mitigations.md

Mitigation Strategies Analysis for dotnet/reactive

Mitigation Strategy: Backpressure Handling (Rx.NET Operators)

Description:

1. Identify High-Volume Observables: Analyze data flow to pinpoint Observables producing high-rate or bursty data.
2. Choose Appropriate Operators: Select Rx.NET operators for backpressure:
   • Buffer(count): Batches items into fixed-size groups.
   • Buffer(timeSpan): Batches items within a time window.
   • Sample(timeSpan): Emits the last item within a time window.
   • Throttle(timeSpan): Emits an item, then ignores subsequent items for a duration.
   • Debounce(timeSpan): Emits an item after a period of silence.
   • Window(count/timeSpan): Emits Observables of buffered items.
3. Strategic Operator Placement: Insert operators before computationally expensive or resource-limited operations.
4. Thorough Testing: Create tests simulating high-volume scenarios to verify backpressure.

Threats Mitigated:

• Denial of Service (DoS) via Uncontrolled Observables: (Severity: High)
• Resource Exhaustion (CPU, Memory, Threads): (Severity: High)
• Application Unresponsiveness: (Severity: Medium)

Impact:

• DoS: Risk significantly reduced (High impact).
• Resource Exhaustion: Risk significantly reduced (High impact).
• Application Unresponsiveness: Risk moderately reduced (Medium impact).

Currently Implemented: Partially. Debounce on search input (SearchService.cs). Throttle on sensor data (SensorDataProcessor.cs).

Missing Implementation: Missing on stock price feed (StockPriceService.cs) and user activity log (UserActivityLogger.cs).

Mitigation Strategy: Subscription Timeouts (Rx.NET Timeout Operator)

Description:

1. Identify Potentially Hanging Observables: Find Observables that might not complete or emit values (e.g., network requests, long-running operations).
2. Apply Timeout Operator: Use the Timeout(TimeSpan) operator on these Observables. Set a reasonable timeout value based on expected behavior.
3. Handle TimeoutException: Use a Catch block to handle the TimeoutException that is thrown when the timeout occurs. Implement appropriate error handling (retry, log, notify user).

Threats Mitigated:

• Hanging Subscriptions: (Severity: Medium) - Prevents indefinite blocking.
• Resource Exhaustion (Threads): (Severity: Medium) - Releases resources held by hanging subscriptions.

Impact:

• Hanging Subscriptions: Risk significantly reduced (High impact).
• Resource Exhaustion: Risk moderately reduced (Medium impact).

Currently Implemented: Implemented for network requests (NetworkService.cs).

Missing Implementation: Not consistently applied to other potentially long-running operations.

Mitigation Strategy: Error Handling with Rx.NET Operators

Description:

1. Catch for Specific Exceptions: Use Catch to handle specific exceptions within the Observable chain. Avoid catching generic Exception.
2. Retry for Transient Errors: Use Retry for automatic retries on transient errors (e.g., network issues). Consider a backoff strategy.
3. OnErrorResumeNext for Fallbacks: Use OnErrorResumeNext to switch to a different Observable sequence on error, providing a fallback.
4. Test Error Scenarios: Create unit tests that specifically test error handling within your Observable chains.

Threats Mitigated:

• Unhandled Exceptions: (Severity: High)
• Application Crashes: (Severity: High)
• Inconsistent State: (Severity: Medium)
• Masked Errors: (Severity: Low)

Impact:

• Unhandled Exceptions: Risk significantly reduced (High impact).
• Application Crashes: Risk significantly reduced (High impact).
• Inconsistent State: Risk moderately reduced (Medium impact).
• Masked Errors: Risk significantly reduced (High impact).

Currently Implemented: Partially. Catch used in some places.

Missing Implementation: Retry and OnErrorResumeNext not widely used. Comprehensive review needed. Error handling not consistently tested.

Mitigation Strategy: Safe Replay Subject Usage (Rx.NET ReplaySubject Parameters)

Description:

1. Assess Necessity: Determine if ReplaySubject or BehaviorSubject is truly required.
2. Limit Buffer Size: Use the ReplaySubject constructor with bufferSize to limit cached values.
3. Time-Based Expiration: Use the ReplaySubject constructor with window (a TimeSpan) for time-based caching.
4. Avoid Sensitive Data: Never store sensitive data directly in a ReplaySubject or BehaviorSubject.
5. Clear on Invalidation: Explicitly clear the ReplaySubject (using OnCompleted or a new instance) when data is invalid.

Threats Mitigated:

• Replay Attacks: (Severity: High)
• Information Disclosure: (Severity: High)
• Stale Data Issues: (Severity: Medium)

Impact:

• Replay Attacks: Risk significantly reduced (High impact).
• Information Disclosure: Risk significantly reduced (High impact).
• Stale Data Issues: Risk significantly reduced (High impact).

Currently Implemented: Partially. ReplaySubject in user profile caching (UserProfileService.cs) has limited buffer size, but no time-based expiration.

Missing Implementation: No time-based expiration in UserProfileService.cs. No explicit clearing. Review all ReplaySubject/BehaviorSubject uses.

Mitigation Strategy: Using TakeUntil for unsubscription

Description:

1. Identify trigger: Find observable that will emit value when unsubscription should happen.
2. Apply TakeUntil Operator: Use the TakeUntil(IObservable<T>) operator on main Observable. Pass trigger observable as parameter.
3. Test unsubscription: Create unit tests that specifically test unsubscription logic.

Threats Mitigated:

• Memory Leaks: (Severity: Medium) - Prevents subscriptions from lingering indefinitely and consuming memory.
• Resource Exhaustion (Threads): (Severity: Medium) - Reduces the number of threads potentially blocked by long-running subscriptions.

Impact:

• Memory Leaks: Risk significantly reduced (High impact).
• Resource Exhaustion: Risk moderately reduced (Medium impact).

Currently Implemented: Not implemented.

Missing Implementation: Not consistently used for component lifecycle management.