Skip to content

Latest commit

 

History

History
147 lines (118 loc) · 18.2 KB

sec-design-deep-analysis.md

File metadata and controls

147 lines (118 loc) · 18.2 KB

Deep Security Analysis of Sourcery

1. Objective, Scope, and Methodology

Objective: The objective of this deep security analysis is to thoroughly examine the Sourcery codebase, its dependencies, and its operational context to identify potential security vulnerabilities, weaknesses, and areas for improvement. The analysis focuses on the key components identified in the security design review, including the Sourcery CLI, Sourcery Engine, Stencil template engine, SwiftSyntax library, and file system interactions. The goal is to provide actionable recommendations to enhance Sourcery's security posture and minimize the risk of introducing vulnerabilities into projects that utilize it.

Scope:

  • Codebase Analysis: Examination of the Sourcery source code (Swift) for potential vulnerabilities, including but not limited to injection flaws, insecure file handling, and logic errors.
  • Dependency Analysis: Assessment of the security posture of Sourcery's direct and transitive dependencies, focusing on known vulnerabilities and update frequency.
  • Template Engine (Stencil) Security: Deep dive into the Stencil template engine's security features and potential risks related to template injection.
  • SwiftSyntax Usage: Analysis of how Sourcery utilizes SwiftSyntax to parse and manipulate Swift code, looking for potential vulnerabilities related to malformed input or unexpected behavior.
  • File System Interactions: Review of how Sourcery interacts with the file system, including reading input files, writing output files, and handling temporary files.
  • Build and Deployment Process: Evaluation of the security aspects of Sourcery's build and deployment process, including code signing and artifact integrity.
  • Configuration Handling: Examination of how Sourcery handles configuration files and command-line arguments.

Methodology:

  1. Static Code Analysis: Manual code review supplemented by automated static analysis tools (SAST) to identify potential vulnerabilities in the Sourcery codebase. Specific tools will be recommended.
  2. Dependency Scanning: Use of Software Composition Analysis (SCA) tools to identify known vulnerabilities in Sourcery's dependencies.
  3. Dynamic Analysis (Fuzzing): Employ fuzz testing techniques to identify potential crashes, unexpected behavior, or vulnerabilities caused by malformed input.
  4. Template Engine Security Review: Detailed examination of the Stencil template engine's documentation and source code to understand its security mechanisms and potential weaknesses.
  5. Architecture and Data Flow Review: Analysis of the C4 diagrams and component descriptions to understand the overall architecture and data flow, identifying potential attack vectors.
  6. Threat Modeling: Based on the identified components and data flows, develop a threat model to identify potential threats and attack scenarios.
  7. Security Design Review Document Analysis: Leverage the provided security design review document to understand existing security controls, accepted risks, and security requirements.

2. Security Implications of Key Components

  • Sourcery CLI:

    • Security Implications: The CLI is the primary entry point for users. Vulnerabilities here could allow attackers to control Sourcery's behavior. The main concern is improper handling of command-line arguments and configuration files, potentially leading to arbitrary file reads or writes, or even code execution if an attacker can influence the arguments passed to the template engine.
    • Specific Concerns: Argument injection, path traversal vulnerabilities if file paths are constructed from user-provided arguments without proper sanitization.
    • Recommendations:
      • Use a robust command-line argument parsing library that provides built-in validation and sanitization. Avoid manual parsing of arguments.
      • Strictly validate and sanitize all file paths provided as arguments, ensuring they are within expected directories and do not contain malicious characters (e.g., "../").
      • Implement a principle of least privilege: Sourcery should only have the necessary file system permissions to perform its tasks.

  • Sourcery Engine:

    • Security Implications: This is the core of the application, where the most critical security vulnerabilities could reside. It handles parsing Swift code, processing templates, and generating output. Vulnerabilities here could lead to arbitrary code execution within the context of the generated code.
    • Specific Concerns: Template injection, vulnerabilities in Swift parsing (via SwiftSyntax), insecure handling of temporary files, logic errors leading to incorrect code generation.
    • Recommendations:
      • Template Injection Mitigation: This is the most critical area. Thoroughly review all uses of the Stencil template engine. Ensure that user-provided data is properly escaped and sanitized before being passed to the template engine. Consider using Stencil's autoescape feature and context-specific filters. Provide clear documentation and examples on how to write secure templates. Strongly consider adding a "safe mode" that disables potentially dangerous template features (e.g., custom filters or tags that could execute arbitrary code).
      • SwiftSyntax Security: Regularly update SwiftSyntax to the latest version to benefit from security fixes. Monitor for any reported vulnerabilities in SwiftSyntax and apply patches promptly. Implement fuzz testing specifically targeting the Swift parsing logic to identify potential crashes or vulnerabilities.
      • Temporary File Handling: If temporary files are used, ensure they are created in secure temporary directories with appropriate permissions. Use unique, unpredictable filenames to prevent race conditions or information disclosure. Delete temporary files as soon as they are no longer needed.
      • Error Handling: Implement robust error handling to prevent unexpected crashes or information disclosure. Avoid exposing internal implementation details in error messages.

