mitigations.md

Mitigation Strategies Analysis for pallets/flask

Mitigation Strategy: Securely Configure SESSION_COOKIE_HTTPONLY (Flask Sessions)

• Description:

  1. Access Flask Configuration: Open your Flask application's configuration file (e.g., config.py or within your main app file).
  2. Set SESSION_COOKIE_HTTPONLY: Add or modify the SESSION_COOKIE_HTTPONLY configuration variable within your Flask app's configuration and set it to True.

     app.config['SESSION_COOKIE_HTTPONLY'] = True

  3. Restart Flask Application: Restart your Flask application server for the configuration to be applied.
  4. Verification (Developer): Use browser developer tools to inspect the Set-Cookie header of your application's session cookie after login. Confirm the HttpOnly flag is present, indicating Flask is correctly setting the cookie attribute.

• List of Threats Mitigated:

  • Cross-Site Scripting (XSS) based Session Hijacking - Medium to High Severity: If XSS vulnerabilities exist in your Flask application, attackers might use JavaScript to try and steal session cookies. HttpOnly prevents JavaScript access, mitigating this attack vector specifically for Flask's session cookies.

• Impact:

  • XSS Session Hijacking Mitigation - High Impact: Significantly reduces the risk of session hijacking via XSS attacks targeting Flask's session management.

• Currently Implemented:

  • Yes, Implemented in config.py: SESSION_COOKIE_HTTPONLY is set to True in the config.py file used for production Flask deployments.

• Missing Implementation:

  • None: This Flask-specific session security setting is currently implemented in production. Verify in staging/development environments for consistency.

Mitigation Strategy: Securely Configure SESSION_COOKIE_SECURE (Flask Sessions)

• Description:

  1. Access Flask Configuration: Open your Flask application's configuration file.
  2. Set SESSION_COOKIE_SECURE: Add or modify the SESSION_COOKIE_SECURE configuration variable in your Flask app's configuration and set it to True.

     app.config['SESSION_COOKIE_SECURE'] = True

  3. Ensure HTTPS for Flask Application: This setting requires your Flask application to be served over HTTPS. Configure your web server (e.g., Nginx, Apache) to handle HTTPS and ensure Flask is accessed via HTTPS URLs.
  4. Restart Flask Application & Web Server: Restart both your Flask application server and your web server for the configuration to take effect.
  5. Verification (Developer): Access your Flask application via HTTPS, log in, and use browser developer tools to inspect the Set-Cookie header. Confirm the Secure flag is present. Access via HTTP should not send the session cookie.

• List of Threats Mitigated:

  • Man-in-the-Middle (MitM) Session Hijacking - High Severity: If Flask sessions are transmitted over HTTP, attackers on the network can intercept session cookies. SESSION_COOKIE_SECURE ensures Flask session cookies are only sent over HTTPS, protecting against MitM attacks targeting Flask sessions.

• Impact:

  • MitM Session Hijacking Mitigation - High Impact: Effectively prevents session cookie theft via network sniffing for Flask sessions when HTTPS is correctly configured.

• Currently Implemented:

  • Yes, Implemented in config.py for Production: SESSION_COOKIE_SECURE is set to True in config.py for production Flask deployments. HTTPS is enforced at the load balancer.

• Missing Implementation:

  • Staging Environment Verification: Confirm SESSION_COOKIE_SECURE is also correctly configured and functioning in the staging Flask environment to mirror production.

Mitigation Strategy: Securely Configure SESSION_COOKIE_SAMESITE (Flask Sessions)

• Description:

  1. Access Flask Configuration: Open your Flask application's configuration file.
  2. Set SESSION_COOKIE_SAMESITE: Add or modify the SESSION_COOKIE_SAMESITE configuration variable in your Flask app's configuration. Set it to 'Lax' or 'Strict'. 'Lax' is generally recommended for a balance of security and usability with Flask applications.

     app.config['SESSION_COOKIE_SAMESITE'] = 'Lax'

  3. Restart Flask Application: Restart your Flask application server.
  4. Verification (Developer): Use browser developer tools to inspect the Set-Cookie header for your Flask session cookie. Verify the SameSite attribute is present and set to your chosen value.

• List of Threats Mitigated:

  • Cross-Site Request Forgery (CSRF) targeting Flask Sessions - Medium Severity: CSRF attacks can potentially exploit Flask sessions if the SameSite attribute is not set. SESSION_COOKIE_SAMESITE helps mitigate CSRF attacks specifically against Flask's session mechanism.

