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Gondwana, Ed. 3 Internet-Draft Fastmail 4 Updates: 5228 (if approved) 2 November 2020 5 Intended status: Standards Track 6 Expires: 6 May 2021 8 Sieve Email Filtering: delivery by mailboxid 9 draft-ietf-extra-sieve-mailboxid-04 11 Abstract 13 The OBJECTID capability of the IMAP protocol (RFC8474) allows clients 14 to identify mailboxes by a unique identifier which survives rename. 16 This document extends the Sieve mail filtering language (RFC5228) to 17 allow using that same unique identifier as a target for fileinto 18 rules, and for testing the existance of mailboxes. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on 6 May 2021. 37 Copyright Notice 39 Copyright (c) 2020 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 44 license-info) in effect on the date of publication of this document. 45 Please review these documents carefully, as they describe your rights 46 and restrictions with respect to this document. Code Components 47 extracted from this document must include Simplified BSD License text 48 as described in Section 4.e of the Trust Legal Provisions and are 49 provided without warranty as described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Conventions Used In This Document . . . . . . . . . . . . . . 3 55 3. Sieve capability string . . . . . . . . . . . . . . . . . . . 3 56 4. Argument ":mailboxid" to Command "fileinto" . . . . . . . . . 3 57 4.1. Interaction with "mailbox" extension . . . . . . . . . . 4 58 4.2. Interaction with "specialuse" extension . . . . . . . . . 4 59 5. Interaction with "fcc" extension . . . . . . . . . . . . . . 5 60 6. Test "mailboxidexists" . . . . . . . . . . . . . . . . . . . 5 61 7. Interaction with variables extension . . . . . . . . . . . . 6 62 8. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 6 63 9. Security considerations . . . . . . . . . . . . . . . . . . . 6 64 10. IANA considerations . . . . . . . . . . . . . . . . . . . . . 7 65 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 66 12. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 67 12.1. draft-ietf-sieve-mailboxid-04 . . . . . . . . . . . . . 7 68 12.2. draft-ietf-sieve-mailboxid-03 . . . . . . . . . . . . . 7 69 12.3. draft-ietf-sieve-mailboxid-02 . . . . . . . . . . . . . 7 70 12.4. draft-ietf-sieve-mailboxid-01 . . . . . . . . . . . . . 8 71 12.5. draft-ietf-sieve-mailboxid-00 . . . . . . . . . . . . . 8 72 12.6. draft-gondwana-sieve-mailboxid-02 . . . . . . . . . . . 8 73 12.7. draft-gondwana-sieve-mailboxid-01 . . . . . . . . . . . 8 74 12.8. draft-gondwana-sieve-mailboxid-00 . . . . . . . . . . . 8 75 13. Normative References . . . . . . . . . . . . . . . . . . . . 8 76 14. Informative References . . . . . . . . . . . . . . . . . . . 9 77 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 79 1. Introduction 81 [RFC5228] Sieve rules are sometimes created using graphical 82 interfaces which allow users to select the mailbox to be used as a 83 target for a rule. 85 If that mailbox is renamed, the client may also update its internal 86 representation of the rule and update the sieve script to match, 87 however this is a multi-step process and subject to partial failures. 88 Also, if the folder is renamed by a different mechanism (e.g. another 89 IMAP client) the rules will get out of sync. 91 By telling "fileinto" to reference the immutable mailboxid specified 92 by [RFC8474], using the extension specified herein, sieve rules can 93 continue to target the same mailbox even if it gets renamed. 95 2. Conventions Used In This Document 97 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 98 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 99 "OPTIONAL" in this document are to be interpreted as described in BCP 100 14 [RFC2119] [RFC8174] when, and only when, they appear in all 101 capitals, as shown here. 103 3. Sieve capability string 105 Scripts which use the following extensions MUST explicitly require 106 the capability "mailboxid". 108 Example: 110 require "mailboxid"; 112 4. Argument ":mailboxid" to Command "fileinto" 114 Normally, the "fileinto" command delivers the message in the mailbox 115 specified using its positional mailbox argument. However, if the 116 optional ":mailboxid" argument is also specified, the "fileinto" 117 command first checks whether a mailbox exists in the user's personal 118 namespace [RFC2342] with the specified [RFC8474] MAILBOXID. 120 If a matching mailbox is found, that mailbox is used for delivery. 122 If there is no such mailbox, the "fileinto" action proceeds as it 123 would without the ":mailboxid" argument. 