mitigations.md

Mitigation Strategies Analysis for tornadoweb/tornado

Mitigation Strategy: Leverage Tornado's Auto-escaping Template Engine

• Description:

  1. Identify all template rendering locations: Review your Tornado application code and identify all places where you are rendering templates using tornado.template.Template.generate() or tornado.web.RequestHandler.render(), render_string().
  2. Ensure variables are rendered within template tags: Verify that all dynamic data intended for display in HTML is being passed to the template and rendered using template tags like {{ variable }}.
  3. Avoid manual HTML string construction: Refrain from manually concatenating strings to build HTML output, especially when including user-provided data. This bypasses auto-escaping.
  4. Review template code: Inspect your template files (.html or similar) to confirm that dynamic content is consistently rendered using template tags and not directly embedded as plain text.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) - Reflected (High Severity): Mitigates reflected XSS by automatically encoding output, preventing injected scripts from being executed in the user's browser.
  • Cross-Site Scripting (XSS) - Stored (Medium Severity): Reduces the risk of stored XSS if data is escaped upon output, even if it wasn't sanitized on input. However, input sanitization is still crucial for robust protection.

• Impact:

  • XSS - Reflected (High Impact): Significantly reduces the risk of reflected XSS by default.
  • XSS - Stored (Medium Impact): Provides a layer of defense against stored XSS, but not a complete solution.

• Currently Implemented:

  • Yes, Globally Implemented: Tornado's auto-escaping is enabled by default for all templates rendered using RequestHandler.render() and render_string() throughout the application. This is a framework-level feature.

• Missing Implementation:

  • None: Auto-escaping is a default feature. However, developers need to be aware of it and avoid bypassing it by manually constructing HTML strings. Continuous code review is needed to ensure adherence.

Mitigation Strategy: Implement Content Security Policy (CSP) via Tornado Handlers

• Description:

  1. Define your CSP policy: Determine the appropriate CSP directives for your application. Start with a restrictive policy and gradually relax it as needed. Key directives include default-src, script-src, style-src, img-src, connect-src, frame-ancestors, etc. For example: default-src 'self'; script-src 'self' 'unsafe-inline' https://trusted-cdn.com; style-src 'self' 'unsafe-inline'; img-src 'self' data:;
  2. Configure CSP header in Tornado: Implement a custom RequestHandler method (e.g., set_default_headers()) or middleware to add the Content-Security-Policy header to all responses. This leverages Tornado's request handling mechanism to set headers.
  3. Test your CSP policy: Thoroughly test your CSP policy in a staging environment. Use browser developer tools to identify and resolve any CSP violations. Start with Content-Security-Policy-Report-Only header to monitor violations without blocking content initially.
  4. Deploy CSP policy: Once tested and refined, deploy the CSP policy by setting the Content-Security-Policy header in production.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) - Reflected and Stored (High Severity): CSP significantly reduces the impact of both reflected and stored XSS attacks by limiting the attacker's ability to execute injected scripts, even if they bypass other defenses.
  • Clickjacking (Medium Severity): frame-ancestors directive can mitigate clickjacking attacks by controlling where your application can be framed.
  • Data Injection Attacks (Low to Medium Severity): Can limit the impact of certain data injection attacks by restricting allowed sources for resources.

• Impact:

  • XSS - Reflected and Stored (High Impact): Provides a strong defense-in-depth layer against XSS.
  • Clickjacking (Medium Impact): Effectively mitigates clickjacking when frame-ancestors is properly configured.
  • Data Injection Attacks (Low to Medium Impact): Reduces the attack surface for certain injection attacks.

• Currently Implemented:

  • Partially Implemented: A basic CSP header is set in the base RequestHandler in app/base_handler.py, but it is very permissive (default-src 'self' 'unsafe-inline' 'unsafe-eval' data:;).

• Missing Implementation:

  • Refine CSP Policy: The current CSP policy needs to be significantly tightened. Remove 'unsafe-inline' and 'unsafe-eval' where possible. Specifically, script-src and style-src should be reviewed and made more restrictive.
  • Report-URI/report-to: Implement CSP reporting using report-uri or report-to directives to monitor and analyze CSP violations in production.

