draft-ietf-anima-bootstrapping-keyinfra-05.txt   draft-ietf-anima-bootstrapping-keyinfra-06.txt 
ANIMA WG M. Pritikin ANIMA WG M. Pritikin
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Informational M. Richardson Intended status: Standards Track M. Richardson
Expires: September 14, 2017 SSW Expires: November 24, 2017 SSW
M. Behringer M. Behringer
S. Bjarnason S. Bjarnason
Cisco Cisco
K. Watsen K. Watsen
Juniper Networks Juniper Networks
March 13, 2017 May 23, 2017
Bootstrapping Remote Secure Key Infrastructures (BRSKI) Bootstrapping Remote Secure Key Infrastructures (BRSKI)
draft-ietf-anima-bootstrapping-keyinfra-05 draft-ietf-anima-bootstrapping-keyinfra-06
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's authorizing service, both online the in combination with a vendor's authorizing service, both online the
Internet, and offline. Bootstrapping a new device can occur using a Internet, and offline. Bootstrapping a new device can occur using a
routable address and a cloud service, or using only link-local routable address and a cloud service, or using only link-local
connectivity, or on limited/disconnected networks. Support for lower connectivity, or on limited/disconnected networks. Support for lower
security models, including devices with minimal identity, is security models, including devices with minimal identity, is
skipping to change at page 1, line 47 skipping to change at page 1, line 47
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 September 14, 2017. This Internet-Draft will expire on November 24, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Secure Imprinting without Vouchers . . . . . . . . . . . 5 1.1. Other Bootstrapping Approaches . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Scope of solution . . . . . . . . . . . . . . . . . . . . 8 1.3. Scope of solution . . . . . . . . . . . . . . . . . . . . 7
2. Architectural Overview . . . . . . . . . . . . . . . . . . . 9 2. Architectural Overview . . . . . . . . . . . . . . . . . . . 9
2.1. Secure Imprinting without Vouchers . . . . . . . . . . . 11 2.1. Secure Imprinting using Vouchers . . . . . . . . . . . . 10
2.2. Secure Imprinting using Vouchers . . . . . . . . . . . . 12 2.2. Initial Device Identifier . . . . . . . . . . . . . . . . 10
2.3. Initial Device Identifier . . . . . . . . . . . . . . . . 12 2.3. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . 12
3. Functional Overview . . . . . . . . . . . . . . . . . . . . . 13 2.4. Lack of realtime clock . . . . . . . . . . . . . . . . . 13
3.1. Behavior of a Pledge . . . . . . . . . . . . . . . . . . 15 2.5. Cloud Registrar . . . . . . . . . . . . . . . . . . . . . 14
3.1.1. Discovery . . . . . . . . . . . . . . . . . . . . . . 17 3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 14
3.1.2. Identity . . . . . . . . . . . . . . . . . . . . . . 18 3.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1.3. Request Join . . . . . . . . . . . . . . . . . . . . 18 3.1.1. Proxy Discovery Protocol Details . . . . . . . . . . 17
3.1.4. Imprint . . . . . . . . . . . . . . . . . . . . . . . 19 3.1.2. Registrar Discovery Protocol Details . . . . . . . . 17
3.1.5. Lack of realtime clock . . . . . . . . . . . . . . . 19 3.2. Request Voucher from the Registrar . . . . . . . . . . . 18
3.1.6. Enrollment . . . . . . . . . . . . . . . . . . . . . 20 3.3. Request Voucher from MASA . . . . . . . . . . . . . . . . 20
3.1.7. Being Managed . . . . . . . . . . . . . . . . . . . . 20 3.4. Voucher Response . . . . . . . . . . . . . . . . . . . . 21
3.2. Behavior of a Join Proxy . . . . . . . . . . . . . . . . 21 3.4.1. Completing authentication of Provisional TLS
3.2.1. CoAP connection to Registrar . . . . . . . . . . . . 22 connection . . . . . . . . . . . . . . . . . . . . . 22
3.2.2. HTTPS proxy connection to Registrar . . . . . . . . . 22 3.5. Voucher Status Telemetry . . . . . . . . . . . . . . . . 23
3.3. Behavior of the Registrar . . . . . . . . . . . . . . . . 22 3.6. MASA authorization log Request . . . . . . . . . . . . . 24
3.3.1. Pledge Authentication . . . . . . . . . . . . . . . . 23 3.7. MASA authorization log Response . . . . . . . . . . . . . 24
3.3.2. Pledge Authorization . . . . . . . . . . . . . . . . 24 3.8. EST Integration for PKI bootstrapping . . . . . . . . . . 26
3.3.3. Claiming the New Entity . . . . . . . . . . . . . . . 24 3.8.1. EST Distribution of CA Certificates . . . . . . . . . 26
3.3.4. Log Verification . . . . . . . . . . . . . . . . . . 25 3.8.2. EST CSR Attributes . . . . . . . . . . . . . . . . . 27
3.4. Behavior of the MASA Service . . . . . . . . . . . . . . 26 3.8.3. EST Client Certificate Request . . . . . . . . . . . 27
3.5. Leveraging the new key infrastructure / next steps . . . 26 3.8.4. Enrollment Status Telemetry . . . . . . . . . . . . . 27
3.5.1. Network boundaries . . . . . . . . . . . . . . . . . 26 3.8.5. EST over CoAP . . . . . . . . . . . . . . . . . . . . 29
3.6. Interactions with Network Access Control . . . . . . . . 27 4. Reduced security operational modes . . . . . . . . . . . . . 29
4. Domain Operator Activities . . . . . . . . . . . . . . . . . 27 4.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 29
4.1. Instantiating the Domain Certification Authority . . . . 27 4.2. New Entity security reductions . . . . . . . . . . . . . 30
4.2. Instantiating the Registrar . . . . . . . . . . . . . . . 27 4.3. Registrar security reductions . . . . . . . . . . . . . . 30
4.3. Accepting New Entities . . . . . . . . . . . . . . . . . 28 4.4. MASA security reductions . . . . . . . . . . . . . . . . 31
4.4. Automatic Enrollment of Devices . . . . . . . . . . . . . 29 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
4.5. Secure Network Operations . . . . . . . . . . . . . . . . 29 5.1. PKIX Registry . . . . . . . . . . . . . . . . . . . . . . 32
5. Proxy Discovery Protocol Details . . . . . . . . . . . . . . 29 6. Security Considerations . . . . . . . . . . . . . . . . . . . 32
6. Registrar Discovery Protocol Details . . . . . . . . . . . . 29 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 34
7. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 30 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
7.1. Request Voucher from the Registrar . . . . . . . . . . . 34 8.1. Normative References . . . . . . . . . . . . . . . . . . 34
7.2. Request Voucher from MASA . . . . . . . . . . . . . . . . 35 8.2. Informative References . . . . . . . . . . . . . . . . . 35
7.3. Voucher Response . . . . . . . . . . . . . . . . . . . . 36 Appendix A. IPv4 operations . . . . . . . . . . . . . . . . . . 37
7.3.1. Completing authentication of Provisional TLS A.1. IPv4 Link Local addresses . . . . . . . . . . . . . . . . 37
connection . . . . . . . . . . . . . . . . . . . . . 37 A.2. Use of DHCPv4 . . . . . . . . . . . . . . . . . . . . . . 37
7.4. Voucher Status Telemetry . . . . . . . . . . . . . . . . 38 Appendix B. mDNS / DNSSD proxy discovery options . . . . . . . . 37
7.5. MASA authorization log Request . . . . . . . . . . . . . 39 Appendix C. IPIP Join Proxy mechanism . . . . . . . . . . . . . 38
7.6. MASA authorization log Response . . . . . . . . . . . . . 39 C.1. Multiple Join networks on the Join Proxy side . . . . . . 39
7.7. EST Integration for PKI bootstrapping . . . . . . . . . . 40 C.2. Automatic configuration of tunnels on Registrar . . . . . 39
7.7.1. EST Distribution of CA Certificates . . . . . . . . . 41 C.3. Proxy Neighbor Discovery by Join Proxy . . . . . . . . . 39
7.7.2. EST CSR Attributes . . . . . . . . . . . . . . . . . 41
7.7.3. EST Client Certificate Request . . . . . . . . . . . 42
7.7.4. Enrollment Status Telemetry . . . . . . . . . . . . . 42
7.7.5. EST over CoAP . . . . . . . . . . . . . . . . . . . . 43
8. Reduced security operational modes . . . . . . . . . . . . . 43
8.1. Trust Model . . . . . . . . . . . . . . . . . . . . . . . 43
8.2. New Entity security reductions . . . . . . . . . . . . . 44
8.3. Registrar security reductions . . . . . . . . . . . . . . 44
8.4. MASA security reductions . . . . . . . . . . . . . . . . 45
9. Security Considerations . . . . . . . . . . . . . . . . . . . 46
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 48
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 48
11.1. Normative References . . . . . . . . . . . . . . . . . . 48
11.2. Informative References . . . . . . . . . . . . . . . . . 49
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 C.4. Use of connected sockets; or IP_PKTINFO for CoAP on
Registrar . . . . . . . . . . . . . . . . . . . . . . . . 54 Registrar . . . . . . . . . . . . . . . . . . . . . . . . 40
C.5. Use of socket extension rather than virtual interface . . 54 C.5. Use of socket extension rather than virtual interface . . 40
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54 Appendix D. To be deprecated: Consolidation remnants . . . . . . 40
D.1. Functional Overview . . . . . . . . . . . . . . . . . . . 41
D.1.1. Behavior of a Pledge . . . . . . . . . . . . . . . . 44
D.1.2. Behavior of a Join Proxy . . . . . . . . . . . . . . 50
D.1.3. Behavior of the Registrar . . . . . . . . . . . . . . 51
D.1.4. Behavior of the MASA Service . . . . . . . . . . . . 55
D.1.5. Leveraging the new key infrastructure / next steps . 56
D.1.6. Interactions with Network Access Control . . . . . . 56
D.2. Domain Operator Activities . . . . . . . . . . . . . . . 56
D.2.1. Instantiating the Domain Certification Authority . . 57
D.2.2. Instantiating the Registrar . . . . . . . . . . . . . 57
D.2.3. Accepting New Entities . . . . . . . . . . . . . . . 57
D.2.4. Automatic Enrollment of Devices . . . . . . . . . . . 58
D.2.5. Secure Network Operations . . . . . . . . . . . . . . 58
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 59
1. Introduction 1. Introduction
To literally "pull yourself up by the bootstraps" is an impossible BRSKI provides a foundation to securely answer the following
action. Similarly the secure establishment of a key infrastructure questions between an element of the network domain called the
without external help is also an impossibility. Today it is commonly "Registrar" and an unconfigured and untouched device called a
accepted that the initial connections between nodes are insecure, "Pledge":
until key distribution is complete, or that domain-specific keying
material is pre-provisioned on each new device in a costly and non-
scalable manner. These existing mechanisms are known as non-secured
'Trust on First Use' (TOFU) [RFC7435], 'resurrecting duckling'
[Stajano99theresurrecting] or 'pre-staging'.
This document describes a zero-touch approach to bootstrapping that
secures the initial distribution of key material between an
unconfigured and untouched device called a "Pledge" and the
"Registrar" device that is a member of an established network domain.
The bootstrapping process provides a foundation to securely answer
the following questions:
o Registrar authenticating the Pledge: "Who is this device? What is o Registrar authenticating the Pledge: "Who is this device? What is
its identity?" its identity?"
o Registrar authorization the Pledge: "Is it mine? Do I want it? o Registrar authorization the Pledge: "Is it mine? Do I want it?
What are the chances it has been compromised?" What are the chances it has been compromised?"
o Pledge authenticating the Registrar/Domain: "What is this domain's o Pledge authenticating the Registrar/Domain: "What is this domain's
identity?" identity?"
o Pledge authorization the Registrar: "Should I join it?" o Pledge authorization the Registrar: "Should I join it?"
This document details protocols and messages to the endpoints to This document details protocols and messages to the endpoints to
answer the above questions. The Registrar actions derive from Pledge answer the above questions. The Registrar actions derive from Pledge
identity, third party cloud service communications, and local access identity, third party cloud service communications, and local access
control lists. The Pledge actions derive from a cryptographically control lists. The Pledge actions derive from a cryptographically
protected "voucher" message delivered through the Registrar. protected "voucher" message delivered through the Registrar.
Multiple forms of "vouchers" are described to support a variety of
use cases.
The syntactic details of vouchers are described in detail in The syntactic details of vouchers are described in detail in
[I-D.ietf-anima-voucher]. This document details automated protocol [I-D.ietf-anima-voucher]. This document details automated protocol
mechanisms to obtain vouchers. mechanisms to obtain vouchers.
The result of bootstrapping is that a security association between BRSKI results in the Pledge storing an X.509 root certificate
the Pledge and the Registrar is established. A method of leveraging sufficient for verifying the Registrar identity. In the process a
this association to optimize PKI enrollment is described. TLS connection is established which can be directly used for
Enrollment over Secure Transport (EST). The Pledge can use these
credentials to secure additional protocol exchanges.
The described system is agile enough to support bootstrapping BRSKI is agile enough to support bootstrapping alternative key
alternative key infrastructures, such as a symmetric key solutions, infrastructures, such as a symmetric key solutions, but no such
but no such system is described. system is described in this document.
1.1. Secure Imprinting without Vouchers 1.1. Other Bootstrapping Approaches
There are pre-existing methods available for establishing initial To literally "pull yourself up by the bootstraps" is an impossible
trust. For example the enrollment protocol EST [RFC7030] details a action. Similarly the secure establishment of a key infrastructure
set of non-autonomic bootstrapping methods such as: without external help is also an impossibility. Today it is commonly
accepted that the initial connections between nodes are insecure,
until key distribution is complete, or that domain-specific keying
material is pre-provisioned on each new device in a costly and non-
scalable manner. Existing mechanisms are known as non-secured 'Trust
on First Use' (TOFU) [RFC7435], 'resurrecting duckling'
[Stajano99theresurrecting] or 'pre-staging'.
