Sieve Working Group A. Melnikov, Ed. Internet-Draft Isode Limited Intended status: Standards Track B. Leiba, Ed. Expires: June 2, 2007 W. Segmuller IBM T.J. Watson Research Center T. Martin BeThereBeSquare Inc. November 29, 2006 Sieve Extension: Notifications draft-ietf-sieve-notify-05 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on June 2, 2007. 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 Melnikov, et al. Expires June 2, 2007 [Page 1] Internet-Draft Sieve Extension: Notifications November 2006 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. Changes since draft-ietf-sieve-notify-04 o Made notification method required. o Defined "mailto" as a mandatory-to-implement method. o Added normative reference to mailto. o Clarified that :importance may be treated as a transport indicator. o Clarified that :importance value can be included in the default :message, if one is not specified. o Made the default :message implementation specific. o Renamed the capability name from "notify" to "enotify" o Updated IANA registration. o Moved text about ManageSieve capability to the ManageSieve document itself. o Removed reference to IANA registry for options. o Some miscellaneous text cleanup and clarification. Changes since draft-ietf-sieve-notify-03 o Added a warning that "notify" must not be used as a crappy form of "redirect". o Added a warning about using "notify" to forward confidential information in order to bypass organization's policy. o Fixed syntax of the :options argument - it is a string list, each string containing "=" o Renamed :priority to :importance Melnikov, et al. Expires June 2, 2007 [Page 2] Internet-Draft Sieve Extension: Notifications November 2006 o Cleaned up section about requirements on methods. Changes since draft-ietf-sieve-notify-02 o Added :from tagged argument. o Added Extract_text action, which allows to extract content of the first text/* part. o Added back the ":options" parameter to the notify action. o Added new section talking about requirements on notification method specs. o Added more examples. Changes since draft-ietf-sieve-notify-00 o Updated references, etc. o Added IANA considerations section. o Removed denotify action. o Updated examples to use the variables extension. o Replaced notification method with URI. o Removed text suggesting that this extension can be used to track all Sieve actions taken. o Changed priority to be a string. o Added text about URI verification. o Clarified that a notification method is allowed to perform adaptation of notification context (e.g. truncation, charset conversion, etc.). These adaptations must be documented in a document describing the notification method. o Clarified that notify is compatible with all existing actions. o Removed the :id parameter to the notify action. o Added valid_notif_method test that allows to test if an notification method (URI) is supported. Melnikov, et al. Expires June 2, 2007 [Page 3] Internet-Draft Sieve Extension: Notifications November 2006 o Added a new capability response to ManageSieve that allows to report supported notification types. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Conventions used in this document . . . . . . . . . . . . . 5 2. Capability Identifier . . . . . . . . . . . . . . . . . . . 5 3. Notify Action . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Notify Action Syntax and Semantics . . . . . . . . . . . . . 5 3.2. Notify tag ":method" . . . . . . . . . . . . . . . . . . . . 5 3.3. Notify tag ":from" . . . . . . . . . . . . . . . . . . . . . 6 3.4. Notify tag ":importance" . . . . . . . . . . . . . . . . . . 6 3.5. Notify tag ":options" . . . . . . . . . . . . . . . . . . . 7 3.6. Notify tag ":message" . . . . . . . . . . . . . . . . . . . 7 3.7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.8. Requirements on notification methods specifications . . . . 10 4. Extract_text Action . . . . . . . . . . . . . . . . . . . . 11 5. Test valid_notif_method . . . . . . . . . . . . . . . . . . 12 6. Interactions with Other Sieve Actions . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . 13 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 13 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 10.1. Normative References . . . . . . . . . . . . . . . . . . . . 14 10.2. Informative References . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . 17 Melnikov, et al. Expires June 2, 2007 [Page 4] Internet-Draft Sieve Extension: Notifications November 2006 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 specify the notification methods. Examples of possible notification methods are email and xmpp. To allow a mechanism for portability of scripts that use notifications, implementation of the [MailTo] method is mandatory. Other available methods shall depend upon the implementation and configuration of the system. 1.1. Conventions used in this document Conventions for notations are as in [Sieve] section 1.1, including 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]. 2. Capability Identifier The capability string associated with the extension defined in this document is "enotify". 3. Notify Action 3.1. Notify Action Syntax and Semantics Usage: notify ":method" string [":from" string] [":importance" <"1" / "2" / "3">] [":options" string-list] [":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 Section 3.2). However, all content specified in the :message parameter SHOULD be included. 