mitigations.md

Mitigation Strategies Analysis for mxgmn/wavefunctioncollapse

Mitigation Strategy: Strict Tile Set Schema Validation

1. Mitigation Strategy: Strict Tile Set Schema Validation

• Description:

  1. Define a Formal Schema: Create a JSON Schema (or equivalent) that precisely defines the structure and allowed values for tile set definitions that are fed into the wavefunctioncollapse library. This schema acts as a contract for valid input.
  2. Schema Elements: The schema should include:
     • Tile ID Format: Specify the allowed data type (integer, string) and any constraints (e.g., maximum length, allowed characters) for tile identifiers used by the library.
     • Tile Properties: Define required properties for each tile as expected by the library (e.g., image path if it uses images, color, metadata) and their data types.
     • Connectivity Rules: Define the structure for specifying how tiles connect according to the library's input format (e.g., "north," "south," "east," "west" connections, or more complex adjacency rules). Specify allowed values and relationships.
     • Cardinality Constraints: Limit the maximum number of tiles, the maximum number of connections per tile, and other quantitative limits to prevent the library from being overwhelmed.
  3. Implementation: Integrate a JSON Schema validator library into the application. Immediately before passing any tile set data to the wavefunctioncollapse library, pass it to the validator.
  4. Rejection: If the validator reports any errors (the input doesn't match the schema), reject the input immediately. Return a clear error message to the user indicating the specific validation failures. Do not call the wavefunctioncollapse library with invalid input.
  5. Example (Conceptual JSON Schema Snippet): (Same as before, but the emphasis is on validating input specifically for the library).

• List of Threats Mitigated:

  • Malicious Tile Set Injection (Severity: High): Prevents attackers from injecting arbitrary data into the tile set, which could lead to unexpected behavior within the wavefunctioncollapse library itself.
  • Data Type Mismatches (Severity: Medium): Ensures that tile properties and connection rules have the expected data types, preventing unexpected behavior or crashes within the library.
  • Schema Violation DoS (Severity: Medium): By limiting the size and complexity of the tile set (cardinality constraints), it helps prevent denial-of-service attacks that attempt to overload the wavefunctioncollapse library with excessively large inputs.

• Impact:

  • Malicious Tile Set Injection: Risk reduced significantly (close to elimination if the schema is comprehensive and the validator is correctly implemented).
  • Data Type Mismatches: Risk reduced to near zero.
  • Schema Violation DoS: Risk significantly reduced, but other DoS mitigations are still necessary.

• Currently Implemented:

  • Partially Implemented: Schema definition exists in tileset_schema.json. Validation is performed in the TileSetLoader class.
  • Missing cardinality constraints in the schema.

• Missing Implementation:

  • Cardinality constraints (maxItems, maxConnections, etc.) are not yet defined in tileset_schema.json.
  • The error messages returned to the user could be more specific about the validation failures.

Mitigation Strategy: Rule Logic Validation

2. Mitigation Strategy: Rule Logic Validation

• Description:

  1. Rule Representation: Define a clear and unambiguous way to represent the connection rules between tiles as understood by the wavefunctioncollapse library. This could be a custom data structure or a domain-specific language (DSL), but it must be compatible with the library's input format.
  2. Completeness Check: For each tile and each possible direction (or adjacency type) recognized by the library, verify that a rule exists. If a rule is missing, either:
     • Reject the tile set as incomplete.
     • Use a predefined default behavior (e.g., assume no connection) if the library supports default behaviors.
  3. Consistency Check: Examine pairs of rules to ensure they are not contradictory according to the logic of the wavefunctioncollapse library.
  4. Cycle Detection (If Applicable): If the specific wavefunctioncollapse implementation is known to be susceptible to infinite loops from cyclical rule patterns, implement an algorithm to detect and prevent these cycles.
  5. Implementation: Create a RuleValidator class that encapsulates these checks. This class should be called immediately before passing the rule set to the wavefunctioncollapse library.
  6. Rejection: If any rule validation checks fail, reject the tile set and provide a clear error message. Do not call the wavefunctioncollapse library with invalid rules.

• List of Threats Mitigated:

  • Infinite Loops (Severity: High): Prevents the wavefunctioncollapse algorithm from getting stuck in an infinite loop due to contradictory or cyclical rules within the library's internal logic.
  • Unexpected Output (Severity: Medium): Ensures that the generated output adheres to the intended rules, preventing nonsensical or inconsistent results produced by the library.
  • Logic Errors (Severity: Medium): Catches errors in the rule definitions that could lead to unexpected behavior within the library.

