Internet DRAFT - draft-ietf-extra-sieve-mailboxid
draft-ietf-extra-sieve-mailboxid
EXTRA B. Gondwana, Ed.
Internet-Draft Fastmail
Updates: 5228 (if approved) 16 March 2021
Intended status: Standards Track
Expires: 17 September 2021
Sieve Email Filtering: delivery by mailboxid
draft-ietf-extra-sieve-mailboxid-09
Abstract
The OBJECTID capability of the IMAP protocol (RFC8474) allows clients
to identify mailboxes by a unique identifier which survives rename.
This document extends the Sieve mail filtering language (RFC5228) to
allow using that same unique identifier as a target for fileinto
rules, and for testing the existance of mailboxes.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 17 September 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used In This Document . . . . . . . . . . . . . . 3
3. Sieve capability string . . . . . . . . . . . . . . . . . . . 3
4. Argument ":mailboxid" to Command "fileinto" . . . . . . . . . 3
4.1. Interaction with "mailbox" extension . . . . . . . . . . 4
4.2. Interaction with "specialuse" extension . . . . . . . . . 4
5. Interaction with "fcc" extension . . . . . . . . . . . . . . 5
6. Test "mailboxidexists" . . . . . . . . . . . . . . . . . . . 5
7. Interaction with variables extension . . . . . . . . . . . . 6
8. Security considerations . . . . . . . . . . . . . . . . . . . 6
9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 6
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
11. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
11.1. draft-ietf-sieve-mailboxid-09 . . . . . . . . . . . . . 7
11.2. draft-ietf-sieve-mailboxid-08 . . . . . . . . . . . . . 7
11.3. draft-ietf-sieve-mailboxid-07 . . . . . . . . . . . . . 7
11.4. draft-ietf-sieve-mailboxid-06 . . . . . . . . . . . . . 8
11.5. draft-ietf-sieve-mailboxid-05 . . . . . . . . . . . . . 8
11.6. draft-ietf-sieve-mailboxid-04 . . . . . . . . . . . . . 8
11.7. draft-ietf-sieve-mailboxid-03 . . . . . . . . . . . . . 8
11.8. draft-ietf-sieve-mailboxid-02 . . . . . . . . . . . . . 8
11.9. draft-ietf-sieve-mailboxid-01 . . . . . . . . . . . . . 8
11.10. draft-ietf-sieve-mailboxid-00 . . . . . . . . . . . . . 8
11.11. draft-gondwana-sieve-mailboxid-02 . . . . . . . . . . . 9
11.12. draft-gondwana-sieve-mailboxid-01 . . . . . . . . . . . 9
11.13. draft-gondwana-sieve-mailboxid-00 . . . . . . . . . . . 9
12. Normative References . . . . . . . . . . . . . . . . . . . . 9
13. Informative References . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
[RFC5228] Sieve rules are sometimes created using graphical
interfaces which allow users to select the mailbox to be used as a
target for a rule.
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If that mailbox is renamed, the client may also update its internal
representation of the rule and update the sieve script to match,
however this is a multi-step process and subject to partial failures.
Also, if the folder is renamed by a different mechanism (e.g. another
IMAP client) the rules will get out of sync.
By telling "fileinto" to reference the immutable mailboxid specified
by [RFC8474], using the extension specified herein, sieve rules can
continue to target the same mailbox even if it gets renamed.
2. Conventions Used In This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Sieve capability string
Scripts which use the following extensions MUST explicitly require
the capability "mailboxid".
Example:
require "mailboxid";
4. Argument ":mailboxid" to Command "fileinto"
Normally, the "fileinto" command delivers the message in the mailbox
specified using its positional mailbox argument. However, if the
optional ":mailboxid" argument is also specified, the "fileinto"
command first checks whether a mailbox exists in the user's personal
namespace [RFC2342] with the specified [RFC8474] MAILBOXID.
If a matching mailbox is found, that mailbox is used for delivery.
If there is no such mailbox, the "fileinto" action proceeds as it
would without the ":mailboxid" argument.
The tagged argument ":mailboxid" to fileinto consumes one additional
token, a string with the objectid of the mailbox to file into.
Example:
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require "fileinto";
require "mailboxid";
if header :contains ["from"] "coyote" {
fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3"
"INBOX.harassment";
}
4.1. Interaction with "mailbox" extension
For servers which also support the [RFC5490] mailbox extension, if
both the ":create" and ":mailboxid" arguments are provided to a
"fileinto" command and no matching mailbox is found, then a new
mailbox will be created.
