draft-ietf-anima-voucher-00.txt   draft-ietf-anima-voucher-01.txt 
ANIMA Working Group K. Watsen ANIMA Working Group K. Watsen
Internet-Draft Juniper Networks Internet-Draft Juniper Networks
Intended status: Standards Track M. Richardson Intended status: Standards Track M. Richardson
Expires: July 8, 2017 SSW Expires: September 14, 2017 Sandelman Software
M. Pritikin M. Pritikin
Cisco Systems Cisco Systems
T. Eckert T. Eckert
January 4, 2017 March 13, 2017
Voucher and Voucher Revocation Profiles for Bootstrapping Protocols Voucher Profile for Bootstrapping Protocols
draft-ietf-anima-voucher-00 draft-ietf-anima-voucher-01
Abstract Abstract
This memo defines the two artifacts "voucher" and "voucher- This document defines a strategy to securely assign a pledge to an
revocation", which are YANG-defined structures that have been signed owner, using an artifact signed, directly or indirectly, by the
by a TBD algorithm. pledge's manufacturer. This artifact is known as a "voucher".
The voucher artifact is generated by the device's manufacture or
delegate. The voucher's purpose is to securely assign one or more
devices to an owner. The voucher informs each device which entity it
should consider to be its owner.
The voucher revocation artifact is used by the manufacturer or The voucher artifact is a YANG-defined JSON document that has been
delegate (i.e. the issuer of the voucher) to revoke vouchers, if signed using a PKCS#7 structure. The voucher artifact is generated
ever necessary. The voucher revocation format defined herein by the pledge's manufacture or delegate (i.e. the MASA).
supports both issuer-wide and voucher-specific constructs, enabling
usage flexibility.
For both artifacts, this memo only defines the artifact, leaving it This document only defines the voucher artifact, leaving it to other
to future work to describe specialized protocols for accessing them. documents to describe specialized protocols for accessing it.
Status of This Memo Status of This Memo
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Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Tree Diagram Notation . . . . . . . . . . . . . . . . . . . . 3 3. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
4. Voucher . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Survey of Voucher Types . . . . . . . . . . . . . . . . . . . 4
4.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 4 5. Voucher . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 4 5.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 7
4.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 5 5.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 7
5. Voucher Revocation . . . . . . . . . . . . . . . . . . . . . 9 5.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 9 6. Design Considerations . . . . . . . . . . . . . . . . . . . . 14
5.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 10 6.1. Renewals instead of Revocations . . . . . . . . . . . . . 14
5.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 11 6.2. Voucher Per Pledge . . . . . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6.1. Clock Sensitivity . . . . . . . . . . . . . . . . . . . . 16 7.1. Clock Sensitivity . . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7.2. Protect Voucher PKI in HSM . . . . . . . . . . . . . . . 16
7.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 16 7.3. Test Domain Certificate Validity when Signing . . . . . . 16
7.2. The YANG Module Names Registry . . . . . . . . . . . . . 17 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 8.1. The IETF XML Registry . . . . . . . . . . . . . . . . . . 17
8.2. The YANG Module Names Registry . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . 17 9.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . 18 9.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 19 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
This document defines a strategy to securely assign devices to an This document defines a strategy to securely assign a pledge to an
owner, using an artifact signed, directly or indirectly, by the owner, using an artifact signed, directly or indirectly, by the
device's manufacturer. This artifact is known as the voucher. pledge's manufacturer or delegate (i.e. the MASA). This artifact is
known as the voucher.
The voucher artifact is a JSON document, conforming to a data model
described by YANG [RFC7950], that has been signed using a PKCS#7
structure.
A voucher may be useful in several contexts, but the driving A voucher may be useful in several contexts, but the driving
motivation herein is to support secure bootstrapping mechanisms, such motivation herein is to support secure bootstrapping mechanisms.
as are defined in [draft-ietf-netconf-zerotouch] and Assigning ownership is important to bootstrapping mechanisms so that
[draft-ietf-anima-bootstrapping-keyinfra]. Assigning ownership is the pledge can authenticate the network that's trying to take control
important to bootstrapping mechanisms so that the booting device can of it.
authenticate the network that's trying to take control of it.
The lifetimes of vouchers may vary. In some bootstrapping protocols The lifetimes of vouchers may vary. In some bootstrapping protocols
the vouchers may be ephemeral, whereas in others the vouchers may be the vouchers may be ephemeral, whereas in others the vouchers may be
potentially long-lived. In order to support the second category of potentially long-lived. In order to support the second category of
vouchers, this document also defines a voucher revocation artifact, vouchers, this document recommends using short-life vouchers with
enabling the manufacturer or delegate to communicate the validity of programatic renewal, enabling the MASA to communicate the ongoing
its vouchers. validity of vouchers.
For both artifacts, this memo only defines the artifact, leaving it
to future work to describe specialized protocols for accessing them.
This document uses YANG [RFC7950] to define the voucher and voucher
revocation formats. YANG is a data modeling language with
established mappings to XML and JSON, with mappings to other
encodings in progress. Which encodings a particular solution uses is
outside the scope of this document.
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the
sections below are to be interpreted as described in RFC 2119
[RFC2119].
3. Tree Diagram Notation This document only defines the voucher artifact, leaving it to other
documents to describe specialized protocols for accessing it. Some
bootstrapping protocols using the voucher artifact defined in this
draft include: [I-D.ietf-netconf-zerotouch],
[I-D.ietf-6tisch-dtsecurity-secure-join], and
[I-D.ietf-anima-bootstrapping-keyinfra]).
