
scope for this document. scope for this document.
5. Protocol Details 5. Proxy Discovery Protocol Details
The proxy uses the GRASP M_FLOOD mechanism to announce itself. This
announcement is done with the same message as the ACP announcement
detailed in [I-D.ietf-anima-autonomic-control-plane].
proxy-objective = ["Proxy", [ O_IPv6_LOCATOR, ipv6-address,
transport-proto, port-number ] ]
ipv6-address - the v6 LL of the proxy
transport-proto - 6, for TCP 17 for UDP
port-number - the TCP or UDP port number to find the proxy
Figure 5
6. Registrar Discovery Protocol Details
The registrar responds to discovery messages from the proxy (or GRASP
caches between them) as follows: (XXX changed from M_DISCOVERY)
objective = ["AN_registrar", F_DISC, 255 ]
discovery-message = [M_NEG_SYN, session-id, initiator, objective]
Figure 6: Registrar Discovery
The response from the registrar (or cache) will be a M_RESPONSE with
the following parameters:
response-message = [M_RESPONSE, session-id, initiator, ttl,
(+locator-option // divert-option), ?objective)]
initiator = ACP address of Registrar
locator1 = [O_IPv6_LOCATOR, fd45:1345::6789, 6, 443]
locator2 = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683]
locator3 = [O_IPv6_LOCATOR, fe80::1234, 41, nil]
Figure 7: Registrar Response
The set of locators is to be interpreted as follows. A protocol of 6
indicates that TCP proxying on the indicated port is desired. A
protocol of 17 indicates that UDP proxying on the indicated port is
desired. In each case, the traffic SHOULD be proxied to the same
port at the ULA address provided.
A protocol of 41 indicates that packets may be IPIP proxy'ed. The
address in the locator In the case of that IPIP proxying is used,
then the provided link-local address MUST be advertised on the local
link using proxy neighbour discovery. The Join Proxy MAY limit
forwarded traffic to the protocol (6 and 17) and port numbers
indicated by locator1 and locator2. The address to which the IPIP
traffic should be sent is the initiator address (an ACP address of
the Registrar), not the address given in the locator.
All Registrar MUST accept TCP / UDP traffic on the ports given at the
ACP address of the Registrar. If the Registrar supports IPIP
tunnelling, it MUST also accept traffic encapsulated with IPIP.
Registrars MUST accept HTTPS/EST traffic on the ports indicated.
Registrars MAY accept DTLS/CoAP/EST traffic in addition.
7. Protocol Details
A bootstrapping protocol could be implemented as an independent A bootstrapping protocol could be implemented as an independent
protocol from EST, but for simplicity and to reduce the number of TLS protocol from EST, but for simplicity and to reduce the number of TLS
connections and crypto operations required on the Pledge, it is connections and crypto operations required on the Pledge, it is
described specifically as extensions to EST. These extensions MUST described specifically as extensions to EST. These extensions MUST
be supported by the Registrar EST server within the same .well-known be supported by the Registrar EST server within the same .well-known
URI tree as the existing EST URIs as described in [RFC7030] section URI tree as the existing EST URIs as described in EST [RFC7030]
3.2.2. section 3.2.2.
The Pledge establishes a TLS connection with the Registrar through A MASA URI is therefore "https:// authority "./well-known/est". The
the circuit proxy (see Section 3.2) but the TLS connection is with portion contained in the IDevID extension is only
the Registar; so for this section the "Pledge" is the TLS client and "https://example.com" since everything after that is well known.
the "Registrar" is the TLS server.
Establishment of the TLS connection for bootstrapping is as specified Establishment of the TLS connection for bootstrapping is as specified
for EST [RFC7030]. In particular server identity and client identity for EST [RFC7030]. In particular server identity and client identity
are as described in EST [RFC7030] section 3.3. In EST [RFC7030] are as described in EST [RFC7030] section 3.3. In EST [RFC7030]
provisional server authentication for bootstrapping is described in provisional server authentication for bootstrapping is described in
section 4.1.1 wherein EST clients can "engage a human user to section 4.1.1 wherein EST clients can "engage a human user to
authorize the CA certificate using out-of-band data such as a CA authorize the CA certificate using out-of-band data such as a CA
certificate" or wherein a human user configures the URI of the EST certificate" or wherein a human user configures the URI of the EST
server for Implicit TA based authentication. As described in this server for Implicit TA based authentication. This documented
document, Section 5.3.1, a new method of bootstrapping now provides a establishes automated methods of authorizing the CA certificate using
completely automating method of bootstrapping PKI. in-band vouchers.
If the Pledge uses a well known URI for contacting a well known
Registrar the EST Implicit Trust Anchor database is used to
authenticate the well known URI. In this case the connection is not
provisional and RFC6125 methods can be used to authenticate the
Registrar
The Pledge establishes a TLS connection with the Registrar through
the circuit proxy (see Section 3.2) but the TLS connection is with
the Registar; so for this section the "Pledge" is the TLS client and
the "Registrar" is the TLS server.
The extensions for the Pledge client are as follows: The extensions for the Pledge client are as follows:
o The Pledge provisionally accept the EST server certificate during o The Pledge provisionally accept the EST server certificate during
the TLS handshake as detailed in Section 5.3.1. the TLS handshake as detailed in Section 7.3.1.
o The Pledge requests and validates the Audit Voucher as described o The Pledge requests and validates the Voucher as described below.
below. At this point the Pledge has sufficient information to At this point the Pledge has sufficient information to validate
validate domain credentials. domain credentials.
o The Pledge calls the EST defined /cacerts method to obtain the o The Pledge calls the EST defined /cacerts method to obtain the
current CA certificate. These are validated using the Audit current CA certificate. These are validated using the Voucher.
Voucher.
o The Pledge completes bootstrapping as detailed in EST section o The Pledge completes bootstrapping as detailed in EST section
4.1.1. 4.1.1.
In order to obtain a validated Audit Voucher and Audit Log a In order to obtain a Voucher and associated logs a Registrar contacts
Registrar contacts the MASA service Service using REST calls: the MASA service Service using REST calls:
+-----------+ +----------+ +-----------+ +----------+ +-----------+ +----------+ +-----------+ +----------+
| New | | Circuit | | | | | | New | | Circuit | | | | |
| Entity | | Proxy | | Registrar | | Vendor | | Entity | | Proxy | | Registrar | | Vendor |
| | | | | | | | | | | | | | | |
++----------+ +--+-------+ +-----+-----+ +--------+-+ ++----------+ +--+-------+ +-----+-----+ +--------+-+
| | | | | | | |
| | | | | | | |
| TLS hello | TLS hello | | | TLS hello | TLS hello | |
Establish +---------------C---------------> | Establish +---------------C---------------> |
skipping to change at page 29, line 33 skipping to change at page 32, line 33
| . +----------------> | . +---------------->
| <----------------+ | <----------------+
| | /requestlog | | | /requestlog |
| +----------------> | +---------------->
| voucher <----------------+ | voucher <----------------+
<-------------------------------+ | <-------------------------------+ |
| (optional config information) | | | (optional config information) | |
| . | | | . | |
| . | | | . | |
Figure 5 Figure 8
In some use cases the Registrar may need to contact the Vendor in In some use cases the Registrar may need to contact the Vendor in
advanced, for example when the target network is air-gapped. The advanced, for example when the target network is air-gapped. The
nonceless request format is provided for this and the resulting flow nonceless request format is provided for this and the resulting flow
is slightly different. The security differences associated with not is slightly different. The security differences associated with not
knowing the nonce are discussed below: knowing the nonce are discussed below:
+-----------+ +----------+ +-----------+ +----------+ +-----------+ +----------+ +-----------+ +----------+
| New | | Circuit | | | | | | New | | Circuit | | | | |
| Entity | | Proxy | | Registrar | | Vendor | | Entity | | Proxy | | Registrar | | Vendor |
skipping to change at page 30, line 33 skipping to change at page 33, line 33
| Client Cert | | | | Client Cert | | |
| | | | | | | |
HTTP REST | POST /requestvoucher | | HTTP REST | POST /requestvoucher | |
Data +----------------------nonce----> (discard | Data +----------------------nonce----> (discard |
| voucher | nonce) | | voucher | nonce) |
<-------------------------------+ | <-------------------------------+ |
| (optional config information) | | | (optional config information) | |
| . | | | . | |
| . | | | . | |
Figure 6 Figure 9
The extensions for a Registrar server are as follows: The extensions for a Registrar server are as follows:
o The Registrar requests and validates the Audit Voucher from the o The Registrar requests and validates the Voucher from the vendor
vendor authorized MASA service. authorized MASA service.
o The Registrar forwards the Audit Voucher to the Pledge when o The Registrar forwards the Voucher to the Pledge when requested.
requested.
o The Registar performs log verifications in addition to local o The Registar performs log verifications in addition to local
authorization checks before accepting the Pledge device. authorization checks before accepting the Pledge device.
