Extended URLFETCH for Binary and Converted Parts
RFC 5524

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 03

Network Working Group                                        D. Cridland
Request for Comments: 5524                                 Isode Limited
Category: Standards Track                                       May 2009

            Extended URLFETCH for Binary and Converted Parts

Status 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) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

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.

Cridland                    Standards Track                     [Page 1]
RFC 5524                    URLFETCH Binary                     May 2009

Table of Contents

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................2
   3. Extended URLFETCH ...............................................2
      3.1. Command Parameters .........................................3
      3.2. Response Metadata ..........................................3
   4. Example Exchanges ...............................................4
   5. Formal Syntax ...................................................6
   6. IANA Considerations .............................................7
   7. Security Considerations .........................................7
   8. Acknowledgements ................................................7
   9. References ......................................................8
      9.1. Normative References .......................................8
      9.2. Informative References .....................................8

1.  Introduction

   Although [URLAUTH] provides a URLFETCH command that can be used to
   dereference a URL and return the body-part data, it does so by
   returning the encoded form, without sufficient metadata 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 in [STREAMING].

   This memo specifies a mechanism that returns additional metadata
   about the part, such as its [MEDIATYPE] type, as well as removes any
   content transfer encoding that was used on the body part.

2.  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 RFC 2119 [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.

3.  Extended URLFETCH

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

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

Cridland                    Standards Track                     [Page 2]
RFC 5524                    URLFETCH Binary                     May 2009

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.  Cases
   where there is an absence of any parameters or where the URL is sent
   unenclosed cause the command to behave precisely as specified in
   [URLAUTH].

   Similarly, if the URL is invalid, the command will behave precisely
   as specified in [URLAUTH] and return a simple NIL.

   Available parameters are:

   BODYPARTSTRUCTURE
      Provide a BODYPARTSTRUCTURE.

      BODYPARTSTRUCTURE is defined in [CONVERT] and provides metadata
      useful for processing applications, such as the type of data.

   BINARY
      Provide the data without any Content-Transfer-Encoding.