--- 1/draft-ietf-ace-cbor-web-token-02.txt 2017-03-02 18:13:44.350169299 -0800 +++ 2/draft-ietf-ace-cbor-web-token-03.txt 2017-03-02 18:13:44.390170207 -0800 @@ -1,23 +1,23 @@ ACE Working Group M. Jones Internet-Draft Microsoft -Intended status: Informational E. Wahlstroem -Expires: July 17, 2017 +Intended status: Standards Track E. Wahlstroem +Expires: September 3, 2017 S. Erdtman Spotify AB H. Tschofenig ARM Ltd. - January 13, 2017 + March 2, 2017 CBOR Web Token (CWT) - draft-ietf-ace-cbor-web-token-02 + draft-ietf-ace-cbor-web-token-03 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 July 17, 2017. + This Internet-Draft will expire on September 3, 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 @@ -56,49 +56,58 @@ 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 - 3.1.3. aud (Audience) Claim . . . . . . . . . . . . . . . . 4 + 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. Creating and Validating CWTs . . . . . . . . . . . . . . . . 6 - 5.1. Creating a CWT . . . . . . . . . . . . . . . . . . . . . 6 - 5.2. Validating a CWT . . . . . . . . . . . . . . . . . . . . 7 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 - 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 - 7.1. CBOR Web Token (CWT) Claims Registry . . . . . . . . . . 8 - 7.1.1. Registration Template . . . . . . . . . . . . . . . . 8 - 7.1.2. Initial Registry Contents . . . . . . . . . . . . . . 9 - 7.2. Media Type Registration . . . . . . . . . . . . . . . . . 10 - 7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 10 - 7.3. CoAP Content-Formats Registration . . . . . . . . . . . . 11 - 7.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 11 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 - 8.2. Informative References . . . . . . . . . . . . . . . . . 13 - Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 13 - A.1. CWT with "aud" and symmetric key . . . . . . . . . . . . 13 - A.2. CWT with "aud" and EC key . . . . . . . . . . . . . . . . 14 - A.3. Full CWT . . . . . . . . . . . . . . . . . . . . . . . . 16 - Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 19 + 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 + 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 . . . . . . . . . . . . . . . . . . . . . . . 20 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 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 (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 @@ -227,38 +235,64 @@ | aud | 3 | 3 | | exp | 4 | 6 tag value 1 | | nbf | 5 | 6 tag value 1 | | iat | 6 | 6 tag value 1 | | cti | 7 | 2 | \---------+------------------------+--------------------------/ Figure 1: Summary of the values, CBOR major types and encoded claim keys. -5. Creating and Validating CWTs +5. CWT CBOR Tag -5.1. Creating a CWT + 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. + + / 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 + +6.1. 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. 3. Create a COSE Header containing the desired set of Header - Parameters. The COSE Header MUST be valid according to the + Parameters. The COSE Header MUST be valid per the [I-D.ietf-cose-msg] specification. - 4. Depending upon whether the CWT is signed, MACed or encrypted, + 4. Depending upon whether the CWT is signed, MACed, or encrypted, there are three cases: * If the CWT is signed, create a COSE_Sign/COSE_Sign1 object using the Message as the COSE_Sign/COSE_Sign1 Payload; all steps specified in [I-D.ietf-cose-msg] for creating a COSE_Sign/COSE_Sign1 object MUST be followed. * Else, if the CWT is MACed, create a COSE_Mac/COSE_Mac0 object using the Message as the COSE_Mac/COSE_Mac0 Payload; all steps specified in [I-D.ietf-cose-msg] for creating a COSE_Mac/ @@ -273,101 +307,112 @@ 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. -5.2. Validating a CWT + 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 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. 