The meaning of the symbols in the above diagram is as follows: 2. Terminology
o Brackets "[" and "]" enclose list keys. The following terms are defined for clarity:
o Braces "{" and "}" enclose feature names, and indicate that the Imprint: The process where a device obtains the cryptographic key
named feature must be present for the subtree to be present. material to identify and trust future interactions with a network.
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. An equivalent for a device is to obtain the fingerprint
of the network's root certification authority certificate. A
device that imprints on an attacker suffers a similar fate to a
duckling that imprints on a hungry wolf. Securely imprinting is a
primary focus of this document.[imprinting]. The analogy to
Lorenz's work was first noted in [Stajano99theresurrecting].
o Abbreviations before data node names: "rw" (read-write) represents Pledge: The prospective device attempting to find and join a secure
configuration data and "ro" (read-only) represents state data. remote key infrastructure. When shipped it only trusts authorized
representatives of the manufacturer.
o Symbols after data node names: "?" means an optional node, "!" Voucher: A signed statement from the MASA service that indicates to
means a presence container, and "*" denotes a list and leaf-list. a Pledge the cryptographic identity of the Registrar it should
trust. There are different types of vouchers depending on how
that trust asserted. This document describes vouchers in detail.
o Parentheses enclose choice and case nodes, and case nodes are also Domain: The set of entities that trust a common key infrastructure
marked with a colon (":"). trust anchor. This includes the Proxy, Registrar, Domain
Certificate Authority, Management components and any existing
entity that is already a member of the domain.
o Ellipsis ("...") stands for contents of subtrees that are not Domain CA: The domain Certification Authority (CA) provides
shown. certification functionalities to the domain. At a minimum it
provides certification functionalities to a Registrar and stores
the trust anchor that defines the domain. Optionally, it
certifies all elements.
4. Voucher 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". The term JRC is used in common with other bootstrap
mechanisms.
The voucher is generated by the device's manufacture or delegate. MASA Service: A third-party Manufacturer Authorized Signing
The voucher's purpose is to securely assign one or more devices to an Authority (MASA) service on the global Internet. The MASA signs
owner. The voucher informs each device which entity it should vouchers. It also provides a repository for audit log information
consider to be its owner. of privacy protected bootstrapping events. It does not track
ownership. It is trusted by the Pledge.
The voucher is signed by the device's manufacturer or delegate. TOFU: Trust on First Use. Used similarly to [RFC7435]. This is
NOTE: AT THIS TIME, THE SIGNING STRATEGY HAS NOT BEEN SELECTED. where a Pledge device makes no security decisions but rather
simply trusts the first Registrar it is contacted by. This is
also known as the "resurrecting duckling" model.
4.1. Tree Diagram 3. Requirements Language
Following is the tree diagram for the YANG module specified in The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
Section 4.3. Details regarding each node in the tree diagram are "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the
provided in the YANG module. Please see Section 3 for information on sections below are to be interpreted as described in RFC 2119
tree diagram notation. [RFC2119].
module: ietf-voucher 4. Survey of Voucher Types
+--ro voucher
+--ro assertion enumeration
+--ro trusted-ca-certificate? binary
+--ro certificate-id
| +--ro cn-id? string
| +--ro dns-id? string
+--ro unique-id* string
+--ro nonce? string
+--ro created-on? yang:date-and-time
+--ro expires-on? yang:date-and-time
+--ro revocation-location? inet:uri
+--ro additional-data?
4.2. Examples 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 bootstrapping use case.
The following illustrates an ephemeral voucher encoded in JSON: The voucher can impart the following information to the Join
Registrar and Pledge:
{ Assertion Basis: Indicates the method that protects the imprint
"ietf-voucher:voucher": { (this is distinct from the voucher signature that protects the
"assertion": "logged", voucher itself). This might include manufacturer asserted
"trusted-ca-certificate": "base64-encoded X.509 DER", ownership verification, assured logging operations or reliance on
"owner-id": "Registrar3245", Pledge endpoint behavior such as secure root of trust of
"unique-id": "JADA123456789", measurement. The Join Registrar might use this information. Only
"created-on": "2016-10-07T19:31:42Z", some methods are normatively defined in this document. Other
"nonce": "987987623489567" methods are left for future work.
}
}
The following illustrates a long-lived voucher encoded in XML:
<voucher Authentication of Join Registrar: Indicates how the Pledge can
xmlns="urn:ietf:params:xml:ns:yang:ietf-voucher"> authenticate the Join Registrar. This might include an indication
<assertion>verified</assertion> of the private PKIX trust anchor used by the Registrar, or an
<trusted-ca-certificate> indication of a public PKIX trust anchor and additional CN-ID or
base64-encoded X.509 DER DNS-ID information to complete authentication. Symmetric key or
</trusted-ca-certificate> other methods are left for future work.
<certificate-id>
<cn-id>Example Inc.</cn-id> <!-- maybe this should be a DN? -->
<dns-id>example.com</dns-id>
</certificate-id>
<unique-id>AAA123456789</unique-id>
<unique-id>BBB123456789</unique-id>
<unique-id>CCC123456789</unique-id>
<created-on>2016-10-07T19:31:42Z</created-on>
</voucher>
4.3. YANG Module Anti-Replay Protections: Time or nonce based information to
constrain the voucher to time periods or bootstrap attempts.