5.1. Request Voucher from the Registrar The provisional TLS connection introduces security risks that are
addressed as follows:
If the Registrar provides a redirect response the Pledge MUST follow
the redirect but the connection remains provisional. The Pledge MUST
only follow a single redirection.
The Registar MAY respond with an HTTP 202 ("the request has been
accepted for processing, but the processing has not been completed")
as described in EST [RFC7030] section 4.2.3 wherein the client "MUST
wait at least the specified 'retry-after' time before repeating the
same request". The Pledge is RECOMMENDED to provide local feed
(blinked LED etc) during this wait cycle if mechanisms for this are
available. To prevent an attacker Registrar from significantly
delaying bootstrapping the Pledge MUST limit the 'retry-after' time
to 60 seconds. To avoid waiting on a single erroneous Registrar the
Pledge MUST drop the connection after 5 seconds and proceed to other
discovered Registrars. Ideally the Pledge could keep track of the
appropriate retry-after value for any number of outstanding
Registrars but this would involve a large state table on the Pledge.
Instead the Pledge MAY ignore the exact retry-after value in favor of
a single hard coded value that takes effect between discovery
(Section 3.1.1) attempts. A Registrar that is unable to complete the
transaction the first time due to timing reasons will have future
chances.
7.1. Request Voucher from the Registrar
When the Pledge bootstraps it makes a request for a Voucher from a When the Pledge bootstraps it makes a request for a Voucher from a
Registrar. Registrar.
This is done with an HTTPS POST using the operation path value of This is done with an HTTPS POST using the operation path value of
"/requestvoucher". "/requestvoucher".
The request format is JSON object containing a 64bit nonce generated The request format is JSON object containing a 64bit nonce generated
by the client for each request. This nonce MUST be a by the client for each request. This nonce MUST be a
cryptographically strong random or pseudo-random number that can not cryptographically strong random or pseudo-random number that can not
be easily predicted. The nonce MUST NOT be reused for multiple be easily predicted. The nonce MUST NOT be reused for multiple
attempts to join a network domain. The nonce assures the Pledge that attempts to join a network domain. The nonce assures the Pledge that
the Audit Voucher response is associated with this bootstrapping the Voucher response is associated with this bootstrapping attempt
attempt and is not a replay. and is not a replay.
Request media type: application/auditnonce Request media type: application/voucherrequest
Request format: a JSON file with the following: Request format: a JSON file with the following:
{ {
"version":"1", "version":"1",
"nonce":"<64bit nonce value>", "nonce":"<64bit nonce value>",
} }
[[EDNOTE: Even if the nonce was signed it would provide no defense [[EDNOTE: Even if the nonce was signed it would provide no defense
against rogue registrars; although it would assure the MASA that a against rogue registrars; although it would assure the MASA that a
skipping to change at page 31, line 37 skipping to change at page 35, line 15
authentications but it is worth exploring additional protections. authentications but it is worth exploring additional protections.
This to be explored more at IETF96.]] This to be explored more at IETF96.]]
The Registrar validates the client identity as described in EST The Registrar validates the client identity as described in EST
[RFC7030] section 3.3.2. The registrar performs authorization as [RFC7030] section 3.3.2. The registrar performs authorization as
detailed in Section 3.3.2. If authorization is successful the detailed in Section 3.3.2. If authorization is successful the
Registrar obtains an Voucher from the MASA service (see Section 5.2). Registrar obtains an Voucher from the MASA service (see Section 5.2).
The received Voucher is forwarded to the Pledge. The received Voucher is forwarded to the Pledge.
As indicated in EST [RFC7030] the bootstrapping server can redirect 7.2. Request Voucher from MASA
the client to an alternate server. If the Pledge authenticated a
Registrar using the well known URI method then the Pledge MUST follow
the redirect automatically and authenticate the new Registrar against
the redirect URI provided. If the Pledge had not yet authenticated a
Registrar because it was discovered and was not a known-to-be-valid
URI then the new Registrar must be authenticated using one of the two
autonomic methods described in this document. Similarly the Registar
MAY respond with an HTTP 202 ("the request has been accepted for
processing, but the processing has not been completed") as described
in EST [RFC7030] section 4.2.3.
Recall that during this communication with the Registar the TLS
authentication is only provisional. The Pledge client MUST handle
all data from the Registrar with upmost care. In particular the
Pledge MUST only allow a single redirection and MUST only support a
delay of five seconds before declaring the Registrar a failure and
moving on to the next discovered Registrar. As detailed in
Section 3.1.1 if no suitable Registrar is found the Pledge restarts
the state machine and tries again. So a Registrar that is unable to
complete the transaction the first time will have future chances.
5.2. Request Voucher from MASA
A Registrar requests a Voucher from the MASA service using a REST A Registrar requests a Voucher from the MASA service using a REST
interface. For simplicity this is defined as an optional EST message interface. For simplicity this is defined as an optional EST message
between a Registrar and an EST server running on the MASA service between a Registrar and an EST server running on the MASA service
although the Registrar is not required to make use of any other EST although the Registrar is not required to make use of any other EST
functionality when communicating with the MASA service. (The MASA functionality when communicating with the MASA service. (The MASA
service MUST properly reject any EST functionality requests it does service MUST properly reject any EST functionality requests it does
not wish to service; a requirement that holds for any REST not wish to service; a requirement that holds for any REST
interface). interface).
This is done with an HTTP POST using the operation path value of This is done with an HTTP POST using the operation path value of
"/requestvoucher". "/requestvoucher".
Request media type: application/voucherrequest+cms
The request format is a JSON object optionally containing the nonce The request format is a JSON object optionally containing the nonce
value (as obtained from the bootstrap request) and the X.509 IDevID value (as obtained from the bootstrap request) and the X.509 IDevID
extracted serial number (the full certificate is not needed and no extracted serial number (the full certificate is not needed and no
proof-of-possession information for the device identity is included). proof-of-possession information for the device identity is included).
The AuthorityKeyIdentifier value from the certificate is included to The AuthorityKeyIdentifier value from the certificate is included to
ensure a statistically unique identity. The Pledge's serial number ensure a statistically unique identity. The Pledge's serial number
is extracted from the X.509 IDevID subject name id-at-serialNumber or is extracted from the X.509 IDevID. See Section 2.3.
it is the base64 encoded RFC4108 hardwareModuleName hwSerialNum:
{ {
"version":"1", "version":"1",
"nonce":"<64bit nonce value>", "nonce":"<64bit nonce value>",
"IDevIDAuthorityKeyIdentifier":"<base64 encoded keyIdentifier">, "IDevIDAuthorityKeyIdentifier":"<base64 encoded keyIdentifier">,
"DevIDSerialNumber":"<id-at-serialNumber or base64 encoded "DevIDSerialNumber":"<id-at-serialNumber or base64 encoded
hardwareModuleName hwSerialNum>", hardwareModuleName hwSerialNum>",
} }
A Registrar MAY exclude the nonce from the request. Doing so allows A Registrar MAY exclude the nonce from the request. Doing so allows
the Registrar to request a Voucher when the Pledge is not online, or the Registrar to request a Voucher when the Pledge is not online, or
when the target bootstrapping environment is not on the same network when the target bootstrapping environment is not on the same network
as the MASA server (this requires the Registrar to learn the as the MASA server (this requires the Registrar to learn the
appropriate DevIDSerialNumber field from the physical device labeling appropriate DevIDSerialNumber field from the physical device labeling
or from the sales channel -- how this occurs is out-of-scope of this or from the sales channel -- how this occurs is out-of-scope of this
document). If a nonce is not provided the MASA server MUST document). If a nonce is not provided the MASA server MUST
authenticate the client as described in EST [RFC7030] section 3.3.2 authenticate the Registrar as described in EST [RFC7030] section
to reduce the risk of DDoS attacks. A Registrar performs 3.3.2 to reduce the risk of DDoS attacks. The MASA performs
authorization as detailed in Section 3.3.2. If authorization is authorization as detailed in Section 3.3.2.
successful the Registrar obtains an Voucher from the MASA service
(see Section 5.2).
