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EDIINT Working Group                                 Chuck Shih
draft-ietf-ediint-as2-00.txt                              Dale Moberg
Expires in six months                                       Rik Drummond
                                                        14 November 1997

                      HTTP Transport for Secure EDI

                      draft-ietf-ediint-as2-00.txt

Status of this Memo

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Abstract

This document describes how to exchange EDI documents securely
using http transport for EDI data that is packaged in MIME messages
that use public key security body parts.

Feedback Instructions:

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Table of Contents

1.  Introduction
   1.1 Purpose and relation to previous work
   1.2 Overall operation

2. Stages of an HTTP EDI exchange transaction
   2.1 EDI sending using POST
    2.1.1 Response and Error Codes for POST requests
    2.1.2 Using Transport Layer Security
   2.2 Receipt Reply

3. Referenced RFCs and their contribution
   3.1  RFC 2068: Hypertext Transfer Protocol -- HTTP/1.1 [11]
   3.2  Internet draft (dierks): Transport Layer Security [11]
   3.3  RFC 1847 MIME Security Multiparts [6]
   3.4  RFC 1892 Multipart/report [9]
   3.5  RFC 1767 EDI Content [2]
   3.6  RFC 2015 PGP/MIME [4]
   3.7  RFC 2045, 2046, and 2049 MIME [1]
   3.8  Internet draft (fajman): Message Disposition Notification [5]
   3.9  Internet draft (dusse): - S/MIME Specification [8]

4. Differences between HTTP and SMTP based transport
   4.1 Unused MIME headers and operations
    4.1.1  Content-Transfer-Encoding not used
    4.1.2  Epilogue must be empty
    4.1.3  Lengthy message bodies and Message/partial
   4.2 Differences in MIME or other headers or parameters used
    4.2.1  Content-Length needed.
    4.2.2  Disposition-notification-to
    4.2.3  To, Final-Recipient, and Original Recipient
    4.2.4  Message-Id and Original-Message-Id
    4.2.5  Host

5.  Acknowledgments

6.  References

7.  Authors' Addresses


1.  Introduction

    1.1 Purpose and relation to previous work

    Early work on Internet EDI focused on specifying MIME content
    types for EDI data ([2] RFC 1767). The functional requirements
    document [9], "Requirements for Interoperable Internet EDI,"
    provides extensive information on EDI security
    and the business and user processes surrounding the need for and
    use of EDI security. In addition, MIME structures
    appropriate for SMTP transport of the packaged EDI data have
    been specified ([12] "MIME-based Secure EDI" draft ).
    That specification also describes comprehensive security features,
    specifically data privacy, data integrity/authenticity,
    non-repudiation of origin and non-repudiation of receipt.

    In this document, it is assumed that the reader is familiar
    with the SMTP/MIME transport document, the requirements document,
    and the RFCs applied or referenced in those documents.

    This draft, like the SMTP/MIME transport document, builds on
    previous RFCs and is attempting to "re-invent" as little
    as possible.  The goal here is to specify how previously specified
    MIME messaging structures and operations can be adapted for use with
    HTTP servers and clients to obtain secure, reliable,
    and acknowledged transport for EDI data.

    The applicability statement, [12] "MIME-based Secure EDI,"
    explained the basic EDI transaction using the concept of a
    "secure transmission loop" for EDI. This loop involves
    one organization sending a signed and encrypted EDI
    interchange to another organization,
    requesting a signed receipt, followed later by the
    receiving organization sending this signed receipt back to the
    sending organization.  In other words, the following transpires:

       i. The organization sending EDI/EC data encrypts the data and
       provides a digital signature, using either PGP/MIME or S/MIME.
       In addition, they request a signed receipt.

       ii. The receiving organization decrypts the message and verifies
       the signature, resulting in verified integrity of the data and
       authenticity of the sender.

       iii. The receiving organization then sends a signed receipt in the
       form of a signature over the hash of a message disposition
       notification, which contains a hash of the received message.

    The above describes functionality which if implemented would
    satisfy all security requirements. Other restricted subsets of
    functionality have also been characterized. In this document, the
    goal is to make use of HTTP instead of SMTP as a transport protocol,
    and make changes needed to adapt to protocol packaging differences.
    An option to make use of Transport Layer Security [13] to provide
    privacy is also added.

    Note that 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.

   1.2 Overall operation

    A HTTP POST operation [11] is used to send appropriately packaged
    EDI or other business data. The Request-URI ([11] section 9.5)
    identifies a process to unpack and handle the message data
    and to generate a reply for the client that contains a message
    disposition acknowledgement. This request/reply transaction
    provides secure, reliable, and authenticated transport for EDI
    or other business data using HTTP.


