Ignore:
Timestamp:
Dec 31, 2012, 2:51:33 AM (7 years ago)
Author:
fielding@…
Message:

update the description of Referer to current practice and actual security concerns

File:
1 edited

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  • draft-ietf-httpbis/latest/p2-semantics.html

    r2071 r2072  
    449449  }
    450450  @bottom-center {
    451        content: "Expires July 3, 2013";
     451       content: "Expires July 4, 2013";
    452452  }
    453453  @bottom-right {
     
    495495      <meta name="dct.creator" content="Reschke, J. F.">
    496496      <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-p2-semantics-latest">
    497       <meta name="dct.issued" scheme="ISO8601" content="2012-12-30">
     497      <meta name="dct.issued" scheme="ISO8601" content="2012-12-31">
    498498      <meta name="dct.replaces" content="urn:ietf:rfc:2616">
    499499      <meta name="dct.abstract" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypertext information systems. This document defines the semantics of HTTP/1.1 messages, as expressed by request methods, request header fields, response status codes, and response header fields, along with the payload of messages (metadata and body content) and mechanisms for content negotiation.">
     
    523523            <tr>
    524524               <td class="left">Intended status: Standards Track</td>
    525                <td class="right">December 30, 2012</td>
     525               <td class="right">December 31, 2012</td>
    526526            </tr>
    527527            <tr>
    528                <td class="left">Expires: July 3, 2013</td>
     528               <td class="left">Expires: July 4, 2013</td>
    529529               <td class="right"></td>
    530530            </tr>
     
    554554         in progress”.
    555555      </p>
    556       <p>This Internet-Draft will expire on July 3, 2013.</p>
     556      <p>This Internet-Draft will expire on July 4, 2013.</p>
    557557      <h1><a id="rfc.copyrightnotice" href="#rfc.copyrightnotice">Copyright Notice</a></h1>
    558558      <p>Copyright © 2012 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
     
    835835         in <a href="p1-messaging.html#uri" title="Uniform Resource Identifiers">Section 2.7</a> of <a href="#Part1" id="rfc.xref.Part1.4"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>.
    836836      </p>
    837       <p id="rfc.section.2.p.2">When a client constructs an HTTP/1.1 request message, it sends the "target URI" in one of various forms, as defined in (<a href="p1-messaging.html#request-target" title="Request Target">Section 5.3</a> of <a href="#Part1" id="rfc.xref.Part1.5"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>). When a request is received, the server reconstructs an "effective request URI" for the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.6"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>).
     837      <p id="rfc.section.2.p.2">When a client constructs an HTTP/1.1 request message, it sends the <a href="p1-messaging.html#target-resource" class="smpl">target URI</a> in one of various forms, as defined in (<a href="p1-messaging.html#request-target" title="Request Target">Section 5.3</a> of <a href="#Part1" id="rfc.xref.Part1.5"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>). When a request is received, the server reconstructs an <a href="p1-messaging.html#effective.request.uri" class="smpl">effective request URI</a> for the target resource (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.6"><cite title="Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing">[Part1]</cite></a>).
    838838      </p>
    839839      <p id="rfc.section.2.p.3">One design goal of HTTP is to separate resource identification from request semantics, which is made possible by vesting the
     
    18221822  <a href="#header.accept" class="smpl">accept-ext</a>     = <a href="#imported.abnf" class="smpl">OWS</a> ";" <a href="#imported.abnf" class="smpl">OWS</a> <a href="#imported.abnf" class="smpl">token</a> [ "=" <a href="#imported.abnf" class="smpl">word</a> ]
    18231823</pre><p id="rfc.section.5.3.2.p.3">The asterisk "*" character is used to group media types into ranges, with "*/*" indicating all media types and "type/*" indicating
    1824          all subtypes of that type. The media-range <em class="bcp14">MAY</em> include media type parameters that are applicable to that range.
    1825       </p>
    1826       <p id="rfc.section.5.3.2.p.4">Each media-range <em class="bcp14">MAY</em> be followed by one or more accept-params, beginning with the "q" parameter for indicating a relative weight, as defined in <a href="#quality.values" title="Quality Values">Section&nbsp;5.3.1</a>. The first "q" parameter (if any) separates the media-range parameter(s) from the accept-params.
     1824         all subtypes of that type. The media-range can include media type parameters that are applicable to that range.
     1825      </p>
     1826      <p id="rfc.section.5.3.2.p.4">Each media-range might be followed by zero or more applicable media type parameters (e.g., <a href="#charset" class="smpl">charset</a>), an optional "q" parameter for indicating a relative weight (<a href="#quality.values" title="Quality Values">Section&nbsp;5.3.1</a>), and then zero or more extension parameters. The "q" parameter is necessary if any accept-ext are present, since it acts
     1827         as a separator between the two parameter sets.
    18271828      </p>
    18281829      <div class="note" id="rfc.section.5.3.2.p.5">
     
