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Mitigation Strategies Analysis for airbnb/lottie-web

Mitigation Strategy: Input Validation of Lottie JSON Structure

Description:

  1. Select a JSON Schema validation library compatible with your project's programming language.
  2. Define a JSON Schema that accurately represents the expected structure of valid Lottie JSON files, based on the official Lottie specification and the features your application uses.
  3. Integrate the JSON Schema validator into your application's Lottie file processing workflow, validating files before they are parsed by lottie-web.
    • For user-uploaded files: Validate on the server-side immediately after upload.
    • For bundled files: Validate during the build process.
  4. Configure the validator to strictly enforce the schema and reject invalid files.
  5. Implement error handling for validation failures, logging errors and providing informative messages if needed.

Threats Mitigated:

  • Malformed Lottie JSON Exploitation (High Severity): Prevents potential vulnerabilities in lottie-web's JSON parsing logic by ensuring only structurally valid JSON is processed. Malformed JSON could cause lottie-web to crash, behave unexpectedly, or potentially expose vulnerabilities if the parsing process is flawed.
  • lottie-web Rendering Errors (Medium Severity): Reduces rendering errors and unexpected behavior within lottie-web that can arise from attempting to render invalid or corrupted Lottie files. This leads to a more stable and predictable animation rendering process within the library.
  • Resource Exhaustion during lottie-web Parsing (Medium Severity): Mitigates resource exhaustion by preventing lottie-web from attempting to parse excessively complex or deeply nested JSON structures that deviate from the expected Lottie format, which could strain lottie-web's parsing engine.

Impact:

  • Malformed Lottie JSON Exploitation: Significantly reduces the risk by ensuring lottie-web receives valid input, minimizing potential parsing-related vulnerabilities within the library.
  • lottie-web Rendering Errors: Moderately reduces the risk of rendering issues caused by invalid input, leading to more reliable lottie-web animation display.
  • Resource Exhaustion during lottie-web Parsing: Minimally to Moderately reduces the risk of parsing-related resource exhaustion within lottie-web.

Currently Implemented:

  • Currently implemented on the server-side for user-uploaded Lottie files in the /api/lottie/upload endpoint using a custom JSON schema and the ajv library in Node.js.

Missing Implementation:

  • Client-side validation is not yet implemented. Lottie files bundled with the application during build are not currently validated. Validation should be added to the build pipeline to ensure application assets are valid before lottie-web processes them.

Mitigation Strategy: Restrict Allowed Lottie Features and Properties

Description:

  1. Analyze the Lottie specification and identify features and properties that are not essential for your application's use of lottie-web or that could pose risks when processed by lottie-web. Focus on features like expressions, specific renderers, or dynamic properties.
  2. Develop a sanitization process to remove or modify these restricted features from the Lottie JSON after validation but before passing it to lottie-web for rendering.
    • Implement a function to traverse the JSON and remove or modify specific keys/values.
  3. Test the sanitization process to ensure it doesn't break intended animation functionality within lottie-web while removing targeted features.
  4. Document restricted features and the rationale for their restriction related to lottie-web usage.

Threats Mitigated:

  • Expression-Based Vulnerabilities in lottie-web (Medium to High Severity - if expressions are used): If lottie-web's expression engine has vulnerabilities, or if expressions can be crafted to cause unintended behavior within lottie-web's rendering process, restricting expressions eliminates this attack vector.
  • Renderer-Specific Vulnerabilities in lottie-web (Low to Medium Severity): If vulnerabilities exist in specific renderers within lottie-web, limiting the allowed renderers reduces the attack surface within the library.
  • Performance Degradation within lottie-web due to Complex Features (Medium Severity): Certain Lottie features can be computationally expensive for lottie-web to render. Restricting these can improve lottie-web's rendering performance and prevent potential DoS by complex animations processed by lottie-web.

Impact:

  • Expression-Based Vulnerabilities in lottie-web: Significantly reduces the risk if expressions are a concern, eliminating a potential vulnerability point within lottie-web.
  • Renderer-Specific Vulnerabilities in lottie-web: Minimally reduces the risk, unless specific renderer vulnerabilities in lottie-web are identified. Reduces attack surface within lottie-web.
  • Performance Degradation within lottie-web due to Complex Features: Moderately reduces the risk of performance issues caused by specific features straining lottie-web's rendering capabilities.

