NETCONF Working Group K. Watsen
Internet-Draft Juniper Networks
Intended status: Standards Track M. Abrahamsson
Expires: September 6, 2018 T-Systems
I. Farrer
Deutsche Telekom AG
March 5, 2018
Zero Touch Provisioning for Networking Devices
draft-ietf-netconf-zerotouch-21
Abstract
This draft presents a technique to securely provision a networking
device when it is booting in a factory-default state. Variations in
the solution enables it to be used on both public and private
networks. The provisioning steps are able to update the boot image,
commit an initial configuration, and execute arbitrary scripts to
address auxiliary needs. The updated device is subsequently able to
establish secure connections with other systems. For instance, a
device may establish NETCONF [RFC6241] and/or RESTCONF [RFC8040]
connections with deployment-specific network management systems.
Editorial Note (To be removed by RFC Editor)
This draft contains many placeholder values that need to be replaced
with finalized values at the time of publication. This note
summarizes all of the substitutions that are needed. No other RFC
Editor instructions are specified elsewhere in this document.
Artwork in the IANA Considerations section contains placeholder
values for DHCP options pending IANA assignment. Please apply the
following replacements:
o "TBD1" --> the assigned value for id-ct-zerotouchInformationXML
o "TBD2" --> the assigned value for id-ct-zerotouchInformationJSON
Artwork in this document contains shorthand references to drafts in
progress. Please apply the following replacements:
o "XXXX" --> the assigned numerical RFC value for this draft
o "ZZZZ" --> the assigned numerical RFC value for
[I-D.ietf-anima-voucher]
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Artwork in this document contains placeholder values for the date of
publication of this draft. Please apply the following replacement:
o "2018-03-05" --> the publication date of this draft
Please update the following informative references to reflect its
final RFC assignment:
o I-D.ietf-netmod-yang-tree-diagrams
The following one Appendix section is to be removed prior to
publication:
o Appendix A. Change Log
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
working documents as Internet-Drafts. The list of current Internet-
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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 September 6, 2018.
Copyright Notice
Copyright (c) 2018 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 7
1.4. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 8
2. Types of Bootstrapping Information . . . . . . . . . . . . . 8
2.1. Redirect Information . . . . . . . . . . . . . . . . . . 8
2.2. Onboarding Information . . . . . . . . . . . . . . . . . 9
3. Artifacts . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1. Zero Touch Information . . . . . . . . . . . . . . . . . 10
3.2. Owner Certificate . . . . . . . . . . . . . . . . . . . . 11
3.3. Ownership Voucher . . . . . . . . . . . . . . . . . . . . 12
3.4. Artifact Encryption . . . . . . . . . . . . . . . . . . . 12
3.5. Artifact Groupings . . . . . . . . . . . . . . . . . . . 13
4. Sources of Bootstrapping Data . . . . . . . . . . . . . . . . 14
4.1. Removable Storage . . . . . . . . . . . . . . . . . . . . 14
4.2. DNS Server . . . . . . . . . . . . . . . . . . . . . . . 15
4.3. DHCP Server . . . . . . . . . . . . . . . . . . . . . . . 16
4.4. Bootstrap Server . . . . . . . . . . . . . . . . . . . . 17
5. Device Details . . . . . . . . . . . . . . . . . . . . . . . 18
5.1. Initial State . . . . . . . . . . . . . . . . . . . . . . 18
5.2. Boot Sequence . . . . . . . . . . . . . . . . . . . . . . 20
5.3. Processing a Source of Bootstrapping Data . . . . . . . . 21
5.4. Validating Signed Data . . . . . . . . . . . . . . . . . 23
5.5. Processing Redirect Information . . . . . . . . . . . . . 24
5.6. Processing Onboarding Information . . . . . . . . . . . . 25
6. The Zero Touch Information Data Model . . . . . . . . . . . . 26
6.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 27
6.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 27
6.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 29
7. The Zero Touch Bootstrap Server API . . . . . . . . . . . . . 35
7.1. API Overview . . . . . . . . . . . . . . . . . . . . . . 35
7.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 36
7.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 39
8. The Zero Touch Device Data Model . . . . . . . . . . . . . . 48
8.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 48
8.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 49
8.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 49
9. DHCP Zero Touch Options . . . . . . . . . . . . . . . . . . . 53
9.1. DHCPv4 Zero Touch Option . . . . . . . . . . . . . . . . 53
9.2. DHCPv6 Zero Touch Option . . . . . . . . . . . . . . . . 55
9.3. Common Field Encoding . . . . . . . . . . . . . . . . . . 56
10. Security Considerations . . . . . . . . . . . . . . . . . . . 56
10.1. Immutable Storage for Trust Anchors . . . . . . . . . . 56
10.2. Secure Storage for Long-lived Private Keys . . . . . . . 56
10.3. Use of IDevID Certificates . . . . . . . . . . . . . . . 57
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10.4. Clock Sensitivity . . . . . . . . . . . . . . . . . . . 57
10.5. Blindly authenticating a bootstrap server . . . . . . . 57
10.6. Disclosing Information to Untrusted Servers . . . . . . 57
10.7. Sequencing Sources of Bootstrapping Data . . . . . . . . 58
10.8. The "ietf-zerotouch-information" YANG Module . . . . . . 58
10.9. The "ietf-zerotouch-bootstrap-server" YANG Module . . . 59
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 60
11.1. The IETF XML Registry . . . . . . . . . . . . . . . . . 60
11.2. The YANG Module Names Registry . . . . . . . . . . . . . 60
11.3. The SMI Security for S/MIME CMS Content Type Registry . 60
11.4. The BOOTP Manufacturer Extensions and DHCP Options
Registry . . . . . . . . . . . . . . . . . . . . . . . . 61
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 61
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 61
13.1. Normative References . . . . . . . . . . . . . . . . . . 61
13.2. Informative References . . . . . . . . . . . . . . . . . 63
Appendix A. Promoting a Connection from Untrusted to Trusted . . 65
Appendix B. Workflow Overview . . . . . . . . . . . . . . . . . 66
B.1. Enrollment and Ordering Devices . . . . . . . . . . . . . 66
B.2. Owner Stages the Network for Bootstrap . . . . . . . . . 68
B.3. Device Powers On . . . . . . . . . . . . . . . . . . . . 71
Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 73
C.1. ID to 00 . . . . . . . . . . . . . . . . . . . . . . . . 73
C.2. 00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . 73
C.3. 01 to 02 . . . . . . . . . . . . . . . . . . . . . . . . 74
C.4. 02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . 74
C.5. 03 to 04 . . . . . . . . . . . . . . . . . . . . . . . . 74
C.6. 04 to 05 . . . . . . . . . . . . . . . . . . . . . . . . 74
C.7. 05 to 06 . . . . . . . . . . . . . . . . . . . . . . . . 75
C.8. 06 to 07 . . . . . . . . . . . . . . . . . . . . . . . . 75
C.9. 07 to 08 . . . . . . . . . . . . . . . . . . . . . . . . 75
C.10. 08 to 09 . . . . . . . . . . . . . . . . . . . . . . . . 75
C.11. 09 to 10 . . . . . . . . . . . . . . . . . . . . . . . . 75
C.12. 10 to 11 . . . . . . . . . . . . . . . . . . . . . . . . 76
C.13. 11 to 12 . . . . . . . . . . . . . . . . . . . . . . . . 76
C.14. 12 to 13 . . . . . . . . . . . . . . . . . . . . . . . . 77
C.15. 13 to 14 . . . . . . . . . . . . . . . . . . . . . . . . 77
C.16. 14 to 15 . . . . . . . . . . . . . . . . . . . . . . . . 77
C.17. 15 to 16 . . . . . . . . . . . . . . . . . . . . . . . . 78
C.18. 16 to 17 . . . . . . . . . . . . . . . . . . . . . . . . 78
C.19. 17 to 18 . . . . . . . . . . . . . . . . . . . . . . . . 79
C.20. 18 to 19 . . . . . . . . . . . . . . . . . . . . . . . . 79
C.21. 19 to 20 . . . . . . . . . . . . . . . . . . . . . . . . 79
C.22. 20 to 21 . . . . . . . . . . . . . . . . . . . . . . . . 80
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 80
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1. Introduction
A fundamental business requirement for any network operator is to
reduce costs where possible. For network operators, deploying
devices to many locations can be a significant cost, as sending
trained specialists to each site for installations is both cost
prohibitive and does not scale.
This document defines Secure Zero Touch Provisioning (SZTP), a
bootstrapping strategy enabling devices to securely obtain
bootstrapping data with no installer action beyond physical placement
and connecting network and power cables. As such, SZTP enables non-
technical personnel to bring up devices in remote locations without
the need for any operator input.
The SZTP solution includes updating the boot image, committing an
initial configuration, and executing arbitrary scripts to address
auxiliary needs. The updated device is subsequently able to
establish secure connections with other systems. For instance, a
devices may establish NETCONF [RFC8040] and/or RESTCONF [RFC6241]
connections with deployment-specific network management systems.
This document primarily regards physical devices, where the setting
of the device's initial state, described in Section 5.1, occurs
during the device's manufacturing process. The SZTP solution may be
extended to support virtual machines or other such logical
constructs, but details for how this can be accomplished is left for
future work.
1.1. Use Cases
o Device connecting to a remotely administered network
This use-case involves scenarios, such as a remote branch
office or convenience store, whereby a device connects as an
access gateway to an ISP's network. Assuming it is not
possible to customize the ISP's network to provide any
bootstrapping support, and with no other nearby device to
leverage, the device has no recourse but to reach out to an
Internet-based bootstrap server to bootstrap from.
o Device connecting to a locally administered network
This use-case covers all other scenarios and differs only in
that the device may additionally leverage nearby devices, which
may direct it to use a local service to bootstrap from. If no
such information is available, or the device is unable to use
the information provided, it can then reach out to the network
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just as it would for the remotely administered network use-
case.
Conceptual workflows for how SZTP might be deployed are provided in
Appendix B.
1.2. Terminology
This document uses the following terms (sorted by name):
Artifact: The term "artifact" is used throughout to represent any of
the three artifacts defined in Section 3 (zero touch information,
ownership voucher, and owner certificate). These artifacts
collectively provide all the bootstrapping data a device may use.
Bootstrapping Data: The term "bootstrapping data" is used throughout
this document to refer to the collection of data that a device
may obtain during the bootstrapping process. Specifically, it
refers to the three artifacts zero touch information, owner
certificate, and ownership voucher, as described in Section 3.
Bootstrap Server: The term "bootstrap server" is used within this
document to mean any RESTCONF server implementing the YANG module
defined in Section 7.3.
Device: The term "device" is used throughout this document to refer
to a network element that needs to be bootstrapped. See
Section 5 for more information about devices.
Manufacturer: The term "manufacturer" is used herein to refer to the
manufacturer of a device or a delegate of the manufacturer.
Network Management System (NMS): The acronym "NMS" is used
throughout this document to refer to the deployment specific
management system that the bootstrapping process is responsible
for introducing devices to. From a device's perspective, when
the bootstrapping process has completed, the NMS is a NETCONF or
RESTCONF client.
Onboarding Information: The term "onboarding information" is used
herein to refer to one of the two types of "zero touch
information" defined in this document, the other being "redirect
information". Onboarding information is formally defined by the
"onboarding-information" YANG-data structure in Section 6.3.
Onboarding Server: The term "onboarding server" is used herein to
refer to a bootstrap server that only returns onboarding
information.
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Owner: The term "owner" is used throughout this document to refer to
the person or organization that purchased or otherwise owns a
device.
Owner Certificate: The term "owner certificate" is used in this
document to represent an X.509 certificate that binds an owner
identity to a public key, which a device can use to validate a
signature over the zero touch information artifact. The owner
certificate may be communicated along with its chain of
intermediate certificates leading up to a known trust anchor.
The owner certificate is one of the three bootstrapping artifacts
described in Section 3.
Ownership Voucher: The term "ownership voucher" is used in this
document to represent the voucher artifact defined in
[I-D.ietf-anima-voucher]. The ownership voucher is used to
assign a device to an owner. The ownership voucher is one of the
three bootstrapping artifacts described in Section 3.
Redirect Information: The term "redirect information" is used herein
to refer to one of the two types of "zero touch information"
defined in this document, the other being "onboarding
information". Redirect information is formally defined by the
"redirect-information" YANG-data structure in Section 6.3.
Redirect Server: The term "redirect server" is used to refer to a
bootstrap server that only returns redirect information. A
redirect server is particularly useful when hosted by a
manufacturer, as a well-known (e.g., Internet-based) resource to
redirect devices to deployment-specific bootstrap servers.
Signed Data: The term "signed data" is used throughout to mean zero
touch information that has been signed, specifically by a private
key possessed by a device's owner.
Unsigned Data: The term "unsigned data" is used throughout to mean
zero touch information that has not been signed.
Zero Touch Information: The term "zero touch information" is used
herein to refer either redirect information or onboarding
information. Zero touch information is one of the three
bootstrapping artifacts described in Section 3.
1.3. 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
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14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.4. Tree Diagrams
Tree diagrams used in this document follow the notation defined in
[I-D.ietf-netmod-yang-tree-diagrams].
2. Types of Bootstrapping Information
This document defines two types of information that devices can
access during the bootstrapping process. These information types are
described in this section. Examples are provided in Section 6.2
2.1. Redirect Information
Redirect information redirects a device to another bootstrap server.
Redirect information encodes a list of bootstrap servers, each
specifying the bootstrap server's hostname (or IP address), an
optional port, and an optional trust anchor certificate that the
device can use to authenticate the bootstrap server with.
Redirect information is YANG modeled data formally defined by the
"redirect-information" container in the YANG module presented in
Section 6.3. This container has the tree diagram shown below.
+--:(redirect-information)
+---- redirect-information
+---- bootstrap-server* [address]
+---- address inet:host
+---- port? inet:port-number
+---- trust-anchor? cms
Redirect information may be trusted or untrusted. The redirect
information is trusted whenever it is obtained via a secure
connection to a trusted bootstrap server, or whenever it is signed by
the device's owner. In all other cases, the redirect information is
untrusted.