    20692070      <div id="rfc.iref.r.2"></div>
    20702071      <h3 id="rfc.section.5.5.2"><a href="#rfc.section.5.5.2">5.5.2</a>&nbsp;<a id="header.referer" href="#header.referer">Referer</a></h3>
    2071       <p id="rfc.section.5.5.2.p.1">The "Referer" [sic] header field allows the client to specify the URI of the resource from which the target URI was obtained
    2072          (the "referrer", although the header field is misspelled.).
    2073       </p>
    2074       <p id="rfc.section.5.5.2.p.2">The Referer header field allows servers to generate lists of back-links to resources for interest, logging, optimized caching,
    2075          etc. It also allows obsolete or mistyped links to be traced for maintenance. Some servers use Referer as a means of controlling
    2076          where they allow links from (so-called "deep linking"), but legitimate requests do not always contain a Referer header field.
    2077       </p>
    2078       <p id="rfc.section.5.5.2.p.3">If the target URI was obtained from a source that does not have its own URI (e.g., input from the user keyboard), the Referer
    2079          field <em class="bcp14">MUST</em> either be sent with the value "about:blank", or not be sent at all. Note that this requirement does not apply to sources with
    2080          non-HTTP URIs (e.g., FTP).
     2072      <p id="rfc.section.5.5.2.p.1">The "Referer" [sic] header field allows the user agent to specify a URI reference for the resource from which the <a href="p1-messaging.html#target-resource" class="smpl">target URI</a> was obtained (i.e., the "referrer", though the field name is misspelled). A user agent <em class="bcp14">MUST</em> exclude any fragment or userinfo components <a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a> when generating the Referer field value.
    20812073      </p>
    20822074      <div id="rfc.figure.u.36"></div><pre class="inline"><span id="rfc.iref.g.35"></span>  <a href="#header.referer" class="smpl">Referer</a> = <a href="#imported.abnf" class="smpl">absolute-URI</a> / <a href="#imported.abnf" class="smpl">partial-URI</a>
    2083 </pre><p id="rfc.section.5.5.2.p.5">Example:</p>
     2075</pre><p id="rfc.section.5.5.2.p.3">Referer allows servers to generate back-links to other resources for simple analytics, logging, optimized caching, etc. It
     2076         also allows obsolete or mistyped links to be found for maintenance. Some servers use Referer as a means of denying links from
     2077         other sites (so-called "deep linking") or restricting cross-site request forgery (CSRF), but not all requests contain a Referer
     2078         header field.
     2079      </p>
     2080      <p id="rfc.section.5.5.2.p.4">Example:</p>
    20842081      <div id="rfc.figure.u.37"></div><pre class="text">  Referer: http://www.example.org/hypertext/Overview.html
    2085 </pre><p id="rfc.section.5.5.2.p.7">If the field value is a relative URI, it <em class="bcp14">SHOULD</em> be interpreted relative to the effective request URI. The URI <em class="bcp14">MUST NOT</em> include a fragment. See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;9.4</a> for security considerations.
     2082</pre><p id="rfc.section.5.5.2.p.6">If the target URI was obtained from a source that does not have its own URI (e.g., input from the user keyboard, or an entry
     2083         within the user's bookmarks/favorites), the user agent <em class="bcp14">MUST</em> either exclude Referer or send it with a value of "about:blank".
     2084      </p>
     2085      <p id="rfc.section.5.5.2.p.7">The Referer field has the potential to reveal information about the request context or browsing history of the user, which
     2086         is a privacy concern if the referring resource's identifier reveals personal information (such as an account name) or a resource
     2087         that is supposed to be confidential (such as behind a firewall or internal to a secured service). Most general-purpose user
     2088         agents do not send the Referer header field when the referring resource is a local "file" or "data" URI. A user agent <em class="bcp14">SHOULD NOT</em> send a <a href="#header.referer" class="smpl">Referer</a> header field in a (non-secure) HTTP request if the referring page was received with a secure protocol. See <a href="#encoding.sensitive.information.in.uris" title="Encoding Sensitive Information in URIs">Section&nbsp;9.4</a> for additional security considerations.
     2089      </p>
     2090      <p id="rfc.section.5.5.2.p.8">Some intermediaries have been known to indiscriminately remove Referer header fields from outgoing requests. This has the
     2091         unfortunate side-effect of interfering with protection against CSRF attacks, which can be far more harmful to their users.
     2092         Intermediaries and user agent extensions that wish to limit information disclosure in Referer ought to restrict their changes
     2093         to specific edits, such as replacing internal domain names with pseudonyms or truncating the query and/or path components.
     2094         Intermediaries <em class="bcp14">SHOULD NOT</em> modify or delete the Referer field when the field value shares the same scheme and host as the request target.
    20862095      </p>
    20872096      <div id="rfc.iref.u.1"></div>
     
