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Internet Engineering Task Force (IETF)                      K. MurchisonRequest for Comments: 8440                                   B. GondwanaCategory: Standards Track                                       FastMailISSN: 2070-1721                                              August 2018IMAP4 Extension for Returning MYRIGHTS Information in Extended LISTAbstract   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 inSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttps://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 toBCP 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.Murchison & Gondwana         Standards Track                    [Page 1]

RFC 8440                   IMAP LIST-MYRIGHTS                August 2018Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .22.  Conventions Used in This Document . . . . . . . . . . . . . .23.  MYRIGHTS Return Option to LIST Command  . . . . . . . . . . .24.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .35.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . .46.  Security Considerations . . . . . . . . . . . . . . . . . . .47.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .48.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .48.1.  Registration of IMAP Capability LIST-MYRIGHTS . . . . . .48.2.  Registration of LIST-EXTENDED Option MYRIGHTS . . . . . .49.  References  . . . . . . . . . . . . . . . . . . . . . . . . .59.1.  Normative References  . . . . . . . . . . . . . . . . . .59.2.  Informative References  . . . . . . . . . . . . . . . . .6   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .6   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .61.  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 inBCP 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 theMurchison & Gondwana         Standards Track                    [Page 2]

RFC 8440                   IMAP LIST-MYRIGHTS                August 2018   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.Murchison & Gondwana         Standards Track                    [Page 3]

RFC 8440                   IMAP LIST-MYRIGHTS                August 20185.  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 Considerations8.1.  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 6Murchison & Gondwana         Standards Track                    [Page 4]

RFC 8440                   IMAP LIST-MYRIGHTS                August 2018   Intended usage:  COMMON   Person and email address to contact for further information:      Kenneth Murchison <murch@fastmailteam.com>   Owner/Change controller:  IESG <iesg@ietf.org>9.  References9.1.  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 inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174,              May 2017, <https://www.rfc-editor.org/info/rfc8174>.Murchison & Gondwana         Standards Track                    [Page 5]

RFC 8440                   IMAP LIST-MYRIGHTS                August 20189.2.  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: murch@fastmailteam.com   Bron Gondwana   FastMail Pty Ltd.   Level 2, 114 William Street   Melbourne, VIC  3000   Australia   Email: brong@fastmailteam.comMurchison & Gondwana         Standards Track                    [Page 6]