Internet DRAFT - draft-ietf-anima-rfc8366bis
draft-ietf-anima-rfc8366bis
ANIMA Working Group K. Watsen
Internet-Draft Watsen Networks
Intended status: Standards Track M. Richardson
Expires: 5 September 2024 Sandelman Software
M. Pritikin
Cisco Systems
T. Eckert
Futurewei Technologies Inc.
Q. Ma
Huawei
4 March 2024
A Voucher Artifact for Bootstrapping Protocols
draft-ietf-anima-rfc8366bis-11
Abstract
This document defines a strategy to securely assign a pledge to an
owner using an artifact signed, directly or indirectly, by the
pledge's manufacturer. This artifact is known as a "voucher".
This document defines an artifact format as a YANG-defined JSON or
CBOR document that has been signed using a variety of cryptographic
systems.
The voucher artifact is normally generated by the pledge's
manufacturer (i.e., the Manufacturer Authorized Signing Authority
(MASA)).
This document updates RFC8366, merging a number of extensions into
the YANG. The RFC8995 voucher request is also merged into this
document.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-anima-rfc8366bis/.
Discussion of this document takes place on the anima Working Group
mailing list (mailto:anima@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/anima/. Subscribe at
https://www.ietf.org/mailman/listinfo/anima/.
Source for this draft and an issue tracker can be found at
https://github.com/anima-wg/voucher.
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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 5 September 2024.
Copyright Notice
Copyright (c) 2024 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 Revised BSD License text as
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Requirements Language . . . . . . . . . . . . . . . . . . . . 6
4. Survey of Voucher Types . . . . . . . . . . . . . . . . . . . 6
5. Changes since RFC8366 . . . . . . . . . . . . . . . . . . . . 8
6. Signature mechanisms . . . . . . . . . . . . . . . . . . . . 9
6.1. CMS Format Voucher Artifact . . . . . . . . . . . . . . . 10
7. Voucher Artifact . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 11
7.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 12
7.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 12
7.4. ietf-voucher SID values . . . . . . . . . . . . . . . . . 19
8. Voucher Request Artifact . . . . . . . . . . . . . . . . . . 20
8.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 20
8.2. "ietf-voucher-request" Module . . . . . . . . . . . . . . 21
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8.3. ietf-voucher-request SID values . . . . . . . . . . . . . 27
9. Design Considerations . . . . . . . . . . . . . . . . . . . . 27
9.1. Renewals Instead of Revocations . . . . . . . . . . . . . 27
9.2. Voucher Per Pledge . . . . . . . . . . . . . . . . . . . 28
10. Security Considerations . . . . . . . . . . . . . . . . . . . 28
10.1. Clock Sensitivity . . . . . . . . . . . . . . . . . . . 29
10.2. Protect Voucher PKI in HSM . . . . . . . . . . . . . . . 29
10.3. Test Domain Certificate Validity When Signing . . . . . 29
10.4. YANG Module Security Considerations . . . . . . . . . . 29
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
11.1. The IETF XML Registry . . . . . . . . . . . . . . . . . 30
11.2. The YANG Module Names Registry . . . . . . . . . . . . . 30
11.3. The Media Types Registry . . . . . . . . . . . . . . . . 31
11.4. The SMI Security for S/MIME CMS Content Type Registry . 31
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
12.1. Normative References . . . . . . . . . . . . . . . . . . 31
12.2. Informative References . . . . . . . . . . . . . . . . . 33
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
1. Introduction
This document defines a strategy to securely assign a candidate
device (pledge) to an owner using an artifact signed, directly or
indirectly, by the pledge's manufacturer, i.e., the Manufacturer
Authorized Signing Authority (MASA). This artifact is known as the
"voucher".
The voucher artifact is a JSON [RFC8259] document that conforms with
a data model described by YANG [RFC7950]. It may also be serialized
to CBOR [CBOR]. It is encoded using the rules defined in [RFC7951],
and is signed using (by default) a CMS structure [RFC5652].
The primary purpose of a voucher is to securely convey a certificate,
the "pinned-domain-cert" (and constrained variations), that a pledge
can use to authenticate subsequent interactions. A voucher may be
useful in several contexts, but the driving motivation herein is to
support secure onboarding mechanisms. Assigning ownership is
important to device onboarding mechanisms so that the pledge can
authenticate the network that is trying to take control of it.
The lifetimes of vouchers may vary. In some onboarding protocols,
the vouchers may include a nonce restricting them to a single use,
whereas the vouchers in other onboarding protocols may have an
indicated lifetime. In order to support long lifetimes, this
document recommends using short lifetimes with programmatic renewal,
see Section 9.1.
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This document only defines the voucher artifact, leaving it to other
documents to describe specialized protocols for accessing it. Some
onboarding protocols using the voucher artifact defined in this
document include: [ZERO-TOUCH], [SECUREJOIN], and [BRSKI].
2. Terminology
This document uses the following terms:
(Voucher) Artifact: Used throughout to represent the voucher as
instantiated in the form of a signed structure.
Bootstrapping: The process where a pledge component obtains
cryptographic key material to identify and trust future
interactions within a specific domain network. Based on imprinted
key material provided during manufacturing process (see
imprinting).
Domain: The set of entities or infrastructure under common
administrative control. The goal of the onboarding protocol is to
enable a pledge component to join a domain and obtain domain
specific security credentials.
Imprint: The process where a device obtains the cryptographic key
material to identify and trust future interactions generally as
part of the manufacturing. This term is taken from Konrad
Lorenz's work in biology with new ducklings: "during a critical
period, the duckling would assume that anything that looks like a
mother duck is in fact their mother" [Stajano99theresurrecting].
An equivalent for a device is to obtain the fingerprint of the
manufacturer's root certification authority (root ca) certificate.
A device that imprints on an attacker suffers a similar fate to a
duckling that imprints on a hungry wolf. Imprinting is a term
from psychology and ethology, as described in [imprinting].
Join Registrar (and Coordinator): A representative of the domain
that is configured, perhaps autonomically, to decide whether a new
device is allowed to join the domain. The administrator of the
domain interfaces with a join registrar (and Coordinator) to
control this process. Typically, a join registrar is "inside" its
domain. For simplicity, this document often refers to this as
just "registrar".
