<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">You want to store the random value and send the hash. Saving the hash is not secure unless it is signed. <div><br></div><div>The idea is to force an attacker to compute a plaintext for the hash (hard to impossible depending on length) in order to be able to present the response from the AS.</div><div><br></div><div><blockquote type="cite"><div lang="EN-US" link="blue" vlink="purple"><div class="WordSection1" style="page: WordSection1;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">For case 1: The Client can generate a random value with sufficient entropy and store that value in local storage. This value is then hashed to produce a nonce value. The hashed value could optionally be truncated to a sufficient number of bits (such as 128) before use. </span></div></div></div></blockquote><div><div>On Oct 29, 2013, at 9:40 PM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com">Michael.Jones@microsoft.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div lang="EN-US" link="blue" vlink="purple" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;"><div class="WordSection1" style="page: WordSection1;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">Here’s an attempt at simplifying George’s text.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">For case 1: The Client can generate a random value with sufficient entropy and store a cryptographic hash (such as SHA-256) of that value in local storage. The hashed value could optionally be truncated to a sufficient number of bits (such as 128) before use. The stored value is used as the nonce value.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"><o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">For case 2: The Client can generate a random value with sufficient entropy and store that value as an HttpOnly session cookie. A cryptographic hash (such as SHA-256) of the cookie value (or a truncation of the hash value to a sufficient number of bits) is used as the nonce value.<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">Am I correct that the cryptographic hash function is used to spread the entropy present in the random value generated throughout the nonce value in both cases?<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">Comments?<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> </span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> -- Mike<o:p></o:p></span></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> </span></div><div><div style="border-style: solid none none; border-top-color: rgb(181, 196, 223); border-top-width: 1pt; padding: 3pt 0in 0in;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif;">From:</span></b><span style="font-size: 10pt; font-family: Tahoma, sans-serif;"><span class="Apple-converted-space"> </span>Richer, Justin P. [<a href="mailto:jricher@mitre.org">mailto:jricher@mitre.org</a>]<span class="Apple-converted-space"> </span><br><b>Sent:</b><span class="Apple-converted-space"> </span>Saturday, October 26, 2013 11:33 AM<br><b>To:</b><span class="Apple-converted-space"> </span>George Fletcher<br><b>Cc:</b><span class="Apple-converted-space"> </span>John Bradley; Mike Jones; <a href="mailto:openid-specs-ab@lists.openid.net">openid-specs-ab@lists.openid.net</a><br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: [Openid-specs-ab] Nonce value suggestion for the Implicit Flow<o:p></o:p></span></div></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-family: Helvetica, sans-serif;">I don't know where the best place is to provide this guidance. If we have a "validating the ID Token" sub-section in the new ID Token section, then maybe it would best fit there.</span><o:p></o:p></div></blockquote><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">+1 to this idea with a cross link from the nonce definition.<o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"> -- Justin<o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div><div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">On Oct 25, 2013, at 6:17 AM, George Fletcher <<a href="mailto:gffletch@aol.com" style="color: purple; text-decoration: underline;">gffletch@aol.com</a>> wrote:<o:p></o:p></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><br><br><o:p></o:p></div><div><p class="MsoNormal" style="margin: 0in 0in 12pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-family: Helvetica, sans-serif;">If we are going to give guidance, then we really need to give guidance for two different use cases...<br><br>1. The "client" will validate the response locally in the browser<br>2. The "client" will validate the response at it's server (even though it's using the implicit flow)<br><br>For use case 1: One method to achieve this is for the client to generate a random string with sufficient entropy and store a SHA-1 hash of the string in local storage. Then use the SHA-1 hash of the random string as the value of the nonce parameter. To validate the nonce on receipt of the ID Token, extract the nonce from the ID Token and compare it to the stored SHA-1 hash in local storage.