  • Stencil (Template Engine):

    • Security Implications: Stencil is a third-party library, so vulnerabilities in Stencil could directly impact Sourcery. The primary concern is template injection, where an attacker can inject malicious code into a template, which is then executed by Sourcery.
    • Specific Concerns: Known vulnerabilities in Stencil, improper use of Stencil's features (e.g., custom filters or tags), insufficient escaping of user-provided data.
    • Recommendations:
      • Regular Updates: Keep Stencil updated to the latest version to address known vulnerabilities.
      • Security Audits: Periodically review the Stencil codebase and its security documentation for potential issues.
      • Safe by Default: Configure Stencil to be as secure as possible by default. Enable autoescape and consider disabling potentially dangerous features if they are not essential.
      • Context-Specific Escaping: Use the appropriate escaping filters for the context in which data is being used (e.g., HTML escaping, JavaScript escaping).
      • Input Validation: Validate any user-provided data that is used within templates, even if it's expected to be "safe."

  • SwiftSyntax:

    • Security Implications: SwiftSyntax is a critical dependency, as it's responsible for parsing Swift code. Vulnerabilities in SwiftSyntax could allow attackers to craft malicious Swift code that causes Sourcery to crash, behave unexpectedly, or even execute arbitrary code.
    • Specific Concerns: Bugs in SwiftSyntax's parsing logic, vulnerabilities related to handling malformed or excessively large input files.
    • Recommendations:
      • Regular Updates: Keep SwiftSyntax updated to the latest version.
      • Vulnerability Monitoring: Monitor for any reported vulnerabilities in SwiftSyntax.
      • Fuzz Testing: Implement fuzz testing to identify potential vulnerabilities in Sourcery's use of SwiftSyntax.
      • Input Size Limits: Implement limits on the size of input files to prevent denial-of-service attacks.

  • File System Interactions:

    • Security Implications: Sourcery reads and writes files, so vulnerabilities in file handling could lead to arbitrary file reads or writes, information disclosure, or denial-of-service.
    • Specific Concerns: Path traversal vulnerabilities, insecure temporary file handling, race conditions, improper file permissions.
    • Recommendations:
      • Path Sanitization: Strictly validate and sanitize all file paths, ensuring they are within expected directories and do not contain malicious characters.
      • Secure Temporary Files: Use secure temporary directories and unique, unpredictable filenames.
      • Least Privilege: Sourcery should only have the necessary file system permissions.
      • Atomic Operations: Use atomic file operations where possible to prevent race conditions.

3. Architecture, Components, and Data Flow (Inferred)

The C4 diagrams and component descriptions provide a good overview of Sourcery's architecture. The key data flows are:

  1. Developer -> Sourcery CLI: The developer provides command-line arguments and configuration to the CLI.
  2. Sourcery CLI -> Sourcery Engine: The CLI passes parsed arguments and configuration to the engine.
  3. Sourcery Engine <-> File System: The engine reads Swift source files, template files, and configuration files from the file system. It writes generated Swift code to the file system.
  4. Sourcery Engine -> Stencil: The engine passes data and template content to Stencil for processing.
  5. Sourcery Engine -> SwiftSyntax: The engine uses SwiftSyntax to parse Swift source code.

Potential Attack Vectors:

  • Attacker-controlled templates: If an attacker can modify or inject a malicious template, they can potentially execute arbitrary code within the context of the generated code.
  • Attacker-controlled Swift source files: While less likely, a maliciously crafted Swift source file could exploit vulnerabilities in SwiftSyntax or Sourcery's parsing logic.
  • Attacker-controlled command-line arguments or configuration: An attacker could potentially inject malicious arguments or configuration settings to influence Sourcery's behavior.
  • Vulnerabilities in dependencies (Stencil, SwiftSyntax): Exploiting known vulnerabilities in these libraries could compromise Sourcery.

