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Gondwana, Ed. 3 Internet-Draft Fastmail 4 Updates: 5228 (if approved) 16 March 2021 5 Intended status: Standards Track 6 Expires: 17 September 2021 8 Sieve Email Filtering: delivery by mailboxid 9 draft-ietf-extra-sieve-mailboxid-08 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 17 September 2021. 37 Copyright Notice 39 Copyright (c) 2021 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. Security considerations . . . . . . . . . . . . . . . . . . . 6 63 9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 6 64 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 65 11. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 66 11.1. draft-ietf-sieve-mailboxid-08 . . . . . . . . . . . . . 7 67 11.2. draft-ietf-sieve-mailboxid-07 . . . . . . . . . . . . . 7 68 11.3. draft-ietf-sieve-mailboxid-06 . . . . . . . . . . . . . 7 69 11.4. draft-ietf-sieve-mailboxid-05 . . . . . . . . . . . . . 7 70 11.5. draft-ietf-sieve-mailboxid-04 . . . . . . . . . . . . . 7 71 11.6. draft-ietf-sieve-mailboxid-03 . . . . . . . . . . . . . 8 72 11.7. draft-ietf-sieve-mailboxid-02 . . . . . . . . . . . . . 8 73 11.8. draft-ietf-sieve-mailboxid-01 . . . . . . . . . . . . . 8 74 11.9. draft-ietf-sieve-mailboxid-00 . . . . . . . . . . . . . 8 75 11.10. draft-gondwana-sieve-mailboxid-02 . . . . . . . . . . . 8 76 11.11. draft-gondwana-sieve-mailboxid-01 . . . . . . . . . . . 8 77 11.12. draft-gondwana-sieve-mailboxid-00 . . . . . . . . . . . 9 78 12. Normative References . . . . . . . . . . . . . . . . . . . . 9 79 13. Informative References . . . . . . . . . . . . . . . . . . . 9 80 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 82 1. Introduction 84 [RFC5228] Sieve rules are sometimes created using graphical 85 interfaces which allow users to select the mailbox to be used as a 86 target for a rule. 88 If that mailbox is renamed, the client may also update its internal 89 representation of the rule and update the sieve script to match, 90 however this is a multi-step process and subject to partial failures. 91 Also, if the folder is renamed by a different mechanism (e.g. another 92 IMAP client) the rules will get out of sync. 94 By telling "fileinto" to reference the immutable mailboxid specified 95 by [RFC8474], using the extension specified herein, sieve rules can 96 continue to target the same mailbox even if it gets renamed. 98 2. Conventions Used In This Document 100 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 101 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 102 "OPTIONAL" in this document are to be interpreted as described in BCP 103 14 [RFC2119] [RFC8174] when, and only when, they appear in all 104 capitals, as shown here. 106 3. Sieve capability string 108 Scripts which use the following extensions MUST explicitly require 109 the capability "mailboxid". 111 Example: 113 require "mailboxid"; 115 4. Argument ":mailboxid" to Command "fileinto" 117 Normally, the "fileinto" command delivers the message in the mailbox 118 specified using its positional mailbox argument. However, if the 119 optional ":mailboxid" argument is also specified, the "fileinto" 120 command first checks whether a mailbox exists in the user's personal 121 namespace [RFC2342] with the specified [RFC8474] MAILBOXID. 123 If a matching mailbox is found, that mailbox is used for delivery. 125 If there is no such mailbox, the "fileinto" action proceeds as it 126 would without the ":mailboxid" argument. 128 The tagged argument ":mailboxid" to fileinto consumes one additional 129 token, a string with the objectid of the mailbox to file into. 131 Example: 133 require "fileinto"; 134 require "mailboxid"; 136 if header :contains ["from"] "coyote" { 137 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 138 "INBOX.harassment"; 139 } 141 4.1. Interaction with "mailbox" extension 143 For servers which also support the [RFC5490] mailbox extension, if 144 both the ":create" and ":mailboxid" arguments are provided to a 145 "fileinto" command and no matching mailbox is found, then a new 146 mailbox will be created. 148 This new mailbox will have the name specified by the positional 149 mailbox argument ([RFC5228] section 4.1), however it will get a 150 different mailboxid (chosen by the server) rather than the one 151 specified by the ":mailboxid" argument to fileinto. 