| Internet-Draft | CDDL models for some existing RFCs | August 2024 |
| Bormann | Expires 28 February 2025 | [Page] |
A number of CBOR- and JSON-based protocols have been defined before CDDL was standardized or widely used.¶
This short draft records some CDDL definitions for such protocols, which could become part of a library of CDDL definitions available for use in CDDL2 processors. It focuses on CDDL in (almost) published IETF RFCs.¶
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 28 February 2025.¶
Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
(Please see abstract.) Add in [STD94] [STD90] [RFC8610] [RFC9165] [I-D.ietf-cbor-cddl-more-control]¶
This section is intended to have one subsection for each CDDL data model presented for an existing RFC. As a start, it is fleshed out with three such data models.¶
Appendix H of [RFC8610] contains two CDDL definitions for [RFC7071], which are not copied here. Typically, the compact form would be used in applications using the RFC 7071 format; while the extended form might be useful to cherry-pick features of RFC 7071 into another protocol.¶
[RFC8366] defines a data model for a "Voucher Artifact", which can be represented in CDDL as:¶
voucher-artifact = {
"ietf-voucher:voucher": {
created-on: yang$date-and-time
? (
expires-on: yang$date-and-time
? last-renewal-date: yang$date-and-time
//
nonce: json-binary<bytes .size (8..32)>
)
assertion: assertion
serial-number: text
? idevid-issuer: json-binary<bytes>
pinned-domain-cert: json-binary<bytes>
? domain-cert-revocation-checks: bool
}
}
assertion = "verified" / "logged" / "proximity"
yang$date-and-time = text .regexp cat3<"[0-9]{4}-[0-9]{2}-[0-9]{2}T",
"[0-9]{2}:[0-9]{2}:[0-9]{2}([.][0-9]+)?",
"(Z|[+-][0-9]{2}:[0-9]{2})">
cat3<A,B,C> = (A .cat B) .cat C
json-binary<T> = text .b64c T
¶
The two examples in the RFC can be validated with this little patchup script:¶
sed -e s/ue=/uQ=/ -e s/'"true"'/true/ | cddl rfc8366.cddl vp -¶
[RFC9457] defines a simple data model that is reproduced in CDDL here:¶
problem-object = {
? type: preferably-absolute-uri
? title: text
? status: 100..599
? detail: text
? instance: preferably-absolute-uri
* text .feature "problem-object-extension" => any
}
; RECOMMENDED: absolute URI or at least absolute path:
preferably-absolute-uri = ~uri
¶
Note that Appendix B of [RFC9290] also defines a CBOR-specific data model that may be useful for tunneling [RFC7807] or [RFC9457] problem details in [RFC9290] Concise Problem Details.¶
[RFC9595] defines a data model for a "SID file" in YANG, to be transported as a YANG-JSON instance.¶
An equivalent CDDL data model is given here:¶
sid-file = {
"ietf-sid-file:sid-file": {
module-name: yang$yang-identifier
? module-revision: revision-identifier
? sid-file-version: sid-file-version-identifier
? sid-file-status: "unpublished" / "published"
? description: text
? dependency-revision: [* dependency-revision]
? assignment-range: [* assignment-range]
? item: [*item]
}
}
rep<RE>=cat3<"(", RE, ")*">
opt<RE>=cat3<"(", RE, ")?">
cat3<A,B,C> = (A .cat B) .cat C
id-re = "[a-zA-Z_][a-zA-Z0-9\\-_.]*"
yang$yang-identifier = text .regexp id-re
revision-identifier = text .regexp "[0-9]{4}-[0-9]{2}-[0-9]{2}"
sid-file-version-identifier = uint .size 4
sid = text .decimal (0..0x7fffffffffffffff); uint63 as text string
plus-id<Prefix> = Prefix .cat id-re
schema-node-re = cat3<plus-id<"/">, plus-id<":">, ; qualified
rep<plus-id<"/"> .cat ; optionally
opt<plus-id<":">> > > ; qualified
schema-node-path = text .regexp schema-node-re
dependency-revision = {
module-name: yang$yang-identifier
module-revision: revision-identifier
}
assignment-range = {
entry-point: sid
size: sid
}
item = {
? status: "stable" / "unstable" / "obsolete"
(
namespace: "module" / "identity" / "feature"
identifier: yang$yang-identifier
//
namespace: "data"
identifier: schema-node-path
)
sid: sid
}
¶
Often, CDDL models need to use numbers that have been registered as values in IANA registries.¶
This section is intended to have one subsection for each CDDL data model presented that is derived from an existing IANA registry. As a start, it is fleshed out with one such data model.¶
