Internet Engineering Task Force (IETF)                      K. Murchison
Request for Comments: 8440                                   B. Gondwana
Category: Standards Track                                       FastMail
ISSN: 2070-1721                                              August 2018


 IMAP4 Extension for Returning MYRIGHTS Information in Extended LIST

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 is an Internet Standards Track document.

  This document is a product of the Internet Engineering Task Force
  (IETF).  It represents the consensus of the IETF community.  It has
  received public review and has been approved for publication by the
  Internet Engineering Steering Group (IESG).  Further information on
  Internet Standards is available in Section 2 of RFC 7841.

  Information about the current status of this document, any errata,
  and how to provide feedback on it may be obtained at
  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.

  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 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.








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Table of Contents

  1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
  2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
  3.  MYRIGHTS Return Option to LIST Command  . . . . . . . . . . .   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 LIST-MYRIGHTS . . . . . .   4
    8.2.  Registration of LIST-EXTENDED Option MYRIGHTS . . . . . .   4
  9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
    9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
    9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
  Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   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 [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, 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



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  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] 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 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 they are interested.

4.  Examples

  In this 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, the LIST reply for the "foo" mailbox is returned
  because it has matching children, but no MYRIGHTS reply is 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.






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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 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 LIST-MYRIGHTS

  This document defines the "LIST-MYRIGHTS" IMAP capability that has
  been added to the "IMAP Capabilities" registry [CAPABILITIES].

8.2.  Registration of LIST-EXTENDED Option MYRIGHTS

  This section registers the "MYRIGHTS" option that has been added to
  the "LIST-EXTENDED options" 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 8440, Section 3

  Security considerations:  RFC 8440, Section 6



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  Intended usage:  COMMON

  Person and email address to contact for further information:
     Kenneth Murchison <[email protected]>

  Owner/Change controller:  IESG <[email protected]>

9.  References

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>.




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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>.

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 Barry Leiba for contributing his ideas and support for
  writing this specification.

Authors' Addresses

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

  Email: [email protected]


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

  Email: [email protected]


















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