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Gondwana, Ed. 3 Internet-Draft Fastmail 4 Updates: 5228 (if approved) September 4, 2020 5 Intended status: Standards Track 6 Expires: March 8, 2021 8 Sieve Email Filtering: delivery by mailboxid 9 draft-ietf-extra-sieve-mailboxid-03 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 March 8, 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-03 . . . . . . . . . . . . . 7 68 12.2. draft-ietf-sieve-mailboxid-02 . . . . . . . . . . . . . 7 69 12.3. draft-ietf-sieve-mailboxid-01 . . . . . . . . . . . . . 7 70 12.4. draft-ietf-sieve-mailboxid-00 . . . . . . . . . . . . . 8 71 12.5. draft-gondwana-sieve-mailboxid-02 . . . . . . . . . . . 8 72 12.6. draft-gondwana-sieve-mailboxid-01 . . . . . . . . . . . 8 73 12.7. draft-gondwana-sieve-mailboxid-00 . . . . . . . . . . . 8 74 13. Normative References . . . . . . . . . . . . . . . . . . . . 8 75 14. Informative References . . . . . . . . . . . . . . . . . . . 9 76 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 78 1. Introduction 80 [RFC5228] Sieve rules are sometimes created using graphical 81 interfaces which allow users to select the mailbox to be used as a 82 target for a rule. 84 If that mailbox is renamed, the client may also update its internal 85 representation of the rule and update the sieve script to match, 86 however this is a multi-step process and subject to partial failures. 87 Also, if the folder is renamed by a different mechanism (e.g. another 88 IMAP client) the rules will get out of sync. 90 By extending "fileinto" to reference the immutable mailboxid 91 specified by [RFC8474] , sieve rules can continue to target the same 92 mailbox, even if it gets renamed. 94 2. Conventions Used In This Document 96 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 97 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 98 "OPTIONAL" in this document are to be interpreted as described in BCP 99 14 [RFC2119] [RFC8174] when, and only when, they appear in all 100 capitals, as shown here. 102 3. Sieve capability string 104 The server advertises the capability "mailboxid", and scripts which 105 use the following extensions MUST explicitly request the capability 106 "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 the 166 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 Example: 181 require "fileinto"; 182 require "mailboxid"; 183 require "mailbox"; 184 require "special-use"; 186 fileinto :mailboxid "F1234567" 187 :specialuse "\\Archive" 188 :create 189 "INBOX.Archive"; 190 # creates INBOX.Archive with use \Archive but 191 # with a different mailboxid. 193 5. Interaction with "fcc" extension 195 This document extends the definition of the ":fcc" argument defined 196 in [RFC8580] so that it can optionally be used with the ":mailboxid" 197 argument. 199 FCC =/ [":mailboxid" ] 201 If the optional ":mailboxid" argument is specified with ":fcc", it 202 instructs the Sieve interpreter to check whether a mailbox exists 203 with the specific mailboxid. If such a mailbox exists, the generated 204 message is filed into that mailbox. Otherwise, the generated message 205 is filed into the ":fcc" target mailbox. 207 Example: 209 require ["enotify", "fcc", "mailboxid"]; 210 notify :fcc "INBOX.Sent" 211 :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 212 :message "You got mail!" 213 "mailto:ken@example.com"; 215 6. Test "mailboxidexists" 217 The "mailboxidexists" test is true if all mailboxes listed in the 218 "mailboxids" argument exist in the mailstore, and each allows the 219 user in whose context the Sieve script runs to "deliver" messages 220 into it. When the mailstore is an IMAP server, "delivery" of 221 messages is possible if: 223 a) the READ-WRITE response code is present for the mailbox (see 224 Section 7.1 of [RFC3501]), if IMAP Access Control List (ACL) 225 [RFC4314] is not supported by the server, or 227 b) the user has 'p' or 'i' rights for the mailbox (see Section 5.2 of 228 [RFC4314]). 230 Note that a successful "mailboxidexists" test for a mailbox doesn't 231 necessarily mean that a "fileinto :mailboxid" action on this mailbox 232 would succeed. For example, the "fileinto" action might put user 233 over quota. The "mailboxidexists" test only verifies existence of 234 the mailbox and whether the user in whose context the Sieve script 235 runs has permissions to execute "fileinto" on it. 237 Example: 239 require "fileinto"; 240 require "mailboxid"; 242 if header :contains ["from"] "coyote" { 243 if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" { 244 fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3" 245 "INBOX.harassment"; 246 } else { 247 fileinto "INBOX.harassment"; 248 } 249 } 251 Note to implementers: this test behaves identically to the 252 "mailboxexists" test defined in [RFC5490] but operates on mailboxids 253 rather than mailbox names. 