Mitigation Strategy: Enable Tornado's Built-in CSRF Protection

• Description:

  1. Set xsrf_cookies to True: In your Tornado application settings dictionary, ensure that xsrf_cookies is set to True. This enables CSRF protection globally using Tornado's built-in mechanism.
  2. Use @tornado.web.authenticated decorator: Apply the @tornado.web.authenticated decorator to all RequestHandler methods that handle state-changing operations (e.g., POST, PUT, DELETE requests). This decorator, provided by Tornado, automatically checks for a valid CSRF token.
  3. Include {% raw xsrf_form_html() %} in forms: In your HTML templates for forms that submit data via POST, include the {% raw xsrf_form_html() %} template tag within the <form> element. This Tornado template tag injects a hidden input field containing the CSRF token.
  4. Handle CSRF token in AJAX requests: For AJAX requests that modify server-side state, retrieve the CSRF token from the _xsrf cookie (set by Tornado) using JavaScript and include it in the request headers (e.g., X-XSRFToken).

• Threats Mitigated:

  • Cross-Site Request Forgery (CSRF) (High Severity): Protects against CSRF attacks by ensuring that state-changing requests originate from legitimate user actions within your application and not from malicious cross-site requests.

• Impact:

  • CSRF (High Impact): Effectively mitigates CSRF attacks when properly implemented across the application using Tornado's features.

• Currently Implemented:

  • Partially Implemented: xsrf_cookies is set to True in config/settings.py. The @tornado.web.authenticated decorator is used in some handlers, but not consistently across all state-changing operations. {% raw xsrf_form_html() %} is used in some forms, but not all. AJAX CSRF handling is not consistently implemented.

• Missing Implementation:

  • Consistent @tornado.web.authenticated Usage: Thoroughly review all RequestHandler methods that handle POST, PUT, DELETE requests and ensure the @tornado.web.authenticated decorator is applied to all of them.
  • {% raw xsrf_form_html() %} in all Forms: Ensure that {% raw xsrf_form_html() %} is included in all HTML forms that submit data via POST.
  • AJAX CSRF Token Handling: Implement consistent CSRF token handling for all AJAX requests that modify server-side state, leveraging the _xsrf cookie set by Tornado. Create a JavaScript utility function to retrieve the _xsrf cookie and set the X-XSRFToken header for AJAX requests.

Mitigation Strategy: Origin Validation for WebSocket Connections in Tornado Handlers

• Description:

  1. Implement open() method in WebSocket handler: Ensure your Tornado WebSocket handler class has an open() method, which is the entry point for WebSocket connections in Tornado.
  2. Retrieve Origin header: Inside the open() method, access the Origin header from the self.request.headers dictionary, which is Tornado's way of providing request information.
  3. Whitelist allowed origins: Create a list or set of allowed origins for your WebSocket connections. This should include the expected origin(s) of your application.
  4. Validate Origin header: Compare the Origin header value with your whitelist of allowed origins.
  5. Reject invalid origins: If the Origin header is not in the whitelist, close the WebSocket connection using self.close() and log the rejected connection attempt. self.close() is the Tornado method for closing WebSocket connections.

• Threats Mitigated:

  • Cross-Site WebSocket Hijacking (Medium Severity): Prevents malicious websites from establishing WebSocket connections to your application on behalf of unsuspecting users, potentially leading to unauthorized actions or data breaches.

• Impact:

  • Cross-Site WebSocket Hijacking (Medium Impact): Effectively mitigates cross-site WebSocket hijacking by ensuring connections originate from trusted origins, leveraging Tornado's WebSocket handling.

• Currently Implemented:

  • Not Implemented: Origin validation is not currently implemented in any WebSocket handlers in the project. WebSocket connections are accepted from any origin.

• Missing Implementation:

  • Implement Origin Validation in WebSocket Handlers: Modify all Tornado WebSocket handler classes to include origin validation in their open() methods as described above. Define a whitelist of allowed origins in the application configuration.