<CODE BEGINS> file "ietf-voucher@2017-01-04.yang" A number of bootstrapping scenarios can be met using differing
combinations of this information. All scenarios address the primary
threat of a Man-in-The-Middle Registrar gaining control over the
Pledge device. The following combinations are "types" of vouchers:
module ietf-voucher { |Assertion |Registrar ID | Validity |
yang-version 1.1; Voucher |Log-|Veri- |Trust |CN-ID or| RTC | Nonce |
Name | ged| fied |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 | X | | wildcard | optional |
out-of-scope | | | | |
-------------|----|-------|----------------|-------------|
namespace NOTE: All voucher types include a 'Pledge ID serial number'
"urn:ietf:params:xml:ns:yang:ietf-voucher"; (Not shown for space reasons)
prefix "vch";
import ietf-yang-types { prefix yang; } Audit Voucher: An Audit Voucher is named after the logging assertion
import ietf-inet-types { prefix inet; } mechanisms that the Registrar then "audits" to enforce local
policy. The Registrar mitigates a MiTM Registrar by auditing that
an unknown MiTM registrar does not appear in the log entries.
This does not direct prevent the MiTM but provides a response
mechanism that ensures the MiTM is unsuccessful. This advantage
is that actual ownership knowledge is not required on the MASA
service.
organization Nonceless Audit Voucher: An Audit Voucher without a validity period
"IETF ANIMA Working Group"; statement. Fundamentally 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.
contact Ownership Audit Voucher: An Audit Voucher where the MASA service has
"WG Web: <http://tools.ietf.org/wg/anima/> verified the Registrar as the authorized owner. The MASA service
WG List: <mailto:anima@ietf.org> mitigates a MiTM Registrar by refusing to generate Audit Voucher's
Author: Kent Watsen for unauthorized Registrars. The Registrar uses audit techniques
<mailto:kwatsen@juniper.net> to supplement the MASA. This provides an ideal sharing of policy
Author: Max Pritikin decisions and enforcement between the vendor and the owner.
<mailto:pritikin@cisco.com>
Author: Michael Richardson
<mailto:mcr+ietf@sandelman.ca>";
description Ownership ID Voucher: An Ownership ID Voucher is named after
"This module defines the format for a voucher, which is inclusion of the Pledge's CN-ID or DNS-ID within the voucher. An
produced by a device's manufacturer or delegate to securely example Ownership Voucher is defined in
assign one or more devices to an 'owner', so that the [I-D.ietf-netconf-zerotouch]. The MASA service mitigates a MiTM
devices may establish a secure connection to the owner's Registrar by identifying the specific Registrar authorized to own
network infrastructure."; the Pledge. [DISCUSS: still needed?]
revision "2017-01-04" { Bearer Voucher: A Bearer Voucher is named after the inclusion of a
description Registrar ID wildcard. Because the Registrar identity is not
"Initial version"; indicated this voucher type must be treated as a secret and
reference protected from exposure as any 'bearer' of the voucher can claim
"RFC XXXX: Voucher and Voucher Revocation Profiles the Pledge device. Publishing a nonceless bearer voucher
for Bootstrapping Protocols"; effectively turns the specified Pledge into a "TOFU" device with
} minimal mitigation against MiTM Registrars. Bearer vouchers are
out-of-scope.
// top-level container 5. Voucher
container voucher {
config false;
description
"A voucher that can be used to assign one or more devices to
an owner.";
leaf assertion { The voucher's purpose is to securely assign a pledge to an owner.
type enumeration { The voucher informs the pledge which entity it should consider to be
enum verified { its owner.
description
"Indicates that the ownership has been positively
verified by the device's manufacturer or delegate
(e.g., through sales channel integration).";
}
enum logged {
description
"Indicates that this ownership assignment has been
logged into a database maintained by the device's
manufacturer or delegate (voucher transparency).";
}
}
mandatory true;
description
"The assertion is a statement from the manufacturer or
delegate regarding the nature of this voucher. This
allows the device to know what assurance the manufacturer
provides, which supports more detailed policy checks
such as 'I only want to allow verified devices, not
just logged devices'.";
}
leaf trusted-ca-certificate { The voucher is signed a PKCS#7 SignedData structure, as specified by
type binary; Section 9.1 of [RFC2315], encoded using ASN.1 distinguished encoding
description rules (DER), as specified in ITU-T X.690.
"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-T X.690.
This certificate is used by a bootstrapping device to The PKCS#7 structure MUST contain JSON-encoded content conforming to
trust another public key infrastructure, in order to the YANG module specified in Section 5.3.
verify another certificate supplied to the device
separately by the bootstrapping protocol, the other
certificate must have this certificate somewhere in
its chain of certificates.";
reference The PKCS#7 structure MUST also contain a 'signerInfo' structure, as
"RFC 5280: described in Section 9.1 of [RFC2315], containing the signature
Internet X.509 Public Key Infrastructure Certificate generated over the content using the MASA's private key.
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).";
}
container certificate-id { The PKCS#7 structure SHOULD also contain all of the certificates
description leading up to and including the MASA's trust anchor certificate known
"When provided, the device MUST also perform RFC 6125 to the pledges.
style validation of another certificate supplied to
the device separately by the bootstrapping protocol
against all the provided ids.";
leaf cn-id {
type string;
description
"The common name field in the cetificate must match
this value.";
}
leaf dns-id {
type string;
description
"A subjectAltName entry of type dNSName in the
certificate must match this value.";
}
}
leaf-list unique-id { 5.1. Tree Diagram
type string;
min-elements 1;
description
"A regular expression identifying one more more device
unique identifiers (e.g., serial numbers). For instance,
the expression could match just a single serial number,
or it might match a range of serial numbers. Devices
use this value to determine if the voucher applies to
them.";
// Ed. both the zerotouch and brwski solutions are devid The following tree diagram [I-D.bjorklund-netmod-yang-tree-diagrams]
// oriented, and so renaming this field to 'serial-number' illustrates a high-level view of a voucher document. Each field in
// wouldn't be crazy. But devid/serial-number (typically) the voucher is fully described by the YANG module provided in
// assumes physical chassis, is it worth using this Section 5.3. Please review this YANG module for a detailed
// term which might extend to e.g. virtual appliances? description of the voucher format.
