Network Working Group                                          C. Daboo
Internet Draft: SIEVE Include Extension
Document: draft-daboo-sieve-include-01.txt                 October 2003

                        SIEVE Include Extension

Status of this Memo

    This document is an Internet-Draft and is in full conformance with
    all provisions of Section 10 of RFC2026.

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Copyright Notice

     Copyright (C) The Internet Society 2003. All Rights Reserved.


























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Internet Draft           SIEVE Include Extension           October 2003

    Abstract

    The SIEVE [SIEVE] "include" extension permits users to include one
    SIEVE script inside another.  This can make managing large scripts
    or multiple sets of scripts much easier, as well as supporting
    common 'libraries' of scripts.  Users are able to include their own
    personal scripts or site-wide scripts provided by the local SIEVE
    implementation.

Change History (to be removed prior to publication as an RFC)

    Changes from -00 to -01:
    1   Added IPR boiler plate.
    2   Re-ordered sections at start to conform to RFC style.
    3   Moved recursion comment into General Considerations section.
    4   Switched to using optional parameter to indicate personal vs
        global.
    5   Explicitly state that an error occurs when a missing script is
        included.


                           Table of Contents
     1  Introduction and Overview . . . . . . . . . . . . . . . . . .  2
     2  Conventions Used in This Document  . . . . . . . . . . . . . . 2
     3  SIEVE Include Extension . . . . . . . . . . . . . . . . . . .  3
       3.1  General Considerations . . . . . . . . . . . . . . . . . . 3
       3.2  Control Structure Include . . . . . . . . . . . . . . . .  3
       3.3  Control Structure Return . . . . . . . . . . . . . . . . . 6
     4  Security Considerations . . . . . . . . . . . . . . . . . . .  7
     5  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 7
       5.1  include registration  . . . . . . . . . . . . . . . . . .  7
     6  Normative References . . . . . . . . . . . . . . . . . . . . . 7
     7  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  7
     8  Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
     9  Intellectual Property Rights Statement  . . . . . . . . . . .  8
    10  Full Copyright Statement . . . . . . . . . . . . . . . . . . . 8

1 Introduction and Overview

    Its convenient to be able to break SIEVE scripts down into smaller
    components which can be reused in a variety of different
    circumstances.  For example, users may want to have a default script
    and a special 'vacation' script, the later being activated when the
    user goes on vacation.  In that case the default actions should
    continue to be run, but a vacation command should be executed first.
    One option is to edit the default script to add or remove the
    vacation command as needed.  Another is to have a vacation script
    that simply has a vacation command and then includes the default
    script.





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2 Conventions Used in This Document

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

3 SIEVE Include Extension

3.1 General Considerations

    SIEVE implementations that implement the "include" and "return"
    control structures described below have an identifier of "include"
    for use with the capability mechanism.  If either of the "include"
    or "return" control structures are used in a script, the "include"
    capability MUST be listed in the "require" statement in that script.

    SIEVE implementations must track the use of actions in included
    scripts so that implicit "keep" behaviour can be properly determined
    based on whether any actions have executed in any script.

    SIEVE implementations are allowed to limit the total number of
    nested included scripts, but MUST provide for a total of at least
    three levels of nested scripts including the top-level script.  An
    error MUST be generated either when the script is uploaded to the
    SIEVE repository, or when the script is executed, if any nesting
    limit is exceeded.  If such an error is detected whilst processing a
    SIEVE script, an implicit "keep" action MUST be executed to prevent
    loss of any messages.

    SIEVE implementations MUST ensure that recursive includes are not
    possible. i.e. if script "A" includes script "B", and script "B"
    includes script "A" an error MUST be generated either when the
    script is uploaded to the SIEVE repository, or when the script is
    executed.  If such an error is detected whilst processing a SIEVE
    script, an implicit "keep" action MUST be executed to prevent loss
    of any messages.

    SIEVE implementations MUST handle missing scripts being referenced
    via an includes in an existing script.  An error MUST be generated
    when a missing included script is descovered during execution.  If
    such an error is detected an implicit "keep" action MUST be executed
    to prevent loss of any messages.

3.2 Control Structure Include

        Syntax: include [LOCATION] <value: string>

    The "include" control structure includes an optional parameter, and
    a single string argument representing the name of the script to
    include in the main script at that point.





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    [LOCATION] is an optional parameter that has one of two values:

   Syntax:
          ":personal"
        / ":global"

   If the [LOCATION] parameter is not present, the location defaults to :personal.

    The location has the following meanings:

        :personal
            Indicates that the named script is stored in the user's own
            personal (private) SIEVE repository.

        :global
            Indicates that the named script is stored in a site-wide
            SIEVE repository, accessible to all users of the SIEVE
            system.

    The included script MUST be a valid SIEVE script, including having
    necessary "require" statements for all optional capabilities used by
    the script.  The scope of a "require" statement in an included
    script is for that script only, not the including script. e.g. if
    script "A" includes script "B", and script "B" uses the "fileinto"
    extension, script "B" must have a "require" statement for
    "fileinto", irrespective of whether script "A" has one.  In
    addition, if script "A" does not have a "require" statement for
    "fileinto", "fileinto" cannot be used anywhere in script "A", even
    after inclusion of script "B".

    A "stop" control statement in an included script MUST stop all
    script processing, including the processing of the scripts that
    include the current one.  The "return" control statement (described
    below) stops processing of the current script only, and allows the
    scripts that include it to continue.

