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threat-modeling.md

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Threat Model Analysis for apache/commons-io

Threat: Path Traversal (Directory Traversal)

Threat: Path Traversal

  • Description: An attacker crafts malicious input containing path traversal sequences (e.g., ../, absolute paths) that are passed to Apache Commons IO functions like FileUtils.readFileToString, FileUtils.copyFile, or FileUtils.openInputStream. Due to insufficient input validation or sanitization before using these Commons IO functions, the attacker can bypass intended directory restrictions and access or manipulate files outside the application's designated file system scope. For example, by manipulating a filename parameter in a web request, an attacker could force FileUtils.readFileToString to read sensitive system files like /etc/passwd.
  • Impact:
    • Information Disclosure: Reading sensitive files, including application source code, configuration files, and user data.
    • Data Tampering/Modification: Potentially writing to or modifying files outside the intended application directory if write operations are involved, leading to application compromise or data corruption.
    • Denial of Service: Accessing or manipulating critical system files, potentially causing application or system instability or failure.
  • Affected Commons-IO Component:
    • FileUtils module functions that operate on file paths: readFileToString, readFileToByteArray, copyFile, copyDirectory, openInputStream, openOutputStream, listFiles, deleteDirectory, and others that take file paths as arguments.
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Strict Input Validation and Sanitization (Pre-Commons IO Usage): Before passing any user-provided input to Commons IO file path functions, rigorously validate and sanitize the input. Implement whitelisting of allowed characters and patterns. Reject any input that contains directory traversal sequences or characters.
    • Canonicalization (Pre-Commons IO Usage): Canonicalize file paths using File.getCanonicalPath() before using them with Commons IO functions. This resolves symbolic links and relative paths, helping to prevent traversal attempts. Verify that the canonical path remains within the expected base directory.
    • Secure Path Construction (Pre-Commons IO Usage): Ensure that file paths are constructed securely and are always within the intended application's file system scope. Avoid directly concatenating user input into file paths without validation.
    • Principle of Least Privilege: Run the application with the minimum necessary file system permissions. Restrict the application's access to only the directories it absolutely needs to access.

Threat: Denial of Service (DoS) through Large File Operations

Threat: Resource Exhaustion via Large File Operations

  • Description: An attacker can exploit Apache Commons IO functions, particularly within the FileUtils module, to initiate resource-intensive file system operations that consume excessive server resources (CPU, memory, disk I/O). This is achieved by providing input that leads to Commons IO performing operations on extremely large files or directories. For example, an attacker could upload a very large file that the application then attempts to copy using FileUtils.copyFile without proper size limits, overwhelming server resources. Or, they could trigger FileUtils.deleteDirectory on a path pointing to an extremely large directory structure.
  • Impact:
    • Application Denial of Service: The application becomes slow, unresponsive, or crashes due to resource exhaustion, preventing legitimate users from accessing it.
    • System Instability: In severe cases, resource exhaustion can impact the stability of the entire server or system hosting the application.
  • Affected Commons-IO Component:
    • FileUtils module functions involved in file and directory copying, writing, and deletion, especially when dealing with potentially large files or directories: copyFile, copyDirectory, writeByteArrayToFile, writeStringToFile, deleteDirectory.
  • Risk Severity: High
  • Mitigation Strategies:
    • Implement File Size Limits (Pre-Commons IO Usage): Before using Commons IO functions to process uploaded files or files specified by user input, enforce strict limits on the maximum allowed file size. Reject requests that exceed these limits.
    • Resource Quotas and Monitoring: Implement resource quotas to limit the amount of disk space, memory, and CPU time that can be consumed by file operations. Monitor resource usage to detect and respond to potential DoS attacks.
    • Asynchronous Operations and Timeouts: For potentially long-running file operations using Commons IO, perform them asynchronously and implement timeouts to prevent indefinite blocking of application threads.
    • Rate Limiting: Implement rate limiting on file upload and file system operation requests to prevent attackers from rapidly triggering resource-intensive operations.
    • Careful Use of Recursive Operations: When using recursive directory operations like FileUtils.deleteDirectory or FileUtils.copyDirectory, especially on user-controlled paths, implement safeguards such as depth limits and timeouts to prevent excessive resource consumption on deeply nested structures.

Threat: File Content Manipulation/Injection (Indirectly through Improper Usage)

Threat: Code Injection or Configuration Tampering via File Content Manipulation

  • Description: While Apache Commons IO itself does not directly introduce code injection, improper application design combined with the use of Commons IO for reading file content can create vulnerabilities. If an application uses Commons IO functions like FileUtils.readFileToString to read configuration files, scripts, or other data files, and then unsafely processes this content (e.g., executes it as code, interprets it without validation), an attacker who can manipulate the file content (potentially through path traversal or other vulnerabilities outside of Commons IO itself, but exacerbated by its use) can inject malicious code or alter application behavior. The vulnerability arises from the application's unsafe handling of the file content read by Commons IO, not from Commons IO itself.
  • Impact:
    • Remote Code Execution (RCE): If the application interprets file content as code, an attacker can inject and execute arbitrary code on the server.
    • Configuration Tampering: An attacker can modify application behavior by manipulating configuration files read and used by the application.
  • Affected Commons-IO Component:
    • FileUtils module functions used for reading file content: readFileToString, readFileToByteArray, lineIterator. These functions are tools used in a potentially vulnerable application flow.
  • Risk Severity: Critical (if code execution is possible)
  • Mitigation Strategies:
    • Never Execute Untrusted File Content: Avoid executing or interpreting file content read using Commons IO as code unless absolutely necessary and with extreme caution.
    • Strict Input Validation for Configuration/Data Files (Post-Commons IO Read): After reading configuration or data files with Commons IO, rigorously validate and sanitize the content before using it in the application. Implement parsing and validation logic to ensure only expected data is processed.
    • Principle of Least Privilege: Run the application with the minimum necessary privileges to limit the impact of potential code execution vulnerabilities.
    • Sandboxing/Isolation: If executing scripts or code read from files is unavoidable, use sandboxing or isolation techniques to limit the potential damage from malicious code.
    • Secure Configuration Parsing: Use secure and well-vetted libraries for parsing configuration files. Avoid using insecure methods like eval() or similar functions to process file content.