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<p class="MsoNormal">EAP call notes 20-Jul-17<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Mike Jones<o:p></o:p></p>
<p class="MsoNormal">Brian Campbell<o:p></o:p></p>
<p class="MsoNormal">Nat Sakimura<o:p></o:p></p>
<p class="MsoNormal">John Bradley<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Agenda<o:p></o:p></p>
<p class="MsoNormal"> Detecting Downplay Attacks<o:p></o:p></p>
<p class="MsoNormal"> Crypto Agility for the "tbh" Hash Function<o:p></o:p></p>
<p class="MsoNormal"> Clustered OAuth Web Server Clients<o:p></o:p></p>
<p class="MsoNormal"> OAuth Token Binding Security Considerations<o:p></o:p></p>
<p class="MsoNormal"> Next Call<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Detecting Downplay Attacks<o:p></o:p></p>
<p class="MsoNormal"> Brian: The Security Considerations language currently seems possibly overly specific<o:p></o:p></p>
<p class="MsoNormal"> Paragraph 3 in Section 4 describes indeterminate cases as likely attacks<o:p></o:p></p>
<p class="MsoNormal"> John: If you're man-in-the-middled, the attacker will change the browser string to one that doesn't support Token Binding<o:p></o:p></p>
<p class="MsoNormal"> Brian: The on/off metadata that we currently have may be useful but is not sufficient<o:p></o:p></p>
<p class="MsoNormal"> John: An indeterminate state can occur if the client negotiates token binding and sends a referred token binding<o:p></o:p></p>
<p class="MsoNormal"> but receives an unbound ID token<o:p></o:p></p>
<p class="MsoNormal"> This could happen due to algorithm mismatches - although servers are required to support all the algorithms<o:p></o:p></p>
<p class="MsoNormal"> We should say in the spec that this should be rejected<o:p></o:p></p>
<p class="MsoNormal"> Mike: There may be deployments in which specific knowledge of capabilities of the participants is used<o:p></o:p></p>
<p class="MsoNormal"> John: If the OP doesn't receive a Token Binding, it may need to inform the user to choose an appropriate browser or that something bad is happening<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Crypto Agility for the "tbh" Hash Function<o:p></o:p></p>
<p class="MsoNormal"> We should add similar language as that used for "x5t" and "x5t#S256"<o:p></o:p></p>
<p class="MsoNormal"> Brian will take a crack at this (he's already doing this for the OAuth MTLS draft)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Clustered OAuth Web Server Clients<o:p></o:p></p>
<p class="MsoNormal"> Brian talked about Token Binding for clustered Web Server clients<o:p></o:p></p>
<p class="MsoNormal"> He's worried that Refresh Token Token Binding may be problematic for clustered deployments<o:p></o:p></p>
<p class="MsoNormal"> The client would have to share Token Binding keys across instances in clustered deployments<o:p></o:p></p>
<p class="MsoNormal"> Brian thinks there may be need to be a way to allow Web Server Clients to bind access tokens but not refresh tokens<o:p></o:p></p>
<p class="MsoNormal"> The best way to indicate this is probably client metadata<o:p></o:p></p>
<p class="MsoNormal"> A dynamic parameter to turn it off seems like it would be a bad idea<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">OAuth Token Binding Security Considerations<o:p></o:p></p>
<p class="MsoNormal"> There are likely similar wording issues in the OAuth Token Binding Security Considerations language<o:p></o:p></p>
<p class="MsoNormal"> Brian will have a look at this<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Next Call<o:p></o:p></p>
<p class="MsoNormal"> Our next call is Thursday, August 3rd, 2017 at 8am Pacific<o:p></o:p></p>
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