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Cross Site Request Forgery


Talk on CSRF I gave at work that talks about CSRF, how to prevent it and how frameworks can make prevention nearly automatic.

Talk on CSRF I gave at work that talks about CSRF, how to prevent it and how frameworks can make prevention nearly automatic.

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  • 1.
      • Presented by Tony Bibbs
      • May 20, 2008
    Cross Site Request Forgeries
  • 2. Rasmus Lerdorf “ The Web is broken and it's all your fault.”
  • 3. “ There is no metric for compliance with a 'culture', and a 'culture of security' is overridden by a culture of 'get the job done' every time.” Jon Espenschied
  • 4. Common Coding Vulnerabilities
    • Injection Flaws (SQL, LDAP, XPath, etc)‏
    • Cross Site Scripting (XSS)‏
    • Cross Site Request Forgeries (CSRF)‏
    • Buffer Overflows
  • 5. CSRF Defined
    • Cross-site request forgery, also known as one click attack, sidejacking or session riding and abbreviated as CSRF (Sea-Surf) or XSRF, is a type of malicious exploit of websites. Although this type of attack has similarities to cross-site scripting (XSS), cross-site scripting requires the attacker to inject unauthorized code into a website, while cross-site request forgery merely transmits unauthorized commands from a user the website trusts.
  • 6. “ Same Origin” Policy document, cookies XHR XHR TAG TAG JS
  • 7. How CSRF Works
    • GET requests are the easiest:
      • - Beware “src” and “href” attributes
    • POST aren't immune:
      • <body onload=”document.forms[0].submit()”>
      • <form method=”POST” action=”_url_”>
        • <input type=”hidden” name=”amount” value=”$1,000” />
      • </form>
  • 8. What Can a Hacker Do With CSRF?
    • Anything an authenticated user can do. Click links, submit forms, complete multi-step wizards.
    • Launch external attacks on Intranet sites.
    • No restrictions on same origin policy but are limited in that hackers can't read responses from other origins
  • 9. Trivial CSRF Exploit
  • 10. Exploiting Otherwise Secure Networks
  • 11. CSRF Prevention
    • Avoid Persistent Sessions
    • Use GET method properly
    • Token-based checks with TTL.
    • Double Authenticate via AJAX (read cookie via JS and submit in the body).
    • Code reviews.
  • 12. Framework-based Security
    • Framework implementations force security precautions.
    • PHP Examples: Flexy, Tainted Variables
    • CSRF prevention in PHP framework.
  • 13. CSRF Resources
    • CSRFGuard (Java, .NET and PHP)‏
    • CSRTTester
  • 14. Enterprise CSRF Mitigation
  • 15. Questions?
  • 16. Contacting Me
    • [email_address]
    • (515)281-6125
  • 17. Credits
    • Some material in this presentation is covered by the OWASP license, specifically work by Eric Sheridan
    • Any of my own contributions are also covered by the OWASP license which can be found at