The Sieve Mail-Filtering Language -- Extensions for Checking Mailbox Status and Accessing Mailbox Metadata
draft-melnikov-sieve-imapext-metadata-08

Sieve Working Group                                          A. Melnikov
Internet-Draft                                             Isode Limited
Intended status: Standards Track                       December 16, 2008
Expires: June 19, 2009

  The Sieve mail filtering language - extensions for checking mailbox
                 status and accessing mailbox metadata
                draft-melnikov-sieve-imapext-metadata-08

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Abstract

   This memo defines an extension to the Sieve mail filtering language
   (RFC 5228) for accessing mailbox and server annotations.

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Table of Contents

   1.    Introduction . . . . . . . . . . . . . . . . . . . . . . . .  3

   2.    Conventions used in this document  . . . . . . . . . . . . .  3

   3.    mailbox and mboxmetadata extensions  . . . . . . . . . . . .  3
   3.1.  Test mailboxexists . . . . . . . . . . . . . . . . . . . . .  3
   3.2.  ':create' argument to 'fileinto' command . . . . . . . . . .  4
   3.3.  Test metadata  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.4.  Test metadataexists  . . . . . . . . . . . . . . . . . . . .  5

   4.    servermetadata extension . . . . . . . . . . . . . . . . . .  5
   4.1.  Test servermetadata  . . . . . . . . . . . . . . . . . . . .  5
   4.2.  Test servermetadataexists  . . . . . . . . . . . . . . . . .  6

   5.    Security Considerations  . . . . . . . . . . . . . . . . . .  6

   6.    IANA Considerations  . . . . . . . . . . . . . . . . . . . .  7

   7.    Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  7

   8.    References . . . . . . . . . . . . . . . . . . . . . . . . .  8
   8.1.  Normative References . . . . . . . . . . . . . . . . . . . .  8
   8.2.  Informative References . . . . . . . . . . . . . . . . . . .  8

         Author's Address . . . . . . . . . . . . . . . . . . . . . .  9
         Intellectual Property and Copyright Statements . . . . . . . 10

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1.  Introduction

   This memo defines an extension to the Sieve mail filtering language
   [SIEVE] for accessing mailbox and server annotations.  This allows
   for customization of the Sieve engine behaviour based on variables
   set using [METADATA].

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [KEYWORDS].

   Conventions for notations are as in [SIEVE] section 1.1, including
   the use of [ABNF].

   This document is written with an assumption that readers are familiar
   with data model and terms defined in Section 3 of [METADATA].

3.  mailbox and mboxmetadata extensions

3.1.  Test mailboxexists

   Usage:  mailboxexists <mailbox-names: string-list>

   The "mailboxexists" test is true if all mailboxes listed in the
   mailbox-names argument exist in the mailstore and each allows the
   user in whose context the Sieve script runs to "deliver" messages
   into it.  When the mailstore is an IMAP server, "delivery" of
   messages is possible if a) the READ-WRITE response code is present
   for the mailbox (see Section 7.1 of [IMAP]) if IMAP ACL [IMAPACL] is
   not supported by the server, or b) the the user has 'p' or 'i' rights
   for the mailbox (see Section 5.2 of [IMAPACL]).

   Note that a successful "mailboxexists" test for a mailbox doesn't
   necessarily mean that a "fileinto" action on this mailbox would
   succeed.  For example the "fileinto" action might put user over
   quota.  The "mailboxexists" only verifies existence of the mailbox
   and whether the user in whose context the Sieve script runs has
   permissions to execute fileinto on it.

   The capability string for use with the require command is "mailbox".

   Example: The following example assumes that the Sieve engine also
   supports "reject" [REJECT] and "fileinto" [SIEVE].  However these
   extensions are not required in order to implement the "mailbox"

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   extension.

        require ["fileinto", "reject", "mailbox"];
        if mailboxexists "Partners" {
           fileinto "Partners";
        } else {
           reject "This message was not accepted by the Mailstore";
        }

3.2.  ':create' argument to 'fileinto' command

   Usage:  fileinto [:create] <mailbox: string>

   If the optional :create argument is specified with "fileinto" it
   instructs the Sieve interpreter to create the specified mailbox, if
   needed, before attempting to deliver the message into the specified
   mailbox.  If the mailbox already exists, this argument is ignored.
   Failure to create the specified mailbox is considered to be an error.

   The capability string for use with the :create parameter is
   "mailbox".

3.3.  Test metadata

   Usage:  metadata [MATCH-TYPE] [COMPARATOR]
           <mailbox: string>
           <annotation-name: string> <key-list: string-list>

   This test retrieves the value of the mailbox annotation "annotation-
   name" for the mailbox "mailbox" [METADATA].  The retrieved value is
   compared to the "key-list".  The test returns true if the annotation
   exists and its value matches any of the keys.

   The default match type is ":is" [SIEVE].  The default comparator is
   "i;ascii-casemap" [SIEVE].

   The capability string for use with the require command is
   "mboxmetadata".

   Annotations MUST be accessed with the permissions of the user in
   whose context the Sieve script runs, and annotations starting with
   the "/private" prefix MUST be those of the user in whose context the
   Sieve script runs.

   Example: The following example assumes that the Sieve engine also
   supports the "vacation" [VACATION] extension.  However this extension
   is not required in order to implement the "mboxmetadata" extension.

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       require ["mboxmetadata", "vacation"];

       if metadata :is "INBOX"
          "/private/vendor/vendor.isode/auto-replies" "on" {

           vacation text:
       I'm away on holidays till March 2009.
       Expect a delay.
       .
       }

3.4.  Test metadataexists

   Usage:  metadataexists <mailbox: string> <annotation-names: string-
           list>

   The "metadataexists" test is true if all of the annotations listed in
   the annotation-names argument exist (i.e., have non-NIL values) for
   the specified mailbox.