This new mailbox will have the name specified by the positional
mailbox argument ([RFC5228] section 4.1), however it will get a
different mailboxid (chosen by the server) rather than the one
specified by the ":mailboxid" argument to fileinto.
Example:
require "fileinto";
require "mailboxid";
require "mailbox";
fileinto :mailboxid "Fnosuch"
:create
"INBOX.no-such-folder";
# creates INBOX.no-such-folder, but it doesn't
# get the "Fnosuch" mailboxid.
4.2. Interaction with "specialuse" extension
For servers which also support [RFC8579] delivery to special-use
mailboxes, it is an error to specify both ":mailboxid" and
":specialuse" in the same fileinto command.
Advanced filtering based on both special-use and mailboxid can be
built with explicit "specialuse_exists" and "mailboxidexists" tests.
Note to developers of sieve generation tools: it is advisable to use
special-use rather than mailboxid when creating rules that are based
on a special-use purpose (e.g. delivery directly to the Junk folder
based on a header that was added by a scanning agent earlier in the
mailflow).
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5. Interaction with "fcc" extension
This document extends the definition of the ":fcc" argument defined
in [RFC8580] so that it can optionally be used with the ":mailboxid"
argument. The syntax for "FCC" is extended here using ABNF
[RFC5234]:
MAILBOXID-OPT = ":mailboxid" objectid
FCC-OPTS =/ MAILBOXID-OPT
If the optional ":mailboxid" argument is specified with ":fcc", it
instructs the Sieve interpreter to check whether a mailbox exists
with the specific mailboxid. If such a mailbox exists, the generated
message is filed into that mailbox. Otherwise, the generated message
is filed into the ":fcc" target mailbox.
As with fileinto, it is an error to specify both ":mailboxid" and
":specialuse" for the same fcc rule.
Example:
require ["enotify", "fcc", "mailboxid"];
notify :fcc "INBOX.Sent"
:mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3"
:message "You got mail!"
"mailto:ken@example.com";
6. Test "mailboxidexists"
The "mailboxidexists" test is true if all mailboxes listed in the
"mailboxids" argument exist in the mailstore, and each allows the
user in whose context the Sieve script runs to "deliver" messages
into it. When the mailstore is an IMAP server, "delivery" of
messages is possible if:
a) the READ-WRITE response code is present for the mailbox (see
Section 7.1 of [RFC3501]), if IMAP Access Control List (ACL)
[RFC4314] is not supported by the server, or
b) the user has 'p' or 'i' rights for the mailbox (see Section 5.2 of
[RFC4314]).
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Note that a successful "mailboxidexists" test for a mailbox doesn't
necessarily mean that a "fileinto :mailboxid" action on this mailbox
would succeed. For example, the "fileinto" action might put user
over quota. The "mailboxidexists" test only verifies existence of
the mailbox and whether the user in whose context the Sieve script
runs has permissions to execute "fileinto" on it.
Example:
require "fileinto";
require "mailboxid";
if header :contains ["from"] "coyote" {
if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" {
fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3"
"INBOX.name.will.not.be.used";
} else {
fileinto "INBOX.harassment";
}
}
Note to implementers: this test behaves identically to the
"mailboxexists" test defined in [RFC5490] but operates on mailboxids
rather than mailbox names.
7. Interaction with variables extension
There is no special interaction defined, however as an objectid is a
string in this document, objectid values can contain variable
expansions if [RFC5229] is enabled.
8. Security considerations
Because mailboxid is always generated by the server, implementations
MUST NOT allow sieve to make an endrun around this protection by
creating mailboxes with the specified ID by using ":create" and
":mailboxid" in a fileinto rule for a non-existant mailbox.
Implementers are referred to the security considerations sections of
[RFC5228] and [RFC8474].
9. IANA considerations
IANA are requested to add a capability to the sieve-extensions
registry:
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To: iana@iana.org
Subject: Registration of new Sieve extension
Capability name: mailboxid
Description: adds a test for checking mailbox existence by objectid,
and new optional arguments to fileinto and :fcc which
allow selecting the destination mailbox by objectid.
RFC number: this RFC
Contact address: The EXTRA discussion list <extra@ietf.org>
10. Acknowledgements
This document borrows heavily from [RFC5490] for the matching
mailboxexists test, and from [RFC8579] for an example of modifying
the fileinto command.
Thanks to Ned Freed and Ken Murchison and Alexey Melnikov for
feedback on the EXTRA mailing list.