<br><br>For use case 2: One method to achieve this is for the backend server to use a SHA-1 hash of the "clients" protected session cookie as the value of the nonce parameter when constructing the AuthorizationRequest. Note that the Session cookie SHOULD be protected (restricted to SSL and not readable by JavaScript) for this method. To validate the ID Token at the server, the server calculates a SHA-1 hash of the Session cookie value and compares that to the nonce value in the ID Token.<br><br>I don't know where the best place is to provide this guidance. If we have a "validating the ID Token" sub-section in the new ID Token section, then maybe it would best fit there.<br><br>Thanks,<br>George</span><o:p></o:p></p><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">On 10/24/13 7:16 PM, John Bradley wrote:<o:p></o:p></div></div><blockquote style="margin-top: 5pt; margin-bottom: 5pt;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">We want the implicit flow to validate nonce, it would be better to have some reasonable advice for using HTML local storage rather than session cookies.<o:p></o:p></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div><div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">On 2013-10-24, at 3:44 PM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com" style="color: purple; text-decoration: underline;">Michael.Jones@microsoft.com</a>> wrote:<o:p></o:p></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><br><br><o:p></o:p></div><div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);">We could drop it from the Implicit Flow, as it’s already present in the Code Flow. Does that work for people?</span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> </span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> -- Mike</span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif; color: rgb(31, 73, 125);"> </span><o:p></o:p></div></div><div><div style="border-style: solid none none; border-top-width: 1pt; padding: 3pt 0in 0in; border-top-color: rgb(181, 196, 223);"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><b><span style="font-size: 10pt; font-family: Tahoma, sans-serif;">From:</span></b><span class="apple-converted-space"><span style="font-size: 10pt; font-family: Tahoma, sans-serif;"> </span></span><span style="font-size: 10pt; font-family: Tahoma, sans-serif;">Richer, Justin P. [<a href="mailto:jricher@" style="color: purple; text-decoration: underline;">mailto:jricher@</a><a href="http://mitre.org/" style="color: purple; text-decoration: underline;">mitre.org</a>]<span class="apple-converted-space"> </span><br><b>Sent:</b><span class="apple-converted-space"> </span>Thursday, October 24, 2013 12:56 PM<br><b>To:</b><span class="apple-converted-space"> </span>Mike Jones<br><b>Cc:</b><span class="apple-converted-space"> </span><a href="mailto:openid-specs-ab@lists.openid.net" style="color: purple; text-decoration: underline;">openid-specs-ab@lists.openid.net</a><br><b>Subject:</b><span class="apple-converted-space"> </span>Re: [Openid-specs-ab] Nonce value suggestion for the Implicit Flow</span><o:p></o:p></div></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"> <o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">I'm actually in favor of dropping this example, or else providing it in a list of alternatives. The important thing is that the client can validate the exact value of the nonce parameter on its way back through, the mechanics of how that happens are client specific (but we can provide simple guidance).<o:p></o:p></div></div><div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"> <o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"> -- Justin<o:p></o:p></div></div><div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"> <o:p></o:p></div></div><div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">On Oct 24, 2013, at 11:44 AM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com" style="color: purple; text-decoration: underline;"><span style="color: purple;">Michael.Jones@microsoft.com</span></a>><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"> wrote:<o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><br><br><br><o:p></o:p></div></div><div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;">For the Implicit Flow, the “nonce” description contains this text at<a href="http://openid.bitbucket.org/openid-connect-core-1_0.html#ImplicitAuthorizationRequest" style="color: purple; text-decoration: underline;"><span style="color: purple;">http://openid.bitbucket.org/openid-connect-core-1_0.html#ImplicitAuthorizationRequest</span></a>:</span><o:p></o:p></div></div><div style="margin-left: 0.5in;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif;">Sufficient entropy MUST be present in the<span class="apple-converted-space"> </span></span><tt style="font-family: 'Courier New';"><span lang="EN" style="font-size: 10pt; color: rgb(0, 51, 102);">nonce</span></tt><span class="apple-converted-space"><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif;"> </span></span><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif;">values used to prevent attackers from guessing values.