mitigations.md

Mitigation Strategies Analysis for handlebars-lang/handlebars.js

Mitigation Strategy: Contextual Output Encoding (Handlebars' Default Escaping)

• Mitigation Strategy: Contextual Output Encoding (Leveraging Handlebars' Default Escaping)
• Description:
  1. Understand Handlebars' default escaping: Ensure developers understand that Handlebars.js automatically HTML-escapes content rendered using {{expression}}.
  2. Utilize default escaping consistently: Encourage developers to use {{expression}} for rendering most dynamic content, especially user-provided data, in HTML contexts.
  3. Avoid disabling default escaping unnecessarily: Do not disable Handlebars' default escaping unless there is a very specific and well-justified reason. If disabling is required, thoroughly document the reason and implement alternative, robust escaping mechanisms within Handlebars if possible, or very carefully outside.
  4. Educate developers on escaping contexts: Train developers to be aware of different output contexts (HTML, JavaScript, URL, CSS) and the appropriate escaping methods for each, and how Handlebars' default escaping relates to HTML context.
• List of Threats Mitigated:
  • Cross-Site Scripting (XSS) (High Severity): Prevents basic XSS attacks by escaping HTML entities, making it harder to inject malicious HTML or JavaScript when using Handlebars' default features.
• Impact:
  • Cross-Site Scripting (XSS): Medium risk reduction. Effective against many common XSS vectors in HTML context when developers correctly use Handlebars' default escaping, but not a complete solution and doesn't cover other contexts.
• Currently Implemented: [Describe here if Handlebars' default escaping is currently utilized and enforced in your project. For example: "Default escaping is enabled globally in Handlebars configuration. Code style guidelines encourage using {{expression}} for dynamic content." or "Default escaping is used in most templates, but there are inconsistencies." ]
• Missing Implementation: [Describe here where default escaping might not be consistently used or where developers might be bypassing it without proper justification. For example: "Need to review templates for instances where {{{unsafe}}} is used and ensure they are justified. Need to enforce code style guidelines to consistently use default escaping." or "Lack of developer training on the importance of default escaping and when to avoid bypassing it." ]

Mitigation Strategy: Avoid Dynamic Template Compilation with User Input

• Mitigation Strategy: Avoid Dynamic Template Compilation with User Input
• Description:
  1. Precompile templates during build time: Compile Handlebars templates into JavaScript functions during the application's build process using Handlebars' precompilation tools. This eliminates the need for runtime template compilation using Handlebars' compile function with potentially untrusted input.
  2. Store precompiled templates: Store precompiled templates as static assets or within the application code.
  3. Use precompiled templates in application code: Load and execute precompiled templates in your application code using Handlebars' runtime environment instead of compiling templates from strings at runtime with Handlebars' compile function.
  4. Restrict dynamic compilation to trusted sources (if absolutely necessary): If dynamic compilation using Handlebars' compile function is unavoidable, strictly control the source of the template string and ensure user input is never directly part of the template string passed to Handlebars' compile function.
• List of Threats Mitigated:
  • Template Injection (High Severity): Significantly reduces or eliminates template injection risk by preventing attackers from controlling the template source code that is passed to Handlebars for compilation.
  • Denial of Service (DoS) (Medium Severity): Reduces potential DoS risks associated with complex or malicious templates being dynamically compiled by Handlebars at runtime.
• Impact:
  • Template Injection: High risk reduction. Effectively eliminates the primary attack vector for template injection related to Handlebars' compilation process.
  • Denial of Service (DoS): Low to Medium risk reduction. Reduces DoS risk related to template compilation within Handlebars, but other DoS vectors might still exist.
• Currently Implemented: [Describe here if templates are precompiled in your project using Handlebars' precompilation tools. For example: "Templates are precompiled using handlebars-cli during the build process and included in the application bundle." or "Dynamic template compilation using Handlebars' compile function is used in some parts of the application." ]
• Missing Implementation: [Describe here if dynamic template compilation using Handlebars' compile function is still used and where precompilation should be implemented. For example: "Dynamic template compilation using Handlebars' compile function is still used in the admin panel for generating reports. Need to migrate to precompiled templates for report generation." or "Need to implement a build process that includes template precompilation using Handlebars' tools." ]

