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attack-surface.md

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Attack Surface Analysis for apache/commons-io

Attack Surface: Path Traversal Vulnerability

  • Description: Attackers can manipulate file paths provided to the application to access files or directories outside of the intended scope, potentially gaining unauthorized access to sensitive data or system files.
  • Commons-IO Contribution: Commons IO provides file manipulation utilities (copy, move, read, write, delete) that operate on file paths. If these paths are constructed using unsanitized user input, Commons IO functions become the execution point for path traversal attacks.
  • Example: An application uses FileUtils.readFileToString(new File(userInputFilename), StandardCharsets.UTF_8) to read files based on user input. An attacker provides userInputFilename as ../../../../etc/passwd. Commons IO will attempt to read /etc/passwd if the application has sufficient permissions, bypassing intended access controls.
  • Impact: Unauthorized file access, reading sensitive data (passwords, configuration files, application data), potential for arbitrary code execution if combined with other vulnerabilities (e.g., file upload leading to web shell).
  • Risk Severity: High to Critical
  • Mitigation Strategies:
    • Input Validation: Strictly validate user input for filenames and paths. Use allow-lists of permitted characters and patterns. Reject or sanitize input containing path traversal sequences like ../ or absolute paths.
    • Path Normalization: Canonicalize file paths using methods provided by the operating system or programming language to resolve symbolic links and remove redundant path components. Ensure the normalized path stays within the expected base directory.
    • Sandboxing/Chroot: If possible, restrict the application's file system access to a specific directory (sandbox or chroot environment). This limits the impact of path traversal vulnerabilities.
    • Principle of Least Privilege: Run the application with minimal file system permissions required for its functionality. Avoid granting excessive permissions that could be exploited.

Attack Surface: Denial of Service (DoS) via Resource Exhaustion

  • Description: Attackers can cause a denial of service by exhausting server resources (CPU, memory, disk space) by providing excessively large files or streams as input to file processing operations.
  • Commons-IO Contribution: Commons IO offers utilities for copying, reading, and processing files and streams. Functions like FileUtils.copyFile, FileUtils.readFileToByteArray, and IOUtils.copy can be exploited if used without proper resource limits when handling untrusted input.
  • Example: An application uses FileUtils.copyFile(uploadedFile, destinationFile) to process uploaded files. An attacker uploads an extremely large file (e.g., several gigabytes). Commons IO attempts to copy this entire file, potentially exhausting server disk space or memory, leading to application slowdown or crash.
  • Impact: Application slowdown, service unavailability, server crash, resource exhaustion (disk space, memory, CPU).
  • Risk Severity: High
  • Mitigation Strategies:
    • File Size Limits: Implement strict limits on the size of uploaded files or files processed by the application. Reject files exceeding these limits.
    • Stream Processing with Limits: When processing streams, use buffered input/output and consider implementing limits on the amount of data processed or time spent processing.
    • Resource Monitoring and Throttling: Monitor server resource usage (CPU, memory, disk I/O). Implement throttling or rate limiting for file processing operations to prevent resource exhaustion from excessive requests.
    • Asynchronous Processing: For long-running file operations, consider using asynchronous processing or background tasks to avoid blocking the main application thread and improve responsiveness.