MASA (Manufacturer Authorized Signing Authority): The entity that,
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for the purpose of this document, issues and signs the vouchers
for a manufacturer's pledges. In some onboarding protocols, the
MASA may have an Internet presence and be integral to the
onboarding process, whereas in other protocols the MASA may be an
offline service that has no active role in the onboarding process.
malicious registrar: An on-path active attacker that presents itself
as a legitimate registrar, but which is in fact under the control
of an attacker.
Onboarding: Onboarding describes the process to provide necessary
operational data to pledge components and completes the process to
bring a device into an operational state. This data may be
configuration data, or also application specific cryptographic key
material (application speciifc security credentials).
Owner: The entity that controls the private key of the "pinned-
domain-cert" certificate conveyed by the voucher.
Pledge: The prospective component attempting to find and securely
join a domain. When shipped or in factory reset mode, it only
trusts authorized representatives of the manufacturer.
Registrar: See join registrar.
TOFU (Trust on First Use): Where a pledge component makes no
security decisions but rather simply trusts the first domain
entity it is contacted by. Used similarly to [RFC7435]. This is
also known as the "resurrecting duckling" model.
Voucher: A short form for Voucher Artifact. It refers to the signed
statement from the MASA service that indicates to a pledge the
cryptographic identity of the domain it should trust. When
clarity is needed, it may be preceeded by the type of the
signature, such as CMS, JWS or COSE.
Voucher Data: The raw (serialized) representation of the YANG
without any enclosing signature. Current formats include JSON and
CBOR.
Voucher Request: A signed artifact sent from the Pledge to the
Registrar, or from the Registrar to the MASA for Voucher
acquisition.
Pledge Voucher Request (PVR): A signed artifact sent from the Pledge
to the Registrar. It is a special form of Voucher Request.
Registrar Voucher Request (RVR): A signed artifact sent from the
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Registrar to the MASA. It is a special form of Voucher Request.
3. Requirements Language
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.
4. Survey of Voucher Types
A voucher is a cryptographically protected statement to the pledge
device authorizing a zero-touch "imprint" on the join registrar of
the domain. The specific information a voucher provides is
influenced by the onboarding use case.
The voucher can impart the following information to the join
registrar and pledge:
Assertion Basis: Indicates the method that protects the imprint
(this is distinct from the voucher signature that protects the
voucher itself). This might include manufacturer-asserted
ownership verification, assured logging operations, or reliance on
pledge endpoint behavior such as secure root of trust of
measurement. The join registrar might use this information. Only
some methods are normatively defined in this document. Other
methods are left for future work.
Authentication of Join Registrar: Indicates how the pledge can
authenticate the join registrar. This document defines a
mechanism to pin the domain certificate, or a raw public key.
Pinning a symmetric key, or "CN-ID" or "DNS-ID" information (as
defined in [RFC6125]) is left for future work.
Anti-Replay Protections: Time- or nonce-based information to
constrain the voucher to time periods or bootstrap attempts.
A number of onboarding scenarios can be met using differing
combinations of this information. All scenarios address the primary
threat of an on-path active attacker (or MiTM) impersonating the
registrar. This would gain control over the pledge device. The
following combinations are "types" of vouchers:
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+============+=========+========+=========+========+========+=====+
| |Assertion| |Registrar| |Validity| |
| | | | ID| | | |
+============+=========+========+=========+========+========+=====+
|Voucher Type| Logged|Verified| Trust|CN-ID or| RTC|Nonce|
| | | | Anchor| DNS-ID| | |
+------------+---------+--------+---------+--------+--------+-----+
|Audit | X| | X| | | X|
+------------+---------+--------+---------+--------+--------+-----+
|Nonceless | X| | X| | X| |
|Audit | | | | | | |
+------------+---------+--------+---------+--------+--------+-----+
|Owner Audit | X| X| X| | X| X|
+------------+---------+--------+---------+--------+--------+-----+
|Owner ID | | X| X| X| X| |
+------------+---------+--------+---------+--------+--------+-----+
|Bearer out- | X| | wildcard|wildcard|optional| opt|
|of-scope | | | | | | |
+------------+---------+--------+---------+--------+--------+-----+
Table 1
NOTE: All voucher types include a 'pledge ID serial-number' (not
shown here for space reasons).
Audit Voucher: An Audit Voucher is named after the logging assertion
mechanisms that the registrar then "audits" to enforce local
policy. The registrar mitigates a malicious registrar by auditing
that an unknown malicious registrar does not appear in the log
entries. This does not directly prevent a malicious registrar but
provides a response mechanism that ensures the MiTM is
unsuccessful. The advantage is that actual ownership knowledge is
not required on the MASA service.
Nonceless Audit Voucher: An Audit Voucher without a validity period
statement. Fundamentally, it is the same as an Audit Voucher
except that it can be issued in advance to support network
partitions or to provide a permanent voucher for remote
deployments.
Ownership Audit Voucher: An Audit Voucher where the MASA service has
verified the registrar as the authorized owner. The MASA service
mitigates a MiTM registrar by refusing to generate Audit Vouchers
for unauthorized registrars. The registrar uses audit techniques
to supplement the MASA. This provides an ideal sharing of policy
decisions and enforcement between the vendor and the owner.
Ownership ID Voucher: Named after inclusion of the pledge's CN-ID or
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DNS-ID within the voucher. The MASA service mitigates a MiTM
registrar by identifying the specific registrar (via WebPKI)
authorized to own the pledge.
Bearer Voucher: A Bearer Voucher is named after the inclusion of a
registrar ID wildcard. Because the registrar identity is not
indicated, this voucher type must be treated as a secret and
protected from exposure as any 'bearer' of the voucher can claim
the pledge device. Publishing a nonceless bearer voucher
effectively turns the specified pledge into a "TOFU" device with
minimal mitigation against MiTM registrars. Bearer vouchers are
out of scope.
5. Changes since RFC8366
[RFC8366] was published in 2018 during the development of [BRSKI],
[ZERO-TOUCH] and other work-in-progress efforts. Since then the
industry has matured significantly, and the in-the-field activity
which this document supports has become known as _onboarding_ rather
than _bootstrapping_.
The focus of [BRSKI] was onboarding of ISP and Enterprise owned wired
routing and switching equipment, with IoT devices being a less
important aspect. [ZERO-TOUCH] has focused upon onboarding of CPE
equipment like cable modems and other larger IoT devices, again with
smaller IoT devices being of less import.
