RFC 5028

RFC 5028 📞💬 A Telephone Number Mapping (ENUM) Service Registration for Instant Messaging (IM) Services

Network Working Group 🌸 Request for Comments: 5028 Author: Rohan Mahy, Plantronics 💅 Category: Standards Track ✨ Date: October 2007 🗓️ Obsoletes / Updates: the title block doesn't list anything this one obsoletes or updates 🦋

Okay bestie, this RFC is a Standards Track doc by Rohan Mahy from Plantronics, dated October 2007. It's a pretty little registration that lets phone numbers point to instant messaging addresses. Let's get into it 🎀

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Status of This Memo 📋

This document is an Internet standards track protocol for the Internet community, and it's asking for discussion and suggestions for improvements 🫶 For where this protocol stands in the standardization process, check the current edition of "Internet Official Protocol Standards" (STD 1). Distribution of this memo is unlimited 🌈

Abstract ✨

This doc registers a Telephone Number Mapping (ENUM) service for Instant Messaging (IM) 💜 It's specifically about provisioning 'im:' URIs (Uniform Resource Identifiers) in ENUM. Main character energy 👑

1. Introduction 🧚

Okay so ENUM (E.164 Number Mapping, RFC 3761 [1]) is a system that uses DNS (Domain Name Service, RFC 1034 [2]) to turn phone numbers, like +12025550100, into URIs (Uniform Resource Identifiers, RFC 3986 [3]), like im:user@example.com. Its whole job is connecting systems that run on phone numbers with systems that use URIs to identify resources. It's giving bridge 🌉

Instant Messaging (IM) is a service defined in RFC 2778 [6] that lets users send and receive messages that are usually short and often text-based, in near real-time 💬 The IETF defined a generic URI for identifying an IM service for a particular resource: the 'im:' URI scheme, which is defined in RFC 3861 [4]. RFC 3861 [4] also has rules for discovering services that run specific protocols, like SIP (the Session Initiation Protocol, RFC 3261 [8]) and XMPP (the eXtensible Messaging and Presence Protocol, RFC 3921 [9]), from a specific 'im:' URI 🔥

RFC 3953 [10] already defines an enumservice for presence services, which returns 'pres:' URIs (also defined in RFC 3861 [4]) 🦋 This doc registers an enumservice for advertising IM info tied to an E.164 number. Iconic 😭

2. ENUM Service Registration - im 💌

As RFC 3761 [1] defines, here's the template with everything needed to register the enumservice in this doc 📝

Enumservice Name:
   "im"
Enumservice Type:
   "im"
Enumservice Subtypes:
   N/A
URI scheme(s):
   "im:"
Functional Specification:
   This Enumservice indicates that the resource identified is an
   'im:' URI.  The 'im:' URI scheme does not identify any particular
   protocol that will be used to handle instant messaging receipt or
   delivery, rather the mechanism in RFC 3861 [4] is used to discover
   whether an IM protocol supported by the party querying ENUM is
   also supported by the target resource.
Security considerations:
   See section 3.
Intended usage:
   COMMON
Author:
   Rohan Mahy (rohan@ekabal.com)

3. Security Considerations 🔒💀

Okay, this section is serious, so pay attention 🫶 DNS doesn't make policy decisions about which records it hands to a DNS resolver. All DNS records have to be assumed available to all inquirers at all times. So the info in an ENUM record set should be treated as open to the public, and that's a real privacy consideration 👀

Revealing an 'im:' URI by itself probably won't cause many privacy issues. But depending on how the URI is built, it might reveal the full name or employer of the target. Anonymous URIs help reduce that risk 🎀

ENUM runs on DNS, and in its current form DNS is an insecure protocol. There's no mechanism for making sure the answer to a query is authentic 😱 RFC 3761 covers threats specific to ENUM's dependence on DNS, and RFC 3833 [11] has a thorough threat analysis of DNS itself. A lot of these problems get prevented when the resolver verifies the authenticity of its ENUM query answers with DNSSEC [5] in zones where it's available 🛡️

The bigger concerns are attacks on the underlying Instant Messaging system, like message forgery and tampering 🚨 That's why IM protocols have a bunch of security requirements (detailed in RFC 2779 [7]) calling for authentication, integrity and confidentiality properties, plus similar measures to stop those attacks. Any instant messaging protocol used with the 'im:' URI scheme is required to meet these requirements 💅

Unlike a traditional telephone number, the resource behind an 'im:' URI may require callers to provide cryptographic credentials for authentication and authorization before any instant messages get exchanged 🔐 Paired with IM protocols, ENUM can actually protect you from unwanted callers way better than the existing PSTN, even though ENUM records are publicly available 🧚✨

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4. IANA Considerations 📚

This document requests registration of the "im" Enumservice, following the definitions in this document and RFC 3761 [1] 🌷

5. References 📖

5.1. 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 - concepts and facilities", STD
      13, RFC 1034, November 1987.

[3]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
      Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
      January 2005.

[4]   Peterson, J., "Address Resolution for Instant Messaging and
      Presence", RFC 3861, August 2004.

[5]   Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,
      "Protocol Modifications for the DNS Security Extensions", RFC
      4035, March 2005.

5.2. Informative References

[6]   Day, M., Rosenberg, J., and H. Sugano, "A Model for Presence
      and Instant Messaging", RFC 2778, February 2000.

[7]   Day, M., Aggarwal, S., Mohr, G., and J. Vincent, "Instant
      Messaging / Presence Protocol Requirements", RFC 2779, February
      2000.

[8]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
      Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP:
      Session Initiation Protocol", RFC 3261, June 2002.

[9]   Saint-Andre, P., Ed., "Extensible Messaging and Presence
      Protocol (XMPP): Instant Messaging and Presence", RFC 3921,
      October 2004.

[10]  Peterson, J., "Telephone Number Mapping (ENUM) Service
      Registration for Presence Services", RFC 3953, January 2005.

[11]  Atkins, D. and R. Austein, "Threat Analysis of the Domain Name
      System (DNS)", RFC 3833, August 2004.

Author's Address 🌸

Rohan Mahy, Plantronics EMail: rohan@ekabal.com 💌

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