attack-surface.md

Attack Surface Analysis for minimistjs/minimist

Attack Surface: Prototype Pollution

Description: An attacker can manipulate the prototype of JavaScript objects by injecting properties into the __proto__ object via command-line arguments. This can lead to unexpected application behavior, security bypasses, or even remote code execution.

• How minimist Contributes: minimist's parsing logic, specifically its handling of double underscores (__proto__) in command-line arguments, allows these arguments to directly modify the prototype chain. This is a direct vulnerability stemming from minimist's design.
• Example:
  • An attacker provides the command-line argument: --__proto__.isAdmin=true
  • If the application later checks Object.prototype.isAdmin or any object's isAdmin property inherited from the prototype, it will incorrectly evaluate to true, potentially bypassing authentication or authorization checks.
• Impact:
  • Denial of Service (DoS)
  • Security Bypass
  • Remote Code Execution (RCE) (in certain scenarios)
• Risk Severity: Critical to High (depending on application usage and exploitability)
• Mitigation Strategies:
  • Upgrade minimist: Check for and apply updates to minimist as vulnerabilities are patched in newer versions. While direct fixes in minimist for prototype pollution might be limited due to design choices, staying updated is generally good practice.
  • Input Validation and Sanitization: Thoroughly validate and sanitize all command-line arguments after parsing by minimist. Crucially, avoid using parsed arguments as keys to set object properties, especially when dealing with user input. Treat minimist output as untrusted.
  • Avoid Prototype Manipulation: Refrain from using user-controlled input to directly set properties on objects, particularly using bracket notation or accessing __proto__. Use safer object manipulation techniques that do not involve directly setting properties based on user-provided keys.
  • Object Freezing: If feasible, freeze critical objects or prototypes to prevent modification.

Attack Surface: Unexpected Argument Parsing Behavior (Leading to Logic Flaws & Input Validation Bypass)

Description: minimist's argument parsing might behave in ways that are not immediately obvious or expected by developers. This can lead to logic flaws and vulnerabilities if developers make incorrect assumptions about how arguments are processed, especially concerning input validation.

• How minimist Contributes: minimist's specific rules for handling boolean flags, string/number coercion, array arguments, and special characters can lead to unexpected parsing outcomes if not fully understood and accounted for in application logic. This unexpected behavior is a direct consequence of minimist's parsing implementation.
• Example:
  • Application expects --id to always be an integer. If an attacker provides --id "NaN", minimist might parse it as a string "NaN". If the application's input validation relies on minimist implicitly converting to a number and doesn't explicitly check for NaN or non-numeric strings, it could bypass validation logic.
  • Boolean flags like --debug are implicitly set to true. If application logic incorrectly assumes --debug false will disable debugging, but minimist only recognizes --debug (or --debug=true), it can lead to unintended debugging features being enabled in production.
• Impact:
  • Logic Flaws
  • Input Validation Bypass
  • Information Disclosure (potentially, if logic flaws expose sensitive data or enable unintended features)
• Risk Severity: Medium to High (depending on the complexity of application logic and reliance on specific parsing behavior for security-critical features. Can be High if input validation is bypassed leading to significant security issues).
• Mitigation Strategies:
  • Thorough Testing: Extensively test argument parsing with various inputs, including edge cases, special characters, and unexpected types, to understand exactly how minimist behaves in different scenarios.
  • Explicit Argument Handling & Type Checking: Do not rely on implicit parsing behavior. Explicitly check and convert argument types after minimist parsing. Validate the type and format of parsed arguments within your application code.
  • Input Validation (Post-Parsing): Always validate the parsed arguments against expected formats, types, and ranges. Do not assume minimist's parsing is sufficient for security. Treat minimist as a raw input processor, and implement your own robust validation.
  • Documentation Review: Carefully review minimist's documentation to fully understand its parsing rules and nuances. However, testing is more crucial than solely relying on documentation, as behavior can sometimes be subtle.