Since [BRSKI] was published there is now a mature effort to do
application-level onboarding of constrained IoT devices defined by
The Thread and Fairhair (now OCF) consortia. The [cBRSKI] document
has defined a version of [BRSKI] that is useable over constrained
802.15.4 networks using CoAP and DTLS, while
[I-D.selander-ace-ake-authz] provides for using CoAP and EDHOC on
even more constrained devices with very constrained networks.
[PRM] has created a new methodology for onboarding that does not
depend upon a synchronous connection between the Pledge and the
Registrar. This mechanism uses a mobile Registrar Agent that works
to collect and transfer signed artifacts via physical travel from one
network to another.
Both [cBRSKI] and [PRM] require extensions to the Voucher Request and
the resulting Voucher. The new attribtes are required to carry the
additional attributes and describe the extended semantics. In
addition [cBRSKI] uses the serialization mechanism described in
[YANGCBOR] to produce significantly more compact artifacts.
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When the process to define [cBRSKI] and [PRM] was started, there was
a belief that the appropriate process was to use the [RFC8040]
_augment_ mechanism to further extend both the voucher request
[BRSKI] and voucher [RFC8366] artifacts. However, [PRM] needs to
extend an enumerated type with additional values and _augment_ can
not do this, so that was initially the impetus for this document.
An attempt was then made to determine what would happen if one wanted
to have a constrained version of the [PRM] voucher artifact. The
result was invalid YANG, with multiple definitions of the core
attributes from the [RFC8366] voucher artifact. After some
discussion, it was determined that the _augment_ mechanism did not
work, nor did it work better when [RFC8040] yang-data was replaced
with the [RFC8791] structure mechanisms.
After significant discussion the decision was made to simply roll all
of the needed extensions up into this document as "RFC8366bis".
This document therefore represents a merge of YANG definitions from
[RFC8366], the voucher-request from [BRSKI], and then extensions to
each of these from [cBRSKI], [CLOUD] and [PRM]. There are some
difficulties with this approach: this document does not attempt to
establish rigorous semantic definitions for how some attributes are
to be used, referring normatively instead to the other relevant
documents.
6. Signature mechanisms
Three signature systems have been defined for vouchers and voucher-
requests.
[I-D.ietf-anima-constrained-voucher] defines a mechanism that uses
COSE RFC9052, with the voucher data encoded using
[I-D.ietf-core-sid]. However, as the SID processe requires up-to-
date YANG, the SID values for this mechanism are presented in this
document.
[I-D.ietf-anima-jws-voucher] defines a mechanism that uses JSON
[RFC8259] and [JWS].
The CMS mechanism first defined in [RFC8366] continues to be defined
here.
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6.1. CMS Format Voucher Artifact
The IETF evolution of PKCS#7 is CMS [RFC5652]. A CMS-signed voucher,
the default type, contains a ContentInfo structure with the voucher
content. An eContentType of 40 indicates that the content is a JSON-
encoded voucher.
The signing structure is a CMS SignedData structure, as specified by
Section 5.1 of [RFC5652], encoded using ASN.1 Distinguished Encoding
Rules (DER), as specified in ITU-T X.690 [ITU-T.X690.2015].
To facilitate interoperability, Section 11.3 in this document
registers the media type "application/voucher-cms+json" and the
filename extension ".vcj".
The CMS structure MUST contain a 'signerInfo' structure, as described
in Section 5.1 of [RFC5652], containing the signature generated over
the content using a private key trusted by the recipient. Normally,
the recipient is the pledge and the signer is the MASA. In the
Voucher Request, the signer is the pledge, or the Registrar. Within
this document, the signer is assumed to be the MASA.
Note that Section 5.1 of [RFC5652] includes a discussion about how to
validate a CMS object, which is really a PKCS7 object (cmsVersion=1).
Intermediate systems (such the Bootstrapping Remote Secure Key
Infrastructures [BRSKI] registrar) that might need to evaluate the
voucher in flight MUST be prepared for such an older format. No
signaling is necessary, as the manufacturer knows the capabilities of
the pledge and will use an appropriate format voucher for each
pledge.
The CMS structure SHOULD also contain all of the certificates leading
up to and including the signer's trust anchor certificate known to
the recipient. The inclusion of the trust anchor is unusual in many
applications, but third parties cannot accurately audit the
transaction without it.
The CMS structure MAY also contain revocation objects for any
intermediate certificate authorities (CAs) between the voucher issuer
and the trust anchor known to the recipient. However, the use of
CRLs and other validity mechanisms is discouraged, as the pledge is
unlikely to be able to perform online checks and is unlikely to have
a trusted clock source. As described below, the use of short-lived
vouchers and/or a pledge-provided nonce provides a freshness
guarantee.
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7. Voucher Artifact
The voucher's primary purpose is to securely assign a pledge to an
owner. The voucher informs the pledge which entity it should
consider to be its owner.
This document defines a voucher that is a JSON-encoded or CBOR-
encoded instance of the YANG module defined in Section 7.3.
This format is described here as a practical basis for some uses
(such as in NETCONF), but more to clearly indicate what vouchers look
like in practice. This description also serves to validate the YANG
data model.
[RFC8366] defined a media type and a filename extension for the CMS-
encoded JSON type. Which type of voucher is expected is signaled
(where possible) in the form of a MIME Content-Type, an HTTP Accept:
header, or more mundane methods like use of a filename extension when
a voucher is transferred on a USB key.
7.1. Tree Diagram
The following tree diagram illustrates a high-level view of a voucher
document. The notation used in this diagram is described in
[RFC8340]. Each node in the diagram is fully described by the YANG
module in Section 7.3. Please review the YANG module for a detailed
description of the voucher format.
module: ietf-voucher
structure voucher:
+-- 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
+-- pinned-domain-pubk? binary
+-- pinned-domain-pubk-sha256? binary
+-- last-renewal-date? yang:date-and-time
+-- est-domain? ietf:uri
+-- additional-configuration? ietf:uri
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7.2. Examples
This section provides voucher examples for illustration purposes.
These examples conform to the encoding rules defined in [RFC8259].
The following example illustrates an ephemeral voucher (uses a
nonce). The MASA generated this voucher using the 'logged' assertion
type, knowing that it would be suitable for the pledge making the
request.
{
"ietf-voucher:voucher": {
"created-on": "2016-10-07T19:31:42Z",
"assertion": "logged",
"serial-number": "JADA123456789",
"idevid-issuer": "base64encodedvalue==",
"pinned-domain-cert": "base64encodedvalue==",
"nonce": "base64encodedvalue=="
}
}
The following example illustrates a non-ephemeral voucher (no nonce).