The intention is that these reference modules are update automatically (after each change of the registry or periodically, frequent enough.) Hence, this document can only present a snapshot for IANA-derived data models.¶
The model(s) presented here clearly are in proof-of-concept stage; suggestions for improvement are very welcome.¶
The IANA registry for COSE Algorithms is part of the IANA cose registry group [IANA.cose].¶
The following automatically derived model defines some 70 CDDL rules that have the name for a COSE algorithm as its rule name and the actual algorithm number as its right hand side. The additional first rule is a type choice between all these constants; this could be used in places that just have to validate the presence of a COSE algorithm number that was registered at the time the model was derived.¶
This section does not explore potential filtering of the registry entries, e.g., by recommended status (such as leaving out deprecated entries) or by capabilities.¶
The names given in the COSE algorithms registry are somewhat irregular
and do not consider their potential use in modeling or programming
languages; the automatic derivation used here turns sequences of one
or more spaces and other characters that cannot be in CDDL names
([/+] here) into underscores.¶
============= NOTE: '\' line wrapping per RFC 8792 ============== algorithms = RS1 / A128CTR / A192CTR / A256CTR / A128CBC / \ A192CBC / A256CBC / WalnutDSA / RS512 / RS384 / RS256 / \ ES256K / HSS-LMS / SHAKE256 / SHA-512 / SHA-384 / RSAES-\ OAEP_w_SHA-512 / RSAES-OAEP_w_SHA-256 / RSAES-\ OAEP_w_RFC_8017_default_parameters / PS512 / PS384 / PS256 / \ ES512 / ES384 / ECDH-SS_A256KW / ECDH-SS_A192KW / ECDH-\ SS_A128KW / ECDH-ES_A256KW / ECDH-ES_A192KW / ECDH-ES_A128KW \ / ECDH-SS_HKDF-512 / ECDH-SS_HKDF-256 / ECDH-ES_HKDF-512 / \ ECDH-ES_HKDF-256 / SHAKE128 / SHA-512_256 / SHA-256 / SHA-\ 256_64 / SHA-1 / direct_HKDF-AES-256 / direct_HKDF-AES-128 / \ direct_HKDF-SHA-512 / direct_HKDF-SHA-256 / EdDSA / ES256 / \ direct / A256KW / A192KW / A128KW / A128GCM / A192GCM / \ A256GCM / HMAC_256_64 / HMAC_256_256 / HMAC_384_384 / \ HMAC_512_512 / AES-CCM-16-64-128 / AES-CCM-16-64-256 / AES-CCM\ -64-64-128 / AES-CCM-64-64-256 / AES-MAC_128_64 / AES-\ MAC_256_64 / ChaCha20_Poly1305 / AES-MAC_128_128 / AES-\ MAC_256_128 / AES-CCM-16-128-128 / AES-CCM-16-128-256 / AES-\ CCM-64-128-128 / AES-CCM-64-128-256 / IV-GENERATION RS1 = -65535 A128CTR = -65534 A192CTR = -65533 A256CTR = -65532 A128CBC = -65531 A192CBC = -65530 A256CBC = -65529 WalnutDSA = -260 RS512 = -259 RS384 = -258 RS256 = -257 ES256K = -47 HSS-LMS = -46 SHAKE256 = -45 SHA-512 = -44 SHA-384 = -43 RSAES-OAEP_w_SHA-512 = -42 RSAES-OAEP_w_SHA-256 = -41 RSAES-OAEP_w_RFC_8017_default_parameters = -40 PS512 = -39 PS384 = -38 PS256 = -37 ES512 = -36 ES384 = -35 ECDH-SS_A256KW = -34 ECDH-SS_A192KW = -33 ECDH-SS_A128KW = -32 ECDH-ES_A256KW = -31 ECDH-ES_A192KW = -30 ECDH-ES_A128KW = -29 ECDH-SS_HKDF-512 = -28 ECDH-SS_HKDF-256 = -27 ECDH-ES_HKDF-512 = -26 ECDH-ES_HKDF-256 = -25 SHAKE128 = -18 SHA-512_256 = -17 SHA-256 = -16 SHA-256_64 = -15 SHA-1 = -14 direct_HKDF-AES-256 = -13 direct_HKDF-AES-128 = -12 direct_HKDF-SHA-512 = -11 direct_HKDF-SHA-256 = -10 EdDSA = -8 ES256 = -7 direct = -6 A256KW = -5 A192KW = -4 A128KW = -3 A128GCM = 1 A192GCM = 2 A256GCM = 3 HMAC_256_64 = 4 HMAC_256_256 = 5 HMAC_384_384 = 6 HMAC_512_512 = 7 AES-CCM-16-64-128 = 10 AES-CCM-16-64-256 = 11 AES-CCM-64-64-128 = 12 AES-CCM-64-64-256 = 13 AES-MAC_128_64 = 14 AES-MAC_256_64 = 15 ChaCha20_Poly1305 = 24 AES-MAC_128_128 = 25 AES-MAC_256_128 = 26 AES-CCM-16-128-128 = 30 AES-CCM-16-128-256 = 31 AES-CCM-64-128-128 = 32 AES-CCM-64-128-256 = 33 IV-GENERATION = 34¶
This document makes no requests of IANA.¶
However, the use of IANA registries for deriving CDDL (e.g., as in Section 3) is an active subject of discussion.¶
The security considerations of [RFC8610], [RFC9165], [I-D.ietf-cbor-cddl-more-control], [STD94] and [STD90] apply. This collection of CDDL models is not thought to create new security considerations. Errors in the models could -- if we knew of them, we'd fix those errors instead of explaining their security consequences in this section.¶