Another approach is to try and minimize user actions during
bootstrapping. The enrollment protocol EST [RFC7030] details a set
of non-autonomic bootstrapping methods in this vein:
o using the Implicit Trust Anchor database (not an autonomic o using the Implicit Trust Anchor database (not an autonomic
solution because the URL must be securely distributed), solution because the URL must be securely distributed),
o engaging a human user to authorize the CA certificate using out- o engaging a human user to authorize the CA certificate using out-
of-band data (not an autonomic solution because the human user is of-band data (not an autonomic solution because the human user is
involved), involved),
o using a configured Explicit TA database (not an autonomic solution o using a configured Explicit TA database (not an autonomic solution
because the distribution of an explicit TA database is not because the distribution of an explicit TA database is not
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Pledge. This creates serveral problems and limitations: Pledge. This creates serveral problems and limitations:
o the pledge requires realtime connectivity to the vendor service, o the pledge requires realtime connectivity to the vendor service,
o the domain identity is exposed to the vendor service (this is a o the domain identity is exposed to the vendor service (this is a
privacy concern), privacy concern),
o the vendor is responsible for making the authorization decisions o the vendor is responsible for making the authorization decisions
(this is a liability concern), (this is a liability concern),
BRSKI addresses these issues by introducting an authorization layer BRSKI addresses these issues by defining "voucher" and automation
via "vouchers". The additional complexity provides for significant extensions to the EST protocol.
flexibility.
1.2. Terminology 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:
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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 solution described in this document is aimed in general at non- The solution described in this document is aimed in general at 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 as 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 bootstrapping 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; for privacy reasons, communication itself is not optimized for speed; for privacy reasons,
the discovery process allows for the Pledge to avoid announcing it's the discovery process allows for the Pledge to avoid announcing it's
presence through broadcasting. This protocol is not intended for low presence through broadcasting.
latency handoffs. In networks requiring such things, the pledge
SHOULD already have been enrolled. 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 certificate contents, and the process by which the four questions
above are resolved do apply to constained devices. It is simply the
actual on-the-wire imprint protocol which could be inappropriate.
This document presumes that network access control has either already This document presumes that network access control has either already
occurred, is not required, or is integrated by the proxy and occurred, is not required, or is integrated by the proxy and
registrar in such a way that the device itself does not need to be registrar in such a way that the device itself does not need to be
aware of the details. Although the use of an X.509 Initial Device aware of the details. Although the use of an X.509 Initial Device
Identity is consistant with IEEE 802.1AR [IDevID], and allows for Identity is consistant with IEEE 802.1AR [IDevID], and allows for
alignment with 802.1X network access control methods, its use here is alignment with 802.1X network access control methods, its use here is
for Pledge authentication rather than network access control. for Pledge authentication rather than network access control.
Integrating this protocol with network access control, perhaps as an
Some aspects are in scope for constrained devices on challenged Extensible Authentication Protocol (EAP) method (see [RFC3748]), is
networks: the certificate contents, and the process by which the four out-of-scope.
questions above are resolved is in scope. It is simply the actual
on-the-wire imprint protocol which is likely inappropriate.
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.
. .
.+------------------------+ .+------------------------+
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| | . | . | | . | .
| | . +------------+ +-----------+ | . | | . +------------+ +-----------+ | .
| | . | | | | | . | | . | | | | | .
|Pledge | . | Circuit | | Domain <-------+ . |Pledge | . | Circuit | | Domain <-------+ .
| | . | Proxy | | Registrar | . | | . | Proxy | | Registrar | .
| <--------> <-------> | . | <--------> <-------> | .
| | . | | | | . | | . | | | | .
| | . +------------+ +-----+-----+ . | | . +------------+ +-----+-----+ .
|IDevID | . | . |IDevID | . | .
| | . +-----------------+----------+ . | | . +-----------------+----------+ .
| | . | Domain Certification | . | | . | Key Infrastructure | .
| | . | Authority | . | | . | (e.g. PKI Certificate | .
+-------+ . | Management and etc | . +-------+ . | Authority) | .
. +----------------------------+ . . +----------------------------+ .
. . . .
................................................ ................................................
"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 Vendor Service for each vendor that supports devices following be a Vendor Service for each vendor that supports devices following
this document's specification, or an integrator could provide a this document's specification, or an integrator could provide a
generic service authorized by multiple vendors. It is unlikely that generic service authorized by multiple vendors. It is unlikely that
an integrator could provide Ownership Tracking services for multiple an integrator could provide Ownership Tracking services for multiple
vendors due to the required sales channel integrations necessary to vendors due to the required sales channel integrations necessary to
track ownership. track ownership.
The domain is the managed network infrastructure the Pledge is The domain is the managed network infrastructure with a Key
managed by. The a domain provides initial device connectivity Infrastructure the Pledge is joining. The a domain provides initial
minimally sufficient for bootstrapping through the Circuit Proxy. device connectivity sufficient for bootstrapping with a Circuit
The Domain registrar makes authorization decisions and handles Proxy. The Domain registrar authenticates the Pledge, makes
connectivity to the vendor services and authenticates the Pledge. authorization decisions, and distributes vouchers obtained from the
Optional cryptographic credential and configuration management Vendor Service. Optionally the Registrar also acts as a PKI
systems are expected. Registration Authority.
This document describes a secure zero-touch approach to bootstrapping
a remote key infrastructure. Secure bootstrapping requires
mitigating the threat of an attacker domain establishing a management
role over the pledge device. In a "trust on first use" model, where
this threat is ignored, the attacker has an opportunity to install a
persistent malware component. This document uses Vouchers to address
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 2.1. Secure Imprinting using Vouchers
A voucher is a cryptographically protected statement to the Pledge A voucher is a cryptographically protected statement to the Pledge
device authorizing a zero-touch imprint on the Registrar domain. device authorizing a zero-touch imprint on the Registrar domain.
The format and cryptographic mechanism of vouchers is described in The format and cryptographic mechanism of vouchers is described in
detail in [I-D.ietf-anima-voucher]. detail in [I-D.ietf-anima-voucher].
Vouchers provide a flexible mechanism to secure imprinting: the Vouchers provide a flexible mechanism to secure imprinting: the
Pledge device only imprints when a voucher can be validated. At the Pledge device only imprints when a voucher can be validated. At the
lowest security levels the MASA server can indiscriminately issue lowest security levels the MASA server can indiscriminately issue
vouchers. At the highest security levels issuance of vouchers can be vouchers. At the highest security levels issuance of vouchers can be
integrated with complex sales channel integrations that are beyond integrated with complex sales channel integrations that are beyond
the scope of this document. This provides the flexability for a the scope of this document. This provides the flexibility for a
number of use cases via a single common protocol mechanism on the number of use cases via a single common protocol mechanism on the
Pledge and Registrar devices that are to be widely deployed in the Pledge and Registrar devices that are to be widely deployed in the
field. The MASA vendor services have the flexibility to leverage field. The MASA vendor services have the flexibility to leverage
either the currently defined claim mechanisms or to experiment with either the currently defined claim mechanisms or to experiment with
higher or lower security levels. higher or lower security levels.
2.3. Initial Device Identifier 2.2. Initial Device Identifier
Pledge authentication is via an X.509 certificate installed during Pledge authentication is via an X.509 certificate installed during
the manufacturing process. This Initial Device Identifier provides a the manufacturing process. This Initial Device Identifier provides a
basis for authenticating the Pledge during subsequent protocol basis for authenticating the Pledge during subsequent protocol
exchanges and informing the Registrar of the MASA URI. There is no exchanges and informing the Registrar of the MASA URI. There is no
requirement for a common root PKI hierarchy. Each device vendor can requirement for a common root PKI hierarchy. Each device vendor can
generate their own root certificate. generate their own root certificate.
The following previously defined fields are in the X.509 IDevID The following previously defined fields are in the X.509 IDevID
certificate: certificate:
o The subject field's DN encoding MUST include the "serialNumber" o The subject field's DN encoding MUST include the "serialNumber"
attribute with the device's unique serial number. attribute with the device's unique serial number.
o The subject alt field's encoding SHOULD include the a non-critical o The subject-alt field's encoding SHOULD include a non-critical
version of the RFC4108 defined HardwareModuleName. version of the RFC4108 defined HardwareModuleName.
The following newly defined field SHOULD be in the X.509 IDevID The following newly defined field SHOULD be in the X.509 IDevID
certificate: An X.509 non-critical certificate extension that certificate: An X.509 non-critical certificate extension that
contains a single Uniform Resource Identifier (URI) that points to an contains a single Uniform Resource Identifier (URI) that points to an
on-line Manufacturer Authorized Signing Authority. The URI is on-line Manufacturer Authorized Signing Authority. The URI is
represented as described in Section 7.4 of [RFC5280]. represented as described in Section 7.4 of [RFC5280].
Any Internationalized Resource Identifiers (IRIs) MUST be mapped to Any Internationalized Resource Identifiers (IRIs) MUST be mapped to
URIs as specified in Section 3.1 of [RFC3987] before they are placed URIs as specified in Section 3.1 of [RFC3987] before they are placed
in the certificate extension. in the certificate extension. The URI provides the authority
information. The BRSKI .well-known tree is described in Section 3
The semantics of the URI are defined in Section 7 of this document.
The new extension is identified as follows: The new extension is identified as follows:
<CODE BEGINS> <CODE BEGINS>
MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6) MASAURLExtnModule-2016 { iso(1) identified-organization(3) dod(6)
internet(1) security(5) mechanisms(5) pkix(7) internet(1) security(5) mechanisms(5) pkix(7)
id-mod(0) id-mod-MASAURLExtn2016(TBD) } id-mod(0) id-mod-MASAURLExtn2016(TBD) }
DEFINITIONS IMPLICIT TAGS ::= BEGIN DEFINITIONS IMPLICIT TAGS ::= BEGIN
skipping to change at page 13, line 47 skipping to change at page 12, line 7
END END
<CODE ENDS> <CODE ENDS>
The choice of id-pe is based on guidance found in Section 4.2.2 of 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 [RFC5280], "These extensions may be used to direct applications to
on-line information about the issuer or the subject". The MASA URL on-line information about the issuer or the subject". The MASA URL
is precisely that: online information about the particular subject. is precisely that: online information about the particular subject.
3. Functional Overview 2.3. Protocol Flow
Entities behave in an autonomic fashion. They discover each other
and autonomically bootstrap into a key infrastructure delineating the
autonomic domain. See [RFC7575] for more information.
This section details the state machine and operational flow for each
of the main three entities. The pledge, the domain (primarily a
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 | Appendix A | | |<-RFC3927 IPv4 adr | Appendix A | |
or|<-RFC4862 IPv6 adr | | | or|<-RFC4862 IPv6 adr | | |
| | | | | | | |
|-------------------->| | | |-------------------->| | |
| optional: mDNS query| Appendix B | | | optional: mDNS query| Appendix B | |
| RFC6763/RFC6762 | | | | RFC6763/RFC6762 | | |
| | | | | | | |
|<--------------------| | | |<--------------------| | |
| GRASP M_FLOOD | | | | GRASP M_FLOOD | | |
| periodic broadcast| | | | 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 | /---> | |
P | | [accept device?] | P | | [accept device?] |
P | | [contact Vendor] | P | | [contact Vendor] |
P | | |--Pledge ID-------->| P | | |--Pledge ID-------->|
P | | |--Domain ID-------->| P | | |--Domain ID-------->|
P | | |--optional:nonce--->| P | | |--optional:nonce--->|
P | | | [extract DomainID] P | | | [extract DomainID]
P | | | | P | | | |
P | optional: | [update audit log] P | optional: | [update audit log]
P | |can | | P | |can | |
P | |occur | | P | |occur | |
P | |in | | P | |in | |
P | |advance | | P | |advance | |
P | | | | P | | | |
P | | |<-device audit log--| P | | |<-device audit log--|
P | | |<- voucher ---------| P | | |<- voucher ---------|
P | \----> | | P | \----> | |
P | | | P | | |
P | [verify audit log and voucher] | P | [verify audit log and voucher] |
P | | | P | | |
P<------voucher---------------------------| | P<------voucher---------------------------| |
[verify voucher ] | | | [verify voucher ] | | |
[verify provisional cert ]| | | [verify provisional cert| | |
| | | | | | | |
|---------------------------------------->| | |<--------------------------------------->| |
| Continue with RFC7030 enrollment | | | Continue with RFC7030 enrollment | |
| using now bidirectionally authenticated | | | using now bidirectionally authenticated | |
| TLS session. | | | | TLS session. | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
Figure 2 Figure 2
3.1. Behavior of a Pledge 2.4. Lack of realtime clock
A pledge that has not yet been bootstrapped attempts to find a local
domain and join it. A pledge MUST NOT automatically initiate
bootstrapping if it has already been configured or is in the process
of being configured.
States of a pledge are as follows:
+--------------+
| Start |
| |
+------+-------+
|
+------v-------+
| Discover |
+------------> |
| +------+-------+
| |
| +------v-------+
| | Identity |
^------------+ |
| rejected +------+-------+
| |
| +------v-------+
| | Request |
| | Join |
| +------+-------+
| |
| +------v-------+
| | Imprint | Optional
^------------+ <--+Manual input (Appendix C)
| Bad Vendor +------+-------+
| response |
| +------v-------+
| | Enroll |
^------------+ |
| Enroll +------+-------+
| Failure |
| +------v-------+
| | Being |
^------------+ Managed |
Factory +--------------+
reset
Figure 3
State descriptions for the pledge are as follows:
1. Discover a communication channel to a Registrar.
2. Identify itself. This is done by presenting an X.509 IDevID
credential to the discovered Registrar (via the Proxy) in a TLS
handshake. (The Registrar credentials are only provisionally
accepted at this time).
3. Requests to Join the discovered Registrar. A unique nonce can be
included ensuring that any responses can be associated with this
particular bootstrapping attempt.
4. Imprint on the Registrar. This requires verification of the
vendor service provided voucher. A voucher contains sufficient
information for the Pledge to complete authentication of a
Registrar. (It enables the Pledge to finish authentication of
the Registrar TLS server certificate).
5. Enroll. By accepting the domain specific information from a
Registrar, and by obtaining a domain certificate from a Registrar
using a standard enrollment protocol, e.g. Enrollment over
Secure Transport (EST) [RFC7030].
6. The Pledge is now a member of, and can be managed by, the domain
and will only repeat the discovery aspects of bootstrapping if it
is returned to factory default settings.
The following sections describe each of these steps in more detail.
3.1.1. Discovery
The result of discovery is a logical communication with a Registrar,
through a Proxy. The Proxy is transparent to the Pledge but is
always assumed to exist.
