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    All of that I agree with. Question remains if the server, in its
    response to the client, wants to tell the client it has several of
    the X options found in discovery.<br>
    <br>
     -- Justin<br>
    <br>
    <div class="moz-cite-prefix">On 01/23/2013 12:36 PM, Mike Jones
      wrote:<br>
    </div>
    <blockquote
cite="mid:4E1F6AAD24975D4BA5B168042967394366A765B3@TK5EX14MBXC283.redmond.corp.microsoft.com"
      type="cite">
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      <div>
        <div style="font-family:Calibri,sans-serif; font-size:11pt">I
          agree they're complimentary.<br>
          <br>
          Discovery tells the client what the server can do.  It uses
          that information to pick the option to use that will work for
          both of them, then registers with that option.<br>
          <br>
          -- Mike<br>
          <br>
        </div>
      </div>
      <hr>
      <span style="font-family:Tahoma,sans-serif; font-size:10pt;
        font-weight:bold">From:
      </span><span style="font-family:Tahoma,sans-serif; font-size:10pt">Justin
        Richer</span><br>
      <span style="font-family:Tahoma,sans-serif; font-size:10pt;
        font-weight:bold">Sent:
      </span><span style="font-family:Tahoma,sans-serif; font-size:10pt">1/23/2013
        9:28 AM</span><br>
      <span style="font-family:Tahoma,sans-serif; font-size:10pt;
        font-weight:bold">To:
      </span><span style="font-family:Tahoma,sans-serif; font-size:10pt">Mike
        Jones</span><br>
      <span style="font-family:Tahoma,sans-serif; font-size:10pt;
        font-weight:bold">Cc:
      </span><span style="font-family:Tahoma,sans-serif; font-size:10pt">John
        Bradley; <a class="moz-txt-link-abbreviated" href="mailto:openid-specs-ab@lists.openid.net">openid-specs-ab@lists.openid.net</a></span><br>
      <span style="font-family:Tahoma,sans-serif; font-size:10pt;
        font-weight:bold">Subject:
      </span><span style="font-family:Tahoma,sans-serif; font-size:10pt">Re:
        [Openid-specs-ab] token_endpoint_auth_method Registration
        example error?</span><br>
      <br>
      <div>Not all clients can necessarily use all forms of auth that a
        server supports, so I see the two values as complimentary.<br>
        <br>
         -- Justin<br>
        <br>
        <div class="moz-cite-prefix">On 01/23/2013 12:14 PM, Mike Jones
          wrote:<br>
        </div>
        <blockquote type="cite"><base href="">
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            <p class="MsoNormal"><span style="font-size:11.0pt;
                font-family:"Calibri","sans-serif";
                color:#1F497D">The server expresses what the client
                should do in the discovery phase – not during
                registration.  See the “</span><span style="">token_endpoint_auth_methods_supported</span><span
                style="font-size:11.0pt;
                font-family:"Calibri","sans-serif";
                color:#1F497D">” discovery result parameter in <a
                  moz-do-not-send="true"
                  href="http://openid.net/specs/openid-connect-discovery-1_0-12.html">
http://openid.net/specs/openid-connect-discovery-1_0-12.html</a>.</span></p>
            <p class="MsoNormal"><span style="font-size:11.0pt;
                font-family:"Calibri","sans-serif";
                color:#1F497D"> </span></p>
            <p class="MsoNormal"><span style="font-size:11.0pt;
                font-family:"Calibri","sans-serif";
                color:#1F497D">                                                           
                -- Mike</span></p>
            <p class="MsoNormal"><span style="font-size:11.0pt;
                font-family:"Calibri","sans-serif";
                color:#1F497D"> </span></p>
            <div>
              <div style="border:none; border-top:solid #B5C4DF 1.0pt;
                padding:3.0pt 0in 0in 0in">
                <p class="MsoNormal"><b><span style="font-size:10.0pt;
                      font-family:"Tahoma","sans-serif"">From:</span></b><span
                    style="font-size:10.0pt;
                    font-family:"Tahoma","sans-serif"">
                    John Bradley [<a moz-do-not-send="true"
                      class="moz-txt-link-freetext"
                      href="mailto:ve7jtb@ve7jtb.com">mailto:ve7jtb@ve7jtb.com</a>]
                    <br>
                    <b>Sent:</b> Wednesday, January 23, 2013 9:02 AM<br>
                    <b>To:</b> Justin Richer<br>
                    <b>Cc:</b> Mike Jones; <a moz-do-not-send="true"
                      class="moz-txt-link-abbreviated"
                      href="mailto:openid-specs-ab@lists.openid.net">
                      openid-specs-ab@lists.openid.net</a><br>
                    <b>Subject:</b> Re: [Openid-specs-ab]
                    token_endpoint_auth_method Registration example
