Internet DRAFT - draft-gondwana-sieve-mailboxid
draft-gondwana-sieve-mailboxid
EXTRA B. Gondwana, Ed.
Internet-Draft FastMail
Updates: 5228 (if approved) 17 June 2020
Intended status: Standards Track
Expires: 19 December 2020
Sieve Email Filtering: delivery by mailboxid
draft-gondwana-sieve-mailboxid-02
Abstract
The OBJECTID capability of the IMAP protocol (I-D.ietf-extra-imap-
objectid) allows clients to identify mailboxes by a unique identifier
which survives rename. In contrast, the Sieve mail filtering
language (RFC 5228) currently has no such capability. This memo
defines a Sieve extension that fills this gap: it adds a method for
specifying the unique identifier of a mailbox as a target for
fileinto rules, and a method for testing the existence of a mailbox
by its unique identifier.
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 19 December 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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extracted from this document must include Simplified BSD License text
as described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used In This Document . . . . . . . . . . . . . . 2
3. Sieve capability string . . . . . . . . . . . . . . . . . . . 3
4. Argument ":mailboxid" to Command "fileinto" . . . . . . . . . 3
4.1. Interaction with "mailbox" extension . . . . . . . . . . 3
4.2. Interaction with "specialuse" extension . . . . . . . . . 4
4.3. Interaction with "fcc" extension . . . . . . . . . . . . 5
5. Test ":mailboxidexists" . . . . . . . . . . . . . . . . . . . 5
6. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Security considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA considerations . . . . . . . . . . . . . . . . . . . . . 6
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
10. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. draft-gondwana-sieve-mailboxid-02 . . . . . . . . . . . 7
10.2. draft-gondwana-sieve-mailboxid-01 . . . . . . . . . . . 7
10.3. draft-gondwana-sieve-mailboxid-00 . . . . . . . . . . . 7
11. TODO . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
12. Normative References . . . . . . . . . . . . . . . . . . . . 8
13. Informative References . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Sieve rules are sometimes created using graphical interfaces which
allow users to select the mailbox to be used as a target for a rule.
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 extending "fileinto" to reference an immutable mailboxid, sieve
rules can continue to target the same mailbox, regardless of how 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.
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3. Sieve capability string
The server advertises the capability "mailboxid", and scripts which
use the following extensions MUST explicitly request 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 [I-D.ietf-extra-imap-objectid]
MAILBOXID. If that is the case, that mailbox is used for delivery
instead. 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:
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, the
":create" modifier to fileinto does not create mailbox with the
specified mailboxid, however it may be specified and interacts as
normal with all other extensions.
Example:
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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 [I-D.ietf-extra-sieve-special-use], if
a fileinto command has both ":mailboxid" and ":special-use"
specified, then the mailboxid is resolved first. If the mailboxid
does not exist, then the special-use is evaluated next following the
process specified in [I-D.ietf-extra-sieve-special-use] - this
includes processing of [RFC5490] ":create" tags to add the special-
use on creation.
Example:
require "fileinto";
require "mailboxid";
require "special-use";
if header :contains ["from"] "coyote" {
fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3"
:specialuse "\\Junk"
"INBOX.harassment";
}
Example:
require "fileinto";
require "mailboxid";
require "mailbox";
require "special-use";
fileinto :mailboxid "F1234567"
:specialuse "\\Archive"
:create
"INBOX.Archive";
# creates INBOX.Archive with use \Archive but
# with a different mailboxid.
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4.3. Interaction with "fcc" extension
This document extends the definition of the :fcc argument so that it
can optionally be used with the ":mailboxid" argument.
FCC =/ [":mailboxid" <mailboxid: string>]
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.
Example:
require ["enotify", "fcc", "mailboxid"];
notify :fcc "INBOX.Sent"
:mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3"
:message "You got mail!"
"mailto:ken@example.com";
5. 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]).
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" 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:
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require "fileinto";
require "mailboxid";
if header :contains ["from"] "coyote" {
if mailboxidexists "F6352ae03-b7f5-463c-896f-d8b48ee3" {
fileinto :mailboxid "F6352ae03-b7f5-463c-896f-d8b48ee3"
"INBOX.harassment";
} else {
fileinto "INBOX.harassment";
}
}
Not to implementers: this test behaves identically to the
"mailboxexists" test defined in [RFC5490] but operates on mailboxids
rather than mailbox names.
6. Formal Syntax
test /= ":mailboxidexists" string-list
tag /= ":mailboxid" string
If [I-D.ietf-extra-sieve-fcc] is supported:
FCC =/ [":mailboxid" <mailboxid: string>]
7. 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
those documents in [RFC5228], [I-D.ietf-extra-imap-objectid].
8. 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 test for checking for mailbox existence by objectid
and a new optional argument to fileinto to select the
destination mailbox using objectid.
RFC number: this RFC
Contact address: The EXTRA discussion list <extra@ietf.org>
9. Acknowledgements
This document borrows heavily from [RFC5490] for the matching
mailboxexists test, and from [I-D.ietf-extra-sieve-special-use] for
an example of modifying the fileinto command.
Thanks to Ned Freed and Ken Murchison for feedback on the EXTRA
mailing list.
10. Changes
(EDITOR: remove this section before publication)
10.1. 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.
10.2. 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.
10.3. draft-gondwana-sieve-mailboxid-00
* Initial version.
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11. TODO
Is there a more explicit way to update the grammar? It seems less
fully specified than IMAP.
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>.
[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>.
[RFC2342] Gahrns, M. and C. Newman, "IMAP4 Namespace", RFC 2342,
DOI 10.17487/RFC2342, May 1998,
<https://www.rfc-editor.org/info/rfc2342>.
[I-D.ietf-extra-imap-objectid]
Gondwana, B., "IMAP Extension for object identifiers",
Work in Progress, Internet-Draft, draft-ietf-extra-imap-
objectid-08, 2 August 2018, <https://tools.ietf.org/html/
draft-ietf-extra-imap-objectid-08>.
[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>.
13. Informative References
[I-D.ietf-extra-sieve-special-use]
Bosch, S., "Sieve Email Filtering: Delivering to Special-
Use Mailboxes", Work in Progress, Internet-Draft, draft-
ietf-extra-sieve-special-use-05, 24 January 2019,
<https://tools.ietf.org/html/draft-ietf-extra-sieve-
special-use-05>.
[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>.
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[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>.
[I-D.ietf-extra-sieve-fcc]
Murchison, K. and B. Gondwana, "Sieve Extension: File
Carbon Copy (Fcc)", Work in Progress, Internet-Draft,
draft-ietf-extra-sieve-fcc-09, 13 January 2019,
<https://tools.ietf.org/html/draft-ietf-extra-sieve-fcc-
09>.
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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