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Network Working Group                                       A. MayrhoferRequest for Comments: 4969                                       enum.atCategory: Standards Track                                    August 2007IANA Registration for vCard EnumserviceStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The IETF Trust (2007).Abstract   This memo registers the Enumservice "vCard" using the URI schemes   "http" and "https".  This Enumservice is to be used to refer from an   ENUM domain name to a vCard instance describing the user of the   respective E.164 number.   Information gathered from those vCards could be used before, during,   or after inbound or outbound communication takes place.  For example,   a callee might be presented with the name and association of the   caller before picking up the call.Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .22.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .23.  Enumservice Registration - vCard  . . . . . . . . . . . . . . .24.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . . .35.  Security and Privacy Considerations . . . . . . . . . . . . . .35.1.  The ENUM Record Itself  . . . . . . . . . . . . . . . . . .35.2.  The Resource Identified . . . . . . . . . . . . . . . . . .46.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .57.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . .58.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .58.1.  Normative References  . . . . . . . . . . . . . . . . . . .58.2.  Informative References  . . . . . . . . . . . . . . . . . .5Mayrhofer                   Standards Track                     [Page 1]

RFC 4969                   vCard Enumservice                 August 20071.  Introduction   E.164 Number Mapping (ENUM) [1] uses the Domain Name System (DNS) [2]   to refer from E.164 numbers [3] to Uniform Resource Identifiers   (URIs) [6].  The registration process for Enumservices is described   inSection 3 of RFC 3761.   "vCard" [4] is a transport-independent data format for the exchange   of information about an individual.  For the purpose of this   document, the term "vCard" refers to a specific instance of this data   format -- an "electronic business card". vCards are exchanged via   several protocols; most commonly, they are distributed as electronic   mail attachments or published on web servers.  Most popular personal   information manager applications are capable of reading and writing   vCards.   The Enumservice specified in this document deals with the relation   between an E.164 number and vCards.  An ENUM record using this   Enumservice identifies a resource from where a vCard corresponding to   the respective E.164 number could be fetched.   Clients could use those resources to, e.g., automatically update   local address books (a Voice over IP phone could try to fetch vCards   for all outbound and inbound calls taking place on that phone and   display them together with the call journal).  In a more integrated   scenario, information gathered from those vCards could even be   automatically incorporated into the personal information manager   application of the respective user.2.  Terminology   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 inRFC 2119 [5].3.  Enumservice Registration - vCard   Enumservice Name: "vCard"   Enumservice Type: "vcard"   Enumservice Subtype: n/a   URI Schemes: "http", "https"Mayrhofer                   Standards Track                     [Page 2]

RFC 4969                   vCard Enumservice                 August 2007   Functional Specification:      This Enumservice indicates that the resource identified is a plain      vCard, according toRFC 2426, which may be accessed using HTTP/      HTTPS [7].      Clients fetching the vCard from the resource indicated should      expect access to be restricted.  Additionally, the comprehension      of the data provided may vary depending on the client's identity.   Security Considerations: seeSection 5   Intended Usage: COMMON   Author: Alexander Mayrhofer <alexander.mayrhofer@enum.at>4.  Example   An example ENUM entry referencing to a vCard could look like:      $ORIGIN 6.4.9.0.6.4.9.7.0.2.4.4.e164.arpa.      @  IN NAPTR 100 10 "u" "E2U+vcard" \      "!^.*$!http://example.net/vcard.vcf!" .5.  Security and Privacy Considerations   As with any Enumservice, the security considerations of ENUM itself   (Section 6 of RFC 3761) apply.5.1.  The ENUM Record Itself   Since ENUM uses DNS -- a publicly available database -- any   information contained in records provisioned in ENUM domains must be   considered public as well.  Even after revoking the DNS entry and   removing the referred resource, copies of the information could still   be available.   Information published in ENUM records could reveal associations   between E.164 numbers and their owners - especially if URIs contain   personal identifiers or domain names for which ownership information   can be obtained easily.  For example, the following URI makes it easy   to guess the owner of an E.164 number, as well as his location and   association, by just examining the result from the ENUM lookup:http://sandiego.company.example.com/joe-william-user.vcfMayrhofer                   Standards Track                     [Page 3]