Currently Implemented:

  • Partially implemented. Expressions are not explicitly disabled in lottie-web configuration, but we are not actively using Lottie animations that rely on expressions.

Missing Implementation:

  • Explicitly disable expressions in lottie-web configuration if possible. Implement a JSON sanitization function to actively remove expression-related properties from Lottie JSON before rendering by lottie-web. Further analysis is needed to identify other potentially risky features for lottie-web to process.

Mitigation Strategy: Enforce File Size Limits for Lottie Files

Description:

  1. Determine a maximum file size for Lottie JSON files based on application needs and expected animation complexity, considering lottie-web's performance and resource usage.
  2. Implement file size checks:
    • Client-side (for user uploads): Provide feedback if files exceed the limit before upload.
    • Server-side (for user uploads): Enforce limits before processing files with lottie-web.
    • During build (for bundled files): Optionally check size to ensure reasonable limits for lottie-web rendering.
  3. Configure web server/CDN to enforce file size limits for serving Lottie files, if applicable, to prevent serving excessively large files to lottie-web.
  4. Communicate file size limits to users uploading Lottie files.

Threats Mitigated:

  • Denial of Service (DoS) through Large Lottie Files impacting lottie-web (High Severity): Prevents attackers from uploading or providing excessively large Lottie files that could consume excessive resources when lottie-web attempts to parse and render them, potentially leading to denial of service by overloading lottie-web or the client.
  • Client-Side Performance Issues with lottie-web (Medium Severity): Reduces the risk of client-side performance problems caused by lottie-web attempting to render very large and complex animations, which can lead to browser crashes or unresponsive behavior due to lottie-web's resource consumption.

Impact:

  • Denial of Service (DoS) through Large Lottie Files impacting lottie-web: Significantly reduces the risk by preventing lottie-web from processing excessively large files that could strain its resources.
  • Client-Side Performance Issues with lottie-web: Moderately reduces the risk of performance problems caused by lottie-web rendering overly large animations.

Currently Implemented:

  • Server-side file size limit of 2MB is implemented for Lottie file uploads in the /api/lottie/upload endpoint. Client-side file size validation with a warning message is also implemented before upload submission.

Missing Implementation:

  • File size limits are not enforced for Lottie files bundled with the application during the build process. Consider adding a build-time check to warn or fail the build if bundled Lottie files exceed a defined size threshold, ensuring reasonable file sizes for lottie-web to handle.

Mitigation Strategy: Regularly Update lottie-web

Description:

  1. Establish a process for monitoring new releases and security updates for lottie-web.
  2. Promptly update lottie-web to the latest stable version, especially security patches, to benefit from bug fixes and security improvements within the library itself.
  3. Thoroughly test your application after each lottie-web update to ensure compatibility and no regressions in lottie-web's rendering or functionality.
  4. Document the lottie-web version used and track update history.

Threats Mitigated:

  • Known Vulnerabilities in lottie-web (High Severity): Mitigates the risk of exploitation of known security vulnerabilities within lottie-web itself. Updates are released to fix bugs and security issues in lottie-web, and using outdated versions leaves your application vulnerable to these known flaws in the library.

Impact:

  • Known Vulnerabilities in lottie-web: Significantly reduces the risk by ensuring you are running the most secure version of lottie-web, benefiting from fixes and security patches directly within the library.

Currently Implemented:

  • We are currently using lottie-web version 5.9.6. We have a manual process for checking for updates.

Missing Implementation:

  • Implement an automated dependency update monitoring system to automatically detect and notify about new lottie-web releases and security vulnerabilities. Integrate this into our CI/CD pipeline to streamline the lottie-web update process.

Mitigation Strategy: Dependency Scanning

Description:

  1. Integrate a dependency scanning tool into your development pipeline that supports scanning JavaScript dependencies.
  2. Configure the tool to regularly scan your project's dependency files to identify known vulnerabilities in lottie-web and its dependencies.
  3. Set up automated alerts for vulnerability detection.
  4. Establish a process for reviewing and remediating identified vulnerabilities in lottie-web or its dependencies, prioritizing based on severity and impact.

