LEMONADE P. Resnick Internet-Draft QUALCOMM Incorporated Expires: August 20, 2005 February 16, 2005 Internet Message Access Protocol (IMAP) CATENATE Extension draft-ietf-lemonade-catenate-04 Status of this Memo This document is an Internet-Draft and is subject to all provisions of Section 3 of RFC 3667. 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 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 August 20, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The CATENATE extension to the Internet Message Access Protocol (IMAP) modifies the APPEND command to allow clients to create messages on the IMAP server which may contain a combination of new data along with parts of (or entire) messages already on the server. Using this extension, the client can catenate parts of an already existing message on to a new message without having to first download the data and then upload it back to the server. Resnick Expires August 20, 2005 [Page 1] Internet-Draft IMAP CATENATE Extension February 2005 1. Introduction The CATENATE extension to the Internet Message Access Protocol (IMAP) [1] allows the client to create a message on the server which can include the text of messages (or parts of messages) that already exist on the server without having to FETCH them and APPEND them back to the server. The CATENATE extension modifies the APPEND command so that, instead of a single message literal, the command can take as arguments any combination of message literals (as described in IMAP [1]) and message URLs (as described in the IMAP URL Scheme [2] specification). The server takes all of the pieces and catenates them into the output message. The CATENATE extension can also co-exist with the MULTIAPPEND extension [3] to append multiple messages in a single command. There are some obvious uses for the CATENATE extension. The motivating use case was to provide a way for a resource-constrained client to compose a message for subsequent submission which contains data that already exists in that client's IMAP store. Because the client does not have to download and re-upload potentially large message parts, bandwidth and processing limitations do not have as much impact. In addition, since the client can create a message in the its own IMAP store, the command also addresses the desire of the client to archive a copy of a sent message without having to upload the message twice. (Mechanisms for sending the message are outside of the scope of this document.) The new APPEND command can also be used to copy parts of a message to another mailbox for archival purposes while getting rid of undesired parts. In environments where server storage is limited, a client could get rid of large message parts by copying over only the necessary parts and then deleting the original message. The mechanism could also be used to add data to a message such as prepending message header fields or including other data by making a copy of the original and catenating the new data. 2. The CATENATE Capability A server which supports this extension returns "CATENATE" as one of the responses to the CAPABILITY command. 3. The APPEND command Arguments: mailbox name (The following can be repeated in the presence of the MULTIAPPEND extension [3]) Resnick Expires August 20, 2005 [Page 2] Internet-Draft IMAP CATENATE Extension February 2005 OPTIONAL flag parenthesized list OPTIONAL date/time string a single message literal or one or more message parts to catenate, specified as: message literal or message (or message part) URL Responses: OPTIONAL NO responses: BADURL, TOOBIG Result: OK - append completed NO - append error: can't append to that mailbox, error in flags or date/time or message text, or can't fetch that data BAD - command unknown or arguments invalid The APPEND command concatenates all of the message parts and appends them as a new message to the end of the specified mailbox. The parenthesized flag list and date/time string set the flags and the internal date, respectively, as described in IMAP [1]. The subsequent command parameters specify the message parts that are appended sequentially to the output message. If the old form of APPEND is used, a message literal follows the optional flag list and date/time string which is appended as described in IMAP [1]. If the new form is used, the token "CATENATE" and a parenthesized list of message literals and message URLs follows, each of which are appended to the new message. If a message literal is specified (indicated by the "TEXT"), the octets following the count are appended. If a message URL is specified (indicated by "URL"), the octets of the body part pointed to by that URL are appended, as if the literal returned in a FETCH BODY response were put in place of the message part specifier. The APPEND command does not cause the \Seen flag to be set for any catenated body part. Note: This document only describes the behavior of the APPEND command using message URLs (as defined by [2]) which refer to specific messages or message parts on the current IMAP server. Use of a URL that refers to anything other than a message or message part on the