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Threat Model Analysis for cucumber/cucumber-ruby

Threat: Arbitrary Code Execution via Step Definition Injection

  • Description: An attacker crafts a malicious feature file or scenario outline example. This input is processed by Cucumber's Gherkin parser (gherkin gem, a direct dependency) and then used to match and execute step definitions. The attacker exploits weaknesses in the regular expression matching logic within Cucumber::RbSupport::RbStepDefinition#regexp_source_and_comment or in how parameter type transformations are handled (Cucumber::ParameterTypeRegistry) to inject and execute arbitrary Ruby code within the step definition. The attacker's goal is to gain control of the system running the tests.
    • Impact: Complete system compromise (Remote Code Execution - RCE), data exfiltration, privilege escalation, denial of service.
    • Affected Component:
      • Cucumber::RbSupport::RbStepDefinition#regexp_source_and_comment (regular expression handling in step definitions).
      • Cucumber::ParameterTypeRegistry (custom parameter type transformations).
      • Step definition methods (the Ruby code within Given, When, Then blocks).
      • gherkin gem (parsing of feature files).
    • Risk Severity: Critical
    • Mitigation Strategies:
      • Strict Input Validation: Implement rigorous input validation and sanitization for all data extracted from feature files before it reaches the step definition matching logic. Use whitelisting.
      • Secure Regular Expressions: Use anchored regular expressions (^...$) in step definitions. Avoid overly permissive regex patterns.
      • Avoid eval, system, exec, backticks: Never use these functions with unsanitized input from feature files.
      • Parameterized Steps: Prefer Cucumber's built-in parameterization (data tables, scenario outlines).
      • Custom Parameter Types (with Validation): If using custom parameter types, ensure they include robust, internal validation logic that cannot be bypassed by the attacker.
      • Code Reviews: Mandatory code reviews for all step definitions, with a security focus.

Threat: Sensitive Data Exposure in Feature Files/Support Code (Direct Cucumber Usage)

  • Description: Although seemingly a general issue, the way Cucumber is used directly contributes to this threat. Developers, misunderstanding Cucumber's purpose or due to convenience, hardcode sensitive information (passwords, API keys) directly within feature files (.feature files, parsed by the gherkin gem) or within the Ruby code loaded by Cucumber to support test execution (environment files, helper modules, step definitions). This data is then exposed if the repository is compromised.
    • Impact: Data breach, unauthorized access to systems and services, reputational damage.
    • Affected Component:
      • Feature files (.feature files, parsed by the gherkin gem).
      • Environment files (features/support/env.rb, loaded by Cucumber::Runtime).
      • Custom helper modules loaded by Cucumber.
      • Step definition files.
    • Risk Severity: High
    • Mitigation Strategies:
      • Environment Variables: Store sensitive data in environment variables, never in files processed by Cucumber.
      • Secrets Management: Use a dedicated secrets management solution.
      • .gitignore: Ensure sensitive files are excluded from version control.
      • Secure Repository Access: Implement strong access controls.
      • Regular Audits: Audit feature files and support code specifically for sensitive data. This is a Cucumber-specific audit, not a general code audit.

Threat: Malicious Cucumber Plugin

  • Description: An attacker publishes a malicious Cucumber plugin (or compromises a legitimate one) as a Ruby gem. This plugin contains harmful code that is executed when Cucumber loads and initializes the plugin via Cucumber::Runtime#load_programming_language. The attacker's code can then perform actions with the privileges of the user running Cucumber.
    • Impact: Remote Code Execution (RCE), data exfiltration, compromise of the testing environment.
    • Affected Component:
      • Third-party Cucumber plugins (gems extending Cucumber).
      • Cucumber::Runtime#load_programming_language (plugin loading mechanism).
    • Risk Severity: High
    • Mitigation Strategies:
      • Use Trusted Sources: Only install plugins from reputable sources (e.g., RubyGems.org, with careful vetting).
      • Verify Plugin Integrity: Check for digital signatures or checksums.
      • Code Audits: Audit the source code of less-known plugins before use.
      • Regular Updates: Keep plugins updated.
      • Principle of Least Privilege: Run Cucumber with minimal privileges.

Threat: Dependency Vulnerability Exploitation (Direct Dependencies)

  • Description: An attacker exploits a known vulnerability in cucumber-ruby itself, or in one of its direct and essential dependencies like the gherkin gem (used for parsing feature files) or cucumber-core (containing core execution logic). This is distinct from vulnerabilities in indirect dependencies or gems used only within step definitions. The vulnerability allows for RCE, information disclosure, or DoS, directly impacting Cucumber's operation.
    • Impact: Varies (RCE, information disclosure, DoS), but directly affects Cucumber's core functionality.
    • Affected Component:
      • cucumber-ruby gem.
      • gherkin gem (feature file parsing).
      • cucumber-core gem (core execution logic).
    • Risk Severity: High (potentially Critical, depending on the specific vulnerability)
    • Mitigation Strategies:
      • Dependency Management: Use bundler to manage dependencies.
      • Vulnerability Scanning: Use bundler-audit or Snyk, focusing on cucumber-ruby and its direct dependencies.
      • Regular Updates: Keep cucumber-ruby, gherkin, and cucumber-core updated.
      • Prompt Patching: Apply security patches immediately.