While the voucher itself expires after two weeks, it presumably can
be renewed for up to a year. The MASA generated this voucher using
the 'verified' assertion type, which should satisfy all pledges.
{
"ietf-voucher:voucher": {
"created-on": "2016-10-07T19:31:42Z",
"expires-on": "2016-10-21T19:31:42Z",
"assertion": "verified",
"serial-number": "JADA123456789",
"idevid-issuer": "base64encodedvalue==",
"pinned-domain-cert": "base64encodedvalue==",
"domain-cert-revocation-checks": true,
"last-renewal-date": "2017-10-07T19:31:42Z"
}
}
7.3. YANG Module
<CODE BEGINS>
module ietf-voucher {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-voucher";
prefix vch;
import ietf-yang-types {
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prefix yang;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-inet-types {
prefix ietf;
reference
"RFC 6991: Common YANG Data Types";
}
import ietf-yang-structure-ext {
prefix sx;
}
organization
"IETF ANIMA Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/anima/>
WG List: <mailto:anima@ietf.org>
Author: Kent Watsen
<mailto:kwatsen@juniper.net>
Author: Max Pritikin
<mailto:pritikin@cisco.com>
Author: Michael Richardson
<mailto:mcr+ietf@sandelman.ca>
Author: Toerless Eckert
<mailto:tte+ietf@cs.fau.de>";
description
"This module defines the format for a voucher, which is
produced by a pledge's manufacturer or delegate (MASA)
to securely assign a pledge to an 'owner', so that the
pledge may establish a secure connection to the owner's
network infrastructure.
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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2023 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
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This version of this YANG module is part of RFC 8366; see the
RFC itself for full legal notices.";
revision 2023-01-10 {
description
"updated to support new assertion enumerated type";
reference
"RFC ZZZZ Voucher Profile for Bootstrapping Protocols";
}
// Top-level statement
sx:structure voucher {
uses voucher-artifact-grouping;
}
// Grouping defined for future augmentations
grouping voucher-artifact-grouping {
description
"Grouping to allow reuse/extensions in future work.";
container voucher {
description
"A voucher assigns a pledge to an owner using
the (pinned-domain-cert) value.";
leaf created-on {
type yang:date-and-time;
mandatory false;
description
"A value indicating the date this voucher was created.
This node is primarily for human consumption and auditing.
Future work MAY create verification requirements based on
this node.";
}
leaf expires-on {
type yang:date-and-time;
must 'not(../nonce)';
description
"A value indicating when this voucher expires. The node is
optional as not all pledges support expirations, such as
pledges lacking a reliable clock.
If this field exists, then the pledges MUST ensure that
the expires-on time has not yet passed. A pledge without
an accurate clock cannot meet this requirement.
The expires-on value MUST NOT exceed the expiration date
of any of the listed 'pinned-domain-cert' certificates.";
}
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leaf assertion {
type enumeration {
enum verified {
value 0;
description
"Indicates that the ownership has been positively
verified by the MASA (e.g., through sales channel
integration).";
}
enum logged {
value 1;
description
"Indicates that the voucher has been issued after
minimal verification of ownership or control. The
issuance has been logged for detection of
potential security issues (e.g., recipients of
vouchers might verify for themselves that unexpected
vouchers are not in the log). This is similar to
unsecured trust-on-first-use principles but with the
logging providing a basis for detecting unexpected
events.";
}
enum proximity {
value 2;
description
"Indicates that the voucher has been issued after
the MASA verified a proximity proof provided by the
device and target domain. The issuance has been
logged for detection of potential security issues.";
}
enum agent-proximity {
value 3;
description
"Mostly identical to proximity, but
indicates that the voucher has been issued
after the MASA has verified a statement that
a registrar agent has made contact with the device.";
}
}
}
leaf serial-number {
type string;
mandatory true;
description
"The serial-number of the hardware. When processing a
voucher, a pledge MUST ensure that its serial-number
matches this value. If no match occurs, then the
pledge MUST NOT process this voucher.";
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}
leaf idevid-issuer {
type binary;
description
"The Authority Key Identifier OCTET STRING (as defined in
Section 4.2.1.1 of RFC 5280) from the pledge's IDevID
certificate. Optional since some serial-numbers are
already unique within the scope of a MASA.
Inclusion of the statistically unique key identifier
ensures statistically unique identification of the
hardware.
When processing a voucher, a pledge MUST ensure that its
IDevID Authority Key Identifier matches this value. If no
match occurs, then the pledge MUST NOT process this
voucher.
When issuing a voucher, the MASA MUST ensure that this
field is populated for serial-numbers that are not
otherwise unique within the scope of the MASA.";
}
leaf pinned-domain-cert {
type binary;
mandatory false;
description
"An X.509 v3 certificate structure, as specified by
RFC 5280, using Distinguished Encoding Rules (DER)
encoding, as defined in ITU-T X.690.
This certificate is used by a pledge to trust a Public Key
Infrastructure in order to verify a domain certificate
supplied to the pledge separately by the bootstrapping
protocol. The domain certificate MUST have this
certificate somewhere in its chain of certificates.
This certificate MAY be an end-entity certificate,
including a self-signed entity.";
reference
"RFC 5280:
Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile.
ITU-T X.690:
Information technology - ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
leaf domain-cert-revocation-checks {
type boolean;
description
"A processing instruction to the pledge that it MUST (true)
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or MUST NOT (false) verify the revocation status for the
pinned domain certificate. If this field is not set, then
normal PKIX behavior applies to validation of the domain
certificate.";
}
leaf nonce {
type binary {
length "8..32";
}
must 'not(../expires-on)';
description
"A value that can be used by a pledge in some bootstrapping
protocols to enable anti-replay protection. This node is
optional because it is not used by all bootstrapping
protocols.
When present, the pledge MUST compare the provided nonce
value with another value that the pledge randomly
generated and sent to a bootstrap server in an earlier
bootstrapping message. If the value is present, but
the values do not match, then the pledge MUST NOT process
this voucher.";
}
leaf pinned-domain-pubk {
type binary;
description
"The pinned-domain-pubk may replace the
pinned-domain-cert in constrained uses of
the voucher. The pinned-domain-pubk
is the Raw Public Key of the Registrar.
