(Software) Security

1. (Software) Security Erik Poll Digital Security group Radboud University Nijmegen

2. A brief history of security problems • attacks on multi-user UNIX systems for fun • viruses & worms attacking operating systems • due to buffer overflow, format string attacks, integer overflows,... • response: firewalls & better operating system code • variant: bot-nets • attacks on web-applications • due to SQL injection, XSS, session riding, .... • response: intrusion detection systems & application firewalls • attacks on web-browsers • man-in-the-browser attacks • ...

3. A brief history of security problems • Trojans & spyware • installed via OS security hole, or silly user • spam • response: spam filters • variants: phishing, spear-phishing & whaling, spit • ...

4. Trend • move away from hacking for 'fun' (ie vandalism) to hacking for profit • zero-day exploits are worth a lot of money

5. Causes Important causes of these security problems • bad software • buggy OS software, web-application software, ... • solution: patching? • gullible & stupid users • too easy to just blame users: if they are gullible and stupid, they should be protected • solution: user education?

6. Security is about people (users, employees, sys-admins, programmers,...), incompetence, confusion, lethargy, stupidity, mistakes, access control, passwords, biometrics, cryptology, protocols, policies & their enforcement, monitoring, auditing, legislation, persecution, liability, risk management, complexity, software, bugs, verification, hackers, viruses, hardware, operating systems, networks, databases, public relations, public perception, conventions, standards, physical protection, data protection, ...

7. Security is about people (users, employees, sys-admins, programmers,...), incompetence, confusion, lethargy, stupidity, mistakes, access control, passwords, biometrics, cryptology, protocols, policies & their enforcement, monitoring, auditing, legislation, persecution, liability, risk management, complexity, software, bugs, verification, hackers, viruses, hardware, operating systems, networks, databases, public relations, public perception, conventions, standards, physical protection, data protection, ...

8. Cryptography is usually not the problem "Using encryption on the Internet is the equivalent of arranging an armored car to deliver credit card information from someone living in a cardboard box to someone living on a park bench." -- Gene Spafford

9. Root cause analysis • Security is always a secondary concern • primary goal of software is to provide somefunctionality or services • managing the associated risks is only a derived or secondary concern • There is often a trade-off/conflict between • security • functionality & convenience

10. "The only system which is truly secure is one which is switched off and unplugged, locked in a titanium-lined safe, buried in a concrete bunker, and surrounded by nerve gas and very highly paid armed guards. Even then, I wouldn't stake my life on it” -- Gene Spafford

11. What goes wrong? • at a high-level • not understanding the security requirements and threats • at a low-level • silly little program bugs or flaws that introduce vulnerabilities

12. How can we improve things? • at a high-level • seriously looking at security requirements and threats when (prior to) building systems • at a low-level • train programmers to be aware of pitfalls associated with programming language, OS, platform • improve these languages, OSs, platform • making them less error-prone

13. low-level

14. Security as secondary concern • in programming languages • Algol 60 introduces array bound checks, in 1960 • C doesn't use this, in 1970s ... • ... 3 decades later, we're still trying to get rid of buffer overflows • early 2000s: people start using safestr.h

15. Security as secondary concern • in training • many students learn programming in C(++) • nobody tells them about buffer overflows or safestring libraries • a case of criminal negligence?

16. Functionality vs security Lost battles? • operating systems • huge OS, with huge attack surface (API), • programming languages • buffer overflows, format strings, ... in C • lots of things in PHP • webbrowsers • plug-ins for various formats, javascript, VBscript, ... • email clients • ...

17. Software infrastructure Applications are built on top of very complex "infrastructure" consisting of • operating system • programming language/platform/APIs/middleware • other applications & utilities • eg SQL database This infrastructure provides security mechanisms, but is also a source of security pitfalls. You need to understand both to develop secure applications on a give infrastructure.

18. Threats & vulnerabilities • Knowledge about threats & vulnerabilities crucial • my first dynamic webpage, with a cgi-bin script, was hopelessly insecure • Vulnerabilities can be specific to programming language, operating system, database,... used, and are continuously evolving, so we cannot hope to cover all vulnerabilities. • “Fortunately” people keep making the same mistakes • and the same security problems keep reappearing

19. The bad news:people keep making the same mistakes • when writing programs & when designing programming languages or other infrastructure • SQL injection • string concatenation is a convenient way to build SQL queries... • will we be chasing SQL injection faults in 30 years, just as we're still chasing buffer overflow attacks? • insist on use of eg. PreparedStatement? • PHP • PHP is a convenient way to quickly build a website...

20. Functionality vs security : PHP "..., I've come to the conclusion that it is basically impossible for normal programmers to write secure PHP code. It takes far too much effort. .... PHP's raison d'etre is that it is simple to pick up and make it do something useful. There needs to be a major push ... to make it safe for the likely level of programmers - newbies. Newbies have zero chance of writing secure software unless their language is safe. " [http://www.greebo.cnet]

21. The "good" news:people keep making the same mistakes • We can make checklists for common mistakes • We can teach students about common mistakes • We can implement tools that check them • source code analysers aka static analysis tools • Static analysis tools for C(++) • Coverity, Fortify, jTest, PolySpace, PREfast, PREfix, ... • C/C++ checkers focus on memory-related issues and for Java • CheckStyle, Findbugs, PMD, Fortify, jTest, IntelliJ, ...

