Introduction to Web Application Security

1. Introduction to Web Application Security Rex Booth, CISSP, PMP Senior Manager, Grant Thornton LLP

2. Introduction: Rex Booth Senior Manager at Grant Thornton 10+ years of IT experience Former web application developer Leads cybersecurity group for Grant Thornton's public sector practice Experience with information security from a variety of perspectives including developer, auditor, and ISSO

3. Agenda • Why target web applications? • Web application attack surface overview • Attack examples • Client layer attacks • Application layer attacks • Data layer attacks • 3rd party trust attacks • Live Demonstration • Best Practices and Remediation resources • Questions

4. Why target web applications? • Incentives • Valuable targets • Financial • Competitive advantage (corporate or national) • Force multiplier • Reputation / Prestige • Absence of effective deterrents • Soft targets: Weak or poorly implemented security • Low cost of entry: cheap and easy access • “Wild West” mentality regarding probability of detection, capture and punishment

5. Agenda • Why target web applications? • Web application attack surface overview • Attack examples • Client layer attacks • Application layer attacks • Data layer attacks • 3rd party trust attacks • Live Demonstration • Best Practices and Remediation resources • Questions

6. Web application attack surface 3rd Party Trusts • Client layer: • Code and functionality executed on the client-side • Various vulnerabilities • Two key points: • Never trust client-supplied data • Don’t introduce vulnerabilities by trying to offload cycles from the server to the client

7. Web application attack surface 3rd Party Trusts • Application layer: • Expression and capture of business rules and business policy logic in code; • Workflows based on the ordered tasks of passing documents or data from one participant (a person or a software system) to another; • Do those expressions introduce vulnerabilities? • Attacks on specific technology and poor implementation

8. Web application attack surface 3rd Party Trusts • Data layer: • Likely the most valuable component of your application to your organization • Less focused on code and logic, more focused on good implementation and maintenance, proper technology

9. Web application attack surface 3rd Party Trusts • 3rd Party Trusts: • Critical to maintain awareness of system interactions • Federal Sector C&A Interconnection Agreements • Potential to affect all layers of the application • Repeat the attack surfaces at the client, application and data layers for each 3rd party trust

10. Agenda • Why target web applications? • Web application attack surface overview • Attack examples • Client layer attacks • Application layer attacks • Data layer attacks • 3rd party trust attacks • Live Demonstration • Best Practices and Remediation resources • Questions

11. Injection Attacks • SQL injection is the most common web attack • An attacker inserts commands that are used to dynamically construct SQL queries • Attacker may be able to view or modify any data in a database • Severity can be equivalent to a full database compromise • Other injections include XML, LDAP, code injection, remote file inclusions • Any action that takes input from the user and uses it in a query or function

12. SQL Injection Scenario You wish to edit your credit card number in your account profile on http://www.shoppingsite.com To verify your identity, the site asks for the last 4 digits of your credit card The application then passes your input to the following query SELECT * FROM credit_cards WHERE digits = ‘your_input’

13. SQL Injection Scenario What if the attacker enters 1234’ OR ‘1’ = ‘1 The full query then becomes SELECT * FROM credit_cards WHERE digits = ‘1234’ OR ‘1’ = ‘1’; This query will always return true and, therefore, will return every card in the database.

14. Cross Site Scripting (XSS) • Affects the client web browser. • Scripting code from URL or HTML Form gets rendered in the page sent by the server. • 2 types of XSS • Persistent / Stored: attack code gets stored in the application data store and affects all users who visit the page. • Non-Persistent / Reflected: attack code does not get stored and can only affect 1 user at a time. • One of the most prolific and dangerous vulnerabilities on the web.

15. Cross Site Scripting (XSS) Scenario • What if we change “shawn” to: • “><script>alert(document.cookie)</script>

16. Cross Site Scripting (XSS) Scenario

17. Cross Site Request Forgery (CSRF) Affects the client browser. The vulnerability allows an attacker to force the browser to fraudulently execute application functionality. Leverages the user’s authenticated session on the target application. Not *really* a vulnerability, rather an exploit of expected functionality. Can be one of the most serious vulnerabilities in web applications.


18. Authentication and Authorization Lack of authentication / authorization. Unauthorized data access. Unauthorized system functionality access. Predictable session identifiers. Session Fixation. Session Replay. Brute forcing of credentials.

19. Session Fixation Example • Session Fixation occurs when a session identifier is not refreshed after successful authentication • The following sequence describes an application vulnerable to Session Fixation: • When a user browses to www.whatever.com, they receive Cookie: my_cookie=abcdefg • After logging in, the application elevates my_cookie=abcdefg from unauthenticated to authenticated status • Why is this a problem? • The initial value may have been sent over an unencrypted channel • Attacker could use XSS to set a known value in the target browser • The application may accept any value prior to authentication, making this even easier for an attacker

20. Business Logic Flaws • Flaw in the design and/or implementation of the project design. • Booking a ticket on a web application without paying. • Registering an account without completing all required steps. • Apply the same coupon/discount multiple times on the same order. • Account lockout on auction sites. • Setting your own pricing on a product. • No way to detect this type of vulnerability using automated tools.

21. Host and 3rd Party Code • Keeping up with patches • Patch management • 3rd party code dependency updates • Host security • Unused network services • Password Policy • Brute forcing • Logging • Hidden/Old/Unreferenced files • Building a good relationship with SysAdmins

22. Agenda • Why target web applications? • Web application attack surface overview • Attack examples • Client layer attacks • Application layer attacks • Data layer attacks • 3rd party trust attacks • Live Demonstration • Best Practices and Remediation resources • Questions

23. Agenda • Why target web applications? • Web application attack surface overview • Attack examples • Client layer attacks • Application layer attacks • Data layer attacks • 3rd party trust attacks • Live Demonstration • Best Practices and Remediation resources • Questions

24. Best Practices Summary Input validation and output encoding Strong authentication and password management Effective access controls Safe error handling and meaningful logging Protection of data at rest and in motion Proper system and database configuration See the OWASP Secure Coding Practices Quick Reference Guide for more information

25. Remediation Resources • Incorporating security into the SDLC • https://buildsecurityin.us-cert.gov • http://www.owasp.org • http://www.webappsec.org/ • Post-deployment remediation • Two basic approaches: fix the underlying problem or get in between the threat and the asset • The latter, including web application firewalls, are not a panacea, but can be useful

26. Questions • Ask now or contact via email: • Rex.Booth@us.gt.com