}
leaf nonce { module: ietf-voucher
type string; // unit64? +--ro voucher
description +--ro authority-key-identifier? binary
"what can be said about this that's ANIMA-neutral?"; +--ro created-on yang:date-and-time
} +--ro expires-on? yang:date-and-time
+--ro assertion enumeration
+--ro device-identifier string
+--ro trusted-ca-certificate binary
+--ro domain-certificate-identifier
| +--ro subject? binary
| +--ro cn-id? string
| +--ro dns-id? string
+--ro assert-certificate-revocations? boolean
+--ro nonce? binary
+--ro last-renewal-date? yang:date-and-time
leaf created-on { 5.2. Examples
type yang:date-and-time;
description
"The date this voucher was created";
}
leaf expires-on { This section provides a couple Voucher examples for illustration
type yang:date-and-time; purposes.
description
"An optional date value for when this voucher expires.";
}
leaf revocation-location { The following example illustrates an ephemeral voucher (uses a nonce)
type inet:uri; encoded in JSON. As is expected with a dynamically-generated
description voucher, only a single pledge (device-identifier) is specified. The
"A URI indicating where revocation information may be MASA generated this voucher using the 'logged' assertion type,
obtained."; knowing that it would be suitable for the pledge making the request.
}
anydata additional-data { {
description "ietf-voucher:voucher": {
"Additional data signed by the manufacturer. The manufacturer "assertion": "logged",
might put additional data into its vouchers, for human or "trusted-ca-certificate": "base64-encoded X.509 DER",
device consumption."; "device-identifier": "JADA123456789",
"created-on": "2016-10-07T19:31:42Z",
"nonce": "base64-encoded octet string"
}
}
// Ed. is the additional data normative? - if so, should we The following illustrates a long-lived voucher (no nonce), encoded in
// remove this free-form field, and assume it will be formally XML. This particular voucher applies to more than one pledge
// extended later? Note: the zerotouch draft doesn't need this (unique-id), which might relate to, for instance, they were all
// field... issued as part of the same purchase order. This voucher includes
} both a trust anchor certificate (trusted-ca-certificate) as well as
} some additional information (cn-id and dns-id) that can be used to
identify a specific domain certificate issued, perhaps indirectly, by
the trust anchor CA.
} {
"ietf-voucher:voucher": {
"assertion": "verified",
"trusted-ca-certificate": "base64-encoded X.509 DER",
"domain-certificate-identifier": {
"subject": "base64-encoded Subject DER"
},
"device-identifier": "JADA123456789",
"created-on": "2016-10-07T19:31:42Z"
}
}
<CODE ENDS> 5.3. YANG Module
5. Voucher Revocation <CODE BEGINS> file "ietf-voucher@2017-03-13.yang"
The vouchers revocation artifact is used to verify the revocation module ietf-voucher {
status of vouchers. Voucher revocations are signed by the yang-version 1.1;
manufacturer or delegate (i.e. the issuer of the voucher). Vouchers
revocation statements MAY be verified by devices during the
bootstrapping process, or at any time before or after by any entity
(e.g., registrar or equivalent) as needed. Registrars or equivalent
SHOULD verify voucher revocation statements and make policy decisions
in case devices are not doing so themselves.
Revocations are generally needed when it is critical for devices to namespace
know that assurances implied at the time the voucher was signed are "urn:ietf:params:xml:ns:yang:ietf-voucher";
still valid at the time the voucher is being processed. prefix "vch";
As mentioned in Section 1, the lifetimes of vouchers may vary. In import ietf-yang-types {
some bootstrapping protocols the vouchers may be ephemeral, whereas prefix yang;
in others the vouchers may be potentially long-lived. For reference "RFC 6991: Common YANG Data Types";
bootstrapping protocols that support ephemeral vouchers, there is no }
need to support revocations. For bootstrapping protocols that
support long-lived vouchers, the need to support revoking vouchers is
a decision for each manufacturer.
If revocations are not supported then voucher assignments are import ietf-restconf {
essentially forever, which may be acceptable for various kinds of prefix rc;
devices. If revocations are supported, then it becomes possible to description
support various scenarios such as handling a key compromise or change "This import statement is only present to access the yang-data
in ownership. extension defined in RFC 8040. The yang-data extension doesn't
itself have anything to do with RESTCONF, but was placed in the
that RFC for convenience. This extension is being tracked to
be moved to the next version of the YANG modeling language.
Regardless where or how this extension statement is defined,
there should not be any impact to a voucher's encoding.";
reference "RFC 8040: RESTCONF Protocol";
}
The voucher revocation format defined herein supports both issuer- organization
wide (similar to a CRL) or voucher-specific (similar to an OCSP "IETF ANIMA Working Group";
response) constructs, enabling usage flexibility.
