rfc9596.original   rfc9596.txt 
COSE Working Group M.B. Jones Internet Engineering Task Force (IETF) M.B. Jones
Internet-Draft Self-Issued Consulting Request for Comments: 9596 Self-Issued Consulting
Intended status: Standards Track O. Steele Category: Standards Track O. Steele
Expires: 5 October 2024 Transmute ISSN: 2070-1721 Transmute
3 April 2024 June 2024
COSE "typ" (type) Header Parameter CBOR Object Signing and Encryption (COSE) "typ" (type) Header Parameter
draft-ietf-cose-typ-header-parameter-05
Abstract Abstract
This specification adds the equivalent of the JSON Object Signing and This specification adds the equivalent of the JSON Object Signing and
Encryption (JOSE) typ (type) header parameter to CBOR Object Signing Encryption (JOSE) "typ" (type) header parameter to CBOR Object
and Encryption (COSE). This enables the benefits of explicit typing, Signing and Encryption (COSE). This enables the benefits of explicit
as defined in the JSON Web Token Best Current Practices BCP, to be typing (as defined in RFC 8725, "JSON Web Token Best Current
brought to COSE objects. The syntax of the COSE type header Practices") to be brought to COSE objects. The syntax of the COSE
parameter value is the same as the existing COSE content type header type header parameter value is the same as the existing COSE content
parameter. type header parameter.
Status of This Memo Status of This Memo
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https://www.rfc-editor.org/info/rfc9596.
Copyright Notice Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction
1.1. Requirements Notation and Conventions . . . . . . . . . . 3 1.1. Requirements Notation and Conventions
2. COSE "typ" (type) header parameter . . . . . . . . . . . . . 3 2. COSE "typ" (type) Header Parameter
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 3. Security Considerations
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations
4.1. COSE Header Parameter Registrations . . . . . . . . . . . 4 4.1. COSE Header Parameter Registrations
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. References
5.1. Normative References . . . . . . . . . . . . . . . . . . 4 5.1. Normative References
5.2. Informative References . . . . . . . . . . . . . . . . . 5 5.2. Informative References
Appendix A. Document History . . . . . . . . . . . . . . . . . . 5 Acknowledgements
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
CBOR Object Signing and Encryption (COSE) [RFC9052] defines header CBOR Object Signing and Encryption (COSE) [RFC9052] defines header
parameters that parallel many of those defined by the JSON Object parameters that parallel many of those defined by the JSON Object
Signing and Encryption (JOSE) [RFC7515] [RFC7516] specifications. Signing and Encryption (JOSE) specifications [RFC7515] [RFC7516].
However, one way in which COSE does not provide equivalent However, one way in which COSE does not provide equivalent
functionality to JOSE is that it does not define an equivalent of the functionality to JOSE is that it does not define an equivalent of the
typ (type) header parameter, which is used for declaring the type of "typ" (type) header parameter, which is used for declaring the type
the entire JOSE data structure. The security benefits of having typ of the entire JOSE data structure. The security benefits of having
(type) are described in Section 3.11 of the JSON Web Token Best "typ" (type) are described in Section 3.11 of [RFC8725], which
Current Practices [RFC8725], which recommends its use for "explicit recommends its use for "explicit typing" -- using "typ" values to
typing" -- using typ values to distinguish between different kinds of distinguish between different kinds of JSON Web Tokens (JWTs)
JSON Web Tokens (JWTs) [RFC7519]. [RFC7519].
This specification adds the equivalent of the JOSE typ (type) header This specification adds the equivalent of the JOSE "typ" (type)
parameter to COSE so that the benefits of explicit typing can be header parameter to COSE so that the benefits of explicit typing can
brought to COSE objects. The syntax of the COSE type header be brought to COSE objects. The syntax of the COSE type header
parameter value is the same as the existing COSE content type header parameter value is the same as the existing COSE content type header
parameter, allowing both unsigned integer CoAP Content-Formats parameter, allowing both unsigned integers as registered in the "CoAP
[IANA.CoAP.ContentFormats] values and string Media Type Content-Formats" registry [CoAP.ContentFormats] and string media type
[IANA.MediaTypes] values to be used. values [MediaTypes] to be used.
The term "COSE object" is used as defined in [RFC9052]. An example The term "COSE object" is used as defined in [RFC9052]. An example
of a COSE object is a COSE_Sign1 structure, as described in of a COSE object is a COSE_Sign1 structure, as described in
Section 4.2 of [RFC9052]. Section 4.2 of [RFC9052].
1.1. Requirements Notation and Conventions 1.1. Requirements Notation and Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. COSE "typ" (type) header parameter 2. COSE "typ" (type) Header Parameter
The typ (type) header parameter is used by COSE applications to The "typ" (type) header parameter is used by COSE applications to
declare the type of this complete COSE object, as compared to the declare the type of this complete COSE object, as compared to the
content type header parameter, which declares the type of the COSE content type header parameter, which declares the type of the COSE
object payload. This is intended for use by the application when object payload. This is intended for use by the application when
more than one kind of COSE object could be present in an application more than one kind of COSE object could be present in an application
data structure that can contain a COSE object; the application can data structure that can contain a COSE object; the application can
use this value to disambiguate among the different kinds of COSE use this value to disambiguate among the different kinds of COSE
objects that might be present. It will typically not be used by objects that might be present. It will typically not be used by
applications when the kind of COSE object is already known. Use of applications when the kind of COSE object is already known. Use of
this header parameter is OPTIONAL. this header parameter is OPTIONAL.
The syntax of this header parameter value is the same as the content The syntax of this header parameter value is the same as the content
type header parameter defined in Section 3.1 of [RFC9052]; it is type header parameter defined in Section 3.1 of [RFC9052]; it is
either an unsigned integer CoAP Content-Formats either an unsigned integer as registered in the "CoAP Content-
[IANA.CoAP.ContentFormats] value or a string Content Type value. Formats" registry [CoAP.ContentFormats] or a string content type
Content Type values have a Media Type name [IANA.MediaTypes] and MAY value. Content type values have a media type name [MediaTypes] and
include Media Type parameters. MAY include media type parameters.
This parameter is ignored by COSE implementations (libraries The "typ" (type) header parameter is ignored by COSE implementations
implementing [RFC9052] and this specification), other than being (libraries implementing [RFC9052] and this specification), other than
passed through to applications using those implementations. Any being passed through to applications using those implementations.
processing of this parameter is performed by the COSE application Any processing of this parameter is performed by the COSE application
using application-specific processing rules. For instance, an using application-specific processing rules. For instance, an
application might verify that the typ value is a particular application might verify that the "typ" value is a particular
application-chosen media type and reject the data structure if it is application-chosen media type and reject the data structure if it is
not. not.
The typ parameter MUST NOT be present in unprotected headers. The "typ" parameter MUST NOT be present in unprotected headers.
The typ parameter does not describe the content of unprotected The "typ" parameter does not describe the content of unprotected
headers. Changes to unprotected headers do not change the type of headers. Changes to unprotected headers do not change the type of
the COSE object. the COSE object.
3. Security Considerations 3. Security Considerations
The case for explicit typing of COSE objects is equivalent to the The case for explicit typing of COSE objects is equivalent to the
case made for explicit typing in Section 3.11 of JSON Web Token Best case made for explicit typing in Section 3.11 of [RFC8725]: Explicit
Current Practices [RFC8725]: Explicit typing can prevent confusion typing can prevent confusion between different kinds of COSE objects.
between different kinds of COSE objects.
COSE applications employing explicit typing should reject COSE COSE applications employing explicit typing should reject COSE
objects with a type header parameter value different than values that objects with a type header parameter value different than values that
they expect in that application context. They should also reject they expect in that application context. They should also reject
COSE objects without a type header parameter when one is expected. COSE objects without a type header parameter when one is expected.
4. IANA Considerations 4. IANA Considerations
4.1. COSE Header Parameter Registrations 4.1. COSE Header Parameter Registrations
This section registers the following value in the IANA "COSE Header IANA has registered the following value in the IANA "COSE Header
Parameters" registry [IANA.COSE.HeaderParameters]. Parameters" registry [COSE.HeaderParameters].
* Name: typ (type) +======+=====+======+=======================+===========+=========+
* Label: TBD (requested assignment 16) |Name |Label|Value | Value Registry |Description|Reference|
* Value Type: uint / tstr | | |Type | | | |
* Value Registry: [IANA.CoAP.ContentFormats] or [IANA.MediaTypes] +======+=====+======+=======================+===========+=========+
* Description: Type of the complete COSE object |typ |16 |uint /| [CoAP.ContentFormats] |Content |Section 2|
* Reference: Section 2 of this specification |(type)| |tstr | or [MediaTypes] |type of the|of RFC |
| | | | registry |complete |9596 |
| | | | |COSE object| |
+------+-----+------+-----------------------+-----------+---------+
Table 1
5. References 5. References
5.1. Normative References 5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 5, line 7 skipping to change at line 187
DOI 10.17487/RFC8725, February 2020, DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/info/rfc8725>. <https://www.rfc-editor.org/info/rfc8725>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE): [RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052, Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022, DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/info/rfc9052>. <https://www.rfc-editor.org/info/rfc9052>.
5.2. Informative References 5.2. Informative References
[IANA.CoAP.ContentFormats] [CoAP.ContentFormats]
IANA, "CoAP Content-Formats", IANA, "CoAP Content-Formats",
<https://www.iana.org/assignments/core-parameters/core- <https://www.iana.org/assignments/core-parameters>.
parameters.xhtml#content-formats>.
[IANA.COSE.HeaderParameters] [COSE.HeaderParameters]
IANA, "COSE Header Parameters", IANA, "COSE Header Parameters",
<https://www.iana.org/assignments/cose/cose.xhtml#header- <https://www.iana.org/assignments/cose>.
parameters>.
[IANA.MediaTypes] [MediaTypes]
IANA, "Media Types", IANA, "Media Types",
<https://www.iana.org/assignments/media-types>. <https://www.iana.org/assignments/media-types>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>. 2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015, RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>. <https://www.rfc-editor.org/info/rfc7516>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>. <https://www.rfc-editor.org/info/rfc7519>.
Appendix A. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-05
* Addressed Area Director review comments.
-04
* Addressed SECDIR review comments.
-03
* Addressed GENART and OPSDIR review comments.
-02
* Addressed working group last call comments.
* Changed requested assignment from 14 to 16 due to conflict a with
new assignment.
-01
* Added language about media type parameters.
-00
* Initial working group version based on draft-jones-cose-typ-
header-parameter-01.
Acknowledgements Acknowledgements
We would like to thank Henk Birkholz, Carsten Bormann, Susan Hares, We would like to thank Henk Birkholz, Carsten Bormann, Susan Hares,
Dan Harkins, Murray Kucherawy, Marco Tiloca, Gunter Van de Velde, Dan Harkins, Murray Kucherawy, Marco Tiloca, Gunter Van de Velde,
Éric Vyncke, and Dale Worley for their valuable contributions to this Éric Vyncke, and Dale Worley for their valuable contributions to this
specification. specification.
Authors' Addresses Authors' Addresses
Michael B. Jones Michael B. Jones
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