Trusted redirect information is useful for enabling a device to
establish a secure connection to a specified bootstrap server, which
is possible when the redirect information includes the bootstrap
server's trust anchor certificate.
Untrusted redirect information is useful for directing a device to a
bootstrap server where signed data has been staged for it to obtain.
Note that, when the redirect information is untrusted, devices
discard any potentially included trust anchor certificates.
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How devices process redirect information is described in Section 5.5.
2.2. Onboarding Information
Onboarding information provides data necessary for a device to
bootstrap itself and establish secure connections with other systems.
As defined in this document, onboarding information can specify
details about the boot image a device must be running, specify an
initial configuration the device must commit, and specify scripts
that the device must successfully execute.
Onboarding information is YANG modeled data formally defined by the
"onboarding-information" container in the YANG module presented in
Section 6.3. This container has the tree diagram shown below.
+--:(onboarding-information)
+---- onboarding-information
+---- boot-image
| +---- os-name? string
| +---- os-version? string
| +---- download-uri* inet:uri
| +---- image-verification* [hash-algorithm]
| +---- hash-algorithm identityref
| +---- hash-value yang:hex-string
+---- configuration-handling? enumeration
+---- pre-configuration-script? script
+---- configuration? binary
+---- post-configuration-script? script
Onboarding information must be trusted for it to be of any use to a
device. There is no option for a device to process untrusted
onboarding information.
Onboarding information is trusted whenever it is obtained via a
secure connection to a trusted bootstrap server, or whenever it is
signed by the device's owner. In all other cases, the onboarding
information is untrusted.
How devices process onboarding information is described in
Section 5.6.
3. Artifacts
This document defines three artifacts that can be made available to
devices while they are bootstrapping. Each source of bootstrapping
information specifies how it provides the artifacts defined in this
section (see Section 4).
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3.1. Zero Touch Information
The zero touch information artifact encodes the essential
bootstrapping data for the device. This artifact is used to encode
the redirect information and onboarding information types discussed
in Section 2.
The zero touch information artifact is a CMS structure, as described
in [RFC5652], encoded using ASN.1 distinguished encoding rules (DER),
as specified in ITU-T X.690 [ITU.X690.1994]. The CMS structure MUST
contain content conforming to the YANG module specified in
Section 6.3.
The zero touch information CMS structure may encode signed or
unsigned bootstrapping data. When the bootstrapping data is signed,
it may also be encrypted but, from a terminology perspective, it is
still "signed data" Section 1.2.
When the zero touch information artifact is unsigned, as it might be
when communicated over trusted channels, the CMS structure's top-most
content type MUST be one of the OIDs described in Section 11.3, or
the OID id_data (1.2.840.113549.1.7.1), in which case the encoding
(JSON, XML, etc.) SHOULD be communicated externally. In either
case, the associated content is an octet string containing
'zerotouch-information' data in the expected encoding.
When the zero touch information artifact is signed, as it might be
when communicated over untrusted channels, the CMS structure's top-
most content type MUST be the OID id-signedData
(1.2.840.113549.1.7.2), and its inner eContentType MUST be one of the
OIDs described in Section 11.3, or the OID id_data
(1.2.840.113549.1.7.1), in which case the encoding (JSON, XML, etc.)
SHOULD be communicated externally. In either case, the associated
content or eContent is an octet string containing 'zerotouch-
information' data in the expected encoding.
When the zero touch information artifact is signed and encrypted, as
it might be when communicated over untrusted channels and privacy is
important, the CMS's structure's top-most content type MUST be the
OID id-envelopedData (1.2.840.113549.1.7.3), and the
encryptedContentInfo's content type MUST be the OID id-signedData
(1.2.840.113549.1.7.2), whose eContentType MUST be one of the OIDs
described in Section 11.3, or the OID id_data (1.2.840.113549.1.7.1),
in which case the encoding (JSON, XML, etc.) SHOULD be communicated
externally. In either case, the associated content or eContent is an
octet string containing 'zerotouch-information' data in the expected
encoding.
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3.2. Owner Certificate
The owner certificate artifact is an X.509 certificate [RFC5280] that
is used to identify an "owner" (e.g., an organization). The owner
certificate can be signed by any certificate authority (CA). The
owner certificate either MUST have no Key Usage specified or the Key
Usage MUST at least set the "digitalSignature" bit. The values for
the owner certificate's "subject" and/or "subjectAltName" are not
constrained by this document.
The owner certificate is used by a device to verify the signature
over the zero touch information artifact (Section 3.1) that the
device should have also received, as described in Section 3.5. In
particular, the device verifies the signature using the public key in
the owner certificate over the content contained within the zero
touch information artifact.
The owner certificate artifact is formally a CMS structure, as
specified by [RFC5652], encoded using ASN.1 distinguished encoding
rules (DER), as specified in ITU-T X.690 [ITU.X690.1994].
The owner certificate CMS structure MUST contain the owner
certificate itself, as well as all intermediate certificates leading
to the 'pinned-domain-cert' certificate specified in the ownership
voucher. The owner certificate artifact MAY optionally include the
'pinned-domain-cert' as well.
In order to support devices deployed on private networks, the owner
certificate CMS structure MAY also contain suitably fresh, as
determined by local policy, revocation objects (e.g., CRLs). Having
these revocation objects stapled to the owner certificate may obviate
the need for the device to have to download them dynamically using
the CRL distribution point or an OCSP responder specified in the
associated certificates.
When unencrypted, the owner certificate artifact's CMS structure's
top-most content type MUST be the OID id-signedData
(1.2.840.113549.1.7.2). The inner SignedData structure is the
degenerate form, whereby there are no signers, that is commonly used
to disseminate certificates and revocation objects.
When encrypted, the owner certificate artifact's CMS structure's top-
most content type MUST be the OID id-envelopedData
(1.2.840.113549.1.7.3), and the encryptedContentInfo's content type
MUST be the OID id-signedData (1.2.840.113549.1.7.2), whereby the
inner SignedData structure is the degenerate form that has no signers
commonly used to disseminate certificates and revocation objects.
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3.3. Ownership Voucher
The ownership voucher artifact is used to securely identify a
device's owner, as it is known to the manufacturer. The ownership
voucher is signed by the device's manufacturer.
The ownership voucher is used to verify the owner certificate
(Section 3.2) that the device should have also received, as described
in Section 3.5. In particular, the device verifies that the owner
certificate has a chain of trust leading to the trusted certificate
included in the ownership voucher ('pinned-domain-cert'). Note that
this relationship holds even when the owner certificate is a self-
signed certificate, and hence also the pinned-domain-cert.
When unencrypted, the ownership voucher artifact is as defined in
[I-D.ietf-anima-voucher]. As described, it is a CMS structure whose
top-most content type MUST be the OID id-signedData
(1.2.840.113549.1.7.2), whose eContentType MUST be OID id-ct-
animaJSONVoucher (1.2.840.113549.1.9.16.1), or the OID id_data
(1.2.840.113549.1.7.1), in which case the encoding (JSON, XML, etc.)
SHOULD be communicated externally. In either case, the associated
content is an octet string containing ietf-voucher data in the
expected encoding.
When encrypted, the ownership voucher artifact's CMS structure's top-
most content type MUST be the OID id-envelopedData
(1.2.840.113549.1.7.3), and the encryptedContentInfo's content type
MUST be the OID id-signedData (1.2.840.113549.1.7.2), whose
eContentType MUST be OID id-ct-animaJSONVoucher
(1.2.840.113549.1.9.16.1), or the OID id_data (1.2.840.113549.1.7.1),
in which case the encoding (JSON, XML, etc.) SHOULD be communicated
externally. In either case, the associated content is an octet
string containing ietf-voucher data in the expected encoding.
3.4. Artifact Encryption
Each of the three artifacts MAY be individually encrypted.
Encryption may be important in some environments where the content is
considered sensitive.
Each of the three artifacts are encrypted in the same way, by the
unencrypted form being encapsulated inside a CMS EnvelopedData type.
As a consequence, both the zerotouch-information and ownership
voucher artifacts are signed and then encrypted, never encrypted and
then signed.
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This sequencing has the advantage of shrouding the signer's
certificate, and ensuring that the owner knows the content being
signed. This sequencing further enables the owner to inspect an
unencrypted voucher obtained from a manufacturer and then encrypt the
voucher later themselves, perhaps while also stapling in current
revocation objects, when ready to place the artifact in an unsafe
location.
When encrypted, the CMS MUST be encrypted using a secure device
identity certificate for the device. This certificate MAY be the
same as the TLS-level client certificate the device uses when
connecting to bootstrap servers. The owner must possess the device's
identity certificate at the time of encrypting the data. How the
owner comes to posses the device's identity certificate for this
purpose is outside the scope of this document.
3.5. Artifact Groupings
The previous sections discussed the bootstrapping artifacts, but only
certain groupings of these artifacts make sense to return in the
various bootstrapping situations described in this document. These
groupings are:
Unsigned Information: This grouping is useful for cases when
transport level security can be used to convey trust (e.g.,
HTTPS), or when the information can be processed in a
provisional manner (i.e. unsigned redirect information).
Signed Information, without revocations: This grouping is useful
when signed information is needed, because it is obtained from
an untrusted source, and it cannot be processed provisionally,
and yet either revocations are not needed or they can be
obtained dynamically.
Signed Information, with revocations: This grouping is useful
when signed information is needed, because it is obtained from
an untrusted source, and it cannot be processed provisionally,
and revocations are needed and cannot be obtained dynamically.
The artifacts associated with these groupings are described below:
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Zero Touch Ownership Owner
Grouping Information Voucher Certificate
-------------------- ------------- ------------ -----------
Unsigned Information Yes, no sig No No
Signed Information, Yes, with sig Yes, without Yes, without
without revocations revocations revocations
Signed Information, Yes, with sig Yes, with Yes, with
with revocations revocations revocations
4. Sources of Bootstrapping Data
This section defines some sources for bootstrapping data that a
device can access. The list of sources defined here is not meant to
be exhaustive. It is left to future documents to define additional
sources for obtaining bootstrapping data.
For each source of bootstrapping data defined in this section,
details are given for how the three artifacts listed in Section 3 are
provided.
4.1. Removable Storage
A directly attached removable storage device (e.g., a USB flash
drive) MAY be used as a source of zero touch bootstrapping data.
Use of a removable storage device is compelling, as it does not
require any external infrastructure to work. It is notable that the
raw boot image file can also be located on the removable storage
device, enabling a removable storage device to be a fully self-
standing bootstrapping solution.
To use a removable storage device as a source of bootstrapping data,
a device need only detect if the removable storage device is plugged
in and mount its filesystem.
A removable storage device is an untrusted source of bootstrapping
data. This means that the information stored on the removable
storage device either MUST be signed or MUST be information that can
be processed provisionally (e.g., unsigned redirect information).
From an artifact perspective, since a removable storage device
presents itself as a filesystem, the bootstrapping artifacts need to
be presented as files. The three artifacts defined in Section 3 are
mapped to files below.
Artifact to File Mapping:
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Zero Touch Information: Mapped to a file containing the binary
artifact described in Section 3.1 (e.g., zerotouch-
information.cms).
Owner Certificate: Mapped to a file containing the binary
artifact described in Section 3.2 (e.g., owner-
certificate.cms).
Ownership Voucher: Mapped to a file containing the binary
artifact described in Section 3.3 (e.g., ownership-voucher.cms
or ownership-voucher.vcj).
The format of the removable storage device's filesystem and the
naming of the files are outside the scope of this document. However,
in order to facilitate interoperability, it is RECOMMENDED devices
support open and/or standards based filesystems. It is also
RECOMMENDED that devices assume a file naming convention that enables
more than one instance of bootstrapping data (i.e., for different
devices) to exist on a removable storage device. The file naming
convention SHOULD additionally be unique to the manufacturer, in
order to enable bootstrapping data from multiple manufacturers to
exist on a removable storage device.
4.2. DNS Server
A DNS server MAY be used as a source of zero touch bootstrapping
data.
Using a DNS server may be a compelling option for deployments having
existing DNS infrastructure, as it enables a touchless bootstrapping
option that does not entail utilizing an Internet based resource
hosted by a 3rd-party.
To use a DNS server as a source of bootstrapping data, a device MAY
perform a multicast DNS [RFC6762] query searching for the service
"_zerotouch._tcp.local.". Alternatively the device MAY perform DNS-
SD [RFC6763] via normal DNS operation, using the domain returned to
it from the DHCP server; for example, searching for the service
"_zerotouch._tcp.example.com".
Unsigned DNS records (e.g., not using DNSSEC as described in
[RFC6698]) are an untrusted source of bootstrapping data. This means
that the information stored in the DNS records either MUST be signed,
or MUST be information that can be processed provisionally (e.g.,
unsigned redirect information).
From an artifact perspective, since a DNS server presents resource
records (Section 3.2.1 of [RFC1035]), the bootstrapping artifacts
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need to be presented as resource records. The three artifacts
defined in Section 3 are mapped to resource records below.
Artifact to Resource Record Mapping:
Zero Touch Information: Mapped to a TXT record called "zt-info"
containing the base64-encoding of the binary artifact described
in Section 3.1.
Owner Certificate: Mapped to a TXT record called "zt-cert"
containing the base64-encoding of the binary artifact described
in Section 3.2.
Ownership Voucher: Mapped to a TXT record called "zt-voucher"
containing the base64-encoding of the binary artifact described
in Section 3.3.
TXT records have an upper size limit of 65535 bytes (Section 3.2.1 in
RFC1035), since "RDLENGTH" is a 16-bit field. Please see
Section 3.1.3 in RFC4408 for how a TXT record can achieve this size.
Due to this size limitation, some zero touch information artifacts
may not fit. In particular, onboarding information could hit this
upper bound, depending on the size of the included configuration and
scripts.
4.3. DHCP Server
A DHCP server MAY be used as a source of zero touch bootstrapping
data.
Using a DHCP server may be a compelling option for deployments having
existing DHCP infrastructure, as it enables a touchless bootstrapping
option that does not entail utilizing an Internet based resource
hosted by a 3rd-party.