NOTE: AT THIS TIME, THE SIGNING STRATEGY HAS NOT BEEN SELECTED. contact
"WG Web: <http://tools.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>";
5.1. Tree Diagram description
"This module defines the format for a voucher, which is produced by
a pledge's manufacturer or delegate (MASA) to securely assign one
or more pledges to an 'owner', so that the pledges may establish a
secure connection to the owner's network infrastructure.";
Following is the tree diagram for the YANG module specified in revision "2017-03-13" {
Section 5.3. Details regarding each node in the tree diagram are description
provided in the YANG module. Please see Section 3 for information on "Initial version";
tree diagram notation. reference
"RFC XXXX: Voucher Profile for Bootstrapping Protocols";
}
module: ietf-voucher-revocation rc:yang-data voucher-artifact {
+--ro voucher-revocation uses voucher-grouping;
+--ro revocation-type enumeration }
+--ro created-on yang:date-and-time
+--ro expires-on? yang:date-and-time
+--ro (voucher-revocation-type)?
| +--:(issuer-wide)
| | +--ro issuer-wide
| | +--ro (list-type)?
| | +--:(whitelist)
| | | +--ro whitelist
| | | +--ro voucher-identifier* string
| | +--:(blacklist)
| | +--ro blacklist
| | +--ro voucher-identifier* string
| +--:(voucher-specific)
| +--ro voucher-specific
| +--ro voucher-identifier string
| +--ro voucher-status enumeration
| +--ro revocation-information
| +--ro revoked-on yang:date-and-time
| +--ro revocation-reason enumeration
+--ro additional-data?
5.2. Examples grouping voucher-grouping {
description
"Grouping only exists for pyang tree output...";
The following illustrates an issuer-wide voucher revocation in XML: container voucher {
config false;
description
"A voucher that can be used to assign one or more
pledges to an owner.";
<voucher-revocation leaf authority-key-identifier {
xmlns="urn:ietf:params:xml:ns:yang:ietf-voucher-revocation"> type binary;
<revocation-type>issuer-wide</revocation-type> description
<created-on>2016-10-31T23:59:59Z</created-on> "The Subject Key Identifier of the MASA's leaf certificate.
<expires-on>2016-12-31T23:59:59Z</expires-on> Enables the pledge a definitively identify the voucher's
<issuer-wide> issuer's certificate. This field is optional as not all
<blacklist> vouchers will be signed by a private key associated with
<voucher-identifier>some fingerprint</voucher-identifier> an X.509 certificate.";
<voucher-identifier>some fingerprint</voucher-identifier> }
<voucher-identifier>some fingerprint</voucher-identifier>
</blacklist>
</issuer-wide>
</voucher>
The following illustrates a voucher-specific revocation in JSON: leaf created-on {
type yang:date-and-time;
mandatory true;
description
"A value indicating the date this voucher was created. This
node is optional because its primary purpose is for human
consumption. However, when present, pledges that have
reliable clocks SHOULD ensure that this created-on value
is not greater than the current time.";
}
{ leaf expires-on {
"ietf-voucher-revocation:voucher-revocation": { type yang:date-and-time;
"revocation-type": "voucher-specific", must "not ../nonce";
"created-on": "2016-10-31T23:59:59Z" description
"expires-on": "2016-12-31T23:59:59Z" "A value indicating when this voucher expires. The node is
"voucher-specific": [ optional as not all pledges support expirations, such as
"voucher-identifier": "some fingerprint", pledges lacking a reliable clock.
"voucher-status": "revoked",
"revocation-information": [
"revoked-on": "2016-11-31T23:59:59Z",
"revocation-reason": "key-compromise"
]
]
}
}
5.3. YANG Module If the pledge supports expirations and the expires-on value
is less then the current time, then the pledge MUST not
process this voucher.";
}
<CODE BEGINS> file "ietf-voucher-revocation@2017-01-04.yang" leaf assertion {
type enumeration {
enum verified {
description
"Indicates that the ownership has been positively
verified by the MASA (e.g., through sales channel
integration).";
}
enum logged {
description
"Indicates that this ownership assignment has been
logged into a database maintained by the MASA, after
first verifying that there has not been a previous
claim in the database for the same pledge (voucher
transparency).";
}
}
mandatory true;
description
"The assertion is a statement from the MASA regarding how
the owner was verified. This statement enables pledges
to support more detailed policy checks. Pledges MUST
ensure that the assertion provided is acceptable before
processing the voucher.";
}
module ietf-voucher-revocation { leaf device-identifier {
yang-version 1.1; type string;
mandatory true;
description
"A unique identifier (e.g., serial number) within the scope
of the MASA.
namespace When processing a vouchers, pledges MUST ensure that their
"urn:ietf:params:xml:ns:yang:ietf-voucher-revocation"; unique identifier matches at least one regular expression in
prefix "vr"; the list. If no matching regular expression is found, the
pledge MUST NOT process this voucher.";
}
import ietf-yang-types { prefix yang; } leaf trusted-ca-certificate {
type binary;
mandatory true;
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-T X.690.
organization This certificate is used by a pledge to trust a public key
"IETF ANIMA Working Group"; 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.
contact This field is optional because it may not be needed by all
"WG Web: <http://tools.ietf.org/wg/anima/> bootstrapping protocols.
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>";
description Note: the expiration date of this certificate effectively
"This module defines the format for a voucher revocation, imposes an upper limit on the voucher's expiration.";
which is produced by a manufacturer or delegate to indicate
the revocation status of vouchers.";
revision "2017-01-04" { reference
description "RFC 5280:
"Initial version"; Internet X.509 Public Key Infrastructure Certificate
reference and Certificate Revocation List (CRL) Profile.
