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Gondwana, Ed. 3 Internet-Draft Fastmail 4 Updates: 5228 (if approved) 3 December 2020 5 Intended status: Standards Track 6 Expires: 6 June 2021 8 Sieve Email Filtering: delivery by mailboxid 9 draft-ietf-extra-sieve-mailboxid-06 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 June 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 . . . . . . . . . . . . . . 4 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 . . . . . . . . . . . . . . . . . . . . . 6 65 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 66 12. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 67 12.1. draft-ietf-sieve-mailboxid-06 . . . . . . . . . . . . . 7 68 12.2. draft-ietf-sieve-mailboxid-05 . . . . . . . . . . . . . 7 69 12.3. draft-ietf-sieve-mailboxid-04 . . . . . . . . . . . . . 7 70 12.4. draft-ietf-sieve-mailboxid-03 . . . . . . . . . . . . . 7 71 12.5. draft-ietf-sieve-mailboxid-02 . . . . . . . . . . . . . 7 72 12.6. draft-ietf-sieve-mailboxid-01 . . . . . . . . . . . . . 8 73 12.7. draft-ietf-sieve-mailboxid-00 . . . . . . . . . . . . . 8 74 12.8. draft-gondwana-sieve-mailboxid-02 . . . . . . . . . . . 8 75 12.9. draft-gondwana-sieve-mailboxid-01 . . . . . . . . . . . 8 76 12.10. draft-gondwana-sieve-mailboxid-00 . . . . . . . . . . . 8 77 13. Normative References . . . . . . . . . . . . . . . . . . . . 8 78 14. Informative References . . . . . . . . . . . . . . . . . . . 9 79 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10 81 1. Introduction 83 [RFC5228] Sieve rules are sometimes created using graphical 84 interfaces which allow users to select the mailbox to be used as a 85 target for a rule. 87 If that mailbox is renamed, the client may also update its internal 88 representation of the rule and update the sieve script to match, 89 however this is a multi-step process and subject to partial failures. 90 Also, if the folder is renamed by a different mechanism (e.g. another 91 IMAP client) the rules will get out of sync. 93 By telling "fileinto" to reference the immutable mailboxid specified 94 by [RFC8474], using the extension specified herein, sieve rules can 95 continue to target the same mailbox even if it gets renamed. 97 2. Conventions Used In This Document 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in BCP 102 14 [RFC2119] [RFC8174] when, and only when, they appear in all 103 capitals, as shown here. 105 3. Sieve capability string 107 Scripts which use the following extensions MUST explicitly require 108 the capability "mailboxid". 110 Example: 112 require "mailboxid"; 114 4. Argument ":mailboxid" to Command "fileinto" 116 Normally, the "fileinto" command delivers the message in the mailbox 117 specified using its positional mailbox argument. However, if the 118 optional ":mailboxid" argument is also specified, the "fileinto" 119 command first checks whether a mailbox exists in the user's personal 120 namespace [RFC2342] with the specified [RFC8474] MAILBOXID. 122 If a matching mailbox is found, that mailbox is used for delivery. 124 If there is no such mailbox, the "fileinto" action proceeds as it 125 would without the ":mailboxid" argument. 127 The tagged argument ":mailboxid" to fileinto consumes one additional 128 token, a string with the objectid of the mailbox to file into. 130 Example: 132 require "fileinto"; 133 require "mailboxid"; 135 if header :contains ["from"] "coyote" { 136 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 137 "INBOX.harassment"; 138 } 140 4.1. Interaction with "mailbox" extension 142 For servers which also support the [RFC5490] mailbox extension, the 143 ":create" modifier to fileinto does not create the mailbox with the 144 specified mailboxid, however it may be specified and interacts as 145 normal with all other extensions. 147 Example: 149 require "fileinto"; 150 require "mailboxid"; 151 require "mailbox"; 153 fileinto :mailboxid "Fnosuch" 154 :create 155 "INBOX.no-such-folder"; 156 # creates INBOX.no-such-folder, but it doesn't 157 # get the "Fnosuch" mailboxid. 159 4.2. Interaction with "specialuse" extension 161 For servers which also support [RFC8579] delivery to special-use 162 mailboxes, it is an error to specify both ":mailboxid" and ":special- 163 use" in the same fileinto command. 165 Advanced filtering based on both special-use and mailboxid can be 166 built with explicit "specialuse_exists" and "mailboxidexists" tests. 168 Note to developers of sieve generation tools: it is advisable to use 169 special-use rather than mailboxid when creating rules that are based 170 on a special-use purpose (e.g. delivery directly to the Junk folder 171 based on a header that was added by a scanning agent earlier in the 172 mailflow). 174 5. Interaction with "fcc" extension 176 This document extends the definition of the ":fcc" argument defined 177 in [RFC8580] so that it can optionally be used with the ":mailboxid" 178 argument. 180 FCC =/ [":mailboxid" ] 182 If the optional ":mailboxid" argument is specified with ":fcc", it 183 instructs the Sieve interpreter to check whether a mailbox exists 184 with the specific mailboxid. If such a mailbox exists, the generated 185 message is filed into that mailbox. Otherwise, the generated message 186 is filed into the ":fcc" target mailbox. 