RFC 4969                   vCard Enumservice                 August 2007   However, it is important to note that the ENUM record itself does not   need to contain any personal information.  It just points to a   location where access to personal information could be granted.  For   example, the following URI only reveals the service provider hosting   the vCard (who probably even provides anonymous hosting):      http://anonhoster.example.org/file_adfa001.vcf   ENUM records pointing to third-party resources can easily be   provisioned on purpose by the ENUM domain owner - so any assumption   about the association between a number and an entity could therefore   be completely bogus unless some kind of identity verification is in   place.  This verification is out of scope for this memo.5.2.  The Resource Identified   In most cases, vCards provide information about individuals.  Linking   telephone numbers to such Personally Identifiable Information (PII)   is a very sensitive topic, because it provides a "reverse lookup"   from the number to its owner.  Publication of such PII is covered by   data-protection law in many legislations.  In most cases, the   explicit consent of the affected individual is required.   Users MUST therefore carefully consider information they provide in   the resource identified by the ENUM record as well as in the record   itself.  Considerations SHOULD include serving information only to   entities of the user's choice and/or limiting the comprehension of   the information provided based on the identity of the requestor.   The use of HTTP in this Enumservice allows using built-in   authentication, authorization, and session control mechanisms to be   used to maintain access controls on vCards.  Most notable, Digest   Authentication [8] could be used to challenge requestors, and even   synthesize vCards based on the client's identity (or refuse access   entirely).  This could especially be useful in private ENUM   deployments (like within enterprises), where clients would more   likely have a valid credential to access the indicated resource.   Even public deployments could synthesize vCards based on the identity   of the client.  Social network sites, for example, could (based on   HTTP session data like cookies [9]) provide more comprehensive vCards   to their members than to anonymous clients.   If access restrictions on the vCard resource are deployed, standard   HTTP authentication, authorization, and state management mechanisms   (as described in RFCs 2617 and 2695) MUST be used to enforce those   restrictions.  HTTPS SHOULD be preferred if the deployed mechanisms   are prone to eavesdropping and replay attacks.Mayrhofer                   Standards Track                     [Page 4]

RFC 4969                   vCard Enumservice                 August 2007   ENUM deployments using this Enumservice together with DNS Security   Extensions (DNSSEC) [10] should consider using Minimally Covering   NSEC Records [11] to prevent zone walking, as the PII data contained   in vCards constitutes a rich target for such attempts.6.  IANA Considerations   This memo requests registration of the "vCard" Enumservice according   to the template inSection 3 of this document and the definitions inRFC 3761 [1].7.  Acknowledgements   The author wishes to thank David Lindner for his contributions during   the early stages of this document.  In addition, Klaus Nieminen, Jon   Peterson, Ondrej Sury, and Ted Hardie provided very helpful   suggestions.8.  References8.1.  Normative References   [1]   Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource         Identifiers (URI) Dynamic Delegation Discovery System (DDDS)         Application (ENUM)",RFC 3761, April 2004.   [2]   Mockapetris, P., "Domain names - implementation and         specification", STD 13,RFC 1035, November 1987.   [3]   ITU-T, "The international public telecommunication numbering         plan", Recommendation E.164 (02/05), Feb 2005.   [4]   Dawson, F. and T. Howes, "vCard MIME Directory Profile",RFC 2426, September 1998.   [5]   Bradner, S., "Key words for use in RFCs to Indicate Requirement         Levels",BCP 14,RFC 2119, March 1997.8.2.  Informative References   [6]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform         Resource Identifier (URI): Generic Syntax", STD 66,RFC 3986,         January 2005.   [7]   Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L.,         Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol --         HTTP/1.1",RFC 2616, June 1999.Mayrhofer                   Standards Track                     [Page 5]

RFC 4969                   vCard Enumservice                 August 2007   [8]   Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,         Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication:         Basic and Digest Access Authentication",RFC 2617, June 1999.   [9]   Kristol, D. and L. Montulli, "HTTP State Management Mechanism",RFC 2965, October 2000.   [10]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,         "DNS Security Introduction and Requirements",RFC 4033,         March 2005.   [11]  Weiler, S. and J. Ihren, "Minimally Covering NSEC Records and         DNSSEC On-line Signing",RFC 4470, April 2006.Author's Address   Alexander Mayrhofer   enum.at GmbH   Karlsplatz 1/2/9   Wien  A-1010   Austria   Phone: +43 1 5056416 34   EMail: alexander.mayrhofer@enum.at   URI:http://www.enum.at/Mayrhofer                   Standards Track                     [Page 6]

RFC 4969                   vCard Enumservice                 August 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Mayrhofer                   Standards Track                     [Page 7]