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Attack Tree Analysis for miguelpruivo/flutter_file_picker

Objective: To gain unauthorized access to sensitive data, execute arbitrary code, or cause a denial-of-service (DoS) on the target device or application by exploiting vulnerabilities within the flutter_file_picker package or its interaction with the underlying operating system.

Attack Tree Visualization

                                      [Attacker's Goal]
                                                        |
                                      -------------------------
                                      |
                      **[1. Exploit File Handling Vulnerabilities]**
                                      |
                      -----------------------------------
                      |                 |
**[1.1 Path Traversal] [HR]**  **[1.2 Malicious]**
                      |   **[File Upload] [HR]**
                      |                 |
    ---------------------             |
    |                   |             |
[1.1.1 Read Arbitrary]  |   **[1.2.1 Overly]**
[Files from Device][HR]|   **[Permissive]**
    |                   |   **[File Type]**
**[1.1.2 Write to]**       |   **[Filtering] [HR]**
**[Arbitrary Locations]**  |             |
                      |   [1.2.2 Lack]
                      |   [of Size]
                      |   [Limits] [HR]

Attack Tree Path: Critical Node: [1. Exploit File Handling Vulnerabilities]

  • Description: This is the overarching category for vulnerabilities arising from how the application (using flutter_file_picker) handles files and interacts with the file system. The core issue is often insufficient validation of file paths and file content after they are obtained from the picker.
  • Mitigation Strategies:
    • Implement rigorous input validation on all file paths.
    • Enforce strict file type and size restrictions.
    • Handle symbolic links carefully (or avoid them).
    • Use platform-specific security features (sandboxing, etc.).
    • Keep all dependencies updated.

Attack Tree Path: Critical Node/High-Risk Path: [1.1 Path Traversal]

  • Description: The attacker manipulates file paths provided to the application (after being selected via flutter_file_picker) to access or modify files outside the intended directory. This is done by injecting special characters like "../" into the path.
  • Sub-Node/High-Risk Path: [1.1.1 Read Arbitrary Files from Device]
    • Description: The attacker successfully reads sensitive files (configuration files, private keys, etc.) by escaping the intended directory using path traversal techniques.
    • Example: An attacker selects a file, but the application uses a vulnerable path construction like: /var/www/uploads/${user_selected_filename}. The attacker provides a filename like ../../../../etc/passwd, resulting in the application reading /etc/passwd.
    • Mitigation: Sanitize and validate file paths before using them. Use a whitelist approach for allowed characters. Normalize paths using platform-specific functions.
  • Critical Node: [1.1.2 Write to Arbitrary Locations]
    • Description: The attacker overwrites critical system files or application files, potentially leading to code execution or denial of service.
    • Example: Similar to reading, but the attacker provides a filename that allows them to write to a critical location, like a system configuration file or a directory containing executable code.
    • Mitigation: Same as 1.1.1, plus ensure the application runs with the least necessary privileges.

Attack Tree Path: Critical Node/High-Risk Path: [1.2 Malicious File Upload]

  • Description: The attacker uploads a file that exploits vulnerabilities in the application or system. This relies on the application using the selected file in a way that's vulnerable. flutter_file_picker facilitates the selection, but the application's handling of the file is the key.
  • Sub-Node/High-Risk Path: [1.2.1 Overly Permissive File Type Filtering]
    • Description: The application doesn't properly restrict the types of files that can be selected and subsequently processed. This allows attackers to upload executable files, scripts, or files that exploit known vulnerabilities in other software.
    • Example: The application allows uploading any file type. The attacker uploads a PHP script, and if the server executes PHP files in the upload directory, the attacker gains code execution.
    • Mitigation:
      • Use the allowedExtensions parameter in flutter_file_picker to restrict file types to a minimal, necessary set.
      • After selection, validate the file's MIME type using a reliable library (don't rely solely on the file extension).
      • Consider using a file scanning service to detect malicious content.
    • Sub-Node/High-Risk Path: [1.2.2 Lack of Size Limits]
      • Description: The application doesn't enforce reasonable size limits on uploaded files.
      • Example: An attacker uploads a very large file, consuming all available disk space or memory, leading to a denial-of-service.
      • Mitigation: Enforce a maximum file size limit both on the client-side (using JavaScript/Dart) and on the server-side.