A DHCP server is an untrusted source of bootstrapping data. Thus the
information stored on the DHCP server either MUST be signed, or it
MUST be information that can be processed provisionally (e.g.,
unsigned redirect information).
However, unlike other sources of bootstrapping data described in this
document, the DHCP protocol (especially DHCP for IPv4) is very
limited in the amount of data that can be conveyed, to the extent
that signed data cannot be communicated. This means that only
unsigned redirect information can be conveyed via DHCP.
Since the redirect information is unsigned, it SHOULD NOT include the
optional trust anchor certificate, as it takes up space in the DHCP
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message, and the device would have to discard it anyway. For this
reason, the DHCP options defined in Section 9 do not enable the trust
anchor certificate to be encoded.
From an artifact perspective, the three artifacts defined in
Section 3 are mapped to the DHCP fields specified in Section 9 as
follows:
Zero Touch Information: This artifact is not supported directly.
Instead, the essence of unsigned redirect information is mapped
to the DHCP options described in Section 9.
Owner Certificate: Not supported. There is not enough space in
the DHCP packet to hold an owner certificate artifact.
Ownership Voucher: Not supported. There is not enough space in
the DHCP packet to hold an ownership voucher artifact.
4.4. Bootstrap Server
A bootstrap server MAY be used as a source of zero touch
bootstrapping data. A bootstrap server is defined as a RESTCONF
[RFC8040] server implementing the YANG module provided in Section 7.
Using a bootstrap server as a source of bootstrapping data is a
compelling option as it MAY use transport-level security, obviating
the need for signed data, which may be easier to deploy in some
situations.
Unlike any other source of bootstrapping data described in this
document, a bootstrap server is not only a source of data, but it can
also receive data from devices using the YANG-defined 'report-
progress' RPC defined in the YANG module (Section 7.3). The 'report-
progress' RPC enables visibility into the bootstrapping process
(e.g., warnings and errors), and provides potentially useful
information upon completion (e.g., the device's SSH host-keys).
A bootstrap server may be a trusted or an untrusted source of
bootstrapping data, depending on if the device learned about the
bootstrap server's trust anchor from a trusted source. When a
bootstrap server is trusted, the information returned from it MAY be
signed. However, when the server is untrusted, in order for its
information to be of any use to the device, the bootstrap information
either MUST be signed or MUST be information that can be processed
provisionally (e.g., unsigned redirect information).
From an artifact perspective, since a bootstrap server presents data
conforming to a YANG data model, the bootstrapping artifacts need to
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be mapped to YANG nodes. The three artifacts defined in Section 3
are mapped to 'output' nodes of the 'get-bootstrapping-data' RPC
defined in Section 7.3 below.
Artifact to Bootstrap Server Mapping:
Zero Touch Information: Mapped to the 'zerotouch-information'
leaf in the output of the 'get-bootstrapping-data' RPC.
Owner Certificate: Mapped to the 'owner-certificate' leaf in the
output of the 'get-bootstrapping-data' RPC.
Ownership Voucher: Mapped to the 'ownership-voucher' leaf in the
output of the 'get-bootstrapping-data' RPC.
Zero touch bootstrap servers have only two endpoints, one for the
'get-bootstrapping-data' RPC and one for the 'report-progress' RPC.
These RPCs use the authenticated RESTCONF username to isolate the
execution of the RPC from other devices.
5. Device Details
Devices supporting the bootstrapping strategy described in this
document MUST have the preconfigured state and bootstrapping logic
described in the following sections.
5.1. Initial State
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+-------------------------------------------------------------+
| <device> |
| |
| +---------------------------------------------------------+ |
| | <read/write storage> | |
| | | |
| | 1. flag to enable zerotouch bootstrapping set to "true" | |
| +---------------------------------------------------------+ |
| |
| +---------------------------------------------------------+ |
| | <read-only storage> | |
| | | |
| | 2. TLS client cert & related intermediate certificates | |
| | 3. list of trusted well-known bootstrap servers | |
| | 4. list of trust anchor certs for bootstrap servers | |
| | 5. list of trust anchor certs for ownership vouchers | |
| +---------------------------------------------------------+ |
| |
| +-----------------------------------------------------+ |
| | <secure storage> | |
| | | |
| | 6. private key for TLS client certificate | |
| | 7. private key for decrypting zerotouch artifacts | |
| +-----------------------------------------------------+ |
| |
+-------------------------------------------------------------+
Each numbered item below corresponds to a numbered item in the
diagram above.
1. Devices MUST have a configurable variable that is used to enable/
disable zerotouch bootstrapping. This variable MUST be enabled
by default in order for zerotouch bootstrapping to run when the
device first powers on. Because it is a goal that the
configuration installed by the bootstrapping process disables
zerotouch bootstrapping, and because the configuration may be
merged into the existing configuration, using a configuration
node that relies on presence is NOT RECOMMENDED, as it cannot be
removed by the merging process.
2. Devices that support loading bootstrapping data from bootstrap
servers (see Section 4.4) SHOULD possess a TLS-level client
certificate and any intermediate certificates leading to the
certificate's well-known trust-anchor. The well-known trust
anchor certificate may be an intermediate certificate or a self-
signed root certificate. To support devices not having a client
certificate, devices MAY, alternatively or in addition to,
identify and authenticate themselves to the bootstrap server
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using an HTTP authentication scheme, as allowed by Section 2.5 in
[RFC8040]; however, this document does not define a mechanism for
operator input enabling, for example, the entering of a password.
3. Devices that support loading bootstrapping data from well-known
bootstrap servers MUST possess a list of the well-known bootstrap
servers. Consistent with redirect information (Section 2.1, each
bootstrap server can be identified by its hostname or IP address,
and an optional port.
4. Devices that support loading bootstrapping data from well-known
bootstrap servers MUST also possess a list of trust anchor
certificates that can be used to authenticate the well-known
bootstrap servers. For each trust anchor certificate, if it is
not itself a self-signed root certificate, the device SHOULD also
possess the chain of intermediate certificates leading up to and
including the self-signed root certificate.
5. Devices that support loading signed data (see Section 1.2) MUST
possess the trust anchor certificates for validating ownership
vouchers. For each trust anchor certificate, if it is not itself
a self-signed root certificate, the device SHOULD also possess
the chain of intermediate certificates leading up to and
including the self-signed root certificate.
6. Devices that support using a TLS-level client certificate to
identify and authenticate themselves to a bootstrap server MUST
possess the private key that corresponds to the public key
encoded in the TLS-level client certificate. This private key
SHOULD be securely stored, ideally in a cryptographic processor
(e.g., a TPM).
7. Devices that support decrypting zerotouch artifacts MUST posses
the private key that corresponds to the public key encoded in the
secure device identity certificate used when encrypting the
artifacts. This private key SHOULD be securely stored, ideally
in a cryptographic processor (e.g., a TPM). This private key MAY
be the same as the one associated to the TLS-level client
certificate used when connecting to bootstrap servers.
A YANG module representing this data is provided in Section 8.
5.2. Boot Sequence
A device claiming to support the bootstrapping strategy defined in
this document MUST support the boot sequence described in this
section.
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Power On
|
v No
1. Zerotouch bootstrapping configured ------> Boot normally
|
| Yes
v
2. For each supported source of bootstrapping data,
try to load bootstrapping data from the source
|
|
v Yes
3. Able to bootstrap from any source? -----> Run with new config
|
| No
v
4. Loop and/or wait for manual provisioning.
Each numbered item below corresponds to a numbered item in the
diagram above.
1. When the device powers on, it first checks to see if zerotouch
bootstrapping is configured, as is expected to be the case for
the device's preconfigured initial state. If zerotouch
bootstrapping is not configured, then the device boots normally.
2. The device iterates over its list of sources for bootstrapping
data (Section 4). Details for how to processes a source of
bootstrapping data are provided in Section 5.3.
3. If the device is able to bootstrap itself from any of the sources
of bootstrapping data, it runs with the new bootstrapped
configuration.
4. Otherwise the device MAY loop back through the list of
bootstrapping sources again and/or wait for manual provisioning.
5.3. Processing a Source of Bootstrapping Data
This section describes a recursive algorithm that devices can use to,
ultimately, obtain onboarding information. The algorithm is
recursive because sources of bootstrapping data may return redirect
information, which causes the algorithm to run again, for the newly
discovered sources of bootstrapping information. An expression that
captures all possible successful sequences of bootstrapping
information is zero or more redirect information responses, followed
by one onboarding information response.
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An important aspect of the algorithm is knowing when data needs to be
signed or not. The following figure provides a summary of options:
Untrusted Source Trusted Source
Kind of Bootstrapping Data Can Provide? Can Provide?
Unsigned Redirect Info : Yes+ Yes
Signed Redirect Info : Yes Yes*
Unsigned Onboarding Info : No Yes
Signed Onboarding Info : Yes Yes*
The '+' above denotes that the source redirected to MUST
return signed data, or more unsigned redirect information.
The '*' above denotes that, while possible, it is generally
unnecessary for a trusted source to return signed data.
The recursive algorithm uses a conceptual global-scoped variable
called "trust-state". The trust-state variable is initialized to
FALSE. The ultimate goal of this algorithm is for the device to
process onboarding information (Section 2.2) while the trust-state
variable is TRUE.
If the source of bootstrapping data (Section 4) is a bootstrap server
(Section 4.4), and the device is able to authenticate the bootstrap
server using X.509 certificate path validation ([RFC6125], Section 6)
to one of the device's preconfigured trust anchors, or to a trust
anchor that it learned from a previous step, then the device MUST set
trust-state to TRUE.
When establishing a connection to a trusted bootstrap server (i.e.
trust-state is TRUE), the device MAY, per Section 2.5 in [RFC8040],
identify and authenticate itself to the bootstrap server using a TLS-
level client certificate and/or an HTTP authentication scheme. If
both mechanisms are used, they MUST both identify the same device
using its serial number.
When establishing a connection to an untrusted bootstrap server (i.e.
trust-state is FALSE), it is still necessary for the device to
identify itself, in order to receive device-specific signed data, due
to the ownership voucher encoding the device's serial number. The
device MUST identify and authenticate itself to the bootstrap server
using a TLS-level client certificate and/or an HTTP authentication
scheme. However, because the bootstrap server is untrusted, the
device MUST NOT use an authentication scheme that conveys a shared
secret, such as a password.
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When sending a client certificate, the device MUST also send all the
intermediate certificates leading up to, and optionally including,
the client certificate's well-known trust anchor certificate.
For any source of bootstrapping data (e.g., Section 4), if any
artifact obtained is encrypted, the device MUST first decrypt it
using the private key associated with the device certificate used to
encrypt the artifact.
If the zero touch information artifact is signed, and the device is
able to validate the signed data using the algorithm described in
Section 5.4, then the device MUST set trust-state to TRUE; otherwise,
if the device is unable to validate the signed data, the device MUST
set trust-state to FALSE. Note, this is worded to cover the special
case when signed data is returned even from a trusted bootstrap
server.
If the zero touch information artifact contains onboarding
information, and trust-state is FALSE, the device MUST exit the
recursive algorithm (as this is not allowed, see the figure above),
returning to the state machine described in Section 5.2. Otherwise,
the device MUST attempt to process the onboarding information as
described in Section 5.6. In either case, success or failure, the
device MUST exit the recursive algorithm, returning to the state
machine described in Section 5.2, the only difference being in how it
responds to the "Able to bootstrap from any source?" conditional
described in the figure in the section.
If the zero touch information artifact contains redirect information,
the device MUST process the redirect information as described in
Section 5.5. This is the recursion step, it will cause the device to
reenter this algorithm, but this time the data source will definitely
be a bootstrap server, as that is all redirect information is able to
redirect a device to.
5.4. Validating Signed Data
Whenever a device is presented signed data, it MUST validate the
signed data as described in this section. This includes the case
where the signed data is provided by a trusted source.
Whenever there is signed data, the device MUST also be provided an
ownership voucher and an owner certificate. How all the needed
artifacts are provided for each source of bootstrapping data is
described in Section 4.
In order to validate signed data, the device MUST first authenticate
the ownership voucher by validating its signature to one of its
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preconfigured trust anchors (see Section 5.1), which may entail using
additional intermediate certificates attached to the ownership
voucher. If the device has an accurate clock, it MUST verify that
the ownership voucher was created in the past (i.e., 'created-on' <
now) and, if the 'expires-on' leaf is present, the device MUST verify
that the ownership voucher has not yet expired (i.e., now < 'expires-
on'). The device MUST verify that the ownership voucher's
'assertion' value is acceptable (e.g., some devices may only accept
the assertion value 'verified'). The device MUST verify that the
ownership voucher specifies the device's serial number in the
'serial-number' leaf. If the 'idevid-issuer' leaf is present, the
device MUST verify that the value is set correctly. If the
authentication of the ownership voucher is successful, the device
extracts the 'pinned-domain-cert' node, an X.509 certificate, that is
needed to verify the owner certificate in the next step.
The device MUST next authenticate the owner certificate by performing
X.509 certificate path verification to the trusted certificate
extracted from the ownership voucher's 'pinned-domain-cert' node.
This verification may entail using additional intermediate
certificates attached to the owner certificate artifact. If the
ownership voucher's 'domain-cert-revocation-checks' node's value is
set to "true", the device MUST verify the revocation status of the
certificate chain used to sign the owner certificate and, if the
revocation status is not attainable or if it is determined that a
certificate has been revoked, the device MUST not validate the owner
certificate.
Finally the device MUST verify the zero touch information artifact
was signed by the validated owner certificate.
If any of these steps fail, the device MUST invalidate the signed
data and not perform any subsequent steps.
5.5. Processing Redirect Information
In order to process redirect information (Section 2.1), the device
MUST follow the steps presented in this section.
Processing redirect information is straightforward, the device
sequentially steps through the list of provided bootstrap servers
until it can find one it can bootstrap from.
