mitigations.md

Mitigation Strategies Analysis for handlebars-lang/handlebars.js

Mitigation Strategy: Context-Aware Escaping with Custom Helpers

• Description:

  1. Identify Contexts: Analyze all Handlebars templates and identify where user-supplied data is used. Categorize these uses into distinct contexts:
     • HTML body (text content)
     • HTML attributes (e.g., href, title, value)
     • JavaScript code (within <script> tags or inline event handlers)
     • URLs (parts of URLs, query parameters)
     • CSS (within <style> tags or inline styles – highly discouraged)
  2. Create Custom Helpers: For each identified context (except the basic HTML body, which uses double braces), create a dedicated Handlebars helper. These helpers will encapsulate the correct escaping logic, directly using Handlebars' API or integrating with other libraries through the Handlebars helper mechanism.
     • escapeAttribute: For HTML attributes.
     • escapeJS: For JavaScript contexts.
     • escapeURL: For URL contexts.
     • safeString: Only for pre-sanitized HTML, and this helper should internally call a sanitization function before using Handlebars.SafeString.
  3. Replace Triple Braces: Systematically replace all instances of triple braces ({{{ }}}) within the Handlebars templates with the appropriate custom helper or double braces ({{ }}}).
  4. Enforce Usage: Through code reviews and potentially custom linting rules (if possible, targeting Handlebars template files), ensure that developers always use the correct helper for the given context within the templates.
  5. Regular Audits: Periodically review the Handlebars templates and helper implementations to ensure consistency and correctness.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) (High Severity): Mitigates XSS attacks by ensuring that user-supplied data is properly escaped within the Handlebars templating system for the specific context in which it's used.
  • HTML Injection (Medium Severity): Prevents attackers from injecting arbitrary HTML tags through the Handlebars templating system.
  • URL Manipulation (Medium Severity): Prevents attackers from manipulating URLs rendered by Handlebars.

• Impact:

  • XSS: Significantly reduces the risk of XSS originating from Handlebars template rendering.
  • HTML Injection: Significantly reduces the risk.
  • URL Manipulation: Significantly reduces the risk.

• Currently Implemented:

  • Partially implemented. Helpers escapeAttribute and escapeURL are defined in helpers.js. Basic HTML escaping (double braces) is used in most templates.

• Missing Implementation:

  • escapeJS helper is missing. Inline JavaScript and <script> tag content within templates are not properly escaped.
  • safeString helper is not consistently used; some triple braces remain within templates.
  • No formal linting rules or code review processes enforce the consistent use of helpers within the templates.
  • No regular audits of Handlebars templates are performed.

Mitigation Strategy: Strict SafeString Usage and Centralized Sanitization (Handlebars-Specific)

• Description:

  1. Identify SafeString Uses: Locate all instances where Handlebars.SafeString or triple braces ({{{ }}}) are used within Handlebars templates.
  2. Centralized Sanitization Function: Create a single, well-tested, and robust HTML sanitization function. This function should be called within a Handlebars helper.
  3. safeString Helper: Create a Handlebars helper named safeString. This helper should:
     • Take the potentially unsafe HTML as input.
     • Call the centralized sanitization function.
     • Wrap the sanitized output in Handlebars.SafeString.
     • Return the Handlebars.SafeString object.
  4. Eliminate Direct Triple Braces: Replace all direct uses of triple braces within Handlebars templates with calls to the safeString helper. Never use triple braces directly.
  5. Code Reviews: Enforce strict code reviews that focus on any use of the safeString helper or any attempt to use Handlebars.SafeString directly.
  6. Auditing: Regularly audit the Handlebars templates for any new or modified uses of the safeString helper or triple braces.

• Threats Mitigated:

  • Cross-Site Scripting (XSS) (High Severity): Mitigates XSS by ensuring that only pre-sanitized HTML is rendered without escaping through the controlled use of Handlebars.SafeString within a dedicated helper.
  • HTML Injection (Medium Severity): Prevents the injection of malicious HTML via Handlebars.

