Security 101
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The document discusses a security vulnerability related to the modification of HTTP/HTTPS standards to enhance performance, specifically through header compression, which could expose login cookies to attackers. It emphasizes the importance of understanding threat models and the challenges of developing secure software, suggesting the use of existing libraries to handle functionality when possible. Ultimately, the takeaway is to avoid implementing potentially insecure features that could compromise user data.
Security 101
- 1. Security 101: Just don’t do it
- 3. A hypothetical world… • You’re working for a company that has: • a web browser used by 45% of internet users • a web server visited by 90% of internet users (Stats made up) http://www.w3schools.com/browsers/browsers_stats.asp http://www.guardian.co.uk/technology/2012/nov/06/google-bing-uk-search-share
- 4. Your product manager says… • FASTER! • Our web browser and our web server must work awesomely fast together • Users have slow internet connections, especially their upload
- 5. So… • I want you to embrace, extend and extinguish the HTTP/HTTPS standard • We’re going to add a proprietary extension so that our web browser & our web server compress HTTP headers (even over HTTPS)
- 6. Your response? • Okay • Nope, that would introduce a security vulnerability • Interesting, I’d need to work out what our threat model is
- 7. Threat model • “Attacker-centric threat modelling starts with an attacker, and evaluates their goals, and how they might achieve them” • Implicit in this is what their capabilities are http://en.wikipedia.org/wiki/Threat_model
- 8. The attack… • The attacker’s goal is to obtain your login cookie so that they can impersonate you on the target site. • Whilst observing your network traffic (e.g. on a public Wi-Fi network), • and whilst you are logged in to the target site, • the attacker gets you to visit their evil site, • which has a whole bunch of Javascript that (slowly) adds images to the DOM. http://en.wikipedia.org/wiki/CRIME_(security_exploit)
- 9. HTTP headers GET / HTTP/1.1 Host: deploymentmanager.red-gate.com Connection: keep-alive Cache-Control: max-age=0 User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.95 Safari/537.11 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 DNT: 1 Accept-Encoding: gzip,deflate,sdch Accept-Language: en-GB,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 Cookie: DeploymentManagerAuthenticationTicket=0166AE259D1D0CE54C73A0FB 69E6A550E153A196C381EF4F2C5F96D96FA2D768E65621... Fiddler
- 10. Images of the form… GET /404.png?DeploymentManagerAuthenticationTicket=0 HTTP/1.1 ... Cookie: DeploymentManagerAuthenticationTicket=0166AE259D1D0CE54C73A0FB 69E6A550E153A196C381EF4F2C5F96D96FA2D768E65621... GET /404.png?DeploymentManagerAuthenticationTicket=1 HTTP/1.1 ... Cookie: DeploymentManagerAuthenticationTicket=0166AE259D1D0CE54C73A0FB 69E6A550E153A196C381EF4F2C5F96D96FA2D768E65621... GET /404.png?DeploymentManagerAuthenticationTicket=2 HTTP/1.1 ... Cookie: DeploymentManagerAuthenticationTicket=0166AE259D1D0CE54C73A0FB 69E6A550E153A196C381EF4F2C5F96D96FA2D768E65621... http://en.wikipedia.org/wiki/CRIME_(security_exploit)
- 11. Takeaway…
- 12. Takeaways… • Just don’t do it! • Writing software where security matters is hard • If you can, use an existing library to do all the functionality (in as few method calls as possible). If that library doesn’t have the feature you want, there’s probably a reason • If you can’t, then you’ve got a big problem