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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">John,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal">> I can then sign exactly one document (the "template" XRD), and<o:p></o:p></p>
<p class="MsoNormal">> point to it from all of my 1M resources.<o:p></o:p></p>
<p class="MsoNormal">> I mark it as cacheable for 1 week and it is used for billions of metadata lookups<o:p></o:p></p>
<p class="MsoNormal">> without any HTTP overhead. Life is good.<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">Sounds good, but… something is missing.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">Signing the “template XRD” doesn’t secure the link from the user’s OpenID identifier to the XRD.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">The signed template XRD securely tells an RP which OP
<b>the signer</b> says is authoritative for the user’s OpenID identifier.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">This is not the same as the OpenID identifier itself securely saying which OP is authoritative.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">To get the HTTP cache goodness the template XRD probably needs to be delivered over HTTP, not HTTPS.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">Consequently, the 1M user account OpenID URIs need to return, say:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"> Link: <http://example.com/template.xrd>; rel=”describedby”<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">If an attacker tampers with the RP’s subsequent unsecured HTTP request for template.xrd, and returns different meta-data — how can the RP tell it isn’t legitimate?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">The 1M user account OpenID URIs have not indicated that:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">1) the XRD needs to be signed; or<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">2) which signer(s) are legitimate.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">We either need to:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">* change the theory behind OpenID so one resource (eg template XRD) can say “I’m authoritative for all, say,
<a href="http://example.com/user/*">http://example.com/user/*</a> OpenID identifiers — so RPs don’t have to contact those URI (eg they will never delegate)”; or<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D">* define a new type of link (eg httpi://…) which means “use http, but check the integrity” (it could mean “use http and only accept a signed response, or
use https — the client can choose”).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="FR" style="font-family:"Arial","sans-serif";
color:#1F497D">James Manger</span></b><span style="color:#1F497D">
<br>
<a href="mailto:James.H.Manger@team.telstra.com"><span lang="FR" style="font-size:10.0pt;font-family:"Arial","sans-serif"">James.H.Manger@team.telstra.com</span></a>
<br>
</span><span style="font-size:10.0pt;font-family:"Arial","sans-serif";
color:#1F497D">Identity and security team</span><span style="color:#1F497D">
</span><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D">—</span><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D"> Chief Technology Office</span><span style="color:#1F497D">
</span><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:#1F497D">—</span><span style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D"> Telstra</span><span style="color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D"><o:p> </o:p></span></p>
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