Internet Engineering Task Force (IETF)                   K. Meadors, Ed.
Request for Comments: 6362                          Drummond Group, Inc.
Category: Informational                                      August 2011
ISSN: 2070-1721


                        Multiple Attachments for
      Electronic Data Interchange - Internet Integration (EDIINT)

Abstract

   The Electronic Data Interchange - Internet Integration (EDIINT) AS1,
   AS2, and AS3 messages were designed specifically for the transport of
   EDI documents.  Since multiple interchanges could be placed within a
   single EDI document, there was not a need for sending multiple EDI
   documents in a single message.  As adoption of EDIINT grew, other
   uses developed aside from single EDI document transport.  Some
   transactions required multiple attachments to be interpreted together
   and stored in a single message.  This Informational RFC describes how
   multiple documents, including non-EDI payloads, can be attached and
   transmitted in a single EDIINT transport message.  The attachments
   are stored within the MIME multipart/related structure.  A minimal
   list of content-types to be supported as attachments is provided.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6362.

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Table of Contents

   1. Introduction ....................................................3
      1.1. Requirements Language ......................................3
   2. Using Multiple Attachments in EDIINT ............................3
      2.1. Multipart/Related Structure ................................3
      2.2. EDIINT-Features Header .....................................4
      2.3. MIC Calculation ............................................4
      2.4. Document Processing ........................................5
      2.5. Content-Types to Support ...................................5
   3. Example Message .................................................6
   4. Security Considerations .........................................7
   5. Normative References ............................................7

1.  Introduction

   The primary work of the EDIINT working group (WG) was to develop a
   secure means of transporting EDI documents over the Internet.  This
   was described in the three WG-developed standards for secure
   transport over SMTP AS1 [RFC3335], HTTP AS2 [RFC4130], and FTP AS3
   [RFC4823].  For most uses of EDI, all relevant information to
   complete a single business transaction could be stored in a single
   document.  As adoption of EDIINT grew, new industries and businesses
   began using AS2 and also needed to include multiple documents in a
   single message to complete a trading-partner transaction.  These
   documents were a variety of MIME media types.  This Informational RFC
   describes how to use the MIME multipart/related body structure within
   EDIINT messages to store multiple document attachments.  Details of
   computing the message integrity check (MIC) value over this body are
   covered.  A minimum listing of MIME media types to support within the
   multipart/related body is given along with information on extracting
   these documents.

1.1.  Requirements Language

   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 [RFC2119].

2.  Using Multiple Attachments in EDIINT

2.1.  Multipart/Related Structure

   Multiple payload attachments for EDIINT messages are stored within a
   multipart/related MIME body [RFC2387].  The multipart/related
   structure allows multiple MIME attachments or message payloads to be
   communicated in a single structure and message.

   The attached payloads can be of any MIME content-type depending on
   the trading-partner agreement, but Section 2.5 lists the
   content-types that MUST be supported.  The use and format of the
   multipart/ related body follows the rules in RFC 2387 [RFC2387],
   including the required type parameter to determine the root body
   part.  The use of the optional start parameter is RECOMMENDED.

2.2.  EDIINT-Features Header

   To indicate support for multiple attachments (MAs), an EDIINT
   application MUST use the EDIINT-Features header [RFC6017].  The
   EDIINT-Features header indicates that the instance application can
   support various features, such as certification exchange.  The header
   is present in all messages from the instance application, not just
   those that feature certification exchange.

   For applications implementing multiple attachments, the
   MA-Feature-Name MUST be used within the EDIINT-Features header as
   listed in this ABNF [RFC5234] syntax:

      MA-Feature-Name = "multiple-attachments"

   An example of the EDIINT-Features header in a message from an
   application supporting MA:

      EDIINT-Features: multiple-attachments

2.3.  MIC Calculation

   MIC calculation in an EDIINT message with multiple attachments is
   performed in the same manner as for a single EDI payload.  The only
   difference is calculating the message integrity check (MIC) over the
   whole multipart/related body rather than a single EDI payload.
   Section 5.2.1 of AS1 [RFC3335] and Section 4 of EDIINT COMPRESSION
   [RFC5402] describe the MIC calculations used for a single payload
   document within an EDIINT message.  The approach is summarized below
   for the multipart/related body.  Refer to stated sections above for
   more details.

   For a compressed but unsigned message, regardless of encryption, the
   MIC is calculated over the uncompressed multipart/related body
   including any applied Content-Transfer-Encoding.  The body MUST be
   canonicalized according to the procedure described in the underlying
   transport protocol (e.g., HTTP AS2 [RFC4130]) before the MIC is
   calculated.

   For an encrypted but unsigned and uncompressed message, the MIC is
   calculated on the decrypted multipart/related body, including the
   header and all attached documents.  The body MUST be canonicalized
   according to the procedure described in the underlying transport
   protocol (e.g., HTTP AS2 [RFC4130]) before the MIC is calculated.

   For an unsigned and unencrypted message, the MIC is calculated over
   the data inside the multipart/related boundaries prior to
   Content-Transfer-Encoding.  However, unsigned and unencrypted
   messages SHOULD NOT be sent due to lack of security.