"RFC XXXX: Voucher and Voucher Revocation Profiles ITU-T X.690:
for Bootstrapping Protocols"; Information technology - ASN.1 encoding rules:
} Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
// top-level container // DISCUSS: do we need this anymore, if short-lived vouchers
container voucher-revocation { // are expected, shouldn't the leaf certificate be pinned, or
config false; // perhaps just the immediate issuer CA?
description container domain-certificate-identifier {
"A voucher revocation that can provide revocation status must "../trusted-ca-certificate" {
information for one or more devices."; description
"A trusted-ca-certificate must be present whenever
this node is present";
}
description
"This container identifies specific values that a domain
certificate, provided to the pledge separately by the
bootstrapping protocol, MUST contain. This is useful
when, for instance, the trust anchor is a long-lived
public CA certificate, while the domain certificate is
reissued periodically.
leaf revocation-type { When provided, the pledge MUST perform RFC 6125 style
type enumeration { validation of the domain certificate against all of
enum issuer-wide { the provided values.
description
"Indicates that this revocation spans all
the vouchers the issuer has issued to date";
}
enum voucher-specific {
description
"Indicated that this revocation only regards
a single voucher.";
}
}
mandatory true;
description
"The revocation-type indicates if the revocation
is issuer-wide or voucher-specific. Both variations
exist to enable implementations to choose between the
number of revocation artifacts generated versus
individual artifact size.";
}
leaf created-on { This container is optional because it is unneeded when,
type yang:date-and-time; for instance, the trusted CA certificate is owned by the
mandatory true; domain (i.e. a private PKI), and hence the trust model
description can be more relaxed.";
"The date this voucher was created";
}
leaf expires-on { leaf subject {
type yang:date-and-time; type binary;
description description
"An optional date value for when this voucher expires."; "The certificate's entire subject field MUST match
} this value. This value is the Subject structure, as
choice voucher-revocation-type { specified by RFC ???? Section ???, encoded using the
description ASN.1 distinguished encoding rules (DER), as specified
"Identifies the revocation type as being either issuer-wide in ITU-T X.690.";
or voucher-specific."; }
leaf cn-id {
type string;
description
"The certificate's subject field's 'common name' value
MUST match this value.";
}
leaf dns-id {
type string;
description
"A subjectAltName entry of type dNSName in the
certificate MUST match this value.";
}
}
container issuer-wide { // DISCUSS: does the transition to 'pinning' model mean we can
description // drop this leaf for now? future proofing allows it to be added
"This revocation provides issuer-wide revocation status // if needed but its a edge condition?
(similar to a CRL)."; //
// DISCUSS: there must be such future proofing. not clear where
// to add it in the voucher document. This is probably the most
// important point of these discusses
leaf assert-certificate-revocations {
type boolean;
must "../expires-on";
default true;
description
"A processing instruction to the device that it should
verify revocation information for the PKIX certificates
involved in bootstrapping. This is available only if
the pledge has a real-time-clock. This is in addition
to any revocation checks performed by the MASA.";
choice list-type { // DISCUSS: should this be a boolean or an enum indicating
description // "fail open" vs "fail closed" to make the meaning clearer.
"Indentifies if this issuer-wide revocation is provided }
in the form of a whitelist or a blacklist";
container whitelist { leaf nonce {
leaf-list voucher-identifier { type binary {
type string; length "8..32";
description }
"A fingerprint over the voucher artifact."; must "not ../expires-on";
} description
description "A value that can be used by a pledge in some bootstrapping
"Indicates that the listed of vouchers are known protocols to enable anti-replay protection. This node is
to be good. If a voucher is not listed, then optional because it is not used by all bootstrapping
it is considered revoked."; protocols.
}
container blacklist { When present, the pledge MUST compare the provided nonce
leaf-list voucher-identifier { value with another value that the pledge randomly generated
type string; and sent to a bootstrap server in an earlier bootstrapping
description message. If the values do not match, then the pledge MUST
"A fingerprint over the voucher artifact. NOT process this voucher.";
Missing if list is empty."; }
}
description
"Indicates that the list of vouchers have been
revoked. If a voucher is not listed, then it
is considered good.";
}
} // end list-type leaf last-renewal-date {
type yang:date-and-time;
must "../expires-on";
description
"The last date that the MASA projects to be the last date it
will renew a voucher on (assuming the same validity duration
used in this voucher. This field is merely infomrative, it
is not processed by pledges.
} // end issuer-wide Circustances may occur after when a voucher was generated
that can 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.";
}
container voucher-specific { } // end voucher
description } // end voucher-grouping
"This revocation provides voucher-specific revocation }
status (similar to an OCSP response).";
leaf voucher-identifier { <CODE ENDS>
type string;
mandatory true;
description
"A fingerprint over the voucher artifact.";
}
leaf voucher-status { 6. Design Considerations
type enumeration {
enum good {
description
"Indicates that this voucher is valid";
}
enum revoked {
description
"Indicates that this voucher is invalid";
}
enum unknown {
description
"Indicates that the voucher's status is unknown";
}
}
mandatory true;
description
"Indicates if the revocation status for the specified
voucher.";
}
container revocation-information { 6.1. Renewals instead of Revocations
must "../voucher-status = 'revoked'";
leaf revoked-on { A revocation artifact is generally used to verify the continued
type yang:date-and-time; validity of an assertion such as a PKIX certificate, web token, or a
mandatory true; "voucher". Conceptually revocation allows for issuance of assertions
description using long lifetimes and thereby avoiding ongoing protocol operations
"The date this voucher was revoked"; to renew the assertion. In practice the use of revocation artifacts
} increases the solution complexity. Rather than a single protocol, or
operation, to obtain or renew the assertion the resulting solution
instead has two or more protocols: one for assertion maintanence and
the other(s) for revocation verification.
leaf revocation-reason { The PKIX use of CRLs and OCSP responses provides an illustrative
type enumeration { example. Relying parties that verify revocation information must
enum unspecified { obtain and parse the CRL or OCSP information. Each revocation method
description has its own validity period that effectively shortens the certificate
"Indicates that the reason the voucher validity period (since without valid revocation checks the
was revoked is unspecified."; certificate would be rejected). In addition to having multiple
} revocation protocol options the resulting space is further
enum key-compromise { complicated by inline distribution of the revocation information.
description The TLS extension "Certificate Status Request" [RFC6066] for when
"Indicates that the reason the voucher "constrained clients may wish to use a certificate-status protocol"
was revoked is because its key was is an example of this. Including revocation information into
compromised."; Cryptographic Message Syntax [RFC5652] is another example.
