attack-surface.md

Attack Surface Analysis for zhanghai/materialfiles

Attack Surface: Broad File System Access

• Description: Access to the device's file system beyond the application's private storage.
  • materialfiles Contribution: The library's core function is file browsing and management, requiring broad file system permissions.
  • Example: An attacker exploits a separate vulnerability in the app to read arbitrary files on the SD card, leveraging materialfiles's granted READ_EXTERNAL_STORAGE permission.
  • Impact: Unauthorized access to sensitive user data (photos, documents, etc.), potential data modification or deletion.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer:
      • Request only the minimum necessary file system permissions. Prioritize scoped storage and SAF.
      • Implement robust input validation to prevent path traversal attacks.
      • Regularly audit permission usage and remove unnecessary permissions.
    • User:
      • Be cautious about granting broad file system permissions to any application.
      • Monitor app permissions and revoke unnecessary ones.

Attack Surface: Malicious Intent Handling

• Description: Vulnerabilities arising from insecure handling of Android Intents used for file operations.
  • materialfiles Contribution: The library likely uses Intents to open, share, and manage files, creating potential entry points for malicious Intents.
  • Example: An attacker crafts a malicious Intent that targets the app, causing it to share a sensitive file with the attacker's app without user consent.
  • Impact: Data leakage, unauthorized file sharing, potential for triggering vulnerabilities in other applications.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer:
      • Use explicit Intents whenever possible.
      • Thoroughly validate all incoming Intent data (action, data, type, extras).
      • Implement strict checks on the sender of the Intent.
      • Avoid blindly trusting data from external sources within Intents.
    • User:
      • Be aware of apps that request broad Intent-related permissions. (This is less directly controllable by the user).

Attack Surface: Symbolic Link (Symlink) Attacks

• Description: Exploiting improper handling of symbolic links to access files or directories outside the intended scope.
  • materialfiles Contribution: The library needs to handle symlinks when navigating the file system.
  • Example: An attacker creates a symlink in a publicly accessible directory that points to a sensitive file within the app's private storage. materialfiles, if not handling symlinks correctly, might follow this link and expose the sensitive file.
  • Impact: Unauthorized access to sensitive files, potential for data modification or deletion.
  • Risk Severity: High
  • Mitigation Strategies:
    • Developer:
      • Explicitly decide whether to follow symlinks. If not needed, disable them.
      • If symlinks must be followed, validate the target path after resolving the symlink to ensure it's within allowed boundaries.
      • Use canonical path resolution to prevent relative path traversal.
    • User:
      • No direct user mitigation, relies on developer best practices.