<span class="apple-converted-space"> </span><span style="background-color: yellow; background-position: initial initial; background-repeat: initial initial;">One method to achieve this is to store a random value as a signed session cookie, and pass the value in the</span></span><tt style="font-family: 'Courier New';"><span lang="EN" style="font-size: 10pt; color: rgb(0, 51, 102); background-color: yellow; background-position: initial initial; background-repeat: initial initial;">nonce</span></tt><span class="apple-converted-space"><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; background-color: yellow; background-position: initial initial; background-repeat: initial initial;"> </span></span><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; background-color: yellow; background-position: initial initial; background-repeat: initial initial;">parameter. In that case, the<span class="apple-converted-space"> </span></span><tt style="font-family: 'Courier New';"><span lang="EN" style="font-size: 10pt; color: rgb(0, 51, 102); background-color: yellow; background-position: initial initial; background-repeat: initial initial;">nonce</span></tt><span class="apple-converted-space"><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; background-color: yellow; background-position: initial initial; background-repeat: initial initial;"> </span></span><span lang="EN" style="font-size: 11pt; font-family: Verdana, sans-serif; background-color: yellow; background-position: initial initial; background-repeat: initial initial;">in the returned ID Token can be compared to the signed session cookie to detect ID Token replay by third parties.</span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;"> </span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;">George wrote this about the suggestion in his review:</span><o:p></o:p></div></div><div style="margin-left: 0.5in;"><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;">“I'm not sure this suggestion makes sense for the implicit flow. The client would need to write a cookie value on the domain of the redirect_uri and the attempt to read it on the return of the implicit flow. Wondering if a local storage example would make more sense.”</span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;"> </span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;">Do people agree with him? If so, does someone want to supply specific alternative text to use?</span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;"> </span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;"> -- Mike</span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 11pt; font-family: Calibri, sans-serif;"> </span><o:p></o:p></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 13.5pt; font-family: Helvetica, sans-serif;">_______________________________________________<br>Openid-specs-ab mailing list<br><a href="mailto:Openid-specs-ab@lists.openid.net" style="color: purple; text-decoration: underline;"><span style="color: purple;">Openid-specs-ab@lists.openid.net</span></a><br><a href="http://lists.openid.net/mailman/listinfo/openid-specs-ab" style="color: purple; text-decoration: underline;"><span style="color: purple;">http://lists.openid.net/mailman/listinfo/openid-specs-ab</span></a></span><o:p></o:p></div></div></div></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"> <o:p></o:p></div></div></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><span style="font-size: 13.5pt; font-family: Helvetica, sans-serif;">_______________________________________________<br>Openid-specs-ab mailing list<br><a href="mailto:Openid-specs-ab@lists.openid.net" style="color: purple; text-decoration: underline;">Openid-specs-ab@lists.openid.net</a><br><a href="http://lists.openid.net/mailman/listinfo/openid-specs-ab" style="color: purple; text-decoration: underline;">http://lists.openid.net/mailman/listinfo/openid-specs-ab</a><o:p></o:p></span></div></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><br><br><br><o:p></o:p></div><pre style="margin: 0in 0in 0.0001pt; font-size: 10pt; font-family: 'Courier New';">_______________________________________________<o:p></o:p></pre><pre style="margin: 0in 0in 0.0001pt; font-size: 10pt; font-family: 'Courier New';">Openid-specs-ab mailing list<o:p></o:p></pre><pre style="margin: 0in 0in 0.0001pt; font-size: 10pt; font-family: 'Courier New';"><a href="mailto:Openid-specs-ab@lists.openid.net" style="color: purple; text-decoration: underline;">Openid-specs-ab@lists.openid.net</a><o:p></o:p></pre><pre style="margin: 0in 0in 0.0001pt; font-size: 10pt; font-family: 'Courier New';"><a href="http://lists.openid.net/mailman/listinfo/openid-specs-ab" style="color: purple; text-decoration: underline;">http://lists.openid.net/mailman/listinfo/openid-specs-ab</a><o:p></o:p></pre></blockquote><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;"><o:p> </o:p></div><div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">--<span class="Apple-converted-space"> </span><br><a href="http://connect.me/gffletch" title="View full card on
Connect.Me" style="color: purple; text-decoration: underline;"><XeC.png></a><o:p></o:p></div></div></div><div style="margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif;">_______________________________________________<br>Openid-specs-ab mailing list<br><a href="mailto:Openid-specs-ab@lists.openid.net" style="color: purple; text-decoration: underline;">Openid-specs-ab@lists.openid.net</a><br><a href="http://lists.openid.net/mailman/listinfo/openid-specs-ab" style="color: purple; text-decoration: underline;">http://lists.openid.net/mailman/listinfo/openid-specs-ab</a></div></div></div></div></blockquote></div><br></div></body></html>