153 Example: 155 require "fileinto"; 156 require "mailboxid"; 157 require "mailbox"; 159 fileinto :mailboxid "Fnosuch" 160 :create 161 "INBOX.no-such-folder"; 162 # creates INBOX.no-such-folder, but it doesn't 163 # get the "Fnosuch" mailboxid. 165 4.2. Interaction with "specialuse" extension 167 For servers which also support [RFC8579] delivery to special-use 168 mailboxes, it is an error to specify both ":mailboxid" and 169 ":specialuse" in the same fileinto command. 171 Advanced filtering based on both special-use and mailboxid can be 172 built with explicit "specialuse_exists" and "mailboxidexists" tests. 174 Note to developers of sieve generation tools: it is advisable to use 175 special-use rather than mailboxid when creating rules that are based 176 on a special-use purpose (e.g. delivery directly to the Junk folder 177 based on a header that was added by a scanning agent earlier in the 178 mailflow). 180 5. Interaction with "fcc" extension 182 This document extends the definition of the ":fcc" argument defined 183 in [RFC8580] so that it can optionally be used with the ":mailboxid" 184 argument. 186 FCC-OPTS =/ [":mailboxid" ] 188 If the optional ":mailboxid" argument is specified with ":fcc", it 189 instructs the Sieve interpreter to check whether a mailbox exists 190 with the specific mailboxid. If such a mailbox exists, the generated 191 message is filed into that mailbox. Otherwise, the generated message 192 is filed into the ":fcc" target mailbox. 194 As with fileinto, it is an error to specify both ":mailboxid" and 195 ":specialuse" for the same fcc rule. 197 Example: 199 require ["enotify", "fcc", "mailboxid"]; 200 notify :fcc "INBOX.Sent" 201 :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 202 :message "You got mail!" 203 "mailto:ken@example.com"; 205 6. Test "mailboxidexists" 207 The "mailboxidexists" test is true if all mailboxes listed in the 208 "mailboxids" argument exist in the mailstore, and each allows the 209 user in whose context the Sieve script runs to "deliver" messages 210 into it. When the mailstore is an IMAP server, "delivery" of 211 messages is possible if: 213 a) the READ-WRITE response code is present for the mailbox (see 214 Section 7.1 of [RFC3501]), if IMAP Access Control List (ACL) 215 [RFC4314] is not supported by the server, or 217 b) the user has 'p' or 'i' rights for the mailbox (see Section 5.2 of 218 [RFC4314]). 220 Note that a successful "mailboxidexists" test for a mailbox doesn't 221 necessarily mean that a "fileinto :mailboxid" action on this mailbox 222 would succeed. For example, the "fileinto" action might put user 223 over quota. The "mailboxidexists" test only verifies existence of 224 the mailbox and whether the user in whose context the Sieve script 225 runs has permissions to execute "fileinto" on it. 227 Example: 229 require "fileinto"; 230 require "mailboxid"; 232 if header :contains ["from"] "coyote" { 233 if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" { 234 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 235 "INBOX.name.will.not.be.used"; 236 } else { 237 fileinto "INBOX.harassment"; 238 } 239 } 241 Note to implementers: this test behaves identically to the 242 "mailboxexists" test defined in [RFC5490] but operates on mailboxids 243 rather than mailbox names. 245 7. Interaction with variables extension 247 There is no special interaction defined, however as an objectid is a 248 string in this document, objectid values can contain variable 249 expansions if [RFC5229] is enabled. 251 8. Security considerations 253 Because mailboxid is always generated by the server, implementations 254 MUST NOT allow sieve to make an endrun around this protection by 255 creating mailboxes with the specified ID by using ":create" and 256 ":mailboxid" in a fileinto rule for a non-existant mailbox. 258 Implementers are referred to the security considerations sections of 259 [RFC5228] and [RFC8474]. 261 9. IANA considerations 263 IANA are requested to add a capability to the sieve-extensions 264 registry: 266 To: iana@iana.org 267 Subject: Registration of new Sieve extension 269 Capability name: mailboxid 270 Description: adds a test for checking mailbox existence by objectid, 271 and new optional arguments to fileinto and :fcc which 272 allow selecting the destination mailbox by objectid. 