2. Stages of an HTTP EDI exchange transaction

    An EDI data file or stream is first structured into one of the
    message templates described in [12], sections 4.2.1 to 4.2.4 or
    4.3.1 to 4.3.4 for PGP/MIME or S/MIME security. If TLS is to be used,
    the typical packaging will be that provided in 4.2.2 or 4.3.2;
    that is, a multipart/signed message will be created with no
    encryption in the message. Otherwise, if privacy
    is desired, message templates 4.2.4 or 4.3.4 are used.
    Content transfer encoding MUST not be used.  A content-length
    field MUST be provided.

    To request an unsigned message disposition notification,
    additional extension headers should be added to the content-type
    and content-length headers in the entity header section preceding
    the message body.

    A Disposition-Notification-To [5] header is added to indicate
    that a message disposition notification is requested
    in the reply to the POST request. The value for this header
    plays no real role in the reply mechanism, unlike in the
    SMTP transport reply. A Message-ID header may be added to support
    message reconciliation, although the role of this value is not
    crucial in a connection-oriented (the HTTP/1.1 default) transaction.

    A Disposition-Notification-Options header is used to request
    a signed message disposition notification. The parameters
    used to select protocols for signed message disposition
    notification are found in [12].

    2.1 EDI sending using POST

    For sending EDI, the following protocol elements are typically
    present: a request line [11], section 5.1,  entity headers, a
    CRLF pair to mark the end of the entity headers, followed by the
    message-body.

    The request line will have the form: "POST Request-URI HTTP/1.1".
    The spaces must be present. (The Request-URI is normally exchanged
    out of band, as part of setting up a trading partner agreement.
    Automation of this process is outside this specification.)
    The request line must be followed by a CRLF.

    The request line may be followed by general headers and
    request headers, but must be followed by entity headers
    specifying content length ([11] section 14.14) and content type
    [11] section 14.18. The Host request header ([11] sections 9
    and 14.23) MUST be included.

    The entity headers used for requesting a message disposition
    notification (unsigned or signed) have previously been mentioned.

    2.1.1 Response and Error Codes for POST requests

    The status line for response to errors in the POST request line
    will be provided by a status line with the following protocol
    elements present ( [11], section 6.1 ) : HTTP version (normally,
    HTTP/1.1), a status code, reason phrase, and CRLF.

    The suggested status code should be a 204 ("No Content")
    in case the request-URI process does not produce
    an entity to return. Other explicit error codes are
    documented in [11], sections 6.1.1 and throughout section 10.
    For errors in the request-URI, 400 ("Bad Request"),
    404 ("Not Found") and similar codes are appropriate status codes.
    Successful responses will be discussed in section 2.2 below,
    where the inclusion of an entity containing the message
    disposition notification is also discussed.

    2.1.2 Using Transport Layer Security

    To use Transport Layer Security, the request-URI should indicate
    the appropriate scheme value, https. Usually only a multipart/signed
    message body would be sent using TLS, as encrypted message bodies
    would be redundant. Encrypted message bodies may be sent, however.


    2.2 Receipt Reply

    The response to the POST command varies depending upon whether
    a receipt has been requested and upon what kind of receipt
    has been requested.

    With no extended header requesting a receipt, and no errors
    accessing the request-URI specified processing, the status
    line in the Response to the POST request should be 200,
    201 or 202. Status code 200 ("OK") should be used when
    an entity is returned (a signed receipt in a multipart/signed
    content type or an unsigned receipt in a multipart/report).
    Status 201 ("Created") should be used if a URI pointing to a receipt
    is returned; this may be preferable to returning an unsolicited
    receipt. The code 202 ("Accepted") should be used to indicate
    processing unable to generate acknowledgements; this status
    is non-committal on the disposition of the message.

    An application may include an unsolicited multipart/report
    as a message body. Extended headers for content-type
    and content-length must be provided.

    When a message disposition notice extended header is present
    in the POST request extended headers, then entity headers for
    the message disposition notice should be included and a message
    body containing the multipart/report [10] or multipart/signed [6]
    should be included in the Response entity headers as appropriate.
    The basic responsibilities of responding to requests are discussed
    at length in [12] section 5, and in detail within section 5.2.1.

    Message Disposition Notifications, when used in the HTTP reply
    context, will normally contain a restricted set of features
    of a MDN.