The JSON message information is encapsulated in a [RFC5652] Signed- As described in [I-D.ietf-anima-voucher] vouchers are normally short
data that is signed by the Registrar. The entire certificate chain, lived to avoid revocation issues. If the request is for a previous
up to and including the Domain CA, MUST be included in the (expired) voucher using the same Registrar (as determined by
CertificateSet structure. The MASA service checks the internal domainID) and the MASA has not been informed that the claim is no
consistency of the CMS but does not authenticate the domain identity longer valid - the request for a renewed voucher SHOULD be
information. The domain is not know to the MASA server in advance automatically authorized. If authorization is successful the MASA
and a shared trust anchor is not implied. The MASA server MUST responds with a [I-D.ietf-anima-voucher] voucher. The MASA SHOULD
verify that the CMS is signed by a Registrar certificate (by checking check for revocation of the Registrar certificate. The maximum
for the cmc-idRA field) that was issued by a the root certificate lifetime of the voucher issued SHOULD NOT exceed the lifetime of the
included in the CMS. This ensures that the Registrar making the Registrar's revocation validation (for example if the Registrar
claim is an authorized Registrar of the unauthenticated domain. The revocation status is indicated in a CRL that is valid for two weeks
EST style client authentication (TLS and HTTP) is used to provide a then that is an appropriate lifetime for the voucher).
DDoS prevention strategy.
The root certificate is extracted and used to populate the Audit The voucher request is encapsulated in a [RFC5652] Signed-data that
Voucher. The domain ID (e.g. hash of the public key of the domain) is signed by the Registrar. The entire certificate chain, up to and
is extracted from the root certificate and is used to update the including the Domain CA, MUST be included in the CertificateSet
audit log. structure. The MASA service checks the internal consistency of the
CMS but does not 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 MUST verify that the CMS is
signed by a Registrar certificate (by checking for the cmc-idRA
field) that was issued by a the root certificate included in the CMS.
This ensures that the Registrar making the claim is an authorized
Registrar of the unauthenticated domain.
5.3. Audit Voucher Response The root certificate is extracted and used to populate the Voucher.
The domain ID (e.g. hash of the public key of the domain) is
extracted from the root certificate and is used to update the audit
log.
7.3. Voucher Response
The voucher response to requests from the device and requests from a The voucher response to requests from the device and requests from a
Registrar are in the same format. A Registrar either caches prior Registrar are in the same format. A Registrar either caches prior
MASA responses or dynamically requests a new Voucher based on local MASA responses or dynamically requests a new Voucher based on local
policy. policy.
If the the join operation is successful, the server response MUST If the the join operation is successful, the server response MUST
contain an HTTP 200 response code with a content-type of contain an HTTP 200 response code. The server MUST answer with a
"application/authorizationvoucher". The server MUST answer with a
suitable 4xx or 5xx HTTP [RFC2616] error code when a problem occurs. suitable 4xx or 5xx HTTP [RFC2616] error code when a problem occurs.
The response data from the MASA server MUST be a plaintext human- The response data from the MASA server MUST be a plaintext human-
readable error message containing explanatory information describing readable error message containing explanatory information describing
why the request was rejected. why the request was rejected.
The Audit Voucher consists of the nonce, if supplied, the serial Response media type: application/voucher+cms
number information identifying the device and the domain CA
certificate extracted from the request: The syntactic details of vouchers are described in detail in
[I-D.ietf-anima-voucher]. For example, the voucher consists of:
{ {
"version":"1", "version":"1",
"nonce":"<64bit nonce value>", "nonce":"<64bit nonce value>",
"IDevIDAuthorityKeyIdentifier":"<base64 encoded keyIdentifier>", "IDevIDAuthorityKeyIdentifier":"<base64 encoded keyIdentifier>",
"DevIDSerialNumber":"<id-at-serialNumber>", "DevIDSerialNumber":"<id-at-serialNumber>",
"domainCAcert":"<the base64 encoded domain CA's certificate>" "domainCAcert":"<the base64 encoded domain CA's certificate>"
} }
The Audit Voucher response is encapsulated in a [RFC5652] Signed-data
that is signed by the MASA server. The Pledge verifies this signed The Voucher response is encapsulated in a [RFC5652] Signed-data that
message using the manufacturer installed trust anchor assocaited with is signed by the MASA server. The Pledge verifies this signed
message using the manufacturer installed trust anchor associated with
the X.509 IDevID. [[EDNOTE: As detailed in netconf-zerotouch this the X.509 IDevID. [[EDNOTE: As detailed in netconf-zerotouch this
might be a distinct trust anchor rather than re-using the trust might be a distinct trust anchor rather than re-using the trust
anchor for the IDevID. This concept will need to be detailed in this anchor for the IDevID. This concept will need to be detailed in this
document as well.]] document as well.]]
[[EDNOTE: Using CMS is consistent with the alignment of this
bootstrapping document with EST, a PKIX enrollment protocol that
includes Certificate Management over CMS. An alternative format
would be the RFC7515 JSON Web Signature (JWS), which would allow
clients that do not use fullCMC messages to avoid CMS entirely. Use
of JWS would likely include a discussion of CBOR in order ensure the
base64 expansions of the certs and signatures within the JWS message
are of minimal size -- it is not yet clear to this author how that
would work out]]
The 'domainCAcert' element of this message contains the domain CA's The 'domainCAcert' element of this message contains the domain CA's
public key. This is specific to bootstrapping a public key public key. This is specific to bootstrapping a public key
infrastructure. To support bootstrapping other key infrastructures infrastructure. To support bootstrapping other key infrastructures
additional domain identity types might be defined in the future. additional domain identity types might be defined in the future.
Clients MUST be prepared to ignore additional fields they do not Clients MUST be prepared to ignore additional fields they do not
recognize. Clients MUST be prepared to parse and fail gracefully recognize. Clients MUST be prepared to parse and fail gracefully
from an Audit Voucher response that does not contain a 'domainCAcert' from an Voucher response that does not contain a 'domainCAcert' field
field at all. at all.
To minimize the size of the Audit Voucher response message the
domainCAcert is not a complete distribution of the EST section 4.1.3
CA Certificate Response.
The Pledge installs the domainCAcert trust anchor. As indicated in To minimize the size of the Voucher response message the domainCAcert
Section 3.1.2 the newly installed trust anchor is used as an EST is not a complete distribution of the EST section 4.1.3 CA
RFC7030 Explicit Trust Anchor. The Pledge MUST use the domainCAcert Certificate Response. The Pledge installs the domainCAcert trust
trust anchor to immediately validate the currently provisional TLS anchor. As indicated in Section 3.1.2 the newly installed trust
connection to a Registrar. anchor is used as an EST RFC7030 Explicit Trust Anchor. The Pledge
MUST use the domainCAcert trust anchor to immediately validate the
currently provisional TLS connection to a Registrar.
5.3.1. Completing authentication of Provisional TLS connection 7.3.1. Completing authentication of Provisional TLS connection
If a Registrar's credential can not be verified using the If a Registrar's credential can not be verified using the
domainCAcert trust anchor the TLS connection is immediately discarded domainCAcert trust anchor the TLS connection is immediately discarded
and the Pledge abandons attempts to bootstrap with this discovered and the Pledge abandons attempts to bootstrap with this discovered
registrar. registrar.
The following behaviors on a Registrar and Pledge are in addition to The following behaviors on a Registrar and Pledge are in addition to
normal PKIX operations: normal PKIX operations:
o The EST server MUST use a certificate that chains to the o The EST server MUST use a certificate that chains to the
domainCAcert. This means that when the EST server obtains renewed domainCAcert. This means that when the EST server obtains renewed
credentials the credentials included in the Section 5.2 request credentials the credentials included in the Section 7.2 request
match the chain used in the current provisional TLS connection. match the chain used in the current provisional TLS connection.
o The Pledge PKIX path validation of a Registrar validity period o The Pledge PKIX path validation of a Registrar validity period
information is as described in Section 3.1.5. information is as described in Section 3.1.5.
Because the domainCAcert trust anchor is installed as an Explicit Because the domainCAcert trust anchor is installed as an Explicit
Trust Anchor it can be used to authenticate any dynamically Trust Anchor it can be used to authenticate any dynamically
discovered EST server that contain the id-kp-cmcRA extended key usage discovered EST server that contain the id-kp-cmcRA extended key usage
extension as detailed in EST RFC7030 section 3.6.1; but to reduce extension as detailed in EST RFC7030 section 3.6.1; but to reduce
system complexity the Pledge SHOULD avoid additional discovery system complexity the Pledge SHOULD avoid additional discovery
operations. Instead the Pledge SHOULD communicate directly with the operations. Instead the Pledge SHOULD communicate directly with the
Registrar as the EST server to complete PKI local certificate Registrar as the EST server to complete PKI local certificate
enrollment. Additionally the Pledge SHOULD use the existing TLS enrollment. Additionally the Pledge SHOULD use the existing TLS
connection to proceed with EST enrollment, thus reducing the total connection to proceed with EST enrollment, thus reducing the total
amount of cryptographic and round trip operations required during amount of cryptographic and round trip operations required during
bootstrapping. [[EDNOTE: It is reasonable to mandate that the bootstrapping. [[EDNOTE: It is reasonable to mandate that the
existing TLS connection be re-used? e.g. MUST >> SHOULD?]] existing TLS connection be re-used? e.g. MUST >> SHOULD?]]