3.2. Notify tag ":method" The :method tag identifies the notification method that will be used; it is a URI [URI], and this tag and the URI MUST be present. For Melnikov, et al. Expires June 2, 2007 [Page 5] Internet-Draft Sieve Extension: Notifications November 2006 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]. The supported URI values will be site-specific, but support for the [MailTo] method is REQUIRED. If a 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 -- and will treat violations of such semantic restrictions as errors. 3.3. Notify tag ":from" A ":from" parameter may be used to specify an author of the notification. The syntax of this parameter's value is method- specific. Implementations SHOULD check the syntax according to the notification method specification and generate an error when a syntactically invalid ":from" parameter is specified. 3.4. Notify tag ":importance" The :importance tag specifies the importance of the delivery of the notification. The :importance tag is followed by a numeric value represented as a string: "1" (high importance), "2" (normal importance), and "3" (low importance). If no importance is given, the default value "2" SHOULD be assumed. A notification method can treat the importance value as a transport indicator. For example, it might deliver notifications of high importance quicker than notifications of normal or low importance. 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 importance of "3" is not to be sent, however the user should be notified of a notification with higher importance. If the notification method allows users to filter messages based upon certain parameters in the message, users SHOULD be able to filter based upon importance. If the notification method does not support importance, then this parameter MUST be ignored, however an Melnikov, et al. Expires June 2, 2007 [Page 6] Internet-Draft Sieve Extension: Notifications November 2006 implementation MAY include the importance value in the default message Section 3.6, if one is not provided. 3.5. Notify tag ":options" The :options tag is used to send additional parameters to the notification method. Interpretation of the parameters is method- specific. This document doesn't specify any such additional parameter. Each string in the options string list has the following syntax: "=" [[Alexey 3: Should we say something about implementation prefix for implementation specific options? Something like "x-Vendor-zzz". If we don't say it now, it might be too late to say it later.]] 3.6. 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 implementation-specific message is used. Unless specified otherwise by a particular notification mechanism, an implementation default containing at least the value of the "From" header field and the value of the "Subject" header field is RECOMMENDED. 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. 3.7. Examples Melnikov, et al. Expires June 2, 2007 [Page 7] Internet-Draft Sieve Extension: Notifications November 2006 Example 1: require ["enotify", "fileinto", "variables"]; if header :contains "from" "boss@example.org" { notify :method "mailto:alm@example.com" :importance "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 :importance "3" :method "mailto:alm@example.com" :message "[SIEVE] ${from}: ${subject}"; fileinto "INBOX.sieve"; } Melnikov, et al. Expires June 2, 2007 [Page 8] Internet-Draft Sieve Extension: Notifications November 2006 Example 2: require ["enotify", "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" "${1}"; } notify :method "mailto:alm@example.com" :message "${from_addr}${env_from}: ${subject}"; } Melnikov, et al. Expires June 2, 2007 [Page 9] Internet-Draft Sieve Extension: Notifications November 2006 Example 3: require ["enotify", "variables"]; set "notif_method" "xmpp:tim@example.com?You%20got%20mail&subject=SIEVE"; if header :contains "subject" "Your dog" { set "notif_method" "sms:+14085551212"; } if header :contains "to" "sievemailinglist@example.org" { set "notif_method" ""; } if not string :is "${notif_method}" "" { notify :method "${notif_method}"; } if header :contains "from" "boss@example.org" { # :matches is used to get the value of the Subject header if header :matches "Subject" "*" { set "subject" "${1}"; } # don't need high importance notification for # a 'for your information' if not header :contains "subject" "FYI:" { notify :method "sms:+14085551212" :importance "1" :message "BOSS: ${subject}"; } } [[anchor2: Make sure that the XMPP notification syntax is correct.]] 3.8. Requirements on notification methods specifications This section describes requirements for documents that define specific Sieve notification methods. A notification method MAY allow modification of 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. Characters in the notification text which can't be represented by the notification method SHOULD be replaced with a symbol indicating an unknown character. Allowed modifications MUST be documented in the document describing the notification method. Melnikov, et al. Expires June 2, 2007 [Page 10] Internet-Draft Sieve Extension: Notifications November 2006 A notification method MAY ignore parameters specified in the Notify action. A notification method MAY recommend the default message value to be used if the :message argument is not specified. It is RECOMMENDED that a timestamp be included in the notification. Methods SHOULD NOT include extraneous information not specified in parameters to the notify action. If there are errors sending the notification, the Sieve interpreter SHOULD ignore the notification and not retry indefinitely. Documents describing notification methods SHOULD describe how retries, duplicate suppression (if any), etc. are to be handled by implementations. 