}
enum issuer-compromise {
description
"Indicates that the reason the voucher
was revoked is because its issuer was
compromised.";
}
enum affiliation-changed {
description
"Indicates that the reason the voucher
was revoked is because its affiliation
changed (e.g., device assigned to a
new owner.";
}
enum superseded {
description
"Indicates that the reason the voucher
was revoked is because it has been
superseded (e.g., the previous voucher
expired.";
}
enum cessation-of-operation {
description
"Indicates that the reason the voucher
was revoked is because its issuer has
ceased operations.";
}
} // end enumeration
mandatory true; If vouchers included revocation similar complexities would propagate
description to all related voucher distribution and assertion protocols. Instead
"modeled after 'CRLReason' in RFC 5280."; vouchers do not support revocation. Instead of the asserting party,
} // end revocation reason or relying party, obtaining and distributing revocation information
the asserting party MUST obtain an up-to-date valid voucher. The
protocol and operations infrastructures for this are expected to be
the same as the initial methods used to obtain a voucher in the first
place, with one important clarification: the MASA services MUST issue
updated validity period vouchers to the same Registrar ID with
minimal friction. This is similar to how an OCSP revocation system
is always willing to confirm that a certificate is not revoked.
There is no requirement implied that vouchers be contiguously
renewed. For example if a two-week lifetime voucher is not used
before it expires there is no requirement that it be still valid when
renewed. The domain MAY renew an expired voucher at any time. The
MASA always has authoritative control and MAY reject such renewals
(such as when requested by domain owner's to "block" renewals or if
the device has been successfully claimed by an alternate domain).
Allowing non-contiguous lifetimes significantly reduces the
operational load on the domain as it is not required to maintain
valid vouchers; only to ensure a valid voucher is available during
the time window in which it needs to be used.
description [[EDNOTE: It might be worth including an indication of maximum
"Provides details regarding why a voucher's revocation. lifetime for which such automated renewal is available. If so the
Modeled after 'ResponseData' in RFC6960."; language we'd use would be similar to the RFC5280 statement that
certificate validity period is "the time interval during which the CA
warrants that it will maintain information about the status of the
certificate" only here used to inform the Registrar of "the time
interval during which the MASA warrants that it will maintain
information about the status of the ownership claim". Such a field
would be independent of the actual validity period of the voucher and
is not intended for consumption by the Pledge. A suggested name for
this field would be "last-renewal-date".]]
} // end revocation-information The communications to the MASA service regarding claiming and
blocking of devices is out of scope of this specification. Similarly
if revocation methods had been described, the method of reporting a
revocation would have been out-of-scope.
} // end voucher-specific The lifetimes of vouchers may vary. In some bootstrapping protocols
} the vouchers may be ephemeral, whereas in others the vouchers may be
potentially long-lived. For bootstrapping protocols that support
ephemeral vouchers, there is no need to support renewal. For
bootstrapping protocols that support long-lived vouchers, final
protocol complexity is reduced when short lifetime vouchers are
easily renewed rather than layering on additional revocation methods.
Manufacturers MAY issue long-lived vouchers to customers if required
but no revocation method is described.
anydata additional-data { 6.2. Voucher Per Pledge
description
"Additional data signed by the manufacturer. The manufacturer
might put additional data into its voucher revocations, for
human or device consumption.";
// Ed. is the additional data normative? - if so, should we The solution originally enabled a single voucher to apply to many
// remove this free-form field, and assume it will be formally pledges, using lists of regular expressions to represent ranges of
// extended later? Note: the zerotouch draft doesn't need this serial numbers. However, it was determined that blocking the renewal
// field... of a voucher that applied to many devices, would be excessive when
} only the ownership for a single pledge needed to be blocked.
} 7. Security Considerations
}
<CODE ENDS> 7.1. Clock Sensitivity
6. Security Considerations This document defines artifacts containing time values for voucher
expirations, which require an accurate clock in order to be processed
correctly. Vendors planning on issuing vouchers with expiration
values MUST ensure 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.
6.1. Clock Sensitivity 7.2. Protect Voucher PKI in HSM
This document defines artifacts containing time values for voucher This document favors using voucher-renewals over needing to support
expirations and revocations, which require an accurate clock in order voucher-revocations (Section 6.1). However, a voucher may be signed
to be processed correctly. Implementations MUST ensure devices have by a chain of intermediate CAs leading to the trust anchor known to a
an accurate clock when shipped from manufacturing facilities, and pledge. Revocation checking of these certificates is similarly
take steps to prevent clock tampering. difficult. The current voucher format supports the existing PKIX
revocation information distribution within the limits of the current
PKI technology; but pledges MAY accept vouchers without checking
X.509 certificate revocation. Without revocation checking, a
compromized MASA keychain could be used to issue vouchers ad
infinitum without recourse. For this reason, MASA implementations
SHOULD ensure that all the CA private keys are protected by hardware
security modules (HSMs).
If it is not possible to ensure clock accuracy, it is RECOMMENDED 7.3. Test Domain Certificate Validity when Signing
that implementations disable the aspects of the solution having clock
sensitivity. In particular, such implementations should assume that
vouchers neither ever expire or are revokable.