188 Example: 190 require ["enotify", "fcc", "mailboxid"]; 191 notify :fcc "INBOX.Sent" 192 :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 193 :message "You got mail!" 194 "mailto:ken@example.com"; 196 6. Test "mailboxidexists" 198 The "mailboxidexists" test is true if all mailboxes listed in the 199 "mailboxids" argument exist in the mailstore, and each allows the 200 user in whose context the Sieve script runs to "deliver" messages 201 into it. When the mailstore is an IMAP server, "delivery" of 202 messages is possible if: 204 a) the READ-WRITE response code is present for the mailbox (see 205 Section 7.1 of [RFC3501]), if IMAP Access Control List (ACL) 206 [RFC4314] is not supported by the server, or 208 b) the user has 'p' or 'i' rights for the mailbox (see Section 5.2 of 209 [RFC4314]). 211 Note that a successful "mailboxidexists" test for a mailbox doesn't 212 necessarily mean that a "fileinto :mailboxid" action on this mailbox 213 would succeed. For example, the "fileinto" action might put user 214 over quota. The "mailboxidexists" test only verifies existence of 215 the mailbox and whether the user in whose context the Sieve script 216 runs has permissions to execute "fileinto" on it. 218 Example: 220 require "fileinto"; 221 require "mailboxid"; 223 if header :contains ["from"] "coyote" { 224 if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" { 225 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 226 "INBOX.name.will.not.be.used"; 227 } else { 228 fileinto "INBOX.harassment"; 229 } 230 } 232 Note to implementers: this test behaves identically to the 233 "mailboxexists" test defined in [RFC5490] but operates on mailboxids 234 rather than mailbox names. 236 7. Interaction with variables extension 238 There is no special interaction defined, however as an objectid is a 239 string in this document, objectid values can contain variable 240 expansions if [RFC5229] is enabled. 242 8. Formal Syntax 244 test =/ "mailboxidexists" string-list 246 tag =/ ":mailboxid" string 248 FCC =/ [":mailboxid" ] 249 ; if [@RFC8580] is supported 251 9. 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 10. 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 11. 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 12. Changes 287 (EDITOR: remove this section before publication) 289 12.1. draft-ietf-sieve-mailboxid-06 291 * GENART review - fixed example to not be semantically pointless 293 * GENART review - fixed !@ to @! in RFC reference mmark syntax 295 12.2. draft-ietf-sieve-mailboxid-05 297 * disallow :mailboxid and :special-use in the same fileinto action. 299 12.3. draft-ietf-sieve-mailboxid-04 301 * made RFC5490 and RFC8579 normative 303 * clarified wording based on AD feedback from Barry 305 12.4. draft-ietf-sieve-mailboxid-03 307 * Fixed ABNF syntax error 309 12.5. draft-ietf-sieve-mailboxid-02 311 * removed bogus : from "mailboxidexists" test title 312 * moved FCC to its own top-level section since it is not used with 313 the fileinto command. 315 12.6. draft-ietf-sieve-mailboxid-01 317 * fixed idnits - RFC5228 not mentioned in the abstract 319 * fixed other I-D references I had missed, oops 321 12.7. draft-ietf-sieve-mailboxid-00 323 * Adopted into working group per adoption call on list 325 * Updated references to old drafts which have since been published. 327 * Fixed some typoes and simplified some language. 329 * Removed stray leading colon on mailboxexists (thanks Alexey) 331 * Added :fcc to the IANA registration description (thanks Alexey) 333 * Mentioned that variables can be expanded (thanks Alexey) 335 12.8. draft-gondwana-sieve-mailboxid-02 337 * Update document date by a couple of years! Ooops, it got 338 forgotten after a WGLC which got not dissent. 340 * Create xml2rfc v3 output. 342 12.9. draft-gondwana-sieve-mailboxid-01 344 * Switch to :mailboxid tagged parameter value with fallback mailbox 345 name. 347 * Document interaction with "mailbox". 349 * Document interaction with "special-use". 351 * Document interaction with "fcc". 353 * Document security considerations around :mailboxid and :create. 355 12.10. draft-gondwana-sieve-mailboxid-00 357 * Initial version. 359 13. Normative References 361 [RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email 362 Filtering Language", RFC 5228, DOI 10.17487/RFC5228, 363 January 2008, . 365 [RFC8580] Murchison, K. and B. Gondwana, "Sieve Extension: File 366 Carbon Copy (FCC)", RFC 8580, DOI 10.17487/RFC8580, May 367 2019, . 369 [RFC8474] Gondwana, B., Ed., "IMAP Extension for Object 370 Identifiers", RFC 8474, DOI 10.17487/RFC8474, September 371 2018, . 373 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 374 Requirement Levels", BCP 14, RFC 2119, 375 DOI 10.17487/RFC2119, March 1997, 376 . 378 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 379 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 380 May 2017, . 382 [RFC2342] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342, 383 DOI 10.17487/RFC2342, May 1998, 384 . 386 14. Informative References 388 [RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language -- 389 Extensions for Checking Mailbox Status and Accessing 390 Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March 391 2009, . 393 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 394 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 395 . 397 [RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension", 398 RFC 5229, DOI 10.17487/RFC5229, January 2008, 399 . 401 [RFC8579] Bosch, S., "Sieve Email Filtering: Delivering to Special- 402 Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019, 403 . 405 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 406 RFC 4314, DOI 10.17487/RFC4314, December 2005, 407 . 409 Author's Address 411 Bron Gondwana (editor) 412 Fastmail 413 Level 2, 114 William St 414 Melbourne VIC 3000 415 Australia 417 Email: brong@fastmailteam.com 418 URI: https://www.fastmail.com