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Young, Ed. 3 Internet-Draft Independent 4 Intended status: Informational January 10, 2018 5 Expires: July 14, 2018 7 SAML Profile for the Metadata Query Protocol 8 draft-young-md-query-saml-08 10 Abstract 12 This document profiles the Metadata Query Protocol 13 [I-D.young-md-query] for use with SAML metadata [SAML2Meta]. 15 This document is a product of the Research and Education Federations 16 (REFEDS) Working Group process. 18 Editorial Note (To be removed by RFC Editor before publication) 20 Discussion of this draft takes place on the MDX mailing list 21 (mdx@lists.iay.org.uk), which is accessed from [MDX.list]. 23 XML versions, latest edits and the issues list for this document are 24 available from [md-query]. 26 The changes in this draft are summarized in Appendix A.9. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on July 14, 2018. 45 Copyright Notice 47 Copyright (c) 2018 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.1. Notation and Conventions . . . . . . . . . . . . . . . . 3 61 2. Request Profile . . . . . . . . . . . . . . . . . . . . . . . 3 62 2.1. Content Type . . . . . . . . . . . . . . . . . . . . . . 3 63 2.2. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 3 64 2.2.1. Unique Identifier . . . . . . . . . . . . . . . . . . 3 65 2.2.2. Transformed Identifier . . . . . . . . . . . . . . . 4 66 2.2.3. Additional Identifiers . . . . . . . . . . . . . . . 4 67 3. Response Profile . . . . . . . . . . . . . . . . . . . . . . 5 68 3.1. Response Cardinality . . . . . . . . . . . . . . . . . . 5 69 3.1.1. No Entity Descriptors Returned . . . . . . . . . . . 5 70 3.1.2. One Entity Descriptor Returned . . . . . . . . . . . 5 71 3.1.3. More Than One Entity Descriptor Returned . . . . . . 5 72 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 73 4.1. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 5 74 4.2. Use of SHA-1 in Transformed Identifiers . . . . . . . . . 6 75 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 76 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 77 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 78 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 79 7.2. Informative References . . . . . . . . . . . . . . . . . 7 80 Appendix A. Change Log (to be removed by RFC Editor before 81 publication) . . . . . . . . . . . . . . . . . . . . 9 82 A.1. draft-young-md-query-saml-00 . . . . . . . . . . . . . . 9 83 A.2. Since draft-young-md-query-saml-00 . . . . . . . . . . . 9 84 A.3. Since draft-young-md-query-saml-01 . . . . . . . . . . . 9 85 A.4. Since draft-young-md-query-saml-02 . . . . . . . . . . . 9 86 A.5. Since draft-young-md-query-saml-03 . . . . . . . . . . . 9 87 A.6. Since draft-young-md-query-saml-04 . . . . . . . . . . . 9 88 A.7. Since draft-young-md-query-saml-05 . . . . . . . . . . . 9 89 A.8. Since draft-young-md-query-saml-06 . . . . . . . . . . . 9 90 A.9. Since draft-young-md-query-saml-07 . . . . . . . . . . . 9 91 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 93 1. Introduction 95 This document profiles the Metadata Query Protocol 96 [I-D.young-md-query] for use with SAML metadata [SAML2Meta]. 98 The Research and Education Federations group ([REFEDS]) is the voice 99 that articulates the mutual needs of research and education identity 100 federations worldwide. It aims to represent the requirements of 101 research and education in the ever-growing space of access and 102 identity management. 104 From time to time REFEDS will wish to publish a document in the 105 Internet RFC series. Such documents will be published as part of the 106 RFC Independent Submission Stream [RFC4844]; however the REFEDS 107 working group sign-off process will have been followed for these 108 documents, as described in the REFEDS Participant's Agreement 109 [REFEDS.agreement]. 111 This document is a product of the REFEDS Working Group process. 113 1.1. Notation and Conventions 115 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 116 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 117 document are to be interpreted as described in RFC 2119 [BCP14]. 119 This document makes use of the Augmented BNF metalanguage defined in 120 [STD68]. 