11. Changes
(EDITOR: remove this section before publication)
11.1. draft-ietf-sieve-mailboxid-09
* update FCC-OPTS to have an intermediate production for the
:mailboxid option, and reference "objectid" from RFC8474 as the
valid format for the option value.
11.2. draft-ietf-sieve-mailboxid-08
* IETF110 discussion - re-add FCC-OPTS syntax, and clarify that
:mailboxid is incompatible with :specialuse to parallel the
fileinto behaviour
11.3. draft-ietf-sieve-mailboxid-07
* Martin Duke review - remove formal section
* Martin Duke review - wording for section 4.1 (interaction with
:create)
* Ken Murchison review - fixed :special-use to :specialuse per
RFC8579
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11.4. draft-ietf-sieve-mailboxid-06
* GENART review - fixed example to not be semantically pointless
* GENART review - fixed !@ to @! in RFC reference mmark syntax
11.5. draft-ietf-sieve-mailboxid-05
* disallow :mailboxid and :special-use in the same fileinto action.
11.6. draft-ietf-sieve-mailboxid-04
* made RFC5490 and RFC8579 normative
* clarified wording based on AD feedback from Barry
11.7. draft-ietf-sieve-mailboxid-03
* Fixed ABNF syntax error
11.8. draft-ietf-sieve-mailboxid-02
* removed bogus : from "mailboxidexists" test title
* moved FCC to its own top-level section since it is not used with
the fileinto command.
11.9. draft-ietf-sieve-mailboxid-01
* fixed idnits - RFC5228 not mentioned in the abstract
* fixed other I-D references I had missed, oops
11.10. draft-ietf-sieve-mailboxid-00
* Adopted into working group per adoption call on list
* Updated references to old drafts which have since been published.
* Fixed some typoes and simplified some language.
* Removed stray leading colon on mailboxexists (thanks Alexey)
* Added :fcc to the IANA registration description (thanks Alexey)
* Mentioned that variables can be expanded (thanks Alexey)
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11.11. draft-gondwana-sieve-mailboxid-02
* Update document date by a couple of years! Ooops, it got
forgotten after a WGLC which got not dissent.
* Create xml2rfc v3 output.
11.12. draft-gondwana-sieve-mailboxid-01
* Switch to :mailboxid tagged parameter value with fallback mailbox
name.
* Document interaction with "mailbox".
* Document interaction with "special-use".
* Document interaction with "fcc".
* Document security considerations around :mailboxid and :create.
11.13. draft-gondwana-sieve-mailboxid-00
* Initial version.
12. Normative References
[RFC5228] Guenther, P., Ed. and T. Showalter, Ed., "Sieve: An Email
Filtering Language", RFC 5228, DOI 10.17487/RFC5228,
January 2008, <https://www.rfc-editor.org/info/rfc5228>.
[RFC8474] Gondwana, B., Ed., "IMAP Extension for Object
Identifiers", RFC 8474, DOI 10.17487/RFC8474, September
2018, <https://www.rfc-editor.org/info/rfc8474>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC2342] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
DOI 10.17487/RFC2342, May 1998,
<https://www.rfc-editor.org/info/rfc2342>.
[RFC8580] Murchison, K. and B. Gondwana, "Sieve Extension: File
Carbon Copy (FCC)", RFC 8580, DOI 10.17487/RFC8580, May
2019, <https://www.rfc-editor.org/info/rfc8580>.
13. Informative References
[RFC8579] Bosch, S., "Sieve Email Filtering: Delivering to Special-
Use Mailboxes", RFC 8579, DOI 10.17487/RFC8579, May 2019,
<https://www.rfc-editor.org/info/rfc8579>.
[RFC5490] Melnikov, A., "The Sieve Mail-Filtering Language --
Extensions for Checking Mailbox Status and Accessing
Mailbox Metadata", RFC 5490, DOI 10.17487/RFC5490, March
2009, <https://www.rfc-editor.org/info/rfc5490>.
[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003,
<https://www.rfc-editor.org/info/rfc3501>.
[RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension",
RFC 4314, DOI 10.17487/RFC4314, December 2005,
<https://www.rfc-editor.org/info/rfc4314>.
[RFC5229] Homme, K., "Sieve Email Filtering: Variables Extension",
RFC 5229, DOI 10.17487/RFC5229, January 2008,
<https://www.rfc-editor.org/info/rfc5229>.
Author's Address
Bron Gondwana (editor)
Fastmail
Level 2, 114 William St
Melbourne VIC 3000
Australia
Email: brong@fastmailteam.com
URI: https://www.fastmail.com
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