It is important to note that implementations SHOULD NOT rely on NTP If a domain certificate is compromised, then any outstanding vouchers
for time, as it is not a secure protocol. for that domain could be used by the attacker. The domain
administrator is clearly expected to initiate revocation of any
domain identity certificates (as in normal in PKI solutions).
Similarly they are expected to contact the MASA to indicate that an
outstanding (presumably short lifetime) voucher be blocked from
automated renewal. Protocols for voucher distribution are
RECOMMENDED to check for revocation of any domain identity
certificates before automated renewal of vouchers.
7. IANA Considerations 8. IANA Considerations
7.1. The IETF XML Registry 8.1. The IETF XML Registry
This document registers two URIs in the IETF XML registry [RFC3688]. This document registers a URIs in the IETF XML registry [RFC3688].
Following the format in [RFC3688], the following registrations are Following the format in [RFC3688], the following registration is
requested: requested:
URI: urn:ietf:params:xml:ns:yang:ietf-voucher URI: urn:ietf:params:xml:ns:yang:ietf-voucher
Registrant Contact: The ANIMA WG of the IETF. Registrant Contact: The ANIMA WG of the IETF.
XML: N/A, the requested URI is an XML namespace. XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-voucher-revocation 8.2. The YANG Module Names Registry
Registrant Contact: The ANIMA WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
7.2. The YANG Module Names Registry
This document registers two YANG modules in the YANG Module Names This document registers a YANG module in the YANG Module Names
registry [RFC6020]. Following the format defined in [RFC6020], the registry [RFC6020]. Following the format defined in [RFC6020], the
the following registrations are requested: the following registration is requested:
name: ietf-voucher name: ietf-voucher
namespace: urn:ietf:params:xml:ns:yang:ietf-voucher namespace: urn:ietf:params:xml:ns:yang:ietf-voucher
prefix: vch prefix: vch
reference: RFC XXXX reference: RFC XXXX
name: ietf-voucher-revocation
namespace: urn:ietf:params:xml:ns:yang:ietf-voucher-revocation
prefix: vchr
reference: RFC XXXX
8. Acknowledgements
The authors would like to thank for following for lively discussions
on list and in the halls (ordered by last name):
9. References 9. References
9.1. Normative References 9.1. Normative References
[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>.
[RFC2315] Kaliski, B., "PKCS #7: Cryptographic Message Syntax
Version 1.5", RFC 2315, DOI 10.17487/RFC2315, March 1998,
<http://www.rfc-editor.org/info/rfc2315>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020, the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010, DOI 10.17487/RFC6020, October 2010,
<http://www.rfc-editor.org/info/rfc6020>. <http://www.rfc-editor.org/info/rfc6020>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016, RFC 7950, DOI 10.17487/RFC7950, August 2016,
<http://www.rfc-editor.org/info/rfc7950>. <http://www.rfc-editor.org/info/rfc7950>.
9.2. Informative References 9.2. Informative References
[draft-ietf-anima-bootstrapping-keyinfra] [I-D.bjorklund-netmod-yang-tree-diagrams]
Pritikin, M., Richardson, M., Behringer, M., and S. Bjorklund, M. and L. Berger, "YANG Tree Diagrams", 2017.
Bjarnason, "Bootstrapping Key Infrastructures", draft-
ietf-anima-bootstrapping-keyinfra (work in progress),
2016, <https://tools.ietf.org/html/draft-ietf-anima-
bootstrapping-keyinfra>.
[draft-ietf-netconf-zerotouch] [I-D.ietf-6tisch-dtsecurity-secure-join]
Richardson, M., "6tisch Secure Join protocol", draft-ietf-
6tisch-dtsecurity-secure-join-01 (work in progress),
February 2017.
[I-D.ietf-anima-bootstrapping-keyinfra]
Pritikin, M., Richardson, M., Behringer, M., Bjarnason,
S., and K. Watsen, "Bootstrapping Remote Secure Key
Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping-
keyinfra-04 (work in progress), October 2016.
[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 (work in progress), 2016, netconf-zerotouch-12 (work in progress), January 2017.
<https://tools.ietf.org/html/draft-ietf-netconf-
zerotouch>. [imprinting]
Wikipedia, , "Wikipedia article: Imprinting", July 2015,
<https://en.wikipedia.org/wiki/Imprinting_(psychology)>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004, DOI 10.17487/RFC3688, January 2004,
<http://www.rfc-editor.org/info/rfc3688>. <http://www.rfc-editor.org/info/rfc3688>.
Appendix A. Change Log [RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection
Most of the Time", RFC 7435, DOI 10.17487/RFC7435,
December 2014, <http://www.rfc-editor.org/info/rfc7435>.
[Stajano99theresurrecting]
Stajano, F. and R. Anderson, "The resurrecting duckling:
security issues for ad-hoc wireless networks", 1999,
<https://www.cl.cam.ac.uk/~fms27/papers/1999-StajanoAnd-
duckling.pdf>.
Appendix A. Acknowledgements
The authors would like to thank for following for lively discussions
on list and in the halls (ordered by last name):
Authors' Addresses Authors' Addresses
Kent Watsen Kent Watsen
Juniper Networks Juniper Networks
EMail: kwatsen@juniper.net EMail: kwatsen@juniper.net
Michael C. Richardson Michael C. Richardson
Sandelman Software Works Sandelman Software
EMail: mcr+ietf@sandelman.ca EMail: mcr+ietf@sandelman.ca
URI: http://www.sandelman.ca/ URI: http://www.sandelman.ca/
Max Pritikin Max Pritikin
Cisco Systems Cisco Systems
EMail: pritikin@cisco.com EMail: pritikin@cisco.com
Toerless Eckert Toerless Eckert
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