5.4. Voucher Status Telemetry 7.4. Voucher Status Telemetry
For automated bootstrapping of devices the adminstrative elements For automated bootstrapping of devices the adminstrative elements
providing bootstrapping also provide indications to the system providing bootstrapping also provide indications to the system
administrators concerning device lifecycle status. To facilitate administrators concerning device lifecycle status. To facilitate
this those elements need telemetry information concerning the this those elements need telemetry information concerning the
device's status. device's status.
To indicate Pledge status regarding the Audit Voucher the client To indicate Pledge status regarding the Voucher the client SHOULD
SHOULD post a status message. post a status message.
The posted data media type: application/json
The client HTTP POSTs the following to the server at the EST well The client HTTP POSTs the following to the server at the EST well
known URI /voucher_status. The Status field indicates if the Voucher known URI /voucher_status. The Status field indicates if the Voucher
was acceptable. If it was not acceptable the Reason string indicates was acceptable. If it was not acceptable the Reason string indicates
why. In the failure case this message is being sent to an why. In the failure case this message is being sent to an
unauthenticated, potentially malicious Registrar and therefore the unauthenticated, potentially malicious Registrar and therefore the
Reason string SHOULD NOT provide information beneficial to an Reason string SHOULD NOT provide information beneficial to an
attacker. The operational benefit of this telemetry information is attacker. The operational benefit of this telemetry information is
balanced against the operational costs of not recording that an balanced against the operational costs of not recording that an
Voucher was ignored by a client the registar expected to continue Voucher was ignored by a client the registar expected to continue
skipping to change at page 36, line 4 skipping to change at page 39, line 10
attacker. The operational benefit of this telemetry information is attacker. The operational benefit of this telemetry information is
balanced against the operational costs of not recording that an balanced against the operational costs of not recording that an
Voucher was ignored by a client the registar expected to continue Voucher was ignored by a client the registar expected to continue
joining the domain. joining the domain.
{ {
"version":"1", "version":"1",
"Status":FALSE /* TRUE=Success, FALSE=Fail" "Status":FALSE /* TRUE=Success, FALSE=Fail"
"Reason":"Informative human readable message" "Reason":"Informative human readable message"
} }
The server SHOULD respond with an HTTP 200 but MAY simply fail with The server SHOULD respond with an HTTP 200 but MAY simply fail with
an HTTP 404 error. The client ignores any response. Within the an HTTP 404 error. The client ignores any response. Within the
server logs the server SHOULD capture this telemetry information. server logs the server SHOULD capture this telemetry information.
5.5. MASA authorization log Request 7.5. MASA authorization log Request
A registrar requests the MASA authorization log from the MASA service A registrar requests the MASA authorization log from the MASA service
using this EST extension. using this EST extension.
This is done with an HTTP GET using the operation path value of This is done with an HTTP GET using the operation path value of
"/requestauditlog". "/requestauditlog".
The client HTTP POSTs the same Voucher Request as for requesting an The client MUST HTTP POSTs the same Voucher Request as for requesting
audit token but now posts it to the /requestauditlog URI instead. a Voucher. It is posted to the /requestauditlog URI instead. The
The IDevIDAuthorityKeyIdentifier and DevIDSerialNumber informs the IDevIDAuthorityKeyIdentifier and DevIDSerialNumber informs the MASA
MASA server which log is requested so the appropriate log can be server which log is requested so the appropriate log can be prepared
prepared for the response. for the response. Using the same media type and message minimizes
cryptographic and message operations although it results in
additional network traffic. The relying MASA server implementation
MAY leverage internal state to associate this request with the
original, and by now already validated, voucher request so as to
avoid an extra crypto validation.
5.6. MASA authorization log Response Request media type: application/voucherrequest+cms
7.6. MASA authorization log Response
A log data file is returned consisting of all log entries. For A log data file is returned consisting of all log entries. For
example: example:
{ {
"version":"1", "version":"1",
"events":[ "events":[
{ {
"date":"<date/time of the entry>", "date":"<date/time of the entry>",
"domainID":"<domainID as extracted from the domain CA certificate "domainID":"<domainID as extracted from the domain CA certificate
skipping to change at page 37, line 13 skipping to change at page 40, line 39
the log includes unexpected domainIDs this is indicative of the log includes unexpected domainIDs this is indicative of
problematic imprints by the Pledge. If the log includes nonce-less problematic imprints by the Pledge. If the log includes nonce-less
entries this is indicative of the permanent ability for the indicated entries this is indicative of the permanent ability for the indicated
domain to trigger a reset of the device and take over management of domain to trigger a reset of the device and take over management of
it. Equipment that is purchased pre-owned can be expected to have an it. Equipment that is purchased pre-owned can be expected to have an
extensive history. extensive history.
Log entries containing the Domain's ID can be compared against local Log entries containing the Domain's ID can be compared against local
history logs in search of discrepancies. history logs in search of discrepancies.
5.7. EST Integration for PKI bootstrapping 7.7. EST Integration for PKI bootstrapping
The prior sections describe EST extensions necessary to enable fully The prior sections describe EST extensions necessary to enable fully
automated bootstrapping. Although the Audit Voucher request/response automated bootstrapping. Although the Voucher request/response
structure members IDevIDAuthorityKeyIdentifier and DevIDSerialNumber structure members IDevIDAuthorityKeyIdentifier and DevIDSerialNumber
are specific to PKI bootstrapping these are the only PKI specific are specific to PKI bootstrapping these are the only PKI specific
aspects of the extensions and future work might replace them with aspects of the extensions and future work might replace them with
non-PKI structures. non-PKI structures.
The prior sections provide functionality for the Pledge to obtain a The prior sections provide functionality for the Pledge to obtain a
trust anchor representative of the Domain. The following section trust anchor representative of the Domain. The following section
describe using EST to obtain a locally issued PKI certificate. The describe using EST to obtain a locally issued PKI certificate. The
Pledge SHOULD leverage the discovered Registrar to proceed with Pledge SHOULD leverage the discovered Registrar to proceed with
certificate enrollment and, if they do, MUST implement the EST certificate enrollment and, if they do, MUST implement the EST
options described in this section. The Pledge MAY perform options described in this section. The Pledge MAY perform
alternative enrollment methods including discovering an alternate EST alternative enrollment methods including discovering an alternate EST
server, or proceed to use its IDevID credential indefinitely. server, or proceed to use its X.509 IDevID credential indefinitely.
5.7.1. EST Distribution of CA Certificates 7.7.1. EST Distribution of CA Certificates
The Pledge MUST request the full EST Distribution of CA Certificates The Pledge MUST request the full EST Distribution of CA Certificates
message. See RFC7030, section 4.1. message. See RFC7030, section 4.1.
This ensures that the Pledge has the complete set of current CA This ensures that the Pledge has the complete set of current CA
certificates beyond the domainCAcert (see Section 5.3 for a certificates beyond the domainCAcert (see Section 7.3 for a
discussion of the limitations). Although these restrictions are discussion of the limitations). Although these restrictions are
acceptable for a Registrar integrated with initial bootstrapping they acceptable for a Registrar integrated with initial bootstrapping they
are not appropriate for ongoing PKIX end entity certificate are not appropriate for ongoing PKIX end entity certificate
validation. validation.
5.7.2. EST CSR Attributes 7.7.2. EST CSR Attributes
Automated bootstrapping occurs without local administrative Automated bootstrapping occurs without local administrative
configuration of the Pledge. In some deployments its plausible that configuration of the Pledge. In some deployments its plausible that
the Pledge generates a certificate request containing only identity the Pledge generates a certificate request containing only identity
information known to the Pledge (essentially the IDevID information) information known to the Pledge (essentially the X.509 IDevID
and ultimately receives a certificate containing domain specific information) and ultimately receives a certificate containing domain
identity information. Conceptually the CA has complete control over specific identity information. Conceptually the CA has complete
all fields issued in the end entity certificate. Realistically this control over all fields issued in the end entity certificate.
is operationally difficult with the current status of PKI certificate Realistically this is operationally difficult with the current status
authority deployments where the CSR is submitted to the CA via a of PKI certificate authority deployments where the CSR is submitted
number of non-standard protocols. to the CA via a number of non-standard protocols.
To alleviate operational difficulty the Pledge MUST request the EST To alleviate operational difficulty the Pledge MUST request the EST
"CSR Attributes" from the EST server. This allows the local "CSR Attributes" from the EST server. This allows the local
infrastructure to inform the Pledge of the proper fields to include infrastructure to inform the Pledge of the proper fields to include
in the generated CSR. in the generated CSR.
