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Attack Surface Analysis for ultraq/thymeleaf-layout-dialect

Attack Surface: Template Injection via Layout/Fragment Names

  • Description: Attackers can inject malicious code into template names used in layout:decorate or layout:fragment attributes when these names are dynamically constructed from user-controlled input. This allows execution of arbitrary Thymeleaf expressions or inclusion of unintended templates.
  • Thymeleaf-Layout-Dialect Contribution: The core functionality of thymeleaf-layout-dialect relies on processing the values provided to layout:decorate and layout:fragment as template names. If these values are derived from unsanitized user input, the dialect directly facilitates template injection by using these potentially malicious names in Thymeleaf's template resolution process.
  • Example:
    • Scenario: An application uses user-provided theme to select a layout: <div layout:decorate="${'layouts/' + theme + '/main'}">.
    • Attack: An attacker provides theme as '${T(java.lang.Runtime).getRuntime().exec("malicious command")}'.
    • Result: The server executes the "malicious command" due to Thymeleaf expression evaluation within the layout:decorate attribute, facilitated by thymeleaf-layout-dialect's template processing.
  • Impact: Remote Code Execution (RCE), Information Disclosure, Cross-Site Scripting (XSS).
  • Risk Severity: Critical
  • Mitigation Strategies:
    • Strict Input Validation: Thoroughly validate and sanitize any user input that could influence layout or fragment names. Use whitelists of allowed characters or patterns.
    • Avoid Dynamic Template Name Construction: Prefer using predefined, static layout and fragment names. If dynamic selection is necessary, map user choices to a fixed, safe set of template names internally, instead of directly using user input in template paths.
    • Template Name Sanitization (If Dynamic Construction is Essential): If dynamic construction is unavoidable, sanitize user input to remove or escape any characters or expression syntax that could be interpreted as Thymeleaf expressions or path traversal sequences before using it in layout:decorate or layout:fragment.
    • Principle of Least Privilege: Run the application with minimal necessary permissions to limit the impact of potential RCE if template injection occurs.

Attack Surface: Path Traversal in Layout/Fragment Resolution (High Severity Aspect)

  • Description: Attackers can exploit vulnerabilities in template resolution logic to access files outside the intended template directories by manipulating paths used to locate layouts or fragments. While not directly a vulnerability in thymeleaf-layout-dialect, the dialect's usage can amplify the risk if template resolution is not properly secured.
  • Thymeleaf-Layout-Dialect Contribution: thymeleaf-layout-dialect triggers template resolution when processing layout:decorate and layout:fragment attributes. If the application's Thymeleaf template resolvers are misconfigured to allow broad path access, or if user input indirectly influences the resolution path, the dialect becomes the mechanism through which path traversal vulnerabilities can be exploited during layout/fragment inclusion.
  • Example:
    • Scenario: A template resolver is configured to search for templates starting from the web application's root directory, and a user-controlled parameter influences a part of the path used for resolution.
    • Attack: An attacker manipulates the user-controlled parameter to inject path traversal sequences like ../../ within the context of a layout:decorate or layout:fragment attribute, attempting to access files outside the intended template directory.
    • Result: Access to sensitive templates or files within the application's deployment directory, potentially leading to information disclosure or further exploitation.
  • Impact: Information Disclosure, potentially leading to further exploitation.
  • Risk Severity: High (when path traversal allows access to sensitive application files).
  • Mitigation Strategies:
    • Secure Template Resolver Configuration: Restrict Thymeleaf template resolvers to search only within specific, controlled template directories. Avoid resolvers that search in broad or user-controlled locations like the web application root.
    • Restrict Access to Template Directories (File System Level): Limit file system permissions to template directories, ensuring only necessary processes can access them.
    • Input Validation (Indirect Influence): Validate any user input that, even indirectly, could influence template resolution paths, even if it's not directly used in template names.
    • Regular Security Audits of Template Resolution: Regularly review template resolver configurations and template directory structures to identify and address potential path traversal vulnerabilities in the context of thymeleaf-layout-dialect usage.

