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

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
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   This Internet-Draft will expire on December 9, 2018.
   https://www.rfc-editor.org/info/rfc8440.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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