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Young, Ed. 3 Internet-Draft Independent 4 Intended status: Informational January 15, 2019 5 Expires: July 19, 2019 7 SAML Profile for the Metadata Query Protocol 8 draft-young-md-query-saml-10 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.11. 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 19, 2019. 45 Copyright Notice 47 Copyright (c) 2019 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 . . . . . . . . . . . . . . . . . . 4 65 2.2.2. Transformed Identifier . . . . . . . . . . . . . . . 4 66 2.2.3. Additional Identifiers . . . . . . . . . . . . . . . 5 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 . . . . . . . . . . . . . . . . . . . 6 73 4.1. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 6 74 4.2. Use of SHA-1 in Transformed Identifiers . . . . . . . . . 6 75 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 76 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 77 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 78 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 79 7.2. Informative References . . . . . . . . . . . . . . . . . 8 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 A.10. Since draft-young-md-query-saml-08 . . . . . . . . . . . 10 92 A.11. Since draft-young-md-query-saml-09 . . . . . . . . . . . 10 94 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 96 1. Introduction 98 This document profiles the Metadata Query Protocol 99 [I-D.young-md-query] for use with SAML metadata [SAML2Meta]. 101 The Research and Education Federations group ([REFEDS]) is the voice 102 that articulates the mutual needs of research and education identity 103 federations worldwide. It aims to represent the requirements of 104 research and education in the ever-growing space of access and 105 identity management. 107 From time to time REFEDS will wish to publish a document in the 108 Internet RFC series. Such documents will be published as part of the 109 RFC Independent Submission Stream [RFC4844]; however the REFEDS 110 working group sign-off process will have been followed for these 111 documents, as described in the REFEDS Participant's Agreement 112 [REFEDS.agreement]. 114 This document is a product of the REFEDS Working Group process. 116 1.1. Notation and Conventions 118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 120 "OPTIONAL" in this document are to be interpreted as described in 121 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 122 capitals, as shown here. 124 This document makes use of the Augmented BNF metalanguage defined in 125 [STD68]. 127 2. Request Profile 129 2.1. Content Type 131 Requests compliant with this profile MUST include the following HTTP 132 header to indicate that the metadata returned should be SAML metadata 133 (see Appendix A of [SAML2Meta]): 135 Accept: application/samlmetadata+xml 137 2.2. Identifiers 138 2.2.1. Unique Identifier 140 Each entity known to the responder MUST be associated with the unique 141 identifier of the entity, corresponding to the "entityID" attribute 142 of the entity's "EntityDescriptor" element in SAML metadata. 144 2.2.2. Transformed Identifier 146 SAML 2.0 [SAML2Core] includes profiles based on the transfer of an 147 "artifact" containing the unique identifier of a SAML entity 148 transformed by means of the SHA-1 [RFC3174] hash algorithm (see 149 [SAML2Bind] sections 3.6 and 3.6.4). 151 In order to support use cases in which clients may be in possession 152 of only such a transformed representation of a SAML entity's unique 153 identifier without any way to establish the original entity 154 identifier, a responder compliant with this profile MUST associate 155 each entity with an identifier matching the "sha1id" production in 156 the following ABNF grammar, and treat such an identifier as 157 equivalent to the corresponding untransformed identifier: 159 SHA1 = %x73 %x68 %x61 %x31 ; lower case "sha1" 160 DIGIT = %x30-39 161 HEXDIGIT = DIGIT | %x61-66 ; lower case a-f 162 sha1id = "{" SHA1 "}" sha1hex 163 sha1hex = 40*HEXDIGIT 165 In the above, the "sha1hex" component encodes the 20-octet (160-bit) 166 binary SHA-1 hash value as a sequence of 40 lower case hexadecimal 167 digits. 169 For example, the identifier 171 http://example.org/service 173 transformed by means of SHA-1 hashing would become 175 {sha1}11d72e8cf351eb6c75c721e838f469677ab41bdb 177 Responder implementations MAY detect malformed SHA-1 transformed 178 identifiers (for example where the string of characters following the 179 "}" contains characters other than hexadecimal digits, or is other 180 than exactly 40 characters in length) and return an HTTP status code 181 of 400 ("bad request"). Alternatively, implementations MAY process 182 these as normal identifiers and return an HTTP status code of 404 183 ("not found") if appropriate. 185 2.2.3. Additional Identifiers 187 Entities MAY also be associated with any number of additional 188 responder-defined identifiers naming arbitrary groups of entities. 190 3. Response Profile 192 3.1. Response Cardinality 194 A request may return information for any number of entities, 195 including none. Responses compliant with this profile MUST use the 196 appropriate representation described below depending on the number of 197 "EntityDescriptor" elements returned. 199 3.1.1. No Entity Descriptors Returned 201 A response which returns no "EntityDescriptor" elements MUST be 202 represented by an HTTP status code of 404 ("not found"). 204 3.1.2. One Entity Descriptor Returned 206 A response which returns a single "EntityDescriptor" element MUST use 207 that element as its document element. The responder MUST NOT make 208 use of a "EntitiesDescriptor" element in this situation (see 209 [SAML2Meta] section 2.3). 211 Such a response MUST include the following HTTP header to indicate 212 that the metadata returned is SAML metadata: 214 Content-Type: application/samlmetadata+xml 216 3.1.3. More Than One Entity Descriptor Returned 218 A response which returns more than one "EntityDescriptor" element 219 MUST consist of a document element which is an "EntitiesDescriptor" 220 element, containing the returned "EntityDescriptor" elements as 221 children. Responses MUST NOT contain nested "EntitiesDescriptor" 222 elements. 