RFC draft for revising RFC3230 under RFC 7231

draft-polli-digest-header.xml

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 <!-- ***** FRONT MATTER ***** -->

 <front>
   <!-- The abbreviated title is used in the page header - it is only necessary if the
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   <title abbrev="Abbreviated Title">Representation Digests in HTTP</title>

   <!-- add 'role="editor"' below for the editors if appropriate -->

   <!-- Another author who claims to be an editor -->

   <author fullname="Roberto Polli" initials="R.P." role="editor"
           surname="Polli">
     <organization>Team Digitale</organization>

     <address>
       <postal>
         <street></street>
         <!-- Reorder these if your country does things differently -->
         <city>Latina</city>
         <region></region>
         <code></code>
         <country>IT</country>
       </postal>
       <phone></phone>
       <email>robipolli@gmail.com</email>
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     </address>
   </author>

   <date year="2010" />

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   <workgroup>Internet Engineering Task Force</workgroup>

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   <abstract>
     <t>
       <xref target="RFC3230">RFC 3230</xref> defined the Digest and Want-Digest header fields for HTTP that allows the client
 and server to negotiate an integrity checksum of the exchanged data.
That specification fixed some known limitations of Content-MD5 introducing
the concept of "instance".

As of today, <xref target="RFC7231">RFC 7231</xref> defines a new semantic for http
and standardize the concepts of `representation` and `selected representation`, further
obsoleting Content-MD5 and making "instance" outdated .

This document updates the Digest and Want-Digest header field definitions to align with
       <xref target="RFC7231">RFC 7231</xref>  concepts. Changes are semantically compatible with existing implementations and
better cover both the request and response cases.

This document obsoletes <xref
     target="RFC3230">RFC 3230</xref>.
</t>
   </abstract>
 </front>

 <middle>
   <section title="Introduction">
     <t>
          Although HTTP is typically layered over a reliable transport
   protocol, such as TCP, this does not guarantee reliable transport of
   information from sender to recipient.  Various problems, including
   undetected transmission errors, programming errors, corruption of
   stored data, and malicious intervention can cause errors in the
   transmitted information.
    </t>

     <t>
   A common approach to the problem of data integrity in a network
   protocol or distributed system, such as HTTP, is the use of digests,
   checksums, or hash values.  The sender computes a digest and sends it
   with the data; the recipient computes a digest of the received data,
   and then verifies the integrity of this data by comparing the
   digests.
     </t>
     <t>
  The Content-MD5 header field was originally introduced to provide integrity,
       but HTTP/1.1<xref
       target="RFC2119">RFC 7231 appendix-B</xref> obsoleted it:

       <list>
               <t>
  The Content-MD5 header field has been removed because it was
  inconsistently implemented with respect to partial responses.
               </t></list>

</t><t>
       The proposed solution uses the checksum of the selected representation of a resource.
       This approach is more flexible and can be easily adapted to use-cases where the transferred data
       does require some sort of manipulation to be considered a representation (eg. Range Requests RFC 7233).


       This information can be sent:
     <list style="symbols">
       <t>in response to a HEAD request with the same value of the corresponding GET request;</t>
       <t>alongside a 206 (Partial Content) response in Range Requests or similar mechanisms.</t>
     </list>

     Its value can be validated once all representation data has been collected.
     Being calculated on the selected representation, the Digest is tied to the representation-data and the Content-Coding.
     A given resource has thus multiple possible digests dependending on the applied Content-Codings.


     </t>

     <section title="Requirements Language">
       <t>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 <xref
       target="RFC2119">RFC 2119</xref>.</t>
     </section>
   </section>

   <section title="Goals">
     <t>
     The goals of this proposal are:
<list style="numbers">
  <t>Digest coverage for representation data communicated via HTTP</t>
  <t>Support for multiple digest algorithms</t>
  <t>Negotiation of the use of digests</t>
</list>

   The goals do not include:
<list>
  <t>      -  header integrity
         The digest mechanisms described here cover only representation data, and do not protect the integrity of associated
         representation metadata headers or other message headers.
</t>
  <t>      -  authentication
         The digest mechanisms described here are not meant to support
         authentication of the source of a digest or of a message or
         anything else.  These mechanisms, therefore, are not sufficient
         defense against many kinds of malicious attacks.
</t>
  <t>      -  privacy
         Digest mechanisms do not provide message privacy.
</t>
  <t>      -  authorization
         The digest mechanisms described here are not meant to support
         authorization or other kinds of access controls.
</t>
</list>


</t>


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+-----------------------+
| Use XML, be Happy :-) |
|_______________________|
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v00 2006-03-15  EBD   Initial version
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