| 6tisch Working Group | M. Richardson |
| Internet-Draft | Sandelman Software Works |
| Intended status: Informational | P. van der Stok |
| Expires: August 18, 2018 | vanderstok consultancy |
| P. Kampanakis | |
| Cisco Systems | |
| February 14, 2018 |
Constrained Voucher Profile for Bootstrapping Protocols
draft-richardson-anima-ace-constrained-voucher-03
This document defines a strategy to securely assign a pledge to an owner, using an artifact signed, directly or indirectly, by the pledge's manufacturer. This artifact is known as a "voucher".
This document builds upon the work in [I-D.ietf-anima-voucher], encoding the resulting artifact in CBOR. Use with two signature technologies are described.
Additionally, this document explains how constrained vouchers may be transported in the [I-D.vanderstok-ace-coap-est] protocol.
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-Drafts is at https://datatracker.ietf.org/drafts/current/.
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 August 18, 2018.
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 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
Enrollment of new nodes into constrained networks with constrained nodes present unique challenges.
There are bandwidth and code space issues to contend. A solution such as [I-D.ietf-anima-bootstrapping-keyinfra] may be too large in terms of code space or bandwidth required.
This document defines a constrained version of [I-D.ietf-anima-voucher]. Rather than serializing the YANG definition in JSON, it is serialized into CBOR ([RFC7049]).
This document follows a similar, but not identical structure as [I-D.ietf-anima-voucher]. Some sections are left out entirely. Additional sections to [I-D.ietf-anima-voucher] concern: - Addition of voucher-request specification as defined in [I-D.ietf-anima-bootstrapping-keyinfra], - Addition to [I-D.vanderstok-ace-coap-est] of voucher transport requests over coap.
The CBOR definitions for this constrained voucher format are defined using the mechanism describe in [I-D.ietf-core-yang-cbor] using the SID mechanism explained in [I-D.ietf-core-sid]. As the tooling to convert YANG documents into an list of SID keys is still in its infancy, the table of SID values presented here should be considered normative rather than the output of the pyang tool.
Two methods of signing the resulting CBOR object are described in this document. One is CMS [RFC5652]. The other is COSE [RFC8152] signatures.
The following terms are defined in [I-D.ietf-anima-voucher], and are used identically as in that document: artifact, imprint, domain, Join Registrar/Coordinator (JRC), Manufacturer Authorized Signing Authority (MASA), pledge, Trust of First Use (TOFU), and Voucher.
In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 [RFC2119] and indicate requirement levels for compliant STuPiD implementations.
[I-D.ietf-anima-voucher] provides for vouchers that assert proximity, that authenticate the registrar and that include different amounts of anti-replay protection.
This document does not make any extensions to the types of vouchers.
Time based vouchers are included in this definition, but given that constrained devices are extremely unlikely to know the correct time, their use is very unlikely. Most users of these constrained vouchers will be online and will use live nonces to provide anti-replay protection.
[I-D.ietf-anima-voucher] defined only the voucher artifact, and not the Voucher Request artifact, which was defined in [I-D.ietf-anima-bootstrapping-keyinfra].
This document defines both a constrained voucher and a constrained voucher-request. They are presented in the order voucher-request, followed by voucher response as this is the time order that they occur.
This section describes the BRSKI extensions to EST-coaps [I-D.vanderstok-ace-coap-est] to transport the voucher between registrar, proxy and pledge over CoAP.
The extension is targeted to low-resource networks with small packets. Saving header space is important and the EST-coaps URI is shorter than the EST URI.
The presence and location of (path to) the management data are discovered by sending a GET request to "/.well-known/core" including a resource type (RT) parameter with the value "ace.est" [RFC6690]. Upon success, the return payload will contain the root resource of the EST resources. It is up to the implementation to choose its root resource; throughout this document the example root resource /est is used. The example below shows the discovery of the presence and location of voucher resources.
REQ: GET /.well-known/core?rt=ace.est RES: 2.05 Content </est>; rt="ace.est"
The EST-coaps server URIs differ from the EST URI by replacing the scheme https by coaps and by specifying shorter resource path names:
coaps://www.example.com/est/short-name
Figure 5 in section 3.2.2 of [RFC7030] enumerates the operations and corresponding paths which are supported by EST. Table 1 provides the mapping from the BRSKI extension URI path to the EST-coaps URI path.
| BRSKI | EST-coaps |
|---|---|
| /requestvoucher | /rv |
| /voucher-status | /vs |
| /enrollstatus | /es |
| /requestauditlog | /ra |
/requestvoucher and /enrollstatus are needed between pledge and Registrar.