Mitigation Strategy: Careful Use of Triple Braces {{{unsafe}}}

• Mitigation Strategy: Careful Use of Triple Braces {{{unsafe}}}
• Description:
  1. Establish a strict policy for {{{unsafe}}} usage: Define a policy that strongly discourages the use of triple braces {{{unsafe}}} in Handlebars templates and requires explicit justification and approval for each instance.
  2. Thoroughly review all {{{unsafe}}} usages: Conduct mandatory code reviews for any code that uses {{{unsafe}}} in Handlebars templates. Ensure that the data being rendered with triple braces is from a trusted source and is already securely escaped before being passed to Handlebars. Document the justification for each usage.
  3. Consider alternative approaches: Before using {{{unsafe}}} explore if there are alternative ways to achieve the desired output using Handlebars helpers or other safer techniques within Handlebars that do not bypass default escaping.
  4. Regularly audit {{{unsafe}}} usage: Periodically audit the codebase to identify and review all instances of {{{unsafe}}} in Handlebars templates to ensure they are still justified and secure.
• List of Threats Mitigated:
  • Cross-Site Scripting (XSS) (High Severity): Directly prevents XSS vulnerabilities that arise from bypassing Handlebars' default escaping with {{{unsafe}}} when rendering untrusted or unsanitized data within Handlebars templates.
• Impact:
  • Cross-Site Scripting (XSS): High risk reduction. Effectively eliminates XSS risks associated with misuse of {{{unsafe}}} if enforced rigorously in Handlebars template development.
• Currently Implemented: [Describe here if there is a policy or process in place for managing {{{unsafe}}} usage in Handlebars templates. For example: "Code style guidelines discourage {{{unsafe}}} usage in Handlebars templates. Code reviews specifically check for and question {{{unsafe}}} usage." or "No specific policy for {{{unsafe}}} usage in Handlebars templates. Developers are generally aware of its implications." ]
• Missing Implementation: [Describe here if a stricter policy or process is needed for managing {{{unsafe}}} in Handlebars templates. For example: "Need to formalize a policy that requires justification and approval for {{{unsafe}}} usage in Handlebars templates. Need to implement automated checks to flag {{{unsafe}}} usage during code reviews." or "Lack of clear guidelines and enforcement regarding {{{unsafe}}} usage in Handlebars templates." ]

Mitigation Strategy: Context-Aware Escaping Beyond HTML

• Mitigation Strategy: Context-Aware Escaping Beyond HTML
• Description:
  1. Identify different output contexts: Analyze your templates to identify contexts beyond HTML where dynamic data is rendered (e.g., JavaScript strings, URLs, CSS, JSON) within Handlebars templates.
  2. Understand context-specific escaping requirements: Learn the appropriate escaping methods for each context (e.g., JavaScript escaping, URL encoding, CSS escaping, JSON stringification).
  3. Utilize Handlebars helpers for context-specific escaping: Create or use existing Handlebars helpers that perform context-aware escaping within Handlebars. For example, create helpers for JavaScript escaping, URL encoding, etc.
  4. Apply context-specific escaping in templates: Use the appropriate context-aware helpers when rendering data in non-HTML contexts within your Handlebars templates.
  5. Educate developers on context-aware escaping: Train developers on the importance of context-aware escaping and how to use the provided helpers correctly within Handlebars template development.
• List of Threats Mitigated:
  • Cross-Site Scripting (XSS) (High Severity): Prevents XSS vulnerabilities that can occur when data is improperly escaped in non-HTML contexts (e.g., JavaScript injection, URL manipulation) within Handlebars templates.
• Impact:
  • Cross-Site Scripting (XSS): High risk reduction. Effectively mitigates XSS risks in various output contexts beyond HTML when using Handlebars helpers for escaping.
• Currently Implemented: [Describe here if context-aware escaping is implemented in your project using Handlebars helpers. For example: "Custom Handlebars helpers for JavaScript escaping and URL encoding are implemented and used in templates where needed." or "Context-aware escaping is not consistently applied within Handlebars templates. Developers are expected to manually escape data in non-HTML contexts outside of Handlebars." ]
• Missing Implementation: [Describe here if context-aware escaping needs to be implemented or improved using Handlebars helpers. For example: "Need to develop and implement Handlebars helpers for various context-specific escaping needs (JavaScript, URL, CSS, etc.). Need to provide developer training on context-aware escaping and helper usage within Handlebars templates." or "Lack of automated checks to ensure context-aware escaping is applied correctly in Handlebars templates." ]

