Delegated Authority for Bootstrap Voucher Artifacts
draft-richardson-anima-voucher-delegation-00
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|---|---|---|---|
| Author | Michael Richardson | ||
| Last updated | 2020-01-06 | ||
| Replaced by | draft-ietf-anima-voucher-delegation | ||
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draft-richardson-anima-voucher-delegation-00
anima Working Group M. Richardson
Internet-Draft Sandelman Software Works
Intended status: Standards Track January 06, 2020
Expires: July 9, 2020
Delegated Authority for Bootstrap Voucher Artifacts
draft-richardson-anima-voucher-delegation-00
Abstract
This document describes an extension of the RFC8366 Voucher Artifact
in order to support delegation of signing authority. The initial
voucher pins a public identity, and that public indentity can then
issue additional vouchers. This chain of authorization can support
permission-less resale of devices, as well as guarding against
business failure of the BRSKI [I-D.ietf-anima-bootstrapping-keyinfra]
Manufacturer Authorized Signing Authority (MASA).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 9, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements for the delegation . . . . . . . . . . . . . 3
1.1.1. Disconnected or Offline MASA . . . . . . . . . . . . 3
1.1.2. Resale of devices . . . . . . . . . . . . . . . . . . 3
1.1.3. Crypto-agility for Registrar . . . . . . . . . . . . 3
1.1.4. Transparent Assemblers/Value-Added-Resellers . . . . 4
1.2. Overview of proposed solution . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Delegated Voucher artifact . . . . . . . . . . . . . . . . . 5
3.1. YANG module . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Bundling of the vouchers . . . . . . . . . . . . . . . . 8
3.3. Delegation of multiple devices . . . . . . . . . . . . . 8
4. Enhanced Pledge behaviour . . . . . . . . . . . . . . . . . . 8
5. Changes to Registrar behaviour . . . . . . . . . . . . . . . 9
5.1. Discoverying the most recent Delegated Authority to use . 9
6. Applying the delegated voucher to requirements . . . . . . . 10
6.1. applicability one . . . . . . . . . . . . . . . . . . . . 10
6.2. applicability two . . . . . . . . . . . . . . . . . . . . 10
7. Constraints on pinning the Delegated Authority . . . . . . . 10
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9.1. YANG Module Security Considerations . . . . . . . . . . . 11
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
10.1. The IETF XML Registry . . . . . . . . . . . . . . . . . 11
10.2. YANG Module Names Registry . . . . . . . . . . . . . . . 11
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
12. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 12
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
13.1. Normative References . . . . . . . . . . . . . . . . . . 12
13.2. Informative References . . . . . . . . . . . . . . . . . 12
Appendix A. Extra references . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
The [RFC8366] voucher artifact provides a proof from a manufacturer's
authorizing signing authority (MASA) of the intended owner of a
device. This is used by an onboarding Pledge device in BRSKI
([I-D.ietf-anima-bootstrapping-keyinfra],
[I-D.ietf-anima-constrained-voucher]), and SZTP ([RFC8572]).
There are a number of criticisms of the MASA concept. They include:
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o the MASA must be reachable to the Registar during the onboarding
process.
o while the use of a nonceless voucher (see {{RFC8366} section 4)
can permit the MASA to be offline, it still requires the public
key/certificate of the Registrar to be known at issuing time
o the MASA must also approve all transfers of ownership, impacting
the rights of the initial seller to transfer ownership as they see
fit.
o if the Registrar has any nonceless vouchers, then it can not
change it's public key, nor can it change which certification
authority it uses
o it is not possible for a MASA to pin ownership to a Registrar by
Certification Authority plus DN
o the creator of an assembly of parts/components can speak for the
entire assembly of parts in a transparent way
1.1. Requirements for the delegation
This voucher artifact satisfies the following requirements:
1.1.1. Disconnected or Offline MASA
A Registrar wishes to onboard devices while not being connected to
the Internet.
1.1.2. Resale of devices
An owner of a device wishes to resale devices which have previously
been onboarded to a third party without specific authorization from
the manufacturer.