current IMAP server is outside of the scope of this document, would require an extension to this specification, and a server implementing only this specification would return NO to such a request. The client is responsible for making sure that the catenated message is in the format of an RFC 2822 [4] message. This includes inserting appropriate MIME [5] boundaries between body parts if necessary. Resnick Expires August 20, 2005 [Page 3] Internet-Draft IMAP CATENATE Extension February 2005 Responses behave just as the APPEND command described in IMAP [1]. If the server implements the IMAP UIDPLUS extension [6], it will also return an APPENDUID response code in the tagged OK response. Two response codes are provided in section 4 which can be used in the tagged NO response if the APPEND command fails. 4. Response Codes When a APPEND command fails it may return a response code that describes a reason for the failure. 4.1 BADURL Response The BADURL response code is returned if the APPEND fails to process one of the specified URLs. Possible reasons for this are bad url syntax, unrecognized URL schema, invalid message UID, invalid body part. The BADURL response code contains the first URL specified as a parameter to the APPEND command that has caused the operation to fail. 4.2 TOOBIG Response The TOOBIG response code is returned if the resulting message will exceed the 4Gb IMAP message limit. This might happen, for example, if the client specifies 3 URLs for 2Gb messages. Note, that even if the server doesn't return TOOBIG, it still has to be defensive against misbehaving or malicious clients that try to construct a message over 4Gb limit. The server may also wish to return the TOOBIG response code if the resulting message exceeds the server specific message size limit. Resnick Expires August 20, 2005 [Page 4] Internet-Draft IMAP CATENATE Extension February 2005 5. Formal Syntax The following syntax specification uses the Augmented Backus-Naur Form (ABNF) [7] notation. Elements not defined here can be found in the formal syntax of the ABNF [7] and IMAP [1] specifications. Note that resp-text-code is extended from original IMAP [1] specification. append = "APPEND" SP mailbox 1*append-message ; only a single append-message may appear ; if MULTIAPPEND capability is not present append-message = append-opts SP (literal / append-catenate) append-opts = [SP flag-list] [SP date-time] append-catenate = "CATENATE" SP "(" catenate-parts ")" catenate-parts = (text-literal / url) *(SP (text-literal / url)) text-literal = "TEXT" SP literal url = "URL" SP astring badurl_response_code = "BADURL" SP url-resp-text url-resp-text = 1*(%x01-09 / %x0B-0C / %x0E-5B / %x5D-FE) ; Any TEXT-CHAR except "]" toobig_response_code = "TOOBIG" resp-text-code =/ badurl_response_code / toobig_response_code The astring in the definition of url and the url-resp-text in the definition of badurl_response_code each contain an imapurl as defined by [2]. 6. Acknowledgments Thanks to the members of the LEMONADE working group for their input. Special thanks to Alexey Melnikov for the Examples. 7. Security Considerations The CATENATE extension does not raise any security considerations that are not present for the base protocol or in the use of IMAP URLs, and these issues are discussed in the IMAP [1] and IMAP URL [2] Resnick Expires August 20, 2005 [Page 5] Internet-Draft IMAP CATENATE Extension February 2005 documents. 8. IANA Considerations IMAP4 capabilities are registered by publishing a standards track or IESG approved experimental RFC. The registry is currently located at . This document defines the CATENATE IMAP capability. IANA is requested to add this capability to the registry. Appendix A. Examples Lines not starting with "C: " or "S: " are continuations of the previous lines. The original message in examples 1 and 2 below (UID = 20) has the following structure: multipart/mixed MIME message with two body parts: 1. text/plain 2. application/x-zip-compressed Example 1: The following example demonstrates how a CATENATE client can replace an attachment in a draft message, without the need to download it to the client and upload it back. C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE (URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/; UID=20;section=HEADER" TEXT {40} S: + Ready for literal data C: --------------030308070208000400050907 C: URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/; UID=20;section=1.MIME" URL "imap://imap.example.org/Drafts; UIDVALIDITY=385759045/;UID=20;section=1" TEXT {40} S: + Ready for literal data C: --------------030308070208000400050907 C: URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/; UID=30" {44} S: + Ready for literal data C: --------------030308070208000400050907-- C: ) S: A003 OK catenate append completed Resnick Expires August 20, 2005 [Page 6] Internet-Draft IMAP CATENATE Extension February 2005 Example 2: The following example demonstrates how the CATENATE extension can be used to replace edited text in a draft message, as well as header fields for the top level message part (e.g. Subject has changed). The previous version of