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<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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<p class="MsoNormal" style="margin-left:30.5pt"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Jacob Hoffman-Andrews [mailto:jsha@letsencrypt.org]
<br>
<b>Sent:</b> Wednesday, October 4, 2017 4:17 PM<br>
<b>To:</b> Doug Beattie <doug.beattie@globalsign.com>; CA/Browser Forum Public Discussion List <public@cabforum.org><br>
<b>Cc:</b> geoffk@apple.com<br>
<b>Subject:</b> Re: [cabfpub] CAA look up failures and retry logic<o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-left:30.5pt"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt">You make a good point. To reiterate the language from the BRs:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt">> CAs are permitted to treat a record lookup failure as permission to issue if:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt">> • the failure is outside the CA's infrastructure;<o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt">> • the lookup has been retried at least once; and<br>
> • the domain's zone does not have a DNSSEC validation chain to the ICANN root. <o:p></o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt">Specifically, this talks about a single record lookup failure, but allows treating that as permission to issue. I think the behavior we'd really like here is to treat a record lookup failure as equivalent to a
successful, empty response if those conditions are met. That way, for instance if a CAA lookup for "<a href="http://nonexistent.example.com">nonexistent.example.com</a>" returns NXDOMAIN, the CA is still required to attempt looking up a CAA record for "<a href="http://example.com">example.com</a>".<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-left:30.5pt">So I agree that your "most likely" option is the ideal, and is what CAs should be implementing to be conservative, but the BRs do not currently say that. I would support a ballot to amend it.<o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">CAs might be motivated to run into fewer failures and to issue more certificates, so being conservative might not be what’s happening. I know we’re blocking
many more requests than some other CAs (mutual customers have informed us), which is driving this line of questioning for clarity.
<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">What constitutes a failure?<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">How are failures retried and processed?<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><![if !supportLists]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><span style="mso-list:Ignore">-<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">What’s an acceptable timeout period?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">None of this is called out in the BRs or RFC.<o:p></o:p></span></p>
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