Network Working Group I. Young, Ed. Internet-Draft Independent Intended status: Informational July 17, 2017 Expires: January 18, 2018 SAML Profile for the Metadata Query Protocol draft-young-md-query-saml-07 Abstract This document profiles the Metadata Query Protocol [I-D.young-md-query] for use with SAML metadata [SAML2Meta]. This document is a product of the Research and Education Federations (REFEDS) Working Group process. Editorial Note (To be removed by RFC Editor before publication) Discussion of this draft takes place on the MDX mailing list (mdx@lists.iay.org.uk), which is accessed from [MDX.list]. XML versions, latest edits and the issues list for this document are available from [md-query]. The changes in this draft are summarized in Appendix A.8. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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 January 18, 2018. Young Expires January 18, 2018 [Page 1] Internet-DraftSAML Profile for the Metadata Query Protocol July 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 carefully, as they describe your rights and restrictions with respect to this document. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Notation and Conventions . . . . . . . . . . . . . . . . 3 2. Request Profile . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Content Type . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 3 2.2.1. Unique Identifier . . . . . . . . . . . . . . . . . . 3 2.2.2. Transformed Identifier . . . . . . . . . . . . . . . 4 2.2.3. Additional Identifiers . . . . . . . . . . . . . . . 4 3. Response Profile . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Response Cardinality . . . . . . . . . . . . . . . . . . 5 3.1.1. No Entity Descriptors Returned . . . . . . . . . . . 5 3.1.2. One Entity Descriptor Returned . . . . . . . . . . . 5 3.1.3. More Than One Entity Descriptor Returned . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 4.1. Integrity . . . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Use of SHA-1 in Transformed Identifiers . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 7.2. Informative References . . . . . . . . . . . . . . . . . 7 Appendix A. Change Log (to be removed by RFC Editor before publication) . . . . . . . . . . . . . . . . . . . . 9 A.1. draft-young-md-query-saml-00 . . . . . . . . . . . . . . 9 A.2. Since draft-young-md-query-saml-00 . . . . . . . . . . . 9 A.3. Since draft-young-md-query-saml-01 . . . . . . . . . . . 9 A.4. Since draft-young-md-query-saml-02 . . . . . . . . . . . 9 A.5. Since draft-young-md-query-saml-03 . . . . . . . . . . . 9 A.6. Since draft-young-md-query-saml-04 . . . . . . . . . . . 9 A.7. Since draft-young-md-query-saml-05 . . . . . . . . . . . 9 A.8. Since draft-young-md-query-saml-06 . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 Young Expires January 18, 2018 [Page 2] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 1. Introduction This document profiles the Metadata Query Protocol [I-D.young-md-query] for use with SAML metadata [SAML2Meta]. The Research and Education Federations group ([REFEDS]) is the voice that articulates the mutual needs of research and education identity federations worldwide. It aims to represent the requirements of research and education in the ever-growing space of access and identity management. From time to time REFEDS will wish to publish a document in the Internet RFC series. Such documents will be published as part of the RFC Independent Submission Stream [RFC4844]; however the REFEDS working group sign-off process will have been followed for these documents, as described in the REFEDS Participant's Agreement [REFEDS.agreement]. This document is a product of the REFEDS Working Group process. 1.1. Notation and Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [BCP14]. This document makes use of the Augmented BNF metalanguage defined in [STD68]. 2. Request Profile 2.1. Content Type Requests compliant with this profile MUST include the following HTTP header to indicate that the metadata returned should be SAML metadata (see Appendix A of [SAML2Meta]): Accept: application/samlmetadata+xml 2.2. Identifiers 2.2.1. Unique Identifier Each entity known to the responder MUST be associated with the unique identifier of the entity, corresponding to the "entityID" attribute of the entity's "EntityDescriptor" element in SAML metadata. Young Expires January 18, 2018 [Page 3] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 2.2.2. Transformed Identifier SAML 2.0 [SAML2Core] includes profiles based on the transfer of an "artifact" containing the unique identifier of a SAML entity transformed by means of the SHA-1 [RFC3174] hash algorithm (see [SAML2Bind] sections 3.6 and 3.6.4). In order to support use cases in which clients may be in possession of only such a transformed representation of a SAML entity's unique identifier without any way to establish the original entity identifier, a responder compliant with this profile MUST associate each entity with an identifier matching the "sha1id" production in the following ABNF grammar, and treat such an identifier as equivalent to the corresponding untransformed identifier: SHA1 = %x73 %x68 %x61 %x31 ; lower case "sha1" DIGIT = %x30-39 HEXDIGIT = DIGIT | %x61-66 ; lower case a-f sha1id = "{" SHA1 "}" sha1hex sha1hex = 40*HEXDIGIT In the above, the "sha1hex" component encodes the 20-octet (160-bit) binary SHA-1 hash value as a sequence of 40 lower case hexadecimal digits. For example, the identifier http://example.org/service transformed by means of SHA-1 hashing would become {sha1}11d72e8cf351eb6c75c721e838f469677ab41bdb Responder implementations MAY detect malformed SHA-1 transformed identifiers (for example where the string of characters following the "}" contains characters other than hexadecimal digits, or is other than exactly 40 characters in length) and return an HTTP status code of 400 ("bad request"). Alternatively, implementations MAY process these as normal identifiers and return an HTTP status code of 404 ("not found") if appropriate. 2.2.3. Additional Identifiers Entities MAY also be associated with any number of additional responder-defined identifiers naming arbitrary groups of entities. Young Expires January 18, 2018 [Page 4] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 3. Response Profile 3.1. Response Cardinality A request may return information for any number of entities, including none. Responses compliant with this profile MUST use the appropriate representation described below depending on the number of "EntityDescriptor" elements returned. 