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
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Copyright Notice
Copyright (C) The Internet Society 2003. All Rights Reserved.
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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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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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"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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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
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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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the copyright notice or references to the Internet Society or other
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The limited permissions granted above are perpetual and will not be
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