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<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">I might have found part of the solution. After some more digging, I saw that at least the SAMLRequest=... page on the IdP sets a Cache-Control: no store header. Which is of course perfect. My theory
is that Chrome prefetches this page, refuses to store because of the header, and then needs to request it again immediately.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">So what I do now is for these type of requests, which are unique anyway (so no caching issues can occur), I remove the header Cache-Control on the response.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Messy but it’s better than what’s happening now.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D">Vincent<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="mso-fareast-language:NL-BE">From:</span></b><span lang="EN-US" style="mso-fareast-language:NL-BE"> users <users-bounces@shibboleth.net>
<b>On Behalf Of </b>Feyaerts Vincent<br>
<b>Sent:</b> woensdag 26 september 2018 11:13<br>
<b>To:</b> users@shibboleth.net<br>
<b>Subject:</b> Issues with Chrome "prefetching" our IdP pages<o:p></o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We have a set-up consisting of ADFS+Shibboleth 3 IdP. ADFS is the slave SP. Both are load balanced behind a Big-IP F5 LTM. Our problem is not really related to this set-up. I think it might occur in any normal IdP deployment.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The Shibboleth IdP back-end logs are full of messages like:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><i><span lang="EN-US">org.opensaml.messaging.handler.MessageHandlerException: Rejecting replayed message ID 'id-f7e02f5c-843f-4d3d-88af-168b8a79653e' from issuer
</span></i><a href="http://url/adfs/services/trust"><i><span lang="EN-US">http://url/adfs/services/trust</span></i></a><i><span lang="EN-US"><o:p></o:p></span></i></p>
<p class="MsoNormal"><i><span lang="EN-US"> at org.opensaml.saml.common.binding.security.impl.MessageReplaySecurityHandler.doInvoke(MessageReplaySecurityHandler.java:157)<o:p></o:p></span></i></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I checked our logs of the load balancer, the client does indeed request the URL with the SAMLRequest referencing that ID twice. Now, it appears one of those requests has a header “Purpose prefetch”. This is a Google Chrome
header. Now, I have no idea why it would prefetch these pages but it does.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Technically speaking this might be a Chrome problem, but it interferes with a normal Shibboleth IdP from working, and I hope somebody else has found a way to fix this on the IdP, because I can’t change Chrome.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">I tried sending a 403 as a response to the Prefetch request, but then Chrome just stops and won’t ask again.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Vincent Feyaerts<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
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