[[EDNOTE: The following is specific to anima purposes and should be [[EDNOTE: The following is specific to anima purposes and should be
moved to an appropriate anima document so as to keep bootstrapping as moved to an appropriate anima document so as to keep bootstrapping as
generic as possible: What we want are a 'domain name' stored in [TBD] generic as possible: What we want are a 'domain name' stored in [TBD]
and an 'ACP IPv6 address' stored in the iPAddress field as specified and an 'ACP IPv6 address' stored in the iPAddress field as specified
in RFC5208 s4.2.1.6. ref ACP draft where certificate verification in RFC5208 s4.2.1.6. ref ACP draft where certificate verification
[TBD]. These should go into the subjectaltname in the [TBD] [TBD]. These should go into the subjectaltname in the [TBD]
fields.]]. If the hardwareModuleName in the IDevID is populated then fields.]]. If the hardwareModuleName in the X.509 IDevID is
it SHOULD by default be propagated to the LDevID along with the populated then it SHOULD by default be propagated to the LDevID along
hwSerialNum. The registar SHOULD support local policy concerning with the hwSerialNum. The registar SHOULD support local policy
this functionality. [[EDNOTE: extensive use of EST CSR Attributes concerning this functionality. [[EDNOTE: extensive use of EST CSR
might need an new OID definition]].]] Attributes might need an new OID definition]].]]
The Registar MUST also confirm the resulting CSR is formatted as The Registar MUST also confirm the resulting CSR is formatted as
indicated before forwarding the request to a CA. If the Registar is indicated before forwarding the request to a CA. If the Registar is
communicating with the CA using a protocol like full CMC which communicating with the CA using a protocol like full CMC which
provides mechanisms to override the CSR attributes, then these provides mechanisms to override the CSR attributes, then these
mechanisms MAY be used even if the client ignores CSR Attribute mechanisms MAY be used even if the client ignores CSR Attribute
guidance. guidance.
5.7.3. EST Client Certificate Request 7.7.3. EST Client Certificate Request
The Pledge MUST request a new client certificate. See RFC7030, The Pledge MUST request a new client certificate. See RFC7030,
section 4.2. section 4.2.
5.7.4. Enrollment Status Telemetry 7.7.4. Enrollment Status Telemetry
For automated bootstrapping of devices the adminstrative elements For automated bootstrapping of devices the adminstrative elements
providing bootstrapping also provide indications to the system providing bootstrapping also provide indications to the system
administrators concerning device lifecycle status. This might administrators concerning device lifecycle status. This might
include information concerning attempted bootstrapping messages seen include information concerning attempted bootstrapping messages seen
by the client, MASA provides logs and status of credential by the client, MASA provides logs and status of credential
enrollment. The EST protocol assumes an end user and therefore does enrollment. The EST protocol assumes an end user and therefore does
not include a final success indication back to the server. This is not include a final success indication back to the server. This is
insufficient for automated use cases. insufficient for automated use cases.
To indicate successful enrollment the client SHOULD re-negotiate the To indicate successful enrollment the client SHOULD re-negotiate the
EST TLS session using the newly obtained credentials. This occurs by EST TLS session using the newly obtained credentials. This occurs by
the client initiating a new TLS ClientHello message on the existing the client initiating a new TLS ClientHello message on the existing
TLS connection. The client MAY simply close the old TLS session and TLS connection. The client MAY simply close the old TLS session and
start a new one. The server MUST support either model. start a new one. The server MUST support either model.
In the case of a failure the Reason string indicates why the most In the case of a FAIL the Reason string indicates why the most recent
recent enrollment failed. The SubjectKeyIdentifier field MUST be enrollment failed. The SubjectKeyIdentifier field MUST be included
included if the enrollment attempt was for a keypair that is locally if the enrollment attempt was for a keypair that is locally known to
known to the client. If EST /serverkeygen was used and failed then the client. If EST /serverkeygen was used and failed then the field
the this field is ommited from the status telemetry. is ommited from the status telemetry.
In the case of a SUCCESS the Reason string is ommitted. The
SubjectKeyIdentifier is included so that the server can record the
successful certificate distribution.
Status media type: application/json
The client HTTP POSTs the following to the server at the new EST well The client HTTP POSTs the following to the server at the new EST well
known URI /enrollstatus. known URI /enrollstatus.
{ {
"version":"1", "version":"1",
"Status":TRUE /* TRUE=Success, FALSE=Fail" "Status":TRUE /* TRUE=Success, FALSE=Fail"
"Reason":"Informative human readable message" "Reason":"Informative human readable message"
"SubjectKeyIdentifier":"<base64 encoded subjectkeyidentifier for the "SubjectKeyIdentifier":"<base64 encoded subjectkeyidentifier for the
enrollment that failed>" enrollment that failed>"
} }
The server SHOULD respond with an HTTP 200 but MAY simply fail with The server SHOULD respond with an HTTP 200 but MAY simply fail with
an HTTP 404 error. an HTTP 404 error.
Within the server logs the server MUST capture if this message was Within the server logs the server MUST capture if this message was
recieved over an TLS session with a matching client certificate. recieved over an TLS session with a matching client certificate.
This allows for clients that wish to minimize their crypto operations This allows for clients that wish to minimize their crypto operations
to simpy POST this response without renegotiating the TLS session - to simply POST this response without renegotiating the TLS session -
at the cost of the server not being able to accurately verify that at the cost of the server not being able to accurately verify that
enrollment was truly successful. enrollment was truly successful.
5.7.5. EST over CoAP 7.7.5. EST over CoAP
[[EDNOTE: In order to support smaller devices the above section on [[EDNOTE: In order to support smaller devices the above section on
Proxy behavior introduces mandatory to implement support for CoAP Proxy behavior introduces mandatory to implement support for CoAP
support by the Proxy. This implies similar support by the Pledge and support by the Proxy. This implies similar support by the Pledge and
Registrar and means that the EST protocol operation encapsulation Registrar and means that the EST protocol operation encapsulation
into CoAP needs to be described. EST is HTTP based and "CoaP is into CoAP needs to be described. EST is HTTP based and "CoaP is
designed to easily interface with HTTP for integration" [RFC7252]. designed to easily interface with HTTP for integration" [RFC7252].
Use of CoAP implies Datagram TLS (DTLS) wherever this document Use of CoAP implies Datagram TLS (DTLS) wherever this document
describes TLS handshake specifics. A complexity is that the large describes TLS handshake specifics. A complexity is that the large
message sizes necessary for bootstrapping will require support for message sizes necessary for bootstrapping will require support for
[draft-ietf-core-block].]] [draft-ietf-core-block].]]
6. Reduced security operational modes 8. Reduced security operational modes
A common requirement of bootstrapping is to support less secure A common requirement of bootstrapping is to support less secure
operational modes for support specific use cases. The following operational modes for support specific use cases. The following
sections detail specific ways that the Pledge, Registrar and MASA can sections detail specific ways that the Pledge, Registrar and MASA can
be configured to run in a less secure mode for the indicated reasons. be configured to run in a less secure mode for the indicated reasons.
6.1. Trust Model 8.1. Trust Model
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
| New | | Circuit | | Domain | | Vendor | | New | | Circuit | | Domain | | Vendor |
| Entity | | Proxy | | Registrar | | Service | | Entity | | Proxy | | Registrar | | Service |
| | | | | | | (Internet | | | | | | | | (Internet |
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
Figure 7 Figure 10
Pledge: The Pledge could be compromised and providing an attack Pledge: The Pledge could be compromised and providing an attack
vector for malware. The entity is trusted to only imprint using vector for malware. The entity is trusted to only imprint using
secure methods described in this document. Additional endpoint secure methods described in this document. Additional endpoint
assessment techniques are RECOMMENDED but are out-of-scope of this assessment techniques are RECOMMENDED but are out-of-scope of this
document. document.
Proxy: Provides proxy functionalities but is not involved in Proxy: Provides proxy functionalities but is not involved in
security considerations. security considerations.
Registrar: When interacting with a MASA server a Registrar makes all Registrar: When interacting with a MASA server a Registrar makes all
skipping to change at page 40, line 42 skipping to change at page 44, line 29
accurately log all claim attempts and to provide authoritative log accurately log all claim attempts and to provide authoritative log
information to Registrars. The MASA does not know which devices information to Registrars. The MASA does not know which devices
are associated with which domains. These claims could be are associated with which domains. These claims could be
strengthened by using cryptographic log techniques to provide strengthened by using cryptographic log techniques to provide
append only, cryptographic assured, publicly auditable logs. append only, cryptographic assured, publicly auditable logs.
Current text provides only for a trusted vendor. Current text provides only for a trusted vendor.
Vendor Service, Ownership Validation: This form of vendor service is Vendor Service, Ownership Validation: This form of vendor service is
trusted to accurately know which device is owned by which domain. trusted to accurately know which device is owned by which domain.