1. Verify that the CWT is a valid CBOR object. - 2. Verify that the resulting COSE Header includes only parameters + 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. + + 4. Verify that the resulting COSE Header includes only parameters and values whose syntax and semantics are both understood and supported or that are specified as being ignored when not understood. - 3. Use the CBOR tag to determine the type of the CWT, COSE_Sign/ + 5. Use the CBOR tag to determine the type of the CWT, COSE_Sign/ COSE_Sign1, COSE_Mac/COSE_Mac0, or COSE_Encrypt/COSE_Encrypt0. - 4. Depending upon whether the CWT is a COSE_Sign/COSE_Sign1, - COSE_Mac/COSE_Mac0 or COSE_Encrypt/COSE_Encrypt0, there are three - cases: + 6. Depending upon whether the CWT is a signed, MACed, or encrypted, + there are three cases: * If the CWT is a COSE_Sign/COSE_Sign1, follow the steps specified in [I-D.ietf-cose-msg] Section 4 (Signing Objects) for validating a COSE_Sign/COSE_Sign1 object. Let the Message be the COSE_Sign/COSE_Sign1 payload. * Else, if the CWT is a COSE_Mac/COSE_Mac0, follow the steps specified in [I-D.ietf-cose-msg] Section 6 (MAC Objects) for validating a COSE_Mac/COSE_Mac0 object. Let the Message be the COSE_Mac/COSE_Mac0 payload. * Else, if the CWT is a COSE_Encrypt/COSE_Encrypt0 object, follow the steps specified in [I-D.ietf-cose-msg] Section 5 (Encryption Objects) for validating a COSE_Encrypt/ COSE_Encrypt0 object. Let the Message be the resulting plaintext. - 5. If the COSE Header contains a "content type" header value + 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. - 6. Verify that the Message is a valid CBOR object; let the CWT + 8. Verify that the Message is a valid CBOR object; let the CWT Claims Set be this CBOR object. -6. Security Considerations +7. Security Considerations - The security of the CWT is dependent on the protection offered by - COSE. Without protecting the claims contained in a CWT an adversary - is able to modify, add or remove claims. Since the claims conveyed - in a CWT are used to make authorization decisions it is not only - important to protect the CWT in transit but also to ensure that the - recipient is able to authenticate the party that collected 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 about the correctness of the provided information. + 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. -7. IANA Considerations +8. IANA Considerations -7.1. CBOR Web Token (CWT) Claims Registry +8.1. 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. -7.1.1. Registration Template +8.1.1. 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 [IANA.JWT.Claims]. CWT claims should normally have a @@ -386,21 +431,21 @@ 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. -7.1.2. Initial Registry Contents +8.1.2. 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 ]] @@ -451,28 +496,28 @@ 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 ]] -7.2. Media Type Registration +8.2. 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. -7.2.1. Registry Contents +8.2.1. 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 ]] @@ -486,41 +531,61 @@ 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 -7.3. CoAP Content-Formats Registration +8.3. 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]. -7.3.1. Registry Contents +8.3.1. Registry Contents o Media Type: application/cwt o Encoding: - o Id: TBD (maybe 61) o Reference: [[ this specification ]] -8. References +8.4. CBOR Tag registration -8.1. Normative References + This section registers the CWT CBOR tag in the "CBOR Tags" registry + [IANA.CBOR.Tags] established by [RFC7049]. + +8.4.1. 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 + +9.1. 