the draft is marked as \Deleted. Note, that the server also supports the UIDPLUS extension, so the APPENDUID response code is returned in the successful OK response to the APPEND command. C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE (TEXT {738} S: + Ready for literal data C: Return-Path: C: Received: from [127.0.0.2] C: by rufus.example.org via TCP (internal) with ESMTPA; C: Thu, 11 Nov 2004 16:57:07 +0000 C: Message-ID: <419399E1.6000505@example.org> C: Date: Thu, 12 Nov 2004 16:57:05 +0000 C: From: Bob Ar C: X-Accept-Language: en-us, en C: MIME-Version: 1.0 C: To: foo@example.net C: Subject: About our holiday trip C: Content-Type: multipart/mixed; C: boundary="------------030308070208000400050907" C: C: --------------030308070208000400050907 C: Content-Type: text/plain; charset=us-ascii; format=flowed C: Content-Transfer-Encoding: 7bit C: C: Our travel agent has sent the updated schedule. C: C: Cheers, C: Bob C: --------------030308070208000400050907 C: URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/; UID=20;Section=2.MIME" URL "imap://imap.example.org/Drafts; UIDVALIDITY=385759045/;UID=20;Section=2" TEXT {44} S: + Ready for literal data C: --------------030308070208000400050907-- C: ) S: A003 OK [APPENDUID 385759045 45] append Completed C: A004 UID STORE 20 +FLAGS.SILENT (\Deleted) S: A004 OK STORE completed Resnick Expires August 20, 2005 [Page 7] Internet-Draft IMAP CATENATE Extension February 2005 Example 3: The following example demonstrates how the CATENATE extension can be used to strip attachments. Below a PowerPoint attachment was replaced by a small text part explaining that the attachment was stripped. C: A003 APPEND Drafts (\Seen \Draft $MDNSent) CATENATE (URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/; UID=21;section=HEADER" TEXT {40} S: + Ready for literal data C: --------------030308070208000400050903 C: URL "imap://imap.example.org/Drafts;UIDVALIDITY=385759045/; UID=21;section=1.MIME" URL "imap://imap.example.org/Drafts; UIDVALIDITY=385759045/;UID=21;section=1" TEXT {255} S: + Ready for literal data C: --------------030308070208000400050903 C: Content-type: text/plain; charset="us-ascii" C: Content-transfer-encoding: 7bit C: C: This bodypart contained a Power Point presentation, that was C: deleted upon your request. C: --------------030308070208000400050903-- C: ) S: A003 OK append Completed Resnick Expires August 20, 2005 [Page 8] Internet-Draft IMAP CATENATE Extension February 2005 Example 4: The following example demonstrates a failed APPEND command. The server returns the BADURL response code to indicate that one of the provided URLs is invalid. This example also demonstrates how the CATENATE extension can be used to construct a digest of several messages. C: A003 APPEND Sent (\Seen $MDNSent) CATENATE (TEXT {541} S: + Ready for literal data C: Return-Path: C: Received: from [127.0.0.2] C: by rufus.example.org via TCP (internal) with ESMTPA; C: Thu, 11 Nov 2004 16:57:07 +0000 C: Message-ID: <419399E1.6000505@example.org> C: Date: Thu, 21 Nov 2004 16:57:05 +0000 C: From: Farren Oo C: X-Accept-Language: en-us, en C: MIME-Version: 1.0 C: To: bar@example.org C: Subject: Digest of the mailing list for today C: Content-Type: multipart/digest; C: boundary="------------030308070208000400050904" C: C: --------------030308070208000400050904 C: URL "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/; UID=11467" TEXT {40} S: + Ready for literal data C: --------------030308070208000400050904 C: URL "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/; UID=113330;section=1.5.9" TEXT {40} S: + Ready for literal data C: --------------030308070208000400050904 C: URL "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/; UID=11916" TEXT {44} S: + Ready for literal data C: --------------030308070208000400050904-- C: ) S: A003 NO [BADURL "imap://imap.example.org/INBOX;UIDVALIDITY=785799047/ ;UID=113330;section=1.5.9"] CATENATE append has failed, one message expunged 9. Normative References [1] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1", RFC 3501, March 2003. [2] Newman, C., "IMAP URL Scheme", RFC 2192, September 1997. [3] Crispin, M., "Internet Message Access Protocol (IMAP) - Resnick Expires August 20, 2005 [Page 9] Internet-Draft IMAP CATENATE Extension February 2005 MULTIAPPEND Extension", RFC 3502, March 2003. [4] Resnick, P., "Internet Message Format", RFC 2822, April 2001. [5] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [6] Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1998. [7] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. Author's Address Peter W. Resnick QUALCOMM Incorporated 5775 Morehouse Drive San Diego, CA 92121-1714 US Phone: +1 858 651 4478 Email: presnick@qualcomm.com URI: http://www.qualcomm.com/~presnick/ Resnick Expires August 20, 2005 [Page 10] Internet-Draft IMAP CATENATE Extension February 2005 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. 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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 (2005). 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. Resnick Expires August 20, 2005 [Page 11]