wdiff rfc8440.original rfc8440.txt

EXTRA
Internet Engineering Task Force (IETF) K. Murchison
Internet-Draft
Request for Comments: 8440 B. Gondwana
Intended status:
Category: Standards Track FastMail
Expires: December 9, 2018 June 7,
ISSN: 2070-1721 August 2018

IMAP4 Extension for Returning MYRIGHTS Information in Extended LIST
draft-ietf-extra-imap-list-myrights-07

Abstract

This document defines an extension to the Internet Message Access
Protocol (IMAP) LIST command that allows the client to request the
set of rights that the logged-in user has been granted on mailboxes,
along with other information typically returned by the LIST command.

Status of This Memo

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provisions of BCP 78 and BCP 79.

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Internet-Drafts are draft documents valid the IETF community. It has
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This Internet-Draft will expire on December 9, 2018.
https://www.rfc-editor.org/info/rfc8440.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. MYRIGHTS Return Option to LIST Command . . . . . . . . . . . 3 2
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 Capability LIST-MYRIGHTS . . . . . . 4
8.2. Registration of LIST-EXTENDED option Option MYRIGHTS . . . . . . 5 4
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
10.1.
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
10.2.
9.2. Informative References . . . . . . . . . . . . . . . . . 6
10.3. URIs . . . . . . . . . . . . . . . . . . .
Acknowledgments . . . . . . . 6
Appendix A. Change History (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 6

1. Introduction

IMAP [RFC3501] clients typically fetch the set of rights granted on
mailboxes so they can expose the allowed functionality 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
MYRIGHTS command for each mailbox found. This document defines an
extension to the to IMAP LIST command that is identified by the
capability string "LIST-MYRIGHTS". The LIST-MYRIGHTS extension
allows the client to request the set of rights that the logged-in
user has been granted on 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 [1] [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

3. MYRIGHTS Return Option to LIST Command

[RFC4314] defines the MYRIGHTS command command, which is used by an IMAP
client to determine the set of rights that the logged-in user has
been granted on a given mailbox. Frequently, a client will have to
look up the rights for some or all of the mailboxes returned by the
LIST command. Doing so in multiple MYRIGHTS commands wastes
bandwidth and can degrade performance if the client does not pipeline
the requests.

This document extends the LIST command with a new "MYRIGHTS" return
option [RFC5258], which [RFC5258] that 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 and SHOULD also return an untagged MYRIGHTS
response containing the set of rights granted to the logged-
in logged-in user.
The ordering of the responses is significant only in that the server
MUST NOT send a MYRIGHTS response for a given mailbox before it sends
the LIST response for that mailbox.

If the server is unable to look up the set of rights for a given
mailbox, it does not send the MYRIGHTS reply for that mailbox.

Client authors ought to note that generating the MYRIGHTS responses
for a large number of mailboxes may be an expensive operation for the
server. Clients SHOULD use a suitable match pattern and/or selection
option to limit the set of mailboxes returned to only those in whose
rights in which they are interested.

4. Examples

In this example example, the "bar" mailbox doesn't exist, so it has no
MYRIGHTS reply.

C: A01 LIST "" % RETURN (MYRIGHTS)
S: * LIST () "." "INBOX"
S: * MYRIGHTS "INBOX" lrswipkxtecda
S: * LIST () "." "foo"
S: * MYRIGHTS "foo" lrs
S: * LIST (\NonExistent) "." "bar"
S: A01 OK List completed.

In this example example, the LIST reply for the "foo" mailbox is returned
because it has matching children, but no MYRIGHTS reply is returned returned,
because "foo" itself doesn't match the selection criteria.

C: A02 LIST (SUBSCRIBED RECURSIVEMATCH) "" % RETURN (MYRIGHTS)
S: * LIST (\Subscribed) "." "INBOX"
S: * MYRIGHTS "INBOX" lrswipkxtecda
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]. Terms not defined here are
taken from [RFC5258].

return-option =/ "MYRIGHTS"

6. Security Considerations

In addition to the security considerations described in [RFC4314],
this extension makes it a bit easier for clients to overload the
server by requesting MYRIGHTS information for a large number of
mailboxes. However, as already noted in the introduction, existing clients
already try to do that by generating a large number of MYRIGHTS
commands for each mailbox in which they are interested. While
performing MYRIGHTS information retrieval for big lists of mailboxes,
a server implementation needs to make sure that it can still serve
other IMAP connections and yield execution to other connections, when
necessary.

