Network Working Group C. Daboo
Internet-Draft ISAMET, Inc.
Expires: January 15, 2005 July 17, 2004
SIEVE Email Filtering: Include Extension
draft-daboo-sieve-include-02
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Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
The SIEVE Email Filtering "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 -01 to -02:
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a. Minor formatting changes only - refreshing expired draft.
Changes from -00 to -01:
a. Added IPR boiler plate.
b. Re-ordered sections at start to conform to RFC style.
c. Moved recursion comment into General Considerations section.
d. Switched to using optional parameter to indicate personal vs
global.
e. Explicitly state that an error occurs when a missing script is
included.
Table of Contents
1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. SIEVE Include Extension . . . . . . . . . . . . . . . . . . . 3
3.1 General Considerations . . . . . . . . . . . . . . . . . . 3
3.2 Control Structure Include . . . . . . . . . . . . . . . . 4
3.3 Control Structure Return . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5.1 include registration . . . . . . . . . . . . . . . . . . . 7
6. Normative References . . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
A. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . 9
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1. Introduction and Overview
Its convenient to be able to break SIEVE [RFC3028] 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.
2. Conventions Used in This Document
Conventions for notations are as in [RFC3028] section 1.1, including
use of [RFC2119].
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.
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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.
[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
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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:
"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"
| {
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| 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" "$$",
| header :contains "Subject" "Make money")
| {
| reject;
| }
The "include" control structure may appear anywhere in the script
where a control structure is legal.
Example:
| require ["include"];
|
| if anyof (header :contains "Subject" "$$",
| header :contains "Subject" "Make money")
| {
| include "my_reject_script";
| }
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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
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
ISAMET, Inc.
5001 Baum Blvd., Suite 650,
Pittsburgh, PA 15213
U.S.A.
<mailto:daboo@isamet.com>
This information should be added to the list of sieve extensions
given on http://www.iana.org/assignments/sieve-extensions.
This information should be added to the list of sieve extensions
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given on http://www.iana.org/assignments/sieve-extensions.
6 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3028] Showalter, T., "Sieve: A Mail Filtering Language", RFC
3028, January 2001.
Author's Address
Cyrus Daboo
ISAMET, Inc.
5001 Baum Blvd.
Suite 650
Pittsburgh, PA 15213
US
EMail: daboo@isamet.com
Appendix A. Acknowledgments
Thanks to Ken Murchison, Rob Siemborski, Alexey Melnikov, Marc Mutz
and Kjetil Torgrim Homme for comments and corrections.
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