mitigations.md

Mitigation Strategies Analysis for pixijs/pixi.js

Mitigation Strategy: Client-Side Resource Origin and Size Pre-Checks (Defense-in-Depth)

• Mitigation Strategy: Client-Side Resource Origin and Size Pre-Checks (Defense-in-Depth)

  • Description:

    1. URL Parsing: Before passing any resource URL to PixiJS (e.g., to PIXI.Loader, PIXI.Texture.from, etc.), use JavaScript's URL API to parse the URL and extract its origin.
    2. Origin Whitelist Check: Compare the extracted origin against a predefined, hardcoded whitelist of trusted origins within your client-side code.
    3. Reject Untrusted Origins: If the origin is not on the whitelist, do not pass the URL to PixiJS. Display an error message to the user or take other appropriate action. Do not attempt to load the resource.
    4. Size Estimation (Images): For image resources, attempt to estimate the image dimensions before loading it into PixiJS. This can be done using the Image object and its onload event:

       const img = new Image();
       img.onload = () => {
           if (img.width > MAX_WIDTH || img.height > MAX_HEIGHT) {
               // Reject the image
           } else {
               // Pass the image to PixiJS
               const texture = PIXI.Texture.from(img);
           }
       };
       img.src = imageUrl; // imageUrl must be from a trusted origin (checked earlier)

    5. Size Estimation (Other Resources): For other resource types (e.g., JSON data for sprite sheets), you might be able to perform some preliminary size checks based on the URL or initial response headers (e.g., Content-Length), but this is less reliable than server-side checks.

  • Threats Mitigated:

    • Cross-Site Scripting (XSS) via Textures/Resources: (Severity: High) - Reduces the risk (but doesn't eliminate it – server-side checks are essential) by preventing PixiJS from loading resources from untrusted origins.
    • Denial of Service (DoS) via Resource Exhaustion: (Severity: High) - Reduces the risk (but doesn't eliminate it) by preventing PixiJS from attempting to load excessively large resources.

  • Impact:

    • XSS: Provides a defense-in-depth layer against XSS, but server-side validation is still the primary defense.
    • DoS: Provides some protection against DoS, but server-side limits are crucial.

  • Currently Implemented: (Assume Not Implemented, as per previous response)

    • No client-side origin or size checks are currently performed before passing resources to PixiJS.

  • Missing Implementation:

    • All aspects of this strategy need to be implemented.

Mitigation Strategy: Safe PIXI.Text Input Handling

• Mitigation Strategy: Safe PIXI.Text Input Handling

  • Description:

    1. Identify PIXI.Text Usage: Locate all instances where PIXI.Text is used in your application.
    2. Source Analysis: Determine the source of the text being passed to PIXI.Text. Is it hardcoded, from a trusted internal source, or from user input?
    3. Sanitization (User Input): If the text originates from user input (or any untrusted source), always sanitize it before passing it to PIXI.Text. Use a dedicated, well-vetted HTML sanitization library (e.g., DOMPurify). Do not attempt to write your own sanitization logic.

       import DOMPurify from 'dompurify';
       
       // ...
       const userInput = getUserInput(); // Get the user's input
       const sanitizedText = DOMPurify.sanitize(userInput);
       const textObject = new PIXI.Text(sanitizedText, textStyle);

    4. Escape, don't concatenate: If you need to combine static text with dynamic (but sanitized) text, use template literals or separate PIXI.Text objects, rather than string concatenation, to avoid accidental injection vulnerabilities.

  • Threats Mitigated:

    • Cross-Site Scripting (XSS) via PIXI.Text: (Severity: High) - Prevents attackers from injecting malicious JavaScript code through user-provided text rendered with PIXI.Text.

  • Impact:

    • XSS: Eliminates the risk of XSS if user input is properly sanitized before being used with PIXI.Text.

  • Currently Implemented: (Assume Not Implemented, as per previous response)

    • No consistent sanitization is performed before using user input with PIXI.Text.

  • Missing Implementation:

    • All aspects of this strategy need to be implemented wherever PIXI.Text is used with potentially untrusted input.

Mitigation Strategy: Visibility and Z-Index Management Audit

• Mitigation Strategy: Visibility and Z-Index Management Audit

  • Description:

    1. Code Review: Conduct a thorough code review of all PixiJS-related code, focusing on the use of:
       • visible property
       • renderable property
       • zIndex property (or any custom z-ordering logic)
    2. Identify Potential Issues: Look for situations where:
       • Objects might be unintentionally hidden or revealed.
       • Incorrect z-ordering could lead to unexpected visual results or expose hidden elements.
       • Sensitive data might be inadvertently rendered (even if briefly) due to incorrect visibility management.
    3. Automated Checks (if possible): Explore the possibility of creating custom linting rules or static analysis tools to help identify potential visibility or z-index issues. This is more advanced but can be beneficial for larger projects.
    4. Testing: Create specific test cases to verify the correct visibility and rendering behavior of PixiJS objects, especially in edge cases or complex scenarios.

