Internet DRAFT - draft-ietf-extra-imap-list-metadata
draft-ietf-extra-imap-list-metadata
EXTRA K. Murchison
Internet-Draft B. Gondwana
Intended status: Standards Track Fastmail
Expires: 20 June 2024 18 December 2023
IMAP4 Extension for Returning Mailbox METADATA in Extended LIST
draft-ietf-extra-imap-list-metadata-01
Abstract
This document defines an extension to the to IMAP LIST command that
allows the client to request mailbox annotations (metadata), along
with other information typically returned by the LIST command.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 20 June 2024.
Copyright Notice
Copyright (c) 2023 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/
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
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Murchison & Gondwana Expires 20 June 2024 [Page 1]
Internet-Draft IMAP LIST-METADATA December 2023
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. METADATA Return Option to LIST Command . . . . . . . . . . . 3
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8.1. Registration of IMAP capability LIST-METADATA . . . . . . 4
8.2. Registration of LIST-EXTENDED option METADATA . . . . . . 4
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Change History (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
IMAP clients sometimes fetch mailbox metadata (e.g. color) to augment
the display of mailboxes to the logged-in user. In order to do that,
the client is forced to issue a LIST or LSUB command to list all
available mailboxes, followed by a GETMETADATA command for each
mailbox found. This document defines an extension to the to IMAP
LIST command that is identified by the capability string "LIST-
METADATA". The LIST-METADATA extension allows the client to request
annotations on available mailboxes, along with other information
typically returned by the LIST command.
2. Conventions Used in This Document
In examples, "C:" indicates lines sent by a client that is connected
to a server. "S:" indicates lines sent by the server to the client.
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.
Murchison & Gondwana Expires 20 June 2024 [Page 2]
Internet-Draft IMAP LIST-METADATA December 2023
3. METADATA Return Option to LIST Command
[RFC5464] defines the GETMETADATA command which is used by an IMAP
client to retrieve mailbox annotations. Sometimes, a client will
have to look up the metadata for some or all of the mailboxes
returned by the LIST command. Doing so in multiple GETMETADATA
commands wastes bandwidth and can degrade performance if the client
does not pipeline the requests.
This document extends the LIST command with a new return option,
"METADATA", which allows the client to request all of the desired
information in a single command. For each listable mailbox matching
the list pattern and selection options, the server MUST return an
untagged LIST response followed by one or more untagged METADATA
responses containing the mailbox annotations requested by the client.
The untagged METADATA responses to an extended LIST command have the
same syntax and semantics as those that would be returned by
GETMETADATA commands on the same set of listable mailboxes (see
Section 4.4.1 of [RFC5464]). As per Section 4.4 of [RFC5464], the
server may return all requested annotations in a single METADATA
response for each mailbox, or it may split the requested annotations
into multiple METADATA responses for each mailbox.
If the server is unable to look up the annotations for given mailbox,
it MAY drop the corresponding METADATA response. In such a
situation, the LIST command would still return a tagged OK reply.
4. Examples
Note that the line wrapping of the extended LIST commands below is
for editorial purposes only.
In this example:
* The "color" annotation for the "foo" mailbox has not been set, so
the METADATA response has a value of "NIL" (has no value).
* The "bar" mailbox doesn't exist, so it has no METADATA response.
C: A01 LIST "" %
RETURN (METADATA ("/shared/vendor/cmu/cyrus-imapd/color"))
S: * LIST () "." "INBOX"
S: * METADATA INBOX ("/shared/vendor/cmu/cyrus-imapd/color" "#b71c1c")
S: * LIST () "." "foo"
S: * METADATA "foo" ("/shared/vendor/cmu/cyrus-imapd/color" NIL)
S: * LIST (\NonExistent) "." "bar"
S: A01 OK List completed.
Murchison & Gondwana Expires 20 June 2024 [Page 3]
Internet-Draft IMAP LIST-METADATA December 2023
In this example the LIST response for the "foo" mailbox is returned
because it has matching children, but no METADATA response is
returned because "foo" itself doesn't match the selection criteria.