This field is encoded as a Subject Public Key Info block
as specified in RFC7250, in section 3.
The ECDSA algorithm MUST be supported.
The EdDSA algorithm as specified in
draft-ietf-tls-rfc4492bis-17 SHOULD be supported.
Support for the DSA algorithm is not recommended.
Support for the RSA algorithm is a MAY.";
}
leaf pinned-domain-pubk-sha256 {
type binary;
description
"The pinned-domain-pubk-sha256 is a second
alternative to pinned-domain-cert. In many cases the
public key of the domain has already been transmitted
during the key agreement process, and it is wasteful
to transmit the public key another two times.
The use of a hash of public key info, at 32-bytes for
sha256 is a significant savings compared to an RSA
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public key, but is only a minor savings compared to
a 256-bit ECDSA public-key.
Algorithm agility is provided by extensions to this
specification which can define a new leaf for another
hash type.";
}
leaf last-renewal-date {
type yang:date-and-time;
must '../expires-on';
description
"The date that the MASA projects to be the last date it
will renew a voucher on. This field is merely
informative; it is not processed by pledges.
Circumstances may occur after a voucher is generated that
may alter a voucher's validity period. For instance,
a vendor may associate validity periods with support
contracts, which may be terminated or extended
over time.";
}
// from BRSKI-CLOUD
leaf est-domain {
type ietf:uri;
description
"The est-domain is a URL to which the Pledge should
continue doing enrollment rather than with the
Cloud Registrar.
The pinned-domain-cert contains a trust-anchor
which is to be used to authenticate the server
found at this URI.
";
}
leaf additional-configuration {
type ietf:uri;
description
"The additional-configuration attribute contains a
URL to which the Pledge can retrieve additional
configuration information.
The contents of this URL are vendor specific.
This is intended to do things like configure
a VoIP phone to point to the correct hosted
PBX, for example.";
}
} // end voucher
} // end voucher-grouping
}
<CODE ENDS>
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7.4. ietf-voucher SID values
[RFC9148] explains how to serialize YANG into CBOR, and for this a
series of SID values are required. While [I-D.ietf-core-sid] defines
the management process for these values, due to the immaturity of the
tooling around this YANG-SID mechanisms, the following values are
considered normative. It is believed, however, that they will not
change.
SID Assigned to
--------- --------------------------------------------------
2451 data /ietf-voucher:voucher/voucher
2452 data /ietf-voucher:voucher/voucher/assertion
2453 data /ietf-voucher:voucher/voucher/created-on
2454 data .../domain-cert-revocation-checks
2455 data /ietf-voucher:voucher/voucher/expires-on
2456 data /ietf-voucher:voucher/voucher/idevid-issuer
2457 data /ietf-voucher:voucher/voucher/last-renewal-date
2458 data /ietf-voucher:voucher/voucher/nonce
2459 data /ietf-voucher:voucher/voucher/pinned-domain-cert
2460 data /ietf-voucher:voucher/voucher/pinned-domain-pubk
2461 data .../pinned-domain-pubk-sha256
2462 data /ietf-voucher:voucher/voucher/serial-number
2463 data .../additional-configuration
2466 data /ietf-voucher:voucher/voucher/est-domain
The "assertion" attribute is an enumerated type [RFC8366], and the
current PYANG tooling does not document the valid values for this
attribute. In the JSON serialization, the literal strings from the
enumerated types are used so there is no ambiguity. In the CBOR
serialization, a small integer is used. This following values are
documented here, but the YANG module should be considered
authoritative. No IANA registry is provided or necessary because the
YANG module (and this document) would be extended when there are new
entries to make.
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+=========+=================+
| Integer | Assertion Type |
+=========+=================+
| 0 | verified |
+---------+-----------------+
| 1 | logged |
+---------+-----------------+
| 2 | proximity |
+---------+-----------------+
| 3 | agent-proximity |
+---------+-----------------+
Table 2: CBOR integers
for the "assertion"
attribute enum
8. Voucher Request Artifact
[BRSKI], Section 3 defined a Voucher-Request Artifact as an augmented
artifact from the Voucher Artifact originally defined in [RFC8366].
That definition has been moved to this document, and translated from
YANG-DATA [RFC8040] to the SX:STRUCTURE extension [RFC8791].
8.1. Tree Diagram
The following tree diagram illustrates a high-level view of a voucher
request document. The notation used in this diagram is described in
[RFC8340]. Each node in the diagram is fully described by the YANG
module in Section 8.2.
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module: ietf-voucher-request
structure voucher:
+-- 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
+-- pinned-domain-pubk? binary
+-- pinned-domain-pubk-sha256? binary
+-- last-renewal-date?
| yang:date-and-time
+-- est-domain? ietf:uri
+-- additional-configuration? ietf:uri
+-- prior-signed-voucher-request? binary
+-- proximity-registrar-cert? binary
+-- proximity-registrar-pubk? binary
+-- proximity-registrar-pubk-sha256? binary
+-- agent-signed-data? binary
+-- agent-provided-proximity-registrar-cert? binary
+-- agent-sign-cert? binary
8.2. "ietf-voucher-request" Module
The ietf-voucher-request YANG module is derived from the ietf-voucher
module.
<CODE BEGINS>
module ietf-voucher-request {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-voucher-request";
prefix vcr;
import ietf-yang-structure-ext {
prefix sx;
}
import ietf-voucher {
prefix vch;
description
"This module defines the format for a voucher,
which is produced by a pledge's manufacturer or
delegate (MASA) to securely assign a pledge to
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an 'owner', so that the pledge may establish a secure
connection to the owner's network infrastructure";
reference
"RFC 8366: Voucher Artifact for
Bootstrapping Protocols";
}
organization
"IETF ANIMA Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/anima/>
WG List: <mailto:anima@ietf.org>
Author: Kent Watsen
<mailto:kent+ietf@watsen.net>
Author: Michael H. Behringer
<mailto:Michael.H.Behringer@gmail.com>
Author: Toerless Eckert
<mailto:tte+ietf@cs.fau.de>
Author: Max Pritikin
<mailto:pritikin@cisco.com>
Author: Michael Richardson
<mailto:mcr+ietf@sandelman.ca>";
description
"This module defines the format for a voucher request.
It is a superset of the voucher itself.
It provides content to the MASA for consideration
during a voucher request.
