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Mitigation Strategies Analysis for bookstackapp/bookstack

Mitigation Strategy: Strict File Upload Configuration (within BookStack)

Description:

  1. ALLOWED_EXTENSIONS: In the BookStack .env file, set the ALLOWED_EXTENSIONS variable to a very restrictive list of allowed file extensions. Prioritize safer formats (e.g., jpg,jpeg,png,gif,pdf,txt). Avoid overly permissive extensions and never allow executable extensions. Example: ALLOWED_EXTENSIONS=jpg,jpeg,png,gif,pdf,txt,docx,xlsx,pptx
  2. UPLOAD_MAX_SIZE: In the .env file, set UPLOAD_MAX_SIZE to a reasonable value (e.g., 10M or lower, depending on your needs). This limits the size of files that can be uploaded through BookStack.
  3. (Code Review/Modification - Advanced): Review the BookStack PHP code responsible for file uploads (likely in controllers related to attachments and images). Ensure that:
    • MIME type validation is performed server-side, using a reliable method (e.g., PHP's finfo extension), not just relying on the file extension or client-provided MIME type.
    • Uploaded files are properly sanitized to prevent any potential injection vulnerabilities.
    • File names are sanitized to prevent path traversal attacks.
    • If possible, implement a mechanism to rename uploaded files to prevent potential conflicts or overwrites.

  • Threats Mitigated:

    • Remote Code Execution (RCE) (Critical Severity): Preventing the upload of executable files directly mitigates RCE.
    • Cross-Site Scripting (XSS) (High Severity): Restricting file types and (ideally) validating MIME types helps prevent the upload of malicious HTML or SVG files.
    • Denial of Service (DoS) (Medium Severity): UPLOAD_MAX_SIZE limits prevent attackers from uploading excessively large files.

  • Impact:

    • RCE: Reduces risk significantly (from Critical to Low, if code modifications are implemented).
    • XSS: Reduces risk (from High to Medium/Low, depending on the robustness of MIME type validation).
    • DoS: Reduces risk significantly (from Medium to Low).

  • Currently Implemented:

    • ALLOWED_EXTENSIONS and UPLOAD_MAX_SIZE are configurable in the .env file.
    • The level of server-side MIME type validation and file sanitization within BookStack's code needs verification and potentially improvement.

  • Missing Implementation:

    • Robust, guaranteed server-side MIME type validation and comprehensive file sanitization within the core code (often requires code review and potential modification).

Mitigation Strategy: Regular Permission Review and Least Privilege (within BookStack's Interface)

Description:

  1. Access BookStack's Admin Area: Log in to BookStack as an administrator.
  2. Navigate to Users/Roles: Go to the "Users" and "Roles" sections in the settings.
  3. Review User Roles: For each user, verify that their assigned role is the minimum necessary for their tasks. Avoid overusing the "Admin" role.
  4. Review Role Permissions: For each role (including custom roles), carefully examine the assigned permissions. Remove any unnecessary permissions.
  5. Check Public Role: Pay special attention to the "Public" role. Ensure that only content intended for public access is accessible to this role.
  6. Repeat Regularly: Perform this review process at least every 3-6 months, or more frequently in high-security environments.

  • Threats Mitigated:

    • Unauthorized Data Access (High Severity): Ensures users can only access content they are authorized to see.
    • Unauthorized Data Modification (High Severity): Prevents unauthorized users from modifying or deleting content.
    • Privilege Escalation (High Severity): Reduces the risk of users accumulating excessive permissions.

  • Impact:

    • Unauthorized Data Access: Reduces risk significantly (from High to Low/Medium).
    • Unauthorized Data Modification: Reduces risk significantly (from High to Low/Medium).
    • Privilege Escalation: Reduces risk significantly (from High to Low/Medium).

  • Currently Implemented:

    • BookStack provides a built-in role-based permission system accessible through the admin interface.

  • Missing Implementation:

    • The discipline of regularly reviewing and enforcing least privilege is a procedural mitigation; BookStack provides the tools, but the administrator must use them effectively.

