Systems: Access Control

Topics and Goals

• Lampson’s “gold” standard techniques
  • Authentication, Authorization, Audit
  • Goal: Identify mechanisms for achieving each
  • Goal: Distinguish between authentication & authorization
• Authorization mechanisms
  • Goal: Explain different mechanisms
  • Goal: Compare & contrast
• Understand a basic logic for reasoning about authorization

“Gold” Standard

• Three core princples for reasoning about secure systems:
  • Authentication: Who is it?
  • Authorization: What can they do?
  • Audit: What happened?

Principles of Access Control

• What are the three components of an access control model?
• How does UNIX compare to AFS?
• How do we interpret an access matrix?
• How does Discretionary access control compare with Mandatory access control?
  • When should we use one vs. the other?
• How do access control lists (ACLs) work?
• How do capabilities work?
• ACLs vs. capabilities
  • How do they compare in expressive power?
  • When should we use one vs. the other?

AAA on the Web

• Authentication
  • Certifying public keys
    • Why are CAs necessary?
      • What trust assumptions do we make about them?
    • What is a certificate and how is it used?

  • What is a root key store?

  • What’s the difference between a DV certificate and an EV certificate?

  • What happens if a CA is malicious or careless?
• Audit
  • What are the key roles in certificate transparency (CT)?
    • Why is it important the the logs are append-only?
    • What can CT do to improve the PKI and what problems does it not (directly) solve?
• Authorization
  • Why is web authorization different from authentication?
  • What kinds of authorization problems do we need to solve?
  • What policy (should) address these problems?