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Network Working Group                                          C. Daboo
Internet Draft: SIEVE Include Extension
Document: draft-daboo-sieve-include-00.txt                   April 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.

    Internet-Drafts are working documents of the Internet Engineering
    Task Force (IETF), its areas, and its working groups.  Note that
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Copyright Notice

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


























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Internet Draft            SIEVE Include Extension            April 2003

                           Table of Contents
     1  Abstract  . . . . . . . . . . . . . . . . . . . . . . . . . .  2
     2  Conventions Used in This Document  . . . . . . . . . . . . . . 2
     3  Change History  . . . . . . . . . . . . . . . . . . . . . . .  2
     4  Open Issues: . . . . . . . . . . . . . . . . . . . . . . . . . 2
     5  Introduction and Overview . . . . . . . . . . . . . . . . . .  2
     6  SIEVE Include Extension  . . . . . . . . . . . . . . . . . . . 3
       6.1  General Considerations  . . . . . . . . . . . . . . . . .  3
       6.2  Control Structure Include  . . . . . . . . . . . . . . . . 3
       6.3  Control Structure Return  . . . . . . . . . . . . . . . .  6
     7  Security Considerations  . . . . . . . . . . . . . . . . . . . 6
     8  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  6
       8.1  include registration . . . . . . . . . . . . . . . . . . . 6
     9  Normative References  . . . . . . . . . . . . . . . . . . . .  7
    10  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 7
    11  Author's Address  . . . . . . . . . . . . . . . . . . . . . .  7
    12  Full Copyright Statement . . . . . . . . . . . . . . . . . . . 7

1 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.

2 Conventions Used in This Document

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

3 Change History

    Initial Document


4 Open Issues:

    1   Should we allow URIs to point to scripts to include?
    2   Should we allow string lists as argument to include?
    3   How should non-exist include scripts be handled?
    4   Interaction with variables?

5 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.


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Internet Draft            SIEVE Include Extension            April 2003

    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.

6 SIEVE Include Extension

6.1 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.


6.2 Control Structure Include

        Syntax: include <value: string>

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

    The script name contains one of two prefixes:

        "/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 second component of the name represents an implementation
    dependent script name.




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    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 example 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:

        "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;
                |   }




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Internet Draft            SIEVE Include Extension            April 2003

        "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;
                |   }

        "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.




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    Example:

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

6.3 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
    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.

7 Security Considerations

    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 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].


8 IANA Considerations

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

8.1 include registration

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

    Capability name: include
    Capability keyword: include
    Capability arguments: N/A


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Internet Draft            SIEVE Include Extension            April 2003

    Standards Track/IESG-approved experimental RFC number: this RFC
    Person and email address to contact for further information:

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

      Email: daboo@cyrusoft.com

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


9 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.


10 Acknowledgments

    Thanks to Ken Murchison and Rob Siemborski for comments and
    suggestions.



11 Author's Address

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

    Email: daboo@cyrusoft.com

12 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


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Internet Draft            SIEVE Include Extension            April 2003

    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.

    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
    TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
    BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
    HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
    MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.






































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