255 7. Interaction with variables extension 257 There is no special interaction defined, however as an objectid is a 258 string in this document, objectid values can contain variable 259 expansions if [RFC5229] is enabled. 261 8. Formal Syntax 263 test =/ "mailboxidexists" string-list 265 tag =/ ":mailboxid" string 267 FCC =/ [":mailboxid" ] 268 ; if [@RFC8580] is supported 270 9. Security considerations 272 Because mailboxid is always generated by the server, implementations 273 MUST NOT allow sieve to make an endrun around this protection by 274 creating mailboxes with the specified ID by using ":create" and 275 ":mailboxid" in a fileinto rule for a non-existant mailbox. 277 Implementers are referred to the security considerations sections of 278 [RFC5228] and [RFC8474]. 280 10. IANA considerations 282 IANA are requested to add a capability to the sieve-extensions 283 registry: 285 To: iana@iana.org 286 Subject: Registration of new Sieve extension 288 Capability name: mailboxid 289 Description: adds a test for checking mailbox existence by objectid, 290 and new optional arguments to fileinto and :fcc which 291 allow selecting the destination mailbox by objectid. 292 RFC number: this RFC 293 Contact address: The EXTRA discussion list 295 11. Acknowledgements 297 This document borrows heavily from [RFC5490] for the matching 298 mailboxexists test, and from [RFC8579] for an example of modifying 299 the fileinto command. 301 Thanks to Ned Freed and Ken Murchison and Alexey Melnikov for 302 feedback on the EXTRA mailing list. 304 12. Changes 306 (EDITOR: remove this section before publication) 308 12.1. draft-ietf-sieve-mailboxid-03 310 * Fixed ABNF syntax error 312 12.2. draft-ietf-sieve-mailboxid-02 314 * removed bogus : from "mailboxidexists" test title 316 * moved FCC to its own top-level section since it is not used with 317 the fileinto command. 319 12.3. draft-ietf-sieve-mailboxid-01 321 * fixed idnits - RFC5228 not mentioned in the abstract 323 * fixed other I-D references I had missed, oops 325 12.4. draft-ietf-sieve-mailboxid-00 327 * Adopted into working group per adoption call on list 329 * Updated references to old drafts which have since been published. 331 * Fixed some typoes and simplified some language. 333 * Removed stray leading colon on mailboxexists (thanks Alexey) 335 * Added :fcc to the IANA registration description (thanks Alexey) 337 * Mentioned that variables can be expanded (thanks Alexey) 339 12.5. draft-gondwana-sieve-mailboxid-02 341 * Update document date by a couple of years! Ooops, it got 342 forgotten after a WGLC which got not dissent. 344 * Create xml2rfc v3 output. 346 12.6. draft-gondwana-sieve-mailboxid-01 348 * Switch to :mailboxid tagged parameter value with fallback mailbox 349 name. 351 * Document interaction with "mailbox". 353 * Document interaction with "special-use". 355 * Document interaction with "fcc". 357 * Document security considerations around :mailboxid and :create. 359 12.7. draft-gondwana-sieve-mailboxid-00 361 * Initial version. 363 13. Normative References 365 [RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email 366 Filtering Language", RFC 5228, DOI 10.17487/RFC5228, 367 January 2008, . 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 [RFC2342] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342, 379 DOI 10.17487/RFC2342, May 1998, 380 . 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 [RFC8580] Murchison, K. and B. Gondwana, "Sieve Extension: File 387 Carbon Copy (FCC)", RFC 8580, DOI 10.17487/RFC8580, May 388 2019, . 390 14. Informative References 392 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 393 RFC 4314, DOI 10.17487/RFC4314, December 2005, 394 . 396 [RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension", 397 RFC 5229, DOI 10.17487/RFC5229, January 2008, 398 . 400 [RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language -- 401 Extensions for Checking Mailbox Status and Accessing 402 Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March 403 2009, . 405 [RFC8579] Bosch, S., "Sieve Email Filtering: Delivering to Special- 406 Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019, 407 . 409 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 410 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 411 . 413 Author's Address 415 Bron Gondwana (editor) 416 Fastmail 417 Level 2, 114 William St 418 Melbourne VIC 3000 419 Australia 420 Email: brong@fastmailteam.com 421 URI: https://www.fastmail.com