22. OWASP Top 10 of web application vulnerabilities • Anyone building a web-application should know about these vulnerabilities: • how they work, • how they arise, and • how they can be avoided • Unvalidated Input • Broken Access Control • Broken Authentication and Session Management • Cross Site Scripting (XSS) Flaws • Buffer Overflows • Injection Flaws • Improper Error Handling • Insecure Storage • Denial of Service • Insecure Configuration Management Lots of info on web-application security on OWAPS.org

23. buffer overruns format string problems integer overflows SQL injection command injection failing to handle errors XSS failing to protect network traffic use of magic URLs or hidden form fields improper use of TLS, SSL weak passwords failing to store & protect data securely information leakage improper file access trusting network name resolution race conditions unauthenticated key exchange weak random numbers poor usability 19 Deadly sins of software security [Howard, LeBlanc, Viega]

24. Classification of Software Security Errors • Input Validation and Representation • API Abuse • Security Features • Time and State • Errors • Code Quality • Encapsulation *. Environment • [Katrina Tsipenyuk, Brian Chess, Gary McGraw, Seven Pernicious Kingdoms: A Taxonomy of Software Security Errors]

25. Two sides to software security: do’s & dont’s • What are the methods and technologies, available to us if we want to provide security? • security in the software development lifecycle • engineering & design principles • security technologies • What are the methods and technologies available to the enemy who wants to break security ? ie. what are the threats and vulnerabilities we’re up against

26. How to improve software security? • Awareness & knowledge of vulnerabilities (don'ts) • general (input validation, ...) • specific to a kind of application (SQL injection, XSS, ...), or • specific to a kind of programming language (buffer overflows, ...) • Awareness & knowledge of countermeasures (do's) at different points in the development lifecycle at level of application, programming language, or platform Eg security technologies such as • access control, session management • untrusted code security • type-safe languages, sandboxing, code-based access control • runtime monitoring • program analyses: typing, information flow, static analysis, verification But beware that security software ≠ software security

27. high-level

28. Security concepts [as used in Common Criteria] availability/ usefulness want to maximise owners want to minimise impose reduce countermeasures may have increase require vulnerabilities of attackers lead to exploit risks give rise to increase threats assets to want to abuse

29. Starting point for ensuring security • Any discussion of security should start with an inventory of • the stakeholders, • their assets, and • the threats to these assets by possible attackers • employees, clients, script kiddies, criminals • Any discussion of security without understanding these issues is meaningless

30. Threat Modeling Aka security/risk/requirements analysis A first step, not just for software • Identify assets & stakeholders • Consider architecture of application & its environment • Brainstorm about known threats • Define security assumptions • Rank threats by risk ≈ impact x likelihood • Decide which threats to respond to • Decide how to migitate these threats • which techniques & technologies

31. Countermeasures and more vulnerabilities Countermeasures can lead to new vulnerabilities • eg. if we only allow three incorrect logins, as a countermeasure to brute-force attacks, which new vulnerability do we introduce? If a countermeasure relies on software, bugs in this software may mean • that it is ineffective, or • worse still, that it introduces more weaknesses

32. STRIDE Simple approach to threat modelling developed at Microsoft, as part of SDL (Secure Development Lifecycle process) • Spoofing Identity • Tampering with Data • Repudiation • Information Disclosure • Denial of Service • Elevation of Privilige These and other checklists can be useful See also http://msdn2.microsoft.com/en-us/library/aa302419.aspx

33. Techniques to migitate these threats • Spoofing Identity • authentication, protect keys & passwords, ... • Tampering with Data • access control, hashes, digital signatures, MACs (message authentication codes), write-once storage... • Repudiation • logging, audit trails, digital signatures, ... • Information Disclosure • access control, encryption, not storing secrets, ... • Denial of Service • graceful degradation, filtering • Elevation of Privilige • access control, esp. least privilige, sandboxing, ...

34. Security in Software Development Life Cycle [Source: Gary McGraw, Software security, Security & Privacy Magazine, IEEE, Vol 2, No. 2, pp. 80-83, 2004. ]

35. keep it simple secure the weakest link defence in depth principle of least privilige minimise attack surface compartementalise secure defaults identify & question your assumptions fail securely promote privacy hiding secrets is hard use community resources ie find out about attacks and countermeasures be reluctant to trust ... Security principles

36. Conclusions

37. Conclusions • Security problems growing, because of • more networks • more software • growing importance of services provided by these • more money to be made by attacker! • People will always concentrate on functionality first, and worry about security later (if at all)

38. Conclusions To prevent security problems, you must • understand the security requirements & the threats that attackers pose • aka threat modeling • think like an attacker! • know the technologies you use • operating system • programming language & platform • ... and their security problems (do's & don'ts) • buffer overflows, SQL injection, ...

39. Questions?