IMAP4 Extension for Returning MYRIGHTS Information in Extended LIST
draft-ietf-extra-imap-list-myrights-02

EXTRA                                                       K. Murchison
Internet-Draft                                               B. Gondwana
Intended status: Standards Track                                FastMail
Expires: September 23, 2018                               March 22, 2018

  IMAP4 Extension for Returning MYRIGHTS Information in Extended LIST
                 draft-ietf-extra-imap-list-myrights-02

Abstract

   This document defines an extension to the to 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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   This Internet-Draft will expire on September 23, 2018.

Copyright Notice

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   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.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   5
     10.2.  Informative References . . . . . . . . . . . . . . . . .   5
   Appendix A.  Change History (To be removed by RFC Editor before
                publication) . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   IMAP 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
   [RFC2119].

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

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   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 return option,
   "MYRIGHTS", 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 an untagged MYRIGHTS response
   containing the set of rights granted to the logged-in user.

   If the server is unable to look up the set of rights for a given
   mailbox, it MAY drop the corresponding MYRIGHTS reply.  In such a
   situation, the LIST command would still return a tagged OK reply.

   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 whose
   rights in which 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

   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 LIST-MYRIGHTS

   This document defines the "LIST-MYRIGHTS" IMAP capability to be added
   to the registry defined in Section 12 of [RFC3501].

8.2.  Registration of LIST-EXTENDED option MYRIGHTS

   This section registers the "MYRIGHTS" option to be added to the
   registry defined in Section 9 of [RFC5258].

   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, Section 3

   Security considerations:  RFC XXXX, Section 6

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   Intended usage:  COMMON

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

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

9.  Acknowledgments

   This document is based largely on [RFC5819].  The author would like
   to thank the authors of that document for providing both inspiration
   and some borrowed text for this document.

10.  References

10.1.  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>.

   [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>.

10.2.  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>.

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

   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 document 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.

Authors' Addresses

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

   Email: murch@fastmailteam.com

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

   Email: brong@fastmailteam.com

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