If a hostname is provided, and the hostname's DNS resolution is to
more than one IP address, the device MUST attempt to connect to all
of the DNS resolved addresses at least once, before moving on to the
next bootstrap server. If the device is able to obtain bootstrapping
data from any of the DNS resolved addresses, it MUST immediately
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process that data, without attempting to connect to any of the other
DNS resolved addresses.
If the redirect information is trusted (e.g., trust-state is TRUE),
and the bootstrap server entry contains a trust anchor certificate,
then the device MUST authenticate the specified bootstrap server's
TLS server certificate using X.509 certificate path validation
([RFC6125], Section 6) to the specified trust anchor. If the
bootstrap server entry does not contain a trust anchor certificate
device, the device MUST establish a provisional connection to the
bootstrap server (i.e., by blindly accepting its server certificate),
and set trust-state to FALSE.
If the redirect information is untrusted (e.g., trust-state is
FALSE), the device MUST discard any trust anchors provided by the
redirect information and establish a provisional connection to the
bootstrap server (i.e., by blindly accepting its TLS server
certificate).
5.6. Processing Onboarding Information
In order to process onboarding information (Section 2.2), the device
MUST follow the steps presented in this section.
When processing onboarding information, the device MUST first process
the boot image information (if any), then execute the pre-
configuration script (if any), then commit the initial configuration
(if any), and then execute the post-configuration script (if any), in
that order. If the device encounters an error at any step, it MUST
NOT proceed to the next step.
When the onboarding information is obtained from a trusted bootstrap
server, the device SHOULD send progress reports throughout the
bootstrapping process using the bootstrap server's 'report-progress'
RPC. When the onboarding information was obtained from an untrusted
bootstrap server, the device SHOULD NOT send any progress reports to
the bootstrap server, even after validating any signed data it may
have receive from the bootstrap server.
If boot image criteria is specified, the device MUST first determine
if the boot image it is running satisfies the specified boot image
criteria. If the device is not running the specified boot image,
then it MUST install the specified boot image or fail processing the
onboarding information. In order to install the specified boot
image, the device MUST download, verify, and install the specified
boot image, and then reboot. To verify the downloaded boot image,
the device MUST check that the boot image file matches the
verification fingerprint supplied by the onboarding information.
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Upon rebooting, the bootstrapping process runs again, which will
eventually come to this very point, but this time the device will be
running the specified boot image, and thus will move to processing
the next step.
Next, for devices that support executing scripts, if a pre-
configuration script has been specified, the device MUST execute the
script and check its exit status code to determine if it had any
warnings or errors. In the case of errors, the device MUST reset
itself in such a way that wipes out any bad state the script may have
left behind.
Next, if an initial configuration has been supplied, the device MUST
commit the provided initial configuration, using the approach
specified by the 'configuration-handling' leaf. If there is an
error, and the device previously executed a pre-configuration script,
the device does not need to reset itself in order to wipe out any
state the script may have left behind; this implies that the pre-
configuration script must be idempotent.
Again, for devices that support executing scripts, if a post-
configuration script has been specified, the device MUST execute the
script and check its exit status code to determine if it had any
warnings or errors. In the case of errors, the device MUST reset
itself in such a way that wipes out any bad state the script may have
left behind.
At this point, the device has completely processed the bootstrapping
data. If the device obtained the onboarding information from a
trusted bootstrap server, the device MUST post the 'bootstrap-
complete' progress report now, using the bootstrap server's 'report-
progress' RPC.
The device is now running its initial configuration. Notably, if
NETCONF Call Home or RESTCONF Call Home [RFC8071] is configured, the
device initiates trying to establish a call home connection at this
time.
6. The Zero Touch Information Data Model
This section defines a YANG 1.1 [RFC7950] module that is used to
define the data model for the zero touch information artifact
described in Section 3.1. This data model uses the 'yang-data'
extension statement defined in [I-D.ietf-netmod-yang-data-ext].
Examples illustrating this data model are provided in Section 6.2.
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6.1. Data Model Overview
The following tree diagram provides an overview of the data model for
the zero touch information artifact.
module: ietf-zerotouch-information
yang-data zerotouch-information:
+---- (information-type)
+--:(redirect-information)
| +---- redirect-information
| +---- bootstrap-server* [address]
| +---- address inet:host
| +---- port? inet:port-number
| +---- trust-anchor? cms
+--:(onboarding-information)
+---- onboarding-information
+---- boot-image
| +---- os-name? string
| +---- os-version? string
| +---- download-uri* inet:uri
| +---- image-verification* [hash-algorithm]
| +---- hash-algorithm identityref
| +---- hash-value yang:hex-string
+---- configuration-handling? enumeration
+---- pre-configuration-script? script
+---- configuration? binary
+---- post-configuration-script? script
6.2. Example Usage
The following example illustrates how redirect information
(Section 2.1) can be encoded using JSON.
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{
"ietf-zerotouch-information:redirect-information" : {
"bootstrap-server" : [
{
"address" : "phs1.example.com",
"port" : 8443,
"trust-anchor" : "base64encodedvalue=="
},
{
"address" : "phs2.example.com",
"port" : 8443,
"trust-anchor" : "base64encodedvalue=="
},
{
"address" : "phs3.example.com",
"port" : 8443,
"trust-anchor" : "base64encodedvalue=="
}
]
}
}
The following example illustrates how onboarding information
(Section 2.2) can be encoded using JSON.
[note: '\' line wrapping for formatting only]
{
"ietf-zerotouch-information:onboarding-information" : {
"boot-image" : {
"os-name" : "VendorOS",
"os-version" : "17.2R1.6",
"download-uri" : [ "http://some/path/to/raw/file" ],
"image-verification" : [
{
"hash-algorithm" : "ietf-zerotouch-information:sha-256",
"hash-value" : "ba:ec:cf:a5:67:82:b4:10:77:c6:67:a6:22:ab:\
7d:50:04:a7:8b:8f:0e:db:02:8b:f4:75:55:fb:c1:13:b2:33"
}
]
},
"configuration-handling" : "merge",
"pre-configuration-script" : "base64encodedvalue==",
"configuration" : "base64encodedvalue==",
"post-configuration-script" : "base64encodedvalue=="
}
}
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6.3. YANG Module
The zero touch information data model is defined by the YANG module
presented in this section.
Note: the module defined herein uses data types defined in [RFC5280],
[RFC6234], and [RFC6991], and an extension statement from
[I-D.ietf-netmod-yang-data-ext], and an encoding defined in
[ITU.X690.1994].
<CODE BEGINS> file "ietf-zerotouch-information@2018-03-05.yang"
module ietf-zerotouch-information {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-zerotouch-information";
prefix zti;
import ietf-yang-types {
prefix yang;
reference "RFC 6991: Common YANG Data Types";
}
import ietf-inet-types {
prefix inet;
reference "RFC 6991: Common YANG Data Types";
}
import ietf-yang-data-ext {
prefix yd;
reference "I-D.ietf-netmod-yang-data-ext: YANG Data Extensions";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: http://tools.ietf.org/wg/netconf
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen <mailto:kwatsen@juniper.net>";
description
"This module defines the data model for the Zero Touch
Information artifact defined in RFC XXXX: Zero Touch
Provisioning for Networking Devices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
and 'OPTIONAL' in the module text are to be interpreted as
described in RFC 2119.
Copyright (c) 2018 IETF Trust and the persons identified as
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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 2018-03-05 {
description
"Initial version";
reference
"RFC XXXX: Zero Touch Provisioning for Networking Devices";
}
// identities
identity hash-algorithm {
description
"A base identity for hash algorithm verification";
}
identity sha-256 {
base "hash-algorithm";
description "The SHA-256 algorithm.";
reference "RFC 6234: US Secure Hash Algorithms.";
}
// typedefs
typedef cms {
type binary;
description
"A CMS structure, as specified in RFC 5652, encoded using
ASN.1 distinguished encoding rules (DER), as specified in
ITU-T X.690.";
reference
"RFC 5652:
Cryptographic Message Syntax (CMS)
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).";
}
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// yang-data
yd:yang-data "zerotouch-information" {
choice information-type {
mandatory true;
description
"This choice statement ensures the response contains
redirect-information or onboarding-information.";
container redirect-information {
description
"Redirect information is described in Section 2.1 in
RFC XXXX. Its purpose is to redirect a device to
another bootstrap server.";
reference
"RFC XXXX: Zero Touch Provisioning for Networking Devices";
list bootstrap-server {
key "address";
min-elements 1;
description
"A bootstrap server entry.";
leaf address {
type inet:host;
mandatory true;
description
"The IP address or hostname of the bootstrap server the
device should redirect to.";
}
leaf port {
type inet:port-number;
default "443";
description
"The port number the bootstrap server listens on. If no
port is specified, the IANA-assigned port for 'https'
(443) is used.";
}
leaf trust-anchor {
type cms;
description
"A CMS structure that MUST contain the chain of
X.509 certificates needed to authenticate the TLS
certificate presented by this bootstrap server.
In all cases, the chain MUST include a self-signed
root certificate. In the case where the root
certificate is itself the issuer of the bootstrap
server's TLS certificate, only one X.509 certificate
is present. If needed by the device, this CMS
structure MAY also contain suitably fresh revocation
objects with which the device can verify the
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revocation status of the certificates.
This CMS encodes the degenerate form of the SignedData
structure that is commonly used to disseminate X.509
certificates and revocation objects.";
reference
"RFC 5280:
Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile.";
}
}
}
container onboarding-information {
description
"Onboarding information is described in Section 2.2 in
RFC XXXX. Its purpose is to provide the device everything
it needs to bootstrap itself.";
reference
"RFC XXXX: Zero Touch Provisioning for Networking Devices";
container boot-image {
description
"Specifies criteria for the boot image the device MUST
be running, as well as information enabling the device
to install the required boot image.";
leaf os-name {
type string;
description
"The name of the operating system software the device
MUST be running in order to not require a software
image upgrade (ex. VendorOS).";
}
leaf os-version {
type string;
description
"The version of the operating system software the
device MUST be running in order to not require a
software image upgrade (ex. 17.3R2.1).";
}
leaf-list download-uri {
type inet:uri;
must '../image-verification' {
description
"Image verification information must be provided if
the device is going to download an image.";
}
ordered-by user;
description
"An ordered list of URIs to where the necessary
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boot-image file may be obtained. Deployments must
know through out-of-band means which URI schemes
(http, ftp, etc.) the bootstrapping device supports.
If a secure scheme (e.g., https) is provided, a
device MAY establish an untrusted connection to the
remote server to obtain the boot-image.";
}
list image-verification {
must '../download-uri' {
description
"Download URIs must be provided if an image is to
be verified.";
}
key hash-algorithm;
description
"A list of hash values that a device can use to verify
boot image files with.";
leaf hash-algorithm {
type identityref {
base "hash-algorithm";
}
description
"Identifies the hash algorithm used.";
}
leaf hash-value {
type yang:hex-string;
mandatory true;
description
"The hex-encoded value of the specified hash
algorithm over the contents of the boot image
file.";
}
}
}
leaf configuration-handling {
type enumeration {
enum "merge" {
description
"Merge configuration into the running datastore.";
}
enum "replace" {
description
"Replace the existing running datastore with the
passed configuration.";
}
}
must '../configuration';
description
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"This enumeration indicates how the server should process
the provided configuration.";
}
leaf pre-configuration-script {
type script;
description
"A script that, when present, is executed before the
configuration has been processed.";
}
leaf configuration {
type binary;
must '../configuration-handling';
description
"Any configuration known to the device. The use of
the 'binary' type enables e.g., XML-content to be
embedded into a JSON document. The exact encoding
of the content, as with the scripts, is vendor
specific.";
}
leaf post-configuration-script {
type script;
description
"A script that, when present, is executed after the
configuration has been processed.";
}
}
}
}
typedef script {
type binary;
description
"A device specific script that enables the execution of
commands to perform actions not possible thru configuration
alone.
No attempt is made to standardize the contents, running
context, or programming language of the script, other than
that it can emit an exit status code and stderr/sdtout. The
contents of the script are considered specific to the vendor,
product line, and/or model of the device.
If a script is erroneously provided to a device that does not
support the execution of scripts, and the device obtained the
onboarding information from a trusted bootstrap server, the
device SHOULD send either a 'pre-script-warning' or
'post-script-warning' progress report, based on which kind
of script was presented, but otherwise continue processing
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the bootstrapping data as if the script had not been present.
The script returns exit status code zero on success and
non-zero otherwise, with accompanying stderr/stdout for
logging purposes.
If the exit status code is greater than zero, then the device
should assume that the script had a soft error, which the
script believes does not affect manageability. If the device
obtained the bootstrap information from a trusted bootstrap
server, it SHOULD either send a 'pre-script-warning' or
'post-script-warning' progress report, based on which kind of
script was executed.
If the exit status code is less than zero, the device should
assume the script had a hard error, which the script believes
will affect manageability. If the device obtained the
bootstrap information from a trusted bootstrap server, it
SHOULD send a 'pre-script-error' or 'post-script-error'
progress report, based on which kind of script was executed,
followed by a reset that will wipe out any bad state left by
the script, and restart the entire bootstrapping process.";
}
}
<CODE ENDS>
7. The Zero Touch Bootstrap Server API
This section defines the API for bootstrap servers. The API is
defined as that produced by a RESTCONF [RFC8040] server that supports
the YANG 1.1 [RFC7950] module defined in this section.
7.1. API Overview
The following tree diagram provides an overview for the bootstrap
server RESTCONF API.
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module: ietf-zerotouch-bootstrap-server
rpcs:
+---x get-bootstrapping-data
| +---w input
| | +---w untrusted-connection? empty
| | +---w hw-model? string
| | +---w os-name? string
| | +---w os-version? string
| | +---w nonce? binary
| +--ro output
| +--ro zerotouch-information cms
| +--ro owner-certificate? cms
| +--ro ownership-voucher? cms
+---x report-progress
+---w input
+---w progress-type enumeration
+---w message? string
+---w ssh-host-keys
| +---w ssh-host-key* []
| +---w format enumeration
| +---w key-data string
+---w trust-anchors
+---w trust-anchor* []
+---w certificate cms
7.2. Example Usage
This section presents three examples illustrating the bootstrap
server's API. Two examples are provided for the 'get-bootstrapping-
data' RPC (once to an untrusted bootstrap server, and again to a
trusted bootstrap server), and one example for the 'report-progress'
RPC.
