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Internet 6tisch Working Group Internet-Draft 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 , 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 protocol.

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 may be too large in terms of code space or bandwidth required. This document defines a constrained version of . Rather than serializing the YANG definition in JSON, it is serialized into CBOR (). This document follows a similar, but not identical structure as . Some sections are left out entirely. Additional sections to concern: - Addition of voucher-request specification as defined in , - Addition to of voucher transport requests over coap. The CBOR definitions for this constrained voucher format are defined using the mechanism describe in using the SID mechanism explained in . 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 . The other is COSE signatures.

The following terms are defined in , 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 and indicate requirement levels for compliant STuPiD implementations.

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. defined only the voucher artifact, and not the Voucher Request artifact, which was defined in . 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 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" . 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.

; 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:

Figure 5 in section 3.2.2 of enumerates the operations and corresponding paths which are supported by EST. 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.

; rt="ace.est" ; rt="ace.est";ct=50 TBD2 16 ; rt="ace.est";ct=50 ; rt="ace.est";ct=50 ; 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 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 , with an allocation that was made via the http://comi.space service. ((EDNOTE: it is unclear if there is further IANA work))

[EDNote: the appropriate generation of the SID values is under discussion]

[EDNote: the appropriate syntax of the module is under discussion]

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: WG List: Author: Michael Richardson "; 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."; } } } } } ]]>

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.

[EDNote: the appropriate generation of the SID values is under discussion]

[EDNote: the appropriate syntax of the module is under discussion]

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: WG List: Author: Michael Richardson "; 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."; } } } } } ]]>

TBD

The IETF evolution of PKCS#7 is CMS . The CMS signed voucher is much like the equivalent voucher defined in . A different eContentType of TBD1 is used to indicate that the contents are in a different format than in . The ContentInfo structure contains a payload consisting of the CBOR encoded voucher. The 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. 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 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 . 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:

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:

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:

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.

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

&RFC2119; &RFC7049; &I-D.ietf-core-yang-cbor; &I-D.ietf-core-sid; &RFC7250; &RFC5652; &RFC8152; &I-D.ietf-anima-voucher; &I-D.ietf-anima-bootstrapping-keyinfra; &I-D.ietf-core-object-security; &I-D.ietf-ace-cbor-web-token; &I-D.vanderstok-ace-coap-est; &I-D.ietf-netmod-yang-tree-diagrams; &RFC6690; &RFC7030;

This section extends the examples from Appendix A of . The CoAP headers are only worked out for the enrollstatus example.

A coaps enrollstatus message can be :

The corresponding coap header fields are shown below.

A 2.05 Content response with an unsigned JSON voucher (ct=50) will then be:

With CoAP fields and payload:

A coaps voucher_status message can be :

A 2.05 Content response with a non signed JSON voucher (ct=50) will then be:

A coaps requestvoucher message can be :

A 2.05 Content response returning CBOR voucher signed with a cms structure(ct=TBD2) will then be:

A coaps requestauditing message can be :

A 2.05 Content response with a COSE voucher (ct=16) will then be: