--- 1/draft-ietf-ace-cbor-web-token-03.txt 2017-04-13 11:13:15.641183562 -0700 +++ 2/draft-ietf-ace-cbor-web-token-04.txt 2017-04-13 11:13:15.681184508 -0700 @@ -1,23 +1,23 @@ ACE Working Group M. Jones Internet-Draft Microsoft Intended status: Standards Track E. Wahlstroem -Expires: September 3, 2017 +Expires: October 15, 2017 S. Erdtman Spotify AB H. Tschofenig ARM Ltd. - March 2, 2017 + April 13, 2017 CBOR Web Token (CWT) - draft-ietf-ace-cbor-web-token-03 + draft-ietf-ace-cbor-web-token-04 Abstract CBOR Web Token (CWT) is a compact means of representing claims to be transferred between two parties. CWT is a profile of the JSON Web Token (JWT) that is optimized for constrained devices. The claims in a CWT are encoded in the Concise Binary Object Representation (CBOR) and CBOR Object Signing and Encryption (COSE) is used for added application layer security protection. A claim is a piece of information asserted about a subject and is represented as a name/ @@ -31,21 +31,21 @@ 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 http://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 September 3, 2017. + This Internet-Draft will expire on October 15, 2017. Copyright Notice Copyright (c) 2017 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 (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -55,73 +55,74 @@ the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Claims . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Claim Names . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. iss (Issuer) Claim . . . . . . . . . . . . . . . . . 4 - 3.1.2. sub (Subject) Claim . . . . . . . . . . . . . . . . . 4 + 3.1.2. sub (Subject) Claim . . . . . . . . . . . . . . . . . 5 3.1.3. aud (Audience) Claim . . . . . . . . . . . . . . . . 5 3.1.4. exp (Expiration Time) Claim . . . . . . . . . . . . . 5 3.1.5. nbf (Not Before) Claim . . . . . . . . . . . . . . . 5 3.1.6. iat (Issued At) Claim . . . . . . . . . . . . . . . . 5 3.1.7. cti (CWT ID) Claim . . . . . . . . . . . . . . . . . 5 4. Summary of the values, CBOR major types and encoded claim keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 5. CWT CBOR Tag . . . . . . . . . . . . . . . . . . . . . . . . 6 - 6. Creating and Validating CWTs . . . . . . . . . . . . . . . . 6 - 6.1. Creating a CWT . . . . . . . . . . . . . . . . . . . . . 6 - 6.2. Validating a CWT . . . . . . . . . . . . . . . . . . . . 7 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 - 8.1. CBOR Web Token (CWT) Claims Registry . . . . . . . . . . 9 - 8.1.1. Registration Template . . . . . . . . . . . . . . . . 9 - 8.1.2. Initial Registry Contents . . . . . . . . . . . . . . 10 - 8.2. Media Type Registration . . . . . . . . . . . . . . . . . 11 - 8.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 11 - 8.3. CoAP Content-Formats Registration . . . . . . . . . . . . 12 - 8.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 12 - 8.4. CBOR Tag registration . . . . . . . . . . . . . . . . . . 12 - 8.4.1. Registry Contents . . . . . . . . . . . . . . . . . . 12 - 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 9.1. Normative References . . . . . . . . . . . . . . . . . . 13 - 9.2. Informative References . . . . . . . . . . . . . . . . . 14 + 5. CBOR Tags and Claim Values . . . . . . . . . . . . . . . . . 6 + 6. CWT CBOR Tag . . . . . . . . . . . . . . . . . . . . . . . . 6 + 7. Creating and Validating CWTs . . . . . . . . . . . . . . . . 7 + 7.1. Creating a CWT . . . . . . . . . . . . . . . . . . . . . 7 + 7.2. Validating a CWT . . . . . . . . . . . . . . . . . . . . 8 + 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 + 9.1. CBOR Web Token (CWT) Claims Registry . . . . . . . . . . 9 + 9.1.1. Registration Template . . . . . . . . . . . . . . . . 10 + 9.1.2. Initial Registry Contents . . . . . . . . . . . . . . 10 + 9.2. Media Type Registration . . . . . . . . . . . . . . . . . 12 + 9.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 12 + 9.3. CoAP Content-Formats Registration . . . . . . . . . . . . 12 + 9.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 12 + 9.4. CBOR Tag registration . . . . . . . . . . . . . . . . . . 13 + 9.4.1. Registry Contents . . . . . . . . . . . . . . . . . . 13 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 13 + 10.2. Informative References . . . . . . . . . . . . . . . . . 14 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 14 A.1. Example CWT Claims Set . . . . . . . . . . . . . . . . . 14 A.2. Example keys . . . . . . . . . . . . . . . . . . . . . . 15 A.2.1. 128-bit Symmetric Key as Hex Encoded String . . . . . 15 A.2.2. 256-bit Symmetric Key as Hex Encoded String . . . . . 15 A.2.3. ECDSA P-256 256-bit COSE Key . . . . . . . . . . . . 15 A.3. Example Signed CWT . . . . . . . . . . . . . . . . . . . 16 A.4. Example MACed CWT . . . . . . . . . . . . . . . . . . . . 17 - A.5. Example Encrypted CWT . . . . . . . . . . . . . . . . . . 18 - A.6. Example Nested CWT . . . . . . . . . . . . . . . . . . . 19 - Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 20 - Appendix C. Document History . . . . . . . . . . . . . . . . . . 20 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 + A.5. Example Encrypted CWT . . . . . . . . . . . . . . . . . . 17 + A.6. Example Nested CWT . . . . . . . . . . . . . . . . . . . 18 + Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 19 + Appendix C. Document History . . . . . . . . . . . . . . . . . . 19 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 1. Introduction The JSON Web Token (JWT) [RFC7519] is a standardized security token format that has found use in OAuth 2.0 and OpenID Connect - deployments, among other applications. JWT uses JSON Web Signatures + deployments, among other applications. JWT uses JSON Web Signature (JWS) [RFC7515] and JSON Web Encryption (JWE) [RFC7516] to secure the - contents of the JWT, which is a set of claims represented in JSON - [RFC7519]. The use of JSON for encoding information is popular for - Web and native applications, but it is considered inefficient for - some Internet of Things (IoT) systems that use low power radio + contents of the JWT, which is a set of claims represented in JSON. + The use of JSON for encoding information is popular for Web and + native applications, but it is considered inefficient for some + Internet of Things (IoT) systems that use low power radio technologies. - In this document an alternative encoding of claims is defined. + An alternative encoding of claims is defined in this document. Instead of using JSON, as provided by JWTs, this specification uses CBOR [RFC7049] and calls this new structure "CBOR Web Token (CWT)", which is a compact means of representing secured claims to be transferred between two parties. CWT is closely related to JWT. It references the JWT claims and both its name and pronunciation are derived from JWT. To protect the claims contained in CWTs, the CBOR Object Signing and Encryption (COSE) [I-D.ietf-cose-msg] specification is used. The suggested pronunciation of CWT is the same as the English word @@ -130,31 +131,36 @@ 2. Terminology 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 "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119]. This document reuses terminology from JWT [RFC7519] and COSE [I-D.ietf-cose-msg]. - Type3StringOrURI: - The "Type3StringOrURI" term has the same meaning, syntax, and + StringOrURI: + The "StringOrURI" term has the same meaning, syntax, and processing rules as the "StringOrUri" term defined in Section 2 of - JWT [RFC7519], except that Type3StringOrURI uses CBOR major type 3 - instead of a JSON string value. + JWT [RFC7519], except that a CWT StringOrURI uses CBOR major type + 3 (text string) instead of a JSON string value. - Type6NumericDate: - The "Type6NumericDate" term has the same meaning, syntax, and + NumericDate: + The "NumericDate" term has the same meaning, syntax, and processing rules as the "NumericDate" term defined in Section 2 of - JWT [RFC7519], except that Type6NumericDate uses CBOR major type - 6, with tag value 1, instead of a numeric JSON value. + JWT [RFC7519], except that a CWT NumericDate uses one of the CBOR + numeric types (0, 1, or 7 with subtypes 25, 26, or 27), instead of + a numeric JSON value. The numeric date values that can used for a + CWT NumericDate are identical to the epoch-based date/time values + that are specified to follow the tag defined in Section 2.4.1 + (Date and Time) of [RFC7049], except that the tag itself need not + be present. CBOR encoded claim key: The key used to identify a claim value. CWT Claims Set A CBOR map that contains the claims conveyed by the CWT. 3. Claims The set of claims that a CWT must contain to be considered valid is @@ -173,111 +179,122 @@ None of the claims defined below are intended to be mandatory to use or implement. They rather provide a starting point for a set of useful, interoperable claims. Applications using CWTs should define which specific claims they use and when they are required or optional. 3.1.1. iss (Issuer) Claim The "iss" (issuer) claim has the same meaning, syntax, and processing rules as the "iss" claim defined in Section 4.1.1 of JWT [RFC7519], - except that the format MUST be a Type3StringOrURI. The CBOR encoded - claim key 1 MUST be used to identify this claim. + except that the format MUST be a StringOrURI. The CBOR encoded claim + key 1 MUST be used to identify this claim. 3.1.2. sub (Subject) Claim The "sub" (subject) claim has the same meaning, syntax, and processing rules as the "sub" claim defined in Section 4.1.2 of JWT - - [RFC7519], except that the format MUST be a Type3StringOrURI. The - CBOR encoded claim key 2 MUST be used to identify this claim. + [RFC7519], except that the format MUST be a StringOrURI. The CBOR + encoded claim key 2 MUST be used to identify this claim. 3.1.3. aud (Audience) Claim The "aud" (audience) claim has the same meaning, syntax, and processing rules as the "aud" claim defined in Section 4.1.3 of JWT - [RFC7519], except that the format MUST be a Type3StringOrURI. The - CBOR encoded claim key 3 MUST be used to identify this claim. + [RFC7519], except that the format MUST be a StringOrURI. The CBOR + encoded claim key 3 MUST be used to identify this claim. 3.1.4. exp (Expiration Time) Claim The "exp" (expiration time) claim has the same meaning, syntax, and processing rules as the "exp" claim defined in Section 4.1.4 of JWT - [RFC7519], except that the format MUST be a Type6NumericDate. The + [RFC7519], except that the format MUST be a CWT NumericDate. The CBOR encoded claim key 4 MUST be used to identify this claim. 3.1.5. nbf (Not Before) Claim The "nbf" (not before) claim has the same meaning, syntax, and processing rules as the "nbf" claim defined in Section 4.1.5 of JWT - [RFC7519], except that the format MUST be a Type6NumericDate. The + [RFC7519], except that the format MUST be a CWT NumericDate. The CBOR encoded claim key 5 MUST be used to identify this claim. 3.1.6. iat (Issued At) Claim The "iat" (issued at) claim has the same meaning, syntax, and processing rules as the "iat" claim defined in Section 4.1.6 of JWT - [RFC7519], except that the format MUST be a Type6NumericDate. The + [RFC7519], except that the format MUST be a CWT NumericDate. The CBOR encoded claim key 6 MUST be used to identify this claim. 3.1.7. cti (CWT ID) Claim The "cti" (CWT ID) claim has the same meaning, syntax, and processing rules as the "jti" claim defined in Section 4.1.7 of JWT [RFC7519], except that the format MUST be of major type 2, binary string. The CBOR encoded claim key 7 MUST be used to identify this claim. 4. Summary of the values, CBOR major types and encoded claim keys - /---------+------------------------+--------------------------\ + /---------+------------------------+-------------------------------\ | Claim | CBOR encoded claim key | CBOR major type of value | - |---------+------------------------+--------------------------| + |---------+------------------------+-------------------------------| | iss | 1 | 3 | | sub | 2 | 3 | | aud | 3 | 3 | - | exp | 4 | 6 tag value 1 | - | nbf | 5 | 6 tag value 1 | - | iat | 6 | 6 tag value 1 | + | exp | 4 | 0, 1, or 7 with float subtype | + | nbf | 5 | 0, 1, or 7 with float subtype | + | iat | 6 | 0, 1, or 7 with float subtype | | cti | 7 | 2 | - \---------+------------------------+--------------------------/ + \---------+------------------------+-------------------------------/ Figure 1: Summary of the values, CBOR major types and encoded claim keys. -5. CWT CBOR Tag +5. CBOR Tags and Claim Values + + The use of CBOR tags to prefix any of the claim values defined in + this specification is NOT RECOMMENDED. For instance, while CBOR tag + 6.1 (seconds-since-the-epoch) could logically be prefixed to values + of the "exp", "nbf", and "iat" claims, this is unnecessary, since the + representation of the claim values is already specified by the claim + definitions. Tagging claim values would only take up extra space, + without adding information. However, other claims defined by other + specifications can specify that a tag prefix the claim value, when + appropriate. + +6. CWT CBOR Tag How to determine that a CBOR data structure is a CWT is application- dependent. In some cases, this information is known from the application context, such as from the position of the CWT in a data structure at which the value must be a CWT. One method of indicating that a CBOR object is a CWT is the use of the "application/cwt" content type by a transport protocol. This section defines the CWT CBOR tag as another means for applications to declare that a CBOR data structure is a CWT. Its use is optional, and is intended for use in cases in which this information would not otherwise be known. - The CWT tag MUST prefix a tagged object using one of the COSE CBOR - tags. In this example, the COSE_Mac0 tag is used. The actual - COSE_Mac0 object has been excluded from this example. + If present, the CWT tag MUST prefix a tagged object using one of the + COSE CBOR tags. In this example, the COSE_Mac0 tag is used. The + actual COSE_Mac0 object has been excluded from this example. / CWT CBOR tag / 61( / COSE_Mac0 CBOR tag / 17( / COSE_Mac0 object / ) ) Figure 2: Example of a CWT tag usage -6. Creating and Validating CWTs +7. Creating and Validating CWTs -6.1. Creating a CWT +7.1. Creating a CWT To create a CWT, the following steps are performed. The order of the steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps. 1. Create a CWT Claims Set containing the desired claims. 