The following example illustrates a device using the API to fetch its
bootstrapping data from a untrusted bootstrap server. In this
example, the device sends the 'untrusted-connection' input parameter
and receives signed data in the response.
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REQUEST
-------
['\' line wrapping added for formatting only]
POST /restconf/operations/ietf-zerotouch-bootstrap-server:get-boot\
strapping-data HTTP/1.1
HOST: example.com
Content-Type: application/yang.data+xml
<input
xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server">
<untrusted-connection/>
</input>
RESPONSE
--------
HTTP/1.1 200 OK
Date: Sat, 31 Oct 2015 17:02:40 GMT
Server: example-server
Content-Type: application/yang.data+xml
<output
xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server">
<zerotouch-information>base64encodedvalue==</zerotouch-information>
<owner-certificate>base64encodedvalue==</owner-certificate>
<ownership-voucher>base64encodedvalue==</ownership-voucher>
</output>
The following example illustrates a device using the API to fetch its
bootstrapping data from a trusted bootstrap server. In this example,
the device sends addition input parameters to the bootstrap server,
which it may use when formulating its response to the device.
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REQUEST
-------
['\' line wrapping added for formatting only]
POST /restconf/operations/ietf-zerotouch-bootstrap-server:get-boot\
strapping-data HTTP/1.1
HOST: example.com
Content-Type: application/yang.data+xml
<input
xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server">
<hw-model>model-x</hw-model>
<os-name>vendor-os</os-name>
<os-version>17.3R2.1</os-version>
<nonce>base64encodedvalue==</nonce>
</input>
RESPONSE
--------
HTTP/1.1 200 OK
Date: Sat, 31 Oct 2015 17:02:40 GMT
Server: example-server
Content-Type: application/yang.data+xml
<output
xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server">
<zerotouch-information>base64encodedvalue==</zerotouch-information>
</output>
The following example illustrates a device using the API to post a
progress report to a bootstrap server. Illustrated below is the
'bootstrap-complete' message, but the device may send other progress
reports to the server while bootstrapping. In this example, the
device is sending both its SSH host keys and a TLS server
certificate, which the bootstrap server may, for example, pass to an
NMS, as discussed in Appendix B.3.
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REQUEST
-------
['\' line wrapping added for formatting only]
POST /restconf/operations/ietf-zerotouch-bootstrap-server:report-\
progress HTTP/1.1
HOST: example.com
Content-Type: application/yang.data+xml
<input xmlns=
"urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server">
<progress-type>bootstrap-complete</progress-type>
<message>example message</message>
<ssh-host-keys>
<ssh-host-key>
<format>ssh-rsa</format>
<key-data>base64encodedvalue==</key-data>
</ssh-host-key>
<ssh-host-key>
<format>ssh-dss</format>
<key-data>base64encodedvalue==</key-data>
</ssh-host-key>
</ssh-host-keys>
<trust-anchors>
<trust-anchor>
<certificate>base64encodedvalue==</certificate>
</trust-anchor>
</trust-anchors>
</input>
RESPONSE
--------
HTTP/1.1 204 No Content
Date: Sat, 31 Oct 2015 17:02:40 GMT
Server: example-server
7.3. YANG Module
The bootstrap server's device-facing API is normatively defined by
the YANG module defined in this section.
Note: the module defined herein uses data types defined in [RFC5652],
[RFC5280], [RFC6960], and [I-D.ietf-anima-voucher], and uses an
encoding defined in [ITU.X690.1994].
<CODE BEGINS> file "ietf-zerotouch-bootstrap-server@2018-03-05.yang"
module ietf-zerotouch-bootstrap-server {
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yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server";
prefix ztbs;
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen <mailto:kwatsen@juniper.net>";
description
"This module defines an interface for bootstrap servers, as
defined by RFC XXXX: Zero Touch Provisioning for Networking
Devices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY',
and 'OPTIONAL' in the module text are to be interpreted as
described in RFC 2119.
Copyright (c) 2018 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 2018-03-05 {
description
"Initial version";
reference
"RFC XXXX: Zero Touch Provisioning for Networking Devices";
}
// typedefs
typedef cms {
type binary;
description
"A CMS structure, as specified in RFC 5652, encoded using
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ASN.1 distinguished encoding rules (DER), as specified in
ITU-T X.690.";
reference
"RFC 5652:
Cryptographic Message Syntax (CMS)
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).";
}
// RPCs
rpc get-bootstrapping-data {
description
"This RPC enables a device, as identified by the RESTCONF
username, to obtain bootstrapping data that has been made
available for it.";
input {
leaf untrusted-connection {
type empty;
description
"This optional input parameter enables a device to
communicate to the bootstrap server that it is unable to
authenticate the bootstrap server's TLS certificate. In
such circumstances, the device likely does not send any
of the other input parameters, except for the 'nonce'
parameter. Upon receiving this input parameter, the
bootstrap server should only return unsigned redirect
information or signed data of any type.";
}
leaf hw-model {
type string;
description
"This optional input parameter enables a device to
communicate to the bootstrap server its vendor specific
hardware model number. This parameter may be needed,
for instance, when a device's IDevID certificate does
not include the 'hardwareModelName' value in its
subjectAltName field, as is allowed by 802.1AR-2009.";
reference
"IEEE 802.1AR-2009: IEEE Standard for Local and
metropolitan area networks - Secure Device Identity";
}
leaf os-name {
type string;
description
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"This optional input parameter enables a device to
communicate to the bootstrap server the name of its
operating system. This parameter may be useful if
the device, as identified by its serial number, can
run more than one type of operating system (e.g.,
on a white-box system.";
}
leaf os-version {
type string;
description
"This optional input parameter enables a device to
communicate to the bootstrap server the version of its
operating system. This parameter may be used by a
bootstrap server to return an operating system specific
response to the device, thus negating the need for a
potentially expensive boot-image update.";
}
leaf nonce {
type binary {
length "8..32";
}
description
"This optional input parameter enables a device to
communicate to the bootstrap server a nonce value.
This may be especially useful for devices lacking
an accurate clock, as then the bootstrap server
can dynamically obtain from the manufacturer a
voucher with the nonce value in it, as described
in I-D.ietf-anima-voucher.";
reference
"RFC ZZZZ: Voucher Profile for Bootstrapping Protocols.";
}
}
output {
leaf zerotouch-information {
type cms;
mandatory true;
description
"A zero touch information artifact, as described in
Section 3.1 of RFC XXXX.";
reference
"RFC XXXX:
Zero Touch Provisioning for Networking Devices";
}
leaf owner-certificate {
type cms;
must '../ownership-voucher' {
description
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"An ownership voucher must be present whenever an owner
certificate is presented.";
}
description
"An owner certificate artifact, as described in Section
3.2 of RFC XXXX. This leaf is optional because it is
only needed when the zero touch information artifact
is signed.";
reference
"RFC XXXX:
Zero Touch Provisioning for Networking Devices";
}
leaf ownership-voucher {
type cms;
must '../owner-certificate' {
description
"An owner certificate must be present whenever an
ownership voucher is presented.";
}
description
"An ownership voucher artifact, as described by Section
3.3 of RFC XXXX. This leaf is optional because it is
only needed when the zero touch information artifact
is signed.";
reference
"RFC XXXX:
Zero Touch Provisioning for Networking Devices";
}
}
}
rpc report-progress {
description
"This RPC enables a device, as identified by the RESTCONF
username, to report its bootstrapping progress to the
bootstrap server. This RPC is expected to be used when
the device obtains onboarding-information from a trusted
bootstap server.";
input {
leaf progress-type {
type enumeration {
enum "bootstrap-initiated" {
description
"Indicates that the device just used the
'get-bootstrapping-data' RPC. The 'message' node
below MAY contain any additional information that
the manufacturer thinks might be useful.";
}
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enum "parsing-warning" {
description
"Indicates that the device had a non-fatal error when
parsing the response from the bootstrap server. The
'message' node below SHOULD indicate the specific
warning that occurred.";
}
enum "parsing-error" {
description
"Indicates that the device encountered a fatal error
when parsing the response from the bootstrap server.
For instance, this could be due to malformed encoding,
the device expecting signed data when only unsigned
data is provided, the ownership voucher not listing
the device's serial number, or because the signature
didn't match. The 'message' node below SHOULD
indicate the specific error. This progress type
also indicates that the device has abandoned trying
to bootstrap off this bootstrap server.";
}
enum "boot-image-warning" {
description
"Indicates that the device encountered a non-fatal
error condition when trying to install a boot-image.
A possible reason might include a need to reformat a
partition causing loss of data. The 'message' node
below SHOULD indicate any warning messages that were
generated.";
}
enum "boot-image-error" {
description
"Indicates that the device encountered an error when
trying to install a boot-image, which could be for
reasons such as a file server being unreachable,
file not found, signature mismatch, etc. The
'message' node SHOULD indicate the specific error
that occurred. This progress type also indicates
that the device has abandoned trying to bootstrap
off this bootstrap server.";
}
enum "pre-script-warning" {
description
"Indicates that the device obtained a greater than
zero exit status code from the script when it was
executed. The 'message' node below SHOULD indicate
both the resulting exit status code, as well as
capture any stdout/stderr messages the script may
have produced.";
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}
enum "pre-script-error" {
description
"Indicates that the device obtained a less than
zero exit status code from the script when it was
executed. The 'message' node below SHOULD indicate
both the resulting exit status code, as well as
capture any stdout/stderr messages the script may
have produced. This progress type also indicates
that the device has abandoned trying to bootstrap
off this bootstrap server.";
}
enum "config-warning" {
description
"Indicates that the device obtained warning messages
when it committed the initial configuration. The
'message' node below SHOULD indicate any warning
messages that were generated.";
}
enum "config-error" {
description
"Indicates that the device obtained error messages
when it committed the initial configuration. The
'message' node below SHOULD indicate the error
messages that were generated. This progress type
also indicates that the device has abandoned trying
to bootstrap off this bootstrap server.";
}
enum "post-script-warning" {
description
"Indicates that the device obtained a greater than
zero exit status code from the script when it was
executed. The 'message' node below SHOULD indicate
both the resulting exit status code, as well as
capture any stdout/stderr messages the script may
have produced.";
}
enum "post-script-error" {
description
"Indicates that the device obtained a less than
zero exit status code from the script when it was
executed. The 'message' node below SHOULD indicate
both the resulting exit status code, as well as
capture any stdout/stderr messages the script may
have produced. This progress type also indicates
that the device has abandoned trying to bootstrap
off this bootstrap server.";
}
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enum "bootstrap-complete" {
description
"Indicates that the device successfully processed
all 'onboarding-information' provided, and that it
is ready to be managed. The 'message' node below
MAY contain any additional information that the
manufacturer thinks might be useful. After sending
this progress type, the device is not expected to
access the bootstrap server again.";
}
enum "informational" {
description
"Indicates any additional information not captured
by any of the other progress types. For instance, a
message indicating that the device is about to
reboot after having installed a boot-image could
be provided. The 'message' node below SHOULD
contain information that the manufacturer thinks
might be useful.";
}
}
mandatory true;
description
"The type of progress report provided.";
}
leaf message {
type string;
description
"An optional arbitrary value.";
}
container ssh-host-keys {
when "../progress-type = 'bootstrap-complete'" {
description
"SSH host keys are only sent when the progress type
is 'bootstrap-complete'.";
}
description
"A list of trust anchor certificates an NMS may use to
authenticate subsequent SSH-based connections to this
device (e.g., netconf-ssh, netconf-ch-ssh).";
list ssh-host-key {
description
"An SSH host-key.";
leaf format {
type enumeration {
enum "ssh-dss" {
description
"The SSH host key is a ssh-dss based key.";
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}
enum "ssh-rsa" {
description
"The SSH host key is a ssh-rsa based key.";
}
}
mandatory true;
description
"The format of the SSH host key.";
}
leaf key-data {
type string;
mandatory true;
description
"The key data for the SSH host key";
}
}
}
container trust-anchors {
when "../progress-type = 'bootstrap-complete'" {
description
"Trust anchors are only sent when the progress type
is 'bootstrap-complete'.";
}
description
"A list of trust anchor certificates an NMS may use to
authenticate subsequent certificate-based connections
to this device (e.g., restconf-tls, netconf-tls, or
even netconf-ssh with X.509 support from RFC 6187).
In practice, trust anchors for IDevID certificates do
not need to be conveyed using this mechanism.";
reference
"RFC 6187:
X.509v3 Certificates for Secure Shell Authentication.";
list trust-anchor {
description
"A trust anchor.";
leaf certificate {
type cms;
mandatory true;
description
"An X.509 v3 certificate structure, as specified
by Section 4 in RFC 5280, encoded using ASN.1
distinguished encoding rules (DER), as specified
in ITU-T X.690.";
reference
"RFC 5280:
Internet X.509 Public Key Infrastructure
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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).";
}
}
}
}
}
}
<CODE ENDS>
8. The Zero Touch Device Data Model
This section defines a non-normative data model that enables the
configuration of zerotouch bootstrapping and discovery of what
parameters are used by a device's bootstrapping logic.
8.1. Data Model Overview
The following tree diagram provides an overview for the zerotouch
device data model.
module: example-zerotouch-device
+--rw zerotouch
+--rw enabled? boolean
+--ro idevid-certificate? cms
| {bootstrap-servers}?
+--ro bootstrap-servers {bootstrap-servers}?
| +--ro bootstrap-server* [address]
| +--ro address inet:host
| +--ro port? inet:port-number
+--ro bootstrap-server-pinned-certificates?
| -> /ks:keystore/pinned-certificates/name
| {bootstrap-servers}?
+--ro voucher-pinned-certificates?
-> /ks:keystore/pinned-certificates/name {signed-data}?
In the above diagram, notice that there is only one configurable node
'enabled'. The expectation is that this node would be set to 'true'
in device's factory default configuration and that it would either be
set to 'false' or deleted when the zerotouch bootstrapping is longer
needed.