   If the expected MIC value differs from the calculated MIC value, all
   attachments MUST be considered invalid and retransmitted.

2.4.  Document Processing

   Upon receipt of an EDIINT message with multiple attachments, the
   receiving user agent MUST be able to extract the attached payloads
   from the message rather than only removing the multipart/related body
   from the message.  The storing or processing of the documents as they
   relate to the pending transaction is implementation dependent.

2.5.  Content-Types to Support

   Documents of the following MIME media types MAY be found in a
   multipart/related body and MUST be accepted by the user agent.
   However, any media type can be used depending upon industry need, and
   other media types MAY be accepted depending upon the trading-partner
   agreement.  Please see [MIMEREG] for the definitions of the media
   types listed below.

      application/xml

      application/pdf

      application/msword

      application/rtf

      application/octet-stream

      application/zip

      image/gif

      image/tiff

      image/jpeg

      text/plain

      text/html

      text/rtf

      text/xml

3.  Example Message

   Below is an example AS2 message that uses two attachments.  The first
   attachment is an XML document, which is the root attachment, and the
   second attachment is a PDF document.  The content of both the XML and
   PDF documents, as well as the applied digital signature, has been
   omitted for size consideration.  This example is provided as an
   illustration only and is not considered part of the specification.
   If the example conflicts with the definitions specified above or in
   the other referenced RFCs, the example is considered invalid.

      POST /as2 HTTP/1.1
      Host: www.example.com:8080
      Connection: Close, TE
      Message-ID: <1109712943488@10.65.122.242>
      Subject: Multiple Attachment Example
      Date: Tue, 01 Mar 2005 21:37:03 GMT
      AS2-To: TradingPartner
      AS2-From: User
      AS2-Version: 1.2
      EDIINT-Features: multiple-attachments
      Disposition-Notification-To: http://www.example.com/as2
      Disposition-Notification-Options:
         signed-receipt-protocol=optional,pkcs7-signature;
         signed-receipt-micalg=optional,sha-1
      Content-type: multipart/signed;
         protocol="application/pkcs7-signature"; micalg=sha-1;
         boundary="OUTER-BOUNDARY"
      Content-length: 207440

      --OUTER-BOUNDARY
      Content-type: multipart/related; boundary="INNER-BOUNDARY";
         start="<root.attachment>"; type="application/xml"

      --INNER-BOUNDARY
      Content-type: application/xml
      Content-ID: <root.attachment>

      [XML DOCUMENT]

      --INNER-BOUNDARY
      Content-type: application/pdf
      Content-ID: <2nd.attachment>

      [PDF DOCUMENT]

      --INNER-BOUNDARY--

      --OUTER-BOUNDARY
      Content-type: application/pkcs7-signature

      [DIGITAL SIGNATURE]

      --OUTER-BOUNDARY--

4.  Security Considerations

   Multiple attachments have security concerns that are very similar to
   those described in the three EDIINT transport standards.  These
   include the importance of using strong cryptography and the necessity
   of using valid certificates and chaining to a trusted certification
   authority (CA).  Please refer to these standards -- SMTP AS1
   [RFC3335], HTTP AS2 [RFC4130], and FTP AS3 [RFC4823] -- for details
   of their security considerations.

   The only additional security consideration is that if the MIC
   calculation by the user agent differs from the expected MIC
   calculation, all the attached documents MUST be considered invalid.
   Because the MIC calculation is over the multipart/related body, the
   MIC validates the content integrity of all the documents.

5.  Normative References

   [MIMEREG]  "MIME Media Types", <http://www.iana.org/>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2387]  Levinson, E., "The MIME Multipart/Related Content-type",
              RFC 2387, August 1998.

   [RFC3335]  Harding, T., Drummond, R., and C. Shih, "MIME-based Secure
              Peer-to-Peer Business Data Interchange over the Internet",
              RFC 3335, September 2002.

   [RFC4130]  Moberg, D. and R. Drummond, "MIME-Based Secure Peer-to-
              Peer Business Data Interchange Using HTTP, Applicability
              Statement 2 (AS2)", RFC 4130, July 2005.

   [RFC4823]  Harding, T. and R. Scott, "FTP Transport for Secure Peer-
              to-Peer Business Data Interchange over the Internet",
              RFC 4823, April 2007.

   [RFC5234]  Crocker, D., Ed., and P. Overell, "Augmented BNF for
              Syntax Specifications: ABNF", STD 68, RFC 5234,
              January 2008.

   [RFC5402]  Harding, T., Ed., "Compressed Data within an Internet
              Electronic Data Interchange (EDI) Message", RFC 5402,
              February 2010.

   [RFC6017]  Meadors, K., Ed., "Electronic Data Interchange - Internet
              Integration (EDIINT) Features Header Field", RFC 6017,
              September 2010.

Author's Address

   Kyle Meadors (editor)
   Drummond Group, Inc.
   Nashville, Tennessee  37221
   US

   Phone: +1 (817) 709-1627
   EMail: kyle@drummondgroup.com