                    error?</span></p>
              </div>
            </div>
            <p class="MsoNormal"> </p>
            <div>
              <p class="MsoNormal">Like discovery the response could be
                multi value.  However the client souls only register one
                value if it wants to restrict what the server accepts
                for that client_id. <br>
                <br>
                Sent from my iPhone</p>
            </div>
            <div>
              <p class="MsoNormal" style="margin-bottom:12.0pt"><br>
                On 2013-01-23, at 4:33 PM, Justin Richer <<a
                  moz-do-not-send="true" href="mailto:jricher@mitre.org">jricher@mitre.org</a>>
                wrote:</p>
            </div>
            <blockquote style="margin-top:5.0pt; margin-bottom:5.0pt">
              <div>
                <p class="MsoNormal" style="margin-bottom:12.0pt">But
                  now that the server responds with the current
                  configuration, it's no longer just about client
                  preference but also about the server expressing to the
                  client what it should do. So if a client gets a
                  client_secret, and the server is OK with it using
                  basic, post, or jwt with that secret, how can the
                  server tell the client this?<br>
                  <br>
                  The simplest thing is to keep it a single value as it
                  is now, but that's (as always) a tradeoff between
                  flexibility and complexity.
                  <br>
                  <br>
                   -- Justin</p>
                <div>
                  <p class="MsoNormal">On 01/23/2013 11:28 AM, John
                    Bradley wrote:</p>
                </div>
                <blockquote style="margin-top:5.0pt;
                  margin-bottom:5.0pt">
                  <p class="MsoNormal">If you want a client to
                    authenticate multiple ways just don't register a
                    prefrence.
                  </p>
                  <div>
                    <p class="MsoNormal"> </p>
                  </div>
                  <div>
                    <p class="MsoNormal">This was intended to prevent
                      IdP from accepting weaker methods of
                      authentication from attackers.   If you are not
                      doing that then the client should be able to use
                      anything the server supports.</p>
                  </div>
                  <div>
                    <p class="MsoNormal"> </p>
                  </div>
                  <div>
                    <p class="MsoNormal">Now if the client doesn't
                      register a public key then some methods will fail,
                      but that is a client decision.</p>
                  </div>
                  <div>
                    <p class="MsoNormal"> </p>
                  </div>
                  <div>
                    <p class="MsoNormal">I think trying to say I only
                      want to use 2 of the 5 available methods is
                      overkill.</p>
                  </div>
                  <div>
                    <p class="MsoNormal"> </p>
                  </div>
                  <div>
                    <p class="MsoNormal">The client should just pick the
                      one it is going to use.</p>
                  </div>
                  <div>
                    <p class="MsoNormal"> </p>
                  </div>
                  <div>
                    <p class="MsoNormal">If it really needs two methods
                      maybe it is really two clients and somebody is
                      fudging things a bit.</p>
                  </div>
                  <div>
                    <p class="MsoNormal"> </p>
                  </div>
                  <div>
                    <p class="MsoNormal">John B.</p>
                  </div>
                  <div>
                    <p class="MsoNormal"> </p>
                    <div>
                      <div>
                        <p class="MsoNormal">On 2013-01-23, at 4:18 PM,
                          Justin Richer <<a moz-do-not-send="true"
                            href="mailto:jricher@mitre.org">jricher@mitre.org</a>>
                          wrote:</p>
                      </div>
                      <p class="MsoNormal"><br>
                        <br>
                      </p>
                      <div>
                        <p class="MsoNormal"
                          style="margin-bottom:12.0pt">Actually come to
                          think of it, why wouldn't a client be able to
                          do both client_secret_basic and
                          client_secret_post to a server that supports
                          them? It's the same info presented in *almost*
                          the same way.
