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Young, Ed. 3 Internet-Draft Independent 4 Intended status: Informational April 24, 2015 5 Expires: October 26, 2015 7 SAML Profile for the Metadata Query Protocol 8 draft-young-md-query-saml-04 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.5. 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 http://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 October 26, 2015. 45 Copyright Notice 47 Copyright (c) 2015 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 (http://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 . . . . . . . . . . . . . . . . . . . . . . . . 2 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 . . . . . . . . . . . . . . . 3 66 2.2.3. Additional Identifiers . . . . . . . . . . . . . . . 4 67 3. Response Profile . . . . . . . . . . . . . . . . . . . . . . 4 68 3.1. Response Cardinality . . . . . . . . . . . . . . . . . . 4 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 88 1. Introduction 90 This document profiles the Metadata Query Protocol 91 [I-D.young-md-query] for use with SAML metadata [SAML2Meta]. 93 The Research and Education Federations group ([REFEDS]) is the voice 94 that articulates the mutual needs of research and education identity 95 federations worldwide. It aims to represent the requirements of 96 research and education in the ever-growing space of access and 97 identity management. 99 From time to time REFEDS will wish to publish a document in the 100 Internet RFC series. Such documents will be published as part of the 101 RFC Independent Submission Stream [RFC4844]; however the REFEDS 102 working group sign-off process will have been followed for these 103 documents, as described in the REFEDS Participant's Agreement 104 [REFEDS.agreement]. 106 This document is a product of the REFEDS Working Group process. 108 1.1. Notation and Conventions 110 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 111 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 112 document are to be interpreted as described in RFC 2119 [BCP14]. 114 This document makes use of the Augmented BNF metalanguage defined in 115 [STD68]. 117 2. Request Profile 119 2.1. Content Type 121 Requests compliant with this profile MUST include the following HTTP 122 header to indicate that the metadata returned should be SAML metadata 123 (see Appendix A of [SAML2Meta]): 125 Accept: application/samlmetadata+xml 127 2.2. Identifiers 129 2.2.1. Unique Identifier 131 Each entity known to the responder MUST be associated with the unique 132 identifier of the entity, corresponding to the "entityID" attribute 133 of the entity's "EntityDescriptor" element in SAML metadata. 135 2.2.2. Transformed Identifier 137 SAML 2.0 [SAML2Core] includes profiles based on the transfer of an 138 "artifact" containing the unique identifier of a SAML entity 139 transformed by means of the SHA-1 [RFC3174] hash algorithm (see 140 [SAML2Bind] sections 3.6 and 3.6.4). 142 In order to support use cases in which clients may be in possession 143 of only such a transformed representation of a SAML entity's unique 144 identifier without any way to establish the original entity 145 identifier, a responder compliant with this profile MUST associate 146 each entity with an identifier matching the "sha1id" production in 147 the following ABNF grammar, and treat such an identifier as 148 equivalent to the corresponding untransformed identifier: 150 SHA1 = %x73 %x68 %x61 %x31 ; lower case "sha1" 151 DIGIT = %x30-39 152 HEXDIGIT = DIGIT | %x61-66 ; lower case a-f 153 sha1id = "{" SHA1 "}" sha1hex 154 sha1hex = 40*HEXDIGIT 156 In the above, the "sha1hex" component encodes the 20-octet (160-bit) 157 binary SHA-1 hash value as a sequence of 40 lower case hexadecimal 158 digits. 160 For example, the identifier 162 http://example.org/service 164 transformed by means of SHA-1 hashing would become 166 {sha1}11d72e8cf351eb6c75c721e838f469677ab41bdb 168 Responder implementations MAY detect malformed SHA-1 transformed 169 identifiers (for example where the string of characters following the 170 "}" contains characters other than hexadecimal digits, or is other 171 than exactly 40 characters in length) and return an HTTP status code 172 of 400 ("bad request"). Alternatively, implementations MAY process 173 these as normal identifiers and return an HTTP status code of 404 174 ("not found") if appropriate. 176 2.2.3. Additional Identifiers 178 Entities MAY also be associated with any number of additional 179 responder-defined identifiers naming arbitrary groups of entities. 181 3. Response Profile 183 3.1. Response Cardinality 185 A request may return information for any number of entities, 186 including none. Responses compliant with this profile MUST use the 187 appropriate representation described below depending on the number of 188 "EntityDescriptor" elements returned. 190 3.1.1. No Entity Descriptors Returned 192 A response which returns no "EntityDescriptor" elements MUST be 193 represented by an HTTP status code of 404 ("not found"). 195 3.1.2. One Entity Descriptor Returned 197 A response which returns a single "EntityDescriptor" element MUST use 198 that element as its document element. The responder MUST NOT make 199 use of a "EntitiesDescriptor" element in this situation (see 200 [SAML2Meta] section 2.3). 