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8.2. Example Usage
Following is an instance example for this data model.
[note: '\' line wrapping for formatting only]
<zerotouch
xmlns="https://example.com/zerotouch-device">
<enabled>true</enabled>
<idevid-certificate>base64encodedvalue==</idevid-certificate>
<bootstrap-servers>
<bootstrap-server>
<address>phs1.example.com</address>
<port>8443</port>
</bootstrap-server>
<bootstrap-server>
<address>phs2.example.com</address>
<port>8443</port>
</bootstrap-server>
<bootstrap-server>
<address>phs3.example.com</address>
<port>8443</port>
</bootstrap-server>
</bootstrap-servers>
<bootstrap-server-pinned-certificates>manufacturers-root-ca-certs<\
/bootstrap-server-pinned-certificates>
<voucher-pinned-certificates>manufacturers-root-ca-certs</voucher-\
pinned-certificates>
</zerotouch>
8.3. YANG Module
The device model is defined by the YANG module defined in this
section.
Note: the module defined herein uses data types defined in [RFC5652],
[RFC6991], and [I-D.ietf-netconf-keystore], and uses an encoding
defined in [ITU.X690.1994].
module example-zerotouch-device {
yang-version 1.1;
namespace "https://example.com/zerotouch-device";
prefix ztd;
import ietf-inet-types {
prefix inet;
reference "RFC 6991: Common YANG Data Types";
}
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import ietf-keystore {
prefix ks;
revision-date 2017-10-30;
description
"This revision is defined in draft-ietf-netconf-keystore-04.";
reference
"I-D.ietf-netconf-keystore:
YANG Data Model for a Keystore Mechanism";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen <mailto:kwatsen@juniper.net>";
description
"This module defines a data model to enable zerotouch
bootstrapping and discover what parameters are used.
This module assumes the use of an IDevID certificate,
as opposed to any other client certificate, or the
use of an HTTP-based client authentication scheme.
Copyright (c) 2018 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 2018-03-05 {
description
"Initial version";
reference
"RFC XXXX: Zero Touch Provisioning for Networking Devices";
}
// features
feature bootstrap-servers {
description
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"The device supports bootstrapping off bootstrap servers.";
}
feature signed-data {
description
"The device supports bootstrapping off signed data.";
}
// typedefs
typedef cms {
type binary;
description
"A CMS structure, as specified in RFC 5652, encoded using
ASN.1 distinguished encoding rules (DER), as specified in
ITU-T X.690.";
reference
"RFC 5652:
Cryptographic Message Syntax (CMS)
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).";
}
// protocol accessible nodes
container zerotouch {
description
"Top-level container for zerotouch data model.";
leaf enabled {
type boolean;
default false;
description
"The 'enabled' leaf controls if zerotouch bootstrapping is
enabled or disabled. The default is 'false' so that, when
not enabled, which is most of the time, no configuration
is needed.";
}
leaf idevid-certificate {
if-feature bootstrap-servers;
type cms;
config false;
description
"An CMS SignedData structure, as specified by Section 5 of
RFC 5652. This is the degenerate form of the SignedData
structure, whereby there are no signers, that is commonly
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used to disseminate certificates.
This CMS structure contains the IEEE 802.1AR-2009
IDevID certificate itself, and all intermediate
certificates leading up to, and optionally including,
the manufacturer's well-known trust anchor certificate
for IDevID certificates. The well-known trust anchor
does not have to be a self-signed certificate.";
reference
"RFC 5652:
Cryptographic Message Syntax (CMS)
IEEE 802.1AR-2009:
IEEE Standard for Local and metropolitan area
networks - Secure Device Identity.";
}
container bootstrap-servers {
if-feature bootstrap-servers;
config false;
description
"List of bootstrap servers this device will attempt
to reach out to when bootstrapping.";
list bootstrap-server {
key "address";
description
"A bootstrap server entry.";
leaf address {
type inet:host;
mandatory true;
description
"The IP address or hostname of the bootstrap server the
device should redirect to.";
}
leaf port {
type inet:port-number;
default "443";
description
"The port number the bootstrap server listens on. If no
port is specified, the IANA-assigned port for 'https'
(443) is used.";
}
}
}
leaf bootstrap-server-pinned-certificates {
if-feature bootstrap-servers;
type leafref {
path "/ks:keystore/ks:pinned-certificates/ks:name";
}
config false;
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description
"A reference to a list of pinned certificate authority (CA)
certificates that the device uses to validate bootstrap
servers with.";
}
leaf voucher-pinned-certificates {
if-feature signed-data;
type leafref {
path "/ks:keystore/ks:pinned-certificates/ks:name";
}
config false;
description
"A reference to a list of pinned certificate authority (CA)
certificates that the device uses to validate ownership
vouchers with.";
}
}
}
9. DHCP Zero Touch Options
This section defines two DHCP options, one for DHCPv4 and one for
DHCPv6. These two options are semantically the same, though
syntactically different.
9.1. DHCPv4 Zero Touch Option
The DHCPv4 Zero Touch Option is used to provision the client with one
or more URIs for bootstrap servers that can be contacted to attempt
further configuration.
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DHCPv4 Zero Touch Redirect Option
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| option-code (143) | option-length |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
. .
. bootstrap-server-list (variable length) .
. .
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
o option-code: OPTION_V4_ZEROTOUCH_REDIRECT (143)
o option-length: The option length in octets
o bootstrap-server-list: A list of servers for the
client to attempt contacting, in order to obtain
further bootstrapping data, in the format shown
in [common-field-encoding].
DHCPv4 Client Behavior
Clients MAY request the OPTION_V4_ZEROTOUCH_REDIRECT by including its
option code in the Parameter Request List (55) in DHCP request
messages.
On receipt of a DHCPv4 Reply message which contains the
OPTION_V4_ZEROTOUCH_REDIRECT, the client processes the response
according to Section 5.5, with the understanding that the 'address'
and 'port' values are encoded in the URIs.
Any invalid URI entries received in the uri-data field are ignored by
the client. If OPTION_V4_ZEROTOUCH_REDIRECT does not contain at
least one valid URI entry in the uri-data field, then the client MUST
discard the option.
As the list of URIs may exceed the maximum allowed length of a single
DHCPv4 option (255 octets), the client MUST implement [RFC3396],
allowing the URI list to be split across a number of
OPTION_V4_ZEROTOUCH_REDIRECT option instances.
DHCPv4 Server Behavior
The DHCPv4 server MAY include a single instance of Option
OPTION_V4_ZEROTOUCH_REDIRECT in DHCP messages it sends. Servers MUST
NOT send more than one instance of the OPTION_V4_ZEROTOUCH_REDIRECT
option.
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As the list of URIs may exceed the maximum allowed length of a single
DHCPv4 option (255 octets), the server MUST implement [RFC3396],
allowing the URI list to be split across a number of
OPTION_V4_ZEROTOUCH_REDIRECT option instances.
9.2. DHCPv6 Zero Touch Option
The DHCPv6 Zero Touch Option is used to provision the client with one
or more URIs for bootstrap servers that can be contacted to attempt
further configuration.
DHCPv6 Zero Touch Redirect Option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code (136) | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. bootstrap-server-list (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o option-code: OPTION_V6_ZEROTOUCH_REDIRECT (136)
o option-length: The option length in octets
o bootstrap-server-list: A list of servers for the client to
attempt contacting, in order to obtain further bootstrapping
data, in the format shown in [common-field-encoding].
DHCPv6 Client Behavior
Clients MAY request the OPTION_V6_ZEROTOUCH_REDIRECT option, as
defined in [RFC3315], Sections 17.1.1, 18.1.1, 18.1.3, 18.1.4,
18.1.5, and 22.7. As a convenience to the reader, we mention here
that the client includes requested option codes in the Option Request
Option.
On receipt of a DHCPv6 Reply message which contains the
OPTION_V6_ZEROTOUCH_REDIRECT, the client processes the response
according to Section 5.5, with the understanding that the 'address'
and 'port' values are encoded in the URIs.
Any invalid URI entries received in the uri-data field are ignored by
the client. If OPTION_V6_ZEROTOUCH_REDIRECT does not contain at
least one valid URI entry in the uri-data field, then the client MUST
discard the option.
DHCPv6 Server Behavior
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Sections 17.2.2 and 18.2 of [RFC3315] govern server operation
in regard to option assignment. As a convenience to the reader,
we mention here that the server will send a particular option code
only if configured with specific values for that option code and if
the client requested it.
Option OPTION_V6_ZEROTOUCH_REDIRECT is a singleton. Servers MUST NOT
send more than one instance of the OPTION_V6_ZEROTOUCH_REDIRECT
option.
9.3. Common Field Encoding
Both of the DHCPv4 and DHCPv6 options defined in this section encode
a list of bootstrap server URIs. The "URI" structure is an option
that can contain multiple URIs (see [RFC7227], Section 5.7).
bootstrap-server-list:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| uri-length | URI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
o uri-length: variable, in octets.
o URI: URI of zerotouch bootstrap server, using the HTTPS URI
scheme defined in Section 2.7.2 of RFC7230. URI MUST be in
form "https://<ip-address-or-hostname>[:<port>]".
10. Security Considerations
10.1. Immutable Storage for Trust Anchors
Devices MUST ensure that all their trust anchor certificates,
including those for connecting to bootstrap servers and verifying
ownership vouchers, are protected from external modification.
It may be necessary to update these certificates over time (e.g., the
manufacturer wants to delegate trust to a new CA). It is therefore
expected that devices MAY update these trust anchors when needed
through a verifiable process, such as a software upgrade using signed
software images.
10.2. Secure Storage for Long-lived Private Keys
Manufacturer-generated device identifiers may have very long
lifetimes. For instance, [Std-802.1AR-2009] recommends using the
"notAfter" value 99991231235959Z in IDevID certificates. Given the
long-lived nature of these private keys, it is paramount that they
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are stored so as to resist discovery, such as in a secure
cryptographic processor (e.g., a TPM).
10.3. Use of IDevID Certificates
IDevID certificates, as defined in [Std-802.1AR-2009], are
RECOMMENDED, both for the TLS-level client certificate used by
devices when connecting to a bootstrap server, as well as for the
device identity certificate used by owners when encrypting the
zerotouch artifacts.
10.4. Clock Sensitivity
The solution in this document relies on TLS certificates, owner
certificates, and ownership vouchers, all of which require an
accurate clock in order to be processed correctly (e.g., to test
validity dates and revocation status). Implementations SHOULD 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, it is RECOMMENDED
that implementations disable the aspects of the solution having clock
sensitivity. In particular, such implementations should assume that
TLS certificates, ownership vouchers, and owner certificates never
expire and are not revokable. From an ownership voucher perspective,
manufacturers SHOULD issue a single ownership voucher for the
lifetime of such devices.
Implementations SHOULD NOT rely on NTP for time, as NTP is not a
secure protocol.
10.5. Blindly authenticating a bootstrap server
This document allows a device to blindly authenticate a bootstrap
server's TLS certificate. It does so to allow for cases where the
redirect information may be obtained in an unsecured manner, which is
desirable to support in some cases.
To compensate for this, this document requires that devices, when
connected to an untrusted bootstrap server, assert that data
downloaded from the server is signed.
10.6. Disclosing Information to Untrusted Servers
This document enables devices to establish provisional connections to
bootstrap servers, in order for the bootstrap server to provide
either unsigned redirect information or signed data of any type to
the device. However, since the server is untrusted, it may be under
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the control of an adversary, and therefore devices should be cautious
about the data they send in such cases.
This document requires devices identify and authenticate themselves
to untrusted bootstrap servers. Depending on the authentication
mechanisms used, this means that, at a minimum, the device's serial
number may be disclosed to an adversary. Serial numbers are
ubiquitous and prominently contained in invoices and on labels
affixed to devices and their packaging. That said, serial numbers
many times encode revealing information, such as the device's model
number, manufacture date, and/or manufacturing sequence number.
Knowledge of this information may provide an adversary with details
needed to launch an attack.
In addition to the information relayed during the authentication,
other potentially identifying values that may be disclosed to an
untrusted server, including 'os-name', 'os-version', 'hw-model', and
progress reports. In order to address this issue, it is RECOMMENDED
that bootstrap server implementations promote the untrusted
connection to a trusted connection, as described in Appendix A.
10.7. Sequencing Sources of Bootstrapping Data
For devices supporting more than one source for bootstrapping data,
no particular sequencing order has to be observed for security
reasons, as the solution for each source is considered equally
secure. However, from a privacy perspective, it is RECOMMENDED that
devices access local sources before accessing remote sources.
10.8. The "ietf-zerotouch-information" YANG Module
The ietf-zerotouch-information module defined in this document
defines a data structure that is always wrapped by a CMS structure.
When accessed by a secure mechanism (e.g., protected by TLS), then
the CMS structure may be unsigned. However, when accessed by an
insecure mechanism (e.g., removable storage device), then the CMS
structure must be signed, in order for the device to trust it.
Implementations should be aware that signed bootstrapping data only
protects the data from modification, the contents are still visible
to others. This doesn't affect Security so much as Privacy. That
the contents may be read by unintended parties when accessed by
insecure mechanisms is considered next.
The ietf-zerotouch-information module defines a top-level 'choice'
statement that declares the contents are either "redirect-
information" or "onboarding-information". Each of these two cases
are now considered.
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When the contents of the CMS structure are redirect-information, an
observer can learn about the bootstrap servers the device is being
directed, their IP addresses or hostnames, ports, and trust anchor
certificates. Knowledge of this information could provide an
observer some insight into a network's inner structure.
When the contents of the CMS structure are onboarding-information, as
observer could learn considerable information about how the device is
to be provisioned. This information includes the specific operating
system version, the initial configuration, and the specific scripts
that the device is to run. All of this information should be
considered highly sensitive and precautions should be taken to
protect it from falling into the wrong hands.
10.9. The "ietf-zerotouch-bootstrap-server" YANG Module
The ietf-zerotouch-bootstrap-server module defined in this document
specifies an API for a RESTCONF [RFC8040]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC5246].
