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Leiba 3 Internet-Draft Huawei Technologies 4 Updates: 6154 (if approved) E. Iceman 5 Intended status: Standards Track Google, Inc. 6 Expires: July 18, 2013 January 14, 2013 8 IMAP LIST Special-Use Attribute: \Important 9 draft-iceman-imap-specialuse-important-00 11 Abstract 13 RFC 6154 created an IMAP Special-Use LIST extension and defined an 14 initial set of attributes. This document defines a new attribute, 15 "\Important", and establishes a new IANA registry for IMAP Special- 16 Use LIST extension folder attributes, updating RFC 6154. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on July 18, 2013. 35 Copyright Notice 37 Copyright (c) 2013 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 53 1.1. Conventions used in this document . . . . . . . . . . . . . . 3 55 2. Definition of the 'Important' Attribute . . . . . . . . . . . 3 56 2.1. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 3 57 2.2. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 59 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 61 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 62 4.1. Creation of the IMAP LIST Special-Use Attributes Registry . . 4 63 4.2. Initial entries for the registry . . . . . . . . . . . . . . 5 64 4.3. Instructions to the Designated Expert . . . . . . . . . . . . 5 66 5. Normative References . . . . . . . . . . . . . . . . . . . . 5 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 6 70 1. Introduction 72 [RFC6154] defines an extension to the Internet Message Access 73 Protocol (IMAP) LIST command [RFC3501] for special-use mailboxes. 74 The extension allows servers to provide extra information 75 (attributes) about the purpose of a mailbox and defines an initial 76 set of special-use attributes. RFC 6154 did not define a registry 77 for those attributes. 79 This document defines a new special-use attribute, "\Important", to 80 designate a mailbox that will hold messages that are considered 81 important for the user, by some externally defined criteria. This 82 document also creates a registry for IMAP special-use mailbox 83 attributes and registers both the new attribute and the initial set, 84 updating RFC 6154. 86 1.1. Conventions used in this document 88 In examples, "C:" indicates lines sent by a client that is connected 89 to a server. "S:" indicates lines sent by the server to the client. 91 2. Definition of the 'Important' Attribute 93 The "\Important" mailbox attribute is a signal that the mailbox 94 contains messages that are likely important to the user. For 95 example, the system might automatically put messages there based on 96 available signals (such as who the message is from, who else the 97 message is addressed to, evaluation of the subject or content). Or 98 it might be a way for users to train the system as to what messages 99 are important (the system can learn patterns from the messages the 100 user copies to that mailbox). 102 This is distinct from the "\Flagged" attribute in that evaluation of 103 importance here is based on heuristics, whereas "\Flagged" is 104 typically based on the setting of the IMAP flag of the same name. 106 2.1. Formal Syntax 108 The following syntax specification updates the one in [RFC6154], 109 Section 6, using Augmented Backus-Naur Form (ABNF) as described in 110 [RFC5234]. 112 use-attr =/ "\Important" 114 2.2. Example 116 In the following example, the mailbox called "Important Messages" is 117 the one designated with the "\Important" attribute. 119 C: t1 list "" "Imp*" 120 S: * LIST (\HasNoChildren \Important) "/" "Important Messages" 121 S: * LIST (\HasNoChildren) "/" "Imported Wine" 122 S: t1 OK Success 124 3. Security Considerations 126 The security considerations in [RFC6154], Section 7, apply equally to 127 this extension. In particular, "Conveying special-use information to 128 a client exposes a small bit of extra information that could be of 129 value to an attacker." Moreover, identifying a place where 130 "important" messages are kept could give an attacker a strategic 131 starting point. If the algorithm by which messages are determined to 132 be important is well known, still more information is exposed -- 133 perhaps, for example, there is an implication that the senders of 134 these messages are particularly significant to the mailbox owner, and 135 perhaps that is information that should not be made public. 137 As noted in RFC 6154, it is wise to protect the IMAP channel from 138 passive eavesdropping, and to defend against unauthorized discernment 139 of the identity of a user's "\Important" mailbox. 141 4. IANA Considerations 143 [[RFC Editor: Please replace "THIS RFC" throughout this section with 144 the identification given to this document, and remove this 145 paragraph.]] 147 4.1. Creation of the IMAP LIST Special-Use Attributes Registry 149 IANA is asked to create a new registry in the group "Internet Message 150 Access Protocol (IMAP) 4 Registries". The new registry will be 151 called "IMAP LIST Special-Use Attributes", and will have as its 152 reference RFC 6154 and THIS RFC. New registrations will be accepted 153 through the Expert Review policy [RFC5226] (and see Section 4.3). 155 The registry entries will contain three fields: 156 1. Attribute Name 157 2. Description 158 3. Reference 159 IANA will keep this list in alphabetical order by Attribute Name, 160 which is registered without the initial backslash ("\"). 162 4.2. Initial entries for the registry 164 The registry will initially consist of: 166 +-----------+-----------------------------------+-----------+ 167 | Attribute | Description | Reference | 168 +-----------+-----------------------------------+-----------+ 169 | All | All messages | [RFC6154] | 170 +-----------+-----------------------------------+-----------+ 171 | Archive | Archived messages | [RFC6154] | 172 +-----------+-----------------------------------+-----------+ 173 | Drafts | Messages that are working drafts | [RFC6154] | 174 +-----------+-----------------------------------+-----------+ 175 | Flagged | Messages with the \Flagged flag | [RFC6154] | 176 +-----------+-----------------------------------+-----------+ 177 | Important | Messages deemed important to user | THIS RFC | 178 +-----------+-----------------------------------+-----------+ 179 | Junk | Messages identified as Spam/Junk | [RFC6154] | 180 +-----------+-----------------------------------+-----------+ 181 | Sent | Sent mail | [RFC6154] | 182 +-----------+-----------------------------------+-----------+ 183 | Trash | Messages the user has discarded | [RFC6154] | 184 +-----------+-----------------------------------+-----------+ 186 4.3. Instructions to the Designated Expert 188 The expert reviewer, who will be designated by the IESG, is expected 189 to provide only a general review of the requested registration, 190 checking that the reference and description are adequate for 191 understanding the intent of the registered attribute. Efforts should 192 also be made to generalize the intent of an attribute so that 193 multiple implementations with the same requirements may reuse 194 existing attributes. Except for this check, this is intended to be 195 very close to a first come first served policy, and the expert should 196 not block serious registration requests with a reasonable reference. 197 The reference may be to any form of documentation, including a web 198 page, but consideration should be given to providing one that is 199 expected to be long-lived and stable. 201 5. Normative References 203 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 204 4rev1", RFC 3501, March 2003. 206 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 207 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 208 May 2008. 210 [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax 211 Specifications: ABNF", STD 68, RFC 5234, January 2008. 213 [RFC6154] Leiba, B. and J. Nicolson, "IMAP LIST Extension for 214 Special-Use Mailboxes", RFC 6154, March 2011. 216 Authors' Addresses 218 Barry Leiba 219 Huawei Technologies 221 Phone: +1 646 827 0648 222 Email: barryleiba@computer.org 223 URI: http://internetmessagingtechnology.org/ 225 Eric Iceman 226 Google, Inc. 228 Email: iceman@google.com