Lecture Notes on Race Conditions

Definition

• Race Condition: Occurs when two events happen nearly simultaneously in an application without the application accounting for these simultaneous operations.
• Commonly checked by developers but unexpected outcomes can occur when multiple events interplay unexpectedly.

Types of Race Conditions

• TOCTOU (Time of Check to Time of Use) Attack:
  • The application retrieves a value from the system, performs a function, but an unseen process may change the value before use.

Practical Example

• Scenario: Two users moving money between two accounts (Account A and Account B).

  1. Initial State: Both Account A and B have $100.
  2. User 1 Action: Transfers $50 to Account B.
     • Account A: $100
     • Account B: $150
  3. User 2 Action: Also transfers $50 to Account B.
     • Account A: $100
     • Account B: $200
  4. User 1 Action: Withdraws $50 from Account A.
     • Account A: $50
     • Account B: $200
  5. User 2 Action: Withdraws $50 from Account A.
     • From User 2's perspective:
       • Account A: $50
       • Account B: $200
     • Actual Outcome: Account A should have $0, but due to race condition, it shows $50.

Real-World Examples

Mars Rover - Spirit (2004)

• Issue: File system error caused rover to continuously reboot (reboot loop).
• Solution: Developers sent additional code to bypass the error.

Tesla Model 3 (Pwn2Own 2023)

• Type: TOCTOU attack on infotainment system via Bluetooth.
• Outcome: Privilege escalation to root user, attackers won $100,000 and the car.

Key Takeaways

• Race conditions can lead to significant and unintended consequences if not properly managed.
• Developers must account for the potential of simultaneous events that may interfere with application logic.
• Real-world cases highlight the importance of robust error handling and updates to prevent race conditions.