2. Let the Message be the binary representation of the CWT Claims Set. @@ -303,36 +320,33 @@ plaintext for the COSE_Encrypt/COSE_Encrypt0 object; all steps specified in [I-D.ietf-cose-msg] for creating a COSE_Encrypt/ COSE_Encrypt0 object MUST be followed. 5. If a nested signing, MACing or encryption operation will be performed, let the Message be the COSE_Sign/COSE_Sign1, COSE_Mac/ COSE_Mac0 or COSE_Encrypt/COSE_Encrypt0, and return to Step 3, using a "content type" header value corresponding to the media type "application/cwt" in the new COSE Header created in that step. - Note: If integrity (signing/MACing) and confidentiality - (encryption) protection are needed, it is recommended to use an - authenticated encryption algorithm to save space and processing. 6. If needed by the application, add the appropriate COSE CBOR tag to the COSE object to indicate type of COSE object. If also needed by the application, add the CWT CBOR tag to indicate that the COSE object is a CWT. -6.2. Validating a CWT +7.2. Validating a CWT When validating a CWT, the following steps are performed. The order of the steps is not significant in cases where there are no dependencies between the inputs and outputs of the steps. If any of the listed steps fail, then the CWT MUST be rejected -- that is, - treated by the application as an invalid input. + treated by the application as invalid input. 1. Verify that the CWT is a valid CBOR object. 2. If the object begins with the CWT CBOR tag, remove it and verify that one of the COSE CBOR tags follows it. 3. If the object is tagged with one of the COSE CBOR tags, remove it and verify that it corresponds to the structure of the following COSE object. @@ -365,63 +379,63 @@ 7. If the COSE Header contains a "content type" header value corresponding to the media type "application/cwt", then the Message is a CWT that was the subject of nested signing or encryption operations. In this case, return to Step 1, using the Message as the CWT. 8. Verify that the Message is a valid CBOR object; let the CWT Claims Set be this CBOR object. -7. Security Considerations +8. Security Considerations The security of the CWT is dependent on the protections offered by COSE. Unless the claims in a CWT are protected, an adversary can modify, add, or remove claims. Since the claims conveyed in a CWT may be used to make authorization decisions, it is not only important to protect the CWT in transit but also to ensure that the recipient can authenticate the party that assembled the claims and created the CWT. Without trust of the recipient in the party that created the CWT, no sensible authorization decision can be made. Furthermore, the creator of the CWT needs to carefully evaluate each claim value prior to including it in the CWT so that the recipient can be assured of the validity of the information provided. -8. IANA Considerations +9. IANA Considerations -8.1. CBOR Web Token (CWT) Claims Registry +9.1. CBOR Web Token (CWT) Claims Registry This section establishes the IANA "CBOR Web Token (CWT) Claims" registry. Values are registered on a Specification Required [RFC5226] basis, on the advice of one or more Designated Experts. However, to allow for the allocation of values prior to publication, the Designated Experts may approve registration once they are satisfied that such a specification will be published. Criteria that should be applied by the Designated Experts includes determining whether the proposed registration duplicates existing functionality, whether it is likely to be of general applicability or whether it is useful only for a single application, and whether the registration description is clear. -8.1.1. Registration Template +9.1.1. Registration Template Claim Name: The human-readable name requested (e.g., "iss"). Claim Description: Brief description of the claim (e.g., "Issuer"). JWT Claim Name: - Claim Name of the equivalent JWT claim as registered in + Claim Name of the equivalent