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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the
RFC itself for full legal notices.";
revision 2023-01-10 {
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description
"Initial version";
reference
"RFC XXXX: Bootstrapping Remote Secure Key Infrastructure";
}
// Top-level statement
sx:structure voucher {
uses voucher-request-grouping;
}
// Grouping defined for future usage
grouping voucher-request-grouping {
description
"Grouping to allow reuse/extensions in future work.";
uses vch:voucher-artifact-grouping {
refine "voucher/created-on" {
mandatory false;
}
refine "voucher/pinned-domain-cert" {
mandatory false;
description
"A pinned-domain-cert field
is not valid in a voucher request, and
any occurrence MUST be ignored";
}
refine "voucher/last-renewal-date" {
description
"A last-renewal-date field
is not valid in a voucher request, and
any occurrence MUST be ignored";
}
refine "voucher/domain-cert-revocation-checks" {
description
"The domain-cert-revocation-checks field
is not valid in a voucher request, and
any occurrence MUST be ignored";
}
refine "voucher/assertion" {
mandatory false;
description
"Any assertion included in registrar voucher
requests SHOULD be ignored by the MASA.";
}
augment "voucher" {
description
"Adds leaf nodes appropriate for requesting vouchers.";
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leaf prior-signed-voucher-request {
type binary;
description
"If it is necessary to change a voucher, or re-sign and
forward a voucher that was previously provided along a
protocol path, then the previously signed voucher SHOULD
be included in this field.
For example, a pledge might sign a voucher request
with a proximity-registrar-cert, and the registrar
then includes it as the prior-signed-voucher-request
field. This is a simple mechanism for a chain of
trusted parties to change a voucher request, while
maintaining the prior signature information.
The Registrar and MASA MAY examine the prior signed
voucher information for the
purposes of policy decisions. For example this
information could be useful to a MASA to determine
that both pledge and registrar agree on proximity
assertions. The MASA SHOULD remove all
prior-signed-voucher-request information when
signing a voucher for imprinting so as to minimize
the final voucher size.";
}
leaf proximity-registrar-cert {
type binary;
description
"An X.509 v3 certificate structure as specified by
RFC 5280, Section 4 encoded using the ASN.1
distinguished encoding rules (DER), as specified
in [ITU.X690.1994].
The first certificate in the Registrar TLS server
certificate_list sequence (the end-entity TLS
certificate, see [RFC8446]) presented by the Registrar
to the Pledge.
This MUST be populated in a Pledge's voucher request
when a proximity assertion is requested.";
}
leaf proximity-registrar-pubk {
type binary;
description
"The proximity-registrar-pubk replaces
the proximity-registrar-cert in constrained uses of
the voucher-request.
The proximity-registrar-pubk is the
Raw Public Key of the Registrar. This field is encoded
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as specified in RFC7250, section 3.
The ECDSA algorithm MUST be supported.
The EdDSA algorithm as specified in
draft-ietf-tls-rfc4492bis-17 SHOULD be supported.
Support for the DSA algorithm is not recommended.
Support for the RSA algorithm is a MAY, but due to
size is discouraged.";
}
leaf proximity-registrar-pubk-sha256 {
type binary;
description
"The proximity-registrar-pubk-sha256
is an alternative to both
proximity-registrar-pubk and pinned-domain-cert.
In many cases the public key of the domain has already
been transmitted during the key agreement protocol,
and it is wasteful to transmit the public key another
two times.
The use of a hash of public key info, at 32-bytes for
sha256 is a significant savings compared to an RSA
public key, but is only a minor savings compared to
a 256-bit ECDSA public-key.
Algorithm agility is provided by extensions to this
specification which may define a new leaf for another
hash type.";
}
leaf agent-signed-data {
type binary;
description
"The agent-signed-data field contains a JOSE [RFC7515]
object provided by the Registrar-Agent to the Pledge.
This artifact is signed by the Registrar-Agent
and contains a copy of the pledge's serial-number.";
}
leaf agent-provided-proximity-registrar-cert {
type binary;
description
"An X.509 v3 certificate structure, as specified by
RFC 5280, Section 4, encoded using the ASN.1
distinguished encoding rules (DER), as specified
in ITU X.690.
The first certificate in the registrar TLS server
certificate_list sequence (the end-entity TLS
certificate; see RFC 8446) presented by the
registrar to the registrar-agent and provided to
the pledge.
This MUST be populated in a pledge's voucher-request
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when an agent-proximity assertion is requested.";
reference
"ITU X.690: Information Technology - ASN.1 encoding
rules: Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER)
RFC 5280: Internet X.509 Public Key Infrastructure
Certificate and Certificate Revocation List (CRL)
Profile
RFC 8446: The Transport Layer Security (TLS)
Protocol Version 1.3";
}
leaf agent-sign-cert {
type binary;
description
"An X.509 v3 certificate structure, as specified by
RFC 5280, Section 4, encoded using the ASN.1
distinguished encoding rules (DER), as specified
in ITU X.690.
This certificate can be used by the pledge,
the registrar, and the MASA to verify the signature
of agent-signed-data. It is an optional component
for the pledge-voucher request.
This MUST be populated in a registrar's
voucher-request when an agent-proximity assertion
is requested.";
reference
"ITU X.690: Information Technology - ASN.1 encoding
rules: Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER)
RFC 5280: Internet X.509 Public Key Infrastructure
Certificate and Certificate Revocation List (CRL)
Profile";
}
}
}
}
}
<CODE ENDS>
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8.3. ietf-voucher-request SID values
[RFC9148] explains how to serialize YANG into CBOR, and for this a
series of SID values are required. While [I-D.ietf-core-sid] defines
the management process for these values, due to the immaturity of the
tooling around this YANG-SID mechanisms, the following values are
considered normative. It is believed, however, that they will not
change.
SID Assigned to
--------- --------------------------------------------------
2501 data /ietf-voucher-request:voucher/voucher
2515 data .../agent-provided-proximity-registrar-cert
2516 data .../agent-sign-cert
2517 data .../agent-signed-data
2502 data /ietf-voucher-request:voucher/voucher/assertion
2503 data /ietf-voucher-request:voucher/voucher/created-on
2504 data .../domain-cert-revocation-checks
2505 data /ietf-voucher-request:voucher/voucher/expires-on
2506 data .../idevid-issuer
2507 data .../last-renewal-date
2508 data /ietf-voucher-request:voucher/voucher/nonce
2509 data .../pinned-domain-cert
2518 data .../pinned-domain-pubk
2519 data .../pinned-domain-pubk-sha256
2510 data .../prior-signed-voucher-request
2511 data .../proximity-registrar-cert
2513 data .../proximity-registrar-pubk
2512 data .../proximity-registrar-pubk-sha256
2514 data .../serial-number
WARNING, obsolete definitions
The "assertion" attribute is an enumerated type, and has values as
defined above in Table 2.