273 RFC number: this RFC 274 Contact address: The EXTRA discussion list 276 10. Acknowledgements 278 This document borrows heavily from [RFC5490] for the matching 279 mailboxexists test, and from [RFC8579] for an example of modifying 280 the fileinto command. 282 Thanks to Ned Freed and Ken Murchison and Alexey Melnikov for 283 feedback on the EXTRA mailing list. 285 11. Changes 287 (EDITOR: remove this section before publication) 289 11.1. draft-ietf-sieve-mailboxid-08 291 * IETF110 discussion - re-add FCC-OPTS syntax, and clarify that 292 :mailboxid is incompatible with :specialuse to parallel the 293 fileinto behaviour 295 11.2. draft-ietf-sieve-mailboxid-07 297 * Martin Duke review - remove formal section 299 * Martin Duke review - wording for section 4.1 (interaction with 300 :create) 302 * Ken Murchison review - fixed :special-use to :specialuse per 303 RFC8579 305 11.3. draft-ietf-sieve-mailboxid-06 307 * GENART review - fixed example to not be semantically pointless 309 * GENART review - fixed !@ to @! in RFC reference mmark syntax 311 11.4. draft-ietf-sieve-mailboxid-05 313 * disallow :mailboxid and :special-use in the same fileinto action. 315 11.5. draft-ietf-sieve-mailboxid-04 317 * made RFC5490 and RFC8579 normative 319 * clarified wording based on AD feedback from Barry 321 11.6. draft-ietf-sieve-mailboxid-03 323 * Fixed ABNF syntax error 325 11.7. draft-ietf-sieve-mailboxid-02 327 * removed bogus : from "mailboxidexists" test title 329 * moved FCC to its own top-level section since it is not used with 330 the fileinto command. 332 11.8. draft-ietf-sieve-mailboxid-01 334 * fixed idnits - RFC5228 not mentioned in the abstract 336 * fixed other I-D references I had missed, oops 338 11.9. draft-ietf-sieve-mailboxid-00 340 * Adopted into working group per adoption call on list 342 * Updated references to old drafts which have since been published. 344 * Fixed some typoes and simplified some language. 346 * Removed stray leading colon on mailboxexists (thanks Alexey) 348 * Added :fcc to the IANA registration description (thanks Alexey) 350 * Mentioned that variables can be expanded (thanks Alexey) 352 11.10. draft-gondwana-sieve-mailboxid-02 354 * Update document date by a couple of years! Ooops, it got 355 forgotten after a WGLC which got not dissent. 357 * Create xml2rfc v3 output. 359 11.11. draft-gondwana-sieve-mailboxid-01 361 * Switch to :mailboxid tagged parameter value with fallback mailbox 362 name. 364 * Document interaction with "mailbox". 366 * Document interaction with "special-use". 368 * Document interaction with "fcc". 370 * Document security considerations around :mailboxid and :create. 372 11.12. draft-gondwana-sieve-mailboxid-00 374 * Initial version. 376 12. Normative References 378 [RFC8474] Gondwana, B., Ed., "IMAP Extension for Object 379 Identifiers", RFC 8474, DOI 10.17487/RFC8474, September 380 2018, . 382 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 383 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 384 May 2017, . 386 [RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email 387 Filtering Language", RFC 5228, DOI 10.17487/RFC5228, 388 January 2008, . 390 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 391 Requirement Levels", BCP 14, RFC 2119, 392 DOI 10.17487/RFC2119, March 1997, 393 . 395 [RFC2342] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342, 396 DOI 10.17487/RFC2342, May 1998, 397 . 399 [RFC8580] Murchison, K. and B. Gondwana, "Sieve Extension: File 400 Carbon Copy (FCC)", RFC 8580, DOI 10.17487/RFC8580, May 401 2019, . 403 13. Informative References 405 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 406 RFC 4314, DOI 10.17487/RFC4314, December 2005, 407 . 409 [RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language -- 410 Extensions for Checking Mailbox Status and Accessing 411 Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March 412 2009, . 414 [RFC8579] Bosch, S., "Sieve Email Filtering: Delivering to Special- 415 Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019, 416 . 418 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 419 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 420 . 422 [RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension", 423 RFC 5229, DOI 10.17487/RFC5229, January 2008, 424 . 426 Author's Address 428 Bron Gondwana (editor) 429 Fastmail 430 Level 2, 114 William St 431 Melbourne VIC 3000 432 Australia 434 Email: brong@fastmailteam.com 435 URI: https://www.fastmail.com