When discovering the root path for the EST resources, the server MAY return the full resource paths and the used content types. This is useful when multiple content types are specified for EST-coaps server. For example, the following more complete response is possible.
REQ: GET /.well-known/core?rt=ace.est RES: 2.05 Content </est>; rt="ace.est" </est/rv>; rt="ace.est";ct=50 TBD2 16 </est/vs>; rt="ace.est";ct=50 </est/es>; rt="ace.est";ct=50 </est/ra>; rt="ace.est";ct= TBD2 16
ct=50 stands for the Content-Format "application/json", ct=16 stands for the Content-Format "application/cose", and ct=TBD2 stands for Content-Format "application/voucher-cms+cbor defined in this document.
The return of the content-types allows the client to choose the most appropriate one from multiple content types.
This section describes the abstract (tree) definition as explained in [I-D.ietf-netmod-yang-tree-diagrams] first. This provides a high-level view of the contents of each artifact.
Then the assigned SID values are presented. These have been assigned using the rules in [I-D.ietf-core-yang-cbor], with an allocation that was made via the http://comi.space service.
((EDNOTE: it is unclear if there is further IANA work))
module: ietf-cwt-voucher-request
grouping voucher-request-cwt-grouping
+---- voucher
+---- created-on
| yang:date-and-time
+---- expires-on?
| yang:date-and-time
+---- assertion
| enumeration
+---- serial-number string
+---- idevid-issuer? binary
+---- pinned-domain-cert binary
+---- domain-cert-revocation-checks? boolean
+---- nonce? binary
+---- last-renewal-date?
| yang:date-and-time
+---- proximity-registrar-subject-public-key-info? binary
[EDNote: the appropriate generation of the SID values is under discussion]
SID Assigned to
--------- --------------------------------------------------
1001150 module ietf-cwt-voucher-request
1001151 module ietf-restconf
1001152 module ietf-voucher
1001153 module ietf-yang-types
1001154 data .../ietf-cwt-voucher-request:voucher
1001155 data .../assertion
1001156 data .../created-on
1001157 data .../domain-cert-revocation-checks
1001158 data .../expires-on
1001159 data .../idevid-issuer
1001160 data .../last-renewal-date
1001161 data .../nonce
1001162 data .../pinned-domain-cert
1001163 data .../proximity-registrar-subject-public-key-info
1001164 data .../serial-number
[EDNote: the appropriate syntax of the module is under discussion]
<CODE BEGINS> file "ietf-cwt-voucher-request@2017-12-11.yang"
/* -*- c -*- */
module ietf-cwt-voucher-request {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-cwt-voucher-request";
prefix "vcwt";
import ietf-voucher {
prefix "v";
}
organization
"IETF 6tisch Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/6tisch/>
WG List: <mailto:6tisch@ietf.org>
Author: Michael Richardson
<mailto:mcr+ietf@sandelman.ca>";
description
"This module defines the format for a voucher, which is produced by
a pledge's manufacturer or delegate (MASA) to securely assign one
or more pledges to an 'owner', so that the pledges may establish a
secure connection to the owner's network infrastructure.
This version provides a very restricted subset appropriate
for very constrained devices.
In particular, it assumes that nonce-ful operation is
always required, that expiration dates are rather weak, as no
clocks can be assumed, and that the Registrar is identified
by a pinned Raw Public Key.
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.";
revision "2017-12-11" {
description
"Initial version";
reference
"RFC XXXX: Voucher Profile for Constrained Devices";
}
// Grouping defined for future usage
grouping voucher-request-cwt-grouping {
description
"Grouping to allow reuse/extensions in future work.";
uses v:voucher-artifact-grouping {
augment "voucher" {
description "Base the CWT voucher-request upon the regular one";
leaf proximity-registrar-subject-public-key-info {
type binary;
description
"The proximity-registrar-subject-public-key-info replaces
the proximit-registrar-cert in constrained uses of
the voucher-request.
The proximity-registrar-subject-public-key-info is the
Raw Public Key of the Registrar. This field is encoded
as specified in RFC7250, section 3.
The ECDSA algorithm MUST be supported.
The EdDSA algorithm as specified in
draft-ietf-tls-rfc4492bis-17 SHOULD be supported.
Support for the DSA algorithm is not recommended.
Support for the RSA algorithm is a MAY.";
}
}
}
}
}
<CODE ENDS>
TBD
The voucher's primary purpose is to securely assign a pledge to an owner. The voucher informs the pledge which entity it should consider to be its owner.