224 Such a response MUST include the following HTTP header to indicate 225 that the metadata returned is SAML metadata: 227 Content-Type: application/samlmetadata+xml 229 4. Security Considerations 231 4.1. Integrity 233 As SAML metadata contains information necessary for the secure 234 operation of interacting services it is strongly RECOMMENDED that a 235 mechanism for integrity checking is provided to clients. 237 It is RECOMMENDED that the integrity checking mechanism provided by a 238 responder is a digital signature embedded in the returned metadata 239 document, as defined by [SAML2Meta] section 3. 241 Such digital signatures: 243 o SHOULD use an RSA keypair whose modulus is no less than 2048 bits 244 in length. 246 o SHOULD NOT use the SHA-1 cryptographic hash algorithm as a digest 247 algorithm. 249 o MUST NOT use the MD5 cryptographic hash algorithm as a digest 250 algorithm. 252 o SHOULD otherwise follow current cryptographic best practices in 253 algorithm selection. 255 4.2. Use of SHA-1 in Transformed Identifiers 257 This profile mandates the availability of a identifier synonym 258 mechanism based on the SHA-1 cryptographic hash algorithm. Although 259 SHA-1 is now regarded as weak enough to exclude it from use in new 260 cryptographic systems, its use in this profile is necessary for full 261 support of the SAML 2.0 standard. 263 Because the SHA-1 cryptographic hash is not being used within this 264 profile in the context of a digital signature, it is not believed to 265 introduce a security concern over and above that which already exists 266 in SAML due to the possibility of a post-hash collision between 267 entities whose "entityID" attributes hash to the same value. 269 Implementations may guard against this possibility by treating two 270 entities whose "entityID" values have the same SHA-1 equivalent as an 271 indicator of malicious intent on the part of the owner of one of the 272 entities. 274 5. IANA Considerations 276 This document has no actions for IANA. 278 6. Acknowledgements 280 The editor would like to acknowledge the following individuals for 281 their contributions to this document: 283 Scott Cantor (The Ohio State University) 285 Leif Johansson (SUNET) 287 Joe St Sauver (University of Oregon) 289 Tom Scavo (Internet2) 291 7. References 293 7.1. Normative References 295 [I-D.young-md-query] 296 Young, I., Ed., "Metadata Query Protocol", draft-young-md- 297 query-10 (work in progress), January 2019. 299 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 300 Requirement Levels", BCP 14, RFC 2119, 301 DOI 10.17487/RFC2119, March 1997, 302 . 304 [RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash Algorithm 1 305 (SHA1)", RFC 3174, DOI 10.17487/RFC3174, September 2001, 306 . 308 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 309 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 310 May 2017, . 312 [SAML2Bind] 313 Cantor, S., Hirsch, F., Kemp, J., Philpott, R., and E. 314 Maler, "Bindings for the Security Assertion Markup 315 Language (SAML) V2.0", OASIS Standard saml-bindings- 316 2.0-os, March 2005. 318 [SAML2Meta] 319 Cantor, S., Moreh, J., Philpott, R., and E. Maler, 320 "Metadata for the Security Assertion Markup Language 321 (SAML) V2.0", OASIS Standard saml-metadata-2.0-os, March 322 2005. 324 [STD68] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 325 Specifications: ABNF", STD 68, RFC 5234, 326 DOI 10.17487/RFC5234, January 2008, 327 . 329 7.2. Informative References 331 [md-query] 332 Young, I., Ed., "md-query Project", 333 . 335 [MDX.list] 336 Young, I., Ed., "MDX Mailing List", 337 . 339 [REFEDS] Research and Education Federations, "REFEDS Home Page", 340 . 342 [REFEDS.agreement] 343 Research and Education Federations, "REFEDS Participant's 344 Agreement", 345 . 347 [RFC4844] Daigle, L., Ed. and Internet Architecture Board, "The RFC 348 Series and RFC Editor", RFC 4844, DOI 10.17487/RFC4844, 349 July 2007, . 351 [SAML2Core] 352 Cantor, S., Kemp, J., Philpott, R., and E. Maler, 353 "Assertions and Protocol for the OASIS Security Assertion 354 Markup Language (SAML) V2.0", OASIS Standard saml-core- 355 2.0-os, March 2005, . 358 Appendix A. Change Log (to be removed by RFC Editor before publication) 360 A.1. draft-young-md-query-saml-00 362 Initial version. 364 A.2. Since draft-young-md-query-saml-00 366 Added REFEDS RFC stream boilerplate. 368 A.3. Since draft-young-md-query-saml-01 370 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 372 Rework Section 2.2 to make the role of transformed identifiers 373 clearer. This changes the semantics slightly (malformed transformed 374 identifiers may now result in a 404 return rather than 400) but this 375 gives implementers more latitude in the way that they handle the 376 feature. 378 A.4. Since draft-young-md-query-saml-02 380 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 382 A.5. Since draft-young-md-query-saml-03 384 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 386 Added an Editorial Note to help direct readers back to the 387 discussion. 389 A.6. Since draft-young-md-query-saml-04 391 Fix reference to the Metadata Query Protocol [I-D.young-md-query]. 393 A.7. Since draft-young-md-query-saml-05 395 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 397 A.8. Since draft-young-md-query-saml-06 399 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 401 A.9. Since draft-young-md-query-saml-07 403 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 405 A.10. Since draft-young-md-query-saml-08 407 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 409 Modernise normative language to include [RFC8174]. 411 Improved references to RFCs. 413 A.11. Since draft-young-md-query-saml-09 415 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 417 Author's Address 419 Ian A. Young (editor) 420 Independent 422 EMail: ian@iay.org.uk