JWT claim, as registered in [IANA.JWT.Claims]. CWT claims should normally have a corresponding JWT claim. If a corresponding JWT claim would not make sense, the Designated Experts can choose to accept registrations for which the JWT Claim Name is listed as "N/A". CBOR Key Value: Key value for the claim. The key value MUST be an integer in the range of 1 to 65536. CBOR Major Type: @@ -431,21 +445,21 @@ For Standards Track RFCs, list the "IESG". For others, give the name of the responsible party. Other details (e.g., postal address, email address, home page URI) may also be included. Specification Document(s): Reference to the document or documents that specify the parameter, preferably including URIs that can be used to retrieve copies of the documents. An indication of the relevant sections may also be included but is not required. -8.1.2. Initial Registry Contents +9.1.2. Initial Registry Contents o Claim Name: "iss" o Claim Description: Issuer o JWT Claim Name: "iss" o CBOR Key Value: 1 o CBOR Major Type: 3 o Change Controller: IESG o Specification Document(s): Section 3.1.1 of [[ this specification ]] @@ -464,60 +478,59 @@ o CBOR Key Value: 3 o CBOR Major Type: 3 o Change Controller: IESG o Specification Document(s): Section 3.1.3 of [[ this specification ]] o Claim Name: "exp" o Claim Description: Expiration Time o JWT Claim Name: "exp" o CBOR Key Value: 4 - o CBOR Major Type: 6, tag value 1 + o CBOR Major Type: 0, 1, or 7 with subtypes 25, 26, or 27 o Change Controller: IESG o Specification Document(s): Section 3.1.4 of [[ this specification ]] o Claim Name: "nbf" o Claim Description: Not Before o JWT Claim Name: "nbf" o CBOR Key Value: 5 - o CBOR Major Type: 6, tag value 1 + o CBOR Major Type: 0, 1, or 7 with subtypes 25, 26, or 27 o Change Controller: IESG o Specification Document(s): Section 3.1.5 of [[ this specification ]] o Claim Name: "iat" o Claim Description: Issued At o JWT Claim Name: "iat" o CBOR Key Value: 6 - o CBOR Major Type: 6, tag value 1 + o CBOR Major Type: 0, 1, or 7 with subtypes 25, 26, or 27 o Change Controller: IESG o Specification Document(s): Section 3.1.6 of [[ this specification ]] o Claim Name: "cti" o Claim Description: CWT ID o JWT Claim Name: "jti" o CBOR Key Value: 7 o CBOR Major Type: 2 o Change Controller: IESG o Specification Document(s): Section 3.1.7 of [[ this specification ]] -8.2. Media Type Registration +9.2. Media Type Registration - This section registers the "application/cwt" media type [RFC2046] in - the "Media Types" registry [IANA.MediaTypes] in the manner described - in RFC 6838 [RFC6838], which can be used to indicate that the content - is a CWT. + This section registers the "application/cwt" media type in the "Media + Types" registry [IANA.MediaTypes] in the manner described in RFC 6838 + [RFC6838], which can be used to indicate that the content is a CWT. -8.2.1. Registry Contents +9.2.1. Registry Contents o Type name: application o Subtype name: cwt o Required parameters: N/A o Optional parameters: N/A o Encoding considerations: binary o Security considerations: See the Security Considerations section of [[ this specification ]] o Interoperability considerations: N/A o Published specification: [[ this specification ]] @@ -531,145 +544,125 @@ Macintosh file type code(s): N/A o Person & email address to contact for further information: IESG, iesg@ietf.org o Intended usage: COMMON o Restrictions on usage: none o Author: Michael B. Jones, mbj@microsoft.com o Change controller: IESG o Provisional registration? No -8.3. CoAP Content-Formats Registration +9.3. CoAP Content-Formats Registration This section registers the CoAP Content-Format ID for the "application/cwt" media type in the "CoAP Content-Formats" registry - [IANA.CoAP.Content-Formats] established by [RFC7252]. + [IANA.CoAP.Content-Formats]. -8.3.1. Registry Contents +9.3.1. Registry Contents o Media Type: application/cwt o Encoding: - o Id: TBD (maybe 61) o Reference: [[ this specification ]] -8.4. CBOR Tag registration +9.4. CBOR Tag registration This section registers the CWT CBOR tag in the "CBOR Tags" registry - [IANA.CBOR.Tags] established by [RFC7049]. + [IANA.CBOR.Tags]. -8.4.1. Registry Contents +9.4.1. Registry Contents o CBOR Tag: TBD (maybe 61 to use the same value as the Content- Format) o Data Item: CBOR Web Token (CWT) o Semantics: CBOR Web Token (CWT), as defined in [[ this specification ]] o Reference: [[ this specification ]] o Point of Contact: Michael B. Jones, mbj@microsoft.com -9. References +10. References -9.1. Normative References +10.1. Normative References [I-D.ietf-cose-msg] Schaad, J., "CBOR Object