This document defines a voucher that is a CBOR encoded instance of the YANG module defined in Section 5.3 that has been signed with CMS or with COSE.
module: ietf-cwt-voucher
grouping voucher-cwt-grouping
+---- voucher
+---- created-on
| yang:date-and-time
+---- expires-on?
| yang:date-and-time
+---- assertion enumeration
+---- serial-number string
+---- idevid-issuer? binary
+---- pinned-domain-cert binary
+---- domain-cert-revocation-checks? boolean
+---- nonce? binary
+---- last-renewal-date?
| yang:date-and-time
+---- pinned-domain-subject-public-key-info? binary
[EDNote: the appropriate generation of the SID values is under discussion]
SID Assigned to
--------- --------------------------------------------------
1001100 module ietf-cwt-voucher
1001101 module ietf-restconf
1001102 module ietf-voucher
1001103 module ietf-yang-types
1001104 data .../ietf-cwt-voucher:voucher
1001105 data .../assertion
1001106 data .../created-on
1001107 data .../domain-cert-revocation-checks
1001108 data .../expires-on
1001109 data .../idevid-issuer
1001110 data .../last-renewal-date
1001111 data .../nonce
1001112 data .../pinned-domain-cert
1001113 data .../pinned-domain-subject-public-key-info
1001114 data .../serial-number
[EDNote: the appropriate syntax of the module is under discussion]
<CODE BEGINS> file "ietf-cwt-voucher@2017-12-11.yang"
/* -*- c -*- */
module ietf-cwt-voucher {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-cwt-voucher";
prefix "vcwt";
import ietf-voucher {
prefix "v";
}
organization
"IETF 6tisch Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/6tisch/>
WG List: <mailto:6tisch@ietf.org>
Author: Michael Richardson
<mailto:mcr+ietf@sandelman.ca>";
description
"This module defines the format for a voucher, which is produced by
a pledge's manufacturer or delegate (MASA) to securely assign one
or more pledges to an 'owner', so that the pledges may establish a
secure connection to the owner's network infrastructure.
This version provides a very restricted subset appropriate
for very constrained devices.
In particular, it assumes that nonce-ful operation is
always required, that expiration dates are rather weak, as no
clocks can be assumed, and that the Registrar is identified
by a pinned Raw Public Key.
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.";
revision "2017-12-11" {
description
"Initial version";
reference
"RFC XXXX: Voucher Profile for Constrained Devices";
}
// Grouping defined for future usage
grouping voucher-cwt-grouping {
description
"Grouping to allow reuse/extensions in future work.";
uses v:voucher-artifact-grouping {
augment "voucher" {
description "Base the CWT voucher upon the regular one";
leaf pinned-domain-subject-public-key-info {
type binary;
description
"The pinned-domain-subject replaces the
pinned-domain-certificate in constrained uses of
the voucher. The pinned-domain-public-key-info is the
Raw Public Key of the Registrar. This field is encoded
as specified in RFC7250, section 3.
The ECDSA algorithm MUST be supported.
The EdDSA algorithm as specified in
draft-ietf-tls-rfc4492bis-17 SHOULD be supported.
Support for the DSA algorithm is not recommended.
Support for the RSA algorithm is a MAY.";
}
}
}
}
}
<CODE ENDS>
TBD
The IETF evolution of PKCS#7 is CMS [RFC5652]. The CMS signed voucher is much like the equivalent voucher defined in [I-D.ietf-anima-voucher].
A different eContentType of TBD1 is used to indicate that the contents are in a different format than in [I-D.ietf-anima-voucher].
The ContentInfo structure contains a payload consisting of the CBOR encoded voucher. The [I-D.ietf-core-yang-cbor] use of delta encoding creates a canonical ordering for the keys on the wire. This canonical ordering is not important as there is no expectation that the content will be reproduced during the validation process.
Normally the recipient is the pledge and the signer is the MASA.
[I-D.ietf-anima-bootstrapping-keyinfra] supports both signed and unsigned voucher requests from the pledge to the JRC. In this specification, voucher-request artifact is not signed from the pledge to the registrar. From the JRC to the MASA, the voucher-request artifact MUST be signed by the domain owner key which is requesting ownership.
The considerations of [RFC5652] section 5.1, concerning validating CMS objects which are really PKCS7 objects (cmsVersion=1) applies.
The CMS structure SHOULD also contain all the certificates leading up to and including the signer's trust anchor certificate known to the recipient. The inclusion of the trust anchor is unusual in many applications, but without it third parties can not accurately audit the transaction.