125 The tagged argument ":mailboxid" to fileinto consumes one additional 126 token, a string with the objectid of the mailbox to file into. 128 Example: 130 require "fileinto"; 131 require "mailboxid"; 133 if header :contains ["from"] "coyote" { 134 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 135 "INBOX.harassment"; 136 } 138 4.1. Interaction with "mailbox" extension 140 For servers which also support the [!@RFC5490] mailbox extension, the 141 ":create" modifier to fileinto does not create the mailbox with the 142 specified mailboxid, however it may be specified and interacts as 143 normal with all other extensions. 145 Example: 147 require "fileinto"; 148 require "mailboxid"; 149 require "mailbox"; 151 fileinto :mailboxid "Fnosuch" 152 :create 153 "INBOX.no-such-folder"; 154 # creates INBOX.no-such-folder, but it doesn't 155 # get the "Fnosuch" mailboxid. 157 4.2. Interaction with "specialuse" extension 159 For servers which also support [!@RFC8579] delivery to special-use 160 mailboxes, if a fileinto command has both ":mailboxid" and ":special- 161 use" specified, then the mailboxid is resolved first. 163 If a mailbox with the specified mailboxid does not exist, then the 164 process specified in [!@RFC8579] is followed - which includes 165 processing of [!@RFC5490] ":create" tags to add the special-use to 166 the created mailbox. 168 Example: 170 require "fileinto"; 171 require "mailboxid"; 172 require "special-use"; 173 if header :contains ["from"] "coyote" { 174 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 175 :specialuse "\\Junk" 176 "INBOX.harassment"; 177 } 179 This means that if a mailbox with ID F6352ae03-b7f5-463c-896f- 180 d8b48ee3 exists, the email will be filed there, regardless of what 181 name or special-use it has, and regardless of whether a different 182 mailbox exists with either the special-use or name specified. 184 Example: 186 require "fileinto"; 187 require "mailboxid"; 188 require "mailbox"; 189 require "special-use"; 191 fileinto :mailboxid "F1234567" 192 :specialuse "\\Archive" 193 :create 194 "INBOX.Archive"; 195 # creates INBOX.Archive with use \Archive but 196 # with a different mailboxid. 198 5. Interaction with "fcc" extension 200 This document extends the definition of the ":fcc" argument defined 201 in [RFC8580] so that it can optionally be used with the ":mailboxid" 202 argument. 204 FCC =/ [":mailboxid" ] 206 If the optional ":mailboxid" argument is specified with ":fcc", it 207 instructs the Sieve interpreter to check whether a mailbox exists 208 with the specific mailboxid. If such a mailbox exists, the generated 209 message is filed into that mailbox. Otherwise, the generated message 210 is filed into the ":fcc" target mailbox. 212 Example: 214 require ["enotify", "fcc", "mailboxid"]; 215 notify :fcc "INBOX.Sent" 216 :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 217 :message "You got mail!" 218 "mailto:ken@example.com"; 220 6. Test "mailboxidexists" 222 The "mailboxidexists" test is true if all mailboxes listed in the 223 "mailboxids" argument exist in the mailstore, and each allows the 224 user in whose context the Sieve script runs to "deliver" messages 225 into it. When the mailstore is an IMAP server, "delivery" of 226 messages is possible if: 228 a) the READ-WRITE response code is present for the mailbox (see 229 Section 7.1 of [RFC3501]), if IMAP Access Control List (ACL) 230 [RFC4314] is not supported by the server, or 232 b) the user has 'p' or 'i' rights for the mailbox (see Section 5.2 of 233 [RFC4314]). 235 Note that a successful "mailboxidexists" test for a mailbox doesn't 236 necessarily mean that a "fileinto :mailboxid" action on this mailbox 237 would succeed. For example, the "fileinto" action might put user 238 over quota. The "mailboxidexists" test only verifies existence of 239 the mailbox and whether the user in whose context the Sieve script 240 runs has permissions to execute "fileinto" on it. 242 Example: 244 require "fileinto"; 245 require "mailboxid"; 247 if header :contains ["from"] "coyote" { 248 if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" { 249 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 250 "INBOX.harassment"; 251 } else { 252 fileinto "INBOX.harassment"; 253 } 254 } 256 Note to implementers: this test behaves identically to the 257 "mailboxexists" test defined in [RFC5490] but operates on mailboxids 258 rather than mailbox names. 260 7. Interaction with variables extension 262 There is no special interaction defined, however as an objectid is a 263 string in this document, objectid values can contain variable 264 expansions if [RFC5229] is enabled. 