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Seitz 3 Internet-Draft RISE 4 Intended status: Standards Track September 18, 2018 5 Expires: March 22, 2019 7 Additional OAuth Parameters for Authorization in Constrained 8 Environments (ACE) 9 draft-ietf-ace-oauth-params-00 11 Abstract 13 This specification defines new parameters for the OAuth 2.0 token and 14 introspection endpoints when used with framework for authentication 15 and authorization for constrained environments (ACE). These are used 16 to express the desired audience of a requested access token, the 17 desired proof-of-possession key, the proof-of-possession key that the 18 AS has selected, and the key the RS should use to authenticate to the 19 client. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on March 22, 2019. 38 Copyright Notice 40 Copyright (c) 2018 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 57 3. Parameters for the Token Endpoint . . . . . . . . . . . . . . 3 58 3.1. Client-to-AS Request . . . . . . . . . . . . . . . . . . 3 59 3.2. AS-to-Client Response . . . . . . . . . . . . . . . . . . 3 60 4. Parameters for the Introspection Endpoint . . . . . . . . . . 4 61 4.1. AS-to-RS Response . . . . . . . . . . . . . . . . . . . . 4 62 5. Confirmation Method Parameters . . . . . . . . . . . . . . . 4 63 6. CBOR Mappings . . . . . . . . . . . . . . . . . . . . . . . . 5 64 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 65 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 5 66 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 67 9.1. OAuth Parameter Registration . . . . . . . . . . . . . . 6 68 9.2. OAuth Introspection Response Parameter Registration . . . 6 69 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6 70 11. Normative References . . . . . . . . . . . . . . . . . . . . 7 71 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8 73 1. Introduction 75 The Authorization for the Internet of Things specification 76 [I-D.ietf-ace-oauth-authz] requires some new parameters for requests 77 and responses to the OAuth 2.0 [RFC6749] token and introspection 78 endpoints, as well as some new claims to be used in access tokens. 79 This document specifies these new parameters and claims separately 80 from the framework, so they can be used and updated independently. 82 2. Terminology 84 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 85 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 86 "OPTIONAL" in this document are to be interpreted as described in BCP 87 14 [RFC2119] [RFC8174] when, and only when, they appear in all 88 capitals, as shown here. 90 Readers are assumed to be familiar with the terminology from 91 [I-D.ietf-ace-oauth-authz]. 93 Note that the term "endpoint" is used here following its OAuth 2.0 94 [RFC6749] definition, which is to denote resources such as token and 95 introspection at the AS and authz-info at the RS. The CoAP [RFC7252] 96 definition, which is "An entity participating in the CoAP protocol" 97 is not used in this specification. 99 3. Parameters for the Token Endpoint 101 3.1. Client-to-AS Request 103 This document defines the following additional parameters for 104 requesting an access token from a token endpoint in the ACE framework 105 [I-D.ietf-ace-oauth-authz]: 107 req_aud 108 OPTIONAL. Specifies the audience for which the client is 109 requesting an access token. If this parameter is missing, it is 110 assumed that the AS has a default audience for access tokens 111 issued to this client. If a client submits a request for an 112 access token without specifying a "req_aud" parameter, and the AS 113 does not have a default audience value for this client, then the 114 AS MUST respond with an error message using a response code 115 equivalent to the CoAP response code 4.00 (Bad Request). 117 req_cnf 118 OPTIONAL. This field contains information about the key the 119 client would like to bind to the access token for proof-of- 120 possession. It is RECOMMENDED that an AS reject a request 121 containing a symmetric key value in the 'req_cnf' field, since the 122 AS is expected to be able to generate better symmetric keys than a 123 potentially constrained client. See Section 5 for more details on 124 the use of this parameter. 126 3.2. AS-to-Client Response 128 This document defines the following additional parameters for an AS 129 response to a request to the token endpoint: 131 cnf 132 REQUIRED if the token type is "pop" and a symmetric key is used. 133 MAY be present for asymmetric proof-of-possession keys. This 134 field contains the proof-of-possession key that the AS selected 135 for the token. See Section 5 for details on the use of this 136 parameter. 138 rs_cnf 139 OPTIONAL if the token type is "pop" and asymmetric keys are used. 140 MUST NOT be present otherwise. This field contains information 141 about the public key used by the RS to authenticate. If this 142 parameter is absent, either the RS does not use a public key or 143 the AS assumes that the client already knows the public key of the 144 RS. See Section 5 for details on the use of this parameter. 146 4. Parameters for the Introspection Endpoint 148 4.1. AS-to-RS Response 150 This document defines the following additional parameters for an AS 151 response to a request to the introspection endpoint: 153 cnf 154 OPTIONAL. This field contains information about the proof-of- 155 possession key that binds the client to the access token. See 156 Section 5 for more details on the use of the "cnf" parameter. 158 rs_cnf 159 OPTIONAL. If the RS has several keys it can use to authenticate 160 towards the client, the AS can give the RS a hint using this 161 parameter, as to which key it should use (e.g., if the AS 162 previously informed the client about a public key the RS is 163 holding). See Section 5 for more details on the use of this 164 parameter. 166 5. Confirmation Method Parameters 168 The confirmation method parameters are used as follows: 170 o "req_cnf" in the token request C -> AS, OPTIONAL to indicate the 171 client's raw public key, or the key-identifier of a previously 172 established key between C and RS that the client wishes to use for 173 proof-of-possession of the access token. 