The CMS structure MAY also contain revocation objects for any intermediate certificate authorities (CAs) between the voucher-issuer and the trust anchor known to the recipient. However, the use of CRLs and other validity mechanisms is discouraged, as the pledge is unlikely to be able to perform online checks, and is unlikely to have a trusted clock source. As described below, the use of short-lived vouchers and/or pledge provided nonce provides a freshness guarantee.
This section to be added.
The design considerations for the CBOR encoding of vouchers is much the same as for [I-D.ietf-anima-voucher].
One key difference is that the names of the leaves in the YANG does not have a material effect on the size of the resulting CBOR, as the SID translation process assigns integers to the names.
TBD.
TBD.
TBD.
This document registers two URIs in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registration is requested:
URI: urn:ietf:params:xml:ns:yang:ietf-cwt-voucher Registrant Contact: The ANIMA WG of the IETF. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-cwt-voucher-request Registrant Contact: The ANIMA WG of the IETF. XML: N/A, the requested URI is an XML namespace.
This document registers two YANG modules in the YANG Module Names registry [RFC6020]. Following the format defined in [RFC6020], the the following registration is requested:
name: ietf-cwt-voucher namespace: urn:ietf:params:xml:ns:yang:ietf-cwt-voucher prefix: vch reference: RFC XXXX name: ietf-cwt-voucher-request namespace: urn:ietf:params:xml:ns:yang:ietf-cwt-voucher-request prefix: vch reference: RFC XXXX
This document registers an OID in the "SMI Security for S/MIME CMS Content Type" registry (1.2.840.113549.1.9.16.1), with the value:
Decimal Description References ------- -------------------------------------- ---------- TBD1 id-ct-animaCBORVoucher [ThisRFC]
EDNOTE: should a separate value be used for Voucher Requests?
The SID range 1001100 was allocated by comi.space to the IETF-CWT-VOUCHER yang module.
The SID range 1001150 was allocated by comi.space to the IETF-CWT-VOUCHER-REQUEST yang module.
EDNOTE: it is unclear if there is further IANA work required.
This section registers the 'application/voucher-cms+cbor' media type in the "Media Types" registry. These media types are used to indicate that the content is a CBOR voucher signed with a cms structure.
Type name: application Subtype name: voucher-cms+cbor Required parameters: none Optional parameters: none Encoding considerations: CMS-signed CBOR vouchers are CBOR encoded. Security considerations: See Security Considerations, Section Interoperability considerations: The format is designed to be broadly interoperable. Published specification: THIS RFC. Applications that use this media type: ANIMA, 6tisch, and other zero-touch imprinting systems Additional information: Magic number(s): None File extension(s): .cbor Macintosh file type code(s): none Person & email address to contact for further information: IETF ANIMA WG Intended usage: LIMITED Restrictions on usage: NONE Author: ANIMA WG Change controller: IETF Provisional registration? (standards tree only): NO
Additions to the sub-registry "CoAP Content-Formats", within the "CoRE Parameters" registry are needed for the below media types. These can be registered either in the Expert Review range (0-255) or IETF Review range (256-9999). Addition: Type name: application Subtype name: voucher-cms+cbor ID: TBD2 Required parameters: None Optional parameters: None Encoding considerations: CBOR Security considerations: As defined in this specification Published specification: this document Applications that use this media type: ANIMA bootstrap (BRSKI)
TBD
| [I-D.ietf-ace-cbor-web-token] | Jones, M., Wahlstroem, E., Erdtman, S. and H. Tschofenig, "CBOR Web Token (CWT)", Internet-Draft draft-ietf-ace-cbor-web-token-12, February 2018. |
| [I-D.ietf-anima-bootstrapping-keyinfra] | Pritikin, M., Richardson, M., Behringer, M., Bjarnason, S. and K. Watsen, "Bootstrapping Remote Secure Key Infrastructures (BRSKI)", Internet-Draft draft-ietf-anima-bootstrapping-keyinfra-09, October 2017. |
