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  1. Getting Past <THAT PROBLEM>Why Architecture is the Key to Software Security Gary McGraw, Ph.D. CTO, Cigital

  2. Defend the perimeter with a firewall To keep stuff out Over-rely on crypto “We use SSL” “Review” products when they’re done Why your code is bad Promulgate “penetrate and patch” Disallow advanced technologies Extensible systems (Java and .NET) are dangerous The “fat guy with keys” does not really understand software development. Old school security is reactive

  3. There is no such thing as 100% secure Must make tradeoffs Should be business decisions Proactive security is about building things right Design for security Security analysis Secure coding practice Security testing It’s all about the software Most security problems are caused by software bugs and flaws We must build secure software Modern security is about managing risks Software vulnerability reports to CERT/CC

  4. Software Security Pitfalls

  5. Language (#1) C/C++ Java, C# Perl, python, PHP Operating system Windows 9X Windows NT/XP Unix flavors The environment in which software operates is critical “Container” systems CORBA EJB DCOM Authentication mechanism Biometrics Password systems Tokens Smart cards PCI keys Network 802.11b (wireless) Technology choices are glossed

  6. Most security organizations are made up of network security people MIS, IT focus CISSP Network people do not often understand software development Code reviews alone do not cut it! Most development shops have good intentions, but little security knowledge Want to “build stuff” No good knowledge source See security review as a waste of time and a big hassle Software security is currently nobody’s job. Sociology problems

  7. IMPLEMENTATION BUGS THAT PROBLEM String format One-stage attacks Race conditions TOCTOU (time of check to time of use) Unsafe environment variables Unsafe system calls System() Untrusted input problems ARCHITECTURAL FLAWS Misuse of cryptography Privileged block protection failure Catastrophic security failure (fragility) Type safety confusion error Insecure auditing Broken or illogical access control Security problems are complicated

  8. Java’s classloading architecture flawed Separate instantiate class from manage name spaces Every release had problems March 96: JDK 1.0 March 97: JDK 1.0.7 July 98: JDK 1.2 What is “Java” anyway? (and what is .NET?!) JavaCard MicroChai J2EE More resources TINI J2SE J2ME FLAW: Architectural problems with Java

  9. Principles and Guidelines for Better Design

  10. Reaching for the brass ring • Design for security is critical • Teaching people HOW to do this is very hard • Apprenticeship is the state of the art today • Guidelines can help (but tend to be unsatisfyingly high level) • Guidelines can help, but are no magic bullet

  11. Secure the weakest link Practice defense in depth Fail securely Follow the principle of least privilege Compartmentalize Keep it simple Promote privacy Remember that hiding secrets is hard Be reluctant to trust Use your community resources Ten guiding principles for secure design

  12. don’t depend on initialization limit access to entities make everything final don’t depend on package scope don’t use inner classes avoid signing your code put all signed code in one archive make classes uncloneable make classes unserializeable make classes undeserializeable don’t compare classes by name don’t store secrets Twelve guidelines for writing safer Java

  13. Problem: Serialization • While serialized, objects aren’t protected by access controls • An attacker can read or modify the object in its serialized form • An attacker can create a serialized representation from scratch to insert into the system with bad data • Serialized data can be modified in several ways • Extending objects and overriding read/writeObject() • Extending ObjectInputStream/ObjectOutputStream • Capturing the data through network monitoring

  14. Fix: Serialization • Declare sensitive fields as transient if possible • If class will be serialized • Implement final writeObject() and readObject() methods to prevent subclasses overriding • Make sure readObject() was called - “initialized” set • If class should not be serialized • Prevent subclasses from overriding methods private final void writeObject()(ObjectOutputStream out) throws { throw new“Object can not be serialized”); } private final void readObject()(ObjectOutputStream out) throws { throw new“Object can not be deserialized”); }

  15. Fix: Serialization • Disallow permissions that allow modification to IO streams • SerializablePermission(“enableSubclassImplementation”) • SerializablePermission(“enableSubstitution”) • Encrypt serialized streams • At application level (key management is hard) • Through network mechanisms (SSL, IPSEC) • Consider using externalization as an alternative • Less data is transferred • Less ability for attacker to inject new classes Guidelines: “Make your classes Unserializable,” “Make your classes Undeserializable”

  16. Why Design?

  17. On Bricks and Walls • Proper use of “dangerous” system calls is equivalent to using solid bricks • Without an architecture, using all the right system calls won’t help

  18. On architectural analysis • Designers should not do this • Build a one page white board design model (like that ) • Use hypothesis testing to categorize risks • Threat modeling/Attack patterns • Rank risks • Tie to business context • Suggest fixes • Repeat

  19. 60 Requirements 50 Design 40 Coding Percentage of Defects 30 Testing 20 Maintenance 10 0 Defects at Each Stage of Software Development Source:TRW

  20. $15,000 $12,000 $9,000 Cost Per Defect $6,000 $3,000 0 Cost of Fixing Defects at Each Stage of Software Development Requirements Design Coding Testing Maintenance Source: TRW

  21. @stake: Security Defects Source: 2002 @stake - The Hoover Project (n=45)

  22. Although benefits can be found throughout the lifecycle, earlier involvement is most beneficial Vulnerabilities are harder to address post-design System-wide changesmay be required atlater stages Enablingimprovementscan be madeat design state @stake: Early is Good Source: 2002 @stake - The Hoover Project

  23. Security push/audit = on-going Microsoft’s software security process Where we need new tools and techniques Threatanalysis Secure questionsduring interviews Learn & Refine External review Concept Designs Complete Test plansComplete Code Complete Ship Post Ship Team member training Review old defects Check-ins checked Secure coding guidelines Use tools Data mutation & Least Priv Tests SecurityReview

  24. Open Questions • How is security best integrated into a standard engineering-based approach? • Do all engineers need to understand security? • What kind of organization can build secure software? • Is expertise and experience necessary for good security analysis? • Where does it come from? • How does auditing designs differ from auditing source code? • What role should security testing play in analysis?

  25. Suggested research agenda • Quantify, analyze, and explain bug/flaw categories • Do more cost/benefit analysis proving that early is good • Untangle security software from software security at the requirements stage • Explain why the software security problem is growing • Build tools for earlier in the lifecycle • Find out how to teach this stuff • Invent measures and metrics

  26. Pointers • Cigital’s Software Security Group invents and practices Software Quality Management • Get Building Secure Software • Send e-mail: “So now, when we face a choice between adding features and resolving security issues, we need to choose security.” -Bill Gates