The NETCONF Access Control Model (NACM) [RFC6536] provides the means
to restrict access for particular users to a preconfigured subset of
all available protocol operations and content.
This module presents no data nodes (only RPCs). There is no need to
discuss the sensitivity of data nodes.
This module defines two RPC operations that may be considered
sensitive in some network environments. These are the operations and
their sensitivity/vulnerability:
get-bootstrapping-data: This RPC is used by devices to obtain their
bootstrapping data. By design, each device, as identified by its
authentication credentials (e.g. client certificate), can only
obtain its own data. NACM is not needed to further constrain
access to this RPC.
report-progress: This RPC is used by devices to report their
bootstrapping progress. By design, each device, as identified by
its authentication credentials (e.g. client certificate), can
only report data for itself. NACM is not needed to further
constrain access to this RPC.
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11. IANA Considerations
11.1. The IETF XML Registry
This document registers two URIs in the IETF XML registry [RFC3688].
Following the format in [RFC3688], the following registrations are
requested:
URI: urn:ietf:params:xml:ns:yang:ietf-zerotouch-information
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server
Registrant Contact: The NETCONF WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
11.2. The YANG Module Names Registry
This document registers two YANG modules in the YANG Module Names
registry [RFC6020]. Following the format defined in [RFC6020], the
the following registrations are requested:
name: ietf-zerotouch-information
namespace: urn:ietf:params:xml:ns:yang:ietf-zerotouch-information
prefix: zti
reference: RFC XXXX
name: ietf-zerotouch-bootstrap-server
namespace: urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-\
server (note: '\' used for formatting reasons only)
prefix: ztbs
reference: RFC XXXX
11.3. The SMI Security for S/MIME CMS Content Type Registry
IANA is kindly requested to two entries in the "SMI Security for
S/MIME CMS Content Type" registry (1.2.840.113549.1.9.16.1), with
values as follows:
Decimal Description References
------- -------------------------------------- ----------
TBD1 id-ct-zerotouchInformationXML [RFCXXXX]
TBD2 id-ct-zerotouchInformationJSON [RFCXXXX]
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11.4. The BOOTP Manufacturer Extensions and DHCP Options Registry
IANA is kindly requested to make permanent the following early code
point allocation in the "BOOTP Manufacturer Extensions and DHCP
Options" registry maintained at http://www.iana.org/assignments/
bootp-dhcp-parameters:
Tag: 143
Name: OPTION_V4_ZEROTOUCH_REDIRECT
Data Length: N
Meaning: This option provides a list of URIs
for zerotouch bootstrap servers
Reference: [RFCXXXX]
And the following early code point allocation in the "Dynamic Host
Configuration Protocol for IPv6 (DHCPv6)" registry maintained at
http://www.iana.org/assignments/dhcpv6-parameters:
Value: 136
Description: OPTION_V6_ZEROTOUCH_REDIRECT
Reference: [RFCXXXX]
12. Acknowledgements
The authors would like to thank for following for lively discussions
on list and in the halls (ordered by last name): David Harrington,
Michael Behringer, Dean Bogdanovic, Martin Bjorklund, Joe Clarke,
Toerless Eckert, Stephen Farrell, Stephen Hanna, Wes Hardaker, Radek
Krejci, Russ Mundy, Reinaldo Penno, Randy Presuhn, Max Pritikin,
Michael Richardson, Phil Shafer, Juergen Schoenwaelder.
Special thanks goes to Steve Hanna, Russ Mundy, and Wes Hardaker for
brainstorming the original I-D's solution during the IETF 87 meeting
in Berlin.
13. References
13.1. Normative References
[I-D.ietf-anima-voucher]
Watsen, K., Richardson, M., Pritikin, M., and T. Eckert,
"Voucher Profile for Bootstrapping Protocols", draft-ietf-
anima-voucher-07 (work in progress), January 2018.
[I-D.ietf-netmod-yang-data-ext]
Bierman, A., Bjorklund, M., and K. Watsen, "YANG Data
Extensions", draft-ietf-netmod-yang-data-ext-00 (work in
progress), February 2018.
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[ITU.X690.1994]
International Telecommunications 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, 1994.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
C., and M. Carney, "Dynamic Host Configuration Protocol
for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
2003, <https://www.rfc-editor.org/info/rfc3315>.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
DOI 10.17487/RFC3396, November 2002,
<https://www.rfc-editor.org/info/rfc3396>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC5652] Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,
RFC 5652, DOI 10.17487/RFC5652, September 2009,
<https://www.rfc-editor.org/info/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/info/rfc6020>.
[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/info/rfc6125>.
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[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
<https://www.rfc-editor.org/info/rfc7227>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[Std-802.1AR-2009]
IEEE SA-Standards Board, "IEEE Standard for Local and
metropolitan area networks - Secure Device Identity",
December 2009, <http://standards.ieee.org/findstds/
standard/802.1AR-2009.html>.
13.2. Informative References
[I-D.ietf-netconf-keystore]
Watsen, K., "YANG Data Model for a "Keystore" Mechanism",
draft-ietf-netconf-keystore-04 (work in progress), October
2017.
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[I-D.ietf-netmod-yang-tree-diagrams]
Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
ietf-netmod-yang-tree-diagrams-06 (work in progress),
February 2018.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/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/info/rfc5246>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536,
DOI 10.17487/RFC6536, March 2012,
<https://www.rfc-editor.org/info/rfc6536>.
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
2012, <https://www.rfc-editor.org/info/rfc6698>.
[RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A.,
Galperin, S., and C. Adams, "X.509 Internet Public Key
Infrastructure Online Certificate Status Protocol - OCSP",
RFC 6960, DOI 10.17487/RFC6960, June 2013,
<https://www.rfc-editor.org/info/rfc6960>.
[RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home",
RFC 8071, DOI 10.17487/RFC8071, February 2017,
<https://www.rfc-editor.org/info/rfc8071>.
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Appendix A. Promoting a Connection from Untrusted to Trusted
The following diagram illustrates a sequence of bootstrapping
activities that promote an untrusted connection to a bootstrap server
to a trusted connection to the same bootstrap server. This enables a
device to limit the amount of information it might disclose to an
adversary hosting an untrusted bootstrap server.
+----------+
|Deployment|
| Specific |
+------+ |Bootstrap |
|Device| | Server |
+------+ +----------+
| |
| 1. "HTTPS" Request ('untrusted-connection', nonce) |
|------------------------------------------------------->|
| 2. "HTTPS" Response (signed redirect information) |
|<-------------------------------------------------------|
| |
| |
| 3. HTTPS Request (os-name=xyz, os-version=123, etc.) |
|------------------------------------------------------->|
| 4. HTTPS Response (unsigned onboarding information |
|<-------------------------------------------------------|
| |
The interactions in the above diagram are described below.
1. The device initiates an untrusted connection to a bootstrap
server, as is indicated by putting "HTTPS" in double quotes
above. It is still an HTTPS connection, but the device is unable
to authenticate the bootstrap server's TLS certificate. Because
the device is unable to trust the bootstrap server, it sends the
'untrusted-connection' input parameter, and optionally also the
'nonce' input parameter, in the 'get-bootstrapping-data' RPC.
The 'untrusted-connection' parameter informs the bootstrap server
that the device does not trust it and may be holding back some
additional input parameters from the server (e.g., other input
parameters, progress reports, etc.). The 'nonce' input parameter
enables the bootstrap server to dynamically obtain an ownership
voucher from a MASA, which may be important for devices that do
not have a reliable clock.
2. The bootstrap server, seeing the 'untrusted-connection' input
parameter, knows that it can either send unsigned redirect
information or signed data of any type. But, in this case, the
bootstrap server has the ability to sign data and chooses to
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respond with signed redirect information, not signed onboarding
information as might be expected, securely redirecting the device
back to it again. Not displayed but, if the 'nonce' input
parameter was passed, the bootstrap server could dynamically
connect to a download a voucher from the MASA having the nonce
value in it. Details regarding a protocol enabling this
integration is outside the scope of this document.
3. Upon validating the signed redirect information, the device
establishes a secure connection to the bootstrap server.
Unbeknownst to the device, it is the same bootstrap server it was
connected to previously but, because the device is able to
authenticate the bootstrap server tis time, it sends its normal
'get-bootstrapping-data' request (i.e., with additional input
parameters) as well as its progress reports (not depicted).
4. This time, because the 'untrusted-connection' parameter was not
passed, having access to all of the device's input parameters,
the bootstrap server returns unsigned onboarding information to
the device.
Appendix B. Workflow Overview
The zero touch solution presented in this document is conceptualized
to be composed of the non-normative workflows described in this
section. Implementation details are expected to vary. Each diagram
is followed by a detailed description of the steps presented in the
diagram, with further explanation on how implementations may vary.
B.1. Enrollment and Ordering Devices
The following diagram illustrates key interactions that may occur
from when a prospective owner enrolls in a manufacturer's zero touch
program to when the manufacturer ships devices for an order placed by
the prospective owner.
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+-----------+
+------------+ |Prospective| +---+
|Manufacturer| | Owner | |NMS|
+------------+ +-----------+ +---+
| | |
| | |
| 1. initiate enrollment | |
#<-----------------------------| |
# | |
# | |
# IDevID trust anchor | |
#-----------------------------># set IDevID trust anchor |
# #--------------------------->|
# | |
# bootstrap server | |
# account credentials | |
#-----------------------------># set credentials |
| #--------------------------->|
| | |
| | |
| 2. set owner certificate trust anchor |
|<----------------------------------------------------------|
| | |
| | |
| 3. place device order | |
|<-----------------------------# model devices |
| #--------------------------->|
| | |
| 4. ship devices and send | |
| device identifiers and | |
| ownership vouchers | |
|-----------------------------># set device identifiers |
| # and ownership vouchers |
| #--------------------------->|
| | |
Each numbered item below corresponds to a numbered item in the
diagram above.
1. A prospective owner of a manufacturer's devices initiates an
enrollment process with the manufacturer. This process includes
the following:
* Regardless how the prospective owner intends to bootstrap
their devices, they will always obtain from the manufacturer
the trust anchor certificate for the IDevID certificates.
This certificate will is installed on the prospective owner's
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NMS so that the NMS can authenticate the IDevID certificates
when they're presented to subsequent steps.
* If the manufacturer hosts an Internet based bootstrap server
(e.g., a redirect server) such as described in Section 4.4,
then credentials necessary to configure the bootstrap server
would be provided to the prospective owner. If the bootstrap
server is configurable through an API (outside the scope of
this document), then the credentials might be installed on the
prospective owner's NMS so that the NMS can subsequently
configure the manufacturer-hosted bootstrap server directly.
2. If the manufacturer's devices are able to validate signed data
(Section 5.4), and assuming that the prospective owner's NMS is
able to prepare and sign the bootstrapping data itself, the
prospective owner's NMS might set a trust anchor certificate onto
the manufacturer's bootstrap server, using the credentials
provided in the previous step. This certificate is the trust
anchor certificate that the prospective owner would like the
manufacturer to place into the ownership vouchers it generates,
thereby enabling devices to trust the owner's owner certificate.
How this trust anchor certificate is used to enable devices to
validate signed bootstrapping data is described in Section 5.4.
3. Some time later, the prospective owner places an order with the
manufacturer, perhaps with a special flag checked for zero touch
handling. At this time, or perhaps before placing the order, the
owner may model the devices in their NMS, creating virtual
objects for the devices with no real-world device associations.
For instance the model can be used to simulate the device's
location in the network and the configuration it should have when
fully operational.
4. When the manufacturer fulfills the order, shipping the devices to
their intended locations, they may notify the owner of the
devices's serial numbers and shipping destinations, which the
owner may use to stage the network for when the devices power on.
Additionally, the manufacturer may send one or more ownership
vouchers, cryptographically assigning ownership of those devices
to the owner. The owner may set this information on their NMS,
perhaps binding specific modeled devices to the serial numbers
and ownership vouchers.
B.2. Owner Stages the Network for Bootstrap
The following diagram illustrates how an owner might stage the
network for bootstrapping devices.
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+----------+ +------------+
|Deployment| |Manufacturer| +------+ +------+
| Specific | | Hosted | | Local| | Local| +---------+
+---+ |Bootstrap | | Bootstrap | | DNS | | DHCP | |Removable|
|NMS| | Server | | Server | |Server| |Server| | Storage |
+---+ +----------+ +------------+ +------+ +------+ +---------+
| | | | | |
1. | | | | | |
activate| | | | | |
modeled | | | | | |
device | | | | | |
------->| | | | | |
| 2. (optional) | | | |
| configure | | | |
| bootstrap | | | |
| server | | | |
|------->| | | | |
| | | | | |
| 3. (optional) configure | | |
| bootstrap server | | | |
|--------------------->| | | |
| | | | | |
| | | | | |
| 4. (optional) configure DNS server| | |
|---------------------------------->| | |
| | | | | |
| | | | | |
| 5. (optional) configure DHCP server | |
|------------------------------------------->| |
| | | | | |
| | | | | |
| 6. (optional) store bootstrapping artifacts on media |
|----------------------------------------------------->|
| | | | | |
| | | | | |
Each numbered item below corresponds to a numbered item in the
diagram above.
1. Having previously modeled the devices, including setting their
fully operational configurations and associating device serial
numbers and (optionally) ownership vouchers, the owner might
"activate" one or more modeled devices. That is, the owner tells
the NMS to perform the steps necessary to prepare for when the
real-world devices power up and initiate the bootstrapping
process. Note that, in some deployments, this step might be
combined with the last step from the previous workflow. Here it
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is depicted that an NMS performs the steps, but they may be
performed manually or through some other mechanism.
2. If it is desired to use a deployment specific bootstrap server,
it must be configured to provide the bootstrapping information
for the specific devices. Configuring the bootstrap server may
occur via a programmatic API not defined by this document.
Illustrated here as an external component, the bootstrap server
may be implemented as an internal component of the NMS itself.