    Examples:

    In the examples below, script content is indicated by a '|' as the
    first non-space character on a line for clarity.  The '|' characters
    are not part of the script itself.

    The user has four scripts stored in their personal repository:











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        "default"

        This is the default active script that includes several others.

                |   require ["include"];
            |
                |   include :personal "always_allow";
                |   include :global "spam_tests";
                |   include :personal "my_spam_tests";
                |   include :personal "mailing_lists";

        "always_allow"

        This script special cases some correspondent email addresses and
        makes sure any message containing those addresses are always
        kept.

                |   if header :is "From" "boss@example.com"
                |   {
                |       keep;
                |   }
                |   elsif header :is "From" "ceo@example.com"
                |   {
                |       keep;
                |   }

        "my_spam_tests"

        This script does some user-specific spam tests to catch spam
        messages not caught by the site-wide spam tests.

                |   require ["reject"];
            |
                |   if header :contains "Subject" "XXXX"
                |   {
                |       reject;
                |   }
                |   elsif header :is "From" "money@example.com"
                |   {
                |       reject;
                |   }













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        "mailing_lists"

        This script looks for messages from different mailing lists and
        files each into a mailbox specific to the mailing list.

                |   require ["fileinto"];
            |
                |   if header :is "Sender" "owner-ietf-mta-filters@imc.org"
                |   {
                |       fileinto "lists.sieve";
                |   }
                |   elsif header :is "Sender" "owner-ietf-imapext@imc.org"
                |   {
                |       fileinto "lists.imapext";
                |   }

    There is one script stored in the global repository:

        "spam_tests"

        This script does some site-wide spam tests which any user at the
        site can include in their own scripts at a suitable point.  The
        script content is kept up to date by the site administrator.

                |   require ["reject"];
            |
                |   if anyof (header :contains "Subject" "$$",
                |                 header :contains "Subject" "Make money")
                |   {
                |       reject;
                |   }

    The "include" control structure may appear anywhere in the script
    where a control structure is legal.

    Example:

                |   require ["include"];
            |
                |   if anyof (header :contains "Subject" "$$",
                |                 header :contains "Subject" "Make money")
                |   {
                |       include "my_reject_script";
                |   }

3.3 Control Structure Return

        Syntax: return

    The "return" control structure stops processing of the currently
    included script only and returns processing control to the script
    which includes it.  If used in the main script (i.e. not in an


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    included script), it has the same effect as the "stop" control
    structure, including the appropriate "keep" action if no other
    actions have been executed up to that point.

4 Security Considerations

    SIEVE implementations MUST ensure adequate security for the global
    script repository to prevent unauthorized changes to global scripts.

    Beyond that, the "include" extension does not raise any security
    considerations that are not present in the base [SIEVE] protocol,
    and these issues are discussed in [SIEVE].


5 IANA Considerations

    The following template specifies the IANA registration of the Sieve
    extension specified in this document:

5.1 include registration

    To: iana@iana.org
    Subject: Registration of new Sieve extension

    Capability name: include
    Capability keyword: include
    Capability arguments: N/A
    Standards Track/IESG-approved experimental RFC number: this RFC
    Person and email address to contact for further information:

      Cyrus Daboo
      Cyrusoft International, Inc.
      5001 Baum Blvd., Suite 780,
      Pittsburgh, PA 15213
      U.S.A.

      <mailto:daboo@cyrusoft.com>

    This information should be added to the list of sieve extensions
    given on http://www.iana.org/assignments/sieve-extensions.


6 Normative References

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

    [SIEVE] Showalter, "Sieve:  A Mail Filtering Language", RFC 3028,
    January 2001.





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7 Acknowledgments

    Thanks to Ken Murchison, Rob Siemborski, Alexey Melnikov, Marc Mutz
    and Kjetil Torgrim Homme for comments and corrections.


8 Author's Address

    Cyrus Daboo
    Cyrusoft International, Inc.
    5001 Baum Blvd., Suite 780,
    Pittsburgh, PA 15213
    U.S.A.

    <mailto:daboo@cyrusoft.com>

9 Intellectual Property Rights Statement

    The IETF takes no position regarding the validity or scope of any
    intellectual property or other rights that might be claimed to
    pertain to the implementation or use of the technology described in
    this document or the extent to which any license under such rights
    might or might not be available; neither does it represent that it
    has made any effort to identify any such rights.  Information on the
    IETF's procedures with respect to rights in standards-track and
    standards-related documentation can be found in BCP-11.  Copies of
    claims of rights made available for publication and any assurances
    of licenses to be made available, or the result of an attempt made
    to obtain a general license or permission for the use of such
    proprietary rights by implementors or users of this specification
    can be obtained from the IETF Secretariat.


10 Full Copyright Statement

    Copyright (C) The Internet Society 2003.  All Rights Reserved.

    This document and translations of it may be copied and furnished to
    others, and derivative works that comment on or otherwise explain it
    or assist in its implementation may be prepared, copied, published
    and distributed, in whole or in part, without restriction of any
    kind, provided that the above copyright notice and this paragraph
    are included on all such copies and derivative works.  However, this
    document itself may not be modified in any way, such as by removing
    the copyright notice or references to the Internet Society or other
    Internet organizations, except as needed for the purpose of
    developing Internet standards in which case the procedures for
    copyrights defined in the Internet Standards process must be
    followed, or as required to translate it into languages other than
    English.




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    The limited permissions granted above are perpetual and will not be
    revoked by the Internet Society or its successors or assigns.

    This document and the information contained herein is provided on an
    "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
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