To discover the Registrar the Pledge performs the following actions:
a. MUST: Obtains a local address using IPv6 methods as described in
[RFC4862] IPv6 Stateless Address AutoConfiguration. [RFC7217] is
encouraged. IPv4 methods are described in Appendix A
b. MUST: Listen for GRASP M_FLOOD ([I-D.ietf-anima-grasp])
announcements of the objective: "ACP+Proxy". See section
Section 5 for the details of the the objective. The Pledge may
listen concurrently for other sources of information, see
Appendix B.
Once a proxy is discovered the Pledge communicates with a Registrar
through the proxy using the bootstrapping protocol defined in
Section 7.
Each discovery method attempted SHOULD exponentially back-off
attempts (to a maximum of one hour) to avoid overloading the network
infrastructure with discovery. The back-off timer for each method
MUST be independent of other methods. Methods SHOULD be run in
parallel to avoid head of queue problems. Once a connection to a
Registrar is established (e.g. establishment of a TLS session key)
there are expectations of more timely responses, see Section 7.1.
Once all discovered services are attempted the device SHOULD return
to listening for GRASP M_FLOOD. It should periodically retry the
vendor specific mechanisms. The Pledge MAY prioritize selection
order as appropriate for the anticipated environment.
3.1.2. Identity
The Pledge identifies itself during the communication protocol
handshake. If the client identity is rejected (that is, the TLS
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.
Thus the connection is provisional and all data received is untrusted
until sufficiently validated even though it is over a TLS connection.
This is aligned with the existing provisional mode of EST [RFC7030]
during s4.1.1 "Bootstrap Distribution of CA Certificates". See
Section 7.3 for more information about when the TLS connection
authentication is completed.
All security associations established are between the new device and
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
The Pledge POSTs a request to join the domain to the Bootstrapping
server. This request contains a Pledge generated nonce and informs
the Bootstrapping server which imprint methods the Pledge will
accept.
The nonce ensures the Pledge can verify that responses are specific
to this bootstrapping attempt. This minimizes the use of global time
and provides a substantial benefit for devices without a valid clock.
3.1.3.1. Redirects during the Join Process
EST [RFC7030] describes situations where the bootstrapping server MAY
redirect the client to an alternate server via a 3xx status code.
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.
3.1.4. Imprint
The Pledge validates the voucher and accepts the Registrar ID. The
provisional TLS connection is validated using the Registrar ID from
the voucher.
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
validity periods are confirmed. This paradoxical "catch-22" is validity periods are confirmed. This paradoxical "catch-22" is
resolved by the Pledge maintaining a concept of the current "window" resolved by the Pledge maintaining a concept of the current "window"
skipping to change at page 19, line 47 skipping to change at page 13, line 49
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" [RFC7030] 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 The Pledge authenticates the voucher presented to it. During this o The Pledge authenticates the voucher presented to it. During this
authentication the Pledge ignores certificate lifetimes (by authentication the Pledge ignores certificate lifetimes (by
necessity because it does not have a clock). The voucher itself necessity because it does not have a realtime clock).
SHOULD contain the nonce included in the original request which
proves the voucher is fresh. o If the voucher contains a nonce then the Pledge MUST confirm the
nonce matches the original voucher request. This ensures the
voucher is fresh. See / (Section 3.2).
o Once the voucher is accepted the validity period of the o Once the voucher is accepted the validity period of the
domainCAcert in the voucher (see Section 7.3) now serves as a domainCAcert in the voucher (see Section 3.4) 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.
3.1.6. Enrollment 2.5. Cloud Registrar
As the final step of bootstrapping a Registrar helps to issue a
domain specific credential to the Pledge. For simplicity in this
document, a Registrar primarily facilitates issuing a credential by
acting as an RFC5280 Registration Authority for the Domain
Certification Authority.
Enrollment proceeds as described in [RFC7030]. Authentication of the
EST server is done using the Voucher rather than the methods defined
in EST.
Once the Voucher is received, as specified in this document, the
client has sufficient information to leverage the existing
communication channel with a Registrar to continue an EST RFC7030
enrollment. Enrollment picks up at RFC7030 section 4.1.1.
bootstrapping where the Voucher provides the "out-of-band" CA
certificate fingerprint (in this case the full CA certificate) such
that the client can now complete the TLS server authentication. At
this point the client continues with EST enrollment operations
including "CA Certificates Request", "CSR Attributes" and "Client
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
Functionality to provide generic "configuration" information is
supported. The parsing of this data and any subsequent use of the
data, for example communications with a Network Management System is
out of scope but is expected to occur after bootstrapping enrollment
is complete. This ensures that all communications with management
systems which can divulge local security information (e.g. network
topology or raw key material) is secured using the local credentials
issued during enrollment.
The Pledge uses bootstrapping to join only one domain. Management by
multiple domains is out-of-scope of bootstrapping. After the device
has successfully joined a domain and is being managed it is plausible
that the domain can insert credentials for other domains depending on
the device capabilities.
See Section 3.5.
3.2. Behavior of a Join Proxy
The role of the Proxy is to facilitate communications. The Proxy
forwards packets between the Pledge and a Registrar that has been
configured on the Proxy.
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,
the port number exposed by the proxy does not need to be well known,
or require an IANA allocation.
If the Proxy joins an Autonomic Control Plane
([I-D.ietf-anima-autonomic-control-plane]) it SHOULD use Autonomic
Control Plane secured GRASP ([I-D.ietf-anima-grasp]) to discovery the
Registrar address and port. As part of the discovery process, the
proxy mechanism (Circuit Proxy vs IPIP encapsulation) is agreed to
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
maximum variety of devices the chosen mechanism SHOULD use the
minimum amount of state on the proxy device. While many devices in
the ANIMA target space will be rather large routers, the proxy
function is likely to be implemented in the control plane CPU of such
a device, with available capabilities for the proxy function similar
to many class 2 IoT devices.
The document [I-D.richardson-anima-state-for-joinrouter] provides a
more extensive analysis of the alternative proxy methods.
3.2.1. CoAP connection to Registrar
The CoAP mechanism was depreciated.
3.2.2. HTTPS proxy connection to Registrar
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
connects the Pledge to a Registrar.
When the Proxy provides a circuit proxy to a Registrar the Registrar
MUST accept HTTPS connections.
When the Proxy provides a stateless IPIP encapsulation to a
Registrar, then the Registrar will have to perform IPIP
decapsulation, remembering the originating outer IPIP source address
in order to qualify the inner link-local address. This is a kind of
encapsulation and processing which is similar in many ways to how
mobile IP works.
Being able to connect a TCP (HTTP) or UDP (CoAP) socket to a link-
local address with an encapsulated IPIP header requires API
extensions beyond [RFC3542] for UDP use, and requires a form of
connection latching (see section 4.1 of [RFC5386] and all of
[RFC5660], except that a simple IPIP tunnel is used rather than an
IPsec tunnel).
3.3. Behavior of the Registrar
A Registrar listens for Pledges and determines if they can join the
domain. A Registrar obtains a Voucher from the MASA service and
delivers them to the Pledge as well as facilitating enrollment with
the domain PKI.
A Registrar is typically configured manually. When the Registrar
joins an Autonomic Control Plane
([I-D.ietf-anima-autonomic-control-plane]) it MUST respond to GRASP
([I-D.ietf-anima-grasp]) M_DISCOVERY message. See Section 6
Registrar behavior is as follows:
Contacted by Pledge
+
|
+-------v----------+
| Entity | fail?
| Authentication +---------+
+-------+----------+ |
| |
+-------v----------+ |
| Entity | fail? |
| Authorization +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Claiming the | fail? |
| Entity +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Log Verification | fail? |
| +--------->
+-------+----------+ |
| |
+-------v----------+ +----v-------+
| Forward | | |
| Voucher | | Reject |
| to the Pledge | | Device |
| | | |
+------------------+ +------------+
Figure 4
3.3.1. Pledge Authentication
The applicable authentication methods detailed in EST [RFC7030] are:
o the use of an X.509 IDevID credential during the TLS client
authentication,
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).
In order to validate the X.509 IDevID credential a Registrar
maintains a database of vendor trust anchors (e.g. vendor root
certificates or keyIdentifiers for vendor root public keys). For
user interface purposes this database can be mapped to colloquial
vendor names. Registrars can be shipped with the trust anchors of a
significant number of third-party vendors within the target market.
3.3.2. Pledge Authorization
In a fully automated network all devices must be securely identified
and authorized to join the domain.
A Registrar accepts or declines a request to join the domain, based
on the authenticated identity presented. Automated acceptance
criteria include:
o allow any device of a specific type (as determined by the X.509
IDevID),
o allow any device from a specific vendor (as determined by the
X.509 IDevID),
o allow a specific device from a vendor (as determined by the X.509
IDevID) against a domain white list. (The mechanism for checking
a shared white list potentially used by multiple Registrars is out
of scope).
To look the Pledge up in a domain white list a consistent method for
extracting device identity from the X.509 certificate is required.
RFC6125 describes Domain-Based Application Service identity but here
we require Vendor Device-Based identity. The subject field's DN
encoding MUST include the "serialNumber" attribute with the device's
unique serial number. In the language of RFC6125 this provides for a
SERIALNUM-ID category of identifier that can be included in a
certificate and therefore that can also be used for matching
purposes. The SERIALNUM-ID whitelist is collated according to vendor
trust anchor since serial numbers are not globally unique.
The Registrar MUST use the vendor provided MASA service to verify
that the device's history log does not include unexpected Registrars.
If a device had previously registered with another domain, a
Registrar of that domain would show in the log.
The authorization performed during BRSKI MAY be used for EST
enrollment requests by proceeding with EST enrollment using the
authenticated and authorized TLS connection. This minimizes the
number of cryptographic and protocol operations necessary to complete
bootstraping of the local key infrastructure.
3.3.3. Claiming the New Entity
Claiming an entity establishes an audit log at the MASA server and
provides a Registrar with proof, in the form of the Voucher, that the
log entry has been inserted. As indicated in Section 3.1.4 a Pledge
will only proceed with bootstrapping if a 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.
The Registrar obtains the MASA URI via static configuration or by
extracting it from the X.509 IDevID credential. See Section 2.3.
During initial bootstrapping the Pledge provides a nonce specific to
the particular bootstrapping attempt. The Registrar SHOULD include
this nonce when claiming the Pledge from the MASA service. Claims
from an unauthenticated Registrar are only serviced by the MASA
resource if a nonce is provided.
The Registrar can claim a Pledge that is not online by forming the
request using the entities unique identifier and not including a
nonce in the claim request. Vouchers obtained in this way do not
have a lifetime and they provide a permanent method for the domain to
claim the device. Evidence of such a claim is provided in the audit
log entries available to any future Registrar. Such claims reduce
the ability for future domains to secure bootstrapping and therefore
the Registrar MUST be authenticated by the MASA service although no
requirement is implied that the MASA associates this authentication
with ownership.
An Ownership Voucher requires the vendor to definitively know that a
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
attempt is made to claim a device that has a an Ownership Voucher.
3.3.4. Log Verification
A Registrar requests the log information for the Pledge from the MASA
service. The log is verified to confirm that the following is true
to the satisfaction of a Registrar's configured policy:
o Any nonceless entries in the log are associated with domainIDs
recognized by the registrar.
o Any nonce'd entries are older than when the domain is known to
have physical possession of the Pledge or that the domainIDs are
recognized by the registrar.
If any of these criteria are unacceptable to a Registrar the entity
is rejected. A Registrar MAY be configured to ignore the history of
the device but it is RECOMMENDED that this only be configured if
hardware assisted NEA [RFC5209] is supported.
This document specifies a simple log format as provided by the MASA
service to the registar. This format could be improved by
distributed consensus technologies that integrate vouchers with a
technologies such as block-chain or hash trees or the like. Doing so
is out of the scope of this document but are anticipated improvements
for future work.
3.4. Behavior of the MASA Service
The Manufacturer Authorized Signing Authority service is directly
provided by the manufacturer, or can be provided by a third party the
manufacturer authorizes. It is a cloud resource. The MASA service
provides the following functionalities to Registrars:
Issue Vouchers: In response to Registrar requests the MASA service
issues vouchers. Depending on the MASA policy the Registrar claim
of device ownership is either accepted or verified using out-of-
scope methods (that are expected to improve over time).
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.
Provide Logs: As a baseline implementation of the certified logging
mechanism the MASA is repsonsible for reporting logged
information. The current method involves trusting the MASA.
Other logging methods where the MASA is less trusted are expected
to be developed over time.
3.5. Leveraging the new key infrastructure / next steps
As the devices have a common trust anchor, device identity can be The Pledge MAY contact a well known URI of a cloud Registrar if a
securely established, making it possible to automatically deploy local Registrar can not be discovered or if the Pledge's target use
services across the domain in a secure manner. cases do not include a local Registrar.
Examples of services: If the Pledge uses a well known URI for contacting a cloud Registrar
an Implicit Trust Anchor database (see [RFC7030]) MUST be used to
authenticate service as described in RFC6125. This is consistent
with the human user configuration of an EST server URI in [RFC7030]
which also depends on RFC6125.
o Device management. 3. Protocol Details
o Routing authentication. The Pledge MUST initiate BRSKI after boot if it is unconfigured. The
Pledge MUST NOT automatically initiate BRSKI if it has been
configured or is in the process of being configured.
o Service discovery. BRSKI is described as extensions to EST [RFC7030] to reduce the
number of TLS connections and crypto operations required on the
Pledge. The Registrar implements the BRSKI REST interface within the
same .well-known URI tree as the existing EST URIs as described in
EST [RFC7030] section 3.2.2. A MASA URI is therefore "https://
authority "./well-known/est".
3.5.1. Network boundaries Establishment of the TLS connection for bootstrapping is as specified
in EST [RFC7030] section 4.1.1 "Bootstrap Distribution of CA
Certificates" [RFC7030] with the following extensions for automation:
When a device has joined the domain, it can validate the domain Automation extensions for the Pledge (equivalent to EST client) are:
membership of other devices. This makes it possible to create trust
boundaries where domain members have higher level of trusted than
external devices. Using the autonomic User Interface, specific
devices can be grouped into to sub domains and specific trust levels
can be implemented between those.
3.6. Interactions with Network Access Control o The Pledge provisionally accepts the Registrar certificate during
the TLS handshake as detailed in EST.
