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Network Working Group                                         J. DegenerRequest for Comments: 3894                                Sendmail, Inc.Category: Standards Track                                   October 2004Sieve Extension: Copying Without Side EffectsStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2004).Abstract   The Sieve scripting language allows users to control handling and   disposal of their incoming e-mail.  By default, an e-mail message   that is processed by a Sieve script is saved in the owner's "inbox".   Actions such as "fileinto" and "redirect" cancel this default   behavior.   This document defines a new keyword parameter, ":copy", to be used   with the Sieve "fileinto" and "redirect" actions.  Adding ":copy" to   an action suppresses cancellation of the default "inbox" save.  It   allows users to add commands to an existing script without changing   the meaning of the rest of the script.1.  Introduction   The Sieve scripting language [SIEVE] allows users to control handling   and disposal of their incoming e-mail.  Two frequently used Sieve   commands are "fileinto" (saving into a local message store, such as   an IMAP server) and "redirect" (forwarding to another e-mail   address).  Both of these cancel the Sieve default behavior of saving   into the user's "inbox".   But some users have the notion of forwarding an extra copy of a   message for safekeeping to another e-mail address, or of saving a   copy in a folder - in addition to the regular message delivery, which   shouldn't be affected by the copy.Degener                     Standards Track                     [Page 1]

RFC 3894      Sieve Extension - Copy Without Side Effects   October 2004   If saving an extra copy is all the user wanted to do,      fileinto "unfiltered";      keep;   would do the job.  The "keep" command does explicitly what the   cancelled default behavior did.  But the explicit "keep" is a poor   substitute for the implicit "keep" when more processing follows:      fileinto "unfiltered";      keep;      if header "Subject" "MAKE MONEY FAST!!!"      {              discard;      }   In this example, the "discard" is ineffective against the explicit   "keep"; the discarded message still ends up in the user's inbox.   It is possible to generate Sieve code that perfectly expresses a   user's wishes, but such code quickly grows unwieldy because it needs   to keep track of the state that the implicit "keep" would have had   without the "fileinto" or "redirect" command.   This extension tries to make life easier for user interface designers   and script writers by allowing them to express the "copy" semantics   directly.2.  Conventions used   Conventions for notations are as in [SIEVE]section 1.1, including   use of [KEYWORDS] and "Syntax:" label for the definition of action   and tagged arguments syntax.   The capability string associated with extension defined in this   document is "copy".3.  ":copy" extension to the "fileinto" and "redirect" commands   Syntax:        "fileinto" [":copy"] <folder: string>        "redirect" [":copy"] <address: string>   If the optional ":copy" keyword is specified with "fileinto" or   "redirect", the tagged command does not cancel the implicit "keep".   Instead, it merely files or redirects a copy in addition to whatever   else is happening to the message.Degener                     Standards Track                     [Page 2]

RFC 3894      Sieve Extension - Copy Without Side Effects   October 2004   Example:      require ["copy", "fileinto"];      fileinto :copy "incoming";      # ... more processing follows ...4.  Security Considerations   The "copy" extension makes it easier to eavesdrop on a user's message   stream without the user noticing.  This was technically possible   before if an attacker gained read/write access to a user's Sieve   scripts, but now an attacker no longer needs to parse a script in   order to modify it.  Write access to Sieve scripts must be protected   as strongly as read/write access to e-mail, for example by using   secure directory protocols such as correctly parameterized LDAP over   TLS [LDAP].   Organizations that wish to monitor their users' e-mail traffic must   familiarize themselves with local data protection laws before   creating stores of old e-mail traffic without control, or perhaps   even knowledge, of the sender or intended recipients.   Organizations that legally use "redirect :copy" to eavesdrop on   correspondence (for example, by keeping a log to answer questions   about insider trading at a later time) can avoid future problems by   setting users' privacy expectations correctly.5.  IANA Considerations   The following template specifies the IANA registration of the "copy"   Sieve extension specified in this document.   To: iana@iana.org   Subject: Registration of new Sieve extension   Capability name: copy   Capability keyword: copy   Capability arguments: N/A   Standards Track:RFC 3894   Person and email address to contact for further information:      Jutta Degener      Sendmail, Inc.      6425 Christie Ave, 4th Floor      Emeryville, CA 94608      Email: jutta@sendmail.comDegener                     Standards Track                     [Page 3]

RFC 3894      Sieve Extension - Copy Without Side Effects   October 2004   This information has been added to the list of Sieve extensions given   onhttp://www.iana.org/assignments/sieve-extensions.6.  Acknowledgments   Thanks to Eric Allman, Ned Freed, Will Lee, Nigel Swinson, and Rand   Wacker for corrections and comments.7.  References7.1.  Normative References   [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [SIEVE]    Showalter, T., "Sieve: A Mail Filtering Language",RFC3028, January 2001.7.2.  Informative References   [LDAP]     Wahl, M., Alvestrand, H., Hodges, J., and R. Morgan,              "Authentication Methods for LDAP",RFC 2829, May 2000.Author's Address   Jutta Degener   Sendmail, Inc.   6425 Christie Ave, 4th Floor   Emeryville, CA 94608   EMail: jutta@sendmail.comDegener                     Standards Track                     [Page 4]

RFC 3894      Sieve Extension - Copy Without Side Effects   October 2004Full Copyright Statement   Copyright (C) The Internet Society (2004).   This document is subject to the rights, licenses and restrictions   contained inBCP 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/S HE   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.Intellectual Property   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 IETF's procedures with respect to rights in IETF Documents can   be found inBCP 78 andBCP 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 athttp://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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Degener                     Standards Track                     [Page 5]