• Impact:

  • XSS: Significantly reduces the risk, provided the sanitization function is robust and the safeString helper is used correctly.
  • HTML Injection: Significantly reduces the risk.

• Currently Implemented:

  • No centralized sanitization function exists.
  • SafeString is used sporadically (and incorrectly) within templates, without consistent sanitization. Triple braces are also used directly.

• Missing Implementation:

  • The entire strategy is largely missing. A centralized sanitization function needs to be created and integrated into a Handlebars helper. Existing uses of SafeString and triple braces within templates need to be refactored to use the new safeString helper.

Mitigation Strategy: Safe Helper Design (Preventing Prototype Pollution within Helpers)

• Description:

  1. Review Existing Helpers: Examine all custom Handlebars helpers for potential prototype pollution vulnerabilities.
  2. Safe Property Access: Within helpers, avoid using user-supplied data to directly access object properties using bracket notation (e.g., object[userData]).
  3. Object.hasOwn(): Instead, use Object.hasOwn(object, propertyName) to check if a property exists before accessing it within the helper. This is the primary Handlebars-specific mitigation.
  4. Input Sanitization within helper: Sanitize any data that comes from template.

• Threats Mitigated:

  • Prototype Pollution (Medium Severity): Prevents attackers from modifying the global Object.prototype through malicious input passed to Handlebars helpers.

• Impact:

  • Prototype Pollution: Reduces the risk of prototype pollution vulnerabilities originating from within Handlebars helpers.

• Currently Implemented:

  • Some helpers use bracket notation with user-supplied data without proper checks.

• Missing Implementation:

  • Helpers need to be reviewed and refactored to use Object.hasOwn() and avoid unsafe property access.

Mitigation Strategy: Avoid eval and new Function in Helpers

• Description:

  1. Code Reviews: Mandatory code reviews for all custom Handlebars helpers. Specifically check for the use of eval, new Function, or any other mechanism that dynamically executes code from strings within the helper code.
  2. Static Analysis: Integrate static analysis tools (e.g., ESLint with security plugins) into the development workflow, if possible, to scan helper code. Configure these tools to automatically detect and flag the use of eval and new Function.
  3. Documentation: Clearly document the prohibition of eval and new Function in coding guidelines specifically for Handlebars helper development.

• Threats Mitigated:

  • Arbitrary Code Execution (High Severity): Prevents attackers from injecting and executing arbitrary JavaScript code through malicious Handlebars helper implementations.

• Impact:

  • Arbitrary Code Execution: Eliminates the risk if the strategy is strictly enforced within the helper code.

• Currently Implemented:

  • Informal code reviews are performed, but there's no specific focus on eval or new Function within helpers.
  • No static analysis tools are currently used that target helper code.

• Missing Implementation:

  • Formal code review processes need to be established, with a specific focus on helper code.
  • Static analysis tools (if feasible) should be integrated to scan helper code.
  • Coding guidelines need to be updated to explicitly prohibit eval and new Function in helpers.

Mitigation Strategy: Regular Updates of Handlebars.js

• Description:

  1. Dependency Management: Use a dependency management tool (e.g., npm, yarn) to manage the Handlebars.js dependency.
  2. Automated Updates: Configure automated dependency updates (e.g., using Dependabot or similar tools) to receive notifications and pull requests for new versions of Handlebars.js.
  3. Testing: After updating Handlebars.js, thoroughly test the application, paying particular attention to the rendering of templates, to ensure that the update hasn't introduced any regressions or compatibility issues.
  4. Security Advisories: Subscribe to security advisories or release notifications for Handlebars.js.

• Threats Mitigated:

  • Known Vulnerabilities in Handlebars.js (Variable Severity): Addresses vulnerabilities that have been publicly disclosed and patched in newer versions of the Handlebars.js library itself.

• Impact:

  • Known Vulnerabilities: Reduces the risk of exploitation of known vulnerabilities in the Handlebars.js library.

• Currently Implemented:

  • npm is used for dependency management.
  • No automated update tools are configured.
  • Updates are performed manually and infrequently.

• Missing Implementation:

  • Automated update tools need to be configured.
  • A more regular update schedule needs to be established.