4. Extract_text Action Usage: extract_text [MODIFIER] [":first" number] The Extract_text action stores at most :first bytes of the first text/* part in the variable identified by varname. If the :first parameter is not present, the whole content of the first text/* part is stored. If the message being processed doesn't contain any text/* part, the action will set the variable identified by varname to the empty string. [[Alexey 5: Do we need to be more specific about what "the first text part" means?]] Modifiers are applied on the extracted text before it is stored in the variable. See [Variables] for details. Note that this action is only available when the Sieve script specifies both "variables" [Variables] and "enotify" capabilities in the require statements. Melnikov, et al. Expires June 2, 2007 [Page 11] Internet-Draft Sieve Extension: Notifications November 2006 Example 4: require ["enotify", "variables"]; if header :contains "from" "boss@example.org" { # :matches is used to get the value of the Subject header if header :matches "Subject" "*" { set "subject" "${1}"; } # extract the first 100 bytes of the first text/* part extract_text :first 100 "msgcontent"; # don't need high importance notification for # a 'for your information' if not header :contains "subject" "FYI:" { notify :method "sms:+14085551212" :importance "1" :message "BOSS: ${subject}; ${msgcontent}"; } } 5. Test valid_notif_method Usage: valid_notif_method 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 (including implementation-specific semantic restrictions) valid. This test MUST perform exactly the same validation as would be performed on the ":method" parameter of the "notify" action. The test is true only if ALL of the listed notification methods are supported and valid. Example 5: if not valid_notif_method ["mailto:", "http://gw.example.net/notify?test"] { stop; } Melnikov, et al. Expires June 2, 2007 [Page 12] Internet-Draft Sieve Extension: Notifications November 2006 6. 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. Specific notification methods MAY allow multiple notifications from the same script to be collapsed into one. 7. 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 that it was sent by the Sieve implementation. It might be possible to forge notifications with some notification methods. An organization may have a policy about the forwarding of classified information to unclassified networks. Unless the policy is also enforced in the module responsible for generating (or sending) of notifications, users can use the extension defined in this document to extract classified information and bypass the policy. Notifications can result in loops and bounces. In particular, a notification to an email address will not contain necessary Received header fields that might be otherwise used to prevent mail loops. All notification methods must take care to provide mechanisms for avoiding notification loops. 8. IANA Considerations The following template specifies the IANA registration of the notify Sieve extension specified in this document: To: iana@iana.org Subject: Registration of new Sieve extension Capability name: enotify Melnikov, et al. Expires June 2, 2007 [Page 13] Internet-Draft Sieve Extension: Notifications November 2006 Description: adds the 'notify' action for notifying user about the received message; also adds the 'extract_text' action for extracting a part of the first textual bodypart. RFC number: this RFC Contact address: The Sieve discussion list This information should be added to the list of sieve extensions given on http://www.iana.org/assignments/sieve-extensions. 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. 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. [MailTo] Leiba, B. and M. Haardt, "Sieve Notification Mechanism: mailto", work in progress, draft-ietf-sieve-notify-mailto, October 2006. [Sieve] Guenther, P. and T. Showalter, "Sieve: An Email Filtering Language", work in progress, draft-ietf-sieve-3028bis, August 2006. [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [Variables] Homme, K., "Sieve Extension: Variables", work in progress, draft-ietf-sieve-variables, December 2005. 10.2. Informative References [SMS-URI] Wilde, E. and A. Vaha-Sipila, "URI scheme for GSM Short Message Service", work in progress, draft-wilde-sms-uri, Melnikov, et al. Expires June 2, 2007 [Page 14] Internet-Draft Sieve Extension: Notifications November 2006 August 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. 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 Melnikov, et al. Expires June 2, 2007 [Page 15] Internet-Draft Sieve Extension: Notifications November 2006 Tim Martin BeThereBeSquare Inc. 672 Haight st. San Francisco, CA 94117 US Phone: +1 510 260-4175 Email: timmartin@alumni.cmu.edu Melnikov, et al. Expires June 2, 2007 [Page 16] Internet-Draft Sieve Extension: Notifications November 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM 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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