• Impact:

  • CSRF Mitigation for Flask Sessions - Medium Impact: Provides a layer of defense against CSRF attacks targeting Flask sessions, especially when combined with Flask-WTF CSRF protection.

• Currently Implemented:

  • No, Not Implemented: SESSION_COOKIE_SAMESITE is not explicitly set in the Flask application's configuration. Flask is using browser defaults.

• Missing Implementation:

  • config.py Configuration: Add SESSION_COOKIE_SAMESITE to config.py for production and staging Flask environments. Start with 'Lax' and test for any issues in cross-site interactions within your Flask application.

Mitigation Strategy: Generate and Securely Manage SECRET_KEY (Flask Sessions, Flask-WTF)

• Description:

  1. Generate Strong SECRET_KEY: Use Python's secrets module to generate a cryptographically secure, long, random SECRET_KEY.

     import secrets
     secret_key = secrets.token_hex(32)

  2. Secure Storage (External to Flask Code): Do not hardcode the SECRET_KEY in your Flask application code. Use environment variables, a secrets manager (e.g., AWS Secrets Manager, HashiCorp Vault), or secure configuration files outside of your version control.
  3. Load into Flask Configuration: Load the SECRET_KEY from your secure storage into your Flask application's configuration. Example using environment variables:

     import os
     app.config['SECRET_KEY'] = os.environ.get('FLASK_SECRET_KEY')

  4. Regular Rotation (Flask Best Practice): Implement a process to periodically rotate the SECRET_KEY used by your Flask application. This involves generating a new key, updating secure storage, and redeploying the Flask application with the new configuration.

• List of Threats Mitigated:

  • Flask Session Hijacking (Weak/Compromised SECRET_KEY) - High Severity: A weak or compromised SECRET_KEY allows attackers to forge Flask session cookies, gaining unauthorized access to accounts managed by your Flask application.
  • Flask-WTF CSRF Bypass (Weak/Compromised SECRET_KEY) - Medium Severity: If using Flask-WTF for CSRF protection, a weak SECRET_KEY can weaken the security of CSRF tokens generated by Flask-WTF.

• Impact:

  • Flask Session Hijacking Mitigation - High Impact: A strong, securely managed SECRET_KEY is fundamental to the security of Flask's session management and related security features like Flask-WTF CSRF protection.
  • Flask-WTF CSRF Reinforcement - Medium Impact: Strengthens CSRF protection when using Flask-WTF in your application.

• Currently Implemented:

  • Partially Implemented - Environment Variable: The SECRET_KEY for the Flask application is loaded from an environment variable (FLASK_SECRET_KEY) in production.

• Missing Implementation:

  • Strong Key Generation Verification: Verify the current SECRET_KEY was generated using a cryptographically secure method and is sufficiently random and long for Flask's security needs.
  • Flask SECRET_KEY Rotation Strategy: A formal rotation strategy for the Flask SECRET_KEY is not currently defined or implemented. This should be added as a proactive security measure for the Flask application.
  • Secrets Management System (Flask Enhancement): Consider migrating from environment variables to a dedicated secrets management system for enhanced security, auditing, and centralized management of the Flask application's SECRET_KEY, especially in larger deployments.

Mitigation Strategy: Implement CSRF Protection with Flask-WTF

• Description:

  1. Install Flask-WTF: If not already installed, add Flask-WTF to your project dependencies: pip install Flask-WTF.
  2. Initialize CSRF Protection in Flask App: In your Flask application initialization, enable CSRF protection using CSRFProtect(app).

     from flask_wtf.csrf import CSRFProtect
     csrf = CSRFProtect(app)

  3. Include CSRF Tokens in Flask Forms: In your Jinja2 templates for forms that modify data (e.g., POST, PUT, DELETE requests), include the CSRF token using form.hidden_tag() (assuming you are using Flask-WTF forms).

     <form method="POST">
         {{ form.hidden_tag() }}
         {# Form fields here #}
         <button type="submit">Submit</button>
     </form>

  4. Flask-WTF Automatic Validation: Flask-WTF automatically validates CSRF tokens on form submissions. Ensure your Flask routes handling form submissions are correctly processing Flask-WTF forms.

• List of Threats Mitigated:

  • Cross-Site Request Forgery (CSRF) - Medium Severity: CSRF attacks can trick users into performing unintended actions on your Flask application. Flask-WTF's CSRF protection, using tokens synchronized with the Flask session, effectively mitigates CSRF vulnerabilities in your Flask application.