266 8. Formal Syntax 268 test =/ "mailboxidexists" string-list 270 tag =/ ":mailboxid" string 272 FCC =/ [":mailboxid" ] 273 ; if [@RFC8580] is supported 275 9. Security considerations 277 Because mailboxid is always generated by the server, implementations 278 MUST NOT allow sieve to make an endrun around this protection by 279 creating mailboxes with the specified ID by using ":create" and 280 ":mailboxid" in a fileinto rule for a non-existant mailbox. 282 Implementers are referred to the security considerations sections of 283 [RFC5228] and [RFC8474]. 285 10. IANA considerations 287 IANA are requested to add a capability to the sieve-extensions 288 registry: 290 To: iana@iana.org 291 Subject: Registration of new Sieve extension 293 Capability name: mailboxid 294 Description: adds a test for checking mailbox existence by objectid, 295 and new optional arguments to fileinto and :fcc which 296 allow selecting the destination mailbox by objectid. 297 RFC number: this RFC 298 Contact address: The EXTRA discussion list 300 11. Acknowledgements 302 This document borrows heavily from [RFC5490] for the matching 303 mailboxexists test, and from [RFC8579] for an example of modifying 304 the fileinto command. 306 Thanks to Ned Freed and Ken Murchison and Alexey Melnikov for 307 feedback on the EXTRA mailing list. 309 12. Changes 311 (EDITOR: remove this section before publication) 313 12.1. draft-ietf-sieve-mailboxid-04 315 * made RFC5490 and RFC8579 normative 317 * clarified wording based on AD feedback from Barry 319 12.2. draft-ietf-sieve-mailboxid-03 321 * Fixed ABNF syntax error 323 12.3. draft-ietf-sieve-mailboxid-02 325 * removed bogus : from "mailboxidexists" test title 327 * moved FCC to its own top-level section since it is not used with 328 the fileinto command. 330 12.4. draft-ietf-sieve-mailboxid-01 332 * fixed idnits - RFC5228 not mentioned in the abstract 334 * fixed other I-D references I had missed, oops 336 12.5. draft-ietf-sieve-mailboxid-00 338 * Adopted into working group per adoption call on list 340 * Updated references to old drafts which have since been published. 342 * Fixed some typoes and simplified some language. 344 * Removed stray leading colon on mailboxexists (thanks Alexey) 346 * Added :fcc to the IANA registration description (thanks Alexey) 348 * Mentioned that variables can be expanded (thanks Alexey) 350 12.6. draft-gondwana-sieve-mailboxid-02 352 * Update document date by a couple of years! Ooops, it got 353 forgotten after a WGLC which got not dissent. 355 * Create xml2rfc v3 output. 357 12.7. draft-gondwana-sieve-mailboxid-01 359 * Switch to :mailboxid tagged parameter value with fallback mailbox 360 name. 362 * Document interaction with "mailbox". 364 * Document interaction with "special-use". 366 * Document interaction with "fcc". 368 * Document security considerations around :mailboxid and :create. 370 12.8. draft-gondwana-sieve-mailboxid-00 372 * Initial version. 374 13. Normative References 376 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 377 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 378 May 2017, . 380 [RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email 381 Filtering Language", RFC 5228, DOI 10.17487/RFC5228, 382 January 2008, . 384 [RFC8474] Gondwana, B., Ed., "IMAP Extension for Object 385 Identifiers", RFC 8474, DOI 10.17487/RFC8474, September 386 2018, . 388 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 389 Requirement Levels", BCP 14, RFC 2119, 390 DOI 10.17487/RFC2119, March 1997, 391 . 393 [RFC2342] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342, 394 DOI 10.17487/RFC2342, May 1998, 395 . 397 [RFC8580] Murchison, K. and B. Gondwana, "Sieve Extension: File 398 Carbon Copy (FCC)", RFC 8580, DOI 10.17487/RFC8580, May 399 2019, . 401 14. Informative References 403 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 404 RFC 4314, DOI 10.17487/RFC4314, December 2005, 405 . 407 [RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language -- 408 Extensions for Checking Mailbox Status and Accessing 409 Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March 410 2009, . 412 [RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension", 413 RFC 5229, DOI 10.17487/RFC5229, January 2008, 414 . 416 [RFC8579] Bosch, S., "Sieve Email Filtering: Delivering to Special- 417 Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019, 418 . 420 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 421 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 422 . 424 Author's Address 426 Bron Gondwana (editor) 427 Fastmail 428 Level 2, 114 William St 429 Melbourne VIC 3000 430 Australia 432 Email: brong@fastmailteam.com 433 URI: https://www.fastmail.com