6.2. New Entity security reductions 8.2. New Entity security reductions
The Pledge MAY support "trust on first use" on physical interfaces The Pledge MAY support "trust on first use" on physical interfaces
but MUST NOT support "trust on first use" on network interfaces. but MUST NOT support "trust on first use" on network interfaces.
This is because "trust on first use" permanently degrades the This is because "trust on first use" permanently degrades the
security for all other use cases. security for all other use cases.
The Pledge MAY have an operational mode where it skips Voucher The Pledge MAY have an operational mode where it skips Voucher
validation one time. For example if a physical button is depressed validation one time. For example if a physical button is depressed
during the bootstrapping operation. This can be useful if the vendor during the bootstrapping operation. This can be useful if the vendor
service is unavailable. This behavior SHOULD be available via local service is unavailable. This behavior SHOULD be available via local
configuration or physical presence methods to ensure new entities can configuration or physical presence methods to ensure new entities can
always be deployed even when autonomic methods fail. This allows for always be deployed even when autonomic methods fail. This allows for
unsecured imprint. unsecured imprint.
It is RECOMMENDED that this only be available if hardware assisted It is RECOMMENDED that this only be available if hardware assisted
NEA [RFC5209] is supported. NEA [RFC5209] is supported.
6.3. Registrar security reductions 8.3. Registrar security reductions
A Registrar can choose to accept devices using less secure methods. A Registrar can choose to accept devices using less secure methods.
These methods are acceptable when low security models are needed, as These methods are acceptable when low security models are needed, as
the security decisions are being made by the local administrator, but the security decisions are being made by the local administrator, but
they MUST NOT be the default behavior: they MUST NOT be the default behavior:
1. A registrar MAY choose to accept all devices, or all devices of a 1. A registrar MAY choose to accept all devices, or all devices of a
particular type, at the administrator's discretion. This could particular type, at the administrator's discretion. This could
occur when informing all Registrars of unique identifiers of new occur when informing all Registrars of unique identifiers of new
entities might be operationally difficult. entities might be operationally difficult.
2. A registrar MAY choose to accept devices that claim a unique 2. A registrar MAY choose to accept devices that claim a unique
identity without the benefit of authenticating that claimed identity without the benefit of authenticating that claimed
identity. This could occur when the Pledge does not include an identity. This could occur when the Pledge does not include an
X.509 IDevID factory installed credential. New Entities without X.509 IDevID factory installed credential. New Entities without
an IDevID credential MAY form the Section 5.1 request using the an X.509 IDevID credential MAY form the Section 7.1 request using
Section 5.2 format to ensure the Pledge's serial number the Section 7.2 format to ensure the Pledge's serial number
information is provided to the Registar (this includes the information is provided to the Registar (this includes the
IDevIDAuthorityKeyIdentifier value which would be statically IDevIDAuthorityKeyIdentifier value which would be statically
configured on the Pledge). The Pledge MAY refused to provide a configured on the Pledge). The Pledge MAY refused to provide a
TLS client certificate (as one is not available). The Pledge TLS client certificate (as one is not available). The Pledge
SHOULD support HTTP-based or certificate-less TLS authentication SHOULD support HTTP-based or certificate-less TLS authentication
as described in EST RFC7030 section 3.3.2. A Registrar MUST NOT as described in EST RFC7030 section 3.3.2. A Registrar MUST NOT
accept unauthenticated New Entities unless it has been configured accept unauthenticated New Entities unless it has been configured
to do so by an administrator that has verified that only expected to do so by an administrator that has verified that only expected
new entities can communicate with a Registrar (presumably via a new entities can communicate with a Registrar (presumably via a
physically secured perimeter). physically secured perimeter).
3. A Registrar MAY request nonce-less Audit Vouchers from the MASA 3. A Registrar MAY request nonce-less Vouchers from the MASA service
service (by not including a nonce in the request). These Audit (by not including a nonce in the request). These Vouchers can
Vouchers can then be transmitted to the Registrar and stored then be transmitted to the Registrar and stored until they are
until they are needed during bootstrapping operations. This is needed during bootstrapping operations. This is for use cases
for use cases where target network is protected by an air gap and where target network is protected by an air gap and therefore can
therefore can not contact the MASA service during Pledge not contact the MASA service during Pledge deployment.
deployment.
4. A registrar MAY ignore unrecognized nonce-less Audit Log entries.
This could occur when used equipment is purchased with a valid
history being deployed in air gap networks that required
permanent Audit Vouchers.
These modes are not available for devices that require a vendor 4. A registrar MAY ignore unrecognized nonce-less log entries. This
Ownership Voucher. The methods vendors use to determine which could occur when used equipment is purchased with a valid history
devices are owned by which domains is out-of-scope. being deployed in air gap networks that required permanent
Vouchers.
6.4. MASA security reductions 8.4. MASA security reductions
Lower security modes chosen by the MASA service effect all device Lower security modes chosen by the MASA service effect all device
deployments unless bound to the specific device identities. In which deployments unless bound to the specific device identities. In which
case these modes can be provided as additional features for specific case these modes can be provided as additional features for specific
customers. The MASA service can choose to run in less secure modes customers. The MASA service can choose to run in less secure modes
by: by:
1. Not enforcing that a Nonce is in the Audit Voucher. This results 1. Not enforcing that a nonce is in the Voucher. This results in
in distribution of Audit Voucher that never expire and in effect distribution of Voucher that never expires and in effect makes
makes the Domain an always trusted entity to the Pledge during the Domain an always trusted entity to the Pledge during any
any subsequent bootstrapping attempts. That this occurred is subsequent bootstrapping attempts. That this occurred is
captured in the log information so that the Domain registrar can captured in the log information so that the Domain registrar can
make appropriate security decisions when a Pledge joins the make appropriate security decisions when a Pledge joins the
Domain. This is useful to support use cases where Registrars Domain. This is useful to support use cases where Registrars
might not be online during actual device deployment. Because might not be online during actual device deployment. Because
this results in long lived Audit Voucher and do not require the this results in long lived Voucher and does not require the proof
proof that the device is online this is only accepted when the that the device is online this is only accepted when the
Registrar is authenticated by the MASA server and authorized to Registrar is authenticated by the MASA server and authorized to
provide this functionality. The MASA server is RECOMMENDED to provide this functionality. The MASA server is RECOMMENDED to
use this functionality only in concert with Ownership Validation use this functionality only in concert with an enhanced level of
tracking. ownership tracking (out-of-scope). If the Pledge device is known
to have a real-time-clock that is set from the factory use of a
voucher validity period is RECOMMENDED.
2. Not verifying ownership before responding with an Audit Voucher. 2. Not verifying ownership before responding with an Voucher. This
This is expected to be a common operational model because doing is expected to be a common operational model because doing so
so relieves the vendor providing MASA services from having to relieves the vendor providing MASA services from having to
tracking ownership during shipping and supply chain and allows tracking ownership during shipping and supply chain and allows
for a very low overhead MASA service. A Registrar uses the audit for a very low overhead MASA service. A Registrar uses the audit
log information as a defense in depth strategy to ensure that log information as a defense in depth strategy to ensure that
this does not occur unexpectedly (for example when purchasing new this does not occur unexpectedly (for example when purchasing new
equipment the Registrar would throw an error if any audit log equipment the Registrar would throw an error if any audit log
information is reported). information is reported).
7. Security Considerations 9. Security Considerations
In order to support a wide variety of use cases, devices can be There are uses cases where the MASA could be unavailable or
claimed by a registrar without proving possession of the device in uncooperative to the Registrar. They include planned and unplanned
question. This would result in a nonceless, and thus always valid, network partitions, changes to MASA policy, or other instances where
claim. Or would result in an invalid nonce being associated with a MASA policy rejects a claim. These introduce an operational risk to
claim. The MASA service is required to authenticate such Registrars the Registrar owner that MASA/vendor behavior might limit the ability
but no programmatic method is provided to ensure good behavior by the to re-boostrap a Pledge device. For example this might be an issue
MASA service. Nonceless entries into the audit log therefore during disaster recovery. This risk can be mitigated by Registrars
permanently reduce the value of a device because future Registrars, that request and maintain long term copies of "nonceless" Vouchers.
during future bootstrap attempts, would now have to be configured In that way they are guaranteed to be able to repeat bootstrapping
with policy to ignore previously (and potentially unknown) domains. for their devices.
