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Versions: 00 01 02 03 RFC 5524

Network Working Group                                        D. Cridland
Internet-Draft                                             Isode Limited
Expires: May 15, 2008                                  November 12, 2007


            Extended URLFETCH for binary and converted parts
                   draft-cridland-urlfetch-binary-00

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   This Internet-Draft will expire on May 15, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The URLFETCH command defined as part of URLAUTH provides a mechanism
   for third-parties to gain access to data held within messages in a
   user's private store, however, this data is sent verbatim, which is
   not suitable for a number of applications.  This memo specifies a
   method for obtaining data in forms suitable for non-mail
   applications.






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Table of Contents

   1.  Conventions used in this document . . . . . . . . . . . . . . . 3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Extended URLFETCH . . . . . . . . . . . . . . . . . . . . . . . 3
     3.1.  Command Parameters  . . . . . . . . . . . . . . . . . . . . 3
     3.2.  Response Metadata . . . . . . . . . . . . . . . . . . . . . 4
   4.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 5
   5.  Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . . 5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 6
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8


































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1.  Conventions used in this document

   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 [KEYWORDS].

   Protocol examples are line-wrapped for clarity.  Protocol strings are
   prefixed with C: and S: for client and server respectively, and
   elided data is represented by [...].  Implementors should note these
   notations are for editorial clarity only.


2.  Introduction

   Although [URLAUTH] provides a URLFETCH command which can be used to
   dereference a URL and return the body part data, it does so by
   returning the encoded form, without sufficient data to decode.  This
   is suitable for use in mail applications such as [BURL], where the
   encoded form is suitable, but not where access to the actual content
   is required, such as [STREAMING].

   This memo specifies a mechanism which returns additional metadata
   about the part, such as its media type, as well as removing any
   content transfer encoding used on the body part.


3.  Extended URLFETCH

   This extension is available in any IMAP server implementation which
   includes URLAUTH=BINARY within its capability string.

   Such servers accept additional, per-URL, parameters to the URLFETCH
   command, and will provide, upon request, additional data for each URL
   dereferenced.

3.1.  Command Parameters

   The URLFETCH command is extended by the provision of optional
   parameters.  The extended URLFETCH command is distinct by enclosing
   each URL and associated parameters in a parenthesized list.  The
   absence of any parameters, or if the URL is sent unenclosed, causes
   the command to behave precisely as specified in [URLAUTH].

   Available parameters are:







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   BODYPARTSTRUCTURE
      Provides a BODYPARTSTRUCTURE in additional to the data itself.
      BODYPARTSTRUCTURE is defined in [CONVERT].

   BINARY
      Remove any Content-Transfer-Encoding.  In particular, this means
      that the data MAY contain NUL octets, and not be formed from
      textual lines.  Data containing NUL octets MUST be transferred
      using the literal8 syntax defined in [BINARY].


3.2.  Response Metadata

   In order to carry any requested metadata and provide additional
   information to the consumer, the URLFETCH response is similarly
   extended.

   Following the URL itself, servers will include a series of
   parenthesized metadata elements.  Defined metadata elements are as
   follows:
   BODYPARTSTRUCTURE
      The BODYPARTSTRUCTURE provides information about the data
      contained in the response, as it has been returned.  It will
      reflect any conversions or decoding that have taken place.


   Note that unlike [CONVERT], BODYPARTSTRUCTURE is not appended with
   the part specifier, as this is implicit in the URL.























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4.  Formal Syntax

   This formal syntax uses ABNF as specified in [ABNF], and includes
   productions defined in [URLAUTH] and [IMAP].

   capability       =/ "URLAUTH=BINARY"

      ; Command parameters; see Section 3.1

   urlfetch         =  "URLFETCH" 1*(SP url-fetch-arg)

   url-fetch-arg    =  url-fetch-simple / url-fetch-ext

   url-fetch-simple =  url-full
      ; Unextended URLFETCH.

   url-fetch-ext    =  "(" url-full *(SP url-fetch-param) ")"
      ; If no url-fetch-param present, as unextended.

   url-fetch-param  =  "BINARY" / "BODYPARTSTRUCTURE" / atom
      ; TODO: Should this be iana-token?

      ; Response; see Section 3.2

   urlfetch-data    =  "*" SP "URLFETCH" 1*(SP url-full [url-metadata]
                       SP (nstring / literal8))
      ; MUST use nstring and MUST NOT use SP url-metadata when client
      ; issues url-fetch-simple or no url-fetch-param.

   url-metadata     =  1*(SP "(" url-metadata-el ")")

   url-metadata-el  =  "BODYPARTSTRUCTURE" SP body



5.  Open Issues


6.  IANA Considerations

   This document has no actions for IANA.


7.  Security Considerations







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8.  Acknowledgements

   Comments were received on the idea, and/or this draft, from Neil
   Cook, Philip Guenther, and others.  Whether in agreement or dissent,
   the comments have refined and otherwise influenced the document.


9.  References

9.1.  Normative References

   [ABNF]     Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", RFC 4234, October 2005.

   [BINARY]   Nerenberg, L., "IMAP4 Binary Content Extension", RFC 3516,
              April 2003.

   [CONVERT]  Melnikov, A. and P. Coates, "IMAP CONVERT extension",
              draft-ietf-lemonade-convert-12 (work in progress),
              October 2007.

   [IMAP]     Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
              4rev1", RFC 3501, March 2003.

   [KEYWORDS]
              Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [URLAUTH]  Crispin, M., "Internet Message Access Protocol (IMAP) -
              URLAUTH Extension", RFC 4467, May 2006.

9.2.  Informative References

   [BURL]     Newman, C., "Message Submission BURL Extension", RFC 4468,
              May 2006.

   [STREAMING]
              Cook, N., "Streaming Internet Messaging Attachments",
              draft-ietf-lemonade-streaming-03 (work in progress),
              September 2007.











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Author's Address

   Dave Cridland
   Isode Limited
   5 Castle Business Village
   36, Station Road
   Hampton, Middlesex  TW12 2BX
   GB

   Email: dave.cridland@isode.com









































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