| [I-D.ietf-anima-voucher] | Watsen, K., Richardson, M., Pritikin, M. and T. Eckert, "Voucher Profile for Bootstrapping Protocols", Internet-Draft draft-ietf-anima-voucher-07, January 2018. |
| [I-D.ietf-core-object-security] | Selander, G., Mattsson, J., Palombini, F. and L. Seitz, "Object Security for Constrained RESTful Environments (OSCORE)", Internet-Draft draft-ietf-core-object-security-08, January 2018. |
| [I-D.ietf-core-sid] | Veillette, M. and A. Pelov, "YANG Schema Item iDentifier (SID)", Internet-Draft draft-ietf-core-sid-03, December 2017. |
| [I-D.ietf-core-yang-cbor] | Veillette, M., Pelov, A., Somaraju, A., Turner, R. and A. Minaburo, "CBOR Encoding of Data Modeled with YANG", Internet-Draft draft-ietf-core-yang-cbor-06, February 2018. |
| [I-D.vanderstok-ace-coap-est] | Stok, P., Kampanakis, P., Kumar, S., Richardson, M., Furuhed, M. and S. Raza, "EST over secure CoAP (EST-coaps)", Internet-Draft draft-vanderstok-ace-coap-est-04, January 2018. |
| [ieee802-1AR] | IEEE Standard, ., "IEEE 802.1AR Secure Device Identifier", 2009. |
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [RFC5652] | Housley, R., "Cryptographic Message Syntax (CMS)", STD 70, RFC 5652, DOI 10.17487/RFC5652, September 2009. |
| [RFC7049] | Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013. |
| [RFC7250] | Wouters, P., Tschofenig, H., Gilmore, J., Weiler, S. and T. Kivinen, "Using Raw Public Keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, June 2014. |
| [RFC8152] | Schaad, J., "CBOR Object Signing and Encryption (COSE)", RFC 8152, DOI 10.17487/RFC8152, July 2017. |
| [duckling] | Stajano, F. and R. Anderson, "The resurrecting duckling: security issues for ad-hoc wireless networks", 1999. |
| [I-D.ietf-netmod-yang-tree-diagrams] | Bjorklund, M. and L. Berger, "YANG Tree Diagrams", Internet-Draft draft-ietf-netmod-yang-tree-diagrams-06, February 2018. |
| [pledge] | Dictionary.com, ., "Dictionary.com Unabridged", 2015. |
| [RFC6690] | Shelby, Z., "Constrained RESTful Environments (CoRE) Link Format", RFC 6690, DOI 10.17487/RFC6690, August 2012. |
| [RFC7030] | Pritikin, M., Yee, P. and D. Harkins, "Enrollment over Secure Transport", RFC 7030, DOI 10.17487/RFC7030, October 2013. |
This section extends the examples from Appendix A of [I-D.vanderstok-ace-coap-est]. The CoAP headers are only worked out for the enrollstatus example.
A coaps enrollstatus message can be :
GET coaps://[192.0.2.1:8085]/est/es
The corresponding coap header fields are shown below.
Ver = 1
T = 0 (CON)
Code = 0x01 (0.01 is GET)
Options
Option1 (Uri-Host)
Option Delta = 0x3 (option nr = 3)
Option Length = 0x9
Option Value = 192.0.2.1
Option2 (Uri-Port)
Option Delta = 0x4 (option nr = 4+3=7)
Option Length = 0x4
Option Value = 8085
Option3 (Uri-Path)
Option Delta = 0x4 (option nr = 7+4= 11)
Option Length = 0x7
Option Value = /est/es
Payload = [Empty]
A 2.05 Content response with an unsigned JSON voucher (ct=50) will then be:
2.05 Content (Content-Format: application/json)
{payload}
With CoAP fields and payload:
Ver=1
T=2 (ACK)
Code = 0x45 (2.05 Content)
Options
Option1 (Content-Format)
Option Delta = 0xC (option nr 12)
Option Length = 0x2
Option Value = 0x32 (application/json)
Payload =
[EDNOTE: put here voucher payload ]
A coaps voucher_status message can be :
GET coaps://[2001:db8::2:1]:61616]/est/vs
A 2.05 Content response with a non signed JSON voucher (ct=50) will then be:
2.05 Content (Content-Format: application/json)
Payload =
[EDNOTE: put here voucher payload ]
A coaps requestvoucher message can be :
GET coaps://[2001:db8::2:1]:61616]/est/rv
A 2.05 Content response returning CBOR voucher signed with a cms structure(ct=TBD2) will then be:
2.05 Content (Content-Format: application/voucher-cms+cbor)
Payload =
[EDNOTE: put here encrypted voucher payload ]
A coaps requestauditing message can be :
GET coaps://[2001:db8::2:1]:61616]/est/ra
A 2.05 Content response with a COSE voucher (ct=16) will then be:
2.05 Content (Content-Format: application/cose)
Payload =
[EDNOTE: put here COSE voucher payload ]