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Threat Model Analysis for kitao/pyxel

Threat: Resource Spoofing/Replacement (Direct Pyxel Loading)

  • Description: An attacker replaces legitimate Pyxel resource files (.pyxel files, image files, sound files) that are loaded directly by Pyxel's pyxel.load() function. This bypasses any external loading mechanisms or wrappers. The attacker achieves this by modifying the application's distribution, compromising a network share (if resources are loaded from there), or exploiting a file system vulnerability.
    • Impact:
      • Display of malicious or inappropriate content (images, sounds).
      • Execution of altered game logic (due to modified tilemaps, sound events, or other data within the .pyxel file).
      • Potential crashes or instability if the replacement files are malformed.
      • Highly Unlikely, but Theoretically Possible: If a severe vulnerability existed in Pyxel's resource parsing code (e.g., a buffer overflow in the image decoder), a carefully crafted malicious resource file could potentially lead to arbitrary code execution. This is extremely improbable in a well-maintained library like Pyxel, but it's the theoretical worst-case scenario for any software that processes external data.
    • Pyxel Component Affected:
      • pyxel.load(): The core function for loading .pyxel resource files. This is the direct point of attack.
      • pyxel.image(): Used internally by pyxel.load() to handle image data.
      • pyxel.tilemap(): Used internally by pyxel.load() to handle tilemap data.
      • pyxel.sound(): Used internally by pyxel.load() to handle sound data.
      • pyxel.play(), pyxel.playm(): Used to play sounds and music loaded via pyxel.load().
    • Risk Severity: High (especially if resources are loaded from untrusted locations or if the distribution mechanism is weak).
    • Mitigation Strategies:
      • Checksum Validation (Crucial): Before calling pyxel.load(), calculate a cryptographic hash (e.g., SHA-256) of the resource file. Compare this hash to a known-good hash that is securely stored within the application code (or in a separate, digitally signed file). Reject the file if the hashes do not match. This is the primary defense against resource spoofing.
      • Secure Packaging (Essential): Use a packaging tool (PyInstaller, Nuitka, etc.) to bundle the resource files directly into the executable or a secure, self-contained archive. This makes it significantly harder for an attacker to tamper with the resources without modifying the entire application, which is more likely to be detected.
      • Digital Signatures (Strongly Recommended): Digitally sign the application executable (and/or the resource archive, if separate). This allows users (and the operating system) to verify the integrity of the application and ensure it hasn't been tampered with.
      • Avoid External Resource Loading (If Possible): The most secure approach is to avoid loading resources from external directories or network locations. If this is absolutely unavoidable, implement strict access controls and consider sandboxing (see below).
      • Sandboxing (If External Loading is Necessary): If external resource loading is unavoidable, run the Pyxel application within a sandboxed environment (e.g., a container, a virtual machine, or using operating system-level sandboxing features). This limits the application's access to the file system and other system resources, reducing the impact of a potential compromise.

Threat: Code Injection via Malicious Resource (Theoretical, but Important to Acknowledge)

  • Description: This is a highly unlikely but theoretically possible scenario. If a vulnerability existed in Pyxel's internal resource parsing code (e.g., a buffer overflow in the image decoding logic within pyxel.image(), a format string vulnerability in how tilemap data is processed within pyxel.tilemap(), or a similar flaw in pyxel.sound()), an attacker could craft a specially designed resource file that exploits this vulnerability to execute arbitrary code when pyxel.load() is called.
    • Impact:
      • Arbitrary Code Execution: The attacker gains complete control over the application and potentially the underlying system, depending on the application's privileges. This is the worst-case scenario.
    • Pyxel Component Affected:
      • pyxel.load(): The entry point for loading the malicious resource.
      • Potentially any of the internal resource handling functions: pyxel.image(), pyxel.tilemap(), pyxel.sound(), depending on the specific vulnerability.
    • Risk Severity: Critical (although the likelihood is very low).
    • Mitigation Strategies:
      • Keep Pyxel Updated (Paramount): The most important mitigation is to always use the latest stable version of Pyxel. Security vulnerabilities are often discovered and patched in software updates. By keeping Pyxel up-to-date, you benefit from these fixes.
      • Input Validation (Indirectly Relevant): While this threat focuses on vulnerabilities within Pyxel, robust input validation in your own code can help prevent scenarios where user-provided data might influence which resources are loaded, reducing the attack surface.
      • Sandboxing (Highly Recommended): Running the Pyxel application in a sandboxed environment (as described above) is a crucial mitigation for this type of threat. Even if arbitrary code execution is achieved, the sandbox limits the attacker's ability to interact with the rest of the system.
      • Avoid Custom Pyxel Forks (Unless Expert): Do not use custom or modified versions of Pyxel unless you are a security expert and have thoroughly audited the changes. Unofficial modifications could introduce new vulnerabilities.
      • Fuzzing (For Pyxel Developers): This mitigation is primarily for the developers of Pyxel itself. Fuzz testing (providing random or malformed data to the resource loading functions) can help identify potential vulnerabilities before they are exploited.