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Attack Surface Analysis for cocos2d/cocos2d-x

Attack Surface: Resource Loading and Path Traversal (Cocos2d-x File Utilities)

  • Description: Vulnerabilities arising from how Cocos2d-x's resource loading mechanisms handle file paths, potentially allowing attackers to access or manipulate files outside the intended application sandbox. This focuses specifically on the FileUtils class and related functions within Cocos2d-x.
  • Cocos2d-x Contribution: Cocos2d-x's FileUtils class provides the core functions for loading resources (images, audio, scripts, etc.). Insecure use of these functions (e.g., constructing file paths from user-supplied data without proper sanitization) directly introduces the vulnerability.
  • Example:
    • An attacker provides a crafted configuration file that includes a resource path like "../../../../etc/passwd" to a function like Sprite::create(). If FileUtils::fullPathForFilename (or a related function) doesn't properly sanitize this, the application might attempt to load the system's password file.
  • Impact:
    • Information disclosure (reading sensitive files).
    • Potential code execution (if a malicious script is loaded).
    • Denial of service.
  • Risk Severity: High to Critical
  • Mitigation Strategies:
    • Strict Path Validation: Never construct file paths directly from user input within Cocos2d-x functions. Use a whitelist of allowed directories and filenames. Sanitize all paths to remove potentially dangerous characters (e.g., "..", "/", "\"). Rely on FileUtils::fullPathForFilename and related functions correctly, ensuring they are used as intended to resolve paths within the application's resource directory.
    • Resource Integrity Checks: Verify the integrity of downloaded resources (if applicable) using checksums (e.g., SHA-256) or digital signatures before passing them to Cocos2d-x loading functions.
    • Sandboxing: Ensure the application, and therefore Cocos2d-x's file access, operates within a restricted environment (sandbox) that limits its access to the filesystem.
    • Resource Loading Limits: Implement limits on the size and number of resources that Cocos2d-x can load to prevent resource exhaustion attacks.

Attack Surface: Scripting Engine Exploitation (Cocos2d-x Bindings)

  • Description: Vulnerabilities in how Cocos2d-x integrates with and exposes its API to scripting engines (Lua or JavaScript), allowing attackers to inject and execute malicious code through the engine's bindings.
  • Cocos2d-x Contribution: Cocos2d-x provides the bindings that allow Lua and JavaScript scripts to interact with the engine's C++ code. The security of these bindings is paramount. If the bindings allow unsafe access to native functions or don't properly validate input from scripts, this creates a direct attack vector.
  • Example:
    • A game uses Cocos2d-x's Lua bindings. A vulnerability in the binding for a function that modifies game state allows an attacker to inject Lua code that calls this function with arbitrary parameters, leading to unintended game behavior or even a crash. Or, a binding might expose a function that should be internal, allowing a script to bypass security checks.
  • Impact:
    • Complete application compromise (arbitrary code execution through the scripting engine).
    • Data theft.
    • Denial of service.
    • Modification of game state.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Input Sanitization (at the Binding Level): Crucially, sanitize all input passed from scripts to Cocos2d-x's C++ functions through the bindings. Treat all script input as untrusted. This is often more important than sanitizing user input within the script itself, as the bindings are the gatekeeper.
    • Secure Bindings: Use a secure, up-to-date version of Cocos2d-x. The Cocos2d-x developers are responsible for the security of the bindings, so staying updated is essential.
    • Minimal API Exposure: Expose only the absolutely necessary Cocos2d-x functions to the scripting engine. Avoid exposing internal or sensitive functions. Carefully review the API exposed to scripts.
    • Code Review (of Bindings): If you are modifying or extending Cocos2d-x's bindings, perform a thorough security code review of the binding code itself.
    • Sandboxing (of the Scripting Engine): Even with secure bindings, consider running the scripting engine in a separate, isolated process with limited privileges, if possible. This limits the damage if the scripting engine itself is compromised.

Attack Surface: Deserialization of Untrusted Data (Cocos2d-x Data Structures)

  • Description: Vulnerabilities arising from Cocos2d-x deserializing data from untrusted sources (network, files) into its own data structures without proper validation. This is specifically about Cocos2d-x's own serialization/deserialization mechanisms, if any are used.
  • Cocos2d-x Contribution: If Cocos2d-x provides built-in mechanisms for serializing and deserializing its own objects (e.g., Node hierarchies, custom data structures), and these mechanisms are used to process untrusted data, this creates a direct vulnerability. Note: Cocos2d-x primarily relies on external formats like JSON or platform-specific serialization, but if custom serialization is used, this becomes relevant.
  • Example:
    • If Cocos2d-x had a built-in function to deserialize a Node tree from a custom binary format, and this function was used to load data from a downloaded file, an attacker could craft a malicious file that, when deserialized, triggers a buffer overflow or other memory corruption vulnerability within Cocos2d-x's internal code.
  • Impact:
    • Arbitrary code execution (within the context of Cocos2d-x).
    • Data corruption.
    • Denial of service.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Avoid Untrusted Deserialization (with Cocos2d-x's mechanisms): If Cocos2d-x provides custom serialization, avoid using it to deserialize data from untrusted sources. Prefer standard, well-vetted formats like JSON (with appropriate security precautions).
    • Whitelist-Based Deserialization (if unavoidable): If you must use Cocos2d-x's custom deserialization with untrusted data, implement strict whitelisting of allowed classes/types. Reject any data that attempts to deserialize an unapproved object. This requires deep understanding of Cocos2d-x's internals.
    • Input Validation (before Cocos2d-x deserialization): Before passing data to Cocos2d-x's deserialization functions, perform rigorous validation of the data's structure and content.
    • Secure Parsers (if applicable): If Cocos2d-x's deserialization uses a custom parser, ensure that parser is secure and resistant to common parsing vulnerabilities.
    • Limited Privileges: Run the code that uses Cocos2d-x's deserialization functions in a context with limited privileges.