122 2. Request Profile 124 2.1. Content Type 126 Requests compliant with this profile MUST include the following HTTP 127 header to indicate that the metadata returned should be SAML metadata 128 (see Appendix A of [SAML2Meta]): 130 Accept: application/samlmetadata+xml 132 2.2. Identifiers 134 2.2.1. Unique Identifier 136 Each entity known to the responder MUST be associated with the unique 137 identifier of the entity, corresponding to the "entityID" attribute 138 of the entity's "EntityDescriptor" element in SAML metadata. 140 2.2.2. Transformed Identifier 142 SAML 2.0 [SAML2Core] includes profiles based on the transfer of an 143 "artifact" containing the unique identifier of a SAML entity 144 transformed by means of the SHA-1 [RFC3174] hash algorithm (see 145 [SAML2Bind] sections 3.6 and 3.6.4). 147 In order to support use cases in which clients may be in possession 148 of only such a transformed representation of a SAML entity's unique 149 identifier without any way to establish the original entity 150 identifier, a responder compliant with this profile MUST associate 151 each entity with an identifier matching the "sha1id" production in 152 the following ABNF grammar, and treat such an identifier as 153 equivalent to the corresponding untransformed identifier: 155 SHA1 = %x73 %x68 %x61 %x31 ; lower case "sha1" 156 DIGIT = %x30-39 157 HEXDIGIT = DIGIT | %x61-66 ; lower case a-f 158 sha1id = "{" SHA1 "}" sha1hex 159 sha1hex = 40*HEXDIGIT 161 In the above, the "sha1hex" component encodes the 20-octet (160-bit) 162 binary SHA-1 hash value as a sequence of 40 lower case hexadecimal 163 digits. 165 For example, the identifier 167 http://example.org/service 169 transformed by means of SHA-1 hashing would become 171 {sha1}11d72e8cf351eb6c75c721e838f469677ab41bdb 173 Responder implementations MAY detect malformed SHA-1 transformed 174 identifiers (for example where the string of characters following the 175 "}" contains characters other than hexadecimal digits, or is other 176 than exactly 40 characters in length) and return an HTTP status code 177 of 400 ("bad request"). Alternatively, implementations MAY process 178 these as normal identifiers and return an HTTP status code of 404 179 ("not found") if appropriate. 181 2.2.3. Additional Identifiers 183 Entities MAY also be associated with any number of additional 184 responder-defined identifiers naming arbitrary groups of entities. 186 3. Response Profile 188 3.1. Response Cardinality 190 A request may return information for any number of entities, 191 including none. Responses compliant with this profile MUST use the 192 appropriate representation described below depending on the number of 193 "EntityDescriptor" elements returned. 195 3.1.1. No Entity Descriptors Returned 197 A response which returns no "EntityDescriptor" elements MUST be 198 represented by an HTTP status code of 404 ("not found"). 200 3.1.2. One Entity Descriptor Returned 202 A response which returns a single "EntityDescriptor" element MUST use 203 that element as its document element. The responder MUST NOT make 204 use of a "EntitiesDescriptor" element in this situation (see 205 [SAML2Meta] section 2.3). 207 Such a response MUST include the following HTTP header to indicate 208 that the metadata returned is SAML metadata: 210 Content-Type: application/samlmetadata+xml 212 3.1.3. More Than One Entity Descriptor Returned 214 A response which returns more than one "EntityDescriptor" element 215 MUST consist of a document element which is an "EntitiesDescriptor" 216 element, containing the returned "EntityDescriptor" elements as 217 children. Responses MUST NOT contain nested "EntitiesDescriptor" 218 elements. 220 Such a response MUST include the following HTTP header to indicate 221 that the metadata returned is SAML metadata: 223 Content-Type: application/samlmetadata+xml 225 4. Security Considerations 227 4.1. Integrity 229 As SAML metadata contains information necessary for the secure 230 operation of interacting services it is strongly RECOMMENDED that a 231 mechanism for integrity checking is provided to clients. 233 It is RECOMMENDED that the integrity checking mechanism provided by a 234 responder is a digital signature embedded in the returned metadata 235 document, as defined by [SAML2Meta] section 3. 237 Such digital signatures: 239 o SHOULD use an RSA keypair whose modulus is no less than 2048 bits 240 in length. 242 o SHOULD NOT use the SHA-1 cryptographic hash algorithm as a digest 243 algorithm. 245 o MUST NOT use the MD5 cryptographic hash algorithm as a digest 246 algorithm. 