mitigations.md

Mitigation Strategies Analysis for ryanb/cancan

Mitigation Strategy: Comprehensive Test Suite for Ability Definitions

• Description:

  1. Create a dedicated test file: Create a file specifically for testing abilities (e.g., spec/models/ability_spec.rb in RSpec).
  2. Define test contexts: Structure tests using contexts for different user roles (e.g., "admin," "user," "guest").
  3. Test positive cases: For each role and resource, write tests that assert the user can perform actions they are allowed to. Use expect(ability).to be_able_to(:action, resource).
  4. Test negative cases: For each role and resource, write tests that assert the user cannot perform actions they are not allowed to. Use expect(ability).not_to be_able_to(:action, resource).
  5. Test edge cases: Include tests for boundary conditions (e.g., empty resources, nil values, invalid IDs), and unusual scenarios.
  6. Test different user attributes: If abilities depend on user attributes (e.g., project.user_id == user.id), test with different attribute values.
  7. Integrate with CI/CD: Run these tests automatically as part of your continuous integration/continuous deployment pipeline.
  8. Regularly update tests: As new features are added or authorization rules change, update the tests accordingly.

• Threats Mitigated:

  • Incorrect Ability Definitions (Logic Errors): (Severity: High) - Incorrect can and cannot rules granting unintended access. This is the core threat CanCan addresses, and testing is the primary defense.
  • Overly Broad Permissions: (Severity: High) - Using :manage, :all too liberally. Testing helps reveal when this is happening.
  • Typos in Ability Definitions: (Severity: Medium) - Misspelled model or attribute names. Tests using be_able_to will fail if the model or attribute doesn't exist.
  • Confusing can and cannot: (Severity: Medium) - Incorrectly using cannot instead of can with a negated condition. Positive and negative tests expose this.

• Impact:

  • Incorrect Ability Definitions: Risk reduced significantly (80-90%).
  • Overly Broad Permissions: Risk reduced moderately (50-60%).
  • Typos: Risk reduced significantly (90%).
  • Confusing can and cannot: Risk reduced significantly (80-90%).

• Currently Implemented:

  • spec/models/ability_spec.rb exists and contains basic tests for admin and user roles.
  • Tests are run as part of the CI/CD pipeline.

• Missing Implementation:

  • Tests for guest users are incomplete.
  • Edge case testing is limited.
  • Tests for specific user attributes (beyond role) are missing.
  • Negative tests are not comprehensive for all actions.

Mitigation Strategy: Enforce Authorization Checks in Controllers (using CanCan methods)

• Description:

  1. Use load_and_authorize_resource: This is a CanCan-specific method. Use it as the default in controllers to automatically load the resource and authorize it based on the Ability class.
  2. Handle CanCan::AccessDenied: Implement a global exception handler to catch this CanCan-specific exception. This ensures consistent handling of authorization failures.
  3. Manual authorize! (when necessary): If load_and_authorize_resource is not suitable, use the CanCan-specific authorize! :action, @resource method.
  4. Code Review Checklist: Include "authorization checks present (using CanCan methods)" as a mandatory item.

• Threats Mitigated:

  • Bypassing CanCan Checks: (Severity: High) - Developers forgetting to use CanCan's authorization methods (authorize! or load_and_authorize_resource).

• Impact:

  • Bypassing CanCan Checks: Risk reduced significantly (70-80%).

• Currently Implemented:

  • load_and_authorize_resource is used in most controllers.
  • CanCan::AccessDenied is handled globally.

• Missing Implementation:

  • Some older controllers still use manual authorize! calls (need to be refactored to use load_and_authorize_resource where possible).
  • Code review checklist item is not consistently enforced.

Mitigation Strategy: Conditional Rendering in Views (using can?)

• Description:

  1. Use can? for UI elements: This is a CanCan-specific method. Wrap UI elements with can? :action, @resource checks. This prevents rendering elements the user cannot access.
  2. Avoid disabling elements: Completely remove unauthorized elements; don't just disable them.
  3. Test view rendering: Verify UI elements are correctly rendered (or not) based on user abilities defined in CanCan.