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] @@ -565,292 +630,293 @@ 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, . -8.2. Informative References +9.2. Informative References - [I-D.seitz-ace-oauth-authz] - Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and - H. Tschofenig, "Authorization for the Internet of Things - using OAuth 2.0", draft-seitz-ace-oauth-authz-00 (work in - progress), October 2015. + [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 - Three examples of CWTs follow. + 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]. -A.1. CWT with "aud" and symmetric key +A.1. Example CWT Claims Set - A CWT used in the context of ACE requires at least the "aud" and a - "cks" claim (defined elsewhere). This means that "iss", "alg", - "key_ops" and others are pre-established and assumed. This would - look like this non-normative JSON. + 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 + + Figure 3: Example CWT Claims Set as hex string { - "aud":"coap://light.example.com", - "cks": - [ // COSE_Key is a CBOR map with an array of keys - { - "kty":4, // symmetric key is indicated using kty 4 - "k": "loremipsum" // the symmetric key - } - ] + / 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' } - Figure 2: "aud" claim and symmetric key in non-normative JSON + Figure 4: Example CWT Claims Set in CBOR diagnostic notation - Using the CBOR encoded claim keys according to Section 4 and COSE - [I-D.ietf-cose-msg] makes a CWT with "aud" and a symmetric key look - like this in CBOR diagnostic notation: +A.2. Example keys - { - 3: "coap://light.example.com", - 8: - [ - { - 1: 4, - -1: "loremipsum" - } - ] - } + This section contains the keys used to sign, MAC, and encrypt the + messages in this appendix. Line breaks are for display purposes + only. - Figure 3: CWT in CBOR diagnostic notation +A.2.1. 128-bit Symmetric Key as Hex Encoded String - Defined in CBOR. + 9e4f3e65cc1a558b39ce97b3db469b04 -a2 # map(2) - 03 # unsigned(3) - 78 18 # text(24) - 636f61703a2f2f6c696768742e6578616d706c652e636f6d # "coap://light.example.com" - 08 # unsigned(8) - 81 # array(1) - a2 # map(2) - 01 # unsigned(1) - 04 # unsigned(4) - 20 # negative(0) - 6a # text(10) - 6c6f72656d697073756d # "loremipsum" +A.2.2. 256-bit Symmetric Key as Hex Encoded String - Figure 4: CWT with "aud" and symmetric key in CBOR + e60198ac1650ec9210d7f4f5b27aeae2ada8f4adada555909edca75ce2ae506e - Size of the CWT with a symmetric key of 10 bytes is 45 bytes. This - is then packaged signed and encrypted using COSE. +A.2.3. ECDSA P-256 256-bit COSE Key -A.2. CWT with "aud" and EC key + a6225820feb11ca73b028a10cf77d58a2dfdf2a11eab8ffeeeaaeeb03097ffee + 9f3ef2fc2358200657fada2568959c49a404583fe237290ebeb1956f3ad3d966 + ea09e33369d7b103260102215820c4f9160fc22682991c59c4d96e8accc2da3c + c7b7a9bc197c7c1e1bc6d0c1dc612001 - Token with "aud" set to "coap://light.example.com" and an EC key with - "kid" set to "11". + Figure 5: ECDSA 256-bit COSE Key as hex string { - "aud": "coap://light.example.com", - "cks": - [ // COSE_Key is a CBOR map with an array of keys - { - "kty": "EC", - "kid": "11", - "crv": 1, // using P-384 - "x": h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', - "y": h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' - } - ] + / d / -4: h'0657fada2568959c49a404583fe237290ebeb1956f3ad3d966 + ea09e33369d7b1', + / y / -3: h'feb11ca73b028a10cf77d58a2dfdf2a11eab8ffeeeaaeeb030 + 97ffee9f3ef2fc', + / x / -2: h'c4f9160fc22682991c59c4d96e8accc2da3cc7b7a9bc197c7c + 1e1bc6d0c1dc61', + / crv / -1: 1 / P-256 / + / kty / 1: 2 / EC2 /, + / alg / 3: -7, \ ECDSA 256 \ } - Figure 5: "aud" claim and EC key in non-normative JSON + Figure 6: ECDSA 256-bit COSE Key in CBOR diagnostic notation - Using the CBOR encoded claim keys according to Section 4 and COSE - [I-D.ietf-cose-msg] makes a CWT with "aud" and an EC key look like - this in CBOR diagnostic notation: +A.3. Example Signed CWT -{ - 3: "coap://light.example.com", - 8: + 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. + + d28446a203183d0126a05850a702656572696b77037818636f61703a2f2f6c69 + 6768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9 + f00175636f61703a2f2f61732e6578616d706c652e636f6d07420b7158407eef + 29abe962ac185e5a372d95d69ce1b5683c5c25efb69a81710dc5173254f5179a + 639827694c22828819704eb026676ca78aaf8da76672a6b5537fb90e710d + + Figure 7: Signed CWT as hex string + + 18( [ - { - 1: 2, - 2: "11", - -1: 1, - -2: h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', - -3: h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' - } + / protected / h'a203183d0126' / { + / content type / 3: 61, / CWT / + / alg / 1: -7 / ECDSA 256 / + } / , + / unprotected / {}, + / payload / h'a702656572696b77037818636f61703a2f2f6c69676874 + 2e6578616d706c652e636f6d041a5612aeb0051a5610d9 + f0061a5610d9f00175636f61703a2f2f61732e6578616d + 706c652e636f6d07420b71' / { + / 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' ] -} + ) - Figure 6: CWT with EC key in CBOR diagnostic notation + Figure 8: Signed CWT in CBOR diagnostic notation - Defined in CBOR. +A.4. Example MACed CWT -a2 # map(2) - 03 # unsigned(3) - 78 18 # text(24) - 636f61703a2f2f6c696768742e6578616d706c652e636f6d # "coap://light.example.com" - 08 # unsigned(8) - 81 # array(1) - a5 # map(5) - 01 # unsigned(1) - 02 # unsigned(2) - 02 # unsigned(2) - 62 # text(2) - 3131 # "11" - 20 # negative(0) - 01 # unsigned(1) - 21 # negative(1) - 58 20 # bytes(32) - bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff # "\xBA\xC5\xB1\x1C\xAD\x8F\x99\xF9\xC7+\x05\xCFK\x9E&\xD2D\xDC\x18\x9FtR(%Z!\x9A\x86\xD6\xA0\x9E\xFF" - 22 # negative(2) - 58 20 # bytes(32) - 20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e # "\x13\x8B\xF8-\xC1\xB6\xD5b\xBE\x0F\xA5J\xB7\x80J:d\xB6\xD7,\xCF\xEDko\xB6\xED(\xBB\xFC\x11~" + This section shows a MACed CWT with a single recipient and a full CWT + Claims Set. - Figure 7: CWT with EC in CBOR + 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. - Size of the CWT with an EC key is 109 bytes. This is then packaged - signed and encrypted using COSE. + d18446a203183d0104a05850a702656572696b77037818636f61703a2f2f6c69 + 6768742e6578616d706c652e636f6d041a5612aeb0051a5610d9f0061a5610d9 + f00175636f61703a2f2f61732e6578616d706c652e636f6d07420b7148b59884 + 6f1ce93f9d -A.3. Full CWT + Figure 9: MACed CWT as hex string - CWT using all claims defined by this specification, plus extensions - for AIF and an EC key. + 17( + [ + / protected / h'a203183d0104' / { + / content type / 3: 61, / CWT / + / alg / 1: 4 / HMAC 256/64 / + } / , + / unprotected / {}, + / payload / h'a702656572696b77037818636f61703a2f2f6c69676874 + 2e6578616d706c652e636f6d041a5612aeb0051a5610d9 + f0061a5610d9f00175636f61703a2f2f61732e6578616d + 706c652e636f6d07420b71' / { + / 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' + ] + ) -{ - "iss": "coap://as.example.com", - "aud": "coap://light.example.com", - "sub": "erikw", - "exp": 1444064944, - "nbf": 1443944944, - "iat": 1443944944, - "cti": 2929, - "cks": - [ // COSE_Key is a CBOR map with an array of keys - { - "kty": "EC", - "kid": "11", - "crv": 1, // using P-384 - "x": h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', - "y": h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' - } - ], - "aif": [["/s/light", 1], ["/a/led", 5], ["/dtls", 2]] - } + Figure 10: MACed CWT in CBOR diagnostic notation - Figure 8: All claims, "aif" and EC key in non-normative JSON +A.5. Example Encrypted CWT - Using the CBOR encoded claim keys according to Section 4 and COSE - [I-D.ietf-cose-msg] makes a full CWT look like this in CBOR - diagnostic notation: + This section shows an encrypted CWT with a single recipient and a + full CWT Claims Set. -{ - 1: "coap://as.example.com", - 3: "coap://light.example.com", - 2: "erikw", - 4: 1(1444064944), - 5: 1(1443944944), - 6: 1(1443944944), - 7: 2929, - 8: [ - { - 1: 2, - 2: "11", - -1: 1, - -2: h'bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff', - -3: h'20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e' - } - ], - 9: [["/s/light", 1], ["/a/led", 5], ["/dtls", 2]] -} + 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. - Figure 9: Full CWT with EC key in CBOR diagnostic notation + d08346a203183d010aa1054dadbe290e8c9c23067a558b15795858f7a8ec3e32 + 3bb6e006e8aec087666f6fc0d65d7aa272f5f1dde1dfb52fd3a5e1ace97e5bfc + 8f05a146fd8a9feab7bb9e722254e2660612f956041264c06ea3b95afb0d8ce3 + 138bc80baf2511565d3dad63ea7534699fa449 - Defined in CBOR. + Figure 11: Encrypted CWT as hex string -a9 # map(9) - 01 # unsigned(1) - 75 # text(21) - 636f61703a2f2f61732e6578616d706c652e636f6d # "coap://as.example.com" - 03 # unsigned(3) - 78 18 # text(24) - 636f61703a2f2f6c696768742e6578616d706c652e636f6d # "coap://light.example.com" - 02 # unsigned(2) - 65 # text(5) - 6572696b77 # "erikw" - 04 # unsigned(4) - c1 # tag(1) - 1a 5612aeb0 # unsigned(1444064944) - 05 # unsigned(5) - c1 # tag(1) - 1a 5610d9f0 # unsigned(1443944944) - 06 # unsigned(6) - c1 # tag(1) - 1a 5610d9f0 # unsigned(1443944944) - 07 # unsigned(7) - 19 0b71 # unsigned(2929) - 08 # unsigned(8) - 81 # array(1) - a5 # map(5) - 01 # unsigned(1) - 02 # unsigned(2) - 02 # unsigned(2) - 62 # text(2) - 3131 # "11" - 20 # negative(0) - 01 # unsigned(1) - 21 # negative(1) - 58 20 # bytes(32) - bac5b11cad8f99f9c72b05cf4b9e26d244dc189f745228255a219a86d6a09eff # "\xBA\xC5\xB1\x1C\xAD\x8F\x99\xF9\xC7+\x05\xCFK\x9E&\xD2D\xDC\x18\x9FtR(%Z!\x9A\x86\xD6\xA0\x9E\xFF" - 22 # negative(2) - 58 20 # bytes(32) - 20138bf82dc1b6d562be0fa54ab7804a3a64b6d72ccfed6b6fb6ed28bbfc117e # "\x13\x8B\xF8-\xC1\xB6\xD5b\xBE\x0F\xA5J\xB7\x80J:d\xB6\xD7,\xCF\xEDko\xB6\xED(\xBB\xFC\x11~" - 09 # unsigned(9) - 83 # array(3) - 82 # array(2) - 68 # text(8) - 2f732f6c69676874 # "/s/light" - 01 # unsigned(1) - 82 # array(2) - 66 # text(6) - 2f612f6c6564 # "/a/led" - 05 # unsigned(5) - 82 # array(2) - 65 # text(5) - 2f64746c73 # "/dtls" - 02 # unsigned(2) + 16( + [ + / protected / h'a203183d010a' / { + / content type / 3: 61, / CWT / + / alg / 1: 10 / AES-CCM-16-64-128 / + } /, + / unprotected / { + / iv / 5: h'adbe290e8c9c23067a558b1579' + }, + / ciphertext / h'f7a8ec3e323bb6e006e8aec087666f6fc0d65d7aa27 + 2f5f1dde1dfb52fd3a5e1ace97e5bfc8f05a146fd8a + 9feab7bb9e722254e2660612f956041264c06ea3b95 + afb0d8ce3138bc80baf2511565d3dad63ea7534699f + a449' + ] + ) - Figure 10: Full CWT with EC in CBOR + Figure 12: Encrypted CWT in CBOR diagnostic notation - Size of the CWT with an EC key is 194 bytes. This is then packaged - signed and encrypted using COSE. +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. + + The signature is generated using the private ECDSA key from + Appendix A.2.3 and it can be validated using the public ECDSA parts + 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 + + 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' + }, + / ciphertext / h'5da538206c33cf941df7ea933ba7b93c60322017f9d + b9c904608fce2688b51028b5b912f9010ae72802bf6 + 5778593c7270b20683b1587824eb4074e03323ccf05 + 41b495a3757f353a8424b6ceeaaec1898964d8a03e0 + 4e514a5b0ca143b57689a2a9f1c6c84d535d1966adf + 900dfaf0dd045d2325c40150a07d602b65c60e62894 + c870ad5fc2cb709e4d17d381806797b6cf118608e18 + c3facd0a0ac09d88ea73d4ed7e3b57c' + ] + ) + + 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. A straw - man proposal of CWT was written in the draft "Authorization for the - Internet of Things using OAuth 2.0" [I-D.seitz-ace-oauth-authz] with - the help of Ludwig Seitz and Goeran Selander. + 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 + + 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. -01 o Added IANA registration for CWT Claims. + o Added IANA registration for the application/cwt CoAP content- format type. o Added Samuel Erdtman as an editor. o Changed Erik's e-mail address. -00 o Created the initial working group version based on draft- wahlstroem-ace-cbor-web-token-00.