1.1.3. Crypto-agility for Registrar
The owner/manager of a registrar wishes to be able to replace its
domain registration key. Replacing the registration key would
invalidate any previously acquired (nonceless) vouchers. Any devices
which have not been onboarded, or which need to be factory reset,
would not trust a replacement key.
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1.1.4. Transparent Assemblers/Value-Added-Resellers
An assembly may consist of a number of parts which are onboarded to a
local controller during the manufacturing process. Subsequent to
this, the entire assembly will be shipped to a customer who wishes to
onboard all the components. The sub-components of the assembly needs
to communicate with other sub-components, and so all the parts need
to transparently onboarded. (This is contrasted with an assembly
where the controller acts as a security gateway. Such a gateway
might be a single point of failure)
Assemblies may nest quite deeply.
1.2. Overview of proposed solution
The MASA will issue a voucher that delegates it's signing authority
for one or more devices to a specific Registrar. This is called a
"delegation voucher".
This Registrar can then operate as an authorized signing authority
for the manufacturer, and can subsequently issue additional vouchers
binding the pledge to new Registrars.
This delegation can potentially be repeated multiple times to enable
second, third, or n-th level of resale.
The delegation voucher may be stored by the pledge for storage, to be
included by the pledge in subsequent bootstrap operations. The
inclusion of the delegation permits next Registrars with heuristics
that permit it to find the delegated authorized signing service
(DASA).
The delegation voucher pins the identity of the delegated authority
using a variety of different mechanisms which are covered in
Section 7.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Delegated Authorized Signing Authority : the Delegated Authorized
Signing Authority (DASA) is a service that can generate vouchers
for one or more pledges to provide bootstrap authority separate
from the manufacturer.
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Delegation Voucher: a Delegation Voucher is an [RFC8366] format
voucher that has additional fields to provide detailed the entity
to which authority has been delegated.
Intermediate Voucher: a voucher that is not the final voucher
linking a pledge to its owner.
End Voucher: a voucher that is the final voucher linking a pledge to
its owner.
3. Delegated Voucher artifact
The following tree diagram shows the extensions to the [RFC8366]
voucher.
There are a few new fields: pinned-delegation-certificate-authority,
pinned-delegation-name, delegation-count. In addition, the serial-
number field is no longer a plain leaf, but can also be an array.
module: ietf-delegated-voucher
grouping voucher-delegated-grouping
+-- voucher
+-- created-on yang:date-and-time
+-- expires-on? yang:date-and-time
+-- assertion enumeration
+-- serial-number string
+-- idevid-issuer? binary
+-- pinned-domain-cert? binary
+-- domain-cert-revocation-checks? boolean
+-- nonce? binary
+-- last-renewal-date? yang:date-and-time
+-- pinned-certificate-authority? binary
+-- pinned-certificate-name? binary
+-- delegation-voucher? binary
+-- intermediate-identities? binary
+-- delegation-countdown? int16
3.1. YANG module
This module uses the grouping that was created in [RFC8366] to extend
the definition.
<CODE BEGINS> file "ietf-delegated-voucher@2020-01-06.yang"
module ietf-delegated-voucher {
yang-version 1.1;
namespace
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"urn:ietf:params:xml:ns:yang:ietf-delegated-voucher";
prefix "delegated";
import ietf-restconf {
prefix rc;
description
"This import statement is only present to access
the yang-data extension defined in RFC 8040.";
reference "RFC 8040: RESTCONF Protocol";
}
// maybe should import from constrained-voucher instead!
import ietf-voucher {
prefix "v";
}
organization
"IETF ANIMA Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/anima/>
WG List: <mailto:anima@ietf.org>
Author: Michael Richardson
<mailto:mcr+ietf@sandelman.ca>";
description
"This module extends the RFC8366 voucher format to provide
a mechanism by which the authority to issue additional vouchers
may be delegated to another entity
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
and 'OPTIONAL' in the module text are to be interpreted as
described in BCP 14 RFC 2119, and RFC8174.";
revision "2020-01-06" {
description
"Initial version";
reference
"RFC XXXX: Voucher Profile for Delegation Vouchers";
}
rc:yang-data voucher-delegated-artifact {
// YANG data template for a voucher.
uses voucher-delegated-grouping;
}
// Grouping defined for future usage
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grouping voucher-delegated-grouping {
description
"Grouping to allow reuse/extensions in future work.";
uses v:voucher-artifact-grouping {
refine voucher/pinned-domain-cert {
mandatory false;
}
augment "voucher" {
description "Base the delegated voucher
upon the regular one";
leaf pinned-certificate-authority {
type binary;
description
"An subject-public-key-info for a public key of the
certificate authority that is to be trusted to issue
a voucher to the Registrar.