    29082917      </p>
    29092918      <div id="rfc.figure.u.51"></div><pre class="inline"><span id="rfc.iref.g.56"></span>  <a href="#header.location" class="smpl">Location</a> = <a href="#imported.abnf" class="smpl">URI-reference</a>
    2910 </pre><p id="rfc.section.7.1.2.p.3">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-5">Section 5</a>). If the original URI, as navigated to by the user agent, contains a fragment identifier, and the Location value does not,
     2919</pre><p id="rfc.section.7.1.2.p.3">The field value consists of a single URI-reference. When it has the form of a relative reference (<a href="#RFC3986" id="rfc.xref.RFC3986.2"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-4.2">Section 4.2</a>), the final value is computed by resolving it against the effective request URI (<a href="#RFC3986" id="rfc.xref.RFC3986.3"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>, <a href="http://tools.ietf.org/html/rfc3986#section-5">Section 5</a>). If the original URI, as navigated to by the user agent, contains a fragment identifier, and the Location value does not,
    29112920         then the original URI's fragment identifier is appended to the Location value.
    29122921      </p>
     
    38003809      </p>
    38013810      <h2 id="rfc.section.9.4"><a href="#rfc.section.9.4">9.4</a>&nbsp;<a id="encoding.sensitive.information.in.uris" href="#encoding.sensitive.information.in.uris">Encoding Sensitive Information in URIs</a></h2>
    3802       <p id="rfc.section.9.4.p.1">Because the source of a link might be private information or might reveal an otherwise private information source, it is strongly
    3803          recommended that the user be able to select whether or not the <a href="#header.referer" class="smpl">Referer</a> field is sent. For example, a browser client could have a toggle switch for browsing openly/anonymously, which would respectively
    3804          enable/disable the sending of Referer and From information.
    3805       </p>
    3806       <p id="rfc.section.9.4.p.2">Clients <em class="bcp14">SHOULD NOT</em> include a <a href="#header.referer" class="smpl">Referer</a> header field in a (non-secure) HTTP request if the referring page was transferred with a secure protocol.
     3811      <p id="rfc.section.9.4.p.1">URIs are intended to be shared, not secured, even when they identify secure resources. URIs are often shown on displays, added
     3812         to templates when a page is printed, and stored in a variety of unprotected bookmark lists. It is therefore unwise to include
     3813         information within a URI that is sensitive, personally identifiable, or a risk to disclose.
     3814      </p>
     3815      <p id="rfc.section.9.4.p.2">Since the Referer header field tells a target site about the context that resulted in a request, it has the potential to reveal
     3816         information about the user's immediate browsing history and any personal information that might be found in the referring
     3817         resource's URI. Further discussion of Referer considerations can be found in <a href="#header.referer" id="rfc.xref.header.referer.3" title="Referer">Section&nbsp;5.5.2</a>.
    38073818      </p>
    38083819      <p id="rfc.section.9.4.p.3">Authors of services <em class="bcp14">SHOULD NOT</em> use GET-based forms for the submission of sensitive data because that data will be placed in the request-target. Many existing
    38093820         servers, proxies, and user agents log or display the request-target in places where it might be visible to third parties.
    3810          Such services can use POST-based form submission instead.
     3821         Such services ought to use POST-based form submission instead.
    38113822      </p>
    38123823      <h2 id="rfc.section.9.5"><a href="#rfc.section.9.5">9.5</a>&nbsp;<a id="location.spoofing-leakage" href="#location.spoofing-leakage">Location Header Fields: Spoofing and Information Leakage</a></h2>
     