The assumption is that Network Access Control (NAC) completes using o If the Registrar responds with a redirection to other web origins
the Pledge 's X.509 IDevID credentials and results in the device the Pledge MUST follow only a single redirection. (EST supports
having sufficient connectivity to discovery and communicate with the redirection but does not allow redirections to other web origins
proxy. Any additional connectivity or quarantine behavior by the NAC without user input).
infrastructure is out-of-scope. After the devices has completed
bootstrapping the mechanism to trigger NAC to re-authenticate the
device and provide updated network privileges is also out-of-scope.
This achieves the goal of a bootstrap architecture that can integrate o The Registar MAY respond with an HTTP 202 ("the request has been
with NAC but does not require NAC within the network where it wasn't accepted for processing, but the processing has not been
previously required. Future optimizations can be achieved by completed") as described in EST [RFC7030] section 4.2.3 wherein
integrating the bootstrapping protocol directly into an initial EAP the client "MUST wait at least the specified 'retry-after' time
exchange. 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 (Appendix D.1.1.1) attempts. A Registrar that is unable
to complete the transaction the first time due to timing reasons
will have future chances.
4. Domain Operator Activities o The Pledge requests and validates a voucher using the new REST
calls described below.
This section describes how an operator interacts with a domain that o If necessary the Pledge calls the EST defined /cacerts method to
supports the bootstrapping as described in this document. obtain the current CA certificate. These are validated using the
Voucher.
4.1. Instantiating the Domain Certification Authority o The Pledge completes authentication of the server certificate as
detailed in Section 3.4.1. This moves the TLS connection out of
the provisional state. Optionally the TLS connection can now be
used for EST enrollment.
This is a one time step by the domain administrator. This is an "off The Pledge establishes the TLS connection with the Registrar through
the shelf" CA with the exception that it is designed to work as an the circuit proxy (see Appendix D.1.2) but the TLS connection is with
integrated part of the security solution. This precludes the use of the Registar; so in the above section the "Pledge" is the TLS client
3rd party certification authority services that do not provide and the "Registrar" is the TLS server. All security associations
support for delegation of certificate issuance decisions to a domain established are between the new device and the Registrar regardless
managed Registration Authority. of proxy operations.
4.2. Instantiating the Registrar The extensions for a Registrar (equivalent to EST server) are:
This is a one time step by the domain administrator. One or more o Client authentication is automated using Initial Device Identity.
devices in the domain are configured take on a Registrar function. The subject field's DN encoding MUST include the "serialNumber"
attribute with the device's unique serial number. In the language
of RFC6125 this provides for a SERIALNUM-ID category of identifier
that can be included in a certificate and therefore that can also
be used for matching purposes. The SERIALNUM-ID whitelist is
collated according to vendor trust anchor since serial numbers are
not globally unique.
A device can be configured to act as a Registrar or a device can o The Registrar requests and validates the Voucher from the vendor
auto-select itself to take on this function, using a detection authorized MASA service.
mechanism to resolve potential conflicts and setup communication with
the Domain Certification Authority. Automated Registrar selection is
outside scope for this document.
4.3. Accepting New Entities o The Registrar forwards the Voucher to the Pledge when requested.
For each Pledge the Registrar is informed of the unique identifier o The Registar performs log verifications in addition to local
(e.g. serial number) along with the manufacturer's identifying authorization checks before accepting optional Pledge device
information (e.g. manufacturer root certificate). This can happen in enrollment requests.
different ways:
1. Default acceptance: In the simplest case, the new device asserts 3.1. Discovery
its unique identity to a Registrar. The registrar accepts all
devices without authorization checks. This mode does not provide
security against intruders and is not recommended.
2. Per device acceptance: The new device asserts its unique identity The result of discovery is a logical communication with a Registrar,
to a Registrar. A non-technical human validates the identity, through a Proxy. The Proxy is transparent to the Pledge but is
for example by comparing the identity displayed by the registrar always assumed to exist.
(for example using a smartphone app) with the identity shown on
the packaging of the device. Acceptance may be triggered by a
click on a smartphone app "accept this device", or by other forms
of pairing. See also [I-D.behringer-homenet-trust-bootstrap] for
how the approach could work in a homenet.
3. Whitelist acceptance: In larger networks, neither of the previous To discover the Registrar the Pledge performs the following actions:
approaches is acceptable. Default acceptance is not secure, and
a manual per device methods do not scale. Here, the registrar is
provided a priori with a list of identifiers of devices that
belong to the network. This list can be extracted from an
inventory database, or sales records. If a device is detected
that is not on the list of known devices, it can still be
manually accepted using the per device acceptance methods.
4. Automated Whitelist: an automated process that builds the a. MUST: Obtains a local address using IPv6 methods as described in
necessary whitelists and inserts them into the larger network [RFC4862] IPv6 Stateless Address AutoConfiguration. [RFC7217] is
domain infrastructure is plausible. Once set up, no human encouraged. Pledges will generally prefer use of IPv6 Link-Local
intervention is required in this process. Defining the exact addresses, and discovery of Proxy will be by Link-Local
mechanisms for this is out of scope although the registrar mechanisms. [[EDNOTE: In some environments, a routable public
authorization checks is identified as the logical integration address may be obtained, should it be? Should it be used?]] IPv4
point of any future work in this area. methods are described in Appendix A
None of these approaches require the network to have permanent b. MUST: Listen for GRASP M_FLOOD ([I-D.ietf-anima-grasp])
Internet connectivity. Even when the Internet based MASA service is announcements of the objective: "ACP+Proxy". See section
used, it is possible to pre-fetch the required information from the Section 3.1.1 for the details of the the objective. The Pledge
MASA a priori, for example at time of purchase such that devices can may listen concurrently for other sources of information, see
enroll later. This supports use cases where the domain network may Appendix B.
be entirely isolated during device deployment.
Additional policy can be stored for future authorization decisions. Once a proxy is discovered the Pledge communicates with a Registrar
For example an expected deployment time window or that a certain through the proxy using the bootstrapping protocol defined in
Proxy must be used. Section 3.
4.4. Automatic Enrollment of Devices Each discovery method attempted SHOULD exponentially back-off
attempts (to a maximum of one hour) to avoid overloading the network
infrastructure with discovery. The back-off timer for each method
MUST be independent of other methods.
The approach outlined in this document provides a secure zero-touch Methods SHOULD be run in parallel to avoid head of queue problems
method to enroll new devices without any pre-staged configuration. wherein an attacker running a fake proxy or registrar can operate
New devices communicate with already enrolled devices of the domain, protocol actions intentionally slowly.
which proxy between the new device and a Registrar. As a result of
this completely automatic operation, all devices obtain a domain
based certificate.
4.5. Secure Network Operations Once a connection to a Registrar is established (e.g. establishment
of a TLS session key) there are expectations of more timely
responses, see Section 3.2.
The certificate installed in the previous step can be used for all Once all discovered services are attempted the device SHOULD return
subsequent operations. For example, to determine the boundaries of to listening for GRASP M_FLOOD. It should periodically retry the
the domain: If a neighbor has a certificate from the same trust vendor specific mechanisms. The Pledge MAY prioritize selection
anchor it can be assumed "inside" the same organization; if not, as order as appropriate for the anticipated environment.
outside. See also Section 3.5.1. The certificate can also be used
to securely establish a connection between devices and central
control functions. Also autonomic transactions can use the domain
certificates to authenticate and/or encrypt direct interactions
between devices. The usage of the domain certificates is outside
scope for this document.
5. Proxy Discovery Protocol Details 3.1.1. Proxy Discovery Protocol Details
The proxy uses the GRASP M_FLOOD mechanism to announce itself. This The proxy uses the GRASP M_FLOOD mechanism to announce itself. This
announcement is done with the same message as the ACP announcement announcement is done with the same message as the ACP announcement
detailed in [I-D.ietf-anima-autonomic-control-plane]. detailed in [I-D.ietf-anima-autonomic-control-plane].
proxy-objective = ["Proxy", [ O_IPv6_LOCATOR, ipv6-address, proxy-objective = ["Proxy", [ O_IPv6_LOCATOR, ipv6-address,
transport-proto, port-number ] ] transport-proto, port-number ] ]
ipv6-address - the v6 LL of the proxy ipv6-address - the v6 LL of the proxy
transport-proto - 6, for TCP 17 for UDP transport-proto - 6, for TCP 17 for UDP
port-number - the TCP or UDP port number to find the proxy port-number - the TCP or UDP port number to find the proxy
Figure 5 Figure 5
6. Registrar Discovery Protocol Details 3.1.2. Registrar Discovery Protocol Details
A Registrar is typically configured manually. When the Registrar
joins an Autonomic Control Plane
([I-D.ietf-anima-autonomic-control-plane]) it MUST respond to GRASP
([I-D.ietf-anima-grasp]) M_NEG_SYN message.
The registrar responds to discovery messages from the proxy (or GRASP The registrar responds to discovery messages from the proxy (or GRASP
caches between them) as follows: (XXX changed from M_DISCOVERY) caches between them) as follows: (XXX changed from M_DISCOVERY)
objective = ["AN_registrar", F_DISC, 255 ] objective = ["AN_registrar", F_DISC, 255 ]
discovery-message = [M_NEG_SYN, session-id, initiator, objective] discovery-message = [M_NEG_SYN, session-id, initiator, objective]
Figure 6: Registrar Discovery Figure 6: Registrar Discovery
The response from the registrar (or cache) will be a M_RESPONSE with The response from the registrar (or cache) will be a M_RESPONSE with
the following parameters: the following parameters:
response-message = [M_RESPONSE, session-id, initiator, ttl, response-message = [M_RESPONSE, session-id, initiator, ttl,
(+locator-option // divert-option), ?objective)] (+locator-option // divert-option), ?objective)]
initiator = ACP address of Registrar initiator = ACP address of Registrar
locator1 = [O_IPv6_LOCATOR, fd45:1345::6789, 6, 443] locator1 = [O_IPv6_LOCATOR, fd45:1345::6789, 6, 443]
locator2 = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683] locator2 = [O_IPv6_LOCATOR, fd45:1345::6789, 17, 5683]
locator3 = [O_IPv6_LOCATOR, fe80::1234, 41, nil] locator3 = [O_IPv6_LOCATOR, fe80::1234, 41, nil]
Figure 7: Registrar Response Figure 7: Registrar Response
The set of locators is to be interpreted as follows. A protocol of 6 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 indicates that TCP proxying on the indicated port is desired. A
protocol of 17 indicates that UDP proxying on the indicated port is protocol of 17 indicates that UDP proxying on the indicated port is
desired. In each case, the traffic SHOULD be proxied to the same desired. In each case, the traffic SHOULD be proxied to the same
port at the ULA address provided. port at the ULA address provided.
A protocol of 41 indicates that packets may be IPIP proxy'ed. The A protocol of 41 indicates that packets may be IPIP proxy'ed. In the
address in the locator In the case of that IPIP proxying is used, case of that IPIP proxying is used, then the provided link-local
then the provided link-local address MUST be advertised on the local address MUST be advertised on the local link using proxy neighbour
link using proxy neighbour discovery. The Join Proxy MAY limit discovery. The Join Proxy MAY limit forwarded traffic to the
forwarded traffic to the protocol (6 and 17) and port numbers protocol (6 and 17) and port numbers indicated by locator1 and
indicated by locator1 and locator2. The address to which the IPIP locator2. The address to which the IPIP traffic should be sent is
traffic should be sent is the initiator address (an ACP address of the initiator address (an ACP address of the Registrar), not the
the Registrar), not the address given in the locator. address given in the locator.
All Registrar MUST accept TCP / UDP traffic on the ports given at the Registrars MUST accept TCP / UDP traffic on the ports given at the
ACP address of the Registrar. If the Registrar supports IPIP ACP address of the Registrar. If the Registrar supports IPIP
tunnelling, it MUST also accept traffic encapsulated with IPIP. tunnelling, it MUST also accept traffic encapsulated with IPIP.
Registrars MUST accept HTTPS/EST traffic on the ports indicated. Registrars MUST accept HTTPS/EST traffic on the TCP ports indicated.
Registrars MAY accept DTLS/CoAP/EST traffic in addition. Registrars MAY accept DTLS/CoAP/EST traffic on the UDP in addition to
TCP traffic.
7. Protocol Details
A bootstrapping protocol could be implemented as an independent
protocol from EST, but for simplicity and to reduce the number of TLS
connections and crypto operations required on the Pledge, it is
described specifically as extensions to EST. These extensions MUST
be supported by the Registrar EST server within the same .well-known
URI tree as the existing EST URIs as described in EST [RFC7030]
section 3.2.2.
A MASA URI is therefore "https:// authority "./well-known/est". The
portion contained in the IDevID extension is only
"https://example.com" since everything after that is well known.
Establishment of the TLS connection for bootstrapping is as specified
for EST [RFC7030]. In particular server identity and client identity
are as described in EST [RFC7030] section 3.3. In EST [RFC7030]
provisional server authentication for bootstrapping is described in
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
certificate" or wherein a human user configures the URI of the EST
server for Implicit TA based authentication. This documented
establishes automated methods of authorizing the CA certificate using
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:
o The Pledge provisionally accept the EST server certificate during
the TLS handshake as detailed in Section 7.3.1.
o The Pledge requests and validates the Voucher as described below.
At this point the Pledge has sufficient information to validate
domain credentials.
o The Pledge calls the EST defined /cacerts method to obtain the
current CA certificate. These are validated using the Voucher.
o The Pledge completes bootstrapping as detailed in EST section
4.1.1.