202 Such a response MUST include the following HTTP header to indicate 203 that the metadata returned is SAML metadata: 205 Content-Type: application/samlmetadata+xml 207 3.1.3. More Than One Entity Descriptor Returned 209 A response which returns more than one "EntityDescriptor" element 210 MUST consist of a document element which is an "EntitiesDescriptor" 211 element, containing the returned "EntityDescriptor" elements as 212 children. Responses MUST NOT contain nested "EntitiesDescriptor" 213 elements. 215 Such a response MUST include the following HTTP header to indicate 216 that the metadata returned is SAML metadata: 218 Content-Type: application/samlmetadata+xml 220 4. Security Considerations 222 4.1. Integrity 224 As SAML metadata contains information necessary for the secure 225 operation of interacting services it is strongly RECOMMENDED that a 226 mechanism for integrity checking is provided to clients. 228 It is RECOMMENDED that the integrity checking mechanism provided by a 229 responder is a digital signature embedded in the returned metadata 230 document, as defined by [SAML2Meta] section 3. 232 Such digital signatures: 234 o SHOULD use an RSA keypair whose modulus is no less than 2048 bits 235 in length. 237 o SHOULD NOT use the SHA-1 cryptographic hash algorithm as a digest 238 algorithm. 240 o MUST NOT use the MD5 cryptographic hash algorithm as a digest 241 algorithm. 243 o SHOULD otherwise follow current cryptographic best practices in 244 algorithm selection. 246 4.2. Use of SHA-1 in Transformed Identifiers 248 This profile mandates the availability of a identifier synonym 249 mechanism based on the SHA-1 cryptographic hash algorithm. Although 250 SHA-1 is now regarded as weak enough to exclude it from use in new 251 cryptographic systems, its use in this profile is necessary for full 252 support of the SAML 2.0 standard. 254 Because the SHA-1 cryptographic hash is not being used within this 255 profile in the context of a digital signature, it is not believed to 256 introduce a security concern over and above that which already exists 257 in SAML due to the possibility of a post-hash collision between 258 entities whose "entityID" attributes hash to the same value. 260 Implementations may guard against this possibility by treating two 261 entities whose "entityID" values have the same SHA-1 equivalent as an 262 indicator of malicious intent on the part of the owner of one of the 263 entities. 265 5. IANA Considerations 267 This document has no actions for IANA. 269 6. Acknowledgements 271 The editor would like to acknowledge the following individuals for 272 their contributions to this document: 274 Scott Cantor (The Ohio State University) 276 Leif Johansson (SUNET) 278 Joe St Sauver (University of Oregon) 280 Tom Scavo (Internet2) 282 7. References 284 7.1. Normative References 286 [BCP14] Bradner, S., "Key words for use in RFCs to Indicate 287 Requirement Levels", BCP 14, RFC 2119, March 1997. 289 [I-D.young-md-query] 290 Young, I., Ed., "Metadata Query Protocol", draft-young-md- 291 query-04 (work in progress), April 2015. 293 [RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1 294 (SHA1)", RFC 3174, September 2001. 296 [SAML2Bind] 297 Cantor, S., Hirsch, F., Kemp, J., Philpott, R., and E. 298 Maler, "Bindings for the Security Assertion Markup 299 Language (SAML) V2.0", OASIS Standard saml-bindings- 300 2.0-os, March 2005. 302 [SAML2Meta] 303 Cantor, S., Moreh, J., Philpott, R., and E. Maler, 304 "Metadata for the Security Assertion Markup Language 305 (SAML) V2.0", OASIS Standard saml-metadata-2.0-os, March 306 2005. 308 [STD68] Crocker, D. and P. Overell, "Augmented BNF for Syntax 309 Specifications: ABNF", STD 68, RFC 5234, January 2008. 311 7.2. Informative References 313 [MDX.list] 314 Young, I., Ed., "MDX Mailing List", 315 . 317 [REFEDS] Research and Education Federations, "REFEDS Home Page", 318 . 320 [REFEDS.agreement] 321 Research and Education Federations, "REFEDS Participant's 322 Agreement", . 325 [RFC4844] Daigle, L. and Internet Architecture Board, "The RFC 326 Series and RFC Editor", RFC 4844, July 2007. 328 [SAML2Core] 329 Cantor, S., Kemp, J., Philpott, R., and E. Maler, 330 "Assertions and Protocol for the OASIS Security Assertion 331 Markup Language (SAML) V2.0", OASIS Standard saml-core- 332 2.0-os, March 2005, . 335 [md-query] 336 Young, I., Ed., "md-query Project", 337 . 339 Appendix A. Change Log (to be removed by RFC Editor before publication) 341 A.1. draft-young-md-query-saml-00 343 Initial version. 345 A.2. Since draft-young-md-query-saml-00 347 Added REFEDS RFC stream boilerplate. 349 A.3. Since draft-young-md-query-saml-01 351 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 353 Rework Section 2.2 to make the role of transformed identifiers 354 clearer. This changes the semantics slightly (malformed transformed 355 identifiers may now result in a 404 return rather than 400) but this 356 gives implementers more latitude in the way that they handle the 357 feature. 359 A.4. Since draft-young-md-query-saml-02 361 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 363 A.5. Since draft-young-md-query-saml-03 365 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. 367 Added an Editorial Note to help direct readers back to the 368 discussion. 370 Author's Address 372 Ian A. Young (editor) 373 Independent 375 EMail: ian@iay.org.uk