mitigations.md

Mitigation Strategies Analysis for zhanghai/materialfiles

Mitigation Strategy: Strict materialfiles API Usage (Least Privilege)

Description:

1. API Review: Thoroughly examine the materialfiles API documentation. Identify all API calls currently used within your application.
2. Least Privilege Selection: For each file operation, meticulously choose the most restrictive materialfiles API call that accomplishes the required functionality.
   • Favor specific methods like getFile() or getDirectory() over broader methods.
   • If you only need to read file metadata, use methods designed only for reading metadata, not methods that also allow writing.
   • If an API offers options for restricting access (e.g., read-only mode), always use those options when write access is not strictly necessary.
3. Avoid Dangerous APIs: Identify any materialfiles APIs that are marked as potentially dangerous or deprecated in the library's documentation. Avoid these unless absolutely essential, and if used, implement extra precautions (see other mitigation strategies).
4. Parameter Validation: Even when using the correct API, validate all parameters passed to materialfiles functions. This includes file paths, file names, and any other data provided to the library. This prevents passing potentially malicious data that could exploit internal library vulnerabilities.

Threats Mitigated:

• Unintended File Access Permissions (High Severity): Directly reduces the risk of the application using the library to access files in unintended ways due to developer error in choosing overly permissive API calls.
• Vulnerabilities within materialfiles (Variable Severity): Mitigates the risk of exploits that rely on passing malicious input to vulnerable materialfiles API calls, or triggering unintended behavior through less-secure API choices.

Impact:

• Unintended File Access Permissions: Risk moderately reduced (Medium Impact). This is "moderate" because even with the correct API, underlying library bugs could still exist.
• Vulnerabilities within materialfiles: Risk moderately to significantly reduced (Medium to High Impact), depending on the specific vulnerability.

Currently Implemented: (Example - Needs to be filled in by the development team)

• Some effort has been made to use specific read methods in FileViewerActivity.

Missing Implementation: (Example - Needs to be filled in by the development team)

• A comprehensive review of all materialfiles API usage across the entire project has not been conducted.
• FileManager.listFiles() is used in several places where a more specific method (e.g., listing only directories or only files) could be used.
• No systematic validation of parameters passed to all materialfiles functions is in place.

Mitigation Strategy: Input Validation Before materialfiles API Calls

Description:

1. Identify All Input Points: Identify all points in your application where data (especially file paths, file names, or user-provided content that influences file operations) is received from untrusted sources. This includes user input, data from external storage, network data, etc.
2. Pre-materialfiles Validation: Before passing any data to any materialfiles API call, rigorously validate and sanitize that data. This is crucial, even if you are using the "correct" API calls from the previous strategy.
   • Path Traversal Prevention: Explicitly check for and reject any input containing path traversal sequences (e.g., "..", "//", potentially encoded versions).
   • Whitelist Characters: Define a strict whitelist of allowed characters for file names and path components. Reject any input containing characters outside this whitelist.
   • Canonicalization: Use File.getCanonicalPath() to resolve the path to its canonical form before passing it to any materialfiles function. This handles symbolic links and relative paths securely, preventing bypasses of other checks.
   • Regular Expressions: Employ regular expressions to enforce a specific, safe structure for file paths and names.
3. Fail Securely: If validation fails, do not proceed with the materialfiles operation. Log the error, inform the user appropriately (without revealing sensitive information), and handle the error gracefully.

Threats Mitigated:

• Unintended File Access Permissions (High Severity): Prevents the application from being tricked into using materialfiles to access files outside of intended boundaries due to malicious input.
• Vulnerabilities within materialfiles (Variable Severity): A critical defense against exploits that rely on passing crafted, malicious input (e.g., specially formatted file paths) to materialfiles API calls. This is your first line of defense against many potential library vulnerabilities.

Impact:

• Unintended File Access Permissions: Risk significantly reduced (High Impact).
• Vulnerabilities within materialfiles: Risk significantly reduced (High Impact). This is arguably the most important mitigation for library-specific vulnerabilities.

Currently Implemented: (Example - Needs to be filled in by the development team)

• Basic null and empty string checks are performed in some areas.

Missing Implementation: (Example - Needs to be filled in by the development team)

• No comprehensive input validation is performed before every materialfiles API call.
• No whitelisting of characters is implemented.
• No explicit checks for path traversal sequences are consistently performed.
• Canonicalization is not used universally before calling materialfiles functions.
• Regular expressions validation is missing.

Mitigation Strategy: File Operation Timeouts (Within materialfiles Context)

Description:

1. Identify Long-Running Operations: Identify any materialfiles API calls that could potentially take a significant amount of time to complete (e.g., listing a directory with a very large number of files, copying a large file).
2. Implement Timeouts: Wrap calls to these potentially long-running materialfiles APIs within timeout mechanisms.
   • Use java.util.concurrent classes (e.g., ExecutorService, Future, Callable) to execute the materialfiles operation in a separate thread.
   • Set a reasonable timeout value for the operation.
   • Use Future.get(timeout, unit) to retrieve the result of the operation, waiting only for the specified timeout.
3. Handle TimeoutException: Catch TimeoutException and handle it gracefully. This might involve:
   • Cancelling the underlying materialfiles operation (if the API supports cancellation).
   • Logging the timeout.
   • Displaying an appropriate error message to the user.
   • Retrying the operation (with caution, and potentially with a longer timeout, up to a maximum limit).
4. Consider materialfiles's own timeout mechanisms: Check if the materialfiles library itself provides any built-in timeout mechanisms for its operations. If so, use those in addition to your own timeouts.

Threats Mitigated:

• Denial of Service via Resource Exhaustion (Medium Severity): Prevents attackers from causing a denial-of-service by triggering materialfiles operations that consume excessive resources or take an extremely long time to complete.
• Vulnerabilities within materialfiles (Variable Severity): Some vulnerabilities might only be exploitable under specific timing conditions or with very long operations. Timeouts can help mitigate these.

Impact:

• Denial of Service via Resource Exhaustion: Risk significantly reduced (High Impact).
• Vulnerabilities within materialfiles: Risk moderately reduced (Medium Impact).

Currently Implemented: (Example - Needs to be filled in by the development team)

• No timeouts are currently implemented for any materialfiles operations.

Missing Implementation: (Example - Needs to be filled in by the development team)

• Timeouts need to be implemented for all potentially long-running materialfiles API calls, especially those involving listing directories, copying files, or performing other I/O-intensive operations.