3.1.1. No Entity Descriptors Returned A response which returns no "EntityDescriptor" elements MUST be represented by an HTTP status code of 404 ("not found"). 3.1.2. One Entity Descriptor Returned A response which returns a single "EntityDescriptor" element MUST use that element as its document element. The responder MUST NOT make use of a "EntitiesDescriptor" element in this situation (see [SAML2Meta] section 2.3). Such a response MUST include the following HTTP header to indicate that the metadata returned is SAML metadata: Content-Type: application/samlmetadata+xml 3.1.3. More Than One Entity Descriptor Returned A response which returns more than one "EntityDescriptor" element MUST consist of a document element which is an "EntitiesDescriptor" element, containing the returned "EntityDescriptor" elements as children. Responses MUST NOT contain nested "EntitiesDescriptor" elements. Such a response MUST include the following HTTP header to indicate that the metadata returned is SAML metadata: Content-Type: application/samlmetadata+xml 4. Security Considerations 4.1. Integrity As SAML metadata contains information necessary for the secure operation of interacting services it is strongly RECOMMENDED that a mechanism for integrity checking is provided to clients. Young Expires January 18, 2018 [Page 5] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 It is RECOMMENDED that the integrity checking mechanism provided by a responder is a digital signature embedded in the returned metadata document, as defined by [SAML2Meta] section 3. Such digital signatures: o SHOULD use an RSA keypair whose modulus is no less than 2048 bits in length. o SHOULD NOT use the SHA-1 cryptographic hash algorithm as a digest algorithm. o MUST NOT use the MD5 cryptographic hash algorithm as a digest algorithm. o SHOULD otherwise follow current cryptographic best practices in algorithm selection. 4.2. Use of SHA-1 in Transformed Identifiers This profile mandates the availability of a identifier synonym mechanism based on the SHA-1 cryptographic hash algorithm. Although SHA-1 is now regarded as weak enough to exclude it from use in new cryptographic systems, its use in this profile is necessary for full support of the SAML 2.0 standard. Because the SHA-1 cryptographic hash is not being used within this profile in the context of a digital signature, it is not believed to introduce a security concern over and above that which already exists in SAML due to the possibility of a post-hash collision between entities whose "entityID" attributes hash to the same value. Implementations may guard against this possibility by treating two entities whose "entityID" values have the same SHA-1 equivalent as an indicator of malicious intent on the part of the owner of one of the entities. 5. IANA Considerations This document has no actions for IANA. 6. Acknowledgements The editor would like to acknowledge the following individuals for their contributions to this document: Scott Cantor (The Ohio State University) Young Expires January 18, 2018 [Page 6] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 Leif Johansson (SUNET) Joe St Sauver (University of Oregon) Tom Scavo (Internet2) 7. References 7.1. Normative References [BCP14] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [I-D.young-md-query] Young, I., Ed., "Metadata Query Protocol", draft-young-md- query-07 (work in progress), June 2016. [RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1 (SHA1)", RFC 3174, September 2001. [SAML2Bind] Cantor, S., Hirsch, F., Kemp, J., Philpott, R., and E. Maler, "Bindings for the Security Assertion Markup Language (SAML) V2.0", OASIS Standard saml-bindings- 2.0-os, March 2005. [SAML2Meta] Cantor, S., Moreh, J., Philpott, R., and E. Maler, "Metadata for the Security Assertion Markup Language (SAML) V2.0", OASIS Standard saml-metadata-2.0-os, March 2005. [STD68] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. 7.2. Informative References [md-query] Young, I., Ed., "md-query Project", . [MDX.list] Young, I., Ed., "MDX Mailing List", . [REFEDS] Research and Education Federations, "REFEDS Home Page", . Young Expires January 18, 2018 [Page 7] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 [REFEDS.agreement] Research and Education Federations, "REFEDS Participant's Agreement", . [RFC4844] Daigle, L. and Internet Architecture Board, "The RFC Series and RFC Editor", RFC 4844, July 2007. [SAML2Core] Cantor, S., Kemp, J., Philpott, R., and E. Maler, "Assertions and Protocol for the OASIS Security Assertion Markup Language (SAML) V2.0", OASIS Standard saml-core- 2.0-os, March 2005, . Young Expires January 18, 2018 [Page 8] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 Appendix A. Change Log (to be removed by RFC Editor before publication) A.1. draft-young-md-query-saml-00 Initial version. A.2. Since draft-young-md-query-saml-00 Added REFEDS RFC stream boilerplate. A.3. Since draft-young-md-query-saml-01 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. Rework Section 2.2 to make the role of transformed identifiers clearer. This changes the semantics slightly (malformed transformed identifiers may now result in a 404 return rather than 400) but this gives implementers more latitude in the way that they handle the feature. A.4. Since draft-young-md-query-saml-02 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. A.5. Since draft-young-md-query-saml-03 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. Added an Editorial Note to help direct readers back to the discussion. A.6. Since draft-young-md-query-saml-04 Fix reference to the Metadata Query Protocol [I-D.young-md-query]. A.7. Since draft-young-md-query-saml-05 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. A.8. Since draft-young-md-query-saml-06 Bump reference to the Metadata Query Protocol [I-D.young-md-query]. Author's Address Young Expires January 18, 2018 [Page 9] Internet-DraftSAML Profile for the Metadata Query Protocol July 2017 Ian A. Young (editor) Independent EMail: ian@iay.org.uk Young Expires January 18, 2018 [Page 10]