• Impact:

  • Infinite Loops: Risk significantly reduced (close to elimination if cycle detection is robust and applicable to the library).
  • Unexpected Output: Risk significantly reduced.
  • Logic Errors: Risk significantly reduced.

• Currently Implemented:

  • Partially Implemented: Basic consistency checks (e.g., checking for reciprocal connections) are implemented in the RuleValidator class.
  • Completeness check is missing.
  • Cycle detection is missing.

• Missing Implementation:

  • Completeness check (ensuring rules exist for all possible adjacencies) is not implemented.
  • Cycle detection algorithm is not implemented (and may not be necessary depending on the specific wavefunctioncollapse library used).
  • The RuleValidator needs to be integrated into the main processing pipeline immediately before the wavefunctioncollapse library call.

Mitigation Strategy: WFC Algorithm Timeout

3. Mitigation Strategy: WFC Algorithm Timeout

• Description:

  1. Set a Time Limit: Determine a reasonable maximum execution time for the wavefunctioncollapse library call. This should be based on:
     • The expected complexity of typical tile sets and rules that are valid inputs to the library.
     • The desired performance characteristics of the application.
     • Testing with various input sizes and complexities passed to the library.
  2. Implementation:
     • Use a timer mechanism (e.g., threading.Timer in Python) to track the execution time of the wavefunctioncollapse library function.
     • Start the timer immediately before calling the wavefunctioncollapse function.
     • If the timer expires before the wavefunctioncollapse algorithm completes, interrupt the algorithm.
  3. Interruption: The interruption mechanism must be compatible with the wavefunctioncollapse library. It might involve:
     • Setting a flag that the wavefunctioncollapse algorithm checks periodically (if the library supports this).
     • Raising an exception that the wavefunctioncollapse algorithm catches (if the library supports this).
     • Terminating the thread or process running the wavefunctioncollapse algorithm (use with caution and only if the library can handle this gracefully). This is the least desirable option.
  4. Error Handling: After interrupting the algorithm, handle the situation gracefully:
     • Log the timeout event.
     • Return an error message to the user indicating that the generation process timed out.
     • Clean up any resources used by the wavefunctioncollapse algorithm (if necessary and possible).
  5. Configuration: Make the timeout value configurable, but provide a safe default value.

• List of Threats Mitigated:

  • Denial of Service (DoS) via Complexity (Severity: High): Prevents attackers from causing a denial-of-service by providing inputs that lead to extremely long processing times within the wavefunctioncollapse library.
  • Infinite Loops (Severity: High): Provides a fallback mechanism to stop the algorithm if it gets stuck in an infinite loop due to unforeseen issues within the library.

• Impact:

  • DoS via Complexity: Risk significantly reduced.
  • Infinite Loops: Risk significantly reduced (provides a safety net).

• Currently Implemented:

  • Not Implemented: No timeout mechanism is currently in place.

• Missing Implementation:

  • The entire timeout mechanism needs to be implemented, including the timer, interruption logic (compatible with the library), and error handling. This should be integrated into the WFCProcessor class, specifically around the call to the wavefunctioncollapse library.

Mitigation Strategy: Output Size Limits

4. Mitigation Strategy: Output Size Limits

• Description:

  1. Define Maximum Dimensions: Determine the maximum allowed width and height for the generated output passed as parameters to the wavefunctioncollapse library.
  2. Implementation:
     • Before calling the wavefunctioncollapse library, check the requested output dimensions against the defined limits.
     • If the requested dimensions exceed the limits, reject the request and return an error message to the user. Do not call the wavefunctioncollapse library with excessive dimensions.
  3. Configuration: Make the maximum dimensions configurable, but with safe default values.

• List of Threats Mitigated:

  • Denial of Service (DoS) via Large Output (Severity: High): Prevents attackers from requesting extremely large outputs that could cause the wavefunctioncollapse library to consume excessive memory or processing time.
  • Resource Exhaustion (Severity: Medium): Helps prevent the application from running out of memory or other resources due to excessively large outputs generated by the library.

• Impact:

  • DoS via Large Output: Risk significantly reduced.
  • Resource Exhaustion: Risk significantly reduced.

• Currently Implemented:

  • Partially Implemented: Maximum width is limited to 500 in config.py.
  • Maximum height is not limited.

• Missing Implementation:

  • Maximum height limit needs to be added to config.py.
  • The error message should clearly indicate which dimension (width or height) exceeded the limit. The check must occur before calling the wavefunctioncollapse library.