<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><base href="x-msg://406/"><style><!--
/* Font Definitions */
@font-face
{font-family:Helvetica;
panose-1:2 11 6 4 2 2 2 2 2 4;}
@font-face
{font-family:Wingdings;
panose-1:5 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:Wingdings;
panose-1:5 0 0 0 0 0 0 0 0 0;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0cm;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0cm;
margin-right:0cm;
margin-bottom:0cm;
margin-left:36.0pt;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";}
span.apple-converted-space
{mso-style-name:apple-converted-space;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri","sans-serif";
color:#1F497D;}
span.c28
{mso-style-name:c28;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:612.0pt 792.0pt;
margin:70.85pt 70.85pt 2.0cm 70.85pt;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:180508841;
mso-list-template-ids:-1932106744;}
@list l0:level1
{mso-level-start-at:4;
mso-level-tab-stop:36.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level2
{mso-level-tab-stop:72.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level3
{mso-level-tab-stop:108.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level4
{mso-level-tab-stop:144.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level5
{mso-level-tab-stop:180.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level6
{mso-level-tab-stop:216.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level7
{mso-level-tab-stop:252.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level8
{mso-level-tab-stop:288.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l0:level9
{mso-level-tab-stop:324.0pt;
mso-level-number-position:left;
text-indent:-18.0pt;}
@list l1
{mso-list-id:1627350741;
mso-list-type:hybrid;
mso-list-template-ids:251710140 67698689 67698691 67698693 67698689 67698691 67698693 67698689 67698691 67698693;}
@list l1:level1
{mso-level-start-at:0;
mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;
mso-fareast-font-family:"Times New Roman";
mso-bidi-font-family:"Times New Roman";}
@list l1:level2
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l1:level3
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l1:level4
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l1:level5
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l1:level6
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
@list l1:level7
{mso-level-number-format:bullet;
mso-level-text:\F0B7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Symbol;}
@list l1:level8
{mso-level-number-format:bullet;
mso-level-text:o;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:"Courier New";}
@list l1:level9
{mso-level-number-format:bullet;
mso-level-text:\F0A7;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-18.0pt;
font-family:Wingdings;}
ol
{margin-bottom:0cm;}
ul
{margin-bottom:0cm;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple style='word-wrap: break-word;-webkit-nbsp-mode: space;-webkit-line-break: after-white-space'><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The attack is carried out in steps 4.1 and 4.2:<o:p></o:p></span></p><p class=MsoListParagraph style='text-indent:-18.0pt;mso-list:l0 level1 lfo1'><![if !supportLists]><span style='mso-list:Ignore'>4.<span style='font:7.0pt "Times New Roman"'> </span></span><![endif]>A malicious site does the following: <o:p></o:p></p><ol start=4 type=1><ol start=1 type=1><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo1'>Logs victim in to attacker’s Facebook by using CSRF on the Login, or by tossing cookies<o:p></o:p></li><li class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;mso-list:l0 level2 lfo1'>POSTs to the account association request<o:p></o:p></li></ol></ol><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>4.1 is the Idp (facebook) who needs CSRF or cookie manipulation protection<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>4.2 is the “accessing application” (stackoverflow) that needs protection<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Two parties might use openid connect: IdP and accessing application. There should be some protection through the signed id_token and nonce inside which might be used a session cookie for both IdP and accessing application.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>The security measure to protect the account linkage by asking for the user’s password again is good but outside of openid connect.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Maybe this discussion is relevant for accountchooser too?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>My guess is that the connect specs are not really relevant for this attack against account linkage.