                          <br>
                          <br>
                          This combination may be the exceptional case,
                          though, as the other types
                          (client_secret_jwt,private_key_jwt, or even
                          "none" that OIDC hasn't adopted yet) aren't
                          particularly mutually compatible.
                          <br>
                          <br>
                           -- Justin<br>
                          <br>
                        </p>
                        <div>
                          <p class="MsoNormal">On 01/23/2013 10:53 AM,
                            Justin Richer wrote:</p>
                        </div>
                        <blockquote style="margin-top:5.0pt;
                          margin-bottom:5.0pt">
                          <p class="MsoNormal"
                            style="margin-bottom:12.0pt">OK, thanks for
                            catching that. I'll file a bug against
                            Oauth2 Dynreg as well (which has the same
                            examples). John is right that it is defined
                            as a single value and the examples are off.<br>
                            <br>
                             -- Justin</p>
                          <div>
                            <p class="MsoNormal">On 01/23/2013 10:03 AM,
                              Mike Jones wrote:</p>
                          </div>
                          <blockquote style="margin-top:5.0pt;
                            margin-bottom:5.0pt">
                            <p class="MsoNormal"><span
                                style="font-size:11.0pt;
                                font-family:"Calibri","sans-serif";
                                color:#1F497D">That’s what I thought. 
                                Thanks for confirming.</span></p>
                            <p class="MsoNormal"><span
                                style="font-size:11.0pt;
                                font-family:"Calibri","sans-serif";
                                color:#1F497D"> </span></p>
                            <p class="MsoNormal"><span
                                style="font-size:11.0pt;
                                font-family:"Calibri","sans-serif";
                                color:#1F497D">                                                           
                                -- Mike</span></p>
                            <p class="MsoNormal"><span
                                style="font-size:11.0pt;
                                font-family:"Calibri","sans-serif";
                                color:#1F497D"> </span></p>
                            <div>
                              <div style="border:none; border-top:solid
                                #B5C4DF 1.0pt; padding:3.0pt 0in 0in
                                0in">
                                <p class="MsoNormal"><b><span
                                      style="font-size:10.0pt;
                                      font-family:"Tahoma","sans-serif"">From:</span></b><span
                                    style="font-size:10.0pt;
                                    font-family:"Tahoma","sans-serif"">
                                    John Bradley [<a
                                      moz-do-not-send="true"
                                      href="mailto:ve7jtb@ve7jtb.com">mailto:ve7jtb@ve7jtb.com</a>]
                                    <br>
                                    <b>Sent:</b> Wednesday, January 23,
                                    2013 7:02 AM<br>
                                    <b>To:</b> Mike Jones<br>
                                    <b>Cc:</b> <a
                                      moz-do-not-send="true"
                                      href="mailto:openid-specs-ab@lists.openid.net">openid-specs-ab@lists.openid.net</a><br>
                                    <b>Subject:</b> Re:
                                    [Openid-specs-ab]
                                    token_endpoint_auth_method
                                    Registration example error?</span></p>
                              </div>
                            </div>
                            <p class="MsoNormal"> </p>
                            <p class="MsoNormal">The server may support
                              multiple methods, but the client MUST only
                              register one, so it shouldn't be multi
                              value for simplicity.</p>
                            <div>
                              <p class="MsoNormal"> </p>
                            </div>
                            <div>
                              <p class="MsoNormal">If you need two auth
                                methods they should be different
                                client_id.</p>
                            </div>
                            <div>
                              <p class="MsoNormal"> </p>
                            </div>
                            <div>
                              <p class="MsoNormal">This is intended
                                mostly to enhance security and prevent a
                                server from taking client_secret_basic
                                from an attacker when the real client is
                                using private_key_jwt.</p>
                            </div>
                            <div>
                              <p class="MsoNormal"> </p>
                            </div>
                            <div>
                              <p class="MsoNormal">John B.</p>
                            </div>
                            <div>
                              <p class="MsoNormal"> </p>
                              <div>
                                <div>
                                  <p class="MsoNormal">On 2013-01-23, at
                                    9:07 AM, Mike Jones <<a
                                      moz-do-not-send="true"
                                      href="mailto:Michael.Jones@microsoft.com">Michael.Jones@microsoft.com</a>>
                                    wrote:</p>
                                </div>
                                <p class="MsoNormal"><br>
                                  <br>