174 o "cnf" in the token response AS -> C, OPTIONAL if using an 175 asymmetric key or a key that the client requested via a key 176 identifier in the request. REQUIRED if the client didn't specify 177 a "req_cnf" and symmetric keys are used. Used to indicate the 178 symmetric key generated by the AS for proof-of-possession of the 179 access token. 180 o "cnf" in the introspection response AS -> RS, REQUIRED if the 181 token that was subject to introspection is a proof-of-possession 182 token, absent otherwise. Indicates the proof-of-possession key 183 bound to the token. 184 o "rs_cnf" in the token response AS -> C, OPTIONAL to indicate the 185 public key of the RS if it has one. 186 o "rs_cnf" in the introspection response AS -> RS, OPTIONAL to 187 indicate to the RS which asymmetric key pair to use for 188 authenticating to the client if the RS has several public keys. 190 All confirmation parameters use the same formatting and semantics as 191 the "cnf" claim specified in [I-D.ietf-ace-cwt-proof-of-possession] 192 when used with a CBOR encoding. When these parameters are used with 193 a JSON encoding, the formatting and semantics of the "cnf" claim 194 specified in [RFC7800] is used. 196 Note that the COSE_Key structure in a confirmation claim or parameter 197 may contain an "alg" or "key_ops" parameter. If such parameters are 198 present, a client MUST NOT use a key that is not compatible with the 199 profile or proof-of-possession algorithm according to those 200 parameters. An RS MUST reject a proof-of-possession using such a 201 key. 203 If an access token is issued for an audience that includes several 204 RS, the "rs_cnf" parameter MUST NOT be used, since the client cannot 205 determine for which RS the key applies. This document recommends to 206 specify a different endpoint that the client can use to acquire RS 207 authentication keys in such cases. The specification of such an 208 endpoint is out of scope for this document. 210 6. CBOR Mappings 212 If CBOR is used, the new parameters and claims defined in this 213 document MUST be mapped to CBOR types as specified in Figure 1, using 214 the given integer abbreviation for the map key. 216 /-----------------+----------+----------------------------------\ 217 | Parameter name | CBOR Key | Value Type | 218 |-----------------+----------+----------------------------------| 219 | cnf | 8 | map | 220 | rs_cnf | 17 | map | 221 | req_aud | 18 | text string | 222 | req_cnf | 19 | map | 223 \-----------------+----------+----------------------------------/ 225 Figure 1: CBOR mappings for new parameters. 227 7. Security Considerations 229 This document is an extension to [I-D.ietf-ace-oauth-authz]. All 230 security considerations from that document apply here as well. 232 8. Privacy Considerations 234 This document is an extension to [I-D.ietf-ace-oauth-authz]. All 235 privacy considerations from that document apply here as well. 237 9. IANA Considerations 239 9.1. OAuth Parameter Registration 241 This section registers the following parameters in the "OAuth 242 Parameters" registry [IANA.OAuthParameters]: 244 o Name: "req_aud" 245 o Parameter Usage Location: authorization request, token request 246 o Change Controller: IESG 247 o Reference: Section 3.1 of [this document] 249 o Name: "req_cnf" 250 o Parameter Usage Location: token request 251 o Change Controller: IESG 252 o Reference: Section 5 of [this document] 254 o Name: "rs_cnf" 255 o Parameter Usage Location: token response 256 o Change Controller: IESG 257 o Reference: Section 5 of [this document] 259 o Name: "cnf" 260 o Parameter Usage Location: token response 261 o Change Controller: IESG 262 o Reference: Section 5 of [this document] 264 9.2. OAuth Introspection Response Parameter Registration 266 This section registers the following parameters in the OAuth Token 267 Introspection Response registry [IANA.TokenIntrospectionResponse]. 269 o Name: "cnf" 270 o Description: Key to prove the right to use a PoP token. 271 o Change Controller: IESG 272 o Reference: Section 4.1 of [this document] 274 o Name: "rs_cnf" 275 o Description: The key the RS should use to authenticate to the 276 client. 277 o Change Controller: IESG 278 o Reference: Section 4.1 of [this document] 280 10. Acknowledgments 282 This document is a product of the ACE working group of the IETF. 284 Ludwig Seitz worked on this document as part of the CelticPlus 285 project CyberWI, with funding from Vinnova. 287 11. Normative References 289 [I-D.ietf-ace-cwt-proof-of-possession] 290 Jones, M., Seitz, L., Selander, G., Erdtman, S., and H. 291 Tschofenig, "Proof-of-Possession Key Semantics for CBOR 292 Web Tokens (CWTs)", draft-ietf-ace-cwt-proof-of- 293 possession-03 (work in progress), June 2018. 295 [I-D.ietf-ace-oauth-authz] 296 Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and 297 H. Tschofenig, "Authentication and Authorization for 298 Constrained Environments (ACE) using the OAuth 2.0 299 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-13 300 (work in progress), July 2018. 302 [IANA.OAuthParameters] 303 IANA, "OAuth Parameters", 304 . 307 [IANA.TokenIntrospectionResponse] 308 IANA, "OAuth Token Introspection Response", 309 . 312 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 313 Requirement Levels", BCP 14, RFC 2119, 314 DOI 10.17487/RFC2119, March 1997, . 317 [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", 318 RFC 6749, DOI 10.17487/RFC6749, October 2012, 319 . 321 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 322 Application Protocol (CoAP)", RFC 7252, 323 DOI 10.17487/RFC7252, June 2014, . 326 [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- 327 Possession Key Semantics for JSON Web Tokens (JWTs)", 328 RFC 7800, DOI 10.17487/RFC7800, April 2016, 329 . 331 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 332 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 333 May 2017, . 335 Author's Address 337 Ludwig Seitz 338 RISE 339 Scheelevaegen 17 340 Lund 223 70 341 Sweden 343 Email: ludwig.seitz@ri.se