9. Design Considerations
9.1. Renewals Instead of Revocations
The lifetimes of vouchers may vary. In some onboarding protocols,
the vouchers may be created and consumed immediately, whereas in
other onboarding solutions, there may be a significant time delay
between when a voucher is created and when it is consumed. In cases
when there is a time delay, there is a need for the pledge to ensure
that the assertions made when the voucher was created are still
valid.
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A revocation artifact is generally used to verify the continued
validity of an assertion such as a PKIX certificate, web token, or a
"voucher". With this approach, a potentially long-lived assertion is
paired with a reasonably fresh revocation status check to ensure that
the assertion is still valid. However, this approach increases
solution complexity, as it introduces the need for additional
protocols and code paths to distribute and process the revocations.
Addressing the shortcomings of revocations, this document recommends
instead the use of lightweight renewals of short-lived non-revocable
vouchers. That is, rather than issue a long-lived voucher, where the
'expires-on' leaf is set to some distant date, the expectation is for
the MASA to instead issue a short-lived voucher, where the 'expires-
on' leaf is set to a relatively near date, along with a promise
(reflected in the 'last-renewal-date' field) to reissue the voucher
again when needed. Importantly, while issuing the initial voucher
may incur heavyweight verification checks ("Are you who you say you
are?" "Does the pledge actually belong to you?"), reissuing the
voucher should be a lightweight process, as it ostensibly only
updates the voucher's validity period. With this approach, there is
only the one artifact, and only one code path is needed to process
it; there is no possibility of a pledge choosing to skip the
revocation status check because, for instance, the OCSP Responder is
not reachable.
While this document recommends issuing short-lived vouchers, the
voucher artifact does not restrict the ability to create long-lived
voucher, if required; however, no revocation method is described.
Note that a voucher may be signed by a chain of intermediate CAs
leading up to the trust anchor certificate known by the pledge. Even
though the voucher itself is not revocable, it may still be revoked,
per se, if one of the intermediate CA certificates is revoked.
9.2. Voucher Per Pledge
The solution described herein originally enabled a single voucher to
apply to many pledges, using lists of regular expressions to
represent ranges of serial-numbers. However, it was determined that
blocking the renewal of a voucher that applied to many devices would
be excessive when only the ownership for a single pledge needed to be
blocked. Thus, the voucher format now only supports a single serial-
number to be listed.
10. Security Considerations
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10.1. Clock Sensitivity
An attacker could use an expired voucher to gain control over a
device that has no understanding of time. The device cannot trust
NTP as a time reference, as an attacker could control the NTP stream.
There are three things to defend against this: 1) devices are
required to verify that the expires-on field has not yet passed, 2)
devices without access to time can use nonces to get ephemeral
vouchers, and 3) vouchers without expiration times may be used, which
will appear in the audit log, informing the security decision.
This document defines a voucher format that contains time values for
expirations, which require an accurate clock in order to be processed
correctly. Vendors planning on issuing vouchers with expiration
values must ensure that devices have an accurate clock when shipped
from manufacturing facilities and take steps to prevent clock
tampering. If it is not possible to ensure clock accuracy, then
vouchers with expirations should not be issued.
10.2. Protect Voucher PKI in HSM
Pursuant the recommendation made in Section 6.1 for the MASA to be
deployed as an online voucher signing service, it is RECOMMENDED that
the MASA's private key used for signing vouchers is protected by a
hardware security module (HSM).
10.3. Test Domain Certificate Validity When Signing
If a domain certificate is compromised, then any outstanding vouchers
for that domain could be used by the attacker. The domain
administrator is clearly expected to initiate revocation of any
domain identity certificates (as is normal in PKI solutions).
Similarly, they are expected to contact the MASA to indicate that an
outstanding (presumably short lifetime) voucher should be blocked
from automated renewal. Protocols for voucher distribution are
RECOMMENDED to check for revocation of domain identity certificates
before the signing of vouchers.
10.4. YANG Module Security Considerations
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.
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Implementations should be aware that the signed data is only
protected from external modification; the data is still visible.
This potential disclosure of information doesn't affect security so
much as privacy. In particular, adversaries can glean information
such as which devices belong to which organizations and which CRL
Distribution Point and/or OCSP Responder URLs are accessed to
validate the vouchers. When privacy is important, the CMS signed-
data content type SHOULD be encrypted, either by conveying it via a
mutually authenticated secure transport protocol (e.g., TLS
[RFC5246]) or by encapsulating the signed-data content type with an
enveloped-data content type (Section 6 of [RFC5652]), though details
for how to do this are outside the scope of this document.
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
[YANG-GUIDE].
11. IANA Considerations
11.1. The IETF XML Registry
This document registers two URIs in the "IETF XML Registry"
[RFC3688].
IANA has registered the following:
URI: urn:ietf:params:xml:ns:yang:ietf-voucher
Registrant Contact: The ANIMA WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
This reference should be updated to point to this document.
11.2. The YANG Module Names Registry
This document registers two YANG module in the "YANG Module Names"
registry [RFC6020].
IANA has registred the following:
name: ietf-voucher
namespace: urn:ietf:params:xml:ns:yang:ietf-voucher
prefix: vch
reference: :RFC 8366
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This reference should be updated to point to this document.
11.3. The Media Types Registry
IANA has registered the media type: voucher-cms+json, and this
registration should be updated to point to this document.
11.4. The SMI Security for S/MIME CMS Content Type Registry
IANA has registered the OID 1.2.840.113549.1.9.16.1.40, id-ct-
animaJSONVoucher. This registration should be updated to point to
this document.
12. References
12.1. Normative References
[BRSKI] Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructure (BRSKI)", RFC 8995, DOI 10.17487/RFC8995,
May 2021, <https://www.rfc-editor.org/rfc/rfc8995>.
[cBRSKI] Richardson, M., Van der Stok, P., Kampanakis, P., and E.
Dijk, "Constrained Bootstrapping Remote Secure Key
Infrastructure (cBRSKI)", Work in Progress, Internet-
Draft, draft-ietf-anima-constrained-voucher-24, 3 March
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
anima-constrained-voucher-24>.
