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RFC draft for revising RFC3230 under RFC 7231
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There has to be one entity for each item to be referenced.
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<rfc category="info" docName="draft-ietf-xml2rfc-template-06" ipr="trust200902">
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<front>
<!-- The abbreviated title is used in the page header - it is only necessary if the
full title is longer than 39 characters -->
<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>
<!-- uri and facsimile elements may also be added -->
</address>
</author>
<date year="2010" />
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<area>General</area>
<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obsoleting Content-MD5 and making "instance" outdated .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>
</section>
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</list> You can write text here as well.</t>
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<artwork align="left"><![CDATA[
+-----------------------+
| Use XML, be Happy :-) |
|_______________________|
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<t>First, a short item.</t>
<t>Second, a longer list item.<vspace blankLines="1" /> And
something that looks like a separate pararaph..</t>
</list></t>
<t>Simple indented paragraph using the "empty" style: <list
hangIndent="10" style="empty">
<t>The quick, brown fox jumped over the lazy dog and lived to fool
many another hunter in the great wood in the west.</t>
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<section title="Numbering Lists across Lists and Sections">
<t>Numbering items continuously although they are in separate
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<section title="Where the List Numbering Continues">
<t>List continues here.</t>
<t>Third list: <list counter="reqs" hangIndent="4" style="format R%d">
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<t>#8</t>
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</list> The end of the list.</t>
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<section anchor="Acknowledgements" title="Acknowledgements">
<t>This template was derived from an initial version written by Pekka
Savola and contributed by him to the xml2rfc project.</t>
<t>This document is part of a plan to make xml2rfc indispensable <xref
target="DOMINATION"></xref>.</t>
</section>
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<section anchor="IANA" title="IANA Considerations">
<t>This memo includes no request to IANA.</t>
<t>All drafts are required to have an IANA considerations section (see
<xref target="RFC5226">Guidelines for Writing an IANA Considerations Section in RFCs</xref> for a guide). If the draft does not require IANA to do
anything, the section contains an explicit statement that this is the
case (as above). If there are no requirements for IANA, the section will
be removed during conversion into an RFC by the RFC Editor.</t>
</section>
<section anchor="Security" title="Security Considerations">
<t>All drafts are required to have a security considerations section.
See <xref target="RFC3552">RFC 3552</xref> for a guide.</t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
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<date year="2006" />
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<front>
<title>Ultimate Plan for Taking Over the World</title>
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<organization>Mad Dominators, Inc.</organization>
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<date year="1984" />
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</references>
<section anchor="app-additional" title="Additional Stuff">
<t>This becomes an Appendix.</t>
</section>
<!-- Change Log
v00 2006-03-15 EBD Initial version
</back>
</rfc>
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