This is not used by end-vouchers.";
}
leaf pinned-certificate-name {
type binary;
description
"A string for the rfc822Name SubjectAltName contents
which will be trusted to issue vouchers.
This is not used by end-vouchers.";
}
leaf delegation-voucher {
type binary;
description
"The intermediate voucher that delegates
authority to the entity that signs this voucher
is to be included here.";
}
leaf intermediate-identities {
type binary;
description
"A set of identities that will be needed to
validate the chain of vouchers. MAY BE REDUNDANT";
}
leaf delegation-countdown {
type int16;
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description
"Number of delegations still available. If zero
or omitted, then this is a terminal voucher and
may not be further delegated";
}
}
}
}
}
<CODE ENDS>
3.2. Bundling of the vouchers
The [I-D.ietf-anima-bootstrapping-keyinfra] defines a mechanism to
return a single voucher to the pledge.
This protocol requires a number of additional items to be returned to
the pledge for evaluation: the series of Intermediate Vouchers that
leads to the DASA, and the public keys (often as certificates) of the
Registrars on the Delegation Path that leads to each Authority.
3.3. Delegation of multiple devices
A MASA MAY delegate multiple devices to the same Registrar by putting
an array of items in the "serial-number" attributes. (XXX-how to
describe this in the YANG)
4. Enhanced Pledge behaviour
The use of a delegated voucher requires changes to how the pledge
evaluates the voucher that is returned to by the Registrar.
There are no significant changes to the voucher-request that is made.
The pledge continues to pin the identity of the Registrar to which it
is connected, providing a nonce to establish freshness.
A pledge which has previously stored a delegation voucher and
delegated authority, SHOULD include it in its voucher request. This
will be in the form of a certificate provided by the "previous"
owner. This allows the Registrar to discover the previous authority
for the pledge. As the pledge has no idea if it connecting to an
entity that it previously has connected to, it needs to include this
certificate anyway.
The pledge receives a voucher from the Registrar. This voucher is
called the zero voucher. It will observe that the voucher is not
signed with its built-in manufacturer trust anchor and it can not
verify it.
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The pledge will examine the voucher to look for the "delegation-
voucher" and the intermediate-identities attributes within the
voucher. A certificate from the set of intermediate-identities is
expected to validate the signature on this zeroth end-entity voucher.
(XXX- This attribute can be replaced by the CMS certificate chain)
The contained delegation-voucher object is to be interpreted as an
(intermediate) voucher. This first voucher is called the first
voucher, or "voucher[1]". Generically, for voucher[i], the voucher
found in the delegation-voucher is called voucher[i+1].
If voucher[i] can be validated by a built-in trust anchor, then the
process is done. If not, then voucher[i] is examined in a recursive
process until no there are no further embedded vouchers. The last
voucher[n] is expected to be validated by a built-in manufacturer
trust anchor.
Once the top (n-th) voucher is found, then the pinned-certificate-
authority is added to the working set of trust anchors. The pinned-
certificate-name attribute is used along with the trust anchor to
validate the certificate chain provided with the n-1th voucher. This
is repeated (unwinding the recursive processing) until the zeroth
voucher has been validated.
5. Changes to Registrar behaviour
TBD
5.1. Discoverying the most recent Delegated Authority to use
The pledge continues to use its manufacturer issued IDevID when
performing BRSKI-style onboarding. The IDevID contains an extension,
the MASA URL (see [I-D.ietf-anima-bootstrapping-keyinfra] section
2.3.2). The IDevID certificate is not expected to be updated when
the device is resold, nor may it be practical for an intermediate
owner to be able to replace the IDevID with their own. (Some devices
may support having an intermediate owner replace the IDevID, in which
case this section does not apply)
The Registrar needs to be informed that it should not contact a MASA
using the URL in the IDevID, but rather to contact the previous
owner's DASA.
