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 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 January 15, 2005. Copyright Notice 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: Daboo Expires January 15, 2005 [Page 1] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 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 Daboo Expires January 15, 2005 [Page 2] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 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. Daboo Expires January 15, 2005 [Page 3] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 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] 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 Daboo Expires January 15, 2005 [Page 4] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 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" | { Daboo Expires January 15, 2005 [Page 5] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 | 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"; | } Daboo Expires January 15, 2005 [Page 6] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 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. 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 Daboo Expires January 15, 2005 [Page 7] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 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. Daboo Expires January 15, 2005 [Page 8] Internet-Draft SIEVE Email Filtering: Include Extension July 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity 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. Copyright Statement Copyright (C) The Internet Society (2004). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Daboo Expires January 15, 2005 [Page 9]