Signing and Encryption (COSE)", draft-ietf-cose-msg-24 (work in progress), November 2016. [IANA.CBOR.Tags] IANA, "Concise Binary Object Representation (CBOR) Tags", . [IANA.CoAP.Content-Formats] IANA, "CoAP Content-Formats", . - [IANA.JWT.Claims] - IANA, "JSON Web Token Claims", - . - [IANA.MediaTypes] IANA, "Media Types", . - [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail - Extensions (MIME) Part Two: Media Types", RFC 2046, - DOI 10.17487/RFC2046, November 1996, - . - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . + [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object + Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, + October 2013, . + + [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token + (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, + . + +10.2. Informative References + + [IANA.JWT.Claims] + IANA, "JSON Web Token Claims", + . + [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, . [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, . - [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object - Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, - October 2013, . - - [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data - Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March - 2014, . - - [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained - Application Protocol (CoAP)", RFC 7252, - DOI 10.17487/RFC7252, June 2014, - . - [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, . [RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)", RFC 7516, DOI 10.17487/RFC7516, May 2015, . - [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token - (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, - . - -9.2. Informative References - - [I-D.greevenbosch-appsawg-cbor-cddl] - Vigano, C. and H. Birkholz, "CBOR data definition language - (CDDL): a notational convention to express CBOR data - structures", draft-greevenbosch-appsawg-cbor-cddl-09 (work - in progress), September 2016. - Appendix A. Examples This appendix includes a set of CWT examples that show how the CWT Claims Set can be protected. There are examples that are signed, MACed, encrypted, and that use nested signing and encryption. To make the examples easier to read, they are presented both as hex - strings and in the extended CBOR diagnostic notation - [I-D.greevenbosch-appsawg-cbor-cddl]. + strings and in the extended CBOR diagnostic notation described in + Section 6 of [RFC7049]. A.1. Example CWT Claims Set The CWT Claims Set used for the different examples displays usage of all the defined claims. For signed and MACed examples, the CWT Claims Set is the CBOR encoding as a binary string. - a702656572696b77037818636f61703a2f2f6c696768742e6578616d706c652e - 636f6d041a5612aeb0051a5610d9f0061a5610d9f00175636f61703a2f2f6173 - 2e6578616d706c652e636f6d07420b71 + a70175636f61703a2f2f61732e6578616d706c652e636f6d02656572696b7703 + 7818636f61703a2f2f6c696768742e6578616d706c652e636f6d041a5612aeb0 + 051a5610d9f0061a5610d9f007420b71 Figure 3: Example CWT Claims Set as hex string { / iss / 1: "coap://as.example.com", / sub / 2: "erikw", / aud / 3: "coap://light.example.com", / exp / 4: 1444064944, / nbf / 5: 1443944944, / iat / 6: 1443944944, @@ -679,165 +672,164 @@ Figure 4: Example CWT Claims Set in CBOR diagnostic notation A.2. Example keys This section contains the keys used to sign, MAC, and encrypt the messages in this appendix. Line breaks are for display purposes only. A.2.1. 128-bit Symmetric Key as Hex Encoded String - 9e4f3e65cc1a558b39ce97b3db469b04 + 8e82e68e61654ecb5a369fe8be7572dd A.2.2. 256-bit Symmetric Key as Hex Encoded String - e60198ac1650ec9210d7f4f5b27aeae2ada8f4adada555909edca75ce2ae506e + 403697de87af64611c1d32a05dab0fe1fcb715a86ab435f1ec99192d79569388 A.2.3. ECDSA P-256 256-bit COSE Key - a6225820feb11ca73b028a10cf77d58a2dfdf2a11eab8ffeeeaaeeb03097ffee - 9f3ef2fc2358200657fada2568959c49a404583fe237290ebeb1956f3ad3d966 - ea09e33369d7b103260102215820c4f9160fc22682991c59c4d96e8accc2da3c - c7b7a9bc197c7c1e1bc6d0c1dc612001 + a622582060f7f1a780d8a783bfb7a2dd6b2796e8128dbbcef9d3d168db952997 + 1a36e7b92358206c1382765aec5358f117733d281c1c7bdc39884d04a45a1e6c + 67c858bc206c1903260102215820143329cce7868e416927599cf65a34f3ce2f + fda55a7eca69ed8919a394d42f0f2001 Figure 5: ECDSA 256-bit COSE Key as hex string { - / d / -4: h'0657fada2568959c49a404583fe237290ebeb1956f3ad3d966 - ea09e33369d7b1', - / y / -3: h'feb11ca73b028a10cf77d58a2dfdf2a11eab8ffeeeaaeeb030 - 97ffee9f3ef2fc', - / x / -2: h'c4f9160fc22682991c59c4d96e8accc2da3cc7b7a9bc197c7c - 1e1bc6d0c1dc61', - / crv / -1: 1 / P-256 / + / d / -4: h'6c1382765aec5358f117733d281c1c7bdc39884d04a45a1e + 6c67c858bc206c19', + / y / -3: h'60f7f1a780d8a783bfb7a2dd6b2796e8128dbbcef9d3d168 + db9529971a36e7b9', + / x / -2: h'143329cce7868e416927599cf65a34f3ce2ffda55a7eca69 + ed8919a394d42f0f', + / crv / -1: 1 / P-256 / , / kty / 1: 2 / EC2 /, - / alg / 3: -7, \ ECDSA 256 \ + / alg / 3: -7 / ECDSA 256 / } Figure 6: ECDSA 256-bit COSE Key in CBOR diagnostic notation A.3. Example Signed CWT This section shows a signed CWT with a single recipient and a full CWT Claims Set. - The signature is generated using the private ECDSA key from - Appendix A.2.3 and it can be validated using the public part of the - ECDSA key from Appendix A.2.3. Line breaks are for display purposes - only. + The signature is generated using the private key listed in + Appendix A.2.3 and it can be validated using the public key from + Appendix A.2.3. Line breaks are for display purposes only. - d28446a203183d0126a05850a702656572696b77037818636f61703a2f2f6c69 - 6768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9 - f00175636f61703a2f2f61732e6578616d706c652e636f6d07420b7158407eef - 29abe962ac185e5a372d95d69ce1b5683c5c25efb69a81710dc5173254f5179a - 639827694c22828819704eb026676ca78aaf8da76672a6b5537fb90e710d + d28443a10126a05850a70175636f61703a2f2f61732e6578616d706c652e636f6 + d02656572696b77037818636f61703a2f2f6c696768742e6578616d706c652e63 + 6f6d041a5612aeb0051a5610d9f0061a5610d9f007420b7158401fe410abce650 + effed497f05d7f9462de67d571384097de0d96f1e2514d284cdd85634f269af6c + 36c64f22e7691abb464bed2ff23176cdba9fd9e213f637d082 Figure 7: Signed CWT as hex string 18( [ - / protected / h'a203183d0126' / { - / content type / 3: 61, / CWT / + / protected / h'a10126' / { / alg / 1: -7 / ECDSA 256 / } / , / unprotected / {}, - / payload / h'a702656572696b77037818636f61703a2f2f6c69676874 - 2e6578616d706c652e636f6d041a5612aeb0051a5610d9 - f0061a5610d9f00175636f61703a2f2f61732e6578616d - 706c652e636f6d07420b71' / { + / payload / h'a70175636f61703a2f2f61732e6578616d706c652e63 + 6f6d02656572696b77037818636f61703a2f2f6c6967 + 68742e6578616d706c652e636f6d041a5612aeb0051a + 5610d9f0061a5610d9f007420b71' / { / iss / 1: "coap://as.example.com", / sub / 2: "erikw", / aud / 3: "coap://light.example.com", / exp / 4: 1444064944, / nbf / 5: 1443944944, / iat / 6: 1443944944, / cti / 7: h'0b71' } / , - / signature / h'7eef29abe962ac185e5a372d95d69ce1b5683c5c25ef - b69a81710dc5173254f5179a639827694c2282881970 - 4eb026676ca78aaf8da76672a6b5537fb90e710d' + / signature / h'1fe410abce650effed497f05d7f9462de67d571384 + 097de0d96f1e2514d284cdd85634f269af6c36c64f + 22e7691abb464bed2ff23176cdba9fd9e213f637d0 + 82' ] ) Figure 8: Signed CWT in CBOR diagnostic notation A.4. Example MACed CWT This section shows a MACed CWT with a single recipient and a full CWT Claims Set. The MAC is generated using the 256-bit symmetric key from Appendix A.2.2 with a 64-bit truncation. Line breaks are for display purposes only. - d18446a203183d0104a05850a702656572696b77037818636f61703a2f2f6c69 - 6768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9 - f00175636f61703a2f2f61732e6578616d706c652e636f6d07420b7148b59884 - 6f1ce93f9d + d83dd18443a10104a05850a70175636f61703a2f2f61732e6578616d706c652e + 636f6d02656572696b77037818636f61703a2f2f6c696768742e6578616d706c + 652e636f6d041a5612aeb0051a5610d9f0061a5610d9f007420b7148093101ef + 6d789200 - Figure 9: MACed CWT as hex string + Figure 9: MACed CWT with CWT tag as hex string + 61( 17( [ - / protected / h'a203183d0104' / { - / content type / 3: 61, / CWT / + / protected / h'a10104' / { / alg / 1: 4 / HMAC 256/64 / } / , / unprotected / {}, - / payload / h'a702656572696b77037818636f61703a2f2f6c69676874 + / payload / h'a70175636f61703a2f2f61732e6578616d706c652e636f + 6d02656572696b77037818636f61703a2f2f6c69676874 2e6578616d706c652e636f6d041a5612aeb0051a5610d9 - f0061a5610d9f00175636f61703a2f2f61732e6578616d - 706c652e636f6d07420b71' / { + f0061a5610d9f007420b71' / { / iss / 1: "coap://as.example.com", / sub / 2: "erikw", / aud / 3: "coap://light.example.com", / exp / 4: 1444064944, / nbf / 5: 1443944944, / iat / 6: 1443944944, / cti / 7: h'0b71' } / , - / tag / h'b598846f1ce93f9d' + / tag / h'093101ef6d789200' ] ) + ) - Figure 10: MACed CWT in CBOR diagnostic notation + Figure 10: MACed CWT with CWT tag in CBOR diagnostic notation A.5. Example Encrypted CWT This section shows an encrypted CWT with a single recipient and a full CWT Claims Set. The encryption is done with AES-CCM mode using the 128-bit symmetric key from Appendix A.2.1 with a 64-bit tag and 13-byte nonce, i.e., COSE AES-CCM-16-64-128. Line breaks are for display purposes