Threats Mitigated:

  • Known Vulnerabilities in lottie-web and its Dependencies (High Severity): Proactively identifies known security vulnerabilities within lottie-web and libraries it relies on. This allows for timely remediation of vulnerabilities in the lottie-web dependency chain before they can be exploited.
  • Supply Chain Attacks targeting lottie-web dependencies (Medium Severity): Dependency scanning can help detect compromised dependencies of lottie-web if they are added to vulnerability databases, offering some protection against supply chain issues affecting lottie-web indirectly.

Impact:

  • Known Vulnerabilities in lottie-web and its Dependencies: Significantly reduces the risk by providing early detection of vulnerabilities in the lottie-web ecosystem, enabling proactive patching and reducing the vulnerability window.
  • Supply Chain Attacks targeting lottie-web dependencies: Minimally to Moderately reduces the risk. Detection depends on vulnerability databases being updated promptly after a supply chain compromise affecting lottie-web's dependencies.

Currently Implemented:

  • We are using npm audit as part of our development workflow to check for vulnerabilities before deployments, including lottie-web and its dependencies.

Missing Implementation:

  • Integrate npm audit (or a more comprehensive tool) into our CI/CD pipeline to automatically run on every build and fail builds if high-severity vulnerabilities are detected in lottie-web or its dependencies. Set up automated notifications for vulnerability alerts related to lottie-web.

Mitigation Strategy: Subresource Integrity (SRI)

Description:

  1. If loading lottie-web from a CDN, generate SRI hashes for the specific lottie-web files used.
  2. When including the <script> tag to load lottie-web from the CDN, add the integrity attribute with the SRI hash and crossorigin="anonymous".
  3. The browser will verify the fetched lottie-web file's hash against the SRI hash. If they don't match, the script will not execute, preventing the use of potentially compromised lottie-web files from the CDN.

Threats Mitigated:

  • CDN Compromise/Supply Chain Attacks targeting lottie-web (Medium to High Severity): Mitigates the risk of a CDN being compromised and malicious code being injected into the lottie-web files served from the CDN. SRI ensures that the browser only executes the expected, untampered version of the lottie-web library.

Impact:

  • CDN Compromise/Supply Chain Attacks targeting lottie-web: Significantly reduces the risk of using compromised CDN resources for lottie-web. Provides a strong guarantee of file integrity when loading lottie-web from CDNs.

Currently Implemented:

  • We are loading lottie-web from a CDN (jsDelivr). SRI is not currently implemented for the <script> tag loading lottie-web.

Missing Implementation:

  • Implement SRI for the <script> tag loading lottie-web from the CDN. Generate SRI hashes for the specific lottie-web version we are using and add the integrity and crossorigin attributes to the <script> tag in our HTML templates to ensure the integrity of the lottie-web library.

Mitigation Strategy: Animation Complexity Limits

Description:

  1. Analyze the typical complexity of Lottie animations used in your application in relation to lottie-web's rendering performance. Define metrics for complexity relevant to lottie-web, such as layers, shapes, keyframes, or effects.
  2. Establish guidelines or limits for animation complexity based on your application's performance requirements and target devices, considering lottie-web's capabilities.
  3. If users upload/create Lottie animations, implement mechanisms to enforce complexity limits relevant to lottie-web:
    • Analysis tools: Develop/use tools to analyze Lottie JSON and assess complexity for lottie-web rendering.
    • Rejection/simplification: Reject animations exceeding limits or simplify them for better lottie-web performance.
  4. Educate designers about complexity limits and best practices for creating performant Lottie animations for lottie-web.

Threats Mitigated:

  • Client-Side Performance Degradation due to lottie-web Rendering Complexity (Medium Severity): Prevents or reduces client-side performance issues (lag, jank, crashes) caused by lottie-web rendering overly complex Lottie animations, especially on lower-powered devices where lottie-web's performance might be more constrained.
  • Resource Exhaustion (Client-Side DoS) due to lottie-web Rendering Load (Medium Severity): Mitigates client-side denial-of-service where excessively complex animations could consume so many resources during lottie-web rendering that the browser becomes unresponsive or crashes specifically due to lottie-web's resource demands.

