threat-modeling.md

Threat Model Analysis for swiftgen/swiftgen

Threat: Malicious Template Injection

• Description: An attacker gains control of a SwiftGen template file (e.g., a .stencil file). They could achieve this through several means:

  • Directly modifying a template file if they have write access to the project's repository.
  • Tricking a developer into downloading and using a malicious template from an untrusted source.
  • Exploiting a vulnerability in a dependency management system to inject a malicious template. The attacker modifies the template to include malicious Swift code. This code will be executed during the build process when SwiftGen generates the output files. The malicious code could do anything the build process has permissions to do, including:
  • Stealing secrets (API keys, credentials) from the build environment.
  • Injecting backdoors into the application.
  • Modifying other source code files.
  • Exfiltrating data from the build machine.

• Impact:

  • Code Execution: Arbitrary code execution within the context of the build process.
  • Data Breach: Exposure of sensitive information (secrets, source code).
  • Application Compromise: Injection of malicious code into the final application, potentially affecting all users.
  • Reputation Damage: Loss of trust in the application and the development team.

• Affected SwiftGen Component:

  • Template engine (Stencil).
  • Custom template files (.stencil).
  • The swiftgen run command and its subcommands that process templates (e.g., swiftgen run config, swiftgen run xcassets, etc.).

• Risk Severity: Critical

• Mitigation Strategies:

  • Treat Templates as Source Code: Store templates in version control (e.g., Git).
  • Mandatory Code Review: Require code review for all changes to SwiftGen templates.
  • Trusted Sources Only: Avoid downloading templates from untrusted sources. Prefer built-in templates or those from well-known, reputable sources.
  • Input Validation (Indirect): Validate any data used within templates that originates from untrusted sources (e.g., filenames, string keys). This is done within the application code, not within SwiftGen itself, but it prevents malicious input from triggering unexpected template behavior.
  • Least Privilege (Build Environment): Run SwiftGen with the minimum necessary permissions. Avoid running it as root or with administrator privileges.
  • Sandboxing (If Possible): If the build environment supports it, run SwiftGen in a sandboxed environment to limit its access to the system.
  • Regular Audits: Periodically review custom templates for suspicious code.
  • Avoid External Template Dependencies: Minimize the use of external template dependencies to reduce the attack surface.

Threat: Compromised SwiftGen Binary

• Description: An attacker replaces the legitimate SwiftGen executable with a malicious version. This could happen if:

  • The attacker gains access to the build server and replaces the binary.
  • The attacker compromises the package manager used to install SwiftGen (e.g., Homebrew).
  • A developer is tricked into downloading and running a malicious binary disguised as SwiftGen. The malicious binary could then perform any action on the build system, including all the impacts listed for template injection, and potentially more.

• Impact:

  • Complete System Compromise: The attacker could gain full control of the build system.
  • Data Breach: Access to all data on the build system, including source code, secrets, and potentially other sensitive information.
  • Application Compromise: Injection of malicious code into the application.

• Affected SwiftGen Component:

  • The SwiftGen executable itself (swiftgen).

• Risk Severity: Critical

• Mitigation Strategies:

  • Secure Installation: Install SwiftGen from trusted sources (e.g., official package managers like Homebrew).
  • Checksum Verification: If checksums are provided, verify them after downloading SwiftGen.
  • Regular Updates: Keep SwiftGen up-to-date to benefit from security patches.
  • Binary Verification (Ideal, but difficult): Ideally, verify the digital signature of the SwiftGen binary before execution. This is often not practical.
  • Secure Build Server: Protect the build server from unauthorized access.

Threat: Accidental Exposure of Sensitive Data

• Description: A developer accidentally includes sensitive information (e.g., API keys, passwords, database credentials) directly within a SwiftGen template or within a resource file that SwiftGen processes (e.g., a strings file). This information is then included in the generated code, potentially exposing it to attackers.

• Impact:

  • Data Breach: Exposure of sensitive information.
  • Credential Compromise: Attackers could use the exposed credentials to access other systems.

• Affected SwiftGen Component:

  • Template files (.stencil).
  • Resource files processed by SwiftGen (e.g., .xcassets, .strings, .json, .plist).
  • Generated Swift code.

• Risk Severity: High

• Mitigation Strategies:

  • Never Hardcode Secrets: Absolutely avoid hardcoding secrets in templates or resource files.
  • Use Secret Management Tools: Use appropriate mechanisms for managing secrets (e.g., environment variables, secure key stores, configuration services).
  • Code Review: Carefully review templates and resource files for any potential exposure of sensitive data.
  • Automated Scanning: Use tools to scan templates and resource files for potential secrets (e.g., git-secrets, trufflehog).