In order to obtain a Voucher and associated logs a Registrar contacts
the MASA service Service using REST calls:
+-----------+ +----------+ +-----------+ +----------+
| New | | Circuit | | | | |
| Entity | | Proxy | | Registrar | | Vendor |
| | | | | | | |
++----------+ +--+-------+ +-----+-----+ +--------+-+
| | | |
| | | |
| TLS hello | TLS hello | |
Establish +---------------C---------------> |
TLS | | | |
connection | | Server Cert | |
<---------------C---------------+ |
| Client Cert | | |
+---------------C---------------> |
| | | |
HTTP REST | POST /requestvoucher | |
Data +--------------------nonce------> |
| . | /requestvoucher|
| . +---------------->
| <----------------+
| | /requestlog |
| +---------------->
| voucher <----------------+
<-------------------------------+ |
| (optional config information) | |
| . | |
| . | |
Figure 8
In some use cases the Registrar may need to contact the Vendor in
advanced, for example when the target network is air-gapped. The
nonceless request format is provided for this and the resulting flow
is slightly different. The security differences associated with not
knowing the nonce are discussed below:
+-----------+ +----------+ +-----------+ +----------+
| New | | Circuit | | | | |
| Entity | | Proxy | | Registrar | | Vendor |
| | | | | | | |
++----------+ +--+-------+ +-----+-----+ +--------+-+
| | | |
| | | |
| | | /requestvoucher|
| | (nonce +---------------->
| | unknown) <----------------+
| | | /requestlog |
| | +---------------->
| | <----------------+
| TLS hello | TLS hello | |
Establish +---------------C---------------> |
TLS | | | |
connection | | Server Cert | |
<---------------C---------------+ |
| Client Cert | | |
| | | |
HTTP REST | POST /requestvoucher | |
Data +----------------------nonce----> (discard |
| voucher | nonce) |
<-------------------------------+ |
| (optional config information) | |
| . | |
| . | |
Figure 9
The extensions for a Registrar server are as follows:
o The Registrar requests and validates the Voucher from the vendor
authorized MASA service.
o The Registrar forwards the Voucher to the Pledge when requested. 3.2. Request Voucher from the Registrar
o The Registar performs log verifications in addition to local When the Pledge bootstraps it makes a request for a Voucher from a
authorization checks before accepting the Pledge device. Registrar.
The provisional TLS connection introduces security risks that are This is done with an HTTPS POST using the operation path value of
addressed as follows: "/requestvoucher".
If the Registrar provides a redirect response the Pledge MUST follow The request is itself a voucher [I-D.ietf-anima-voucher]. The Pledge
the redirect but the connection remains provisional. The Pledge MUST populates the voucher fields as follows:
only follow a single redirection.
The Registar MAY respond with an HTTP 202 ("the request has been assertion: The voucher request MUST contain an assertion of
accepted for processing, but the processing has not been completed") "proximity". [[EDNOTE: this is a placeholder as this commit is
as described in EST [RFC7030] section 4.2.3 wherein the client "MUST not the correct place to expand this list. Using proximity and
wait at least the specified 'retry-after' time before repeating the channel binding: if both the Pledge and the Registrar sign the
same request". The Pledge is RECOMMENDED to provide local feed channel binding statement then these provide vital proximity
(blinked LED etc) during this wait cycle if mechanisms for this are information to the MASA. To be expanded on in a future commit.]]
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 created-on: Pledges that have a realtime clock are RECOMMENDED to
populate this field. This provides additional information to the
MASA.
When the Pledge bootstraps it makes a request for a Voucher from a nonce: The voucher request MUST contain a cryptographically strong
Registrar. random or pseudo-random number nonce. Doing so ensures
Section 2.4 functionality. The nonce MUST NOT be reused for
multiple bootstrapping attempts.
This is done with an HTTPS POST using the operation path value of All other fields MAY be ommitted in a voucher request. [[EDNOTE: An
"/requestvoucher". issue has been created for the voucher document to ensure normative
language supports this]]
The request format is JSON object containing a 64bit nonce generated Signing the request is RECOMMENDED if the Pledge has sufficient
by the client for each request. This nonce MUST be a processing to perform the crypto operations. Doing so allows the
cryptographically strong random or pseudo-random number that can not Registrar and MASA to confirm the "proximity" assertion of the
be easily predicted. The nonce MUST NOT be reused for multiple Pledge.
attempts to join a network domain. The nonce assures the Pledge that
the Voucher response is associated with this bootstrapping attempt
and is not a replay.
Request media type: application/voucherrequest Request media type: application/voucherrequest
Request format: a JSON file with the following: An example JWS payload of the voucher request:
{ {
"version":"1", "ietf-voucher:voucher": {
"nonce":"<64bit nonce value>", "nonce": "62a2e7693d82fcda2624de58fb6722e5",
"created-on": "2017-01-01T00:00:00.000Z",
"assertion": "proximity"
}
} }
[[EDNOTE: Even if the nonce was signed it would provide no defense [[EDNOTE: The move to JWT allows for relatively simple signing
against rogue registrars; although it would assure the MASA that a operations. One possibility here is to carry the original signed JWT
certified Pledge exists. To protect against rogue registrars a nonce as an optional part of the payload sent to the MASA (e.g. "original
component generated by the MASA (a new round trip) would be request"). this would be a BRSKI addition to the voucher?]]
required). Instead this is addressed by requiring MASA & Registrar
authentications but it is worth exploring additional protections.
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 3.3).
The received Voucher is forwarded to the Pledge. The received voucher request is forwarded to the Pledge.
7.2. Request Voucher from MASA 3.3. 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).
skipping to change at page 35, line 37 skipping to change at page 20, line 27
"/requestvoucher". "/requestvoucher".
Request media type: application/voucherrequest+cms 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. See Section 2.3. is extracted from the X.509 IDevID. See Section 2.2.
{ {
"version":"1", "ietf-voucher:voucher": {
"nonce":"<64bit nonce value>", "nonce": "62a2e7693d82fcda2624de58fb6722e5",
"IDevIDAuthorityKeyIdentifier":"<base64 encoded keyIdentifier">, "created-on": "2017-01-01T00:00:00.000Z",
"DevIDSerialNumber":"<id-at-serialNumber or base64 encoded "assertion": "proximity"
hardwareModuleName hwSerialNum>", "device-identifier-aki": "[[EDNOTE:authority key identifier field
from the IDevID. Voucher draft text that device-identifier is "A
unique identifier (e.g., serial number) within the scope of the
MASA" is insufficient because it prevents vendors from sharing
a MASA]]"
"device-identifier": "JADA123456789"
}
} }
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 Registrar as described in EST [RFC7030] section authenticate the Registrar as described in EST [RFC7030] section
3.3.2 to reduce the risk of DDoS attacks. The MASA performs 3.3.2 to reduce the risk of DDoS attacks. The MASA performs
authorization as detailed in Section 3.3.2. authorization as detailed in Appendix D.1.3.2.
As described in [I-D.ietf-anima-voucher] vouchers are normally short As described in [I-D.ietf-anima-voucher] vouchers are normally short
lived to avoid revocation issues. If the request is for a previous lived to avoid revocation issues. If the request is for a previous
(expired) voucher using the same Registrar (as determined by (expired) voucher using the same Registrar (as determined by
domainID) and the MASA has not been informed that the claim is no Registrar's' domainID) and the MASA has not been informed that the
longer valid - the request for a renewed voucher SHOULD be claim is invalid - the request for a renewed voucher SHOULD be
automatically authorized. If authorization is successful the MASA automatically authorized. If authorization is successful the MASA
responds with a [I-D.ietf-anima-voucher] voucher. The MASA SHOULD responds with a [I-D.ietf-anima-voucher] voucher. The MASA SHOULD
check for revocation of the Registrar certificate. The maximum check for revocation of the Registrar certificate. The maximum
lifetime of the voucher issued SHOULD NOT exceed the lifetime of the lifetime of the voucher issued SHOULD NOT exceed the lifetime of the
Registrar's revocation validation (for example if the Registrar Registrar's revocation validation (for example if the Registrar
revocation status is indicated in a CRL that is valid for two weeks revocation status is indicated in a CRL that is valid for two weeks
then that is an appropriate lifetime for the voucher). then that is an appropriate lifetime for the voucher).
The voucher request is encapsulated in a [RFC5652] Signed-data that The voucher request is signed by the Registrar as indicated in
is signed by the Registrar. The entire certificate chain, up to and [I-D.ietf-anima-voucher] voucher. The entire certificate chain, up
including the Domain CA, MUST be included in the CertificateSet to and including the Domain CA, MUST be included. The MASA service
structure. The MASA service checks the internal consistency of the checks the internal consistency of the voucher request but does not
CMS but does not authenticate the domain identity information. The authenticate the domain identity information since the domain is not
domain is not know to the MASA server in advance and a shared trust know to the MASA server in advance. The MASA server MUST verify that
anchor is not implied. The MASA server MUST verify that the CMS is the voucher request is signed by a Registrar certificate (by checking
signed by a Registrar certificate (by checking for the cmc-idRA for the cmc-idRA field) that was issued by the self signed root
field) that was issued by a the root certificate included in the CMS. certificate included in the request. [[ EDNOTE: can we simplify the
This ensures that the Registrar making the claim is an authorized above sentence? ]] This ensures that the Registrar making the claim
Registrar of the unauthenticated domain. is an authorized Registrar of the unauthenticated domain.
The root certificate is extracted and used to populate the Voucher. 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 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 extracted from the root certificate and is used to update the audit
log. log.
7.3. Voucher Response 3.4. 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. The server MUST answer with a contain an HTTP 200 response code. 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 (ASCII, english) error message containing explanatory
why the request was rejected. information describing why the request was rejected.
Response media type: application/voucher+cms Response media type: application/voucher+cms
The syntactic details of vouchers are described in detail in The syntactic details of vouchers are described in detail in
[I-D.ietf-anima-voucher]. For example, the voucher consists of: [I-D.ietf-anima-voucher]. For example, the voucher consists of:
{ {
"version":"1", "ietf-voucher:voucher": {
"nonce":"<64bit nonce value>", "nonce": "62a2e7693d82fcda2624de58fb6722e5",
"IDevIDAuthorityKeyIdentifier":"<base64 encoded keyIdentifier>", "assertion": "logging"
"DevIDSerialNumber":"<id-at-serialNumber>", "trusted-ca-certificate": "<base64 encoded certificate>"
"domainCAcert":"<the base64 encoded domain CA's certificate>" "device-identifier": "JADA123456789"
}
} }
The Voucher response is encapsulated in a [RFC5652] Signed-data that The Pledge verifies the signed voucher using the manufacturer
is signed by the MASA server. The Pledge verifies this signed installed trust anchor associated with the vendor's selected
message using the manufacturer installed trust anchor associated with Manufacturer Authorized Signing Authority.
the X.509 IDevID. [[EDNOTE: As detailed in netconf-zerotouch this
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
document as well.]]
The 'domainCAcert' element of this message contains the domain CA's The 'trusted-ca-certificate' element of the voucher contains the
public key. This is specific to bootstrapping a public key domain CA's public key. This is useful for bootstrapping a public
infrastructure. To support bootstrapping other key infrastructures key infrastructure but to support bootstrapping other key
additional domain identity types might be defined in the future. infrastructures additional domain identity types might be defined in
Clients MUST be prepared to ignore additional fields they do not the future.
recognize. Clients MUST be prepared to parse and fail gracefully
from an Voucher response that does not contain a 'domainCAcert' field
at all.
To minimize the size of the Voucher response message the domainCAcert The pledge's EST clients MUST be prepared to ignore additional fields
is not a complete distribution of the EST section 4.1.3 CA they do not recognize.
Certificate Response. The Pledge installs the domainCAcert trust
anchor. As indicated in Section 3.1.2 the newly installed trust
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.
7.3.1. Completing authentication of Provisional TLS connection the pledge MUST be prepared to parse and fail gracefully from an
Voucher response that does not contain a 'trusted-ca-certificate'
field at all.
If a Registrar's credential can not be verified using the The Pledge MUST use the 'trusted-ca-certificate' trust anchor to
domainCAcert trust anchor the TLS connection is immediately discarded immediately complete authentication of the provisional TLS
and the Pledge abandons attempts to bootstrap with this discovered connection.
registrar.
The following behaviors on a Registrar and Pledge are in addition to 3.4.1. Completing authentication of Provisional TLS connection
normal PKIX operations:
o The EST server MUST use a certificate that chains to the If a Registrar's credentials can not be verified using the trusted-
domainCAcert. This means that when the EST server obtains renewed ca-certificate trust anchor from the voucher then the TLS connection
credentials the credentials included in the Section 7.2 request is immediately discarded and the Pledge abandons attempts to
match the chain used in the current provisional TLS connection. bootstrap with this discovered registrar. The pledge SHOULD send
voucher status telemetry (described below) before closing the TLS
connection. The pledge MUST attempt to enroll using any other
proxies it has found. It SHOULD return to the same proxy again after
attempting with other proxies. Attempts should be attempted in the
exponential backoff described earlier. Attempts SHOULD be repeated
as failure may be the result of a temporary inconsistently (an
inconsistently rolled Registrar key, or some other mis-
configuration). The inconsistently could also be the result an
active MITM attack on the EST connection.
o The Pledge PKIX path validation of a Registrar validity period To ensure that the trusted-ca-certificate provide chain is able to
information is as described in Section 3.1.5. verify, the Registrar MUST use a certificate that chains to the
trusted-ca-certificate.
Because the domainCAcert trust anchor is installed as an Explicit The Pledge's PKIX path validation of a Registrar certificate's
Trust Anchor it can be used to authenticate any dynamically validity period information is as described in Section 2.4. Beyond
discovered EST server that contain the id-kp-cmcRA extended key usage that once PKIX path validation is successful the TLS connection is no
extension as detailed in EST RFC7030 section 3.6.1; but to reduce longer provisional.
system complexity the Pledge SHOULD avoid additional discovery
operations. Instead the Pledge SHOULD communicate directly with the
Registrar as the EST server to complete PKI local certificate
enrollment. Additionally the Pledge SHOULD use the existing TLS
connection to proceed with EST enrollment, thus reducing the total
amount of cryptographic and round trip operations required during
bootstrapping. [[EDNOTE: It is reasonable to mandate that the
existing TLS connection be re-used? e.g. MUST >> SHOULD?]]
7.4. Voucher Status Telemetry The trusted-ca-certificate is installed as an Explicit Trust Anchor
for future operations. It can therefore can be used to authenticate
any dynamically 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 system complexity the Pledge SHOULD avoid
additional discovery operations. Instead the Pledge SHOULD
communicate directly with the Registrar as the EST server for future
key management operations. The 'trusted-ca-certificate' is not a
complete distribution of the EST section 4.1.3 CA Certificate
Response which is an additional justification for the recommendation
to proceed with EST key management operations.
For automated bootstrapping of devices the adminstrative elements 3.5. Voucher Status Telemetry
providing bootstrapping also provide indications to the system
The domain is expected to 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 it needs telemetry information concerning the device's status.
device's status.
To indicate Pledge status regarding the Voucher the client SHOULD To indicate Pledge status regarding the Voucher the client SHOULD
post a status message. post a status message.