248 o SHOULD otherwise follow current cryptographic best practices in 249 algorithm selection. 251 4.2. Use of SHA-1 in Transformed Identifiers 253 This profile mandates the availability of a identifier synonym 254 mechanism based on the SHA-1 cryptographic hash algorithm. Although 255 SHA-1 is now regarded as weak enough to exclude it from use in new 256 cryptographic systems, its use in this profile is necessary for full 257 support of the SAML 2.0 standard. 259 Because the SHA-1 cryptographic hash is not being used within this 260 profile in the context of a digital signature, it is not believed to 261 introduce a security concern over and above that which already exists 262 in SAML due to the possibility of a post-hash collision between 263 entities whose "entityID" attributes hash to the same value. 265 Implementations may guard against this possibility by treating two 266 entities whose "entityID" values have the same SHA-1 equivalent as an 267 indicator of malicious intent on the part of the owner of one of the 268 entities. 270 5. IANA Considerations 272 This document has no actions for IANA. 274 6. Acknowledgements 276 The editor would like to acknowledge the following individuals for 277 their contributions to this document: 279 Scott Cantor (The Ohio State University) 280 Leif Johansson (SUNET) 282 Joe St Sauver (University of Oregon) 284 Tom Scavo (Internet2) 286 7. References 288 7.1. Normative References 290 [BCP14] Bradner, S., "Key words for use in RFCs to Indicate 291 Requirement Levels", BCP 14, RFC 2119, March 1997. 293 [I-D.young-md-query] 294 Young, I., Ed., "Metadata Query Protocol", draft-young-md- 295 query-08 (work in progress), January 2018. 297 [RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1 298 (SHA1)", RFC 3174, September 2001. 300 [SAML2Bind] 301 Cantor, S., Hirsch, F., Kemp, J., Philpott, R., and E. 302 Maler, "Bindings for the Security Assertion Markup 303 Language (SAML) V2.0", OASIS Standard saml-bindings- 304 2.0-os, March 2005. 306 [SAML2Meta] 307 Cantor, S., Moreh, J., Philpott, R., and E. Maler, 308 "Metadata for the Security Assertion Markup Language 309 (SAML) V2.0", OASIS Standard saml-metadata-2.0-os, March 310 2005. 312 [STD68] Crocker, D. and P. Overell, "Augmented BNF for Syntax 313 Specifications: ABNF", STD 68, RFC 5234, January 2008. 315 7.2. Informative References 317 [md-query] 318 Young, I., Ed., "md-query Project", 319 . 321 [MDX.list] 322 Young, I., Ed., "MDX Mailing List", 323 . 325 [REFEDS] Research and Education Federations, "REFEDS Home Page", 326 . 328 [REFEDS.agreement] 329 Research and Education Federations, "REFEDS Participant's 330 Agreement", 331 . 333 [RFC4844] Daigle, L. and Internet Architecture Board, "The RFC 334 Series and RFC Editor", RFC 4844, July 2007. 336 [SAML2Core] 337 Cantor, S., Kemp, J., Philpott, R., and E. Maler, 338 "Assertions and Protocol for the OASIS Security Assertion 339 Markup Language (SAML) V2.0", OASIS Standard saml-core- 340 2.0-os, March 2005, . 343 Appendix A. Change Log (to be removed by RFC Editor before publication) 345 A.1. draft-young-md-query-saml-00 347 Initial version. 349 A.2. Since draft-young-md-query-saml-00 351 Added REFEDS RFC stream boilerplate. 353 A.3. Since draft-young-md-query-saml-01 355 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 357 Rework Section 2.2 to make the role of transformed identifiers 358 clearer. This changes the semantics slightly (malformed transformed 359 identifiers may now result in a 404 return rather than 400) but this 360 gives implementers more latitude in the way that they handle the 361 feature. 363 A.4. Since draft-young-md-query-saml-02 365 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 367 A.5. Since draft-young-md-query-saml-03 369 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 371 Added an Editorial Note to help direct readers back to the 372 discussion. 374 A.6. Since draft-young-md-query-saml-04 376 Fix reference to the Metadata Query Protocol [I-D.young-md-query]. 378 A.7. Since draft-young-md-query-saml-05 380 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 382 A.8. Since draft-young-md-query-saml-06 384 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 386 A.9. Since draft-young-md-query-saml-07 388 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 390 Author's Address 392 Ian A. Young (editor) 393 Independent 395 EMail: ian@iay.org.uk