4. Tailored Security Considerations

  • Template Injection is Paramount: Given Sourcery's core function of code generation based on templates, mitigating template injection is the highest priority. This requires a multi-layered approach:

    • Strict Input Validation: Validate all user-provided data that is used within templates.
    • Proper Escaping: Use Stencil's autoescape feature and context-specific escaping filters.
    • Safe Mode: Consider a "safe mode" that disables potentially dangerous template features.
    • Security Documentation: Provide clear guidance on writing secure templates.
    • Regular Audits: Periodically review the use of Stencil and the handling of template data.

  • Dependency Management is Crucial: Sourcery relies on external libraries (Stencil, SwiftSyntax, and others). Vulnerabilities in these libraries can directly impact Sourcery's security.

    • SCA Tooling: Use an SCA tool (e.g., OWASP Dependency-Check, Snyk) to identify known vulnerabilities in dependencies.
    • Regular Updates: Keep dependencies updated to the latest versions.
    • Vulnerability Monitoring: Monitor for security advisories related to dependencies.

  • Fuzz Testing is Essential: Fuzz testing can help identify unexpected behavior and vulnerabilities caused by malformed input.

    • Target Swift Parsing: Fuzz the Swift parsing logic (using SwiftSyntax) with malformed Swift code.
    • Target Template Processing: Fuzz the template processing logic with malformed templates and data.
    • Target CLI Arguments: Fuzz the command-line argument parsing.

  • Secure File Handling is Non-Negotiable: Sourcery interacts extensively with the file system.

    • Path Traversal Prevention: Strictly validate and sanitize all file paths.
    • Secure Temporary Files: Use secure temporary directories and unique filenames.
    • Least Privilege: Run Sourcery with the minimum necessary file system permissions.

  • Code Signing (Recommended): While not currently implemented, code signing the released binaries would provide an additional layer of security, ensuring that users are running authentic, unmodified code.

5. Actionable Mitigation Strategies

Threat Mitigation Strategy Priority
Template Injection - Implement strict input validation for all data used in templates.
- Use Stencil's autoescape feature and context-specific escaping filters.
- Consider a "safe mode" that disables potentially dangerous template features.
- Provide clear documentation on writing secure templates.
- Regularly audit template handling.		 High
Vulnerabilities in Dependencies - Use an SCA tool (e.g., OWASP Dependency-Check, Snyk) to identify known vulnerabilities.
- Keep dependencies updated to the latest versions.
- Monitor for security advisories related to dependencies.		 High
Malformed Input (Swift Code, Templates) - Implement fuzz testing targeting Swift parsing, template processing, and CLI argument parsing.
- Implement input size limits.		 High
Insecure File Handling - Strictly validate and sanitize all file paths.
- Use secure temporary directories and unique filenames.
- Run Sourcery with the minimum necessary file system permissions.
- Use atomic file operations where possible.		 High
Arbitrary Code Execution (via Dependencies) - Keep dependencies updated.
- Monitor for security advisories.
- Consider sandboxing or containerization (though this may be impractical for a CLI tool).		 Medium
Lack of Code Signing - Implement code signing for released binaries. Medium
Logic Errors in Code Generation - Maintain a comprehensive test suite (unit and integration tests).
- Perform thorough code reviews.
- Use static analysis tools (SAST).		 Medium
Denial of Service (DoS) - Implement input size limits.
- Implement resource limits (e.g., memory, CPU time) if possible.		 Low

Specific Tool Recommendations:

  • SAST:
    • SwiftLint: (Already in use) Continue using SwiftLint for code style and basic security checks.
    • SonarQube: A comprehensive static analysis platform that supports Swift.
    • Semgrep: A fast and flexible static analysis tool that can be customized with rules specific to Sourcery.
  • SCA:
    • OWASP Dependency-Check: A free and open-source SCA tool.
    • Snyk: A commercial SCA tool with a free tier.
    • GitHub Dependabot: Automated dependency updates and security alerts (integrated with GitHub).
  • Fuzzing:
    • libFuzzer: A coverage-guided fuzzer that can be integrated with Swift projects.
    • SwiftFuzz: A Swift-specific fuzzing library.
    • AFL (American Fuzzy Lop): A general-purpose fuzzer that can be used with some effort.

Conclusion:

Sourcery is a powerful tool with the potential to significantly improve developer productivity. However, its code generation capabilities introduce inherent security risks, primarily related to template injection. By implementing the recommended mitigation strategies, focusing on secure template handling, dependency management, fuzz testing, and secure file handling, Sourcery's security posture can be significantly enhanced, minimizing the risk of introducing vulnerabilities into projects that utilize it. Continuous security monitoring, regular updates, and a proactive approach to addressing vulnerabilities are essential for maintaining Sourcery's security over time.