Mitigation Strategy: Configure Secure Session Cookies via Tornado cookie_settings

• Description:

  1. Configure cookie_settings in application settings: In your Tornado application settings dictionary, configure the cookie_settings dictionary. This is Tornado's mechanism for setting cookie attributes.
  2. Set httponly=True: Add or modify the httponly key within cookie_settings and set it to True. This will instruct Tornado to add the HttpOnly flag to session cookies it sets.
  3. Set secure=True: Add or modify the secure key within cookie_settings and set it to True. This will instruct Tornado to add the Secure flag to session cookies, ensuring they are only transmitted over HTTPS.
  4. Ensure HTTPS is enforced: Verify that your application is configured to enforce HTTPS for all communication, as the secure flag is only effective over HTTPS.

• Threats Mitigated:

  • Session Hijacking via XSS (Medium Severity): HttpOnly flag prevents client-side JavaScript from accessing session cookies, mitigating session hijacking through XSS vulnerabilities.
  • Session Hijacking via Man-in-the-Middle (MitM) Attacks (Medium Severity): Secure flag prevents session cookies from being transmitted over insecure HTTP connections, protecting against MitM attacks on non-HTTPS connections.

• Impact:

  • Session Hijacking via XSS (Medium Impact): Significantly reduces the risk of session hijacking via XSS.
  • Session Hijacking via MitM (Medium Impact): Effectively mitigates session hijacking via MitM attacks when HTTPS is enforced.

• Currently Implemented:

  • Partially Implemented: secure=True is set in cookie_settings in config/settings.py. However, httponly=True is missing.

• Missing Implementation:

  • Enable httponly=True: Add httponly=True to the cookie_settings in config/settings.py to enable the HttpOnly flag for session cookies managed by Tornado.

Mitigation Strategy: Request Rate Limiting (Leveraging Tornado's Asynchronous Nature)

• Description:

  1. Choose a rate limiting mechanism: Select a rate limiting approach. Options include:
     • Middleware: Implement custom middleware to intercept requests and apply rate limiting logic within Tornado's middleware framework.
     • Decorator: Create a decorator that can be applied to individual RequestHandler methods to enforce rate limits, utilizing Tornado's decorator capabilities.
     • Third-party libraries: Utilize existing Tornado rate limiting libraries designed for asynchronous environments.
  2. Define rate limits: Determine appropriate rate limits for different endpoints or user roles. Consider factors like request frequency, resource consumption, and expected user behavior.
  3. Implement rate limiting logic: Implement the chosen rate limiting mechanism, ensuring it's compatible with Tornado's asynchronous request handling. This typically involves:
     • Identifying clients: Use IP addresses, user IDs, or API keys to identify clients.
     • Tracking request counts: Maintain counters for each client within a time window (e.g., using in-memory dictionaries, Redis, Memcached), ensuring thread-safety if needed in a multi-process Tornado setup.
     • Enforcing limits: Check the request count for each client before processing a request. If the limit is exceeded, return a 429 Too Many Requests error response using Tornado's set_status and finish methods.
     4. Customize error response: Provide a clear and informative 429 error response to clients when rate limits are exceeded, potentially including information about retry-after time, using Tornado's response handling.

• Threats Mitigated:

  • Denial of Service (DoS) - Brute-Force Attacks (High Severity): Limits the rate of requests, making brute-force attacks (e.g., password guessing, resource exhaustion) significantly less effective.
  • Denial of Service (DoS) - Application-Level Attacks (Medium Severity): Protects against application-level DoS attacks that attempt to overwhelm the server with a high volume of legitimate-looking requests. Tornado's asynchronous nature helps in handling many connections, but rate limiting is still crucial.

• Impact:

  • DoS - Brute-Force Attacks (High Impact): Effectively mitigates brute-force attacks.
  • DoS - Application-Level Attacks (Medium Impact): Reduces the impact of application-level DoS attacks.

• Currently Implemented:

  • Not Implemented: Request rate limiting is not currently implemented anywhere in the application. There are no mechanisms to limit the number of requests from a single IP or user.

• Missing Implementation:

  • Implement Global Rate Limiting Middleware: Implement a middleware component within Tornado's middleware framework that applies rate limiting to all or critical endpoints based on IP address.
  • Endpoint-Specific Rate Limiting: Consider implementing more granular rate limiting for specific endpoints that are more resource-intensive or prone to abuse, potentially using decorators on Tornado RequestHandler methods.