The posted data media type: application/json 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
joining the domain. joining the domain.
[[EDNOTE: the server can know which pledge failed by the previous
voucher, I think. Is this worth noting?]]
{ {
"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.
7.5. MASA authorization log Request 3.6. 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. If a device had previously registered with
another domain, a Registrar of that domain would show in the log.
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 MUST HTTP POSTs the same Voucher Request as for requesting The client MUST HTTP POSTs the same Voucher Request as for requesting
a Voucher. It is posted to the /requestauditlog URI instead. The a Voucher. It is posted to the /requestauditlog URI instead. The
IDevIDAuthorityKeyIdentifier and DevIDSerialNumber informs the MASA IDevIDAuthorityKeyIdentifier and DevIDSerialNumber informs the MASA
server which log is requested so the appropriate log can be prepared server which log is requested so the appropriate log can be prepared
for the response. Using the same media type and message minimizes for the response. Using the same media type and message minimizes
cryptographic and message operations although it results in cryptographic and message operations although it results in
additional network traffic. The relying MASA server implementation additional network traffic. The relying MASA server implementation
MAY leverage internal state to associate this request with the MAY leverage internal state to associate this request with the
original, and by now already validated, voucher request so as to original, and by now already validated, voucher request so as to
avoid an extra crypto validation. avoid an extra crypto validation.
Request media type: application/voucherrequest+cms Request media type: application/voucherrequest+cms
7.6. MASA authorization log Response 3.7. 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 40, line 27 skipping to change at page 25, line 27
within the CMS of the audit voucher request>", within the CMS of the audit voucher request>",
"nonce":"<any nonce if supplied (or the exact string 'NULL')>" "nonce":"<any nonce if supplied (or the exact string 'NULL')>"
} }
] ]
} }
Distribution of a large log is less than ideal. This structure can Distribution of a large log is less than ideal. This structure can
be optimized as follows: All nonce-less entries for the same domainID be optimized as follows: All nonce-less entries for the same domainID
MAY be condensed into the single most recent nonceless entry. MAY be condensed into the single most recent nonceless entry.
A Registrar uses this log information to make an informed decision A Registrar SHOULD use this log information to make an informed
regarding the continued bootstrapping of the Pledge. For example if decision regarding the continued bootstrapping of the Pledge. For
the log includes unexpected domainIDs this is indicative of example if the log includes unexpected domainIDs this is indicative
problematic imprints by the Pledge. If the log includes nonce-less of problematic imprints by the Pledge. If the log includes nonce-
entries this is indicative of the permanent ability for the indicated less entries this is indicative of the permanent ability for the
domain to trigger a reset of the device and take over management of indicated domain to trigger a reset of the device and take over
it. Equipment that is purchased pre-owned can be expected to have an management of it. Equipment that is purchased pre-owned can be
extensive history. expected to have an extensive history. A Registrar MAY request logs
at future times [[EDNOTE: we need to ensure MASA server is not
slammed with too many requests]]. A Registrar MAY be configured to
ignore the history of the device but it is RECOMMENDED that this only
be configured if hardware assisted NEA [RFC5209] is supported.
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.
7.7. EST Integration for PKI bootstrapping This document specifies a simple log format as provided by the MASA
service to the registar. This format could be improved by
distributed consensus technologies that integrate vouchers with a
technologies such as block-chain or hash trees or the like. Doing so
is out of the scope of this document but are anticipated improvements
for future work. As such, the Registrar client SHOULD anticipate new
kinds of responses, and SHOULD provide operator controls to indicate
how to process unknown responses.
The prior sections describe EST extensions necessary to enable fully 3.8. EST Integration for PKI bootstrapping
This section describes EST extensions necessary to enable fully
automated bootstrapping. Although the 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 Once the Voucher is received, as specified in this document, the
trust anchor representative of the Domain. The following section client has sufficient information to leverage the existing
describe using EST to obtain a locally issued PKI certificate. The communication channel with a Registrar to continue an EST RFC7030
Pledge SHOULD leverage the discovered Registrar to proceed with enrollment. The Pledge SHOULD use the existing current TLS
certificate enrollment and, if they do, MUST implement the EST connection to proceed with EST enrollment, thus reducing the total
options described in this section. The Pledge MAY perform amount of cryptographic and round trip operations required during
alternative enrollment methods including discovering an alternate EST bootstrapping (enrollment picks up after EST RFC7030 "Bootstrap
server, or proceed to use its X.509 IDevID credential indefinitely. Distribution of CA Certificates" and the client continues with EST
enrollment operations including "CA Certificates Request", "CSR
Attributes" and "Client Certificate Request" or "Server-Side Key
Generation").
7.7.1. EST Distribution of CA Certificates The Pledge is RECOMMENDED to implement the following EST automation
extensions. They supplement the RFC7030 EST to better support
automated devices that do not have an end user.
[[EDNOTE:might be best to discuss in CSR attributes?]]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.
3.8.1. 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 7.3 for a certificates beyond the domainCAcert (see Section 3.4 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.
7.7.2. EST CSR Attributes 3.8.2. 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 X.509 IDevID information known to the Pledge (essentially the X.509 IDevID
information) and ultimately receives a certificate containing domain information) and ultimately receives a certificate containing domain
specific identity information. Conceptually the CA has complete specific identity information. Conceptually the CA has complete
control over all fields issued in the end entity certificate. control over all fields issued in the end entity certificate.
Realistically this is operationally difficult with the current status Realistically this is operationally difficult with the current status
of PKI certificate authority deployments where the CSR is submitted of PKI certificate authority deployments where the CSR is submitted
skipping to change at page 42, line 9 skipping to change at page 27, line 42
concerning this functionality. [[EDNOTE: extensive use of EST CSR concerning this functionality. [[EDNOTE: extensive use of EST CSR
Attributes 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.
7.7.3. EST Client Certificate Request 3.8.3. 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.
7.7.4. Enrollment Status Telemetry 3.8.4. 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 FAIL the Reason string indicates why the most recent In the case of a FAIL the Reason string indicates why the most recent
enrollment failed. The SubjectKeyIdentifier field MUST be included enrollment failed. The SubjectKeyIdentifier field MUST be included
if the enrollment attempt was for a keypair that is locally known to if the enrollment attempt was for a keypair that is locally known to
the client. If EST /serverkeygen was used and failed then the field the client. If EST /serverkeygen was used and failed then the field
is ommited from the status telemetry. is omitted from the status telemetry.
In the case of a SUCCESS the Reason string is ommitted. The In the case of a SUCCESS the Reason string is omitted. The
SubjectKeyIdentifier is included so that the server can record the SubjectKeyIdentifier is included so that the server can record the
successful certificate distribution. successful certificate distribution.
Status media type: application/json 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. received 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 simply 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.
7.7.5. EST over CoAP 3.8.5. 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].]]
8. Reduced security operational modes 4. 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.
8.1. Trust Model 4.1. Trust Model
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
| New | | Circuit | | Domain | | Vendor | | New | | Circuit | | Domain | | Vendor |
| Entity | | Proxy | | Registrar | | Service | | Entity | | Proxy | | Registrar | | Service |
| | | | | | | (Internet | | | | | | | | (Internet |
+--------+ +---------+ +------------+ +------------+ +--------+ +---------+ +------------+ +------------+
Figure 10 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 44, line 29 skipping to change at page 30, line 11
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.
8.2. New Entity security reductions 4.2. 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.
8.3. Registrar security reductions 4.3. 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 X.509 IDevID credential MAY form the Section 7.1 request using an X.509 IDevID credential MAY form the Section 3.2 request using
the Section 7.2 format to ensure the Pledge's serial number the Section 3.3 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 refuse 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 Vouchers from the MASA service 3. A Registrar MAY request nonce-less Vouchers from the MASA service
(by not including a nonce in the request). These Vouchers can (by not including a nonce in the request). These Vouchers can
then be transmitted to the Registrar and stored until they are then be transmitted to the Registrar and stored until they are
needed during bootstrapping operations. This is for use cases needed during bootstrapping operations. This is for use cases
where target network is protected by an air gap and therefore can where target network is protected by an air gap and therefore can
not contact the MASA service during Pledge deployment. not contact the MASA service during Pledge deployment.
4. A registrar MAY ignore unrecognized nonce-less log entries. This 4. A registrar MAY ignore unrecognized nonce-less log entries. This
could occur when used equipment is purchased with a valid history could occur when used equipment is purchased with a valid history
being deployed in air gap networks that required permanent being deployed in air gap networks that required permanent
Vouchers. Vouchers.
8.4. MASA security reductions 4.4. 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 Voucher. This results in 1. Not enforcing that a nonce is in the Voucher. This results in
distribution of Voucher that never expires and in effect makes distribution of Voucher that never expires and in effect makes
the Domain an always trusted entity to the Pledge during any the Domain an always trusted entity to the Pledge during any
skipping to change at page 46, line 20 skipping to change at page 31, line 49
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 an enhanced level of use this functionality only in concert with an enhanced level of
ownership tracking (out-of-scope). If the Pledge device is known 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 to have a real-time-clock that is set from the factory use of a
voucher validity period is RECOMMENDED. voucher validity period is RECOMMENDED.
2. Not verifying ownership before responding with an Voucher. This 2. Not verifying ownership before responding with an Voucher. This
is expected to be a common operational model because doing so is expected to be a common operational model because doing so
relieves the vendor providing MASA services from having to relieves the vendor providing MASA services from having to track
tracking ownership during shipping and supply chain and allows ownership during shipping and supply chain and allows for a very
for a very low overhead MASA service. A Registrar uses the audit low overhead MASA service. A Registrar uses the audit log
log information as a defense in depth strategy to ensure that information as a defense in depth strategy to ensure that this
this does not occur unexpectedly (for example when purchasing new 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).
9. Security Considerations 5. IANA Considerations
5.1. PKIX Registry
This document requests a number for id-mod-MASAURLExtn2016(TBD) from
the pkix(7) id-mod(0) Registry. [[EDNOTE: fix names]]
This document requests a number from the id-pe registry for id-pe-
masa-url. XXX
6. Security Considerations
There are uses cases where the MASA could be unavailable or There are uses cases where the MASA could be unavailable or
uncooperative to the Registrar. They include planned and unplanned uncooperative to the Registrar. They include planned and unplanned
network partitions, changes to MASA policy, or other instances where network partitions, changes to MASA policy, or other instances where
MASA policy rejects a claim. These introduce an operational risk to MASA policy rejects a claim. These introduce an operational risk to
the Registrar owner that MASA/vendor behavior might limit the ability the Registrar owner that MASA/vendor behavior might limit the ability
to re-boostrap a Pledge device. For example this might be an issue to re-boostrap a Pledge device. For example this might be an issue
during disaster recovery. This risk can be mitigated by Registrars during disaster recovery. This risk can be mitigated by Registrars
that request and maintain long term copies of "nonceless" Vouchers. that request and maintain long term copies of "nonceless" Vouchers.
In that way they are guaranteed to be able to repeat bootstrapping In that way they are guaranteed to be able to repeat bootstrapping
skipping to change at page 47, line 13 skipping to change at page 33, line 4
resistant recovery and security of future bootstrapping. Registrars resistant recovery and security of future bootstrapping. Registrars
take the Pledge's audit history into account when applying policy to take the Pledge's audit history into account when applying policy to
new devices. new devices.
The MASA server is exposed to DoS attacks wherein attackers claim an The MASA server is exposed to DoS attacks wherein attackers claim an
unbounded number of devices. Ensuring a Registrar is representative unbounded number of devices. Ensuring a Registrar is representative
of a valid vendor customer, even without validating ownership of of a valid vendor customer, even without validating ownership of
specific Pledge devices, helps to mitigate this. Inserting a specific Pledge devices, helps to mitigate this. Inserting a
cryptographic proof-of-possession step to the protocol operations is cryptographic proof-of-possession step to the protocol operations is
a possible area of future work. One method that would not introduce a possible area of future work. One method that would not introduce
additional round-trips would be for the Registrar to share the Plege- additional round-trips would be for the Registrar to share the
Registrar TLS handshake with the MASA service when requesting a Pledge-Registrar TLS handshake with the MASA service when requesting
voucher. Doing so would allow the MASA service to verify that the a voucher. Doing so would allow the MASA service to verify that the
Registrar's Server Certificate was signed by the Pledge's Certificate Registrar's Server Certificate was signed by the Pledge's Certificate
Verify message (which covers the entire handshake). Verify message (which covers the entire handshake). [[EDNOTE:
Security Considerations should not offer up new protocol ideas
without a reason for having not done it...]]
It is possible for an attacker to request a voucher from the MASA It is possible for an attacker to request a voucher from the MASA
service directly after the real Registrar obtains an audit log. If service directly after the real Registrar obtains an audit log. If
the attacker could also force the bootstrapping protocol to reset the attacker could also force the bootstrapping protocol to reset
there is a theoretical opportunity for the attacker to use their there is a theoretical opportunity for the attacker to use their
voucher to take control of the Pledge but then proceed to enroll with voucher to take control of the Pledge but then proceed to enroll with
the target domain. Possible prevention mechanisms include: 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.
skipping to change at page 47, line 41 skipping to change at page 33, line 34
To facilitate logging and administrative oversight the Pledge reports To facilitate logging and administrative oversight the Pledge reports
on Voucher parsing status to the Registrar. In the case of a failure on Voucher parsing status to the Registrar. In the case of a failure
this information is informative to a potentially malicious Registar this information is informative to a potentially malicious Registar
but this is RECOMMENDED anyway because of the operational benefits of but this is RECOMMENDED anyway because of the operational benefits of
an informed administrator in cases where the failure is indicative of an informed administrator in cases where the failure is indicative of
a problem. a problem.
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 8 to a statement that clients only model have been reduced in Section 4 to a statement that clients only
"SHOULD" support such a model. This reflects current (poor) "SHOULD" support such a model. This reflects current (poor)
practices that are NOT RECOMMENDED. practices that are NOT RECOMMENDED.
During the provisional period of the connection all HTTP header and During the provisional period of the connection all HTTP header and
content data MUST treated as untrusted data. HTTP libraries are content data MUST treated as untrusted data. HTTP libraries are
regularly exposed to non-secured HTTP traffic. regularly exposed to non-secured HTTP traffic: mature libraries
should not have any problems.