    The disposition field is a required element in the machine
    readable second part of a multipart/report.
    The final-recipient-field([5] section 3.1) value need not
    be derived from the entity headers of the request,
    because the "To" field may be absent in the entity
    headers. In the case of a signed report,
    the value may be the email address field from
    the signer's X.509 attribute for email addresses.
    For unsigned reports, a technical or administrative
    contact's email address may be included. However,
    if a "To" field is present in the request headers,
    then that value should be used for the value of the
    "Final-Recipient" field in the message/disposition-notification
    body part.

    An application should report the Message-ID of a request
    if it was included in the request using the original-message-
    id-field in the message/disposition-notification body part.

    The human readable part (the first part of the multipart/report)
    may omit items such as the subject, date and other information
    not generally present in header fields in the POST request.
    Generally the first report part  will consist of some text
    reflecting the disposition status.

    The HTTP reply SHOULD omit the third part of the report (which
    can includes the original message or its headers in the SMTP
    context).


3. Referenced RFCs and their contribution

     3.1 RFC 2068 [11] : The HyperText Transfer Protocol, HTTP,
     provides an application level protocol for distributed hypermedia
     information systems. This standard specifies the protocol HTTP/1.1.

     3.2 Internet Draft  draft-ietf-tls-protocol-04.txt: Transport Layer
     Security specifies a protocol similar to SSL version 3 that provides
     communications privacy over the Internet.  Applications can
     communicate without eavesdropping, tampering, or message forgery.

     3.3 RFC 1847 MIME Security Multiparts [6]

     This document defines security multiparts for MIME:
     multipart/encrypted and multipart/signed.

     3.4 RFC 1892 Multipart/report [10]

     This RFC defines the use of the multipart/report content type,
     something that the MDN draft (fajman) builds upon.

     3.5 RFC 1767 EDI Content [2]

     This RFC defines the use of content type "application" for ANSI
     X12 (application/EDI-X12), EDIFACT (application/EDIFACT) and
     mutually defined EDI (application/EDI-Consent).

     3.6 RFC 2015 PGP/MIME [4]

     This RFC defines the use of content types
     "multipart/encrypted", "multipart/signed", "application/pgp
     encrypted" and "application/pgp-signature" for defining MIME PGP
     content.

     3.7 RFC 2045, 2046, and 2049 MIME [1]

     These are the basic MIME standards, upon which all MIME related RFCs
     build, including this one.  Key contributions include definition of
     "content type", "sub-type" and "multipart", as well as encoding
     guidelines,  which establishes 7-bit US-ASCII as the canonical
     character set to be used in Internet messaging.

     3.8 Internet draft (fajman): Message Disposition Notification [5]

     This Internet draft defines how a message disposition notification
     (MDN) is requested, and the format and syntax of the MDN. The MDN
     is the basis upon which receipts and signed receipts are defined
     in this and the "Requirements" specification.

     3.9 Internet draft (dusse): S/MIME Message Specification [8]
     This specification describes how MIME shall carry PKCS7
     envelopes.

     3.10 Internet draft (shih): MIME-based Secure EDI [12]
     This applicability statement describes security patterns,
     MIME content types, and acknowledgement policies and
     mechanisms for EDI or business data transport.


4. Comparison of HTTP and SMTP based transport

    The major difference between HTTP and SMTP transport for secure
    EDI is found in the persistence of the connection over the send
    and reply transaction. SMTP may involve mail relays; HTTP
    may involve intermediate proxies. Likewise, SMTP MTAs must invoke
    user agents to handle messages, and HTTP servers handle
    the POST request via a cooperating thread or process. For HTTP
    version 1.1, TCP persistent connections are the default, ( [11]
    sections 8.1.2, 8.2, and 19.7.1).

    A number of other differences exist because HTTP does not
    conform to MIME [1] as used in SMTP transport. Relevant
    differences are summarized below.

  4.1 Unused MIME headers and operations

   4.1.1  Content-Transfer-Encoding not used in HTTP transport

    Because HTTP, unlike SMTP, does not have an early history
    involving 7-bit restriction, there is no need to use
    the Content Transfer Encodings of MIME [1]. This difference
    is discussed in [11] section 19.4.4.

   4.1.2  Epilogue must be empty

    The EBNF for a multipart [1] RFC 2046, section 5.1.1 allows
    a multipart to have trailing octets after the close delimiter.
    In [11] section 3.7.2, it is explicitly noted that multiparts
    must have null epilogues.