3. If it is desired to use a manufacturer hosted bootstrap server,
it must be configured to provide the bootstrapping information
for the specific devices. The configuration must be either
redirect or onboarding information. That is, either the
manufacturer hosted bootstrap server will redirect the device to
another bootstrap server, or provide the device with the
onboarding information itself. The types of bootstrapping
information the manufacturer hosted bootstrap server supports may
vary by implementation; some implementations may only support
redirect information, or only support onboarding information, or
support both redirect and onboarding information. Configuring
the bootstrap server may occur via a programmatic API not defined
by this document.
4. If it is desired to use a DNS server to supply bootstrapping
information, a DNS server needs to be configured. If multicast
DNS-SD is desired, then the server must reside on the local
network, otherwise the DNS server may reside on a remote network.
Please see Section 4.2 for more information about how to
configure DNS servers. Configuring the DNS server may occur via
a programmatic API not defined by this document.
5. If it is desired to use a DHCP server to supply bootstrapping
data, a DHCP server needs to be configured. The DHCP server may
be accessed directly or via a DHCP relay. Please see Section 4.3
for more information about how to configure DHCP servers.
Configuring the DHCP server may occur via a programmatic API not
defined by this document.
6. If it is desired to use a removable storage device (e.g., USB
flash drive) to supply bootstrapping information, the information
would need to be placed onto it. Please see Section 4.1 for more
information about how to configure a removable storage device.
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B.3. Device Powers On
The following diagram illustrates the sequence of activities that
occur when a device powers on.
+----------+
+-----------+ |Deployment|
| Source of | | Specific |
+------+ | Bootstrap | |Bootstrap | +---+
|Device| | Data | | Server | |NMS|
+------+ +-----------+ +----------+ +---+
| | | |
| | | |
| 1. if zerotouch bootstrap service | | |
| is not enabled, then exit. | | |
| | | |
| 2. for each source supported, check | | |
| for bootstrapping data. | | |
|------------------------------------>| | |
| | | |
| 3. if onboarding information found, | | |
| initialize self and, only if | | |
| source is a bootstrap server, | | |
| send progress updates. | | |
|------------------------------------># | |
| # webhook | |
| #----------------------->|
| | |
| 4. else if redirect-information found, for each | |
| bootstrap server specified, check for data. | |
|-+------------------------------------------------->| |
| | | |
| | if more redirect-information is found, recurse | |
| | (not depicted), else if onboarding-information | |
| | found, initialize self and post progress reports | |
| +-------------------------------------------------># |
| # webhook |
| #-------->|
|
| 5. retry sources and/or wait for manual provisioning.
|
The interactions in the above diagram are described below.
1. Upon power being applied, the device checks to see if zerotouch
bootstrapping is configured, such as must be the case when
running its "factory default" configuration. If zerotouch
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bootstrapping is not configured, then the bootstrapping logic
exits and none of the following interactions occur.
2. For each source of bootstrapping data the device supports,
preferably in order of closeness to the device (e.g., removable
storage before Internet based servers), the device checks to see
if there is any bootstrapping data for it there.
3. If onboarding information is found, the device initializes itself
accordingly (e.g., installing a boot-image and committing an
initial configuration). If the source is a bootstrap server, and
the bootstrap server can be trusted (i.e., TLS-level
authentication), the device also sends progress reports to the
bootstrap server.
* The contents of the initial configuration should configure an
administrator account on the device (e.g., username, ssh-rsa
key, etc.), and should configure the device either to listen
for NETCONF or RESTCONF connections or to initiate call home
connections [RFC8071], and should disable the zerotouch
bootstrapping service (e.g., the 'enabled' leaf in data model
presented in Section 8).
* If the bootstrap server supports forwarding device progress
reports to external systems (e.g., via a webhook), a
"bootstrap-complete" progress report (Section 7.3) informs the
external system to know when it can, for instance, initiate a
connection to the device. To support this scenario further,
the 'bootstrap-complete' progress report may also relay the
device's SSH host keys and/or TLS certificates, with which the
external system can use to authenticate subsequent connections
to the device.
If the device successfully completes the bootstrapping process,
it exits the bootstrapping logic without considering any
additional sources of bootstrapping data.
4. Otherwise, if redirect information is found, the device iterates
through the list of specified bootstrap servers, checking to see
if it has bootstrapping data for the device. If the bootstrap
server returns more redirect information, then the device
processes it recursively. Otherwise, if the bootstrap server
returns onboarding information, the device processes it following
the description provided in (3) above.
5. After having tried all supported sources of bootstrapping data,
the device may retry again all the sources and/or provide
manageability interfaces for manual configuration (e.g., CLI,
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HTTP, NETCONF, etc.). If manual configuration is allowed, and
such configuration is provided, the configuration should also
disable the zerotouch bootstrapping service, as the need for
bootstrapping would no longer be present.
Appendix C. Change Log
C.1. ID to 00
o Major structural update; the essence is the same. Most every
section was rewritten to some degree.
o Added a Use Cases section
o Added diagrams for "Actors and Roles" and "NMS Precondition"
sections, and greatly improved the "Device Boot Sequence" diagram
o Removed support for physical presence or any ability for
configlets to not be signed.
o Defined the Zero Touch Information DHCP option
o Added an ability for devices to also download images from
configuration servers
o Added an ability for configlets to be encrypted
o Now configuration servers only have to support HTTP/S - no other
schemes possible
C.2. 00 to 01
o Added boot-image and validate-owner annotations to the "Actors and
Roles" diagram.
o Fixed 2nd paragraph in section 7.1 to reflect current use of
anyxml.
o Added encrypted and signed-encrypted examples
o Replaced YANG module with XSD schema
o Added IANA request for the Zero Touch Information DHCP Option
o Added IANA request for media types for boot-image and
configuration
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C.3. 01 to 02
o Replaced the need for a configuration signer with the ability for
each NMS to be able to sign its own configurations, using
manufacturer signed ownership vouchers and owner certificates.
o Renamed configuration server to bootstrap server, a more
representative name given the information devices download from
it.
o Replaced the concept of a configlet by defining a southbound
interface for the bootstrap server using YANG.
o Removed the IANA request for the boot-image and configuration
media types
C.4. 02 to 03
o Minor update, mostly just to add an Editor's Note to show how this
draft might integrate with the draft-pritikin-anima-bootstrapping-
keyinfra.
C.5. 03 to 04
o Major update formally introducing unsigned data and support for
Internet-based redirect servers.
o Added many terms to Terminology section.
o Added all new "Guiding Principles" section.
o Added all new "Sources for Bootstrapping Data" section.
o Rewrote the "Interactions" section and renamed it "Workflow
Overview".
C.6. 04 to 05
o Semi-major update, refactoring the document into more logical
parts
o Created new section for information types
o Added support for DNS servers
o Now allows provisional TLS connections
o Bootstrapping data now supports scripts
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o Device Details section overhauled
o Security Considerations expanded
o Filled in enumerations for notification types
C.7. 05 to 06
o Minor update
o Added many Normative and Informative references.
o Added new section Other Considerations.
C.8. 06 to 07
o Minor update
o Added an Editorial Note section for RFC Editor.
o Updated the IANA Considerations section.
C.9. 07 to 08
o Minor update
o Updated to reflect review from Michael Richardson.
C.10. 08 to 09
o Added in missing "Signature" artifact example.
o Added recommendation for manufacturers to use interoperable
formats and file naming conventions for removable storage devices.
o Added configuration-handling leaf to guide if config should be
merged, replaced, or processed like an edit-config/yang-patch
document.
o Added a pre-configuration script, in addition to the post-
configuration script from -05 (issue #15).
C.11. 09 to 10
o Factored ownership voucher and voucher revocation to a separate
document: draft-kwatsen-netconf-voucher. (issue #11)
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o Removed <configuration-handling> options 'edit-config' and 'yang-
patch'. (issue #12)
o Defined how a signature over signed-data returned from a bootstrap
server is processed. (issue #13)
o Added recommendation for removable storage devices to use open/
standard file systems when possible. (issue #14)
o Replaced notifications "script-[warning/error]" with "[pre/post]-
script-[warning/error]". (goes with issue #15)
o switched owner-certificate to be encoded using the PKCS #7 format.
(issue #16)
o Replaced md5/sha1 with sha256 inside a choice statement, for
future extensibility. (issue #17)
o A ton of editorial changes, as I went thru the entire draft with a
fine-toothed comb.
C.12. 10 to 11
o fixed yang validation issues found by IETFYANGPageCompilation.
note: these issues were NOT found by pyang --ietf or by the
submission-time validator...
o fixed a typo in the yang module, someone the config false
statement was removed.
C.13. 11 to 12
o fixed typo that prevented Appendix B from loading the examples
correctly.
o fixed more yang validation issues found by
IETFYANGPageCompilation. note: again, these issues were NOT found
by pyang --ietf or by the submission-time validator...
o updated a few of the notification enumerations to be more
consistent with the other enumerations (following the warning/
error pattern).
o updated the information-type artifact to state how it's encoded,
matching the language that was in Appendix B.
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C.14. 12 to 13
o defined a standalone artifact to encode the old information-type
into a PKCS #7 structure.
o standalone information artifact hardcodes JSON encoding (to match
the voucher draft).
o combined the information and signature PKCS #7 structures into a
single PKCS #7 structure.
o moved the certificate-revocations into the owner-certificate's
PKCS #7 structure.
o eliminated support for voucher-revocations, to reflect the
voucher-draft's switch from revocations to renewals.
C.15. 13 to 14
o Renamed "bootstrap information" to "onboarding information".
o Rewrote DHCP sections to address the packet-size limitation issue,
as discussed in Chicago.
o Added Ian as an author for his text-contributions to the DHCP
sections.
o Removed the Guiding Principles section.
C.16. 14 to 15
o Renamed action 'notification' to 'update-progress' and, likewise
'notification-type' to 'update-type'.
o Updated examples to use "base64encodedvalue==" for binary values.
o Greatly simplified the "Artifact Groupings" section, and moved it
as a subsection to the "Artifacts" section.
o Moved the "Workflow Overview" section to the Appendix.
o Renamed "bootstrap information" to "update information".
o Removed "Other Considerations" section.
o Tons of editorial updates.
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C.17. 15 to 16
o tweaked language to refer to "initial state" rather than "factory
default configuration", so as accommodate white-box scenarios.
o added a paragraph to Intro regarding how the solution primarily
regards physical machines, but could be extended to VMs by a
future document.
o added a pointer to the Workflow Overview section (recently moved
to the Appendix) to the Intro.
o added a note that, in order to simplify the verification process,
the "Zerotouch Information" PKCS #7 structure MUST also contain
the signing X.509 certificate.
o noted that the owner certificate's must either have no Key Usage
or the Key Usage must set the "digitalSignature" bit.
o noted that the owner certificate's subject and subjectAltName
values are not constrained.
o moved/consolidated some text from the Artifacts section down to
the Device Details section.
o tightened up some ambiguous language, for instance, by referring
to specific leaf names in the Voucher artifact.
o reverted a previously overzealous s/unique-id/serial-number/
change.
o modified language for when ZTP runs from when factory-default
config is running to when ZTP is configured, which the factory-
defaults should set .
C.18. 16 to 17
o Added an example for how to promote an untrusted connection to a
trusted connection.
o Added a "query parameters" section defining some parameters
enabling scenarios raised in last call.
o Added a "Disclosing Information to Untrusted Servers" section to
the Security Considerations.
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C.19. 17 to 18
o Added Security Considerations for each YANG module.
o Reverted back to the device always sending its DevID cert.
o Moved data tree to ac'get-bootstrapping-data' RPC.
o Moved the 'update-progress' action to a 'report-progress' RPC.
o Added an 'untrusted-connection' parameter to 'get-bootstrapping-
data' RPC.
o Added the "ietf-zerotouch-device" module.
o Lots of small updates.
C.20. 18 to 19
o Fixed 'must' expressions, by converting 'choice' to a 'list' of
'image-verification', each of which now points to a base identity
called "hash-algorithm". There's just one algorithm currently
defined (sha-256). Wish there was a standard crypto module that
could identify such identities.
C.21. 19 to 20
o Now references I-D.ietf-netmod-yang-tree-diagrams.
o Fixed tree-diagrams in Section 2 to always reflect current YANG
(now they are now dynamically generated).
o The "redirect-information" container's "trust-anchor" is now a CMS
structure that can contain a chain of certificates, rather than a
single certificate.
o The "onboarding-information" container's support for image
verification reworked to be extensible.
o Added a reference to the "Device Details" section to the new
example-zerotouch-device module.
o Clarified that the device must always pass its IDevID certificate,
even for untrusted bootstrap servers.
o Fixed the description statement for the "script" typedef to refer
to the [pre/post]-script-[warning/error] enums, rather than the
legacy script-[warning/error] enums.
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o For the get-bootstrapping-data RPC's input, removed the "remote-
id" and "circuit-id" fields, and added a "hw-model" field.
o Improved DHCP error handling text.
o Added MUST requirement for DHCPv6 client and server implementing
[RFC3396] to handle URI lists longer than 255 octets.
o Changed the "configuration" value in onboarding-information to be
type 'binary' instead of 'anydata'.
o Moved everything from PKCS#7 to CMS (this shows up as a big
change).
o Added the early code point allocation assignments for the DHCP
Options in the IANA Considerations section, and updated the RFC
Editor note accordingly.
o Added RFC Editor request to replace the assigned values for the
CMS content types.
o Relaxed auth requirements from device needing to always send
IDevID cert to device needing to always send authentication
credentials, as this better matches what RFC 8040 Section 2.5
says.
o Moved normative module "ietf-zerotouch-device" to non-normative
module "example-zerotouch-device".
o Updated Title, Abstract, and Introduction per discussion on list.
C.22. 20 to 21
o Now any of the three artifact can be encrypted.
o Fixed some line-too-long issues.
Authors' Addresses
Kent Watsen
Juniper Networks
EMail: kwatsen@juniper.net
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Mikael Abrahamsson
T-Systems
EMail: mikael.abrahamsson@t-systems.se
Ian Farrer
Deutsche Telekom AG
EMail: ian.farrer@telekom.de
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