7. Privacy Considerations

This specification does not introduce any additional privacy concerns
beyond those described in [RFC4314].

8. IANA Considerations

8.1. Registration of IMAP capability Capability LIST-MYRIGHTS

This document defines the "LIST-MYRIGHTS" IMAP capability to be that has
been added to the "IMAP Capabilities" registry:
<https://www.iana.org/assignments/imap-capabilities/imap-
capabilities.xhtml#imap-capabilities-1>. registry [CAPABILITIES].

8.2. Registration of LIST-EXTENDED option Option MYRIGHTS

This section registers the "MYRIGHTS" option to be that has been added to
the "LIST-EXTENDED options" registry: <https://www.iana.org/assignments/
imap-list-extended/imap-list-extended.xhtml#imap-list-extended-1>. registry [EXTENDED].

LIST-EXTENDED option name: MYRIGHTS

LIST-EXTENDED option type: RETURN

LIST-EXTENDED option description: Causes the LIST command to return
MYRIGHTS responses in addition to LIST responses.

Published specification: RFC XXXX, 8440, Section 3

Security considerations: RFC XXXX, 8440, Section 6
Intended usage: COMMON

Person and email address to contact for further information:
Kenneth Murchison <murch@fastmail.com> <murch@fastmailteam.com>

Owner/Change controller: IESG <iesg@ietf.org>

9. Acknowledgments

This document is based largely on [RFC5819]. The authors would like
to thank the authors of that document for providing both inspiration
and some borrowed text for this document. The authors would also
like to thank the following individuals for contributing their ideas
and support for writing this specification: Barry Leiba.

10. References

10.1.

9.1. Normative References

[CAPABILITIES]
IANA, "Internet Message Access Protocol (IMAP)
Capabilities Registry", <https://www.iana.org/assignments/
imap-capabilities/imap-capabilities>.

[EXTENDED]
IANA, "Internet Message Access Protocol (IMAP) LIST
EXTENDED Registry",
<https://www.iana.org/assignments/imap-list-extended>.

[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>.

[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>.

[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>.

[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>.

10.2.

9.2. Informative References

[RFC5819] Melnikov, A. and T. Sirainen, "IMAP4 Extension for
Returning STATUS Information in Extended LIST", RFC 5819,
DOI 10.17487/RFC5819, March 2010,
<https://www.rfc-editor.org/info/rfc5819>.

10.3. URIs

[1] https://tools.ietf.org/html/bcp14

Appendix A. Change History (To be removed by RFC Editor before
publication)

Changes from draft-ietf-extra-imap-list-myrights-06:

o Editorial fix.

Changes from draft-ietf-extra-imap-list-myrights-05:

o Updated Keywords boilerplate.

o Referenced security concerns in RFC 4314.

o Reworded first sentence in second paragraph of Section 3.

o Added informative reference

Acknowledgments

This document is based largely on [RFC5819]. The authors would like
to RFC5819.

Changes from draft-ietf-extra-imap-list-myrights-04:

o Added references for "IMAP" and "return option".

Changes from draft-ietf-extra-imap-list-myrights-03:

o Fixed a typo in thank the Abstract.

Changes from draft-ietf-extra-imap-list-myrights-02:

o WGLC editorial changes from Barry Leiba.

Changes from draft-ietf-extra-imap-list-myrights-01:

o Removed 'n' right from example.

o Added advice to client authors regarding expense of calculating
MYRIGHTS.

o Replicated Security Considerations section from RFC 5819.

Changes from draft-ietf-extra-imap-list-myrights-00:

o Corrected contact email address in IANA registration.

o Fixed typos (extra SP) in examples.

Changes from draft-murchison-imap-list-myrights-01:

o Renamed that document for providing both inspiration
and some borrowed text for this document. The authors would also
like to be a work product of the EXTRA WG.

o Updated authors' addresses.

Changes from draft-murchison-imap-list-myrights-00:

o Augmented Introduction with mention of "LIST-MYRIGHTS" capability
string.

o Minor editorial changes. thank Barry Leiba for contributing his ideas and support for
writing this specification.

Authors' Addresses

Kenneth Murchison
FastMail Pty Ltd Ltd.
Level 2, 114 William Street
Melbourne, VIC 3000
Australia

Email: murch@fastmailteam.com

Bron Gondwana
FastMail Pty Ltd Ltd.
Level 2, 114 William Street
Melbourne, VIC 3000
Australia

Email: brong@fastmailteam.com