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attack-surface.md

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Attack Surface Analysis for ruby-concurrency/concurrent-ruby

Attack Surface: Race Conditions

  • Description: Unsynchronized access to shared resources by multiple threads, leading to unpredictable and potentially exploitable behavior.
    • How concurrent-ruby Contributes: Provides concurrency primitives (threads, actors, promises, etc.) that, if used incorrectly, increase the likelihood of race conditions. The library's core functionality enables concurrent execution, making race conditions possible.
    • Example: Two threads concurrently modify a shared hash (without using Concurrent::Map or proper locking) using concurrent-ruby's Future. One thread might add a key-value pair, while another removes a key-value pair, leading to an inconsistent state or a missing entry.
    • Impact: Data corruption, inconsistent application state, security bypass (e.g., bypassing authorization checks), unexpected program termination.
    • Risk Severity: Critical (in many cases, can lead to complete compromise) to High (depending on the specific shared resource).
    • Mitigation Strategies:
      • Use Atomics: Employ concurrent-ruby's Atomic types (e.g., AtomicFixnum, AtomicBoolean, AtomicReference) for all shared mutable data. Ensure all operations are truly atomic.
      • Use Synchronization Primitives: Utilize Mutex, ReadWriteLock, Semaphore, and Condition appropriately to protect critical sections. Choose the most granular lock possible.
      • Immutable Data Structures: Favor immutable data structures. If modification is needed, create a new copy.
      • Message Passing (Actors): Use the Actor model (Agent in concurrent-ruby) to encapsulate state and communicate via messages, avoiding direct shared memory.
      • Code Review: Thoroughly review code for potential race conditions, focusing on shared variable access.
      • Stress Testing: Use stress testing tools to expose race conditions.

Attack Surface: Deadlocks

  • Description: Two or more threads are blocked indefinitely, waiting for each other to release resources, leading to a denial-of-service (DoS).
    • How concurrent-ruby Contributes: Provides synchronization primitives (Mutex, Semaphore, Channel) that, if used incorrectly (e.g., creating circular dependencies), can directly lead to deadlocks.
    • Example: Thread A acquires a concurrent-ruby Mutex for resource X and then tries to acquire a concurrent-ruby Mutex for resource Y. Simultaneously, Thread B acquires the Mutex for resource Y and then tries to acquire the Mutex for resource X. Both threads are now blocked indefinitely.
    • Impact: Application freeze, denial of service.
    • Risk Severity: High (can completely halt application functionality).
    • Mitigation Strategies:
      • Lock Ordering: Establish a strict global order for acquiring locks. If all threads always acquire locks in the same order, circular dependencies are impossible.
      • Timeouts: Use try_lock with a timeout instead of lock. If a thread cannot acquire a lock within a specified time, it can back off.
      • Deadlock Detection Tools: Employ tools that can detect deadlocks during development and testing.
      • Careful Design: Design concurrent code to minimize the need for holding multiple locks simultaneously. Consider finer-grained locks or alternative concurrency patterns (e.g., message passing with Agent).
      • Avoid Nested Locking: Minimize or eliminate nested locking.

Attack Surface: Resource Exhaustion (DoS)

  • Description: Uncontrolled creation of threads or other concurrent resources, leading to system instability or crashes.
    • How concurrent-ruby Contributes: Provides mechanisms for creating threads (e.g., ThreadPoolExecutor) and other concurrent objects (e.g., Promise, Future, Channel, TimerTask). Misuse directly leads to excessive resource consumption.
    • Example: An application uses an unbounded concurrent-ruby ThreadPoolExecutor and receives a flood of requests. The executor creates a new thread for each request, exhausting system memory.
    • Impact: Denial of service, application crash, system instability.
    • Risk Severity: High (can render the application unusable).
    • Mitigation Strategies:
      • Bounded Thread Pools: Use bounded thread pools (e.g., FixedThreadPool, CachedThreadPool with appropriate maximum sizes).
      • Resource Limits: Set limits on the number of Promise, Future, Channel, and TimerTask objects.
      • Proper Resource Management: Ensure that concurrent resources from concurrent-ruby are properly released when no longer needed (e.g., cancelling TimerTask instances, closing Channels).
      • Rate Limiting: Implement rate limiting to prevent overload.
      • Circuit Breakers: Use circuit breakers to prevent cascading failures.
      • Monitoring: Monitor resource usage (CPU, memory, threads).