Attack Surface: Dependency Vulnerabilities in thymeleaf-layout-dialect or its Dependencies (Potentially High/Critical)

  • Description: Vulnerabilities in thymeleaf-layout-dialect itself or, more commonly, in its transitive dependencies can introduce security risks. Exploiting these vulnerabilities can have severe consequences.
  • Thymeleaf-Layout-Dialect Contribution: By including thymeleaf-layout-dialect in an application, the application also includes all of the dialect's dependencies. If any of these dependencies have known high or critical severity vulnerabilities, the application becomes vulnerable by virtue of using the dialect.
  • Example:
    • Scenario: A transitive dependency of thymeleaf-layout-dialect contains a critical vulnerability that allows for Remote Code Execution.
    • Attack: An attacker exploits this vulnerability through interactions with the application that indirectly utilize the vulnerable dependency via thymeleaf-layout-dialect.
    • Result: Remote Code Execution, potentially full compromise of the server.
  • Impact: Remote Code Execution, Denial of Service, Information Disclosure, depending on the specific dependency vulnerability.
  • Risk Severity: Variable, potentially Critical (depending on the severity of the dependency vulnerability).
  • Mitigation Strategies:
    • Robust Dependency Management: Use a dependency management tool (like Maven or Gradle) to track and manage dependencies effectively.
    • Regular Dependency Updates: Keep thymeleaf-layout-dialect and all its dependencies updated to the latest versions, including security patches. Regularly check for and apply updates.
    • Vulnerability Scanning and Monitoring: Implement automated vulnerability scanning for dependencies using tools like OWASP Dependency-Check, Snyk, or similar. Continuously monitor for new vulnerability disclosures related to thymeleaf-layout-dialect and its dependencies.
    • Dependency Review and Justification: Periodically review the dependencies of thymeleaf-layout-dialect. Understand why each dependency is included and assess if there are alternative, less risky options if vulnerabilities are frequently found.

Attack Surface: Configuration Misconfigurations of Thymeleaf Template Resolvers (High Severity Aspect)

  • Description: Incorrectly configured Thymeleaf template resolvers, when used in conjunction with thymeleaf-layout-dialect, can create high-severity vulnerabilities. Allowing template resolution from overly broad locations or without proper restrictions can lead to security breaches.
  • Thymeleaf-Layout-Dialect Contribution: thymeleaf-layout-dialect relies entirely on Thymeleaf's template resolution mechanism to locate and process layouts and fragments. If template resolvers are misconfigured to allow access to sensitive areas or unintended template sources, thymeleaf-layout-dialect becomes the tool that inadvertently loads and processes these potentially malicious or sensitive templates.
  • Example:
    • Scenario: A template resolver is misconfigured to allow template resolution from a publicly writable directory within the web application.
    • Attack: An attacker uploads a malicious template to the writable directory and then crafts a request that uses thymeleaf-layout-dialect to include this malicious template as a layout or fragment.
    • Result: Remote Code Execution if the malicious template contains executable code, or information disclosure if it accesses sensitive data.
  • Impact: Information Disclosure, Path Traversal, potentially Template Injection and Remote Code Execution.
  • Risk Severity: High to Critical (depending on the nature of the misconfiguration and the attacker's ability to leverage it).
  • Mitigation Strategies:
    • Principle of Least Privilege for Template Resolution: Configure template resolvers with the most restrictive settings possible. Only allow template resolution from explicitly defined, secure template directories.
    • Secure Template Directory Structure and Permissions: Organize templates in a clear and secure directory structure. Ensure template directories are not publicly writable and have appropriate file system permissions.
    • Regular Configuration Review and Hardening: Periodically review Thymeleaf template resolver configurations to ensure they adhere to security best practices and are hardened against misconfiguration vulnerabilities.
    • Testing and Validation of Template Resolution Paths: Thoroughly test template resolution configurations to verify that they only resolve templates from intended locations and do not allow access to unauthorized areas or files.