This can be accomplished by local override, as described in
[I-D.ietf-anima-bootstrapping-keyinfra] section 5.4:
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Registrars MAY include a mechanism to override
the MASA URL on a manufacturer-by-manufacturer basis, and within that
override it is appropriate to provide alternate anchors. This will
typically used by some vendors to establish explicit (or private)
trust anchors for validating their MASA that is part of a sales
channel integration.
The above override needs to be established on a per-device basis. It
requires per-device configuration which is very much non-autonomic.
There are two other alternatives:
1. The Manufacturer could be aware of any delegation-vouchers that
it has issued for a particular device, and when contacted by the
Registrar, it could redirect the Registrar to the DASA.
2. The Pledge could provide a signed statement from the manufacturer
providing the Registrar with a pointer to the DASA.
Option 1 requires that the Registrar still contact the MASA,
violating most of the goals from Section 1.1.
Option 2 requires a signed artifact, and conveniently, the delegation
voucher is exactly the document needed. The most difficult problem
is that the Pledge needs to (a) store one or more delegation vouchers
in a non-volatile storage that survives factory reset operations, (b)
attach these documents to the pledge's voucher-request.
The extension to the [I-D.ietf-anima-bootstrapping-keyinfra] voucher-
request described below provides for a contained for these delegation
vouchers.
6. Applying the delegated voucher to requirements
6.1. applicability one
TBD
6.2. applicability two
TBD
7. Constraints on pinning the Delegated Authority
TBD
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8. Privacy Considerations
YYY
9. Security Considerations
9.1. YANG Module Security Considerations
As described in the Security Considerations section of [RFC8366]
(section 7.4), the YANG module specified in this document defines the
schema for data that is subsequently encapsulated by a CMS signed-
data content type, as described in Section 5 of [RFC5652]. As such,
all of the YANG modeled data is protected from modification.
The use of YANG to define data structures, via the 'yang-data'
statement, is relatively new and distinct from the traditional use of
YANG to define an API accessed by network management protocols such
as NETCONF [RFC6241] and RESTCONF [RFC8040]. For this reason, these
guidelines do not follow template described by Section 3.7 of
[RFC8407].
10. IANA Considerations
This document requires the following IANA actions:
10.1. The IETF XML Registry
This document registers a URI in the "IETF XML Registry" [RFC3688].
IANA is asked to register the following:
URI: urn:ietf:params:xml:ns:yang:ietf-delegated-voucher
Registrant Contact: The ANIMA WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
10.2. YANG Module Names Registry
This document registers a YANG module in the "YANG Module Names"
registry [RFC6020]. IANA is asked to register the following:
name: ietf-delegated-voucher
namespace: urn:ietf:params:xml:ns:yang:ietf-delegated-voucher
prefix: NONE
reference: THIS DOCUMENT
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11. Acknowledgements
Hello.
12. Changelog
13. References
13.1. Normative References
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-34 (work in progress), January 2020.
[I-D.ietf-anima-constrained-voucher]
Richardson, M., Stok, P., and P. Kampanakis, "Constrained
Voucher Artifacts for Bootstrapping Protocols", draft-
ietf-anima-constrained-voucher-05 (work in progress), July
2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8366] Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
"A Voucher Artifact for Bootstrapping Protocols",
RFC 8366, DOI 10.17487/RFC8366, May 2018,
<https://www.rfc-editor.org/info/rfc8366>.
13.2. Informative References
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/rfc5652>.
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[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/info/rfc8407>.
[RFC8572] Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero
Touch Provisioning (SZTP)", RFC 8572,
DOI 10.17487/RFC8572, April 2019,
<https://www.rfc-editor.org/info/rfc8572>.
Appendix A. Extra references
RFC Editor, please remove this section. This section lists
references in the YANG. [RFC8174], [RFC8040].
Author's Address
Michael Richardson
Sandelman Software Works
Email: mcr+ietf@sandelman.ca
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