[CLOUD] Friel, O., Shekh-Yusef, R., and M. Richardson, "BRSKI
Cloud Registrar", Work in Progress, Internet-Draft, draft-
ietf-anima-brski-cloud-08, 24 August 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-anima-
brski-cloud-08>.
[I-D.ietf-anima-constrained-voucher]
Richardson, M., Van der Stok, P., Kampanakis, P., and E.
Dijk, "Constrained Bootstrapping Remote Secure Key
Infrastructure (cBRSKI)", Work in Progress, Internet-
Draft, draft-ietf-anima-constrained-voucher-24, 3 March
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
anima-constrained-voucher-24>.
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[I-D.ietf-anima-jws-voucher]
Werner, T. and M. Richardson, "JWS signed Voucher
Artifacts for Bootstrapping Protocols", Work in Progress,
Internet-Draft, draft-ietf-anima-jws-voucher-09, 29 August
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
anima-jws-voucher-09>.
[I-D.ietf-core-sid]
Veillette, M., Pelov, A., Petrov, I., Bormann, C., and M.
Richardson, "YANG Schema Item iDentifier (YANG SID)", Work
in Progress, Internet-Draft, draft-ietf-core-sid-24, 22
December 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-core-sid-24>.
[ITU-T.X690.2015]
International Telecommunication Union, "Information
Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, ISO/IEC 8825-1, August 2015,
<https://www.itu.int/rec/T-REC-X.690/>.
[jBRSKI] Werner, T. and M. Richardson, "JWS signed Voucher
Artifacts for Bootstrapping Protocols", Work in Progress,
Internet-Draft, draft-ietf-anima-jws-voucher-09, 29 August
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
anima-jws-voucher-09>.
[PRM] Fries, S., Werner, T., Lear, E., and M. Richardson, "BRSKI
with Pledge in Responder Mode (BRSKI-PRM)", Work in
Progress, Internet-Draft, draft-ietf-anima-brski-prm-11,
20 November 2023, <https://datatracker.ietf.org/doc/html/
draft-ietf-anima-brski-prm-11>.
[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/rfc/rfc2119>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/rfc/rfc5652>.
[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/rfc/rfc6020>.
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[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/rfc/rfc7950>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/rfc/rfc7951>.
[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/rfc/rfc8174>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>.
[RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data
Structure Extensions", RFC 8791, DOI 10.17487/RFC8791,
June 2020, <https://www.rfc-editor.org/rfc/rfc8791>.
[RFC9148] van der Stok, P., Kampanakis, P., Richardson, M., and S.
Raza, "EST-coaps: Enrollment over Secure Transport with
the Secure Constrained Application Protocol", RFC 9148,
DOI 10.17487/RFC9148, April 2022,
<https://www.rfc-editor.org/rfc/rfc9148>.
[ZERO-TOUCH]
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/rfc/rfc8572>.
12.2. Informative References
[CBOR] Internet Standard 94,
<https://www.rfc-editor.org/info/std94>.
At the time of writing, this STD comprises the following:
Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/info/rfc8949>.
[COSE] Internet Standard 96,
<https://www.rfc-editor.org/info/std96>.
At the time of writing, this STD comprises the following:
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Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/info/rfc9052>.
Schaad, J., "CBOR Object Signing and Encryption (COSE):
Countersignatures", STD 96, RFC 9338,
DOI 10.17487/RFC9338, December 2022,
<https://www.rfc-editor.org/info/rfc9338>.
[I-D.selander-ace-ake-authz]
Selander, G., Mattsson, J. P., VuÄinić, M., Richardson,
M., and A. Schellenbaum, "Lightweight Authorization for
Authenticated Key Exchange.", Work in Progress, Internet-
Draft, draft-selander-ace-ake-authz-05, 18 April 2022,
<https://datatracker.ietf.org/doc/html/draft-selander-ace-
ake-authz-05>.
[imprinting]
Wikipedia, "Wikipedia article: Imprinting", February 2018,
<https://en.wikipedia.org/w/
index.php?title=Imprinting_(psychology)&oldid=825757556>.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/rfc/rfc7515>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/rfc/rfc3688>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/rfc/rfc5246>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/rfc/rfc6125>.
[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/rfc/rfc6241>.
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[RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <https://www.rfc-editor.org/rfc/rfc7435>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/rfc/rfc8040>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/rfc/rfc8340>.
[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/rfc/rfc8366>.
[SECUREJOIN]
Richardson, M., "6tisch Secure Join protocol", Work in
Progress, Internet-Draft, draft-ietf-6tisch-dtsecurity-
secure-join-01, 25 February 2017,
<https://datatracker.ietf.org/doc/html/draft-ietf-6tisch-
dtsecurity-secure-join-01>.
[Stajano99theresurrecting]
Stajano, F. and R. Anderson, "The Resurrecting Duckling:
Security Issues for Ad-Hoc Wireless Networks", 1999, <http
s://www.cl.cam.ac.uk/research/dtg/www/files/publications/
public/files/tr.1999.2.pdf>.
[YANG-GUIDE]
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/rfc/rfc8407>.
[YANGCBOR] Veillette, M., Ed., Petrov, I., Ed., Pelov, A., Bormann,
C., and M. Richardson, "Encoding of Data Modeled with YANG
in the Concise Binary Object Representation (CBOR)",
RFC 9254, DOI 10.17487/RFC9254, July 2022,
<https://www.rfc-editor.org/rfc/rfc9254>.
Acknowledgements
The authors would like to thank for following for lively discussions
on list and in the halls (ordered by last name): William Atwood,
Michael H. Behringer, Esko Dijk, Steffen Fries, Sheng Jiang, Thomas
Werner.
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Authors' Addresses
Kent Watsen
Watsen Networks
Email: kent+ietf@watsen.net
Michael C. Richardson
Sandelman Software
Email: mcr+ietf@sandelman.ca
URI: http://www.sandelman.ca/
Max Pritikin
Cisco Systems
Email: pritikin@cisco.com
Toerless Eckert
Futurewei Technologies Inc.
2330 Central Expy
Santa Clara, 95050
United States of America
Email: tte+ietf@cs.fau.de
Qiufang Ma
Huawei
101 Software Avenue, Yuhua District
Nanjing
210012
China
Email: maqiufang1@huawei.com
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