Mitigation Strategy: Configure Session Timeout (within BookStack)

Description:

  1. Edit .env File: Open the .env file in your BookStack installation.
  2. Set SESSION_LIFETIME: Find the SESSION_LIFETIME variable. Set it to a reasonable value (in minutes). A common value is 30 (30 minutes). A shorter timeout is more secure but may be less convenient for users. Example: SESSION_LIFETIME=30
  3. Save Changes: Save the .env file.
  4. Restart Services: Restart your web server and any relevant services (e.g., PHP-FPM) for the changes to take effect.

  • Threats Mitigated:

    • Session Hijacking (High Severity): Reduces the window of opportunity for an attacker to hijack an inactive session.

  • Impact:

    • Session Hijacking: Reduces risk (from High to Medium).

  • Currently Implemented:

    • SESSION_LIFETIME is configurable in the .env file.

  • Missing Implementation:

    • None, as long as the administrator sets a reasonable value for SESSION_LIFETIME.

Mitigation Strategy: Disable Unnecessary Features (within BookStack's Configuration)

Description:

  1. Review .env file and Settings: Examine the .env file and BookStack's settings (accessible through the admin interface) for features that are not essential to your use case.
  2. Disable Features:
    • Comments: If comments are not needed, disable them. This reduces the attack surface for XSS and other comment-related vulnerabilities. This is usually a setting within the admin interface.
    • Custom HTML Attributes: If you don't need to allow users to add custom HTML attributes to elements, disable this feature. This reduces the risk of XSS. This is usually a setting within the admin interface, often related to Markdown or editor settings.
    • Registration: If you don't need public user registration, disable it in the .env file (REGISTRATION_ENABLED=false).
    • Other Features: Look for any other features that are not being used and disable them.
  3. Save and Restart: Save any changes to the .env file and restart relevant services.

  • Threats Mitigated:

    • XSS (High Severity): Disabling features like comments and custom HTML attributes reduces the attack surface for XSS.
    • Other Feature-Specific Vulnerabilities (Variable Severity): Disabling any unused feature reduces the risk of vulnerabilities specific to that feature.

  • Impact:

    • XSS: Reduces risk (from High to Medium/Low, depending on which features are disabled).
    • Other Vulnerabilities: Reduces risk (variable, depending on the feature).

  • Currently Implemented:

    • BookStack provides settings (in the .env file and the admin interface) to disable various features.

  • Missing Implementation:

    • The administrator must actively review and disable unnecessary features.

Mitigation Strategy: Review and Sanitize Custom HTML/JavaScript (if used)

Description:

  1. Identify Custom Code: If you have allowed custom HTML or JavaScript (through configuration or extensions), locate all instances of this code.
  2. Review for Vulnerabilities: Carefully review the custom code for potential security vulnerabilities, such as:
    • XSS vulnerabilities (e.g., improper handling of user input).
    • Use of outdated or vulnerable JavaScript libraries.
    • Any code that could be used to bypass BookStack's security mechanisms.
  3. Sanitize Input: If the custom code handles user input, ensure that the input is properly sanitized to prevent XSS and other injection attacks. Use appropriate escaping and encoding techniques.
  4. Limit Permissions: If possible, limit the permissions of the custom code to the minimum necessary.
  5. Consider Alternatives: If possible, consider using built-in BookStack features or trusted extensions instead of custom code.
  6. Disable if not essential: If custom HTML/JS is not absolutely required, disable the feature entirely.

  • Threats Mitigated:

    • XSS (High Severity): The primary threat mitigated by this strategy.
    • Other Code-Specific Vulnerabilities (Variable Severity): Depends on the specific custom code.

  • Impact:

    • XSS: Reduces risk significantly (from High to Low, if the code is properly reviewed and sanitized).
    • Other Vulnerabilities: Reduces risk (variable, depending on the code).

  • Currently Implemented:

    • BookStack may allow custom HTML/JavaScript in certain contexts (e.g., through extensions or configuration). The level of built-in sanitization needs verification.

  • Missing Implementation:

    • Thorough review and sanitization of any custom code are the responsibility of the administrator or developer who added the code. BookStack cannot automatically guarantee the security of arbitrary custom code. The option to disable custom HTML/JS entirely is often the safest approach.