Sieve Working Group A. Melnikov, Ed.
Internet-Draft Isode Limited
Expires: August 8, 2006 B. Leiba, Ed.
W. Segmuller
IBM T.J. Watson Research Center
T. Martin
Mirapoint Inc.
February 4, 2006
Sieve Extension: Notifications
draft-ietf-sieve-notify-02
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
Users go to great lengths to be notified as quickly as possible that
they have received new mail. Most of these methods involve polling
to check for new messages periodically. A push method handled by the
final delivery agent gives users quicker notifications and saves
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server resources. This document does not specify the notification
method but is expected that using existing instant messaging
infrastructure such as Zephyr, Jabber, or SMS messages will be
popular. This draft describes an extension to the Sieve mail
filtering language that allows users to give specific rules for how
and when notifications should be sent.
Note
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Conventions used in this document . . . . . . . . . . . . . 3
2. Capability Identifier . . . . . . . . . . . . . . . . . . . 4
3. Notify Action . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Notify Action Syntax and Semantics . . . . . . . . . . . . . 5
3.2 Notify tag ":method" . . . . . . . . . . . . . . . . . . . . 5
3.3 Notify tag ":priority" . . . . . . . . . . . . . . . . . . . 6
3.4 Notify tag ":message" . . . . . . . . . . . . . . . . . . . 6
3.5 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. Test valid_notif_method . . . . . . . . . . . . . . . . . . 9
5. Interactions with Other Sieve Actions . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . 11
7. Extensions to ManageSieve protocol . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
10.1 Normative References . . . . . . . . . . . . . . . . . . . . 15
10.2 Non-Normative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16
Intellectual Property and Copyright Statements . . . . . . . 17
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1. Introduction
This is an extension to the Sieve language defined by [Sieve] for
providing instant notifications. It defines the new action "notify".
This document does not dictate the notification method used.
Examples of possible notification methods are Zephyr and Jabber. The
available methods shall be site-defined.
1.1 Conventions used in this document
Conventions for notations are as in [Sieve] section 1.1, including
the use of [Kwds] and the use of [ABNF].
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 [Kwds].
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2. Capability Identifier
The capability string associated with the extension defined in this
document is "notify".
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3. Notify Action
3.1 Notify Action Syntax and Semantics
Usage: notify [":method" string]
[":priority" <"1" / "2" / "3">]
[":message" string]
The Notify action specifies that a notification should be sent to the
user. The format of the notification is implementation-defined and
is also affected by the notification method used (see below).
However, all content specified in the notify action SHOULD be
included. It is RECOMMENDED that a timestamp be included in the
notification. Implementations SHOULD NOT include extraneous
information.
If there are errors sending the notification, the Sieve interpreter
SHOULD ignore the notification and not retry indefinitely.
[[Barry 4: Does this really belong here? Shouldn't we push the
question of error recovery to the individual methods?]]
3.2 Notify tag ":method"
The :method tag identifies the notification method that will be used;
it is a URI. For example, the notification method can be an SMS URI
[SMS-URI] containing a phone number, or an XMPP [XMPP] URI containing
a Jabber identifier [XMPP-URI]. If the :method tag is not specified,
a default implementation-defined notification method is used, and if
there is no default method defined, the notification is ignored.
Implementations MUST NOT generate an error condition for lack of a
default notification method, and execution of the script MUST
continue.
The supported URI values will be site-specific. If an URI schema is
specified that the implementation does not support, the notification
MUST cause an error condition. Sieve scripts can check the supported
methods using the "valid_notif_method" test to be sure that they only
use supported ones, to avoid such error conditions. If the :method
tag contains a supported URI schema, then the URI MUST be checked for
syntactic validity. An invalid URI syntax or an unsupported URI
extension MUST cause an error. An implementation MAY enforce other
semantic restrictions on URIs -- for example an SMS URI can only
contain phone numbers in a particular geographical region. Violation
of such semantic restrictions MUST also cause an error.
[[Barry 1: "MUST" seems silly here, since the whole sentence is a
"MAY".]]
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3.3 Notify tag ":priority"
The :priority tag specifies the importance of the notification. The
:priority tag is followed by a numeric value represented as a string:
"1" (high importance), "2" (normal importance), and "3" (low
importance). If no priority is given, a default priority of "2"
SHOULD be assumed. Some notification methods allow users to specify
their state of activity (for example "busy" or "away from keyboard").
If the notification method provides this information it SHOULD be
used to selectively send notifications. If, for example, the user
marks herself as "busy", a notification method can require that a
notification with a priority of "3" is not to be sent, however the
user should be notified of a higher priority notifications. If the
notification method allows users to filter messages based upon
certain parameters in the message, users SHOULD be able to filter
based upon priority. If the notification method does not support
priority, then this parameter MUST be ignored.
[[Alexey 1: Should we keep using "high", "normal" and "low"
instead?]]
[[Barry 3.5: Why do we call this "priority", and then explain it as
"importance"? Shouldn't we just call it "importance"?]]
3.4 Notify tag ":message"
The :message tag specifies the message data to be included in the
notification. The entirety of the string SHOULD be sent but
implementations MAY shorten the message for technical or aesthetic
reasons. If the message parameter is absent, a default message
containing the value of the From header field and the value of the
Subject header field will be used. Note that the notification method
(the ":method" tag) may affect how this information is formatted.