Future registrars are recommended to take the audit history of a The issuance of nonceless vouchers themselves create a security
device into account when deciding to join such devices into their concern. If the Registrar of a previous domain can intercept
network. If the MASA server were to have allowed a significantly protocol communications then it can use a previously issued nonceless
large number of claims this might become onerous to the MASA server voucher to establish management control of a pledge device even after
which must maintain all the extra log entries. Ensuring a Registrar having sold it. This risk is mitigated by recording the issuance of
is representative of a valid customer domain even without validating such vouchers in the MASA audit log that is verified by the
ownership helps to mitigate this. subsequent Registrar. This reduces the resale value of the equipment
because future owners will detect the lowered security inherent in
the existence of a nonceless voucher that would be trusted by their
Pledge. This accurately reflects a balance between partition
resistant recovery and security of future bootstrapping. Registrars
take the Pledge's audit history into account when applying policy to
new devices.
It is possible for an attacker to send an authorization request to The MASA server is exposed to DoS attacks wherein attackers claim an
the MASA service directly after the real Registrar obtains an unbounded number of devices. Ensuring a Registrar is representative
authorization log. If the attacker could also force the of a valid vendor customer, even without validating ownership of
bootstrapping protocol to reset there is a theoretical opportunity specific Pledge devices, helps to mitigate this. Inserting a
for the attacker to use the Audit Voucher to take control of the cryptographic proof-of-possession step to the protocol operations is
Pledge but then proceed to enroll with the target domain. Possible a possible area of future work. One method that would not introduce
prevention mechanisms include: additional round-trips would be for the Registrar to share the Plege-
Registrar TLS handshake with the MASA service when requesting a
voucher. Doing so would allow the MASA service to verify that the
Registrar's Server Certificate was signed by the Pledge's Certificate
Verify message (which covers the entire handshake).
It is possible for an attacker to request a voucher from the MASA
service directly after the real Registrar obtains an audit log. If
the attacker could also force the bootstrapping protocol to reset
there is a theoretical opportunity for the attacker to use their
voucher to take control of the Pledge but then proceed to enroll with
the target domain. Possible prevention mechanisms include:
o Per device rate limits on the MASA service ensure such timing o Per device rate limits on the MASA service ensure such timing
attacks are difficult. attacks are difficult.
o In the advent of an unexpectedly lost bootstrapping connection the o The Registrar can repeat the request for audit log information at
Registrar repeats the request for audit log information. some time after bootstrapping is complete.
To facilitate logging and administrative oversight the Pledge reports To facilitate logging and administrative oversight the Pledge reports
on Audit Voucher parsing status to the Registrar. In the case of a on Voucher parsing status to the Registrar. In the case of a failure
failure this information is informative to a potentially malicious this information is informative to a potentially malicious Registar
Registar but this is RECOMMENDED anyway because of the operational but this is RECOMMENDED anyway because of the operational benefits of
benefits of an informed administrator in cases where the failure is an informed administrator in cases where the failure is indicative of
indicative of a problem. a problem.
As indicated in EST [RFC7030] the connection is provisional and
untrusted until the server is successfully authorized. If the server
provides a redirect response the client MUST follow the redirect but
the connection remains provisional. If the client uses a well known
URI for contacting a well known Registrar the EST Implicit Trust
Anchor database is used as is described in RFC6125 to authenticate
the well known URI. In this case the connection is not provisional
and RFC6125 methods can be used for each subsequent redirection.
To facilitate truely limited clients EST RFC7030 section 3.3.2 To facilitate truely limited clients EST RFC7030 section 3.3.2
requirements that the client MUST support a client authentication requirements that the client MUST support a client authentication
model have been reduced in Section 6 to a statement that clients only model have been reduced in Section 8 to a statement that clients only
"SHOULD" support such a model. This reflects current (not great) "SHOULD" support such a model. This reflects current (poor)
practices but is NOT RECOMMENDED. practices that are NOT RECOMMENDED.
The MASA service could lock a claim and refuse to issue a new voucher
or the MASA 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 to the Domain
that Vendor behavior could limit future bootstrapping of the device
by the Domain. This can be mitigated by Registrars that request
nonce-less Audit Vouchers.
7.1. Security concerns with discovery process
7.1.1. Discovery of Registrar by Proxy
As described in section Section 3.2, the RECOMMENDED mechanism is for
the proxy to discover the address of the registrar via GRASP
[I-D.ietf-anima-grasp]
GRASP is intended to run over a secured, and private Autonomic During the provisional period of the connection all HTTP header and
Control Plan [I-D.ietf-anima-autonomic-control-plane]. This content data MUST treated as untrusted data. HTTP libraries are
discovery is between the already registered Registrar, and the regularly exposed to non-secured HTTP traffic.
already registered Proxy. There are no GRASP security issues with
this part, as both entities will have already joined the secured ACP.
7.1.2. Discovery of Proxy by New Entity 10. Acknowledgements
[[EDNOTE: To be discussed]] We would like to thank the various reviewers for their input, in
particular Brian Carpenter, Toerless Eckert, Fuyu Eleven, Eliot Lear,
Sergey Kasatkin, Markus Stenberg, and Peter van der Stok
8. Acknowledgements 11. References
We would like to thank the various reviewers for their input, in 11.1. Normative References
particular Markus Stenberg, Brian Carpenter, Fuyu Eleven, Toerless
Eckert, Eliot Lear and Sergey Kasatkin.
9. References [I-D.ietf-anima-autonomic-control-plane]
Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic
Control Plane", draft-ietf-anima-autonomic-control-
plane-05 (work in progress), January 2017.
9.1. Normative References [I-D.ietf-anima-voucher]
Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
"Voucher and Voucher Revocation Profiles for Bootstrapping
Protocols", draft-ietf-anima-voucher-00 (work in
progress), January 2017.
[IDevID] IEEE Standard, , "IEEE 802.1AR Secure Device Identifier", [IDevID] IEEE Standard, , "IEEE 802.1AR Secure Device Identifier",
December 2009, <http://standards.ieee.org/findstds/ December 2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>. standard/802.1AR-2009.html>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 46, line 10 skipping to change at page 49, line 42
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed., [RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030, "Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013, DOI 10.17487/RFC7030, October 2013,
<http://www.rfc-editor.org/info/rfc7030>. <http://www.rfc-editor.org/info/rfc7030>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228, Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014, DOI 10.17487/RFC7228, May 2014,
<http://www.rfc-editor.org/info/rfc7228>. <http://www.rfc-editor.org/info/rfc7228>.
9.2. Informative References 11.2. Informative References
[I-D.behringer-homenet-trust-bootstrap] [I-D.behringer-homenet-trust-bootstrap]
Behringer, M., Pritikin, M., and S. Bjarnason, Behringer, M., Pritikin, M., and S. Bjarnason,
"Bootstrapping Trust on a Homenet", draft-behringer- "Bootstrapping Trust on a Homenet", draft-behringer-
homenet-trust-bootstrap-02 (work in progress), February homenet-trust-bootstrap-02 (work in progress), February
2014. 2014.
[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-04 (work in
progress), September 2016.
[I-D.ietf-anima-autonomic-control-plane]
Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic
Control Plane", draft-ietf-anima-autonomic-control-
plane-03 (work in progress), July 2016.
[I-D.ietf-anima-grasp] [I-D.ietf-anima-grasp]
Bormann, C., Carpenter, B., and B. Liu, "A Generic Bormann, C., Carpenter, B., and B. Liu, "A Generic
Autonomic Signaling Protocol (GRASP)", draft-ietf-anima- Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
grasp-08 (work in progress), October 2016. grasp-09 (work in progress), December 2016.
[I-D.ietf-netconf-zerotouch] [I-D.ietf-netconf-zerotouch]
Watsen, K. and M. Abrahamsson, "Zero Touch Provisioning Watsen, K. and M. Abrahamsson, "Zero Touch Provisioning
for NETCONF or RESTCONF based Management", draft-ietf- for NETCONF or RESTCONF based Management", draft-ietf-
netconf-zerotouch-09 (work in progress), July 2016. netconf-zerotouch-12 (work in progress), January 2017.
[I-D.lear-mud-framework] [I-D.lear-mud-framework]
Lear, E., "Manufacturer Usage Description Framework", Lear, E., "Manufacturer Usage Description Framework",
draft-lear-mud-framework-00 (work in progress), January draft-lear-mud-framework-00 (work in progress), January
2016. 2016.
[I-D.richardson-anima-state-for-joinrouter] [I-D.richardson-anima-state-for-joinrouter]
Richardson, M., "Considerations for stateful vs stateless Richardson, M., "Considerations for stateful vs stateless
join router in ANIMA bootstrap", draft-richardson-anima- join router in ANIMA bootstrap", draft-richardson-anima-
state-for-joinrouter-01 (work in progress), July 2016. state-for-joinrouter-01 (work in progress), July 2016.
[imprinting] [imprinting]
Wikipedia, , "Wikipedia article: Imprinting", July 2015, Wikipedia, , "Wikipedia article: Imprinting", July 2015,
<https://en.wikipedia.org/wiki/Imprinting_(psychology)>. <https://en.wikipedia.org/wiki/Imprinting_(psychology)>.