    41534164      <p id="rfc.section.C.p.16">Requirements for sending the Date header field have been clarified. (<a href="#header.date" id="rfc.xref.header.date.4" title="Date">Section&nbsp;7.1.1.2</a>)
    41544165      </p>
    4155       <p id="rfc.section.C.p.17">The <a href="#header.referer" class="smpl">Referer</a> header field can now have a value of "about:blank" as an alternative to not sending a Referer header field. (<a href="#header.referer" id="rfc.xref.header.referer.3" title="Referer">Section&nbsp;5.5.2</a>)
     4166      <p id="rfc.section.C.p.17">The <a href="#header.referer" class="smpl">Referer</a> header field can now have a value of "about:blank" as an alternative to not sending a Referer header field. (<a href="#header.referer" id="rfc.xref.header.referer.4" title="Referer">Section&nbsp;5.5.2</a>)
    41564167      </p>
    41574168      <p id="rfc.section.C.p.18">The <a href="#status.201" class="smpl">201 (Created)</a> status code can indicate that more than one resource has been created (as well as just one).
     
    46534664            </li>
    46544665            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul>
    4655                   <li>Referer header field&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">5.5</a>, <a href="#rfc.iref.r.2"><b>5.5.2</b></a>, <a href="#rfc.xref.header.referer.2">8.3.2</a>, <a href="#rfc.xref.header.referer.3">C</a></li>
     4666                  <li>Referer header field&nbsp;&nbsp;<a href="#rfc.xref.header.referer.1">5.5</a>, <a href="#rfc.iref.r.2"><b>5.5.2</b></a>, <a href="#rfc.xref.header.referer.2">8.3.2</a>, <a href="#rfc.xref.header.referer.3">9.4</a>, <a href="#rfc.xref.header.referer.4">C</a></li>
    46564667                  <li>representation&nbsp;&nbsp;<a href="#rfc.iref.r.1">3</a></li>
    46574668                  <li><em>REST</em>&nbsp;&nbsp;<a href="#rfc.xref.REST.1">3</a>, <a href="#rfc.xref.REST.2">4.1</a>, <a href="#REST"><b>11.2</b></a></li>
     
    47014712                  </li>
    47024713                  <li><em>RFC2978</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2978.1">3.1.1.2</a>, <a href="#RFC2978"><b>11.2</b></a></li>
    4703                   <li><em>RFC3986</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">7.1.2</a>, <a href="#rfc.xref.RFC3986.2">7.1.2</a>, <a href="#RFC3986"><b>11.1</b></a><ul>
    4704                         <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">7.1.2</a></li>
    4705                         <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.2">7.1.2</a></li>
     4714                  <li><em>RFC3986</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">5.5.2</a>, <a href="#rfc.xref.RFC3986.2">7.1.2</a>, <a href="#rfc.xref.RFC3986.3">7.1.2</a>, <a href="#RFC3986"><b>11.1</b></a><ul>
     4715                        <li><em>Section 4.2</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.2">7.1.2</a></li>
     4716                        <li><em>Section 5</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.3">7.1.2</a></li>
    47064717                     </ul>
    47074718                  </li>
     
    47564767            </li>
    47574768            <li><a id="rfc.index.T" href="#rfc.index.T"><b>T</b></a><ul>
    4758                   <li>TRACE method&nbsp;&nbsp;<a href="#rfc.xref.TRACE.1">4.1</a>, <a href="#rfc.iref.t.1"><b>4.3.8</b></a>, <a href="#rfc.xref.TRACE.2">5.1.1</a>, <a href="#rfc.xref.TRACE.3">8.1.3</a>, <a href="#rfc.xref.TRACE.4">9.3</a>, <a href="#rfc.extref.t.48">C</a>, <a href="#rfc.xref.TRACE.5">C</a></li>
     4769                  <li>TRACE method&nbsp;&nbsp;<a href="#rfc.xref.TRACE.1">4.1</a>, <a href="#rfc.iref.t.1"><b>4.3.8</b></a>, <a href="#rfc.xref.TRACE.2">5.1.1</a>, <a href="#rfc.xref.TRACE.3">8.1.3</a>, <a href="#rfc.xref.TRACE.4">9.3</a>, <a href="#rfc.extref.t.50">C</a>, <a href="#rfc.xref.TRACE.5">C</a></li>
    47594770               </ul>
    47604771            </li>
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