10. Acknowledgements Pledge's might chose to engage in protocol operations with multiple
discovered Registrars in parallel. As noted above they will only do
so with distinct nonce values, but the end result could be multple
voucher's issued from the MASA if all registrars attempt to claim the
device. This is not a failure and the Pledge choses whichever
voucher to accept based on internal logic. The Registrar's verifying
log information will see multiple entries and take this into account
for their analytics purposes.
7. Acknowledgements
We would like to thank the various reviewers for their input, in We would like to thank the various reviewers for their input, in
particular Brian Carpenter, Toerless Eckert, Fuyu Eleven, Eliot Lear, particular Brian Carpenter, Toerless Eckert, Fuyu Eleven, Eliot Lear,
Sergey Kasatkin, Markus Stenberg, and Peter van der Stok Sergey Kasatkin, Markus Stenberg, and Peter van der Stok
11. References 8. References
11.1. Normative References 8.1. Normative References
[I-D.ietf-anima-autonomic-control-plane] [I-D.ietf-anima-autonomic-control-plane]
Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic
Control Plane", draft-ietf-anima-autonomic-control- Control Plane", draft-ietf-anima-autonomic-control-
plane-05 (work in progress), January 2017. plane-06 (work in progress), March 2017.
[I-D.ietf-anima-voucher] [I-D.ietf-anima-voucher]
Watsen, K., Richardson, M., Pritikin, M., and T. Eckert, Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
"Voucher and Voucher Revocation Profiles for Bootstrapping "Voucher Profile for Bootstrapping Protocols", draft-ietf-
Protocols", draft-ietf-anima-voucher-00 (work in anima-voucher-02 (work in progress), March 2017.
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>.
[RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei, [RFC3542] Stevens, W., Thomas, M., Nordmark, E., and T. Jinmei,
"Advanced Sockets Application Program Interface (API) for "Advanced Sockets Application Program Interface (API) for
IPv6", RFC 3542, DOI 10.17487/RFC3542, May 2003, IPv6", RFC 3542, DOI 10.17487/RFC3542, May 2003,
<http://www.rfc-editor.org/info/rfc3542>. <http://www.rfc-editor.org/info/rfc3542>.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, Ed., "Extensible Authentication Protocol
(EAP)", RFC 3748, DOI 10.17487/RFC3748, June 2004,
<http://www.rfc-editor.org/info/rfc3748>.
[RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
Configuration of IPv4 Link-Local Addresses", RFC 3927, Configuration of IPv4 Link-Local Addresses", RFC 3927,
DOI 10.17487/RFC3927, May 2005, DOI 10.17487/RFC3927, May 2005,
<http://www.rfc-editor.org/info/rfc3927>. <http://www.rfc-editor.org/info/rfc3927>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007, DOI 10.17487/RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>. <http://www.rfc-editor.org/info/rfc4862>.
skipping to change at page 49, line 42 skipping to change at page 35, 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>.
11.2. Informative References 8.2. 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-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-09 (work in progress), December 2016. grasp-12 (work in progress), May 2017.
[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-12 (work in progress), January 2017. netconf-zerotouch-13 (work in progress), March 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.
skipping to change at page 54, line 48 skipping to change at page 40, line 48
just pay attention to this extra information and add an appropriate just pay attention to this extra information and add an appropriate
IPIP header on outgoing. A CoAP over UDP mechanism may need to IPIP header on outgoing. A CoAP over UDP mechanism may need to
expose this extra information to the application as the UDP sockets expose this extra information to the application as the UDP sockets
are often not connected, and the application will need to specify the are often not connected, and the application will need to specify the
outgoing path on each packet send. outgoing path on each packet send.
Such an additional socket mechanism has not been standardized. Such an additional socket mechanism has not been standardized.
Terminating L2TP connections over IPsec transport mode suffers from Terminating L2TP connections over IPsec transport mode suffers from
the same challenges. the same challenges.
Appendix D. To be deprecated: Consolidation remnants
[[EDNOTE: As per working group feedback there were multiple instances
where this document repeated itself. To address this we have moved
all text to this appendix and restored only one copy of each
normative discussion. The next pass will reduce and delete this
appendix to '0'; although some may be maintained in a design
considerations appendix.]]
D.1. Functional Overview
Entities behave in an autonomic fashion. They discover each other
and autonomically bootstrap into a key infrastructure delineating the
autonomic domain. See [RFC7575] for more information.
This section details the state machine and operational flow for each
of the main three entities. The pledge, the domain (primarily a
Registrar) and the MASA service.
A representative flow is shown in Figure 2:
+--------+ +---------+ +------------+ +------------+
| Pledge | | Circuit | | Domain | | Vendor |
| | | Proxy | | Registrar | | Service |
| | | | | | | (Internet |
+--------+ +---------+ +------------+ +------------+
| | | |
|<-RFC3927 IPv4 adr | Appendix A | |
or|<-RFC4862 IPv6 adr | | |
| | | |
|-------------------->| | |
| optional: mDNS query| Appendix B | |
| RFC6763/RFC6762 | | |
| | | |
|<--------------------| | |
| GRASP M_FLOOD | | |
| periodic broadcast| | |
| | | |
|<------------------->C<----------------->| |
| TLS via the Circuit Proxy | |
|<--Registrar TLS server authentication---| |
[PROVISIONAL accept of server cert] | |
P---X.509 client authentication---------->| |
P | | |
P---Request Voucher (include nonce)------>| |
P | | |
P | /---> | |
P | | [accept device?] |
P | | [contact Vendor] |
P | | |--Pledge ID-------->|
P | | |--Domain ID-------->|
P | | |--optional:nonce--->|
P | | | [extract DomainID]
P | | | |
P | optional: | [update audit log]
P | |can | |
P | |occur | |
P | |in | |
P | |advance | |
P | | | |
P | | |<-device audit log--|
P | | |<- voucher ---------|
P | \----> | |
P | | |
P | [verify audit log and voucher] |
P | | |
P<------voucher---------------------------| |
[verify voucher ] | | |
[verify provisional cert| | |
| | | |
|<--------------------------------------->| |
| Continue with RFC7030 enrollment | |
| using now bidirectionally authenticated | |
| TLS session. | | |
| | | |
| | | |
| | | |
Figure 2
[[UNRESOLVED:need to restore some functional overview section for all
these diagrams]]In order to obtain a Voucher and associated logs a
Registrar contacts the MASA service Service using REST calls:
+-----------+ +----------+ +-----------+ +----------+
| New | | Circuit | | | | |
| Entity | | Proxy | | Registrar | | Vendor |
| | | | | | | |
++----------+ +--+-------+ +-----+-----+ +--------+-+
| | | |
| | | |
| TLS hello | TLS hello | |
Establish +---------------C---------------> |
TLS | | | |
connection | | Server Cert | |
<---------------C---------------+ |
| Client Cert | | |
+---------------C---------------> |
| | | |
HTTP REST | POST /requestvoucher | |
Data +--------------------nonce------> |
| . | /requestvoucher|
| . +---------------->
| <----------------+
| | /requestlog |
| +---------------->
| voucher <----------------+
<-------------------------------+ |
| (optional config information) | |
| . | |
| . | |
Figure 8
In some use cases the Registrar may need to contact the Vendor in
advanced, for example when the target network is air-gapped. The
nonceless request format is provided for this and the resulting flow
is slightly different. The security differences associated with not
knowing the nonce are discussed below:
+-----------+ +----------+ +-----------+ +----------+
| New | | Circuit | | | | |
| Entity | | Proxy | | Registrar | | Vendor |
| | | | | | | |
++----------+ +--+-------+ +-----+-----+ +--------+-+
| | | |
| | | |
| | | /requestvoucher|
| | (nonce +---------------->
| | unknown) <----------------+
| | | /requestlog |
| | +---------------->
| | <----------------+
| TLS hello | TLS hello | |
Establish +---------------C---------------> |
TLS | | | |
connection | | Server Cert | |
<---------------C---------------+ |
| Client Cert | | |
| | | |
HTTP REST | POST /requestvoucher | |
Data +----------------------nonce----> (discard |
| voucher | nonce) |
<-------------------------------+ |
| (optional config information) | |
| . | |
| . | |
Figure 9
D.1.1. Behavior of a Pledge
A pledge that has not yet been bootstrapped attempts to find a local
domain and join it. A pledge [[RESOLVED:MUST NOT]] automatically
initiate bootstrapping if it has already been configured or is in the
process of being configured.
States of a pledge are as follows:
+--------------+
| Start |
| |
+------+-------+
|
+------v-------+
| Discover |
+------------> |
| +------+-------+
| |
| +------v-------+
| | Identity |
^------------+ |
| rejected +------+-------+
| |
| +------v-------+
| | Request |
| | Join |
| +------+-------+
| |
| +------v-------+
| | Imprint | Optional
^------------+ <--+Manual input (Appendix C)
| Bad Vendor +------+-------+
| response |
| +------v-------+
| | Enroll |
^------------+ |
| Enroll +------+-------+
| Failure |
| +------v-------+
| | Being |
^------------+ Managed |
Factory +--------------+
reset
Figure 3
State descriptions for the pledge are as follows:
1. Discover a communication channel to a Registrar.
2. Identify itself. This is done by presenting an X.509 IDevID
credential to the discovered Registrar (via the Proxy) in a TLS
handshake. (The Registrar credentials are only provisionally
accepted at this time).
3. Requests to Join the discovered Registrar. A unique nonce
[[RESOLVED:can be]] included ensuring that any responses can be
associated with this particular bootstrapping attempt.
4. Imprint on the Registrar. This requires verification of the
vendor service provided voucher. A voucher contains sufficient
information for the Pledge to complete authentication of a
Registrar. (It enables the Pledge to finish authentication of
the Registrar TLS server certificate).
5. Enroll. By accepting the domain specific information from a
Registrar, and by obtaining a domain certificate from a Registrar
using a standard enrollment protocol, e.g. Enrollment over
Secure Transport (EST) [RFC7030].
6. The Pledge is now a member of, and can be managed by, the domain
and will only repeat the discovery aspects of bootstrapping if it
is returned to factory default settings.
The following sections describe each of these steps in more detail.
D.1.1.1. Discovery
[[RESOLVED:TEXT moved up into above]]
D.1.1.2. Identity
The Pledge identifies itself during the communication protocol
handshake. If the client identity is rejected (that is, the TLS
handshake does not complete) the Pledge repeats the Identity process
using the next proxy or discovery method available.
[[RESOLVED: need normative statement in protocol section]] The
bootstrapping protocol server is not initially authenticated. Thus
the connection is provisional and all data received is untrusted
until sufficiently validated even though it is over a TLS connection.
This is aligned with the existing provisional mode of EST [RFC7030]
during s4.1.1 "Bootstrap Distribution of CA Certificates". See
Section 3.4 for more information about when the TLS connection
authentication is completed.
[[RESOLVED:]]All security associations established are between the
new device and the Bootstrapping server regardless of proxy
operations.
D.1.1.2.1. Concurrent attempts to join
[[RESOLVED: by dropping this text. the "priority mechanism" is
unspecified thus any discussion is unclear. Not only that once an
initial request is sent to the registrar the question of multiple
MASA interactions has already occurred. Nothing breaks if
implementations do this. I've added text to the security
considerations indicating the end result (MASA entries that might be
ignored by the device but which confuse the end administrator)]] 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.
D.1.1.3. Request Join
The Pledge POSTs a request to join the domain to the Bootstrapping
server. This request contains a Pledge generated nonce and informs
the Bootstrapping server which imprint methods the Pledge will
accept.
The nonce ensures the Pledge can verify that responses are specific
to this bootstrapping attempt. This minimizes the use of global time
and provides a substantial benefit for devices without a valid clock.
D.1.1.3.1. Redirects during the Join Process
[[RESOVED via current root protocol discussion. reference to
mdnsmethods is dropped]] EST [RFC7030] describes situations where the
bootstrapping server MAY redirect the client to an alternate server
via a 3xx status code. 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.
D.1.1.4. Imprint
The Pledge validates the voucher and accepts the Registrar ID. The
provisional TLS connection is validated using the Registrar ID from
the voucher.
D.1.1.5. Lack of realtime clock APPENDIX
[[RESOVED: entire section promoted back into the main text]]
Many devices when bootstrapping do not have knowledge of the current
time. Mechanisms like Network Time Protocols can not be secured
until bootstrapping is complete. Therefore bootstrapping is defined
in a method that does not require knowledge of the current time.
Unfortunately there are moments during bootstrapping when
certificates are verified, such as during the TLS handshake, where
validity periods are confirmed. This paradoxical "catch-22" is
resolved by the Pledge maintaining a concept of the current "window"
of presumed time validity that is continually refined throughout the
bootstrapping process as follows:
o Initially the Pledge does not know the current time.
o During Pledge authentiation by the Registrar a realtime clock can
be used by the Registrar. This bullet expands on a closely
related issue regarding Pledge lifetimes. RFC5280 indicates that
long lived Pledge certifiates "SHOULD be assigned the
GeneralizedTime value of 99991231235959Z" [RFC7030] so the
Registrar MUST support such lifetimes and SHOULD support ignoring
Pledge lifetimes if they did not follow the RFC5280
recommendations.
o The Pledge authenticates the voucher presented to it. During this
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 3.4) now serves as a
valid time window. Any subsequent certificate validity periods
checked during RFC5280 path validation MUST occur within this
window.
o When accepting an enrollment certificate the validity period
within the new certificate is assumed to be valid by the Pledge.
The Pledge is now willing to use this credential for client
authentication.
D.1.1.6. Enrollment
As the final step of bootstrapping a Registrar helps to issue a
domain specific credential to the Pledge. For simplicity in this
document, a Registrar primarily facilitates issuing a credential by
acting as an RFC5280 Registration Authority for the Domain
Certification Authority.
Enrollment proceeds as described in [RFC7030]. Authentication of the
EST server is done using the Voucher rather than the methods defined
in EST.
[[RESOLVED: moved to protocol discussion]]Once the Voucher is
received, as specified in this document, the client has sufficient
information to leverage the existing communication channel with a
Registrar to continue an EST RFC7030 enrollment. Enrollment picks up
at RFC7030 section 4.1.1. bootstrapping where the Voucher provides
the "out-of-band" CA certificate fingerprint (in this case the full
CA certificate) such that the client can now complete the TLS server
authentication. At this point the client continues with EST
enrollment operations including "CA Certificates Request", "CSR
Attributes" and "Client Certificate Request" or "Server-Side Key
Generation".