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Maybe a new section in “</span><span class=c28>Running a Login System with an Account Chooser</span><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>” titled “Adding more accounts to a local user account”<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><a href="https://docs.google.com/document/pub?id=1O7jyQLb7dW6EnJrFsWZDyh0Yq0aFJU5UJ4i5QzYlTjU">https://docs.google.com/document/pub?id=1O7jyQLb7dW6EnJrFsWZDyh0Yq0aFJU5UJ4i5QzYlTjU</a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>might help?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>-Axel<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><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"'> openid-specs-ab-bounces@lists.openid.net [mailto:openid-specs-ab-bounces@lists.openid.net] <b>On Behalf Of </b>John Bradley<br><b>Sent:</b> Wednesday, May 15, 2013 9:16 AM<br><b>To:</b> Mike Jones<br><b>Cc:</b> openid-specs-ab@lists.openid.net<br><b>Subject:</b> Re: [Openid-specs-ab] OAuth implementation vulnerability<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The attack seems to be about using CSRF to link an account rather than the normal login. I need to look at it some more, but I guess the account linking code taking a POST without CSRF protection is the underlying cause. The Connect state and nonce would not be able to stop this as Connect is triggered by the Post before the Connect flow.<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On 2013-05-15, at 8:20 AM, Mike Jones <<a href="mailto:Michael.Jones@microsoft.com">Michael.Jones@microsoft.com</a>> wrote:<o:p></o:p></p></div><p class=MsoNormal><br><br><o:p></o:p></p><div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Can you propose concise security considerations text about the issues identified in the post? I’m almost done applying the changes agreed to in Mountain View to the specs, so the timing of adding this would be good, in terms of letting people review the text before we publish the Implementer’s Drafts.</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> -- Mike</span><o:p></o:p></p></div><div><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p></div><div><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span class=apple-converted-space><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> </span></span><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'><a href="mailto:openid-specs-ab-bounces@lists.openid.net">openid-specs-ab-bounces@lists.openid.net</a> [mailto:openid-<a href="mailto:specs-ab-bounces@lists.openid.net">specs-ab-bounces@lists.openid.net</a>]<span class=apple-converted-space> </span><b>On Behalf Of<span class=apple-converted-space> </span></b>Nat Sakimura<br><b>Sent:</b><span class=apple-converted-space> </span>Tuesday, May 14, 2013 6:33 PM<br><b>To:</b><span class=apple-converted-space> </span><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>[Openid-specs-ab] OAuth implementation vulnerability</span><o:p></o:p></p></div><div><p class=MsoNormal> <o:p></o:p></p></div><div><div><p class=MsoNormal>You guys probably new it, but it is a good read. <o:p></o:p></p></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><p class=MsoNormal><a href="http://webstersprodigy.net/2013/05/09/common-oauth-issue-you-can-use-to-take-over-accounts/"><span style='color:purple'>http://webstersprodigy.net/2013/05/09/common-oauth-issue-you-can-use-to-take-over-accounts/</span></a><o:p></o:p></p></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><p class=MsoNormal>BTW, perhaps we should add <span style='font-size:9.5pt;font-family:"Arial","sans-serif";color:#555555'> x-frame-options </span>to the spec? <o:p></o:p></p></div></div><div><div><p class=MsoNormal>Also, some tightening up in the security considerations? <o:p></o:p></p></div></div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><div><p class=MsoNormal>I know that this is really an implementation issues but the magnitude of the attack success make me think that perhaps it is a good idea to mention them at least. I being probably the one who want to finish the spec the most... <o:p></o:p></p></div></div><div><div><div><p class=MsoNormal> <o:p></o:p></p></div></div><div><p class=MsoNormal>--<span class=apple-converted-space> </span><br>Nat Sakimura (=nat)<o:p></o:p></p></div><div><div><p class=MsoNormal>Chairman, OpenID Foundation<br><a href="http://nat.sakimura.org/" target="_blank"><span style='color:purple'>http://nat.sakimura.org/</span></a><br>@_nat_en<o:p></o:p></p></div></div></div></div><p class=MsoNormal><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">Openid-specs-ab@lists.openid.net</a><br>http://lists.openid.net/mailman/listinfo/openid-specs-ab<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p></div></div></body></html>