   The capability string for use with the require command is
   "mboxmetadata".

4.  servermetadata extension

4.1.  Test servermetadata

   Usage:  servermetadata [MATCH-TYPE] [COMPARATOR]
           <annotation-name: string> <key-list: string-list>

   This test retrieves the value of the server annotation "annotation-
   name" [METADATA].  The retrieved value is compared to the "key-list".
   The test returns true if the annotation exists and its value matches
   any of the keys.

   The default match type is ":is".  The default comparator is "i;ascii-
   casemap".

   The capability string for use with the require command is
   "servermetadata".

   Annotations MUST be accessed with the permissions of the user in
   whose context the Sieve script runs, and annotations starting with
   the "/private" prefix MUST be those of the user in whose context the
   Sieve script runs.

   Example: The following example assumes that the Sieve engine also

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   supports "variables" [VARIABLES] and "enotify" [NOTIFY] and
   "envelope" [SIEVE] extensions.  However these extensions are not
   required in order to implement the "servermetadata" extension.

       require ["enotify", "servermetadata", "variables", "envelope"];

       if servermetadata :matches
          "/private/vendor/vendor.isode/notification-uri" "*" {
           set "notif_uri" "${0}";
       }

       if not string :is "${notif_uri}" "none" {
           # :matches is used to get the MAIL FROM address
           if envelope :all :matches "from" "*" {
               set "env_from" " [really: ${1}]";
           }

           # :matches is used to get the value of the Subject header
           if header :matches "Subject" "*" {
               set "subject" "${1}";
           }

           # :matches is used to get the address from the From header
           if address :matches :all "from" "*" {
               set "from_addr" "${1}";
           }

           notify :message "${from_addr}${env_from}: ${subject}"
                  "${notif_uri}";
       }

4.2.  Test servermetadataexists

   Usage:  servermetadataexists
           <annotation-names: string-list>

   The "servermetadataexists" test is true if all of the server
   annotations listed in the annotation-names argument exist (i.e., have
   non-NIL values).

   The capability string for use with the require command is
   "servermetadata".

5.  Security Considerations

   Extensions defined in this document deliberately don't provide a way
   to modify annotations.

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   A failure to retrieve data due to the server storing the annotations
   being down or otherwise inaccessible may alter the result of Sieve
   processing.  So implementations SHOULD treat a temporary failure to
   retrieve annotations in the same manner as a temporary failure to
   retrieve a Sieve script.

   Protocols/APIs used to retrieve annotations MUST provide the same
   level of confidentiality as protocols/APIs used to retrieve Sieve
   scripts.

6.  IANA Considerations

   IANA is requested to add the following registrations to the list of
   Sieve extensions:

   To: iana@iana.org
   Subject: Registration of new Sieve extension
   Capability name: mailbox
   Description: adds test for checking for mailbox existence and a new
   optional argument to fileinto for creating a mailbox before
   attempting mail delivery.
   RFC number: this RFC
   Contact address:
       The Sieve discussion list <ietf-mta-filters@imc.org>

   Capability name: mboxmetadata
   Description: adds tests for checking for mailbox metadata item
   existence and for retrieving of a mailbox metadata value.
   RFC number: this RFC
   Contact address:
       The Sieve discussion list <ietf-mta-filters@imc.org>

   Capability name: servermetadata
   Description: adds tests for checking for server metadata item
   existence and for retrieving of a server metadata value.
   RFC number: this RFC
   Contact address:
       The Sieve discussion list <ietf-mta-filters@imc.org>

7.  Acknowledgements

   Thanks to Cyrus Daboo for initial motivation for this draft.

   Thanks to Barry Leiba, Randall Gellens and Aaron Stone for helpful
   comments on this document.

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   The author also thanks the Open Mobile Alliance's Mobile Email
   working group for providing a set of requirements for mobile devices,
   guiding some of the extensions in this document.

8.  References

8.1.  Normative References

   [ABNF]     Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 5234, January 2008.

   [IMAP]     Crispin, M., "Internet Message Access Protocol - Version
              4rev1", RFC 3501, March 2003.

   [IMAPACL]  Melnikov, A., "IMAP4 Access Control List (ACL) Extension",
              RFC 4314, December 2005.

   [KEYWORDS]
              Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.

   [METADATA]
              Daboo, C., "IMAP METADATA Extension",
              draft-daboo-imap-annotatemore-17 (work in progress),
              December 2008.

   [SIEVE]    Guenther, P. and T. Showalter, "Sieve: An Email Filtering
              Language", RFC 5228, January 2008.

8.2.  Informative References

   [NOTIFY]   Melnikov, A., Leiba, B., Segmuller, W., and T. Martin,
              "Sieve Extension: Notifications",
              draft-ietf-sieve-notify-12 (work in progress),
              January 2008.

   [REJECT]   Stone, A., "The SIEVE mail filtering language - reject
              extension", draft-ietf-sieve-refuse-reject-09 (work in
              progress), November 2008.

   [VACATION]
              Showalter, T. and N. Freed, "Sieve Email Filtering:
              Vacation Extension", RFC 5230, January 2008.

   [VARIABLES]
              Homme, K., "Sieve: An Email Filtering Language", RFC 5229,
              January 2008.

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Author's Address

   Alexey Melnikov
   Isode Limited
   5 Castle Business Village
   36 Station Road
   Hampton, Middlesex  TW12 2BX
   UK

   Email: Alexey.Melnikov@isode.com

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