threat-modeling.md

Threat Model Analysis for tokio-rs/tokio

Threat: Unbounded Task Spawning

• Description: An attacker exploits the application's task spawning logic to create an excessive number of Tokio tasks. By sending a flood of requests or malicious inputs, they overwhelm the Tokio runtime with tasks, exceeding resource limits. This is amplified by Tokio's efficiency in handling concurrent tasks, making it easier to spawn a large number quickly.
• Impact: Denial of Service (DoS), application crash, resource exhaustion (CPU, memory, threads), degraded performance for legitimate users.
• Tokio Component Affected: tokio::spawn, tokio::task::spawn, Tokio Runtime Task Scheduler.
• Risk Severity: High
• Mitigation Strategies:
  • Implement request rate limiting to control incoming requests.
  • Set limits on the maximum number of concurrent tasks the application can spawn.
  • Utilize bounded channels for task communication to introduce backpressure and prevent task queue buildup.
  • Employ Tokio's JoinSet to manage and limit the number of concurrently running tasks.
  • Implement monitoring of task creation rates and resource usage to detect anomalies.

Threat: Race Conditions in Asynchronous Code (Tokio Context)

• Description: An attacker exploits race conditions in the application's asynchronous code, which are made more complex and potentially harder to detect due to Tokio's concurrency model. By sending carefully timed concurrent requests, they trigger vulnerabilities in shared mutable state accessed by multiple Tokio tasks. This exploits the non-deterministic nature of asynchronous execution within the Tokio runtime.
• Impact: Data corruption, inconsistent application state, security vulnerabilities (e.g., privilege escalation, authentication bypass), unpredictable application behavior, potential crashes.
• Tokio Component Affected: Application code utilizing shared mutable state and asynchronous operations within the Tokio runtime, tokio::sync primitives (if misused).
• Risk Severity: High to Critical (depending on the impact of data corruption or security breach)
• Mitigation Strategies:
  • Minimize the use of shared mutable state in asynchronous code.
  • Employ appropriate synchronization primitives from tokio::sync (e.g., Mutex, RwLock, mpsc channels) correctly to protect shared mutable state.
  • Carefully design asynchronous workflows to avoid data races, considering the concurrent execution model of Tokio.
  • Utilize Rust's ownership and borrowing system to prevent data races at compile time where possible.
  • Implement rigorous testing specifically for concurrent code, including race condition detection tools and techniques suitable for asynchronous Rust.

Threat: Deadlocks in Asynchronous Context (Tokio Context)

• Description: An attacker crafts requests or inputs that intentionally trigger deadlock conditions in the application's asynchronous code, which can be more challenging to debug and prevent in Tokio's asynchronous environment compared to traditional threaded code. This involves exploiting resource acquisition patterns or synchronization logic using Tokio's asynchronous primitives to cause tasks to block each other indefinitely within the Tokio runtime.
• Impact: Denial of Service (DoS), application freeze, complete unresponsiveness, requiring application restart.
• Tokio Component Affected: Application code utilizing asynchronous synchronization primitives within the Tokio runtime, tokio::sync primitives (if misused).
• Risk Severity: High
• Mitigation Strategies:
  • Adhere to best practices for deadlock prevention in concurrent programming, adapted for asynchronous contexts.
  • Carefully design synchronization logic and resource acquisition order, paying attention to the asynchronous nature of Tokio operations.
  • Implement timeouts for asynchronous operations to prevent indefinite blocking and potential deadlocks.
  • Consider utilizing deadlock detection mechanisms or techniques if available and applicable to asynchronous Rust code.
  • Conduct thorough testing of concurrent code specifically for deadlock scenarios, simulating various asynchronous execution paths.

Threat: Asynchronous I/O Amplification DoS

• Description: An attacker leverages the high efficiency of Tokio's asynchronous I/O to amplify Denial of Service attacks. Tokio's ability to handle a massive number of concurrent connections makes it more susceptible to attacks like slowloris, where the attacker establishes many slow, incomplete connections to exhaust server resources.
• Impact: Denial of Service (DoS), server unresponsiveness, resource exhaustion (connection limits, memory, file descriptors), impacting availability for legitimate users.
• Tokio Component Affected: tokio::net (TCP listeners, sockets), Tokio Runtime I/O handling.
• Risk Severity: High
• Mitigation Strategies:
  • Implement strict connection limits and enforce maximum concurrent connections to prevent resource exhaustion.
  • Set aggressive timeouts for connection establishment, request headers, and request bodies to quickly discard slow or incomplete connections.
  • Employ load balancing and traffic shaping techniques to distribute and manage incoming traffic, mitigating the impact of DoS attempts.
  • Utilize firewalls and intrusion detection/prevention systems to identify and block malicious traffic patterns.
  • Monitor network connection metrics and analyze traffic patterns to detect and respond to suspicious activity.

Threat: Thread Pool Exhaustion (Tokio Runtime)

• Description: An attacker sends requests or inputs that force the application to perform blocking operations directly within Tokio tasks, without using tokio::task::spawn_blocking. This directly blocks the Tokio runtime's worker threads. Repeatedly triggering such blocking operations can exhaust the thread pool, preventing the Tokio runtime from making progress and leading to a severe Denial of Service.
• Impact: Denial of Service (DoS), application unresponsiveness, severe performance degradation, potential deadlocks within the Tokio runtime, rendering the application unusable.
• Tokio Component Affected: Tokio Runtime Thread Pool, tokio::task::spawn (when misused for blocking operations), application code performing blocking operations within asynchronous tasks.
• Risk Severity: High
• Mitigation Strategies:
  • Strictly avoid performing any blocking operations directly within asynchronous tasks running on the Tokio runtime.
  • Offload all blocking operations to dedicated thread pools using tokio::task::spawn_blocking, ensuring they do not block Tokio's worker threads.
  • Carefully configure the Tokio runtime with an appropriate number of worker threads based on the application's workload and hardware resources.
  • Implement monitoring of thread pool usage and actively identify tasks that are inadvertently blocking the thread pool.
  • Introduce timeouts and circuit breakers to prevent cascading failures and resource exhaustion due to thread pool saturation.

Threat: Vulnerabilities in Tokio or its Dependencies

• Description: An attacker exploits security vulnerabilities directly present within the Tokio runtime library itself or its core dependencies (e.g., mio). This could be a bug in Tokio's scheduler, networking implementation, or a low-level dependency. Exploiting such vulnerabilities can have a critical and widespread impact on any application using the affected version of Tokio.
• Impact: Remote Code Execution (RCE), Denial of Service (DoS), complete application compromise, potential for widespread impact across numerous applications utilizing the vulnerable Tokio version.
• Tokio Component Affected: Tokio Runtime core, tokio crate, core dependencies of tokio (e.g., mio).
• Risk Severity: Critical to High (depending on the specific vulnerability type, exploitability, and potential impact)
• Mitigation Strategies:
  • Maintain up-to-date versions of Tokio and all dependencies. Regularly update to the latest stable versions to benefit from security patches and bug fixes.
  • Implement automated dependency auditing using tools like cargo audit to proactively identify known vulnerabilities in Tokio and its dependency tree.
  • Subscribe to security advisories and vulnerability disclosure channels for Tokio and the Rust ecosystem to stay informed about potential security issues.
  • Actively contribute to the Tokio project and its security by reporting any identified bugs or potential security concerns and participating in security discussions within the community.
  • In the event of critical vulnerabilities being disclosed, promptly apply patches or consider downgrading to a known secure version if immediate updates are not feasible, following security best practices for incident response.