CSRF
What Is CSRF?
Forces user to execute unwanted actions using their authenticated session.
1. User logs into bank.com
2. User visits evil.com
3. Evil.com sends: <img src="bank.com/transfer?to=attacker&amount=1000">
4. Browser sends cookie → bank processes transfer!
Prevention
- CSRF tokens (Synchronizer Token Pattern)
- SameSite cookie attribute
- Origin/Referer header checks
- Double-submit cookie pattern
Key Points
- Understanding CSRF is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Best Practices
Key Principles
- Follow SOLID principles
- Write clean, readable code
- Test thoroughly
- Document decisions
- Monitor in production
Implementation
- Start simple, refactor as needed
- Use established patterns
- Consider trade-offs
- Review with peers
Continuous Improvement
- Learn from incidents
- Update documentation
- Share knowledge
- Mentor others
Key Points
- Understanding CSRF is essential for production systems
- Always consider scalability and maintainability
- Test thoroughly before deploying to production
- Monitor performance and set up alerting
Common Patterns
- Validation: Always validate input at the boundary
- Error Handling: Use structured error responses
- Logging: Log key events for debugging
- Testing: Unit, integration, and load tests
- Documentation: Keep docs updated with code changes
Practice Problems
Design and implement a solution for CSRF in a backend system. Consider scalability, error handling, and production readiness.
Solution
// CSRF implementation
// Key aspects: validation, error handling, logging, testing
public class CSRF {
// Production-ready implementation
}Identify and handle edge cases for CSRF. What happens under high load, with invalid input, or during failures?
Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotencyWrite a testing strategy for CSRF. Include unit tests, integration tests, and performance tests.
Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injectionQuiz
1. CSRF attacks use?
2. CSRF prevention includes?
3. What is the primary purpose of CSRF?
4. What is a common mistake when implementing CSRF?
Flashcards
Question
CSRF attack?
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Answer
Forces user to make requests using their session
Question
CSRF prevention?
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Answer
CSRF tokens, SameSite cookies
Question
What is CSRF?
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Answer
CSRF is a key concept in backend development.
Question
When to use CSRF?
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Answer
Use CSRF when building production systems that require reliability, scalability, and maintainability.
Question
CSRF best practices
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Answer
Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.
Revision Notes
Key Takeaways
- 1.CSRF uses existing session for unwanted actions
- 2.Prevent: CSRF tokens, SameSite cookies
- 3.Check Origin/Referer headers
- 4.State-changing operations at risk
Interview Tips
- •Explain CSRF attacks
- •Know prevention methods
Cheat Sheet
CSRF
- Forces actions using user session
- Prevent: CSRF tokens, SameSite cookies
- Check: Origin/Referer headers
- Risk: state-changing operations