threat-modeling.md

Threat Model Analysis for pixijs/pixi.js

Threat: Denial of Service (DoS) via Resource Exhaustion

• Threat: Denial of Service (DoS) via Resource Exhaustion

  • Description: An attacker crafts malicious input or manipulates existing content to cause excessive GPU/CPU usage. This could involve:

    • Creating a huge number of Sprite objects.
    • Using extremely large textures.
    • Applying complex, computationally expensive custom Filter instances.
    • Triggering frequent and unnecessary re-renders of the entire scene graph.
    • Exploiting inefficiencies in specific Renderer methods.
    • Abusing particle systems (pixi/particle-emitter) with excessive particle counts and lifetimes.

  • Impact: The user's browser becomes unresponsive, potentially crashing the tab or even the entire browser. The application becomes unusable. In extreme cases, it could lead to system instability.

  • PixiJS Component Affected:

    • Renderer (and its subclasses like WebGLRenderer and CanvasRenderer)
    • Sprite
    • Texture
    • Filter
    • Container (and its subclasses, as excessive nesting can impact performance)
    • Graphics (if used to draw extremely complex shapes repeatedly)
    • pixi/particle-emitter (if installed and used)

  • Risk Severity: High

  • Mitigation Strategies:

    • Limit Sprite Count: Impose a reasonable maximum on the number of sprites that can be displayed simultaneously.
    • Texture Size Restrictions: Validate and limit the dimensions and file size of textures loaded, especially from user-provided sources.
    • Filter Complexity Control: Restrict the use of custom filters, or carefully review and profile their performance impact. Limit the number of filters applied to a single object.
    • Rate Limiting: Implement rate limiting on user actions that trigger rendering updates.
    • Scene Graph Optimization: Use techniques like object pooling, culling (removing objects outside the viewport), and minimizing the depth of the scene graph.
    • Resource Monitoring: Monitor GPU/CPU usage and frame rate. If thresholds are exceeded, throttle rendering or take other corrective actions.
    • Input Validation: Sanitize any user input that affects rendering parameters.
    • Particle System Limits: If using pixi/particle-emitter, strictly limit the number of particles, emission rate, and particle lifetime.

Threat: Browser/System Instability via WebGL Exploits

• Threat: Browser/System Instability via WebGL Exploits

  • Description: An attacker leverages vulnerabilities in the browser's WebGL implementation (which PixiJS uses) by crafting malicious PixiJS content. This is not a PixiJS bug, but PixiJS is the vector. The attacker might:

    • Provide a specially crafted shader (Filter) that triggers a known WebGL vulnerability.
    • Use a combination of PixiJS features in a way that exposes a browser bug.

  • Impact: Browser crash, potential system instability, or in rare cases, arbitrary code execution (though this is more likely to be a browser vulnerability than a PixiJS one).

  • PixiJS Component Affected:

    • Renderer (specifically WebGLRenderer)
    • Filter (custom shaders are the most likely vector)
    • Any component that interacts with WebGL (indirectly, most PixiJS components)

  • Risk Severity: Critical (if a WebGL exploit exists), but the likelihood depends on the browser's vulnerability, not PixiJS itself.

  • Mitigation Strategies:

    • User Education: Encourage users to keep their browsers up-to-date.
    • Stay Updated with PixiJS: Use the latest stable version of PixiJS, as it may include workarounds for known browser issues.
    • Avoid Experimental WebGL Features: Stick to well-tested WebGL features.
    • Shader Validation (Difficult): Ideally, validate custom shaders, but this is extremely complex. Consider using a shader linter or restricting shader capabilities.
    • Fallback to Canvas: If WebGL is unavailable or deemed risky, provide a fallback rendering mechanism (e.g., using CanvasRenderer).

Threat: Visual Spoofing/Manipulation

• Threat: Visual Spoofing/Manipulation

  • Description: An attacker manipulates the visual output of the application, potentially to mislead the user. This is most relevant if user input influences the rendering. The attacker might:

    • Inject malicious code that alters the properties of Sprite, Text, or Graphics objects.
    • Modify texture data to display incorrect images.
    • Change the position, scale, or rotation of objects to obscure or misrepresent information.

  • Impact: Users are presented with false or misleading information, potentially leading to phishing, data breaches, or other security compromises. The application's integrity is compromised.

  • PixiJS Component Affected:

    • Sprite
    • Text
    • Graphics
    • Texture
    • Container (and its subclasses, for positioning and visibility manipulation)
    • Any component whose visual properties can be influenced by user input.

  • Risk Severity: High (depending on the application's purpose and the sensitivity of the displayed information)

  • Mitigation Strategies:

    • Strict Input Validation: Thoroughly validate and sanitize all user input that affects the visual output. This includes text, colors, positions, sizes, and any other parameters.
    • Data Binding (Careful): If using data binding to connect user input to PixiJS objects, ensure that the binding mechanism itself is secure and cannot be exploited.
    • Output Encoding (Context-Specific): While not directly applicable to PixiJS rendering, ensure that any text displayed using PixiJS's Text object is properly encoded to prevent XSS vulnerabilities if that text comes from user input. This is a general web security principle, but relevant here.
    • Texture Integrity (If Applicable): If loading textures from external sources, consider using integrity checks (though this is less common for images than for scripts).
    • Separation of Concerns: Keep the core rendering logic separate from user-controlled data as much as possible.