   4.1.3  Lengthy message bodies

    In [12], section 5.4.1, options for large file processing are
    discussed for SMTP transport. For HTTP, large files should
    be handled correctly by the TCP layer. However, [11] sections
    3.5 and 3.6 discuss some options for compressing or chunking
    entities to be transferred. Section 8.1.2.2 discusses a
    pipelining option that may be useful for segmenting large
    amounts of data.

  4.2 Differences in MIME or other headers or parameters used

   4.2.1  Content-Length

    Because connections are persistent, closing a connection
    cannot be used to indicate the end of an entity. Therefore,
    [11] sections 4.4 and 14.14 indicate the need for a
    Content-Length entity header in a request. In MIME,
    Content-Length is not normally used.

   4.2.2  Disposition-notification-to

    In MIME, a value is needed in order to mail the
    message disposition notification to an address.

    In HTTP, a value is not needed because the reply
    goes back as an "immediate" response, using the
    existing TCP connection. A good value to use would
    be a technical or administrative contact email address.
    The header itself must be present.


   4.2.3  To, Final Recipient, and Original Recipient

    The "To" is optional in the POST request.

    If present, it should be used as the Final-Recipient value
    if request generated. If absent, Final-Recipient value may
    be the signer email address for unsigned receipts or
    a technical or administrative contact email address.

    The final and original recipient distinction should not
    arise for HTTP transport.

   4.2.4  Message-Id and Original-Message-Id

   In SMTP, required and useful for reconciliation of MDN receipt
   with original message.

   In HTTP, not required but could be useful for reconciliation


   4.2.5 Host header

    The host request header field must be included in the
    POST request made when sending business data. This field
    is to allow one server IP address to service multiple
    hostnames, and potentially conserve IP addresses.
    See [11], sections 14.23 and 19.5.1.


5. Acknowledgments

6. References

[1]  N. Borenstein,  N.Freed, "Multipurpose Internet Mail Extensions (MIME)
     Part One: Format of Internet Message Bodies", RFC 2045,
     December 02, 1996.

     N. Borenstein, N.Freed, "Multipurpose Internet Mail Extensions (MIME)
     Part Two: Media Types", RFC 2046, December 02, 1996.

     N. Borenstein, N.Freed, "Multipurpose Internet Mail Extensions (MIME)
     Part Five: Conformance Criteria and Examples", RFC 2049 , December 02,
     1996.

[2]  D. Crocker, "MIME Encapsulation of EDI Objects",  RFC 1767,  March
     2, 1995.

[3]  D. Crocker, "Standard for the Format of ARPA Internet Text
     Messages", STD 11,  RFC 822,  August 13, 1982.

[4]  M. Elkins, "MIME Security With Pretty Good Privacy (PGP)",  RFC
     2015, Sept. 1996.

[5]  R. Fajman, "An Extensible Message Format for Message Disposition
     Notifications", draft-ietf-receipt-mdn-04.txt, June 14, 1997.

[6]  J. Galvin, S. Murphy, S. Crocker, N. Freed,  "Security Multiparts
     for MIME: Multipart/Signed and Multipart/Encrypted", RFC 1847, Oct.
     3, 1995

[7]  J. Postel, "Simple Mail Transfer Protocol",  STD 10, RFC 821,
     August 1, 1982.

[8]  S. Dusse, "S/MIME Message Specification; PKCS Security
     Services for MIME", Internet draft: draft-dusse-mime-msg-spec
     00.txt

[9]  C. Shih, "Requirements for Interoperable Internet EDI",
       Internet draft: draft-ietf-ediint-req03.txt  July 1997.

[10] G. Vaudreuil, "The Multipart/Report Content Type for the Reporting
     of Mail System Administrative Messages",  RFC 1892,
     January 15, 1996.

[11] R. Fielding, J.Gettys, J. Mogul, H. Frystyk, T. Berners-Lee,
     "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2068,
     January 1997.

[12] C. Shih, "MIME-based Secure EDI", Internet draft:
     draft-ietf-ediint-as1-04.txt,


[13] T. Dierks, "The TLS Protocol, Version 1.0,"  Internet draft:
     draft-ietf-tls-protocol-04.txt, April 28, 1997.


7.  Authors' Addresses

Chuck Shih
chucks@actracorp.com
Actra Corp.
610 East Caribbean Drive
Sunnyvale, CA 94089 USA

Dale Moberg
dale_moberg@stercomm.com
Sterling Commerce
4600 Lakehurst Ct.
Dublin, OH 43016 USA

Rik Drummond
drummond@onramp.com
The Drummond Group
5008 Bentwood Ct.
Ft. Worth, TX 76132 USA


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