LEMONADE P. Resnick Internet-Draft QUALCOMM Incorporated Expires: June 11, 2005 December 11, 2004 Internet Message Access Protocol (IMAP) CATENATE Extension draft-ietf-lemonade-catenate-03 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 June 11, 2005. Copyright Notice Copyright (C) The Internet Society (2004). Abstract The CATENATE extension to the Internet Message Access Protocol (IMAP) allows 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 June 11, 2005 [Page 1] Internet-Draft IMAP CATENATE Extension December 2004 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 command works much like the APPEND command except 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. There are some obvious uses for the CATENATE command. The motivating use case for this command 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 CATENATE creates the message in the client's 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.) CATENATE 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. CATENATE 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 CATENATE command Arguments: mailbox name message parameter list or NIL one or more message parts to catenate, specified as: message literal Resnick Expires June 11, 2005 [Page 2] Internet-Draft IMAP CATENATE Extension December 2004 or message (or message part) URL Responses: no specific responses for this command Result: OK - catenate completed NO - catenate 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 CATENATE command concatenates all of the message parts and appends them as a new message to the end of the specified mailbox. The message parameters defined in this document for the message parameter list are a parenthesized flag list (indicated by "FLAGS") and date/time string (indicated by "DATE") that are used just as they are in the APPEND command, setting the flags and the internal date, respectively. The subsequent command parameters specify the message parts that are appended sequentially to the output message. If a message literal is specified (indicated by the "TEXT"), the octets following the count are appended just as they would be with the APPEND command. 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 CATENATE command does not cause the \Seen flag to be set for any catenated body part. Note: This document only describes the behavior of the CATENATE command using a message URL (as defined by [2]) which refers to a specific message or message part in the currently selected mailbox on the current IMAP server. (Because of that, the CATENATE command is valid in the selected state for purposes of this specification.) Use of a URL that refers to anything other than a message or message part from the currently selected mailbox 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 [3] message. This includes inserting appropriate MIME [4] boundaries between body parts if necessary. Responses behave just as the APPEND command. If the server implements the IMAP UIDPLUS extension [5], 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 Resnick Expires June 11, 2005 [Page 3] Internet-Draft IMAP CATENATE Extension December 2004 response if the CATENATE command fails. 4. Response Codes When a CATENATE 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 CATENATE 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 CATENATE 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 June 11, 2005 [Page 4] Internet-Draft IMAP CATENATE Extension December 2004 5. Formal Syntax The following syntax specification uses the Augmented Backus-Naur Form (ABNF) [6] notation. Elements not defined here can be found in the formal syntax of the ABNF [6] and IMAP [1] specifications. Note that resp-text-code is extended from original IMAP [1] specification. catenate = "CATENATE" SP mailbox SP parameters 1*(SP (text-literal / url)) parameters = ("(" parameter *(SP parameter) ")") / "NIL" parameter = ("FLAGS" SP flag-list) / ("DATE" SP date-time) text-literal = "TEXT" SP literal url = "URL" SP astring badurl_response_code = "BADURL" SP url-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-text in the definition of badurl_response_code contain an imapurl as defined by [2]. 6. Acknowledgments Thanks to Alexey Melnikov for the Examples. Thanks to all of the LEMONADE working group for their input. 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] 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 Resnick Expires June 11, 2005 [Page 5] Internet-Draft IMAP CATENATE Extension December 2004 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 CATENATE Drafts FLAGS (\Seen \Draft $MDNSent) 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=1.1" 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 Completed Resnick Expires June 11, 2005 [Page 6] Internet-Draft IMAP CATENATE Extension December 2004 Example 2: The following example demonstrates how CATENATE 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 CATENATE command. C: A003 CATENATE Drafts FLAGS (\Seen \Draft $MDNSent) 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=1.2" TEXT {44} S: + Ready for literal data C: --------------030308070208000400050907-- C: S: A003 OK [APPENDUID 385759045 45] CATENATE Completed C: A004 UID STORE 20 +FLAGS.SILENT (\Deleted) S: A004 OK STORE completed Resnick Expires June 11, 2005 [Page 7] Internet-Draft IMAP CATENATE Extension December 2004 Example 3: The following example demonstrates how CATENATE 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 CATENATE Drafts FLAGS (\Seen \Draft $MDNSent) 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=1.1" 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 CATENATE Completed Resnick Expires June 11, 2005 [Page 8] Internet-Draft IMAP CATENATE Extension December 2004 Example 4: The following example demonstrates a failed CATENATE command. The server returns the BADURL response code to indicate that one of the provided URLs is invalid. This example also demonstrates how CATENATE can be used to construct a digest of several messages. C: A003 CATENATE Sent FLAGS (\Seen $MDNSent) 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 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] Resnick, P., "Internet Message Format", RFC 2822, April 2001. Resnick Expires June 11, 2005 [Page 9] Internet-Draft IMAP CATENATE Extension December 2004 [4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [5] Myers, J., "IMAP4 UIDPLUS extension", RFC 2359, June 1998. [6] Crocker, D. 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 June 11, 2005 [Page 10] Internet-Draft IMAP CATENATE Extension December 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. 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