attack-surface.md

Attack Surface Analysis for varvet/pundit

Attack Surface: 1. Incorrectly Implemented Policy Methods (Logic Errors)

• Description: Flaws in the boolean logic, attribute comparisons, or edge case handling within Pundit policy methods, leading to incorrect authorization decisions. This is the core area where Pundit-specific vulnerabilities arise.
  • How Pundit Contributes: Pundit provides the framework, but the developer defines the authorization rules within the policy methods. Errors here are directly attributable to how Pundit is used.
  • Example:

    # Policy for deleting a Comment
    class CommentPolicy < ApplicationPolicy
      def destroy?
        user.admin? || user.id == @record.post.user_id # Incorrect! Should be @record.user_id
      end
    end

    This allows any user who owns the post to delete any comment on that post, even if they didn't write the comment.
  • Impact: Unauthorized access to data (read, create, update, delete), potentially leading to data breaches, data corruption, or privilege escalation. The impact is directly tied to the flawed logic.
  • Risk Severity: Critical to High (depending on the specific logic flaw and the sensitivity of the data/actions).
  • Mitigation Strategies:
    • Rigorous Code Reviews: Multiple reviewers, focusing intensely on the boolean logic, attribute comparisons, and all potential edge cases within each policy method.
    • Comprehensive Unit Testing: Write unit tests for every policy method, covering all possible user roles, object states, and edge cases. Use pundit-matchers to simplify and standardize testing. Consider property-based testing.
    • Consistent Naming and Structure: Adopt a clear and consistent naming convention for policy methods and attributes to minimize confusion and errors.
    • Static Analysis (where applicable): Explore linters or static analysis tools that might detect some logic errors or inconsistencies in policy code (though this is less reliable than thorough testing and review).

Attack Surface: 2. Missing authorize Call or Incorrect Policy Method Invocation

• Description: Forgetting to call authorize in a controller action, or calling it with the wrong arguments (e.g., missing the policy method name or using incorrect syntax), leading to completely bypassed authorization checks.
  • How Pundit Contributes: Pundit requires explicit authorize calls to enforce authorization. Missing or incorrect calls directly circumvent Pundit's intended functionality.
  • Example:

    # Controller action
    def destroy
      @post = Post.find(params[:id])
      # authorize @post, :destroy?  <-- MISSING!  Authorization is bypassed.
      @post.destroy
      redirect_to posts_path
    end

    Or:

    authorize @post  # Incorrect - should be authorize @post, :destroy?

  • Impact: Completely unauthorized access to actions and data. This is a critical bypass of the authorization system.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Mandatory after_action :verify_authorized: Use this callback in ApplicationController (or relevant base controllers) to force a check that authorize has been called in every action. This is a crucial preventative measure.
    • Code Reviews: Carefully review all controller actions to ensure that authorize is called correctly, with the appropriate policy method.
    • Automated Testing: Write integration tests that specifically check for unauthorized access when authorize is missing or incorrect. These tests should attempt to access actions without proper authorization.
    • Linters/Static Analysis: Use tools that can reliably detect missing or incorrect authorize calls.

Attack Surface: 3. Incorrect Scope Resolution (Information Disclosure)

• Description: Errors in Policy::Scope classes that result in users seeing more data than they should, leading to information disclosure. This is a direct misuse of Pundit's scoping mechanism.
  • How Pundit Contributes: Pundit's Policy::Scope classes are specifically designed to filter collections of records based on user authorization. Incorrect filtering logic within these classes is a direct Pundit-related vulnerability.
  • Example:

    # Policy scope for Posts
    class PostPolicy < ApplicationPolicy
      class Scope < Scope
        def resolve
          scope.all # Incorrect!  Returns ALL posts, regardless of user permissions.
        end
      end
    end

  • Impact: Information disclosure, potentially revealing sensitive data to unauthorized users. The severity depends on the data exposed.
  • Risk Severity: High
  • Mitigation Strategies:
    • Thorough Testing: Write specific tests for each Policy::Scope class, verifying that only the expected records are returned for different user roles and contexts. This is crucial.
    • Code Reviews: Carefully review the resolve method in each scope class, focusing intensely on the filtering logic and ensuring it correctly restricts access based on user permissions and relationships.
    • Database Query Analysis: Examine the generated SQL queries (e.g., using database logging or profiling tools) to ensure they are efficient and, more importantly, do not inadvertently expose data.

Attack Surface: 4. Overly Permissive Default Policy

• Description: If a specific policy method is not defined, Pundit may fall back to a default policy (e.g., ApplicationPolicy). If this default policy is too permissive (e.g., allows access by default), it can lead to unauthorized access.
  • How Pundit Contributes: Pundit's policy resolution mechanism can fall back to default policies if specific methods are not found. This fallback behavior, if misconfigured, is a direct source of vulnerability.
  • Example:

    # ApplicationPolicy (default)
    class ApplicationPolicy
      def create?
        true # Allows access by default - TOO PERMISSIVE!
      end
    end

    If a specific policy (e.g., ProductPolicy) does not define a create? method, this overly permissive default would be used, allowing any user to create products.
  • Impact: Unauthorized access to actions and data, particularly if developers forget to define specific policy methods.
  • Risk Severity: High
  • Mitigation Strategies:
    • Restrictive Default Policies: Ensure that default policies (e.g., ApplicationPolicy) are as restrictive as possible, ideally denying access by default for all actions. This is a crucial preventative measure.

      class ApplicationPolicy
        def index?; false; end
        def show?; false; end
        def create?; false; end
        def update?; false; end
        def destroy?; false; end
        # ... deny access by default for all other actions
      end

    • Explicit Policy Methods: Define all required policy methods explicitly in each policy class, rather than relying on defaults. This eliminates the risk of the fallback mechanism.