• Impact:

  • CSRF Mitigation for Flask Application - High Impact: Flask-WTF provides robust CSRF protection, significantly reducing the risk of CSRF attacks against your Flask application's forms and state-changing requests.

• Currently Implemented:

  • Yes, Implemented with Flask-WTF: Flask-WTF is integrated into the project, and CSRF protection is enabled using CSRFProtect(app). Forms are designed using Flask-WTF and include CSRF tokens.

• Missing Implementation:

  • CSRF Token Coverage Audit: Audit all forms and state-changing routes in your Flask application to ensure CSRF protection is consistently applied using Flask-WTF. Verify that form.hidden_tag() is used in all relevant Jinja2 templates and that Flask-WTF form handling is correctly implemented in Flask routes.

Mitigation Strategy: Disable Flask Debug Mode in Production

• Description:

  1. Identify Debug Mode Setting: Locate where Flask debug mode is configured in your application. This might be in your main application file (app.debug = True) or via environment variables (FLASK_DEBUG=1).
  2. Disable Debug Mode for Production: Ensure debug mode is disabled in your production environment. This is critical.
     • Configuration File: In your config.py (for production), ensure app.debug = False or remove any explicit setting (it defaults to False).
     • Environment Variables: In your production deployment environment, ensure the FLASK_DEBUG environment variable is either not set or set to 0 or False.
  3. Verify Debug Mode is Disabled (Production): After deploying to production, access your Flask application and intentionally trigger an error (e.g., access a non-existent route). Verify that you see a generic error page and not the Flask debugger or detailed traceback.

• List of Threats Mitigated:

  • Information Disclosure (High Severity in Debug Mode): Flask debug mode exposes sensitive information like code snippets, configuration details, and internal paths in error pages. This information can be valuable to attackers for reconnaissance and exploiting vulnerabilities.
  • Remote Code Execution (High Severity in Debug Mode - Pin Exploit): In older versions of Flask or with specific configurations, debug mode could be vulnerable to "PIN exploits" allowing remote code execution. While less common now, disabling debug mode eliminates this risk entirely.

• Impact:

  • Information Disclosure Mitigation - High Impact: Disabling debug mode prevents the exposure of sensitive application details in production error pages, significantly reducing information leakage.
  • Remote Code Execution Risk Reduction - High Impact: Eliminates the potential for remote code execution vulnerabilities associated with debug mode.

• Currently Implemented:

  • Yes, Implemented in Production Configuration: Flask debug mode is explicitly disabled in the config.py file used for production deployments (app.debug = False).

• Missing Implementation:

  • Staging/Development Environment Review: While disabled in production, review staging and development environments. While debug mode can be useful in development, consider if it's unnecessarily enabled in staging and if it aligns with your staging environment's security posture. Ideally, staging should closely mirror production settings.

Mitigation Strategy: Implement Custom Error Pages in Flask

• Description:

  1. Create Error Handler Functions: Define Python functions to handle specific HTTP error codes (e.g., 404, 500) using Flask's @app.errorhandler decorator.

     from flask import render_template
     
     @app.errorhandler(404)
     def page_not_found(error):
         return render_template('404.html'), 404
     
     @app.errorhandler(500)
     def internal_server_error(error):
         return render_template('500.html'), 500

  2. Create Error Templates: Create Jinja2 templates (e.g., 404.html, 500.html) for your custom error pages. These templates should be user-friendly and avoid revealing sensitive application details.
  3. Register Error Handlers with Flask App: Ensure your error handler functions are registered with your Flask application using @app.errorhandler.

• List of Threats Mitigated:

  • Information Disclosure via Default Error Pages - Medium Severity: Default Flask error pages (especially when debug mode is off but custom handlers are missing) can still sometimes reveal internal application paths or framework details. Custom error pages allow you to control the information presented to users in error scenarios, preventing information leakage.

• Impact:

  • Information Disclosure Mitigation - Medium Impact: Custom error pages prevent the display of potentially sensitive framework or application details in error responses, reducing information leakage. Improves user experience by providing more user-friendly error messages.

• Currently Implemented:

  • Yes, Implemented for Common Errors: Custom error handlers and templates are implemented for common HTTP error codes like 404 (Page Not Found) and 500 (Internal Server Error) in the Flask application.

• Missing Implementation:

  • Coverage Review: Review the implemented error handlers to ensure they cover all relevant error codes for your Flask application (e.g., 400, 403, etc.) and that custom error pages are in place for each.
  • Error Page Content Review: Review the content of your custom error page templates to ensure they are generic and do not inadvertently expose any sensitive information about your Flask application or its environment.