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Threat Model Analysis for tornadoweb/tornado

Threat: Asynchronous Reentrancy Issues

  • Description: An attacker might exploit race conditions in asynchronous handlers. By sending concurrent requests that trigger overlapping asynchronous operations, the attacker can manipulate shared application state in unintended ways. For example, in an e-commerce application, an attacker might be able to purchase an item that is out of stock by exploiting a race condition in the inventory update logic.
  • Impact: Data corruption, security bypass (e.g., unauthorized access, privilege escalation), inconsistent application state, denial of service due to application errors.
  • Tornado Component Affected: tornado.web.RequestHandler (asynchronous handlers), asyncio or tornado.gen (asynchronous programming constructs).
  • Risk Severity: High
  • Mitigation Strategies:
    • Design asynchronous handlers to be reentrant-safe, minimizing shared mutable state.
    • Use asynchronous locking mechanisms (asyncio.Lock, tornado.locks.Lock) to protect critical sections of code that modify shared state.
    • Implement atomic operations where possible to avoid race conditions.
    • Thoroughly test asynchronous handlers under concurrent load to identify and fix reentrancy issues.
    • Employ code reviews to identify potential reentrancy vulnerabilities.

Threat: Blocking the Event Loop (Denial of Service)

  • Description: An attacker can cause a Denial of Service by triggering blocking operations within request handlers. For instance, by sending requests that cause the application to perform synchronous database queries or CPU-intensive tasks directly in the event loop, the attacker can make the application unresponsive to legitimate requests.
  • Impact: Denial of Service, application unresponsiveness, degraded performance for all users.
  • Tornado Component Affected: tornado.ioloop.IOLoop (event loop), tornado.web.RequestHandler (handlers executing blocking code).
  • Risk Severity: High
  • Mitigation Strategies:
    • Ensure all I/O operations (database access, network requests, file I/O) are asynchronous using Tornado's asynchronous libraries or wrappers.
    • Offload CPU-intensive tasks to separate processes or threads using tornado.process.Subprocess or concurrent.futures.ThreadPoolExecutor.
    • Implement timeouts for external operations to prevent indefinite blocking.
    • Monitor event loop latency and identify any blocking operations using Tornado's instrumentation or external monitoring tools.
    • Conduct performance testing to identify and eliminate blocking code paths.

Threat: WebSocket Injection Attacks

  • Description: An attacker can send malicious payloads within WebSocket messages. If the application doesn't properly sanitize or validate these messages before processing or echoing them back to other clients, the attacker can inject code or commands. For example, an attacker might inject JavaScript code that gets executed in another user's browser if the application reflects WebSocket messages without proper encoding.
  • Impact: Cross-site scripting (in WebSocket context), data manipulation, potentially command injection if WebSocket data is used in system commands on the server.
  • Tornado Component Affected: tornado.websocket.WebSocketHandler (WebSocket handling).
  • Risk Severity: High
  • Mitigation Strategies:
    • Implement strict input validation and sanitization of all data received via WebSockets on the server-side.
    • Use context-aware output encoding when displaying WebSocket data to clients to prevent interpretation of malicious code.
    • Consider using secure message formats and protocols for WebSocket communication.
    • Regularly review WebSocket message handling logic for potential injection vulnerabilities.

Threat: WebSocket Resource Exhaustion (Denial of Service)

  • Description: An attacker can initiate a large number of WebSocket connections or send a high volume of messages through existing connections to overwhelm server resources. By exhausting memory, CPU, or network bandwidth, the attacker can cause a Denial of Service, making the application unavailable to legitimate users.
  • Impact: Denial of Service, application unresponsiveness, server crashes.
  • Tornado Component Affected: tornado.websocket.WebSocketHandler, tornado.httpserver.HTTPServer (connection handling).
  • Risk Severity: High
  • Mitigation Strategies:
    • Implement rate limiting on WebSocket connections and messages per client and globally.
    • Set limits on the maximum number of concurrent WebSocket connections allowed.
    • Implement connection timeouts and idle connection management to automatically close inactive WebSocket connections and release resources.
    • Monitor WebSocket connection metrics (number of connections, message rate, resource usage) and set up alerts for unusual activity.
    • Use a reverse proxy or load balancer in front of Tornado to distribute WebSocket connection load and provide additional protection against DDoS attacks.

Threat: Slowloris/Slow POST Denial of Service (Asynchronous Context)

  • Description: An attacker sends slow, incomplete HTTP requests (headers or body) to keep connections open for an extended period. In Tornado's asynchronous environment, if connection timeouts are not properly configured, these slow connections can accumulate, exhausting server resources (file descriptors, memory) and preventing the server from accepting new legitimate connections.
  • Impact: Denial of Service, application unresponsiveness.
  • Tornado Component Affected: tornado.httpserver.HTTPServer (connection handling, timeouts).
  • Risk Severity: High
  • Mitigation Strategies:
    • Configure appropriate timeouts for request headers (HTTPServer.header_timeout) and bodies (HTTPServer.body_timeout) in Tornado's HTTPServer settings.
    • Use a reverse proxy (like Nginx or HAProxy) in front of Tornado, which is often more effective at handling slowloris attacks and can provide connection limiting and timeouts.
    • Implement connection limits at the application or proxy level to restrict the number of concurrent connections from a single IP address or in total.
    • Monitor server resource usage (file descriptors, memory, CPU) and set up alerts for resource exhaustion.

Threat: Insecure Configuration of Tornado Server

  • Description: Misconfiguration of the Tornado HTTP server or application settings can introduce various vulnerabilities. Examples include enabling debug mode in production, exposing unnecessary endpoints or administrative interfaces, using weak or default secret keys, or not enforcing HTTPS.
  • Impact: Information disclosure (debug mode, exposed endpoints), security bypass (weak secrets), data interception (lack of HTTPS), unauthorized access.
  • Tornado Component Affected: tornado.web.Application (settings), tornado.httpserver.HTTPServer (configuration).
  • Risk Severity: High
  • Mitigation Strategies:
    • Disable debug mode in production (debug=False in tornado.web.Application).
    • Carefully configure listening interfaces and ports to expose only necessary services.
    • Use strong, randomly generated secret keys for security features like cookies, CSRF protection, and session management.
    • Enforce HTTPS for all communication by configuring SSL/TLS certificates and redirecting HTTP to HTTPS.
    • Regularly review and audit Tornado server and application configurations against security best practices and hardening guidelines.
    • Use configuration management tools to ensure consistent and secure configurations across environments.