only. - d08346a203183d010aa1054dadbe290e8c9c23067a558b15795858f7a8ec3e32 - 3bb6e006e8aec087666f6fc0d65d7aa272f5f1dde1dfb52fd3a5e1ace97e5bfc - 8f05a146fd8a9feab7bb9e722254e2660612f956041264c06ea3b95afb0d8ce3 - 138bc80baf2511565d3dad63ea7534699fa449 + d08343a1010aa1054d3a869e378e72b77d077c29be025858d275ad9cd7df1b10 + ba8cde785c74b1e1e6ada287e2baf1451b06862529b784d230b0111773b6c369 + 1319aec4dcc379fe47115a5d62632727c05f4567fc84dd79554db86676a14978 + 42de805d8be93180af4d6ff3043886a0 Figure 11: Encrypted CWT as hex string 16( [ - / protected / h'a203183d010a' / { - / content type / 3: 61, / CWT / + / protected / h'a1010a' / { / alg / 1: 10 / AES-CCM-16-64-128 / } /, / unprotected / { - / iv / 5: h'adbe290e8c9c23067a558b1579' + / iv / 5: h'3a869e378e72b77d077c29be02' }, - / ciphertext / h'f7a8ec3e323bb6e006e8aec087666f6fc0d65d7aa27 - 2f5f1dde1dfb52fd3a5e1ace97e5bfc8f05a146fd8a - 9feab7bb9e722254e2660612f956041264c06ea3b95 - afb0d8ce3138bc80baf2511565d3dad63ea7534699f - a449' + / ciphertext / h'd275ad9cd7df1b10ba8cde785c74b1e1e6ada287e2b + af1451b06862529b784d230b0111773b6c3691319ae + c4dcc379fe47115a5d62632727c05f4567fc84dd795 + 54db86676a1497842de805d8be93180af4d6ff30438 + 86a0' ] ) Figure 12: Encrypted CWT in CBOR diagnostic notation A.6. Example Nested CWT This section shows a Nested CWT, signed and then encrypted, with a single recipient and a full CWT Claims Set. @@ -846,63 +838,67 @@ from Appendix A.2.3. The encryption is done with AES-CCM mode using the 128-bit symmetric key from Appendix A.2.1 with a 64-bit tag and 13-byte nonce, i.e., COSE AES-CCM-16-64-128. The content type is set to CWT to indicate that there are multiple layers of COSE protection before finding the CWT Claims Set. The decrypted ciphertext will be a COSE_sign1 structure. In this example, it is the same one as in Appendix A.3, i.e., a Signed CWT Claims Set. Note that there is no limitation to the number of layers; this is an example with two layers. Line breaks are for display purposes only. - d08346a203183d010aa1054d2653469d58937647a6a1bb023458a65da538206c33 - cf941df7ea933ba7b93c60322017f9db9c904608fce2688b51028b5b912f9010 - ae72802bf65778593c7270b20683b1587824eb4074e03323ccf0541b495a3757 - f353a8424b6ceeaaec1898964d8a03e04e514a5b0ca143b57689a2a9f1c6c84d - 535d1966adf900dfaf0dd045d2325c40150a07d602b65c60e62894c870ad5fc2 - cb709e4d17d381806797b6cf118608e18c3facd0a0ac09d88ea73d4ed7e3b57c + d08346a203183d010aa1054d9120e5dc42c9f9aec05ebe8a4858a538be026c02 + 4a40b19d6dbea3ddb18b31021f874a097a05ff3cdaa4665bafc8e46a3d7f37ad + f002fe57eee267f8f62a9c1621af75e1ecd742a3d801c2cc82358cf104a8d902 + 4d38a599ea6027d482dc2948a88fe83f9734804299c832401029e2d32a984789 + c8e9563e8d2a751323bb7e4462b549e0fa89ef93f78bf6425635fba76b4aa804 + 7908e89b3b7c3d59d8a80e22f70a1b6ee8c162c564341c2f15cec252d3da038c Figure 13: Signed and Encrypted CWT as hex string 16( [ / protected / h'a203183d010a' / { / content type / 3: 61, / CWT / / alg / 1: 10 / AES-CCM-16-64-128 / } / , / unprotected / { - / iv / 5: h'2653469d58937647a6a1bb0234' + / iv / 5: h'9120e5dc42c9f9aec05ebe8a48' }, - / ciphertext / h'5da538206c33cf941df7ea933ba7b93c60322017f9d - b9c904608fce2688b51028b5b912f9010ae72802bf6 - 5778593c7270b20683b1587824eb4074e03323ccf05 - 41b495a3757f353a8424b6ceeaaec1898964d8a03e0 - 4e514a5b0ca143b57689a2a9f1c6c84d535d1966adf - 900dfaf0dd045d2325c40150a07d602b65c60e62894 - c870ad5fc2cb709e4d17d381806797b6cf118608e18 - c3facd0a0ac09d88ea73d4ed7e3b57c' + / ciphertext / h'38be026c024a40b19d6dbea3ddb18b31021f874a097 + a05ff3cdaa4665bafc8e46a3d7f37adf002fe57eee2 + 67f8f62a9c1621af75e1ecd742a3d801c2cc82358cf + 104a8d9024d38a599ea6027d482dc2948a88fe83f97 + 34804299c832401029e2d32a984789c8e9563e8d2a7 + 51323bb7e4462b549e0fa89ef93f78bf6425635fba7 + 6b4aa8047908e89b3b7c3d59d8a80e22f70a1b6ee8c + 162c564341c2f15cec252d3da038c' ] ) Figure 14: Signed and Encrypted CWT in CBOR diagnostic notation Appendix B. Acknowledgements This specification is based on JSON Web Token (JWT) [RFC7519], the authors of which also include Nat Sakimura and John Bradley. Ludwig Seitz and Goeran Selander have made contributions the specification. Appendix C. Document History [[ to be removed by the RFC Editor before publication as an RFC ]] - -03 + -04 + o Specified that the use of CBOR tags to prefix any of the claim + values defined in this specification is NOT RECOMMENDED. + + -03 o Reworked the examples to include signed, MACed, encrypted, and nested CWTs. o Defined the CWT CBOR tag and explained its usage. -02 o Added IANA registration for the application/cwt media type. o Clarified the nested CWT language. o Corrected nits identified by Ludwig Seitz.