C: A02 LIST (SUBSCRIBED RECURSIVEMATCH) "" %
RETURN (METADATA ("/shared/vendor/cmu/cyrus-imapd/color"))
S: * LIST (\Subscribed) "." "INBOX"
S: * METADATA INBOX ("/shared/vendor/cmu/cyrus-imapd/color" "#b71c1c")
S: * LIST () "." "foo" (CHILDINFO ("SUBSCRIBED"))
S: A02 OK List completed.
5. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) as described in [RFC5234]. Note that "return-option" is
defined in [RFC5258] and "entry" is defined in [RFC5464].
return-option =/ "METADATA" SP "(" entry *(SP entry) ")"
6. Security Considerations
This specification does not introduce any additional security
concerns beyond those described in [RFC5258].
7. Privacy Considerations
This specification does not introduce any additional privacy concerns
beyond those described in [RFC5464].
8. IANA Considerations
8.1. Registration of IMAP capability LIST-METADATA
This document defines the "LIST-METADATA" IMAP capability to be added
to the registry defined in Section 12.1 of [RFC9051].
8.2. Registration of LIST-EXTENDED option METADATA
This section registers the "METADATA" option to be added to the
registry defined in Section 9 of [RFC5258].
LIST-EXTENDED option name:
METADATA
LIST-EXTENDED option type:
RETURN
Murchison & Gondwana Expires 20 June 2024 [Page 4]
Internet-Draft IMAP LIST-METADATA December 2023
LIST-EXTENDED option description:
Causes the LIST command to return METADATA responses in addition
to LIST responses.
Published specification:
RFC XXXX, Section 3
Security considerations:
RFC XXXX, Section 6
Intended usage:
COMMON
Person and email address to contact for further information:
Kenneth Murchison <murch@fastmailteam.com>, Bron Gondwana
<brong@fastmailteam.com>
Owner/Change controller:
IESG <iesg@ietf.org>
9. References
9.1. Normative References
[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>.
[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>.
[RFC5258] Leiba, B. and A. Melnikov, "Internet Message Access
Protocol version 4 - LIST Command Extensions", RFC 5258,
DOI 10.17487/RFC5258, June 2008,
<https://www.rfc-editor.org/info/rfc5258>.
[RFC5464] Daboo, C., "The IMAP METADATA Extension", RFC 5464,
DOI 10.17487/RFC5464, February 2009,
<https://www.rfc-editor.org/info/rfc5464>.
[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>.
Murchison & Gondwana Expires 20 June 2024 [Page 5]
Internet-Draft IMAP LIST-METADATA December 2023
[RFC9051] Melnikov, A., Ed. and B. Leiba, Ed., "Internet Message
Access Protocol (IMAP) - Version 4rev2", RFC 9051,
DOI 10.17487/RFC9051, August 2021,
<https://www.rfc-editor.org/info/rfc9051>.
Appendix A. Change History (To be removed by RFC Editor before
publication)
Changes from draft-ietfextra-imap-list-metadata-00:
* Added missing SP in ABNF.
Changes from draft-murchison-imap-list-metadata-02:
* Renamed as a WG document.
* Clarified that the METADATA response with values is used.
* Miscellaneous editorial changes.
Changes from draft-murchison-imap-list-metadata-01:
* None.
Changes from draft-murchison-imap-list-metadata-00:
* Updated Keywords boilerplate.
* Changed RFC 3501 reference to RFC 9051.
Authors' Addresses
Kenneth Murchison
Fastmail US LLC
1429 Walnut Street - Suite 1201
Philadelphia, PA 19102
United States of America
Email: murch@fastmailteam.com
Bron Gondwana
Fastmail Pty Ltd
Level 2, 114 William Street
Melbourne VIC 3000
Australia
Email: brong@fastmailteam.com
Murchison & Gondwana Expires 20 June 2024 [Page 6]