• Threats Mitigated:

  • Ability Leakage (Information Disclosure): (Severity: Medium) - Exposing information about a user's abilities through the UI (by showing elements they can't use).

• Impact:

  • Ability Leakage: Risk reduced significantly (80-90%).

• Currently Implemented:

  • can? is used in most views.

• Missing Implementation:

  • Some older views may still disable elements.
  • View tests specifically checking for can? usage are limited.

Mitigation Strategy: Judicious Use of accessible_by (and Analysis)

• Description:

  1. Prefer authorize! and can?: For simple checks, use these CanCan-specific methods.
  2. Use accessible_by for scoping queries: Only use this CanCan-specific method when you need to retrieve a set of records based on abilities defined in the Ability class.
  3. Analyze generated SQL: Examine the SQL queries generated by accessible_by to ensure efficiency and prevent data leakage. This is crucial because accessible_by directly interacts with the database based on CanCan's rules.
  4. Consider alternatives: If accessible_by leads to complex queries, consider fetching more data and filtering in Ruby (using can? on individual objects, if needed).
  5. Document usage: If using accessible_by, clearly document the reason and the expected behavior.

• Threats Mitigated:

  • Performance Issues with accessible_by: (Severity: Medium) - Inefficient queries.
  • Data Leakage with accessible_by: (Severity: Medium) - Exposing unintended data. This is directly related to how CanCan translates abilities into database queries.

• Impact:

  • Performance Issues: Risk reduced moderately (50-60%).
  • Data Leakage: Risk reduced moderately (50-60%).

• Currently Implemented:

  • accessible_by is used in a few places.

• Missing Implementation:

  • No formal guidelines for when to use accessible_by.
  • Generated SQL is not routinely analyzed.
  • Documentation is limited.

Mitigation Strategy: Code Reviews Focused on CanCan Usage

• Description:

  1. Dedicated Reviewer: Assign a developer familiar with CanCan to review authorization logic.
  2. Checklist: Include items specifically related to CanCan:
     • Presence of authorize! or load_and_authorize_resource.
     • Correctness of can and cannot rules.
     • Use of can? in views.
     • Appropriate use of accessible_by.
     • No bypassing of CanCan's checks.
  3. Focus on Logic: Understand the intended access control model and how CanCan is used to implement it.
  4. Scenario Walkthrough: Walk through user scenarios to ensure CanCan rules behave as expected.

• Threats Mitigated:

  • Incorrect Ability Definitions (Logic Errors): (Severity: High)
  • Bypassing CanCan Checks: (Severity: High)
  • Ability Leakage: (Severity: Medium)
  • Overly Broad Permissions: (Severity: High)
  • All other CanCan-related threats: (Severity: Medium to High)

• Impact:

  • All Threats: Risk reduced significantly (60-80%).

• Currently Implemented:

  • Code reviews are mandatory.

• Missing Implementation:

  • No dedicated reviewer for CanCan logic.
  • No specific checklist items for CanCan.
  • Scenario walkthroughs are not consistent.

Mitigation Strategy: Regular Security Audits of the Ability Class

• Description:

  1. Schedule: Conduct regular audits of the Ability class (the core of CanCan).
  2. Independent Reviewer: Ideally, have someone not directly involved in development perform the audit.
  3. Focus on Changes: Review changes made to the Ability class since the last audit.
  4. Re-evaluate Existing Rules: Re-evaluate all existing CanCan rules.
  5. Document Findings: Document any vulnerabilities or areas for improvement.
  6. Prioritize Remediation: Address identified issues promptly.

• Threats Mitigated:

  • Incorrect Ability Definitions (Logic Errors): (Severity: High)
  • Overly Broad Permissions: (Severity: High)
  • All other CanCan-related threats: (Severity: Medium to High)

• Impact:

  • All Threats: Risk reduced moderately (40-60%).

• Currently Implemented:

  • None.

• Missing Implementation:

  • No formal process for regular audits of the Ability class.