Mitigation Strategy: Principle of Least Privilege in Templates

• Mitigation Strategy: Principle of Least Privilege in Templates
• Description:
  1. Minimize data passed to templates: Only pass the absolutely necessary data to Handlebars templates. Avoid passing entire objects or large datasets if only specific properties are needed when providing data to Handlebars templates.
  2. Restrict helper function capabilities: If using custom Handlebars helpers, ensure they operate with the principle of least privilege. Helpers should only have access to the data and functionalities they strictly require within the Handlebars helper context. Avoid creating overly powerful helpers that could be misused within Handlebars.
  3. Review template data access: Regularly review the data being passed to templates and the capabilities of helper functions to ensure they adhere to the principle of least privilege in Handlebars template and helper design.
  4. Avoid exposing sensitive data unnecessarily: Do not expose sensitive data (e.g., API keys, database credentials, user secrets) directly within templates or through helper functions in Handlebars.
• List of Threats Mitigated:
  • Information Disclosure (Medium to High Severity): Reduces the risk of accidentally exposing sensitive data if templates are compromised or if vulnerabilities exist in helper functions within Handlebars.
  • Template Injection (Medium Severity): Limits the potential damage from template injection by restricting the attacker's access to sensitive data and functionalities within the template context provided to Handlebars.
• Impact:
  • Information Disclosure: Medium risk reduction. Reduces the potential for information disclosure if other vulnerabilities are exploited related to Handlebars data handling.
  • Template Injection: Low to Medium risk reduction. Limits the attacker's capabilities after successful template injection within the Handlebars context.
• Currently Implemented: [Describe here if the principle of least privilege is considered in template design and data handling in your project specifically for Handlebars. For example: "Developers are instructed to pass only necessary data to Handlebars templates. Code reviews include checks for data minimization in templates." or "Principle of least privilege is not explicitly considered in Handlebars template design." ]
• Missing Implementation: [Describe here if the principle of least privilege needs to be more actively implemented in the context of Handlebars. For example: "Need to implement stricter guidelines for data passing to Handlebars templates and enforce them through code reviews. Need to review existing templates and helper functions to minimize data exposure and restrict helper capabilities within Handlebars." or "Lack of developer awareness about the principle of least privilege in Handlebars template design." ]

Mitigation Strategy: Template Complexity Limits

• Mitigation Strategy: Template Complexity Limits
• Description:
  1. Establish template complexity metrics: Define metrics to measure Handlebars template complexity, such as nesting depth, template size, or number of expressions within Handlebars templates.
  2. Set reasonable complexity limits: Based on performance testing and security considerations, set reasonable limits for Handlebars template complexity metrics.
  3. Implement automated complexity checks: Develop or use tools to automatically check Handlebars templates against the defined complexity limits during development or build processes.
  4. Enforce complexity limits in code reviews: Include Handlebars template complexity as a factor in code reviews. Reject templates that exceed the defined limits.
  5. Monitor template rendering performance: Continuously monitor the performance of Handlebars template rendering, especially for complex templates or templates handling user input.
• List of Threats Mitigated:
  • Denial of Service (DoS) (Medium Severity): Reduces the risk of DoS attacks caused by excessively complex or deeply nested Handlebars templates consuming excessive server resources during Handlebars rendering.
• Impact:
  • Denial of Service (DoS): Medium risk reduction. Limits the potential for DoS attacks related to Handlebars template complexity.
• Currently Implemented: [Describe here if Handlebars template complexity limits are in place and how they are enforced. For example: "Handlebars template complexity limits are not formally defined or enforced. Developers are generally encouraged to keep templates simple." or "Basic Handlebars template complexity guidelines exist, but no automated checks are in place." ]
• Missing Implementation: [Describe here if Handlebars template complexity limits need to be implemented. For example: "Need to define and implement formal Handlebars template complexity limits. Need to develop or find tools to automatically check Handlebars template complexity. Need to integrate complexity checks into the build process and code reviews." or "Lack of awareness or prioritization of Handlebars template complexity as a potential DoS risk." ]