The implementation of a notification method MAY modify the final
notification text -- for example, truncating it if it exceeds a
length limit, or modifying characters that can not be represented in
the target character set. Allowed modifications should be documented
in a standards-track or informational document.
In order to construct more complex messages the notify extension can
be used together with the Sieve variables extension [Variables], as
shown in the examples below.
[[Note 2: Open issue:]] The previous version of this draft has
defined the two variables that can't be currently represented:
$text$ - the first text/* part
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$text[n]$ - the first n bytes of the first text/* part
3.5 Examples
Example 1:
require ["notify", "fileinto", "variables"];
if header :contains "from" "boss@example.org" {
notify :priority "1"
:message "This is probably very important";
# Don't send any further notifications
stop;
}
if header :contains "to" "sievemailinglist@example.org" {
# :matches is used to get the value of the Subject header
if header :matches "Subject" "*" {
set "subject" "${1}";
}
# :matches is used to get the value of the From header
if header :matches "From" "*" {
set "from" "${1}";
}
notify :priority "3"
:message "[SIEVE] ${from}: ${subject}";
fileinto "INBOX.sieve";
}
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Example 2:
require ["notify", "fileinto", "variables", "envelope"];
if header :matches "from" "*@*.example.org" {
# :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}";
}
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4. Test valid_notif_method
Usage: valid_notif_method <notification-uris: string-list>
The "valid_notif_method" test is true if the notification methods
listed in the notification-uris argument are supported and they are
syntactically and semantically valid. All of the notification
methods must be supported and valid or the test is false.
[[Alexey 2: The text must be clear that this test performs exactly
the same checks as done during notify :method parameter
verificiation.]]
Example: if valid_notif_method ["mailto:",
"http://gw.example.net/notify?test"] {
stop;
}
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5. Interactions with Other Sieve Actions
The notify action is compatible with all other actions, and does not
affect the operation of other actions. In particular, the notify
action MUST NOT cancel the implicit keep.
Multiple executed notify actions are allowed.
[[Note 3: Add text about suppression of identical notifications.]]
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6. Security Considerations
Security considerations are discussed in [Sieve]. Additionally,
implementations must be careful to follow the security considerations
of the specific notification methods.
The notify action is potentially very dangerous. The path the
notification takes through the network may not be secure. An error
in the options string may cause the message to be transmitted to
someone it was not intended for, or may expose information to
eavesdroppers.
Just because a notification is received doesn't mean it was sent by
the Sieve implementation. It might be possible to forge
notifications with some notification methods.
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7. Extensions to ManageSieve protocol
A ManageSieve [ManageSieve] server that supports the "notify"
extension MUST advertise the NOTIFY capability, that has a single
mandatory parameter. The parameter is a string containing space
separated list of URI schema parts for supported nofication methods.
Example:
S: "NOTIFY" "xmpp mailto"
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8. IANA Considerations
The following template specifies the IANA registration of the
variables Sieve extension specified in this document:
To: iana@iana.org
Subject: Registration of new Sieve extension
Capability name: notify
Capability keyword: notify
Capability arguments: N/A
Standards Track/IESG-approved experimental RFC number: this RFC
Person and email address to contact for further information:
Alexey Melnikov <Alexey.Melnikov@isode.com>
This information should be added to the list of sieve extensions
given on http://www.iana.org/assignments/sieve-extensions.
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9. Acknowledgements
Thanks to Larry Greenfield, Sarah Robeson, Tim Showalter, Cyrus
Daboo, Nigel Swinson, Kjetil Torgrim Homme, Michael Haardt, Mark E.
Mallett and Ned Freed for help with this document.
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10. References
10.1 Normative References
[ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005.
[Kwds] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[ManageSieve]
Martin, T. and A. Melnikov, "A Protocol for Remotely
Managing Sieve Scripts", work in
progress, draft-martin-managesieve, February 2006.
[Sieve] Guenther, P. and T. Showalter, "Sieve: An Email Filtering
Language", work in progress, draft-ietf-sieve-3028bis,
July 2005.
10.2 Non-Normative References
[SMS-URI] Wilde, E. and A. Vaha-Sipila, "URI scheme for GSM Short
Message Service", work in progress, draft-wilde-sms-uri,
August 2005.
[Variables]
Homme, K., "Sieve Extension: Variables", work in
progress, draft-ietf-sieve-variables, October 2005.
[XMPP] Saint-Andre, Ed., P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[XMPP-URI]
Saint-Andre, P., "Internationalized Resource Identifiers
(IRIs) and Uniform Resource Identifiers (URIs) for the
Extensible Messaging and Presence Protocol (XMPP)", work
in progress, draft-saintandre-xmpp-iri, September 2005.
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Authors' Addresses
Alexey Melnikov (editor)
Isode Limited
5 Castle Business Village
36 Station Road
Hampton, Middlesex TW12 2BX
UK
Email: Alexey.Melnikov@isode.com
Barry Leiba (editor)
IBM T.J. Watson Research Center
19 Skyline Drive
Hawthorne, NY 10532
US
Phone: +1 914 784 7941
Email: leiba@watson.ibm.com
Wolfgang Segmuller
IBM T.J. Watson Research Center
19 Skyline Drive
Hawthorne, NY 10532
US
Phone: +1 914 784 7408
Email: werewolf@us.ibm.com
Tim Martin
Mirapoint Inc.
909 Hermosa Court
Sunnyvale, CA 94085
US
Phone: +1 409 720 3835
Email: tmartin@mirapoint.com
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