[[RESOLVED: included into EST discussion]]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.
D.1.1.7. Being Managed
[[RESOLVED: by slight change to introduction text.]] Functionality to
provide generic "configuration" information is supported. The
parsing of this data and any subsequent use of the data, for example
communications with a Network Management System is out of scope but
is expected to occur after bootstrapping enrollment is complete.
This ensures that all communications with management systems which
can divulge local security information (e.g. network topology or raw
key material) is secured using the local credentials issued during
enrollment.
The Pledge uses bootstrapping to join only one domain. Management by
multiple domains is out-of-scope of bootstrapping. After the device
has successfully joined a domain and is being managed it is plausible
that the domain can insert credentials for other domains depending on
the device capabilities.
See Appendix D.1.5.
D.1.2. Behavior of a Join Proxy
The role of the Proxy is to facilitate communications. The Proxy
forwards packets between the Pledge and a Registrar that has been
configured on the Proxy.
[[UNRESOLVED: since proxy behavior is not visible we can limit
ourselves to discussion of what the protocol does to enable/faciliate
a theoretical proxy]]The Proxy does not terminate the TLS handshake.
[[UNRESOLVED: this is an anima architecture requirement to use BRSKI?
move to there?]] 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
Appendix D.1.1.1, the port number exposed by the proxy does not need
to be well known, or require an IANA allocation.
If the Proxy joins an Autonomic Control Plane
([I-D.ietf-anima-autonomic-control-plane]) it SHOULD use Autonomic
Control Plane secured GRASP ([I-D.ietf-anima-grasp]) to discovery the
Registrar address and port. As part of the discovery process, the
proxy mechanism (Circuit Proxy vs IPIP encapsulation) is agreed to
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
maximum variety of devices the chosen mechanism SHOULD use the
minimum amount of state on the proxy device. While many devices in
the ANIMA target space will be rather large routers, the proxy
function is likely to be implemented in the control plane CPU of such
a device, with available capabilities for the proxy function similar
to many class 2 IoT devices.
The document [I-D.richardson-anima-state-for-joinrouter] provides a
more extensive analysis of the alternative proxy methods.
D.1.2.1. CoAP connection to Registrar
[[RESOLVED:this section thus removed]]The CoAP mechanism was
depreciated.
D.1.2.2. HTTPS proxy connection to Registrar
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
connects the Pledge to a Registrar.
When the Proxy provides a circuit proxy to a Registrar the Registrar
MUST accept HTTPS connections.
When the Proxy provides a stateless IPIP encapsulation to a
Registrar, then the Registrar will have to perform IPIP
decapsulation, remembering the originating outer IPIP source address
in order to qualify the inner link-local address. This is a kind of
encapsulation and processing which is similar in many ways to how
mobile IP works.
Being able to connect a TCP (HTTP) or UDP (CoAP) socket to a link-
local address with an encapsulated IPIP header requires API
extensions beyond [RFC3542] for UDP use, and requires a form of
connection latching (see section 4.1 of [RFC5386] and all of
[RFC5660], except that a simple IPIP tunnel is used rather than an
IPsec tunnel).
D.1.3. Behavior of the Registrar
A Registrar listens for Pledges and determines if they can join the
domain. A Registrar obtains a Voucher from the MASA service and
delivers them to the Pledge as well as facilitating enrollment with
the domain PKI.
[[RESOLVED: moved to discovery discussion]] A Registrar is typically
configured manually. When the Registrar joins an Autonomic Control
Plane ([I-D.ietf-anima-autonomic-control-plane]) it MUST respond to
GRASP ([I-D.ietf-anima-grasp]) M_DISCOVERY message. See
Section 3.1.2
Registrar behavior is as follows:
Contacted by Pledge
+
|
+-------v----------+
| Entity | fail?
| Authentication +---------+
+-------+----------+ |
| |
+-------v----------+ |
| Entity | fail? |
| Authorization +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Claiming the | fail? |
| Entity +--------->
+-------+----------+ |
| |
+-------v----------+ |
| Log Verification | fail? |
| +--------->
+-------+----------+ |
| |
+-------v----------+ +----v-------+
| Forward | | |
| Voucher | | Reject |
| to the Pledge | | Device |
| | | |
+------------------+ +------------+
Figure 4
D.1.3.1. Pledge Authentication
The applicable authentication methods detailed in EST [RFC7030] are:
o [[RESOLVED:pointed out in protocol details]]the use of an X.509
IDevID credential during the TLS client authentication,
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).
In order to validate the X.509 IDevID credential a Registrar
maintains a database of vendor trust anchors (e.g. vendor root
certificates or keyIdentifiers for vendor root public keys). For
user interface purposes this database can be mapped to colloquial
vendor names. Registrars can be shipped with the trust anchors of a
significant number of third-party vendors within the target market.
D.1.3.2. Pledge Authorization
[[UNRESOLVED: this is referenced above as how the MASA does
authorization. That is incorrect]]
In a fully automated network all devices must be securely identified
and authorized to join the domain.
A Registrar accepts or declines a request to join the domain, based
on the authenticated identity presented. Automated acceptance
criteria include:
o allow any device of a specific type (as determined by the X.509
IDevID),
o allow any device from a specific vendor (as determined by the
X.509 IDevID),
o allow a specific device from a vendor (as determined by the X.509
IDevID) against a domain white list. (The mechanism for checking
a shared white list potentially used by multiple Registrars is out
of scope).
[[RESOLVED: this looks like good text to include in above]]To look
the Pledge up in a domain white list a consistent method for
extracting device identity from the X.509 certificate is required.
RFC6125 describes Domain-Based Application Service identity but here
we require Vendor Device-Based identity. The subject field's DN
encoding MUST include the "serialNumber" attribute with the device's
unique serial number. In the language of RFC6125 this provides for a
SERIALNUM-ID category of identifier that can be included in a
certificate and therefore that can also be used for matching
purposes. The SERIALNUM-ID whitelist is collated according to vendor
trust anchor since serial numbers are not globally unique.
[[RESOLVED: into log request]]The Registrar MUST use the vendor
provided MASA service to verify that the device's history log does
not include unexpected Registrars. If a device had previously
registered with another domain, a Registrar of that domain would show
in the log.
[[RESOLVED: est integration section used 'SHOULD']]The authorization
performed during BRSKI MAY be used for EST enrollment requests by
proceeding with EST enrollment using the authenticated and authorized
TLS connection. This minimizes the number of cryptographic and
protocol operations necessary to complete bootstrapping of the local
key infrastructure.
D.1.3.3. Claiming the New Entity
Claiming an entity establishes an audit log at the MASA server and
provides a Registrar with proof, in the form of the Voucher, that the
log entry has been inserted. As indicated in Appendix D.1.1.4 a
Pledge will only proceed with bootstrapping if a 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.
The Registrar obtains the MASA URI via static configuration or by
extracting it from the X.509 IDevID credential. See Section 2.2.
During initial bootstrapping the Pledge provides a nonce specific to
the particular bootstrapping attempt. [[RESOLVED: to resolve this I
updated many points where vouchers are referenced]]The Registrar
SHOULD include this nonce when claiming the Pledge from the MASA
service. Claims from an unauthenticated Registrar are only serviced
by the MASA resource if a nonce is provided.
The Registrar can claim a Pledge that is not online by forming the
request using the entities unique identifier and not including a
nonce in the claim request. Vouchers obtained in this way do not
have a lifetime and they provide a permanent method for the domain to
claim the device. Evidence of such a claim is provided in the audit
log entries available to any future Registrar. Such claims reduce
the ability for future domains to secure bootstrapping and therefore
the Registrar MUST be authenticated by the MASA service although no
requirement is implied that the MASA associates this authentication
with ownership.
An Ownership Voucher requires the vendor to definitively know that a
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
attempt is made to claim a device that has a an Ownership Voucher.
D.1.3.4. Log Verification
A Registrar requests the log information for the Pledge from the MASA
service. The log is verified to confirm that the following is true
to the satisfaction of a Registrar's configured policy:
o Any nonceless entries in the log are associated with domainIDs
recognized by the registrar.
o Any nonce'd entries are older than when the domain is known to
have physical possession of the Pledge or that the domainIDs are
recognized by the registrar.
If any of these criteria are unacceptable to a Registrar the entity
is rejected. [[RESOLVED: moved to main body]] A Registrar MAY be
configured to ignore the history of the device but it is RECOMMENDED
that this only be configured if hardware assisted NEA [RFC5209] is
supported.
[[RESOLVED: added to main text]]This document specifies a simple log
format as provided by the MASA service to the registar. This format
could be improved by distributed consensus technologies that
integrate vouchers with a technologies such as block-chain or hash
trees or the like. Doing so is out of the scope of this document but
are anticipated improvements for future work.
D.1.4. Behavior of the MASA Service
[[UNRESOLVED: primary value of keeping this discussion is to
distinguish between registrar and masa particularly wrt to the
protocol functions provided. perhaps add statements in each protocol
entry "provided by masa" etc?]]
The Manufacturer Authorized Signing Authority service is directly
provided by the manufacturer, or can be provided by a third party the
manufacturer authorizes. It is a cloud resource. The MASA service
provides the following functionalities to Registrars:
Issue Vouchers: In response to Registrar requests the MASA service
issues vouchers. Depending on the MASA policy the Registrar claim
of device ownership is either accepted or verified using out-of-
scope methods (that are expected to improve over time).
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.
Provide Logs: As a baseline implementation of the certified logging
mechanism the MASA is repsonsible for reporting logged
information. The current method involves trusting the MASA.
Other logging methods where the MASA is less trusted are expected
to be developed over time.
D.1.5. Leveraging the new key infrastructure / next steps
As the devices have a common trust anchor, device identity can be
securely established, making it possible to automatically deploy
services across the domain in a secure manner.
Examples of services:
o Device management.
o Routing authentication.
o Service discovery.
D.1.5.1. Network boundaries
When a device has joined the domain, it can validate the domain
membership of other devices. This makes it possible to create trust
boundaries where domain members have higher level of trusted than
external devices. Using the autonomic User Interface, specific
devices can be grouped into to sub domains and specific trust levels
can be implemented between those.
D.1.6. Interactions with Network Access Control
[[RESOLVED: via paragraph in 'scope of solution' discussion.]]
The assumption is that Network Access Control (NAC) completes using
the Pledge 's X.509 IDevID credentials and results in the device
having sufficient connectivity to discovery and communicate with the
proxy. Any additional connectivity or quarantine behavior by the NAC
infrastructure is out-of-scope. After the devices has completed
bootstrapping the mechanism to trigger NAC to re-authenticate the
device and provide updated network privileges is also out-of-scope.
This achieves the goal of a bootstrap architecture that can integrate
with NAC but does not require NAC within the network where it wasn't
previously required. Future optimizations can be achieved by
integrating the bootstrapping protocol directly into an initial EAP
exchange.
D.2. Domain Operator Activities
This section describes how an operator interacts with a domain that
supports the bootstrapping as described in this document.
D.2.1. Instantiating the Domain Certification Authority
This is a one time step by the domain administrator. This is an "off
the shelf" CA with the exception that it is designed to work as an
integrated part of the security solution. This precludes the use of
3rd party certification authority services that do not provide
support for delegation of certificate issuance decisions to a domain
managed Registration Authority.
D.2.2. Instantiating the Registrar
This is a one time step by the domain administrator. One or more
devices in the domain are configured take on a Registrar function.
A device can be configured to act as a Registrar or a device can
auto-select itself to take on this function, using a detection
mechanism to resolve potential conflicts and setup communication with
the Domain Certification Authority. Automated Registrar selection is
outside scope for this document.
D.2.3. Accepting New Entities
For each Pledge the Registrar is informed of the unique identifier
(e.g. serial number) along with the manufacturer's identifying
information (e.g. manufacturer root certificate). This can happen in
different ways:
1. Default acceptance: In the simplest case, the new device asserts
its unique identity to a Registrar. The registrar accepts all
devices without authorization checks. This mode does not provide
security against intruders and is not recommended.
2. Per device acceptance: The new device asserts its unique identity
to a Registrar. A non-technical human validates the identity,
for example by comparing the identity displayed by the registrar
(for example using a smartphone app) with the identity shown on
the packaging of the device. Acceptance may be triggered by a
click on a smartphone app "accept this device", or by other forms
of pairing. See also [I-D.behringer-homenet-trust-bootstrap] for
how the approach could work in a homenet.
3. Whitelist acceptance: In larger networks, neither of the previous
approaches is acceptable. Default acceptance is not secure, and
a manual per device methods do not scale. Here, the registrar is
provided a priori with a list of identifiers of devices that
belong to the network. This list can be extracted from an
inventory database, or sales records. If a device is detected
that is not on the list of known devices, it can still be
manually accepted using the per device acceptance methods.
4. Automated Whitelist: an automated process that builds the
necessary whitelists and inserts them into the larger network
domain infrastructure is plausible. Once set up, no human
intervention is required in this process. Defining the exact
mechanisms for this is out of scope although the registrar
authorization checks is identified as the logical integration
point of any future work in this area.
None of these approaches require the network to have permanent
Internet connectivity. Even when the Internet based MASA service is
used, it is possible to pre-fetch the required information from the
MASA a priori, for example at time of purchase such that devices can
enroll later. This supports use cases where the domain network may
be entirely isolated during device deployment.
Additional policy can be stored for future authorization decisions.
For example an expected deployment time window or that a certain
Proxy must be used.
D.2.4. Automatic Enrollment of Devices
The approach outlined in this document provides a secure zero-touch
method to enroll new devices without any pre-staged configuration.
New devices communicate with already enrolled devices of the domain,
which proxy between the new device and a Registrar. As a result of
this completely automatic operation, all devices obtain a domain
based certificate.
D.2.5. Secure Network Operations
The certificate installed in the previous step can be used for all
subsequent operations. For example, to determine the boundaries of
the domain: If a neighbor has a certificate from the same trust
anchor it can be assumed "inside" the same organization; if not, as
outside. See also Appendix D.1.5.1. The certificate can also be
used to securely establish a connection between devices and central
control functions. Also autonomic transactions can use the domain
certificates to authenticate and/or encrypt direct interactions
between devices. The usage of the domain certificates is outside
scope for this document.
Authors' Addresses 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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