Impact:

  • Client-Side Performance Degradation due to lottie-web Rendering Complexity: Moderately reduces the risk by limiting animation complexity, leading to smoother lottie-web rendering and better user experience.
  • Resource Exhaustion (Client-Side DoS) due to lottie-web Rendering Load: Moderately reduces the risk of client-side DoS by preventing lottie-web from rendering animations likely to overwhelm client resources.

Currently Implemented:

  • No explicit animation complexity limits are currently implemented for lottie-web rendering.

Missing Implementation:

  • Implement analysis tools to assess Lottie animation complexity relevant to lottie-web's performance. Define specific complexity metrics and thresholds. Consider server-side checks to reject/simplify overly complex user-uploaded animations for lottie-web. Document animation complexity guidelines for designers to optimize for lottie-web.

Mitigation Strategy: Resource Quotas for Animation Rendering

Description:

  1. Implement resource quotas for animation rendering, especially when multiple animations might be rendered concurrently by lottie-web or when users can trigger frequent animation rendering.
  2. Limit:
    • Concurrent animations: Restrict the number of Lottie animations lottie-web can render simultaneously.
    • Total rendering time: Limit total time spent rendering animations by lottie-web within a period.
    • CPU/Memory usage: (More complex) Monitor CPU/memory usage during lottie-web rendering and throttle/stop if thresholds are exceeded.
  3. Prioritize animation rendering if needed, ensuring critical animations are rendered by lottie-web while less important ones are delayed/skipped under resource constraints.

Threats Mitigated:

  • Client-Side Performance Degradation due to Concurrent lottie-web Rendering (Medium Severity): Reduces client-side performance issues caused by excessive concurrent animation rendering by lottie-web.
  • Resource Exhaustion (Client-Side DoS) due to Overloading lottie-web (Medium Severity): Mitigates client-side denial-of-service caused by overloading the browser with too many animations for lottie-web to render at once, leading to resource exhaustion specifically related to lottie-web's processing.

Impact:

  • Client-Side Performance Degradation due to Concurrent lottie-web Rendering: Moderately reduces the risk by preventing resource contention from excessive lottie-web animation rendering.
  • Resource Exhaustion (Client-Side DoS) due to Overloading lottie-web: Moderately reduces the risk of client-side DoS by limiting the overall resource demand from animations rendered by lottie-web.

Currently Implemented:

  • No explicit resource quotas for lottie-web animation rendering are currently implemented.

Missing Implementation:

  • Implement limits on the number of concurrent Lottie animations that lottie-web can render. Explore options for limiting total rendering time or monitoring resource usage during lottie-web animation rendering.

Mitigation Strategy: Lazy Loading and On-Demand Rendering

Description:

  1. Implement lazy loading for Lottie animations, especially for multiple animations or those not immediately visible, to optimize lottie-web usage.
  2. Use Intersection Observer API to detect when Lottie animation containers become visible.
  3. Only initialize and start rendering Lottie animations with lottie-web when containers are in the viewport or needed based on user interaction.
  4. For non-continuous animations, render them with lottie-web only on demand (e.g., hover, click).

Threats Mitigated:

  • Initial Page Load Performance Degradation due to lottie-web Initialization (Medium Severity): Reduces initial page load time by deferring loading and rendering of Lottie animations by lottie-web that are not immediately needed.
  • Unnecessary Resource Consumption (Client-Side) by lottie-web (Low to Medium Severity): Prevents unnecessary CPU and memory usage by avoiding rendering animations with lottie-web that are not visible or actively used.

Impact:

  • Initial Page Load Performance Degradation due to lottie-web Initialization: Moderately reduces the risk by improving initial page load speed and perceived performance by deferring lottie-web usage.
  • Unnecessary Resource Consumption (Client-Side) by lottie-web: Minimally to Moderately reduces resource consumption, especially on pages with many animations, leading to better battery life and smoother performance by optimizing lottie-web's activity.

Currently Implemented:

  • Lazy loading is not currently implemented for Lottie animations rendered by lottie-web. All animations are initialized and start rendering on page load.

Missing Implementation:

  • Implement lazy loading for Lottie animations using Intersection Observer API. Modify animation initialization logic to start lottie-web rendering only when the animation container is in the viewport, optimizing lottie-web's resource usage.