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Threat Model Analysis for airbnb/lottie-android

Threat: Malicious JSON File - Code Execution (RCE)

  • Description: An attacker crafts a Lottie JSON file that exploits a vulnerability in lottie-android's JSON parsing or rendering engine (e.g., a buffer overflow in native code, a deserialization vulnerability in Java/Kotlin) to execute arbitrary code on the device. This leverages a flaw within the library.
  • Impact: Complete device compromise. The attacker could steal data, install malware, or take full control of the device.
  • Affected Component:
    • JsonCompositionLoader: The JSON parsing component is the most likely entry point.
    • Native rendering engine (if used by lottie-android). Vulnerabilities in C/C++ code are often more exploitable.
    • Any component handling data derived from the JSON (e.g., if custom properties are used to influence application logic within the library's context).
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Developer (Library-Level - Airbnb's Responsibility):
      • Secure Coding Practices: lottie-android must be developed with rigorous secure coding practices, especially in any native code components. This includes:
        • Strict bounds checking.
        • Avoiding unsafe functions.
        • Using memory-safe languages where possible.
        • Regular security audits and code reviews.
      • Fuzz Testing: Extensive fuzz testing of the JSON parser and rendering engine is crucial to identify and fix vulnerabilities.
      • Input Sanitization (Deep): lottie-android must thoroughly sanitize all data extracted from the JSON, even seemingly harmless values. This goes beyond basic JSON validation.
      • Sandboxing (Process Isolation): If feasible, consider running the Lottie rendering engine in a separate, isolated process with limited permissions. This can contain the damage if a vulnerability is exploited. This is a more advanced mitigation.
      • Dependency Management: Carefully manage dependencies of lottie-android to ensure they are also secure and up-to-date.
    • Developer (Application-Level):
      • Regular Security Updates: Promptly apply updates to the lottie-android library to address any discovered vulnerabilities. This is the most important application-level mitigation for a library-level RCE.
      • Input Validation (Pre-emptive): While the core vulnerability is in the library, pre-emptive input validation (checking file size, basic structure) before passing the JSON to Lottie can reduce the attack surface.

Threat: Malicious JSON File - Resource Exhaustion (DoS) within Lottie

  • Description: An attacker crafts a Lottie JSON file with an extremely high number of layers, masks, effects, keyframes, or excessively large dimensions, specifically designed to exploit weaknesses in lottie-android's resource handling. This is not just about general resource limits, but about triggering a bug or inefficiency within the library's code.
  • Impact: Application crash, device unresponsiveness, battery drain, potential for device overheating. User experience is severely degraded. The key difference from a general DoS is that this exploits a lottie-android specific vulnerability.
  • Affected Component:
    • JsonCompositionLoader: Inefficient parsing of overly complex JSON structures.
    • LottieDrawable: Inefficient handling of complex animations during rendering.
    • Internal rendering engine (potentially involving native code): Memory leaks or excessive memory allocation within the library.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer (Library-Level - Airbnb's Responsibility):
      • Complexity Scoring: lottie-android should implement a complexity scoring system. This would assign a "score" to an animation based on its features (layers, masks, etc.) and reject animations exceeding a threshold. This is a critical library-level mitigation.
      • Memory Allocation Monitoring: Monitor memory allocation during parsing and rendering within the library. If allocation exceeds a predefined limit within the library's context, abort the process.
      • Optimized Rendering: Continuously optimize the rendering engine to handle complex animations efficiently.
      • Robust Error Handling: Implement robust error handling to gracefully handle cases where resource limits are exceeded within the library.
    • Developer (Application-Level):
      • Resource Limits (Configuration): Configure LottieAnimationView with limits: setMaxFrame(), setMinFrame(), setMaxProgress(), setMinProgress(). Use these to restrict animation duration and complexity, but this is a secondary defense. The library should handle this internally.
      • Timeout Handling: Implement a timeout for the entire loading and rendering process. If it exceeds the timeout, terminate it and display a fallback. Again, this is a secondary defense; the library should have internal timeouts.
      • Input Validation (Pre-emptive): Check for obvious red flags in the JSON file before passing it to Lottie (e.g., extremely large file size).