Internet Engineering Task Force (IETF) K. Meadors, Ed.

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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RFC 6362 Multiple Attachments for EDIINT August 2011

Copyright Notice

Copyright (c) 2011 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
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This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
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Without obtaining an adequate license from the person(s) controlling
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not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.

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

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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.

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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.

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RFC 6362 Multiple Attachments for EDIINT August 2011

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

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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: <[email protected]>
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>

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[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.

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RFC 6362 Multiple Attachments for EDIINT August 2011

[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: [email protected]

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