                                  <br>
                                </p>
                                <div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif"">Registration
                                        contains the following
                                        definition:</span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif""> </span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Verdana","sans-serif""
                                        lang="EN">token_endpoint_auth_method</span></p>
                                  </div>
                                  <div style="margin-left:.5in">
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Verdana","sans-serif""
                                        lang="EN">OPTIONAL. Requested
                                        authentication method for the
                                        Token Endpoint. The options are</span><tt><span
                                          style="font-size:10.0pt;
                                          color:#003366" lang="EN">client_secret_post</span></tt><span
                                        style="font-size:11.0pt;
                                        font-family:"Verdana","sans-serif""
                                        lang="EN">,<span
                                          class="apple-converted-space"> </span></span><tt><span
                                          style="font-size:10.0pt;
                                          color:#003366" lang="EN">client_secret_basic</span></tt><span
                                        style="font-size:11.0pt;
                                        font-family:"Verdana","sans-serif""
                                        lang="EN">,<span
                                          class="apple-converted-space"> </span></span><tt><span
                                          style="font-size:10.0pt;
                                          color:#003366" lang="EN">client_secret_jwt</span></tt><span
                                        style="font-size:11.0pt;
                                        font-family:"Verdana","sans-serif""
                                        lang="EN">, and<span
                                          class="apple-converted-space"> </span></span><tt><span
                                          style="font-size:10.0pt;
                                          color:#003366" lang="EN">private_key_jwt</span></tt><span
                                        style="font-size:11.0pt;
                                        font-family:"Verdana","sans-serif""
                                        lang="EN">, as described in
                                        Section 2.2.1 of
                                        [OpenID.Messages]. Other
                                        Authentication methods may be
                                        defined by extension. If
                                        unspecified or omitted, the
                                        default is<span
                                          class="apple-converted-space"> </span></span><tt><span
                                          style="font-size:10.0pt;
                                          color:#003366" lang="EN">client_secret_basic</span></tt><span
                                        class="apple-converted-space"><span
                                          style="font-size:11.0pt;
                                          font-family:"Verdana","sans-serif""
                                          lang="EN"> </span></span><span
                                        style="font-size:11.0pt;
                                        font-family:"Verdana","sans-serif""
                                        lang="EN">HTTP Basic
                                        Authentication Scheme as
                                        specified in Section 2.3.1 of
                                        [RFC6749].</span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif""> </span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif"">It
                                        later uses
                                        “token_endpoint_auth_method” in
                                        two example result values in
                                        this manner:</span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif""> </span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"
                                      style="background:#CCCCCC"><span
                                        style="" lang="EN">"token_endpoint_auth_method":</span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"
                                      style="background:#CCCCCC"><span
                                        style="" lang="EN">  
                                        "client_secret_basic
                                        client_secret_post",</span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif""> </span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif"">This
                                        looks like a bug to me, since
                                        the string appears to be trying
                                        to contain multiple values.</span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif""> </span></p>
                                  </div>
                                  <div>
                                    <p class="MsoNormal"><span
                                        style="font-size:11.0pt;
                                        font-family:"Calibri","sans-serif"">Thus,
                                        I’m changing the string used to
                                        just<span
                                          class="apple-converted-space"> </span></span></p>
                                  </div>
                                </div>
                              </div>
                            </div>
                          </blockquote>
                        </blockquote>
                      </div>
                    </div>
                  </div>
                </blockquote>
              </div>
            </blockquote>
          </div>
        </blockquote>
        <br>
      </div>
    </blockquote>
    <br>
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