  • Threats Mitigated:

    • Data Leakage (Indirect): (Severity: Medium) - Reduces the risk of unintentionally exposing sensitive data through rendering artifacts or hidden elements.

  • Impact:

    • Data Leakage: Reduces the risk of unintentional data exposure, but the effectiveness depends on the thoroughness of the audit and testing.

  • Currently Implemented: (Assume Partially Implemented, as per previous response)

    • Basic visibility and z-index management are used, but a comprehensive audit is needed.

  • Missing Implementation:

    • A thorough, systematic audit of all visibility and z-index usage is required.
    • Automated checks are not implemented.
    • Specific test cases for visibility and rendering behavior are not comprehensive.

Mitigation Strategy: Avoid Deprecated PixiJS Features

• Mitigation Strategy: Avoid Deprecated PixiJS Features

  • Description:

    1. Documentation Review: Regularly review the official PixiJS documentation and changelogs for any deprecated features or APIs.
    2. Codebase Search: Search your codebase for any instances of deprecated features. Use your IDE's search functionality or a command-line tool like grep.
    3. Update Code: Replace any deprecated features with their recommended alternatives, as specified in the PixiJS documentation.
    4. Linter Configuration: Configure a linter (e.g., ESLint) with rules to detect the use of deprecated PixiJS features. This provides real-time feedback during development and helps prevent the introduction of new deprecated code. This may require custom ESLint rules specific to PixiJS.
    5. Testing: Thoroughly test the application after replacing deprecated features to ensure no regressions or unexpected behavior.

  • Threats Mitigated:

    • Vulnerabilities in Deprecated Features: (Severity: Variable, depends on the feature) - Reduces the risk of exploiting potential vulnerabilities that might exist in older, deprecated code.
    • Compatibility Issues: (Severity: Medium) - Ensures the application remains compatible with future versions of PixiJS.

  • Impact:

    • Vulnerabilities: Reduces the risk of vulnerabilities associated with deprecated features.
    • Compatibility: Improves long-term maintainability and compatibility.

  • Currently Implemented: (Assume Partially Implemented, as per previous response)

    • Developers are generally aware of the need to avoid deprecated features.

  • Missing Implementation:

    • No formal process for regularly reviewing PixiJS documentation for deprecations.
    • No linter rules are configured to specifically detect deprecated PixiJS features.
    • No specific testing procedures are in place to address deprecated feature replacements.

Mitigation Strategy: Web Worker Usage for Intensive Tasks

• Mitigation Strategy: Web Worker Usage for Intensive Tasks

  • Description:

    1. Identify Intensive Operations: Profile your PixiJS application to identify computationally intensive operations. This might include:
       • Complex filter calculations.
       • Large sprite sheet animations.
       • Frequent updates to a large number of objects.
       • Custom shader computations.
    2. Create a Web Worker: Create a separate JavaScript file (the Web Worker) to handle the intensive operations.
    3. Message Passing: Use the postMessage API to communicate between the main thread and the Web Worker. Send the necessary data to the worker, and receive the results back.
    4. PixiJS in the Worker (Careful Consideration): It's possible to use PixiJS within a Web Worker, but it requires careful setup and has limitations. You cannot directly manipulate the DOM from a Web Worker, so you'll need to use an OffscreenCanvas and transfer its control to the worker. This is a more advanced technique.
    5. Alternative: Data Processing in Worker: A simpler approach is often to perform the data processing in the Web Worker and then send the processed data back to the main thread, where PixiJS renders it. For example, calculate positions, colors, or other properties in the worker, and then update the PixiJS objects on the main thread.

  • Threats Mitigated:

    • Denial of Service (DoS) via Resource Exhaustion (Indirectly): (Severity: High) - While it doesn't prevent DoS, it significantly improves the user experience during an attack by keeping the main thread responsive.

  • Impact:

    • DoS: Improves application resilience to DoS attacks by preventing the UI from freezing.
    • Performance: Improves overall application performance and responsiveness.

  • Currently Implemented: (Assume Not Implemented, as per previous response)

    • Web Workers are not currently used for any PixiJS-related operations.

  • Missing Implementation:

    • All aspects of this strategy need to be implemented for identified computationally intensive tasks.