[pledge] Dictionary.com, , "Dictionary.com Unabridged", July 2015, [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
<http://dictionary.reference.com/browse/pledge>. IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <http://www.rfc-editor.org/info/rfc2473>.
[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,
<http://www.rfc-editor.org/info/rfc7217>.
[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <http://www.rfc-editor.org/info/rfc7435>.
[RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A., [RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
Networking: Definitions and Design Goals", RFC 7575, Networking: Definitions and Design Goals", RFC 7575,
DOI 10.17487/RFC7575, June 2015, DOI 10.17487/RFC7575, June 2015,
<http://www.rfc-editor.org/info/rfc7575>. <http://www.rfc-editor.org/info/rfc7575>.
[Stajano99theresurrecting] [Stajano99theresurrecting]
Stajano, F. and R. Anderson, "The resurrecting duckling: Stajano, F. and R. Anderson, "The resurrecting duckling:
security issues for ad-hoc wireless networks", 1999, security issues for ad-hoc wireless networks", 1999,
<https://www.cl.cam.ac.uk/~fms27/papers/1999-StajanoAnd- <https://www.cl.cam.ac.uk/~fms27/papers/1999-StajanoAnd-
duckling.pdf>. duckling.pdf>.
Authors' Addresses Appendix A. IPv4 operations
A.1. IPv4 Link Local addresses
Instead of an IPv6 link-local address, an IPv4 address may be
generated using [RFC3927] Dynamic Configuration of IPv4 Link-Local
Addresses.
In the case that an IPv4 Local-Local address is formed, then the
bootstrap process would continue as in the IPv6 case by looking for a
(circuit) proxy.
A.2. Use of DHCPv4
The Plege MAY obtain an IP address via DHCP [RFC2131]. The DHCP
provided parameters for the Domain Name System can be used to perform
DNS operations if all local discovery attempts fail.
Appendix B. mDNS / DNSSD proxy discovery options
The Pledge MAY perform DNS-based Service Discovery [RFC6763] over
Multicast DNS [RFC6762] searching for the service
"_bootstrapks._tcp.local.".
To prevent unaccceptable levels of network traffic the congestion
avoidance mechanisms specified in [RFC6762] section 7 MUST be
followed. The Pledge SHOULD listen for an unsolicited broadcast
response as described in [RFC6762]. This allows devices to avoid
announcing their presence via mDNS broadcasts and instead silently
join a network by watching for periodic unsolicited broadcast
responses.
Performs DNS-based Service Discovery [RFC6763] over normal DNS
operations. The service searched for is
"_bootstrapks._tcp.example.com". In this case the domain
"example.com" is discovered as described in [RFC6763] section 11.
This method is only available if the host has received a useable IPv4
address via DHCPv4 as suggested in Appendix A.
If no local bootstrapks service is located using the GRASP
mechanisms, or the above mentioned DNS-based Service Discovery
methods the Pledge MAY contact a well known vendor provided
bootstrapping server by performing a DNS lookup using a well known
URI such as "bootstrapks.vendor-example.com". The details of the URI
are vendor specific. Vendors that leverage this method on the Pledge
are responsible for providing the bootstrapks service.
The current DNS services returned during each query is maintained
until bootstrapping is completed. If bootstrapping fails and the
Pledge 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 doesn't work then the
second and third responses are tried. If these fail the Pledge moves
on to normal DNS-based Service Discovery.
Appendix C. IPIP Join Proxy mechanism
The Circuit Proxy mechanism suffers from requiring a state on the
Join Proxy for each connection that is relayed. The Circuit Proxy
can be considered a kind of Algorithm Gateway [FIND-good-REF].
An alternative to proxying at the TCP layer is to selectively forward
at the IP layer. This moves all per-connection to the Join
Registrar. The IPIP tunnel statelessly forwards packets. This
section provides some explanation of some of the details of the
Registrar discovery procotol which are not important to Circuit
Proxy, and some implementation advice.
The IPIP tunnel is described in [RFC2473]. Each such tunnel is
considered a unidirectional construct, but two tunnels may be
associated to form a bidirectional mechanism. An IPIP tunnel is
setup as follows. The outer addresses are an ACP address of the Join
Proxy, and the ACP address of the Join Registrar. The inner
addresses seen in the tunnel are the link-local addresses of the
network on which the join activity is occuring.
One way to look at this construct is to consider that the Registrar
is extending attaching an interface to the network on which the Join
Proxy is physically present. The Registrar then interacts as if it
were present on that network using link-local (fe80::) addresses.
The Join node is unaware that the traffic is being proxied through a
tunnel, and does not need any special routing.
There are a number of considerations with this mechanism which
require cause some minor amounts of complexity. Note that due to the
tunnels, the Registrar sees multiple connections to a fe80::/10
network on not just physical interfaces, but on each of the virtual
interfaces represending the tunnels.
C.1. Multiple Join networks on the Join Proxy side
The Join Proxy will in the general case be a routing device with
multiple interfaces. Even a device as simple as a wifi access point
may have wired, and multiple frequencies of wireless interfaces,
potentially with multiple ESSIDs.
Each of these interfaces on the Join Proxy may be seperate L3 routing
domains, and therefore will have a unique set of link-local
addresses. An IPIP packet being returned by the Registrar needs to
be forwarded to the correct interface, so the Join Proxy needs an
additional key to distinguish which network the packet should be
returned to.
The simplest way to get this additional key is to allocate an
additional ACP address; one address for each network on which join
traffic is occuring. The Join Proxy SHOULD do a GRASP M_NEG_SYN for
each interface which they wish to relay traffic, as this allows the
Registrar to do any static tunnel configuration that may be required.
C.2. Automatic configuration of tunnels on Registrar
The Join Proxy is expected to do a GRASP negotiation with the proxy
for each Join Interface that it needs to relay traffic from. This is
to permit Registrars to configure the appropriate virtual interfaces
before join traffic arrives.
A Registrar serving a large number of interfaces may not wish to
allocate resources to every interface at all times, but can instead
dynamically allocate interfaces. It can do this by monitoring IPIP
traffic that arrives on it's ACP interface, and when packets arrive
from new Join Proxys, it can dynamically configure virtual
interfaces.
A more sophisticated Registrar willing to modify the behaviour of
it's TCP and UDP stack could note the IPIP traffic origination in the
socket control block and make information available to the TCP layer
(for HTTPS connections), or to the the application (for CoAP
connections) via a proprietary extension to the socket API.
C.3. Proxy Neighbor Discovery by Join Proxy
The Join Proxy MUST answer neighbor discovery messages for the
address given by the Registrar as being it's link-local address. The
Join Proxy must also advertise this address as the address to which
to connect to when advertising it's existence.
This proxy neighbor discovery means that the pledge will create TCP
and UDP connections to the correct Registrar address. This matters
as the TCP and UDP pseudo-header checksum includes the destination
address, and for the proxy to remain completely stateless, it must
not be necessary for the checksum to be updated.
C.4. Use of connected sockets; or IP_PKTINFO for CoAP on Registrar
TCP connections on the registrar SHOULD properly capture the ifindex
of the incoming connection into the socket structure. This is normal
IPv6 socket API processing. The outgoing responses will go out on
the same (virtual) interface by ifindex.
When using UDP sockets with CoAP, the application will have to pay
attention to the incoming ifindex on the socket. Access to this
information is available using the IP_PKTINFO auxiliary extension
which is a standard part of the IPv6 sockets API.
A registrar application could, after receipt of an initial CoAP
message from the Pledge, create a connected UDP socket (including the
ifindex information). The kernel would then take care of accurate
demultiplexing upon receive, and subsequent transmission to the
correct interface.
C.5. Use of socket extension rather than virtual interface
Some operating systems on which a Registrar need be implemented may
find need for a virtual interface per Join Proxy to be problematic.
There are other mechanism which can make be done.
If the IPIP decapsulator can mark the (SYN) packet inside the kernel
with the address of the Join Proxy sending the traffic, then an
interface per Join Proxy may not be needed. The outgoing path need
just pay attention to this extra information and add an appropriate
IPIP header on outgoing. A CoAP over UDP mechanism may need to
expose this extra information to the application as the UDP sockets
are often not connected, and the application will need to specify the
outgoing path on each packet send.
Such an additional socket mechanism has not been standardized.
Terminating L2TP connections over IPsec transport mode suffers from
the same challenges.
Authors' Addresses
Max Pritikin Max Pritikin
Cisco Cisco
Email: pritikin@cisco.com Email: pritikin@cisco.com
Michael C. Richardson Michael C. Richardson
Sandelman Software Works Sandelman Software Works
Email: mcr+ietf@sandelman.ca Email: mcr+ietf@sandelman.ca
URI: http://www.sandelman.ca/ URI: http://www.sandelman.ca/
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